Chapter: Embryology; Topic: Development of Urinary System; Subtopic: Origin and Development of Ureteric Bud
Keyword Definitions:
Ureteric Bud: A diverticulum arising from the mesonephric duct that forms the collecting part of the kidney, including the ureter and pelvis.
Mesonephric Duct: Also called Wolffian duct; gives rise to male genital ducts and the ureteric bud.
Metanephros: The permanent kidney formed by interaction between the ureteric bud and metanephric blastema.
Pronephros and Mesonephros: Early embryonic kidney structures that are transient and replaced by the metanephros.
Lead Question - 2014
Ureteric bud arises from?
a) Paramesonephric Duct
b) Mullerian duct
c) Mesonephric duct
d) Mesonephric tubule
Explanation:
The ureteric bud arises as a dorsal outgrowth from the mesonephric (Wolffian) duct near the cloaca around the fifth week of development. It later differentiates into the ureter, renal pelvis, major and minor calyces, and collecting ducts. Therefore, the correct answer is c) Mesonephric duct. This process is vital for kidney formation through interaction with the metanephric blastema.
1. Which embryonic structure induces the formation of the metanephric blastema?
a) Mesonephros
b) Pronephros
c) Ureteric bud
d) Paramesonephric duct
Explanation:
The ureteric bud interacts with the surrounding metanephric mesenchyme (blastema), inducing it to form nephrons. This reciprocal induction process is crucial for kidney development. The correct answer is c) Ureteric bud. Without this signaling, the metanephric blastema fails to differentiate, leading to renal agenesis.
2. Clinical: A newborn with bilateral renal agenesis likely has a defect in which structure?
a) Mesonephric duct
b) Ureteric bud
c) Cloaca
d) Metanephric blastema
Explanation:
Bilateral renal agenesis results from failure of the ureteric bud to develop or interact with the metanephric blastema. The absence of this interaction leads to no kidney formation and severe oligohydramnios (Potter sequence). Thus, the correct answer is b) Ureteric bud.
3. Which of the following structures is derived from the ureteric bud?
a) Nephron
b) Collecting duct
c) Glomerulus
d) Bowman’s capsule
Explanation:
The ureteric bud forms the entire collecting system of the kidney, including the collecting ducts, renal pelvis, calyces, and ureter. Nephrons, glomeruli, and Bowman’s capsules arise from the metanephric blastema. Therefore, the correct answer is b) Collecting duct.
4. Clinical: Duplicated ureter is caused by which developmental abnormality?
a) Early division of the ureteric bud
b) Incomplete regression of mesonephros
c) Absence of metanephros
d) Delayed differentiation of pronephros
Explanation:
Duplication of ureter occurs due to premature branching or duplication of the ureteric bud before it contacts the metanephric blastema. Each branch induces its own collecting system, leading to double ureters or pelves. Hence, the correct answer is a) Early division of the ureteric bud.
5. The mesonephric duct gives rise to all except:
a) Ureteric bud
b) Vas deferens
c) Seminal vesicle
d) Urethra
Explanation:
The mesonephric duct gives rise to the male genital ducts, including the epididymis, vas deferens, and seminal vesicle, and also gives rise to the ureteric bud. However, the urethra develops from the urogenital sinus. Hence, the correct answer is d) Urethra.
6. Clinical: An ectopic ureter opening into the vagina indicates abnormal migration of which structure?
a) Ureteric bud
b) Metanephric blastema
c) Mesonephric duct
d) Paramesonephric duct
Explanation:
An ectopic ureter occurs when the ureteric bud migrates abnormally or connects improperly with the developing urogenital sinus. The condition leads to urinary incontinence in females. Therefore, the correct answer is a) Ureteric bud.
7. Which structure develops from the metanephric blastema?
a) Collecting duct
b) Renal pelvis
c) Nephron tubules
d) Ureter
Explanation:
Metanephric blastema differentiates into nephron tubules including Bowman’s capsule, proximal and distal convoluted tubules, and the loop of Henle. The collecting parts derive from the ureteric bud. Hence, the correct answer is c) Nephron tubules.
8. Clinical: Congenital hydronephrosis is due to obstruction in the outflow tract derived from:
a) Metanephric blastema
b) Ureteric bud
c) Mesonephric duct
d) Pronephros
Explanation:
Hydronephrosis occurs due to obstruction in the ureter, pelvis, or collecting ducts—all derived from the ureteric bud. The backup of urine causes renal dilation and cortical thinning. Therefore, the correct answer is b) Ureteric bud.
9. Which week marks the development of the ureteric bud?
a) 3rd week
b) 4th week
c) 5th week
d) 6th week
Explanation:
The ureteric bud appears as an outgrowth from the mesonephric duct during the fifth week of embryonic development. It extends dorsocranially to meet the metanephric blastema. Hence, the correct answer is c) 5th week.
10. Clinical: Absence of one kidney with a normal contralateral kidney is most likely due to failure of:
a) Mesonephric duct
b) One ureteric bud
c) Metanephric blastema
d) Pronephros
Explanation:
Unilateral renal agenesis results when one ureteric bud fails to form or fails to contact the metanephric blastema. The remaining kidney undergoes compensatory hypertrophy to maintain normal renal function. Thus, the correct answer is b) One ureteric bud.
Chapter: Embryology; Topic: Development of Cardiovascular System; Subtopic: Development and Derivatives of Vitelline Veins
Keyword Definitions:
Vitelline Veins: Paired embryonic veins that return blood from the yolk sac to the primitive heart tube and form parts of the portal and hepatic veins.
Inferior Vena Cava (IVC): Major vein returning deoxygenated blood from the lower body to the right atrium; partially derived from the right vitelline vein.
Hepatic Portal System: Venous network that carries blood from the gastrointestinal tract to the liver.
Ductus Venosus: A fetal vessel connecting the umbilical vein to the IVC, bypassing the liver during fetal circulation.
