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What are the sources of development of kidney. Mention two congenital anomalies and give their reasons. [TU 2055,63/12]
Surgico-medical aspect of development of mesonephric duct and their derivatives. [TU 2062]
The urogenital system arises from intermediate mesoderm which forms a urogenital ridge on either side of the aorta. The urogenital ridge develops into three sets of tubular nephric structures (from head to tail): the pronephros, the mesonephros, and the metanephros.
A. The Pronephros
- Is the cranialmost set of tubes, which mostly regress.
B. The mesonephro
s - Is located along the midsection of the embryo and develops into mesonephric tubules and the mesonephric duct (Wolffian duct). These tubules carry out some kidney function at first, but then many of the tubules regress. However, the mesonephric duct persists and opens to the cloaca at the tail of the embryo.
C. The metanephros
- Gives rise to the definitive adult kidney. Develops from an outgrowth of the caudal mesonephric duct, the ureteric bud, and from a condensation of nearby renogenic intermediate mesoderm, the metanephric blastema.
- Steps in renogenesis - 1. Involves a process of reciprocal induction, which is retinoic acid dependent
- 2. Cranial-caudal patterning establishes a “renogenic” region within the intermediate mesoderm in the tail of the embryo –this renogenic mesoderm is the METANEPHRIC BLASTEMA
- 3. The METANEPHRIC BLASTEMA secretes growth factors that induce growth of the URETERIC BUD from the caudal portion of the mesonephric duct.
- 4. The URETERIC BUD proliferates and responds by secreting growth factors that stimulates proliferation and then differentiation of the metanephric blastema into glomeruli and kidney tubules (i.e. induces the blastema to undergo mesenchymal-to-epithelial transition ).
- 5. Perturbations in any aspect of these inductive events (e.g. mutations of either metanephric or ureteric factors or disruption of retinoic acid signaling) may cause inhibition of ureteric bud growth and renal hypoplasia or agenesis. Conversely, duplication or overproliferation of structures can occur if there is a gain of function of the inductive factors.
- Derivatives of the metanephric blastema:
- Podocytes covering glomerular capillaries
- Epithelial cells lining Bowman’s capsule
- Proximal convoluted tubules
- Descending thick limbs of the loops of Henle
- Thin limbs of the loops of Henle
- Ascending thick limbs of the loop of Henle
- Distal convoluted tubules
- Derivatives of the ureteric bud:
- Collecting tubules and ducts
- Minor and major calyces
Wolffian duct (Mesonephric duct): Derivatives?
- In females:
- * Gartner's duct, cyst
- In males:
- * Seminal vesicles
- * Epididymis
- * Ejaculatory duct
- * Ductus deferens
[@ Gardener's SEED]
Short note on Ascent of the kidneys?
- The kidneys initially form near the tail of the embryo.
- Vascular buds from the kidneys grow toward and invade the common iliac arteries.
- Growth of the embryo in length causes the kidneys to “ascend” to their final position in the lumbar region.
- Rather than “drag” their blood supply with them as they ascend, the kidneys send out new and slightly more cranial branches and then induce the regression of the more caudal branches.
Discuss the embryological basis of various congenital upper urinary tract anomalies. [TU 2063/2]
Malformations related to the ascent of the kidneys?
- Pelvic kidney : one or both kidneys stays in the pelvis rather than ascending
- Horseshoe kidney: the two developing kidneys fuse ventrally into a single, horseshoe shape that gets trapped in the abdomen by the inferior mesenteric artery.
- Supernumerary arteries: can often have more than one renal artery per kidney, which is often asymptomatic but can sometimes compress the ureter causing a backup of fluid into the renal pelvis and kidney tubules (hydronephrosis)
Urogenital sinus and its derivatives. [TU 2057,56,68]
Development of the bladder?
- The terminal part of the hindgut ends in the CLOACA, which is an endoderm-lined chamber that contacts the surface ectoderm at the cloacal membrane and communicates with the allantois, which is a membranous sac that extends into the umbilicus alongside the vitelline duct.
- The cloaca is then divided by the URORECTAL SEPTUM
- the DORSAL (inferior) portion develops into the RECTUM and ANAL CANAL
- the VENTRAL (superior) portion develops into the BLADDER and UROGENITAL SINUS, which will give rise to the bladder and lower urogenital tracts (prostatic and penile urethrae in males; urethra and lower vagina in females)
- As the bladder grows and expands, the distal ends of the mesonephric ducts are absorbed into the wall of the bladder as the TRIGONE.
Development of the adrenal cortex?
Arises mostly from intermediate mesoderm in the lumbar region of the embryo.
Development of the adrenal medulla?
Trunk neural crest cells migrate into the center of the adrenal glands and develop into the chromaffin cells of the adrenal medulla. These cells are essentially postganglionic sympathetic neurons that release epinephrine or norepinephrine directly into the bloodstream as opposed to innervating a target organ.
