Renal – Anatomy

From outside to inside, the coverings of the kidney are arranged as follows:

1️⃣ Paranephric (pararenal) fat — outermost layer, between posterior abdominal wall and renal fascia.
2️⃣ Renal fascia (Gerota’s fascia) — encloses kidney and adrenal gland; anchors them in place.
3️⃣ Perinephric (perirenal) fat — surrounds kidney and adrenal gland within the fascia, acting as cushioning.
4️⃣ Renal capsule — tough fibrous covering tightly adherent to kidney surface.

Why others are wrong:
❌ Other options mix up the order — particularly confusing paranephric and perinephric layers.

Renal columns of Bertin are extensions of cortical tissue that project between the renal pyramids into the medulla. They contain interlobar blood vessels and help separate adjacent pyramids, providing structural support for the renal cortex and medulla.

Why others are wrong:
❌ Marks beginning of nephron — the nephron begins at the renal corpuscle, not in the renal columns.
❌ Medullary substance that extends into cortex — reversed; it’s the cortex extending into the medulla.
❌ Nephrons that are drained by a common collecting duct — describes the organization within a renal lobule, not the columns.
❌ Convoluted parts of renal tubules — these are located in the renal cortex, not in the renal columns.

When performing a renal biopsy, the needle is inserted posteriorly through the back muscles and soft tissues to reach the kidney.
From superficial (outside) to deep (inside), the layers encountered around the kidney are:

1️⃣ Paranephric (pararenal) fat — outermost layer surrounding the renal fascia.
2️⃣ Renal fascia (Gerota’s fascia) — fibrous covering enclosing the kidney and perinephric fat.
3️⃣ Perinephric (perirenal) fat — fatty cushion directly around the kidney.
4️⃣ Renal capsule — thin fibrous capsule adherent to the kidney surface.

Hence, the correct order pierced during posterior approach is:
👉 Paranephric fat → Renal fascia → Perinephric fat → Renal capsule

❌ Why Others Are Wrong:

• Perinephric fat first: ❌ It lies inside the fascia, not outermost.

• Capsule before fascia: ❌ The capsule is the innermost layer, reached last.

• Reversed or skipped layers: ❌ Anatomically incorrect sequence.

The ureter’s lymphatic drainage follows its three anatomical segments, each draining to nearby lymph node groups:

Thus, lymph from the middle part of the ureter drains primarily into the common iliac lymph nodes, which lie at the bifurcation of the aorta.

❌ Why Others Are Wrong:

• Para-aortic group:
  Drains the upper ureter and kidneys, not the middle portion.

• Celiac nodes:
  Drain upper abdominal organs (stomach, liver, spleen), not urinary structures.

• Hepatic nodes:
  Drain the liver and gallbladder, unrelated to ureter.

• Internal iliac nodes:
  Drain the lower ureter and bladder, not the middle segment.

Ureteric stones commonly get lodged at natural narrowings of the ureter.
There are three classical constriction sites where a calculus is most likely to get stuck:

1️⃣ Uretero-pelvic junction (UPJ) — where the renal pelvis narrows to form the ureter.
2️⃣ Pelvic brim (crossing of iliac vessels) — mid-ureteral narrowing.
3️⃣ Uretero-vesical junction (UVJ) — where the ureter enters the bladder wall.

The uretero-pelvic junction is the most common site of initial obstruction, producing loin-to-groin radiating pain along the ureter’s course.

❌ Why Others Are Wrong:

• Pelvic outlet:
  Refers to the bony pelvis exit — not a ureteric constriction site.

• Trigone of the bladder:
  Lies inside the bladder; stones may enter but are not typically lodged there.

• Renal medulla:
  Part of the kidney parenchyma — stones form in calyces, not get stuck here.

• Renal papilla:
  Where urine drains into minor calyces — possible site of origin, not impaction.

The renal fascia (Gerota’s fascia) is a fibrous sheath that encloses both the kidney and the suprarenal (adrenal) gland, along with the perirenal fat.
It helps anchor the kidney in place and provides a barrier that can limit the spread of infection.

Layered arrangement (from inside → outside):
1️⃣ Fibrous capsule – directly covers the kidney.
2️⃣ Perirenal fat – surrounds the capsule.
3️⃣ Renal fascia – encloses both kidney and adrenal gland.
4️⃣ Pararenal fat – lies outside the fascia.

❌ Why Others Are Wrong:

• Pararenal fat continues with fascia iliaca: ❌ No direct continuity; fascia iliaca is in the pelvis/thigh region.

• Perirenal fat continues with fascia transversalis: ❌ The renal fascia (not the fat) is related to fascia transversalis.

• Perirenal fat lies external to the renal fascia: ❌ It lies inside the renal fascia, around the kidney.

• Renal fascia directly covers the kidney: ❌ The fibrous capsule does — fascia is an outer layer enclosing the perirenal fat.

The renal arteries arise directly from the abdominal aorta at the level of L1–L2 vertebrae, just below (distal to) the origin of the superior mesenteric artery (SMA).
Each renal artery then divides into segmental branches to supply the kidneys.

❌ Why Others Are Wrong:

• Inferior mesenteric artery:
  Originates much lower (around L3) — below the renal arteries.

• Celiac trunk:
  Arises higher up (at T12) — above the SMA and renal arteries.

• Left gastric artery:
  A branch of the celiac trunk, not a direct branch of the aorta.

• Splenic artery:
  Also a branch of the celiac trunk, supplies the spleen — unrelated to renal origin.

The retropubic space (space of Retzius) lies anterior to the bladder, between the pubic symphysis and the bladder.

• Therefore, it cannot be considered a posterior relation.

• Posterior relations of the bladder differ slightly between males and females but generally include the rectum, rectovesical pouch (male), and uterus/vagina (female).

❌ Incorrect Answer Breakdown:

• Rectovesical pouch: Present posterior to the bladder in males (peritoneal reflection between bladder and rectum).

• Rectum: Lies posterior to the bladder (directly in males; in females, posterior to uterus and vagina which lie between bladder and rectum).

• Uterus: In females, the uterus lies superior/posterior to the bladder (separated by vesicouterine pouch).

• None of these: Wrong, because one option (retropubic space) is clearly not posterior.

Both the ureter and urinary bladder receive dual autonomic innervation:

• Parasympathetic (pelvic splanchnic nerves, S2–S4): stimulates contraction of the detrusor muscle and ureter peristalsis, and relaxes the internal urethral sphincter → promotes urination.

• Sympathetic (from T11–L2 via hypogastric plexus): relaxes the detrusor muscle and ureter, and contracts the internal urethral sphincter → promotes urine storage.
  This balance between sympathetic and parasympathetic input controls both storage and micturition.

❌ Incorrect Answer Breakdown:

• Preganglionic fibers: Too nonspecific; autonomic innervation involves both pre- and postganglionic fibers depending on the pathway.

• Parasympathetic only: Wrong, because sympathetic input is equally important for urine storage.

• Sympathetic only: Wrong, because parasympathetic activity is essential for micturition.

• None of these: Incorrect, since both autonomic divisions are definitely involved.

The pelvic splanchnic nerves (S2–S4) provide the parasympathetic innervation to the bladder.

• These nerves stimulate the detrusor muscle to contract.

• They also cause relaxation of the internal urethral sphincter, allowing urination (micturition).

• This regulation is considered the autonomous parasympathetic control of the bladder.

❌ Incorrect Answer Breakdown:

• Lumbar splanchnic nerve: Carries sympathetic fibers from L1–L2 that help in bladder relaxation and internal sphincter contraction, not parasympathetic activity.

• Cervical plexus: Innervates structures of the neck (phrenic nerve, etc.); has nothing to do with bladder control.

• None of these: Incorrect, since the correct nerve (pelvic splanchnic) is listed.

• Lumbar plexus: Supplies muscles and skin of the lower limb and parts of the abdominal wall; not responsible for parasympathetic regulation of the bladder.