Lead Question - 2014
Derivative of vitelline vein?
a) IVC
b) SVC
c) Ligamentum venosum
d) Ligamentum teres
Explanation:
Vitelline veins drain blood from the yolk sac to the sinus venosus in the embryo. They later form hepatic sinusoids, the portal vein, superior mesenteric vein, and a portion of the inferior vena cava (hepatic segment). Therefore, the correct answer is a) IVC. The right vitelline vein mainly contributes to the hepatic segment of the IVC, while left parts regress.
1. The hepatic portal vein develops primarily from which embryonic vein?
a) Vitelline vein
b) Umbilical vein
c) Cardinal vein
d) Subcardinal vein
Explanation:
The hepatic portal vein develops from the anastomosis between the right and left vitelline veins around the duodenum. The vitelline venous system contributes to the hepatic sinusoids, portal vein, and part of the hepatic IVC. Hence, the correct answer is a) Vitelline vein.
2. Clinical: A newborn with portal hypertension likely has abnormal development of which embryonic structure?
a) Cardinal veins
b) Vitelline veins
c) Umbilical veins
d) Subcardinal veins
Explanation:
Abnormal development or malformation of vitelline veins can affect the hepatic portal system, leading to portal venous hypertension. These veins form the hepatic sinusoids and portal vein. Therefore, the correct answer is b) Vitelline veins.
3. The left vitelline vein primarily contributes to which structure?
a) Superior mesenteric vein
b) Hepatic veins
c) Ligamentum teres
d) Hepatic segment of IVC
Explanation:
The left vitelline vein largely regresses, but parts of it help form the hepatic sinusoids along with the right vitelline vein. The right vitelline vein contributes mainly to the hepatic veins and the hepatic segment of the IVC. Hence, the correct answer is b) Hepatic veins.
4. Clinical: Absence of hepatic segment of IVC is due to failure of which embryonic structure?
a) Vitelline vein
b) Subcardinal vein
c) Supracardinal vein
d) Umbilical vein
Explanation:
Failure of development or regression of the right vitelline vein results in the absence of the hepatic segment of the inferior vena cava. The rest of the IVC develops from subcardinal and supracardinal veins. Therefore, the correct answer is a) Vitelline vein.
5. The ductus venosus connects which two structures in the fetus?
a) Umbilical vein and portal vein
b) Umbilical vein and IVC
c) Portal vein and IVC
d) Hepatic vein and SVC
Explanation:
The ductus venosus shunts oxygenated blood from the left umbilical vein directly into the inferior vena cava, bypassing the liver. It ensures efficient oxygen delivery to the fetal brain and heart. After birth, it closes to form the ligamentum venosum. Hence, the correct answer is b) Umbilical vein and IVC.
6. Clinical: Persistent ductus venosus after birth leads to?
a) Cyanosis
b) Portal hypertension
c) Liver congestion
d) Polycythemia
Explanation:
If the ductus venosus remains patent after birth, portal blood bypasses the liver, causing hepatic dysfunction and portal hypertension. This persistence may lead to cyanosis and liver congestion. Thus, the correct answer is b) Portal hypertension.
7. Which vein forms the superior vena cava (SVC)?
a) Vitelline vein
b) Cardinal vein
c) Subcardinal vein
d) Umbilical vein
Explanation:
The superior vena cava (SVC) develops from the right common cardinal vein and the proximal part of the right anterior cardinal vein, not from the vitelline system. Therefore, the correct answer is b) Cardinal vein.
8. The ligamentum teres hepatis is derived from which fetal vessel?
a) Right umbilical vein
b) Left umbilical vein
c) Vitelline vein
d) Ductus venosus
Explanation:
The ligamentum teres hepatis is the fibrous remnant of the left umbilical vein, which carried oxygenated blood from the placenta to the fetus. After birth, it closes and becomes a fibrous cord in the falciform ligament. Hence, the correct answer is b) Left umbilical vein.
9. Clinical: Portal vein thrombosis in adults affects a structure derived from which embryonic vein?
a) Umbilical vein
b) Cardinal vein
c) Vitelline vein
d) Subcardinal vein
Explanation:
The portal vein originates from the vitelline venous system. Thrombosis in this vessel can cause portal hypertension and liver dysfunction. Therefore, embryologically, the affected structure is derived from the c) Vitelline vein.
10. The superior mesenteric vein is formed from:
a) Right vitelline vein
b) Left vitelline vein
c) Umbilical vein
d) Subcardinal vein
Explanation:
The superior mesenteric vein develops from the right vitelline vein near the duodenum. This part of the vitelline system drains the midgut and later contributes to the portal venous system. Hence, the correct answer is a) Right vitelline vein.
Chapter: Embryology; Topic: Development of Gonads; Subtopic: Ovary Development
Keyword Definitions:
• Genital ridge: A thickened area of intermediate mesoderm where gonads develop.
• Sex cords: Cellular cords derived from coelomic epithelium forming gonadal structures.
• Oocytes: Female germ cells derived from primordial germ cells of endodermal origin.
• Follicles: Functional units in the ovary containing developing oocytes surrounded by granulosa cells.
Lead Question – 2014
Not true about development of ovary?
a) Develops in genital ridge
b) Sex cords are derived from coelomic epithelium
c) Oocytes are mesodermal in origin
d) At birth ovary contains 2 million follicles
Explanation:
The correct answer is (c) Oocytes are mesodermal in origin. Oocytes are derived from primordial germ cells, which originate from the yolk sac endoderm and migrate to the genital ridge. The genital ridge arises from intermediate mesoderm, while sex cords arise from coelomic epithelium. At birth, around 2 million follicles remain in each ovary.
1. The medullary cords in ovary develop into?
a) Theca cells
b) Primordial follicles
c) Interstitial cells
d) Corpus luteum
Explanation:
The correct answer is (c) Interstitial cells. Medullary cords in the ovary regress during development, leaving behind interstitial cells derived from the mesenchymal tissue. These cells are hormonally active and play a role in early ovarian steroidogenesis before follicular development begins.