Describe the descent of testes and explain cryptorchidism. [TU 2066/1]
Describe in short the anomalies which may occur during descent of testis. [TU 2060/6]
Short note on descent of the testes?
- The testes arise in the lumbar region but then descend into pelvic cavity and through the inguinal canal to end up in the scrotum
- Descent of the testis is due to tethering of the testes to the anterior body wall by the gubernaculum. With growth and elongation of the embryo coupled with shortening of the gubernaculum, the testes are pulled through the body wall, then the inguinal canal, and finally into the scrotum.
Summary of male urogenital tract derivatives?
- Ureteric bud: ureter
- Mesonephric ducts: rete testis, efferent ducts, epididymis, vas deferens, seminal vesicle, trigone of bladder
- Urogenital sinus: bladder (except trigone), prostate gland, bulbourethral gland, urethra
Describe coverings of kidney and surgical importances. [TU 2066/1]
Each kidney has the following four coverings on its exterior.
- Fibrous capsule: It surrounds the kidney and is closely applied to its outer surface.
- Perirenal fat: It surrounds the fibrous capsule.
- Renal fascia (Gerota's fascia): It is a condensation of connective tissue and lies outside the perirenal fat. In addition to the kidney, it also encloses the suprarenal gland. The renal fascia is continuous with the fascia transversalis.
- Pararenal fat: It is found often in large quantity and lies external to the renal fascia. If forms part of the retroperitoneal fat.
Trigone of the urinary bladder. [TU 2054]
The trigone is a smooth triangular region of the internal urinary bladder formed by the two ureteral orifices and the internal urethral orifice.
The area is very sensitive to expansion and once stretched to a certain degree, the urinary bladder signals the brain of its need to empty. The signals become stronger as the bladder continues to fill.
Embryologically, the trigone of the bladder is derived from the caudal end of mesonephric ducts, which is of mesodermal origin (the rest of the bladder is endodermal). In the female the mesonephric ducts regresses, causing the trigone to be less prominent, but still present.
Pathology - Clinically important because infections (trigonitis) tend to persist in this region.
Structure in renal hilum
- from anterior to posterior
- - Renal Vein
- - Renal Artery
- - Pelvis
Mention briefly the extent and course along with its surgical importance of Right ureter. [TU 2064/5]
Size and Extent of ureter?
- Length: About 25 cm (10 inches)
- Diameter: About 3 mm
- Extent: Pelviureteric junction to urinary bladder
Parts, Courses and Relations of ureter?
- A) Pelvis of Ureter:
- Arises from the renal pelvis (leaves kidney from hilum situated medially) formed by calyces encircling the renal papillae
- Descends along the medial margin of the kidney
- At the lower end of kidney, it becomes continuous with the abdominal ureter.
- B) Abdominal ureter:
- Passes downwards and medially to lie on the medial edge of psoas major
- Then enters into the pelvis at the bifurcation of the common iliac artery in front of the sacroiliac joint.
- Anteriorly, the right ureter is covered at its origin by the 2nd part of the duodenum and then lies lateral to the inferior vena cava and behind the posterior peritoneum
- Right ureter is crossed by the testicular (or ovarian), right colic, and ileocolic vessels. The left ureter is crossed by the testicular (or ovarian) and left colic vessels
- Then passes above the pelvic brim, behind the mesosigmoid and sigmoid colon to cross the common iliac artery immediately above its bifurcation and enter the true (lesser) pelvis
- C) Pelvic ureter:
- Runs downwards and backwards on the lateral pelvic wall in front of the internal iliac artery to reach just in front of the ischial spine
- Then turns forwads and medially to enter the urinary bladder
- In the male it lies above the seminal vesicle near its termination and is crossed superficially by the vas deferens
- In the female, the ureter passes above the lateral fornix of the vagina lateral to the supravaginal portion of the cervix and lies below the broad ligament and uterine vessels
- D) Intravesical ureter:
- Passes obliquely through the wall of the bladder and open into it at the lateral angle of trigone
Normal Ureteric Contrictions?
- A) 3 Anatomical Constrictions:
- Pelviureteric junction
- Pelvic brim (Crossing of iliac vessels)
- Ureterovesical junction
- B) 5 Surgical Constrictions:
- Pelviureteric junction
- Pelvic brim (Crossing of iliac vessels)
- Crossing of Vas deferens(♂) / Broad ligament(♀)
- Ureterovesical junction
- Ureteric orifice (Intravesical)
Congenital anomalies of ureter?
1. Ureteral duplication: The mesonephric duct may give off a double metanephric bud so that 2 ureters may develop on one side (Double ureter) or both sides (Bifid ureter). These ureters may fuse into a single duct anywhere along their course or open separately into the bladder.
2. Ectopic ureter: Extra ureter may open ectopically into the vagina or urethra resulting in urinary incontinence.
3. Retrocaval ureter: Ureter deviates medially and passes behind the inferior vena cava, winding about and crossing in front of it from medial to lateral side. It may lead to right lumbar pain, recurrent urinary tact infections or episodes of acute pyelonephritis.