The renal artery enters the kidney at the hilum, which is the medial concavity of the kidney. The hilum serves as the passage for major structures:

• Renal vein (most anterior)

• Renal artery (middle)

• Renal pelvis/ureter (most posterior)
  This arrangement is remembered by the acronym “VAU” (Vein, Artery, Ureter — from anterior to posterior).

❌ Incorrect Answer Breakdown:

• Glomerulus: A capillary tuft inside the nephron, supplied by afferent arterioles after the renal artery has branched many times. Not the entry site.

• Pyramid: Refers to the renal medullary pyramids. These are deep structures within the kidney, not points of vascular entry.

• Bladder: A separate organ where urine collects; not related to the entry of renal vessels.

• Capsule: The fibrous covering of the kidney. Vessels do not pierce it directly but enter through the hilum.

The pylorus is part of the stomach and lies more medially in the epigastric/right hypochondriac region. It does not come into direct relation with the anterior surface of the right kidney. Instead, it lies anterior to the pancreas and duodenum, not directly touching the kidney.

❌ Incorrect Answer Breakdown:

• Right colic flexure: ✅ Related — the hepatic flexure of the colon is in contact with the lower part of the anterior surface of the right kidney.

• Suprarenal gland: ✅ Related — the right suprarenal gland caps the upper pole of the right kidney anteriorly and medially.

• Duodenum: ✅ Related — specifically the descending part of the duodenum (2nd part) lies in front of the hilum of the right kidney.

• Liver: ✅ Related — the right lobe of the liver covers the upper part of the anterior surface of the right kidney.

The female urethra is about 4 cm in length (sometimes described as 3–5 cm). The statement saying it is “20 cm long” is incorrect, because that length applies to the male urethra (approximately 18–20 cm). The short length of the female urethra contributes to a higher risk of urinary tract infections (UTIs).

❌ Incorrect Answer Breakdown (Why the others are correct):

• The area continuous with the labia majora is lined with non-keratinized stratified squamous epithelium: ✅ True — the distal urethra near the external opening is lined with non-keratinized stratified squamous epithelium, continuous with the vulvar epithelium.

• The middle part is surrounded by the external striated muscle sphincter: ✅ True — the urethra passes through the urogenital diaphragm, where it is surrounded by the external urethral sphincter composed of striated muscle.

• It is initially lined with transitional epithelium: ✅ True — the proximal urethra, near the bladder neck, is lined with transitional (urothelium).

• It is approximately 5 cm long: ✅ True — often given as 4 cm, but some sources accept 3–5 cm. This is correct.

An arteriovenous (AV) fistula is a surgical connection between an artery and a vein, usually in the forearm (e.g., radial artery to cephalic vein). The arterial pressure strengthens and enlarges the vein, making it durable for repeated needle punctures. This high-flow access is essential for hemodialysis, and AV fistulas are the preferred long-term access because they last longer and have fewer complications compared to catheters or grafts.

❌ Incorrect Answer Breakdown:

• Arteriolymphatic fistula: Not a real clinical procedure; arteries are not surgically joined to lymphatic vessels.

• Capillary bed: A natural microscopic exchange network; cannot be surgically created for dialysis.

• Foramen ovale: A fetal cardiac opening between atria; unrelated to dialysis or vascular access.

• Portal vein: A natural venous vessel carrying blood from the gut to the liver; not surgically made and irrelevant to dialysis.

✅ Pylorus
The pylorus lies anterior to the left side of the midline (mainly in relation to the stomach and duodenum), not directly in front of the right kidney.

The anterior relations of the right kidney are:

• Superiorly: right suprarenal gland & liver.

• Medially: 2nd part of duodenum.

• Inferolaterally: right colic (hepatic) flexure of colon.
  Thus, the liver, duodenum (2nd part), and hepatic flexure are all in front of the right kidney. The pylorus, however, is more midline and associated with the stomach/duodenum transition, so it is not an anterior relation of the right kidney.

Explanation of the Incorrect Options

❌ 2nd part of duodenum
Yes, directly anterior to the medial border of the right kidney.

❌ Right colic flexure / Hepatic flexure
The right (hepatic) colic flexure lies anterior to the lower part of the right kidney.

❌ Liver
Covers the upper anterior part of the right kidney.

❌ Pylorus
Correct — it is not an anterior relation of the right kidney.

Step-by-Step Reasoning

1. Kidney position

• Kidneys are retroperitoneal organs, situated on the posterior abdominal wall.

• They extend approximately from T12 to L3 vertebral level.

• Right kidney is slightly lower than the left because of the liver.

2. Other vertebral levels

• T4–T12 → thoracic region; mostly thoracic organs (lungs, heart, esophagus). ❌

• L4–L5 → lower lumbar; location of iliac crest, far below kidneys. ❌

• L5–S3 → sacral region; far below kidney. ❌

• S3–S5 → tail end; not relevant. ❌

Correct Answer: T12–L3 ✅

Step-by-Step Reasoning

1. Kidney lymphatic drainage

• The kidneys are retroperitoneal and drain lymph primarily to the lateral aortic (para-aortic) lymph nodes along the abdominal aorta.

• From the para-aortic nodes, lymph eventually drains into cisterna chyli and the thoracic duct.

2. Check each option

• External iliac node → drains pelvic organs, not kidneys. ❌

• Common iliac node → drains lower limbs and pelvis, minor role if any. ❌

• Para-aortic node → ✅ main node for kidney lymphatic drainage.

• Celiac node → drains foregut organs (stomach, liver, pancreas, spleen). ❌

• None of these → incorrect.

Correct Answer: Para-aortic node ✅

✅ All of these
Hydronephrosis can occur if obstruction happens at any of the classical ureteric narrowing sites.

The ureter has three natural sites of narrowing where obstruction (often by stones) commonly occurs:

1. Pelviureteric junction (PUJ): where the renal pelvis narrows to form the ureter.

2. Pelvic brim: where the ureter crosses over the iliac vessels.

3. Ureterovesical junction (UVJ): where the ureter enters the bladder.

Obstruction at any of these points can lead to urine backup, causing hydronephrosis.

Explanation of the Incorrect Options

❌ Site of attachment with bladder / Ureterovesical junction
Correct site but not the only one; obstruction here is common but answer is broader.

❌ Pelviureteric junction
Yes, this is a major site, but not the only possible obstruction point.

❌ Pelvic brim
Also a classical narrowing, but again not the only site.

❌ All of these (if excluded)
If this option wasn’t present, then the individual sites could be correct, but since it is included, the comprehensive answer is “All of these.”

Step-by-Step Reasoning

1. Kidney support anatomy

• The kidneys are retroperitoneal, lying between T12–L3.

• They are surrounded by several layers that provide support and protection:

  1. Renal capsule → tough fibrous capsule directly around kidney.

  2. Perinephric (perirenal) fat → cushions and supports the kidney.

  3. Perinephric fascia (Gerota’s fascia / renal fascia) → encloses kidney and fat, anchoring it to surrounding structures.

• These layers prevent excessive movement and protect the kidney from trauma.

2. Check other options

• Median arcuate ligament → fibrous arch of diaphragm over aorta; unrelated to kidney support. ❌

• Peritoneal fluid → lubricates peritoneal cavity; kidney is retroperitoneal, not in peritoneal cavity. ❌

• Greater omentum / Lesser omentum → intraperitoneal structures; do not support retroperitoneal kidney. ❌

Correct Answer: Perinephric fascia ✅

Step-by-Step Reasoning

1. Detrusor muscle function

• Smooth muscle of the bladder wall.

• Responsible for bladder contraction during urination (micturition).

2. Autonomic innervation

• Parasympathetic (pelvic splanchnic nerves, S2–S4) → stimulatory: contracts detrusor, relaxes internal urethral sphincter.

• Sympathetic (hypogastric nerve, T11–L2) → inhibitory: relaxes detrusor, contracts internal urethral sphincter for urine storage.