2. Primordial germ cells arise from?
a) Yolk sac endoderm
b) Coelomic epithelium
c) Mesonephros
d) Genital ridge
Explanation:
The correct answer is (a) Yolk sac endoderm. Primordial germ cells originate from the wall of the yolk sac near the allantois and migrate to the developing gonadal ridge. They later differentiate into oogonia in females or spermatogonia in males, determining the gonadal fate.
3. Cortical cords of the ovary develop into?
a) Theca interna
b) Granulosa cells
c) Oogonia
d) Corpus albicans
Explanation:
The correct answer is (b) Granulosa cells. The cortical cords, derived from coelomic epithelium, break into clusters surrounding the oogonia, forming primordial follicles. Granulosa cells support and nourish the developing oocyte and are essential for hormone secretion and follicular maturation.
4. The indifferent gonad appears at which week of gestation?
a) 3rd week
b) 4th week
c) 5th week
d) 6th week
Explanation:
The correct answer is (5th week). The indifferent gonad begins to develop from the intermediate mesoderm during the 5th week. The differentiation into testis or ovary occurs later, guided by genetic and hormonal influences, particularly the presence or absence of the SRY gene on the Y chromosome.
5. In Turner’s syndrome, the gonads develop as?
a) Normal ovaries
b) Streak gonads
c) Dysgenetic testes
d) Ambiguous gonads
Explanation:
The correct answer is (b) Streak gonads. Turner’s syndrome (45,XO) results in underdeveloped gonads known as streak gonads due to absence of one X chromosome. These gonads are nonfunctional fibrous streaks, leading to infertility and lack of secondary sexual characteristics.
6. Clinical: A 20-year-old female with primary amenorrhea and high gonadotropins is diagnosed with streak gonads. What is the chromosomal pattern?
a) 46,XX
b) 45,XO
c) 47,XXX
d) 46,XY
Explanation:
The correct answer is (b) 45,XO. In Turner’s syndrome, streak gonads fail to produce estrogen, leading to elevated FSH and LH levels. The 45,XO karyotype results in short stature, webbed neck, and primary amenorrhea due to absence of ovarian follicular development.
7. Clinical: A newborn female with ambiguous genitalia has 46,XY karyotype. The gonads are undescended. Diagnosis?
a) Androgen insensitivity
b) Gonadal dysgenesis
c) True hermaphroditism
d) Congenital adrenal hyperplasia
Explanation:
The correct answer is (a) Androgen insensitivity. In this disorder, despite 46,XY karyotype, androgen receptors are defective, leading to female external genitalia and undescended testes. The gonads do not differentiate into functional ovaries or testes, a form of testicular feminization.
8. Clinical: A 25-year-old woman with infertility shows multiple small cystic follicles and hyperandrogenism. What is the diagnosis?
a) Turner’s syndrome
b) Polycystic ovary syndrome
c) Premature ovarian failure
d) Mullerian agenesis
Explanation:
The correct answer is (b) Polycystic ovary syndrome. PCOS is caused by hormonal imbalance leading to multiple small cystic follicles, anovulation, and infertility. It is associated with obesity, insulin resistance, and increased LH to FSH ratio, affecting follicular maturation.
9. Clinical: A 15-year-old girl presents with absence of secondary sexual characteristics but normal external genitalia. Likely cause?
a) Gonadal dysgenesis
b) Pituitary tumor
c) Hypothalamic dysfunction
d) Uterine agenesis
Explanation:
The correct answer is (a) Gonadal dysgenesis. In gonadal dysgenesis, ovaries fail to differentiate properly, resulting in lack of estrogen production and secondary sexual development. These individuals present with primary amenorrhea and elevated FSH and LH levels, indicating gonadal failure.
10. Clinical: A 17-year-old female presents with cyclic abdominal pain but no menstruation. On examination, vagina is absent. Diagnosis?
a) Mullerian agenesis
b) Turner’s syndrome
c) Gonadal dysgenesis
d) Imperforate hymen
Explanation:
The correct answer is (a) Mullerian agenesis. In this condition, also called Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome, the Müllerian ducts fail to develop, leading to absence of uterus and upper vagina. The ovaries are normal, and secondary sexual characteristics develop normally due to functional gonads.
Chapter: Embryology; Topic: Development of Genital System; Subtopic: Descent of Testis
Keyword Definitions:
• Deep inguinal ring: Opening in the transversalis fascia through which the spermatic cord and testis descend during fetal life.
• Gubernaculum: Fibrous cord that guides testicular descent into the scrotum.
• Processus vaginalis: Peritoneal diverticulum that accompanies testicular descent.
• Cryptorchidism: Condition where one or both testes fail to descend into the scrotum.
Lead Question – 2014
Testis lies at deep inguinal ring upto?
a) 4 months
b) 5 months
c) 7 months
d) 9 months
Explanation:
The correct answer is (c) 7 months. The testis descends from the posterior abdominal wall to the deep inguinal ring by the 7th month of intrauterine life. It passes through the inguinal canal in the 8th month and reaches the scrotum by the 9th month. This descent is guided by the gubernaculum and controlled hormonally by testosterone and INSL3.
1. Which structure guides the descent of the testis?
a) Processus vaginalis
b) Gubernaculum
c) Cremaster muscle
d) Tunica albuginea
Explanation:
The correct answer is (b) Gubernaculum. The gubernaculum is a fibromuscular structure extending from the lower pole of the testis to the scrotum. It shortens and helps in the transabdominal and inguinoscrotal descent of the testis, under the influence of androgens and genitofemoral nerve stimulation.