Nerve supply and action of brachialis and popliteus,. [TU]
Short notes on vas differens. [TU]
The ductus deferens forms part of the male internal genitalia where it transports sperm from the epididymis to the ejaculatory duct. In modern anatomic nomenclature, it is no longer referred to as the vas deferens.
The ductus deferens is a paired 30-45 cm muscular small caliber tube that connects the epididymis to the ejaculatory duct.
Course - The ductus deferens is the continuation of the tail of the epididymis and runs in the spermatic cord through the scrotum, inguinal canal and into the abdominal cavity, where it is extra-peritoneal. There it travels laterally through the pelvis, passing over (anterior to) the ureter and inferior to the bladder, where it unites with the duct of the seminal vesicle to form the ejaculatory duct in the prostate. In the prostate, the ejaculatory duct empties into the prostatic urethra.
- Blood supply -
- arterial: artery of the ductus deferens from the superior vesical artery (branch of anterior division of the internal iliac artery)
- venous: veins of the ductus deferens drain into the pelvic venous plexus
Short note on Pudendal nerve. [TU 2066/1]
The pudendal nerve arises from the S2-4 nerve roots of the anterior division of the sacral plexus. It is the nerve of the perineum and pelvic floor.
- The pudendal nerve arises from the anterior division of ventral rami of 2nd, 3rd and 4th sacral nerves of the sacral plexus.
- The nerve emerges from the pelvis and courses through the gluteal region through the greater sciatic foramen, below the piriformis muscle. It then turns forward around the sacrospinous ligament and leaves the gluteal region through the lesser sciatic foramen (between sacrotuberous and sacrospinous ligaments). It is then directed into the pudendal canal, which lies on the obturator fascia above the falciform ridge on the ischial tuberosity.
- Relations -
- - passes below lower border of piriformis muscle as it passes through greater sciatic foramen
- - lies on sacrospinous ligament just medial to spine of ischium as it passes through lesser sciatic foramen
- - travels through pudendal canal with internal pudendal vessels
- Anal, perineal, and genital sensation
- Anal and urethral sphincters, pelvic floor muscles
Explain the anatomy of superficial perineal pouch with its applied aspects. [TU 2072]
Superficial perineal pouch is a compartment of the perineum lying between the perineal membrane and urogenital diaphragm.
Boundaries and borders: Inferiorly, the superficial perineal pouch is bounded by membranous layer of perineal superficial fascia (Fascia of Colles). Superiorly, it is bounded by the urogenital diaphragm. Collis fascia is continuous with the dartos fascia of the penis and Scarpa's fascia upon the anterior wall of the abdomen;
The pouch is closed behind by the fusion of its superior and inferior boundaries. Laterally, it is closed by the attachment of the membranous layer of superficial fascia and urogenital diaphragm to the margins of pubic arch. Anteriorly, it communicates with the potential space between the superficial fascia of anterior abdominal wall and abdominal muscles.
- Superficial perineal pouch has the following contents:
- Crura of penis (in males) or clitoris (in females)
- Bulb of penis (in males) or vestibular bulbs (in females)
- Greater vestibular glands (only in females)
- Ischiocavernosus muscle
- Bulbospongiosus muscle
- Superficial transverse perineal muscle
What is deep perineal pouch?
- - Is bounded superiorly by superior fascia of urogenital diaphragm, inferiorly by inferior fascial of urogenital diaphragm.
- - Content - Urogenital diaphragm, external sphincter of bladder, cowper's gland (in male)
Branches of internal iliac artery?
Terminal branch of internal iliac artery -
Branches of external iliac artery?
- Inferior epigastric artery
- Deep circumflex iliac artery
- Femoral artery
Branches of femoral artery?
- Deep branches of femoral artery -
- 1. Profunda femoris (deep femoral artery) - that give medial and lateral circumflex femoral artery
- 2. Deep external pudendal
- 3. Descending genicular
- Superficial branches of femoral artery
- - Superficial circumflex iliac
- - Superficial epigastric
- - Superficial external pudendal artery
Discuss the various groups of inguinal lymph nodes and their surgical importance. [TU 2056,62]
Inguinal lymph nodes are the lymph nodes in the inguinal region. They are found in the femoral triangle, and are grouped into superficial nodes, and deep nodes.
The superficial inguinal lymph nodes are divided into three groups:
- Inferior – inferior of the saphenous opening of the leg, receive drainage from lower legs
- Superolateral – on the side of the saphenous opening, receive drainage from the side buttocks and the lower abdominal wall.
- Superomedial – located at the middle of the saphenous opening, take drainage from the perineum and outer genitalia.
- The deep inguinal lymph nodes:
- - arranged near and along the femoral vein of the leg.
- - drain the deep parts of the lower limbs, woman's clitoris, and man's penis.
- - connected to the superficial lymph nodes and send their drainage to those via lymph vessels