• Somatic (pudendal nerve, S2–S4) → controls external urethral sphincter (voluntary).

3. Check each option

• Pelvic splanchnic nerve → supplies detrusor, stimulates contraction → ✅ correct.

• Hypogastric nerve → sympathetic, inhibits detrusor → ❌

• Pudendal nerve → somatic, controls external sphincter → ❌

• Lumbar plexus → no direct role in detrusor innervation → ❌

• None of these → incorrect

Correct Answer: Pelvic splanchnic nerve ✅

Clinical Correlation

• Damage to pelvic splanchnic nerves (e.g., pelvic surgery) → flaccid bladder, urinary retention.

• Hypogastric nerve injury → may affect storage reflex, but contraction still possible via parasympathetics.

Step-by-Step Reasoning

1. External urethral sphincter anatomy

• It is a skeletal muscle surrounding the urethra.

• Controls voluntary urination.

• Part of the urogenital diaphragm in both males and females.

2. Nerve supply

• Pudendal nerve (S2–S4) provides somatic motor innervation to the external urethral sphincter.

• This allows voluntary control of micturition.

3. Check other options

• Vesicular nerve → not a recognized anatomical term; possibly a distractor. ❌

• Obturator nerve → innervates medial thigh muscles (adductors). ❌

• Femoral nerve → innervates anterior thigh muscles. ❌

• Gonadal nerve → innervates gonads (testes/ovaries), sensory; not sphincter. ❌

Correct Answer: Pudendal nerve ✅

Clinical Correlation

• Injury to the pudendal nerve (e.g., pelvic trauma, childbirth) can cause loss of voluntary urinary control, leading to stress incontinence.

✅ Medullary collecting ducts
The nephron extends from Bowman’s capsule to the distal convoluted tubule. Collecting ducts are separate structures that drain multiple nephrons and are not technically part of the nephron itself.

The nephron is the structural and functional unit of the kidney. It consists of:

1. Renal corpuscle (glomerulus + Bowman’s capsule).

2. Proximal convoluted tubule.

3. Loop of Henle.

4. Distal convoluted tubule.

The collecting ducts are distinct — they receive urine from several nephrons and participate in final concentration under hormonal control (ADH, aldosterone). Thus, they are not strictly part of the nephron.

Explanation of the Incorrect Options

❌ Bowman’s capsule
Part of the renal corpuscle, essential to the nephron.

❌ Mesangial cells
Located within the glomerulus; provide structural support, phagocytosis, and regulate filtration. Considered part of the nephron’s functional unit.

❌ Loop of Henle
A clear segment of the nephron involved in countercurrent multiplication.

❌ Glomerulus
The capillary tuft of the renal corpuscle — the very start of the nephron.

Step-by-Step Reasoning

1. Loop of Henle segments:

   • Descending limb: highly permeable to water, but not to solutes.

   • Ascending limb (thin + thick):

     • Impermeable to water.

     • Thick ascending limb actively reabsorbs Na⁺, K⁺, Cl⁻ via the Na⁺-K⁺-2Cl⁻ cotransporter.

     • Known as the diluting segment because it removes solutes but leaves water behind.

2. Check each option:

• Permeability to water is affected by ADH → false. ADH mainly acts on the collecting ducts, not the ascending limb.

• Impermeable to potassium → false. Potassium is reabsorbed here via NKCC2 cotransporter.

• Impermeable to sodium → false. It actively reabsorbs sodium.

• Impermeable to water → ✅ true property of ascending limb.

• Permeable to water → false, this describes the descending limb.

Correct Answer: Impermeable to water ✅

Step-by-Step Reasoning

1. Cortex vs. Medulla – Nephron distribution

   • Cortex:

     • Glomeruli (Bowman’s capsule + glomerulus)

     • Proximal convoluted tubule (PCT)

     • Distal convoluted tubule (DCT)

     • Cortical collecting ducts

   • Medulla:

     • Loop of Henle (thin descending + thin ascending + thick ascending limb)

     • Medullary collecting ducts

2. Check each option

   • Proximal convoluted tubule → lies in the cortex → ✅ correct.

   • Medullary collecting duct → found in the medulla, not cortex.

   • Thin descending limb → part of loop of Henle, in the medulla.

   • Thin ascending limb → also in the medulla.

   • None of these → wrong, because PCT is clearly in the cortex.

Correct Answer: Proximal convoluted tubule ✅

Step-by-Step Reasoning

1. Ureteric blood supply overview

   • The ureter is supplied segmentally, from top to bottom:

     • Upper part → renal artery, gonadal artery, adrenal arteries.

     • Middle part → aorta, common iliac artery, gonadal artery.

     • Lower part → superior vesical artery, inferior vesical artery (in males), uterine artery/vaginal artery (in females).

2. Check each option

   • Renal artery → yes, supplies the upper part of the ureter.

   • Gonadal artery (testicular/ovarian) → yes, supplies the ureter along its course.

   • Common iliac artery → yes, provides branches to the mid-ureter.

   • Superior vesical artery → yes, supplies the lower ureter.

   • Inferior mesenteric artery → ❌ this artery supplies the large intestine (distal transverse colon, descending colon, sigmoid, rectum), but not the ureter.

Correct Answer: Inferior mesenteric artery ✅

✅ Kidney
The parallelogram of Morris is a surface anatomical landmark used to outline the position of the kidney on the posterior abdominal wall.

The parallelogram of Morris is a four-sided area drawn on the back to project the position of the kidney.

• The upper boundary is the 11th rib.

• The lower boundary is the iliac crest.

• The lateral boundary is the vertical line from the midpoint of the iliac crest (midaxillary line).

• The medial boundary is the line 2.5 cm from the midline.

Within this parallelogram lies the surface marking of the kidney, useful in clinical examination, surgery, and radiology for locating the renal angle and understanding relations.

Explanation of the Incorrect Options

❌ Bladder
Surface anatomy of the bladder is determined in the suprapubic region, not by Morris’ parallelogram.

❌ Stomach
The stomach’s surface anatomy is related to the left hypochondrium and epigastrium; it is not outlined using the parallelogram of Morris.

❌ Spleen
The spleen lies under the left 9th–11th ribs, along the long axis of the 10th rib — no parallelogram method is used.

❌ Liver
Liver surface anatomy uses percussion lines (midclavicular, midsternal), not Morris’ parallelogram.

✅ The right renal vein is longer than the left
In fact, the left renal vein is longer than the right, as it must cross in front of the aorta to reach the IVC.

The arrangement of structures at the kidney hilum is clinically important. From anterior to posterior, the order is: renal vein → renal artery → renal pelvis (ureter origin). The renal artery divides into several segmental branches, the renal vein drains directly into the IVC, and while some variation can occur in accessory vessels, the general pattern holds true.

The left renal vein is distinctly longer than the right because it crosses the midline, passing anterior to the aorta and posterior to the superior mesenteric artery before draining into the IVC. The right renal vein, in contrast, drains directly into the IVC and is shorter.

Explanation of the Incorrect Options

❌ The renal artery divides into 3–5 segmental arteries at the hilum
This is true — these segmental arteries are end arteries, supplying distinct renal segments without significant collateral circulation.

❌ The renal pelvis is normally the most posterior of the three
Correct — the pelvis lies behind the artery and vein, forming the beginning of the ureter.

❌ The renal veins empty directly into the inferior vena cava
Correct — both renal veins ultimately drain straight into the IVC.

❌ The anatomy of the contents of the hilum can be variable
Correct — accessory renal arteries or variable arrangements of the hilum are well documented.

❌ The right renal vein is longer than the left
This is false — the left renal vein is the longer one.

The lymphatic drainage of the kidneys follows the renal veins and drains primarily into the para-aortic (lumbar) lymph nodes, which are located along the abdominal aorta near the origin of the renal arteries. This makes sense because the kidneys are retroperitoneal organs lying adjacent to the aorta. These nodes eventually drain into the cisterna chyli and then the thoracic duct.