2. The processus vaginalis later forms which structure in adults?
a) Tunica vaginalis
b) Tunica albuginea
c) Cremasteric fascia
d) Dartos fascia
Explanation:
The correct answer is (a) Tunica vaginalis. The processus vaginalis is a peritoneal diverticulum that descends with the testis. Its distal part remains as tunica vaginalis covering the front and sides of the testis, while the proximal portion normally obliterates. Failure of closure may lead to congenital hernia or hydrocele.
3. Which hormone primarily regulates testicular descent?
a) Testosterone
b) LH
c) FSH
d) Progesterone
Explanation:
The correct answer is (a) Testosterone. Testosterone secreted by fetal Leydig cells promotes gubernacular shortening and migration of the testis into the scrotum. In addition, Insulin-like peptide 3 (INSL3) and genitofemoral nerve-mediated calcitonin gene-related peptide (CGRP) also play critical roles in testicular descent.
4. The inguinoscrotal phase of testicular descent occurs in which month?
a) 5th month
b) 6th month
c) 7th month
d) 8th month
Explanation:
The correct answer is (d) 8th month. The descent of the testis occurs in two phases: transabdominal (by 3–7 months) and inguinoscrotal (by 7–9 months). During the inguinoscrotal phase, the testis passes through the inguinal canal into the scrotum, guided by the gubernaculum and controlled by hormonal and neural factors.
5. Failure of testicular descent is known as?
a) Ectopic testis
b) Cryptorchidism
c) Hydrocele
d) Varicocele
Explanation:
The correct answer is (b) Cryptorchidism. Cryptorchidism is a developmental defect where the testis fails to descend into the scrotum, remaining in the abdomen or inguinal canal. It leads to infertility due to higher intra-abdominal temperature and increased risk of malignancy and hernia formation.
6. Clinical: A 2-year-old boy presents with empty scrotum. Testis is palpable in the inguinal canal. Diagnosis?
a) Ectopic testis
b) Retractile testis
c) Undescended testis
d) Anorchia
Explanation:
The correct answer is (c) Undescended testis. Undescended (cryptorchid) testis is located along the normal path of descent, commonly within the inguinal canal. It may descend spontaneously by one year of age; if not, orchiopexy is indicated to prevent infertility and testicular malignancy later in life.
7. Clinical: A 3-year-old has testis located in the perineum. What is the condition?
a) Ectopic testis
b) Undescended testis
c) Retractile testis
d) Anorchia
Explanation:
The correct answer is (a) Ectopic testis. Ectopic testis deviates from the normal path of descent and may be found in perineal, femoral, or suprapubic regions. The gubernaculum attaches abnormally, misdirecting the testis. Surgical repositioning is necessary to preserve fertility and avoid complications.
8. Clinical: A newborn with right-sided scrotal swelling transilluminates. Diagnosis?
a) Hydrocele
b) Varicocele
c) Hernia
d) Epididymitis
Explanation:
The correct answer is (a) Hydrocele. Hydrocele results from persistence of the processus vaginalis, allowing peritoneal fluid to accumulate around the testis. It presents as a painless, fluctuant, transilluminant swelling in the scrotum, often resolving spontaneously within the first year of life.
9. Clinical: A 20-year-old male has infertility due to failure of testicular descent. What is the most likely histologic change?
a) Leydig cell hyperplasia
b) Seminiferous tubule atrophy
c) Germ cell proliferation
d) Sertoli cell hypertrophy
Explanation:
The correct answer is (b) Seminiferous tubule atrophy. In undescended testes, high temperature impairs spermatogenesis, causing seminiferous tubule atrophy. Leydig cells remain relatively preserved but may undergo hyperplasia. Early surgical correction improves fertility outcomes but does not completely reverse germ cell loss.
10. Clinical: A male infant has absent left testis on examination and ultrasonography. Most probable condition?
a) Retractile testis
b) Anorchia
c) Ectopic testis
d) Torsion of testis
Explanation:
The correct answer is (b) Anorchia. Anorchia refers to congenital absence of one or both testes due to early testicular regression during fetal life. The scrotum appears underdeveloped, and serum testosterone levels are low. Diagnosis is confirmed by ultrasound and hormone assays (low testosterone, high LH/FSH).
Chapter: Embryology; Topic: Development of Genital System; Subtopic: Descent of Testis
Keyword Definitions:
• Testicular descent: The process by which the testes move from the posterior abdominal wall to the scrotum during fetal life.
• Inguinal canal: A passage in the anterior abdominal wall through which the testis descends into the scrotum.
• Gubernaculum: A fibromuscular cord guiding testicular descent.
• Processus vaginalis: A peritoneal diverticulum accompanying the testis during descent, forming the tunica vaginalis later.
Lead Question – 2014
Position of testis at 24–28 weeks of intrauterine life?
a) Inguinal canal
b) Lumbar region
c) Superficial inguinal ring
d) Deep inguinal ring
Explanation:
The correct answer is (d) Deep inguinal ring. At 24–28 weeks of gestation, the testis reaches the deep inguinal ring after descending from the posterior abdominal wall. From the 28th to 32nd week, it traverses the inguinal canal and reaches the scrotum by the 9th month. This process is guided by the gubernaculum and influenced by testosterone and intra-abdominal pressure.
1. During which month of gestation does the testis reach the scrotum?
a) 5th month
b) 7th month
c) 8th month
d) 9th month
Explanation:
The correct answer is (d) 9th month. The testis completes its descent into the scrotum by the 9th month of intrauterine life. Descent occurs in two phases: transabdominal (by 3–7 months) and inguinoscrotal (7–9 months). The gubernaculum and genitofemoral nerve–mediated calcitonin gene-related peptide (CGRP) regulate this descent.
2. Which structure forms the pathway for the descent of testis?
a) Inguinal ligament
b) Gubernaculum
c) Cremaster muscle
d) Dartos fascia
Explanation:
The correct answer is (b) Gubernaculum. The gubernaculum anchors the testis to the scrotum and guides its descent through the inguinal canal. Under hormonal control (testosterone and INSL3), it shortens and pulls the testis into position. Abnormal gubernacular development can cause undescended or ectopic testis.