Explanation of the Incorrect Options

❌ Pre-aortic nodes
These nodes lie in front of the aorta and are mainly responsible for drainage of the gastrointestinal tract (celiac, superior mesenteric, inferior mesenteric nodes), not the kidneys.

✅ Para-aortic nodes
Correct — the main lymphatic drainage site of the kidneys.

❌ Inguinal nodes
These drain the superficial perineum, lower limb, and abdominal wall below the umbilicus, but not deep retroperitoneal structures like the kidney.

❌ Thoracic nodes
There are mediastinal and thoracic lymph nodes, but the kidneys drain into abdominal para-aortic nodes before lymph flows into the thoracic duct.

❌ Celiac nodes
These are pre-aortic nodes that drain foregut structures (stomach, liver, pancreas, spleen, etc.), not the kidneys.

After blood passes through the glomerular capillaries, it exits via the efferent arteriole. From here:

• In cortical nephrons → the efferent arterioles drain into the peritubular capillaries, which surround the proximal and distal convoluted tubules. These vessels play a crucial role in reabsorption and secretion.

• In juxtamedullary nephrons → the efferent arterioles form the vasa recta, which descend into the medulla and maintain the countercurrent exchange system.

Thus, the general answer is peritubular capillaries, with vasa recta being a special subset for juxtamedullary nephrons.

Explanation of the Incorrect Options

❌ Inferior mesenteric vein
This drains blood from the large intestine, not from the kidney.

✅ Peritubular capillaries
Correct — main drainage of efferent arterioles (especially in cortical nephrons).

❌ Afferent arteriole
This brings blood into the glomerulus, not out of it.

❌ Capillary tuft
This is the glomerulus itself — where the efferent arteriole originates, not where it drains.

❌ Vasa recta
Partially correct for juxtamedullary nephrons, but the broader correct answer is peritubular capillaries, since they are universal for cortical nephrons.

The kidney is supported and held in position within the posterior abdominal wall mainly by:

• Perinephric (Gerota’s) fascia, which encloses the kidney and the perirenal fat.

• This fascia, along with surrounding fat (perinephric fat and paranephric fat), acts as a cushion and anchor, preventing excessive movement of the kidney.

• The renal vessels and pressure from surrounding abdominal structures also contribute, but the main supportive structure is the perinephric fascia.

Explanation of the Incorrect Options

❌ Median arcuate ligament
This is part of the diaphragm arching over the aorta; it does not support the kidney.

✅ Perinephric fascia
Correct — it surrounds and anchors the kidney with its fat capsule.

❌ Peritoneal fluid
This lubricates abdominal viscera within the peritoneal cavity. The kidneys are retroperitoneal and are not supported by peritoneal fluid.

❌ Greater omentum
A fold of peritoneum hanging from the stomach and transverse colon; it provides protection to abdominal viscera but has no role in supporting the kidneys.

❌ Lesser omentum
A peritoneal fold between the stomach/duodenum and liver; also unrelated to kidney support.

✅ Gonadal artery

• The middle part of the ureter is supplied by the gonadal artery (testicular artery in males, ovarian artery in females).

• The blood supply to the ureter is segmental:

  • Upper part → renal artery

  • Middle part → gonadal artery

  • Lower part → branches from common iliac, internal iliac, and vesical arteries

Why the Other Options Are Incorrect

❌ Renal artery

• Supplies the upper part of the ureter, not the middle.

❌ Supra renal artery

• Supplies the suprarenal (adrenal) gland, not the ureter.

❌ Cystic artery

• Supplies the gallbladder, not related to the ureter.

❌ Common iliac artery

• Contributes to the lower part of the ureter’s blood supply, not the middle.

✅ Left renal vein is anterior to aorta

• The left renal vein runs from the left kidney, passes anterior to the aorta but posterior to the superior mesenteric artery (SMA), before draining into the IVC.

• This anatomical relationship creates the potential for “nutcracker syndrome”, where the vein is compressed between the SMA and aorta.

Why the Other Options Are Incorrect

❌ Left renal vein is shorter than the right vein

• The left renal vein is longer, because it has to cross the midline anterior to the aorta to reach the IVC.

• The right renal vein is much shorter since the IVC is located on the right side.

❌ Superior mesenteric artery is posterior to left renal vein

• The opposite is true: the SMA lies anterior to the left renal vein, creating the “nutcracker” compression point.

❌ Renal artery is anterior to renal vein

• In the renal hilum (anterior → posterior), the arrangement is: renal vein → renal artery → renal pelvis.

• So, the renal vein is anterior to the renal artery, not the other way around.

❌ Left testicular vein drains directly into IVC

• The right testicular vein drains directly into the IVC.

• The left testicular (gonadal) vein drains into the left renal vein, which then empties into the IVC.

✅ Kidney laceration

• The 12th rib lies posteriorly and protects the upper part of the kidney, especially on the left side.

• A fracture of the lower ribs (11th and 12th, known as “floating ribs”) often transmits force to the underlying kidney.

• Clinical signs may include hematuria, flank pain, and tenderness.

Why the Other Options Are Incorrect

❌ Colon perforation

• The descending colon is retroperitoneal but not directly under the 12th rib.

• Injury to the colon is more likely from penetrating trauma to the abdomen, not a posterior rib fracture.

❌ Liver hematoma

• The liver is located on the right side under ribs 7–11.

• A left-sided 12th rib fracture would not involve the liver.

❌ Pancreatic laceration

• The pancreas is retroperitoneal and sits across the upper abdomen (around L1 level).

• It is not directly adjacent to the 12th rib, so a rib fracture here is unlikely to damage it.

❌ Pneumothorax

• Pneumothorax is typically associated with upper rib fractures and pleural injury.

• The 12th rib is too low and posterior to injure the lung apex or pleura significantly.

✅ Pubic symphysis

• Located directly anterior to the urinary bladder in males.

• A cartilaginous joint between the two pubic bones.

• Clinically relevant in suprapubic catheterization, where the bladder is accessed just above this joint.

Why the Other Options Are Incorrect

❌ Rectum

• Lies posterior to the bladder.

• Separated from it by the rectovesical pouch.

❌ Prostate gland

• Sits inferior to the bladder.

• Surrounds the prostatic urethra, not anterior to the bladder.

❌ Seminal vesicles

• Located posterior-superior to the bladder.

• Positioned at the bladder’s base, not in front of it.

❌ Urethra

• Emerges inferiorly from the bladder.

• A tubular passage, not an anterior structure.

Explanation:

• The hilum of the kidney is the entry/exit point for the renal artery, vein, and ureter.

• Left kidney:

  • Usually lies slightly higher than the right kidney because of the liver on the right side.

  • Hilum level:

    • Transpyloric plane (approx. L1 vertebral level)

    • About 5 cm lateral to the midline

• Clinical relevance:

  • Knowledge of hilum location is important for surgical approaches, imaging, and catheterization.

Why the Other Options Are Incorrect:

• Junction of midclavicular line and transtubercular plane: Too low; transtubercular plane ~L5

• Subcostal plane: Around L3; hilum is higher

• Transtubercular plane, 5 cm from median plane: Too low

• Interspinous plane: Around S1; far below kidney

The renal medulla contains pyramids, which are triangular structures of tubules and collecting ducts.

• Renal columns (of Bertin):

  • Extensions of cortical tissue that project between the renal pyramids.

  • Provide structural support and contain blood vessels supplying the cortex and medulla.

Other structures:

• Renal pyramids: Medullary tissue containing loops of Henle and collecting ducts.

• Medullary rays: Straight tubules extending from the cortex into the medulla, not cortical extensions.

• Major calices / Minor calices: Collect urine from the pyramids; part of the collecting system.

The parallelogram of Morris is a surface landmark used to approximate the position of the kidneys on the posterior abdominal wall. Its borders are:

• Vertical lines:

  • 9.5 cm from the midline (spinal column)

  • 2.5 cm from the midline

• Horizontal lines:

  • Superior: Tips of the spinous processes of T11

  • Inferior: Spinous process of L3

The kidney lies roughly between T12 and L3 vertebral levels, so L1 is not used as a horizontal border of the parallelogram.

Why the Other Options Are Correct:

• Vertical line 9.5 cm from midline – Part of the parallelogram.

• Horizontal border at T11 tips – Superior boundary.

• Vertical line 2.5 cm from midline – Medial boundary.

• Horizontal border at L3 spinous process – Inferior boundary.

Kidney stones (renal calculi) can form or get lodged in areas where urine collects or flows, such as the renal pelvis, calyces, ureter, or bladder. These are parts of the urinary tract that deal with the passage or storage of urine, making them common sites for stone obstruction.

The nephron, however, is the microscopic functional unit of the kidney that filters blood and forms urine. It is too small for stone formation or retention — stones are far larger than the microscopic tubules of the nephron.

Why the other options are incorrect:

• Ureter: Narrow tubes — stones often get stuck here.

• Bladder: Stones can form or accumulate here, especially in urinary retention.

• Calyces: Stones often form in the minor or major calyces where urine first collects.

• Pelvis: Common site for stone lodging before entering the ureter.

The ureters are muscular tubes that connect each kidney to the urinary bladder.

• They originate from the renal pelvis at the hilum of the kidney.

• They descend retroperitoneally along the posterior abdominal wall.

• They finally enter the bladder at the posterolateral angles, allowing urine to flow from the kidney to the bladder for storage before excretion.

Why the other options are incorrect:

• Transversalis fascia: This is a fascial layer of the abdominal wall, not involved in urinary drainage.

• Lumbar nodes: These are lymph nodes, not a physical connection between kidney and bladder.

• Perinephric fat: This surrounds and protects the kidney but doesn’t connect it to the bladder.

• Aorta: The main artery of the body; supplies blood but is unrelated to urine transport.

The nephron is the basic structural and functional unit of the kidney, responsible for filtering blood, reabsorbing essential substances, and excreting waste products in urine. Each kidney contains about 1 to 1.5 million nephrons, consisting of the renal corpuscle (Bowman’s capsule and glomerulus) and the renal tubule.

Why other options are incorrect:

• Minor calices: These are part of the collecting system that collects urine from papillary ducts, not functional filtration units.

• Renal corpuscles: These are part of nephrons but are not the entire functional unit.

• Medullary rays: These are bundles of straight tubules and collecting ducts within the cortex, not complete functional units.

• Renal pyramids: These are anatomical structures in the medulla, containing loops of Henle and collecting ducts, but they are not individual functional units.

The ureters are muscular tubes (~25–30 cm long) that transport urine from the renal pelvis to the urinary bladder.

Key features:

• Retroperitoneal: They lie behind the peritoneum throughout their course.

• Originate at the renal pelvis: At the hilum of the kidney (posteriorly, not anteriorly).

• Constriction sites (three):

  1. Ureteropelvic junction – where the renal pelvis becomes the ureter.

  2. Pelvic brim – where ureter crosses over the iliac vessels.

  3. Vesicoureteral junction – where ureter enters the bladder.

Why the Other Options Are Incorrect

• “Arise from anterior side…” – Incorrect; they arise posteriorly at the hilum, not anteriorly.

• “Ureters are intraperitoneal” – Incorrect; they are retroperitoneal.

• “They are constricted at two regions” – Incorrect; there are three constriction sites, not two.

• “None of these” – Incorrect, because the statement about being retroperitoneal is true.

The kidney coverings (from inside to outside) are arranged in layers:

1. Fibrous capsule –

   • The innermost covering.

   • A thin, tough, fibrous membrane that directly adheres to the kidney surface, providing protection and structural integrity.

2. Perinephric fat (perirenal fat) –

   • Surrounds the fibrous capsule and acts as a cushion.

3. Renal fascia (Gerota’s fascia) –

   • Encloses the perinephric fat and kidney, anchoring them in place.

4. Paranephric fat (pararenal fat) –

   • Outermost fat layer, providing additional support and insulation.

Why the Other Options Are Incorrect

• Paranephric fat – Outermost fat, not innermost.

• Renal fascia – Lies outside perinephric fat, not the first layer.

• Perinephric fat – Surrounds but doesn’t directly touch the kidney.

• None of these – Incorrect, as fibrous capsule is the true innermost covering.

The posterior relations of the kidney include muscles, nerves, and fascia that are located behind the kidney in the retroperitoneal space.

Posterior structures of the kidney:

• Muscles:

  • Psoas major

  • Quadratus lumborum

  • Transversus abdominis

• Nerves:

  • Subcostal nerve

  • Iliohypogastric nerve

  • Ilioinguinal nerve

The quadratus femoris muscle, however, is a deep gluteal muscle located in the hip region, not in the posterior abdominal wall where the kidneys are located.

Why the Other Options Are Incorrect

• Transversus abdominis – Lies posterior-laterally to the kidney.

• Ilioinguinal nerve – Runs posterior to the kidney along with iliohypogastric nerve.

• Iliohypogastric nerve – Posterior to the kidney in the retroperitoneal space.

• Psoas major – Lies medially and posteriorly to the kidney.

The ureter is a retroperitoneal muscular tube that carries urine from the kidneys to the bladder.

• It lies anterior to the transverse processes of the lumbar vertebrae as it descends vertically along the posterior abdominal wall.

• This relationship is often noted during surgeries like ureteric stent placements or retroperitoneal procedures.

Why the Other Options Are Incorrect

• Esophagus – Located in the posterior mediastinum (thorax), not related to lumbar transverse processes.

• Rectum – Lies in the pelvis, anterior to the sacrum, not along the lumbar vertebral transverse processes.

• Aorta – Runs anterior to the vertebral bodies, not anterior to the transverse processes.

• Bladder – Located in the pelvis, far from the lumbar transverse processes.

The tip of each renal pyramid is called the renal papilla.

• Urine formed in the nephrons drains through the collecting ducts located in the medulla.

• From the papilla, urine flows into the minor calyx, then into a major calyx, then the renal pelvis, and finally into the ureter for excretion.

Why the Other Options Are Incorrect

• Capsule – The fibrous capsule surrounds the kidney but is not part of the drainage pathway.

• Ureter – Receives urine after it passes through calyces and the renal pelvis; not the direct opening point of the pyramid tips.

• Medulla – This is the region where the pyramids are located, but the openings are at the calyces, not in the medulla tissue itself.

• Cortex – The outer region of the kidney, containing glomeruli and parts of the nephron, but not the drainage point.

The mucosa of the urinary bladder is lined by urothelium, also known as transitional epithelium.

• It is a specialized stratified epithelium that allows the bladder to stretch as it fills with urine and recoil when it empties.

• The superficial layer contains umbrella cells that protect underlying tissues from urine toxicity.

Why the Other Options Are Incorrect

• Adventitia – This is a connective tissue layer found externally around parts of the bladder (except the superior surface). It is not the mucosal lining.

• Serosa – Found only on the superior surface of the bladder, derived from the peritoneum; not the lining of the mucosa.

• Endothelium – Lines blood vessels, not the bladder.

• Renal fascia – Connective tissue around the kidney, unrelated to bladder mucosa.

• Renal capsule: Thin fibrous covering directly on the kidney surface.

• Perinephric (perirenal) fat: Immediately outside the capsule, cushioning the kidney.

• Renal fascia: Condensation of connective tissue enclosing kidney + adrenal gland + perinephric fat.

• Paranephric (pararenal) fat: Outermost, behind the kidney, between renal fascia and posterior abdominal wall.