3. What is the fate of processus vaginalis after testicular descent?
a) Forms tunica vaginalis
b) Forms cremaster muscle
c) Forms dartos muscle
d) Obliterates completely
Explanation:
The correct answer is (a) Forms tunica vaginalis. The distal part of the processus vaginalis persists as the tunica vaginalis around the anterior and lateral sides of the testis, while the proximal portion obliterates. If it remains patent, congenital hydrocele or indirect inguinal hernia may result.
4. Which phase of testicular descent is controlled by INSL3 hormone?
a) Inguinoscrotal phase
b) Transabdominal phase
c) Both phases
d) Postnatal phase
Explanation:
The correct answer is (b) Transabdominal phase. INSL3 (Insulin-like 3 hormone) secreted by fetal Leydig cells acts on gubernaculum receptors to mediate the transabdominal phase of testicular descent. The inguinoscrotal phase, in contrast, is primarily androgen- and genitofemoral nerve–dependent.
5. Failure of testicular descent results in which condition?
a) Hydrocele
b) Varicocele
c) Cryptorchidism
d) Orchitis
Explanation:
The correct answer is (c) Cryptorchidism. Cryptorchidism refers to undescended testes that fail to reach the scrotum. It occurs in about 3% of full-term males and 30% of preterm males. Untreated cases may lead to infertility, testicular cancer, and torsion due to elevated temperature in the abdomen.
6. Clinical: A 1-year-old boy presents with empty scrotum and palpable testis in the inguinal canal. Diagnosis?
a) Ectopic testis
b) Retractile testis
c) Undescended testis
d) Anorchia
Explanation:
The correct answer is (c) Undescended testis. Undescended testis (cryptorchidism) is located along the normal descent pathway, usually in the inguinal canal. Early orchiopexy before 1 year of age is advised to prevent infertility, testicular torsion, and malignancy risk in adulthood.
7. Clinical: A 2-year-old male has a painless, transilluminant swelling in the scrotum. What is the diagnosis?
a) Varicocele
b) Hydrocele
c) Hernia
d) Epididymal cyst
Explanation:
The correct answer is (b) Hydrocele. Hydrocele results from persistence of the processus vaginalis allowing peritoneal fluid to collect around the testis. It appears as a smooth, fluctuant, transilluminant scrotal swelling, commonly resolving spontaneously within infancy or treated surgically if persistent.
8. Clinical: A 3-year-old boy has testis located in the perineum. This represents?
a) Ectopic testis
b) Retractile testis
c) Cryptorchidism
d) Hypogonadism
Explanation:
The correct answer is (a) Ectopic testis. An ectopic testis deviates from the normal descent pathway and may be found in the perineum, thigh, or femoral region. The gubernaculum misdirects the testis. Surgical correction is required to prevent infertility and potential malignancy.
9. Clinical: A newborn’s left testis is not found even in the abdomen on ultrasound. Most likely diagnosis?
a) Undescended testis
b) Ectopic testis
c) Anorchia
d) Retractile testis
Explanation:
The correct answer is (c) Anorchia. Anorchia or “vanishing testis syndrome” results from early vascular accident or regression of the testis during fetal life. It presents with empty scrotum and absent testis on imaging. Elevated gonadotropins (FSH, LH) and low testosterone levels confirm the diagnosis.
10. Clinical: A male infant with inguinal hernia is found to have patent processus vaginalis. The embryologic defect involved is?
a) Gubernaculum persistence
b) Failure of processus vaginalis obliteration
c) Absent tunica albuginea
d) Premature testicular descent
Explanation:
The correct answer is (b) Failure of processus vaginalis obliteration. If the proximal part of the processus vaginalis fails to close, abdominal contents may herniate into the inguinal canal, forming an indirect inguinal hernia. This condition often coexists with hydrocele and is corrected surgically to prevent complications.
Chapter: Embryology; Topic: Development of Germ Layers; Subtopic: Notochord Formation
Keyword Definitions:
• Notochord: A rod-like structure derived from mesoderm that defines the body’s axial orientation and induces neural tube formation.
• Hypoblast: The lower layer of the bilaminar disc, contributing to the extraembryonic endoderm.
• Induction: The process by which one group of embryonic cells influences the development of another.
• Nucleus pulposus: The central, gelatinous core of the intervertebral disc, derived from notochordal remnants.
Lead Question – 2014
True about notochord are all except?
a) Defines axis of embryo
b) Serves as primary inductor
c) Derived from hypoblast
d) Remains as nucleus pulposus
Explanation:
The correct answer is (c) Derived from hypoblast. The notochord develops from the mesodermal cells of the primitive streak and node, not from the hypoblast. It defines the embryonic axis, acts as a primary inductor in neural development, and later persists as the nucleus pulposus in intervertebral discs. Hypoblast mainly contributes to the yolk sac lining.
1. The notochord is first formed during which week of development?
a) 1st week
b) 2nd week
c) 3rd week
d) 4th week
Explanation:
The correct answer is (c) 3rd week. The notochord forms during the third week from mesodermal cells migrating through the primitive node. It plays a vital role in establishing the midline and inducing the neural plate to form the neural tube. This event marks the beginning of organogenesis in embryonic development.
2. The structure that induces the formation of the neural tube is?
a) Somite
b) Notochord
c) Neural crest
d) Yolk sac
Explanation:
The correct answer is (b) Notochord. The notochord secretes morphogens like SHH (Sonic Hedgehog) that induce the overlying ectoderm to thicken and form the neural plate, which later folds into the neural tube. This process is called neural induction, a fundamental event in central nervous system development.
3. The notochord is derived from which embryonic germ layer?
a) Ectoderm
b) Mesoderm
c) Endoderm
d) Hypoblast
Explanation:
The correct answer is (b) Mesoderm. The notochord arises from axial mesoderm formed by the cells migrating cranially through the primitive node. It separates the ectoderm and endoderm along the midline, providing structural support and molecular signals guiding differentiation of surrounding tissues such as somites and neural tube.
4. The remnant of the notochord in adults is known as?
a) Ligamentum flavum
b) Nucleus pulposus
c) Annulus fibrosus
d) Conus medullaris
Explanation:
The correct answer is (b) Nucleus pulposus. The notochord degenerates in most regions but persists as the nucleus pulposus in intervertebral discs. This gelatinous structure provides cushioning between vertebrae, maintaining spinal flexibility. Surrounding mesenchymal tissue forms the annulus fibrosus, the tough outer ring of the disc.
5. The primitive streak gives rise to all the following except?
a) Notochord
b) Endoderm
c) Ectoderm
d) Mesoderm
Explanation:
The correct answer is (c) Ectoderm. The primitive streak forms mesoderm and endoderm as epiblast cells migrate through it. The cells that remain in place become ectoderm. The primitive node at its anterior end produces the notochordal process, which later develops into the notochord.
6. Clinical: A newborn has remnants of the notochord forming a midline mass at the base of the skull. What is the diagnosis?
a) Teratoma
b) Craniopharyngioma
c) Chordoma
d) Meningocele
Explanation:
The correct answer is (c) Chordoma. Chordoma is a malignant tumor arising from notochordal remnants, often at the skull base (clivus) or sacrococcygeal region. It grows slowly but can invade bone and neural tissue. Histologically, it shows physaliphorous cells with vacuolated cytoplasm, confirming notochordal origin.
7. Clinical: A defect in notochordal signaling affects vertebral column formation. Which anomaly results?
a) Scoliosis
b) Spina bifida
c) Hemivertebra
d) Anencephaly
Explanation:
The correct answer is (c) Hemivertebra. Hemivertebra occurs when notochordal signaling fails to properly segment sclerotomes, leading to incomplete vertebral development. This results in lateral curvature of the spine (congenital scoliosis). Proper notochordal function is crucial for symmetrical vertebral body formation and axial alignment.
8. Clinical: A 20-week fetus shows defective neural tube closure due to disrupted SHH pathway. Which embryonic structure is primarily affected?
a) Notochord
b) Somite
c) Yolk sac
d) Amnion
Explanation:
The correct answer is (a) Notochord. Abnormal Sonic Hedgehog (SHH) expression from the notochord impairs neural tube induction, leading to defects like spina bifida or anencephaly. The notochord serves as a key signaling center directing neural and somite patterning during organogenesis.
9. Clinical: Which of the following results if the notochord fails to induce vertebral body formation?
a) Spina bifida
b) Hemivertebra
c) Vertebral agenesis
d) Myelomeningocele
Explanation:
The correct answer is (c) Vertebral agenesis. Failure of notochordal induction during mesodermal segmentation results in vertebral agenesis, where certain vertebral bodies do not develop. This can cause severe spinal deformities and neurological deficits due to loss of structural support and alignment along the vertebral column.
10. Clinical: A midline sacrococcygeal mass containing notochordal tissue remnants is most likely?
a) Sacrococcygeal teratoma
b) Chordoma
c) Lipoma
d) Dermoid cyst
Explanation:
The correct answer is (b) Chordoma. Sacrococcygeal chordomas are rare, slow-growing tumors originating from notochordal remnants. They often present with pain or bowel obstruction. Despite slow growth, they are locally aggressive and may recur after resection, emphasizing the embryologic importance of notochordal regression in normal development.
Chapter: Embryology; Topic: Development of Germ Layers; Subtopic: Notochord and Its Derivatives
Keyword Definitions:
• Notochord: A rod-like midline structure derived from mesoderm that defines the embryo’s axis and induces neural tube formation.
• Nucleus pulposus: The gelatinous central core of the intervertebral disc, a remnant of the embryonic notochord.
• Annulus fibrosus: The outer fibrocartilaginous ring surrounding the nucleus pulposus, derived from sclerotome.
• Intervertebral disc: A cushion between vertebrae formed from notochordal and mesenchymal tissues.
Lead Question – 2014
Remnant of notochord is ?
a) Annulus fibrosus
b) Nucleus pulposus
c) Ligament flavum
d) Intertransverse ligament
Explanation:
The correct answer is (b) Nucleus pulposus. During embryonic development, the notochord serves as the primary axial structure and induces the neural tube. Most of it degenerates as the vertebral column forms, but remnants persist as the nucleus pulposus in the intervertebral discs. The annulus fibrosus originates from the surrounding mesenchymal cells, not the notochord.
1. The notochord develops from which embryonic layer?
a) Ectoderm
b) Mesoderm
c) Endoderm
d) Hypoblast
Explanation:
The correct answer is (b) Mesoderm. The notochord forms from mesodermal cells that migrate cranially from the primitive node. It provides structural support and releases molecular signals such as Sonic Hedgehog (SHH), which guides the development of the neural tube, somites, and surrounding tissues, playing a vital role in body axis formation.
2. Which of the following structures is derived from the notochord?
a) Neural tube
b) Nucleus pulposus
c) Annulus fibrosus
d) Vertebral body
Explanation:
The correct answer is (b) Nucleus pulposus. The nucleus pulposus is the only adult derivative of the notochord. It forms the gelatinous center of intervertebral discs, maintaining spinal flexibility and cushioning vertebrae. The rest of the notochord degenerates as vertebral bodies form around it from mesenchymal sclerotome tissue.
3. The notochord acts as a primary inductor for the development of which structure?
a) Neural tube
b) Amnion
c) Somites
d) Gut tube
Explanation:
The correct answer is (a) Neural tube. The notochord induces the overlying ectoderm to form the neural plate, which folds to form the neural tube, the precursor of the central nervous system. It releases morphogens like SHH, which pattern the ventral neural tube and influence somite differentiation.