Answer breakdown:

• Capsule → perinephric fat → renal fascia → paranephric fat → ✅ Correct

• Paranephric first → ❌ it’s the outermost, not innermost

• Capsule → paranephric fat → ❌ wrong sequence

• Capsule last → ❌ capsule is innermost

• Paranephric before perinephric → ❌ inverted

The coverings of the kidney from innermost to outermost are:

1. Fibrous capsule – thin layer tightly adherent to kidney.

2. Perinephric (perirenal) fat – surrounds kidney and adrenal gland.

3. Renal fascia (Gerota’s fascia) – fibrous connective tissue enclosing kidney + fat.

4. Paranephric fat – outermost, posterior to the renal fascia.

• Cortex & medulla are internal structures of the kidney, not coverings.

• Pelvis is the funnel-shaped structure inside, collecting urine.

• Perinephric fat is not the outermost, it lies inside the renal fascia.

• The renal fascia is the true outermost layer enclosing the kidney and perinephric fat.

Answer breakdown:

• Renal fascia → Correct (outermost covering of kidney itself)

• Pelvis → inside, collects urine

• Cortex → internal tissue

• Medulla → deeper internal tissue

• Perinephric fat → surrounded by fascia, not outermost

• The hilum of the kidney lies at the level of L1 vertebra in the transpyloric plane, which passes through:

  • Pylorus of the stomach

  • Fundus of gallbladder

  • Neck of pancreas

  • Origins of the superior mesenteric artery and portal vein

  • Hilum of kidneys

Other options:

• Median plane – Incorrect: Vertical midline plane, not used for kidney hilum location.

• Supine plane – Incorrect: Not an anatomical reference plane.

• Subcostal plane – Incorrect: At L2 level, below the transpyloric plane.

• Transtubercular plane – Incorrect: At L5 level, much lower than the kidneys.

Answer breakdown:

• Transpyloric plane – Correct (L1, passes through renal hilum).

• Others – Incorrect anatomical levels.

The ureter receives blood supply segmentally from nearby arteries as it descends:

• Abdominal ureter: renal artery, gonadal artery, aorta, common iliac artery.

• Pelvic ureter: branches from internal iliac artery, especially superior vesical artery, inferior vesical artery (in males), uterine/vaginal arteries (in females).

• Occasionally, umbilical artery remnants (via superior vesical) also supply.

The inferior mesenteric artery supplies the hindgut (distal colon & rectum), but does not contribute to ureteric supply.

Answer breakdown:

• Inferior mesenteric artery → ✗ does not supply ureter

• Umbilical artery → ✓ via superior vesical branch, supplies pelvic ureter

• Superior vesical artery → ✓ supplies upper pelvic ureter

• Inferior vesical artery → ✓ supplies lower ureter in males

• Internal iliac artery → ✓ main pelvic source

The anterior relations of the left kidney are important in anatomy because they help understand surgical approaches and potential sites of injury. Let’s analyze the structures:

• Head of pancreas → Lies anterior to the right kidney, not the left.

• Spleen → Lies anterior and lateral to the upper pole of the left kidney.

• Suprarenal (adrenal) gland → Sits on the superior pole of the kidney; part of the anterior and superior relations.

• Looped jejunum → Found anterior to the lower part of the left kidney.

• Splenic flexure of colon → Lies anterior to the upper pole of the left kidney.

So, the head of the pancreas is specific to the right kidney and is not found anterior to the left kidney.

✅ Correct Answer: Head of pancreas

❌ Why the other options are incorrect

• Spleen → Correct anterior relation of left kidney.

• Suprarenal gland → Superior anterior relation of left kidney.

• Looped jejunum → Found anterior to the left kidney.

• Splenic flexure → Found anterior to upper pole of left kidney.

The kidney is surrounded by multiple layers, each with distinct roles:

1. Fibrous (renal) capsule → Thin, tough layer directly covering the kidney surface. Protects against trauma and infection.

2. Perinephric (perirenal) fat → Surrounds the fibrous capsule, cushioning the kidney.

3. Renal fascia (Gerota’s fascia) → Fibrous connective tissue that encloses the kidney and perinephric fat, anchoring it to surrounding structures.

4. Paranephric (pararenal) fat → Lies outside the renal fascia; additional padding.

5. Peritoneum → Covers anterior surfaces in some areas but is not a true structural layer of the kidney.

Key point: The outermost layer directly forming the boundary with surrounding tissue is the renal fascia. It wraps both the kidney and perinephric fat, holding the organ in place.

✅ Correct Answer: Renal fascia

❌ Why the other options are incorrect

• Fibrous capsule → Innermost protective layer around the kidney surface, not outermost.

• Only fat → Fat is external to the fibrous capsule but lies inside the fascia or outside as paranephric fat.

• Perinephric fat → Between fibrous capsule and renal fascia; not the outermost.

• Peritoneum → Covers only parts of the anterior kidney; not an actual structural layer.

The renal sinus is a central cavity within the kidney that serves as a space for vessels, nerves, fat, and the collecting system. Its key components include:

• Renal pelvis → The funnel-shaped structure that collects urine from the calyces and directs it into the ureter.

• Renal blood vessels → Branches of the renal artery and vein.

• Fat and connective tissue → Cushions and supports the vessels and pelvis.

Structures not present in the renal sinus:

• Bowman’s capsule and glomerulus → Part of the nephron, located in the renal cortex.

• Renal cortex → The outer functional layer of the kidney.

• Medulla → The inner pyramidal region surrounding the sinus, but not inside it.

Thus, the renal pelvis is the structure located within the renal sinus.

✅ Correct Answer: Renal pelvis

❌ Why the other options are incorrect

• Bowman’s capsule → Found in the renal cortex; part of the nephron.

• Glomerulus → Located in renal cortex, not in the sinus.

• Renal cortex → The outer kidney tissue, surrounds the sinus.

• Medulla → Surrounds the sinus; forms pyramids, not part of the sinus cavity.

The ureter has three main parts: upper (superior), middle, and lower (inferior). Lymphatic drainage follows the course of the ureter and is region-specific:

• Superior (upper) ureter → Lies near the renal pelvis and kidney.

  • Lymph drains primarily into the lateral aortic (para-aortic) lymph nodes.

• Middle ureter → Around the level of the common iliac vessels.

  • Drains into common iliac lymph nodes.

• Inferior (lower) ureter → Near the bladder.

  • Drains into external iliac, internal iliac, and vesical lymph nodes.

Key point: The drainage closely follows the arterial supply; the superior ureter is supplied by branches of the renal artery, which explains why its lymphatics go to the lateral aortic nodes.

✅ Correct Answer: Lateral aortic nodes

❌ Why the other options are incorrect:

• Internal iliac nodes → Drain the lower ureter and bladder, not the upper ureter.

• Common iliac nodes → Drain the middle ureter, not the superior part.

• Vesical nodes → Drain the bladder, not the upper ureter.

• External iliac nodes → Drain the lower ureter, near the bladder.

The kidney’s vascular system is unique in that it has two capillary beds in series: the glomerular capillaries and the peritubular capillaries (or vasa recta in the medulla). To connect these two, a specialized vessel is required.

• Afferent arterioles
  These are the small arteries that deliver blood into the glomerulus. They regulate how much blood enters the glomerular capillaries but do not connect the glomerulus to the peritubular network. Their role ends at the glomerular tuft.

• Vasa recta
  These are straight capillaries that run deep into the medulla alongside the loop of Henle. However, they arise specifically from the efferent arterioles of juxtamedullary nephrons, not directly from the glomerulus of all nephrons. Thus, they are a downstream branch, not the immediate connector.

• Peritubular capillaries
  These form a network around the proximal and distal convoluted tubules, where exchange of water and solutes occurs. But they themselves are not the vessel that links the glomerular capillaries to the tubular circulation—they are the destination.

• Arcuate arteries
  These are large vessels running along the corticomedullary junction. They are part of the arterial supply pathway (between interlobar and interlobular arteries) and are much farther upstream, with no direct role in linking the glomerulus to the peritubular capillaries.