4. The vertebral bodies develop from which embryonic source?
a) Notochord
b) Paraxial mesoderm
c) Lateral plate mesoderm
d) Neural crest
Explanation:
The correct answer is (b) Paraxial mesoderm. Paraxial mesoderm segments into somites, which form sclerotomes. Sclerotomes give rise to vertebral bodies and ribs, surrounding the degenerating notochord. The notochord itself persists only as the nucleus pulposus, highlighting the interaction between mesodermal derivatives in axial skeleton formation.
5. The primitive streak gives rise to which of the following?
a) Notochord
b) Neural crest
c) Yolk sac
d) Surface ectoderm
Explanation:
The correct answer is (a) Notochord. The primitive streak is the site where epiblast cells migrate inward to form the three germ layers. The cranial extension of the streak, known as the primitive node, forms the notochordal process, which later differentiates into the definitive notochord that defines the body’s longitudinal axis.
6. Clinical: A midline sacrococcygeal tumor arising from notochord remnants is known as?
a) Chordoma
b) Teratoma
c) Lipoma
d) Ependymoma
Explanation:
The correct answer is (a) Chordoma. Chordomas are rare, malignant tumors originating from notochordal remnants, typically found at the skull base or sacrococcygeal region. They grow slowly but are locally aggressive, eroding bone and compressing adjacent structures. Histologically, they contain physaliphorous cells with vacuolated cytoplasm, confirming notochordal origin.
7. Clinical: A defect in notochord formation will primarily affect which system?
a) Nervous system
b) Digestive system
c) Respiratory system
d) Cardiovascular system
Explanation:
The correct answer is (a) Nervous system. Defective notochordal induction leads to improper formation of the neural plate, resulting in neural tube defects such as spina bifida and anencephaly. The notochord provides essential signals guiding neural differentiation and patterning of the developing central nervous system.
8. Clinical: Which congenital anomaly results from persistent notochordal tissue in the vertebral region?
a) Spina bifida
b) Chordoma
c) Hemivertebra
d) Scoliosis
Explanation:
The correct answer is (b) Chordoma. Persistent notochordal tissue in the vertebral axis can give rise to a chordoma. These tumors often develop in the sacral or cranial region, presenting as a destructive lesion causing pain or neurological symptoms. Their embryologic origin from the notochord distinguishes them from other spinal tumors.
9. Clinical: Failure of notochordal signaling to mesoderm leads to which skeletal deformity?
a) Hemivertebra
b) Polydactyly
c) Spina bifida
d) Kyphosis
Explanation:
The correct answer is (a) Hemivertebra. Incomplete notochordal signaling results in asymmetric vertebral body development. A hemivertebra forms when one half of a vertebra fails to develop, leading to congenital scoliosis. Proper notochordal signaling ensures bilateral symmetry in vertebral segmentation and skeletal axis formation.
10. Clinical: A 50-year-old patient presents with a destructive skull base mass derived from notochordal remnants. What is the most likely diagnosis?
a) Osteosarcoma
b) Chordoma
c) Meningioma
d) Schwannoma
Explanation:
The correct answer is (b) Chordoma. Chordoma of the clivus (skull base) arises from embryonic notochordal remnants. It typically causes cranial nerve compression, leading to diplopia or headache. Imaging shows a midline lytic lesion. Despite surgical resection and radiotherapy, recurrence is common due to its slow but invasive growth pattern.
Chapter: Embryology; Topic: Development of Gastrointestinal Tract; Subtopic: Development of Duodenum
Keyword Definitions:
Foregut: Gives rise to pharynx, esophagus, stomach, and part of duodenum up to the opening of bile duct.
Midgut: Forms distal duodenum, jejunum, ileum, and part of large intestine.
Duodenum: The first part of the small intestine, divided into four parts.
Embryonic origin: Refers to the germ layer or gut region from which an organ develops.
Lead Question – 2014
2nd part of duodenum is derived from?
a) Foregut
b) Midgut
c) Both foregut & midgut
d) Hindgut
Explanation:
The second part of the duodenum (descending part) develops partly from the terminal foregut and partly from the proximal midgut. The site where the bile and pancreatic ducts open marks the junction between these two regions. Hence, the correct answer is c) Both foregut & midgut. This dual origin is important for blood supply variations and surgical relevance.
1) The junction between foregut and midgut in the duodenum is marked by?
a) Pylorus
b) Ampulla of Vater
c) Ligament of Treitz
d) Duodenojejunal flexure
The foregut–midgut junction lies near the opening of the bile and pancreatic ducts into the second part of the duodenum, known as the Ampulla of Vater. This region receives dual blood supply from both celiac trunk and superior mesenteric artery, reflecting its embryonic dual origin.
2) Which artery supplies the foregut-derived part of duodenum?
a) Superior mesenteric artery
b) Inferior mesenteric artery
c) Celiac trunk
d) Internal iliac artery
The part of duodenum derived from the foregut is supplied by the Celiac trunk via its branch, the superior pancreaticoduodenal artery. This dual supply pattern is essential in surgeries involving pancreatic head and duodenal resection to prevent ischemic injury.
3) Which part of the duodenum is related to the head of pancreas?
a) First
b) Second
c) Third
d) Fourth
The second part (descending part) of the duodenum is closely related to the head of pancreas. The bile and pancreatic ducts open here, forming the hepatopancreatic ampulla. This anatomical relation is vital in understanding obstructive jaundice due to carcinoma of the pancreatic head.
4) During development, the duodenum becomes C-shaped due to?
a) Growth of stomach
b) Rotation of stomach and pancreas
c) Migration of liver
d) Elongation of midgut
The rotation of the stomach and pancreas causes the duodenum to acquire its C-shaped configuration and become retroperitoneal. This process brings the bile and pancreatic ducts into close proximity, establishing the hepatopancreatic junction.