• Efferent arterioles
  These carry blood out of the glomerular capillaries. From here, the blood is directed either into the peritubular capillaries (in cortical nephrons) or into the vasa recta (in juxtamedullary nephrons). This makes the efferent arteriole the key connecting vessel between the two capillary systems.

✅ Correct Answer: Efferent arterioles

✅ Correct Answer: Loop of Henle

Explanation:

Step 1: Kidney structure overview

• The kidney has two main regions: cortex and medulla.

  • Cortex: contains renal corpuscles (glomeruli + Bowman’s capsule) and proximal/distal convoluted tubules.

  • Medulla: contains loops of Henle, collecting ducts, and blood vessels.

Step 2: Loop of Henle

• The loop of Henle dips from the cortex into the medulla and is responsible for:

  • Creating the medullary osmotic gradient

  • Facilitating concentration of urine via countercurrent mechanism

Step 3: Clinical relevance

• The thick ascending limb of the loop is impermeable to water, a key factor in urine concentration.

❌ Why the other options are incorrect:

Bowman’s capsule

• ❌ Found in the cortex, surrounding glomeruli.

Proximal convoluted tubule

• ❌ Located entirely in the cortex, not in the medulla.

Distal convoluted tubule

• ❌ Also located in the cortex, before entering the collecting duct.

Glomerulus

• ❌ Present only in the cortex, as part of the renal corpuscle.

✅ Correct Answer: Cortical substance that extends into medulla

Explanation:

Step 1: Anatomy of the kidney

• The kidney has cortex and medulla:

  • Cortex: outer part, contains renal corpuscles and convoluted tubules

  • Medulla: inner part, contains renal pyramids

Step 2: Renal columns of Bertin

• Renal columns are extensions of cortical tissue that project between the renal pyramids into the medulla.

• They contain blood vessels and fibrous tissue and separate the pyramids.

• Functionally, they provide a pathway for vessels and support the renal pyramids.

Step 3: Clinical relevance

• Enlargement of the renal columns may be confused with renal masses on imaging.

❌ Why the other options are incorrect:

Medullary substance that extends into cortex

• ❌ The columns are cortical, not medullary tissue.

Nephrons that are drained by a common collecting duct

• ❌ Refers to renal pyramids, not the columns.

Marks beginning of nephron

• ❌ Nephron begins in the renal corpuscle, located in cortex.

Convoluted parts of renal tubules

• ❌ Tubules are part of nephrons, not a description of renal columns.

✅ Correct Answer: A structural and functional unit of kidney

Explanation:

Step 1: Definition of nephron

• The nephron is the basic structural and functional unit of the kidney.

• It is responsible for:

  • Filtration of blood at the glomerulus

  • Reabsorption of essential substances (water, glucose, electrolytes)

  • Secretion of waste products and hydrogen ions

  • Excretion of urine

Step 2: Components of the nephron

• Renal corpuscle: glomerulus + Bowman’s capsule (filtration)

• Renal tubule: proximal tubule, loop of Henle, distal tubule, collecting duct (reabsorption and secretion)

Step 3: Clinical relevance

• Damage to nephrons, as in glomerulonephritis or chronic kidney disease, reduces renal function.

❌ Why the other options are incorrect:

Glucose transporter

• ❌ This is a protein involved in glucose reabsorption, not the nephron itself.

Storage site of lipids

• ❌ Nephrons do not store lipids; they are for filtration and urine formation.

Site of ADH production

• ❌ ADH is produced by the hypothalamus (supraoptic and paraventricular nuclei), not the nephron.

Cholesterol synthesizing body

• ❌ Nephrons are not involved in cholesterol synthesis.

✅ Correct Answer: Interlobular artery

Explanation:

Step 1: Renal arterial hierarchy

• Renal artery → Segmental arteries → Interlobar arteries → Arcuate arteries → Interlobular arteries → Afferent arterioles → Glomerular capillaries

Step 2: Functional significance

• The afferent arteriole brings blood into the glomerulus for filtration.

• Its origin from the interlobular artery allows precise control of glomerular blood flow and filtration rate via afferent arteriolar tone.

❌ Why the other options are incorrect:

Intralobar artery

• ❌ Intermediate vessel within lobes; afferent arterioles do not arise directly from it.

Interlobar artery

• ❌ Travels between renal pyramids; gives rise to arcuate arteries, not directly to afferent arterioles.

Peritubular capillaries

• ❌ Formed after glomerular filtration, not a source of afferent arterioles.

Arcuate artery

• ❌ Gives off interlobular arteries, which then form afferent arterioles.

✅ Correct Answer: Internal iliac artery

Explanation:

Step 1: Ureteral arterial supply

• The ureter is divided into abdominal, pelvic, and intramural parts, each supplied by different arteries:

  • Abdominal ureter: renal artery, gonadal artery, aorta, common iliac artery branches

  • Pelvic ureter: primarily branches from the internal iliac artery, such as the inferior vesical artery, middle rectal artery, and uterine artery (in females)

  • Intramural ureter: branches from vesical arteries

Step 2: Clinical relevance

• Knowledge of ureteral blood supply is important during pelvic surgery or ureteral reconstruction to prevent ischemia.

❌ Why the other options are incorrect:

Gonadal artery

• ❌ Supplies abdominal ureter, not the pelvic portion.

Inferior vesical artery

• ❌ Although it is a branch of the internal iliac, the main arterial source to the pelvic ureter is considered the internal iliac artery as the parent vessel.

Abdominal aorta

• ❌ Supplies proximal abdominal ureter.

Renal artery

• ❌ Supplies upper ureter, not pelvic ureter.

✅ Correct Answer: Spleen

Explanation:

Step 1: Anterior relations of the right kidney

• Right kidney anterior relations:

  • Liver – superior and anterior.

  • Descending (2nd) part of duodenum – medial-anterior.

  • Right colic flexure – inferior-anterior.

  • Suprarenal (adrenal) gland – superior pole (partially anterior).

• Spleen is on the left side, related to the anterior surface of the left kidney, not the right.

Step 2: Clinical relevance

• Important in surgical approaches, imaging interpretation, and understanding perirenal organ relationships.

❌ Why the other options are incorrect:

Right colic flexure

• ❌ Lies anterior and inferior to the right kidney.

Descending part of duodenum

• ❌ Lies medial and anterior to the right kidney.

Liver

• ❌ Major anterior relation of right kidney.

Suprarenal gland

• ❌ Sits on the superior pole; partially anterior.

The stretch signals responsible for initiating bladder emptying arise mainly from stretch receptors in the detrusor muscle of the body of the urinary bladder.

• As urine accumulates, the body of the bladder distends

• Stretch receptors here send afferent signals via pelvic nerves (S2–S4)

• These signals activate the micturition reflex

• This leads to detrusor contraction and coordinated relaxation of sphincters

Thus, the body of the bladder is the primary sensory region for bladder filling.

❌ Incorrect Options Explained

❌ Ureter

• Transports urine from kidney to bladder

• Contains stretch receptors for peristalsis, not micturition

❌ Fundus of urinary bladder

• Fundus (base) is relatively fixed

• Less involved in stretch detection compared to the bladder body

❌ Anterior urethra

• Not involved in sensing bladder filling

• Plays no role in initiating micturition reflex

❌ Posterior urethra

• Contains receptors important for urethral reflexes

• Not the main source of stretch signals for bladder emptying

✅ Correct Answer: Body of uterus

Explanation:

Step 1: Anterior relations of the urinary bladder

• Male:

  • Anterior to bladder: pubic bones, puboprostatic ligament, retropubic (Retzius) space.

• Female:

  • Anterior to bladder: pubic bones, pubovesical ligament, retropubic space.

  • Body of uterus lies superior and posterior to the bladder, not anterior.

Step 2: Clinical relevance

• Knowledge of these relationships is important during cystoscopy, suprapubic catheter placement, and pelvic surgery.

❌ Why the other options are incorrect:

Pubic bones

• True; directly anterior to bladder.

Puboprostatic ligament

• True in males; supports bladder and prostate anteriorly.

Retropubic space

• True; space between pubic symphysis and bladder, contains fat and vessels.

Pubo-vesical ligament

• True in females; connects bladder to pubis anteriorly.

✅ Correct Answer: SGLT2 (sodium-glucose cotransporter-2)

Explanation:

Step 1: Glucose reabsorption in the PCT

• The proximal convoluted tubule reabsorbs ~90% of filtered glucose.

• SGLT2 is located in the S1 segment of the PCT.

  • It is a low-affinity, high-capacity sodium-glucose cotransporter.

  • Couples 1 glucose molecule with 1 sodium ion into the tubular cell.

Step 2: Glucose exit into blood

• Inside the tubular cell, glucose exits via GLUT2 on the basolateral membrane into peritubular capillaries.

Step 3: SGLT1 function

• SGLT1 is in the S3 segment of the PCT.

  • It is a high-affinity, low-capacity transporter, responsible for the remaining ~10% of glucose reabsorption.

❌ Why the other options are incorrect:

GLUT2

• Basolateral transporter, not responsible for apical uptake in S1 segment.

GLUT3 / GLUT1

• Found in other tissues (neurons, erythrocytes), not primarily in PCT S1 segment.

SGLT1

• Located in S3 segment, not S1; handles a small fraction of glucose reabsorption

✅ Correct Answer: Columns of Bertin

Explanation:

Step 1: Definition

• Columns of Bertin are extensions of cortical tissue that project between the medullary pyramids into the medulla.

• They contain blood vessels, interlobar arteries, and cortical tissue.

Step 2: Function and clinical relevance

• Provide structural support and pathways for vascular supply between cortex and medulla.

• Can be mistaken for renal masses on imaging if prominent.

❌ Why the other options are incorrect:

Papillae

• Apex of the medullary pyramid, projecting into a minor calyx; not cortical.

Calyces

• Collect urine from the papillae; part of the renal collecting system, not cortical parenchyma.

Medullary rays

• Straight tubules and collecting ducts that extend from cortex into medulla; cortical tissue oriented differently, not between pyramids.

Renal lobules

• Functional units centered on medullary rays, including surrounding nephrons; broader concept, not specific to the tissue between pyramids.

✅ Correct Answer: 10 cm

Explanation:

Step 1: Normal kidney dimensions

• Adult kidney is roughly 10–12 cm in length, 5–7 cm in width, and 3 cm in thickness.

• The average length commonly cited in textbooks is about 10 cm, which is clinically significant for imaging and assessment of kidney health.

Step 2: Clinical relevance

• Kidney length is measured via ultrasound to detect atrophy, enlargement, or congenital anomalies.

• Kidneys smaller than 9 cm may indicate chronic kidney disease, while unusually large kidneys may suggest hydronephrosis, tumors, or diabetes-related hypertrophy.

❌ Why the other options are incorrect:

12 cm

• Upper limit of normal; not the average approximate length.

6–12 cm

• Too broad; includes abnormal lengths.

8–9 cm

• Smaller than typical adult kidney length.

11–13 cm

• Exceeds the normal range for average adult kidney; may indicate pathology or measurement in tall individuals.

The lymphatic drainage of the ureter is segmental, following its arterial supply:

• Superior portion (abdominal ureter): drains into the lateral aortic (paraaortic) lymph nodes near the origin of the renal vessels.

• Middle portion: drains into the common iliac nodes.

• Inferior portion (pelvic ureter): drains into the external iliac and internal iliac nodes.

Thus, the superior portion specifically drains into the lateral aortic nodes.

Why the Other Options Are Incorrect

• Internal iliac nodes ❌
  Drain the pelvic ureter, not the superior portion.

• Vesical nodes ❌
  Related to drainage of the bladder, not ureter.

• Common iliac nodes ❌
  Drain the middle ureter, not the superior portion.

• External iliac nodes ❌
  Drain the inferior ureter and bladder, not the superior portion.

The branching pattern of the renal blood supply is very structured:

1. Renal artery (branch of abdominal aorta)

2. → Segmental arteries

3. → Interlobar arteries (run between renal pyramids)

4. → Arcuate arteries (arch over the bases of pyramids at corticomedullary junction)

5. → Interlobular arteries (extend into cortex)

6. → Afferent arterioles → Glomerular capillaries → Efferent arterioles

Thus, the renal arterioles (afferent and efferent) arise as branches of the interlobular arteries in the cortex.

Why the Other Options Are Incorrect

• Abdominal aorta ❌
  It gives rise to the renal arteries, but arterioles are several branches downstream.

• Interlobar artery ❌
  These are larger arteries running between pyramids; they give rise to arcuate arteries, not directly to arterioles.

• Arcuate artery ❌
  These arch over pyramid bases and give rise to interlobular arteries, not directly to arterioles.

• Renal artery ❌
  Major artery entering the kidney; it divides further before reaching the level of arterioles.

✅ Correct Answer: Afferent glomerular arterioles arise mostly from arcuate arteries

Explanation:

Step 1: Normal renal arterial anatomy

• Renal artery → segmental arteries → interlobar arteries → arcuate arteries → interlobular (cortical radiate) arteries → afferent arterioles → glomeruli.

• So, afferent arterioles arise from interlobular arteries, not arcuate arteries.

Step 2: Other statements

• Interlobular arteries are end arteries

  • True; they have no significant collateral circulation, so occlusion leads to infarction.

• Renal circulation is of portal type

  • True; glomerular capillaries → efferent arterioles → peritubular capillaries forms a portal system.

• Kidney is divided into five vascular segments

  • True; kidney has five segmental arteries: apical, upper, middle, lower, posterior.

• Medulla receives blood mostly from efferent arterioles of glomeruli

  • True; vasa recta arise from efferent arterioles of juxtamedullary nephrons, supplying the medulla.

❌ Why the other options are correct:

• They accurately describe renal vascular anatomy and physiology, including end-artery nature, segmental divisions, portal circulation, and medullary blood supply.

The ureter receives a segmental blood supply along its course from multiple nearby arteries.

• In the abdominal part, the renal artery is the main contributor. Additional smaller branches may also come from the gonadal artery (testicular or ovarian) and the abdominal aorta.

• In the pelvic part, the blood supply mainly comes from branches of the internal iliac artery, such as the uterine artery (in females) or the inferior vesical artery (in males).

Therefore, for the abdominal ureter, the correct supply is the renal artery.

Why the Other Options Are Incorrect

• Abdominal aorta ❌
  While the aorta gives rise to renal, gonadal, and common iliac arteries, it does not directly supply the ureter in a primary sense.

• Uterine vessels ❌
  These supply the pelvic ureter in females, not the abdominal ureter.

• Inferior vena cava ❌
  A venous structure, not an artery — it drains blood, not supplies it.

• Arcuate artery ❌
  These are branches of the renal artery supplying the renal cortex, not the ureter.

The urinary bladder lies in the anterior part of the pelvis. Its anterior relations include:

• The pubic bones (pubic symphysis)

• The retropubic space (space of Retzius), which separates the bladder from the pubic symphysis

• In females: the pubo-vesical ligament (attaching bladder to pubis)

• In males: the puboprostatic ligament (connecting prostate and bladder to pubis)

The body of the uterus, however, lies posterior and superior to the bladder (the uterus rests on the bladder in females). Therefore, it is not an anterior relation.

Why the Other Options Are Incorrect

• Pubic bones ❌
  The pubic symphysis and bones lie directly in front of the bladder.

• Pubo-vesical ligament ❌
  Present in females, connects the bladder to the pubis — anterior relation.

• Puboprostatic ligament ❌
  Present in males, attaching the prostate and bladder to pubis — anterior relation.

• Retropubic space ❌
  A fat-filled space between bladder and pubic symphysis, directly anterior.