5) The epithelial lining of duodenum develops from?
a) Endoderm
b) Mesoderm
c) Ectoderm
d) Neural crest
The epithelial lining of the duodenum is derived from endoderm, which also forms the epithelial cells of other parts of the digestive tract. The surrounding smooth muscle and connective tissue arise from splanchnic mesoderm. This combination forms a fully functional intestinal wall.
6) A neonate presents with bilious vomiting soon after birth. The most likely cause is?
a) Hypertrophic pyloric stenosis
b) Duodenal atresia
c) Hirschsprung disease
d) Malrotation
Bilious vomiting in a neonate indicates obstruction below the opening of the bile duct. Duodenal atresia is a congenital condition caused by failure of recanalization of the duodenum. It is associated with polyhydramnios and the “double bubble” sign on X-ray.
7) Which congenital anomaly involves annular pancreas encircling duodenum?
a) Meckel’s diverticulum
b) Annular pancreas
c) Hirschsprung’s disease
d) Malrotation
In Annular pancreas, the ventral pancreatic bud abnormally encircles the duodenum, causing obstruction. It is due to abnormal migration during rotation of the foregut. This leads to vomiting and feeding intolerance in neonates, often requiring surgical correction.
8) The duodenojejunal flexure lies at which vertebral level?
a) L1
b) L2
c) L3
d) L4
The duodenojejunal flexure lies at the left side of the L2 vertebra, supported by the suspensory ligament of Treitz. This structure marks the end of the duodenum and beginning of the jejunum. Its position is clinically important in differentiating upper from lower GI bleeding.
9) Which of the following structures open into the second part of duodenum?
a) Cystic duct
b) Hepatic ducts
c) Common bile duct and pancreatic duct
d) Main pancreatic duct only
The common bile duct and main pancreatic duct unite to form the hepatopancreatic ampulla (of Vater), which opens into the second part of duodenum at the major duodenal papilla. This opening is guarded by the sphincter of Oddi, controlling bile and pancreatic secretions.
10) Which structure marks the embryological boundary between foregut and midgut in the duodenum?
a) Ampulla of Vater
b) Ligament of Treitz
c) Pylorus
d) Ileocecal junction
The Ampulla of Vater marks the junction between foregut and midgut in the duodenum. This site divides the arterial supply between the celiac trunk and superior mesenteric artery. It is a key landmark during endoscopic retrograde cholangiopancreatography (ERCP) procedures.
Chapter: Embryology; Topic: Development of Eye; Subtopic: Development of Cornea
Keyword Definitions:
Cornea: The transparent anterior portion of the fibrous coat of the eyeball that helps focus light.
Neural crest cells: Migratory embryonic cells contributing to structures like corneal stroma, endothelium, and sclera.
Surface ectoderm: Gives rise to corneal epithelium, lens, and conjunctival lining.
Mesoderm: Embryonic layer forming muscles, blood vessels, and connective tissues in various organs.
Lead Question – 2014
Stroma of cornea develops from?
a) Neural ectoderm
b) Surface ectoderm
c) Mesoderm
d) Neural crest
Explanation:
The corneal stroma develops primarily from neural crest cells that migrate between the surface ectoderm and lens vesicle. These cells produce collagen fibers and keratocytes that maintain corneal transparency. The surface ectoderm forms the corneal epithelium, while the endothelium and stroma originate from neural crest, not mesodermal sources.
1) The corneal epithelium develops from?
a) Neural ectoderm
b) Surface ectoderm
c) Neural crest
d) Mesoderm
The corneal epithelium is derived from the surface ectoderm. It forms a stratified squamous non-keratinized layer that provides protection and transparency. The surface ectoderm also contributes to the formation of the lens and conjunctival epithelium, highlighting its key role in anterior eye development.
2) Corneal endothelium arises from?
a) Surface ectoderm
b) Neural ectoderm
c) Neural crest
d) Mesoderm
The corneal endothelium is derived from neural crest cells that migrate posteriorly to line the inner corneal surface. It maintains corneal transparency by regulating stromal hydration through ion transport. Any dysfunction of this layer, such as in Fuchs dystrophy, results in corneal edema and visual impairment.
3) Which embryological source gives rise to the sclera?
a) Surface ectoderm
b) Neural crest
c) Neural ectoderm
d) Mesoderm
The sclera develops from neural crest-derived mesenchyme surrounding the optic cup. These cells differentiate into dense connective tissue forming the white outer coat of the eyeball. The sclera provides protection and attachment for extraocular muscles, maintaining the structural integrity of the eye.
4) Which of the following is derived from neural ectoderm?
a) Corneal stroma
b) Lens
c) Retina
d) Corneal epithelium
The retina originates from the neural ectoderm of the optic vesicle. It differentiates into two layers — the outer pigmented and inner sensory layer. Neural ectoderm also gives rise to the optic nerve fibers and part of the iris epithelium, but not to corneal tissues.
5) The corneal transparency is maintained by?
a) Presence of keratin
b) Regular arrangement of collagen
c) High vascularity
d) Thick epithelium
Corneal transparency depends on the regular arrangement of collagen fibrils in the stroma and the dehydrating function of endothelial cells. This precise spacing allows uniform light transmission. The avascular nature of the cornea further prevents light scattering, ensuring optical clarity necessary for vision.
6) A newborn presents with opaque cornea and shallow anterior chamber. Which developmental defect is most likely?
a) Neural crest cell migration failure
b) Incomplete lens vesicle separation
c) Mesodermal hypoplasia
d) Surface ectodermal defect
Failure of neural crest cell migration causes congenital anomalies like Axenfeld-Rieger syndrome and Peters anomaly. These lead to corneal opacity, anterior segment dysgenesis, and glaucoma. Proper neural crest migration is essential for forming corneal stroma, endothelium, trabecular meshwork, and anterior chamber structures.
7) Which condition is associated with defective corneal endothelial pump function?
a) Fuchs endothelial dystrophy
b) Keratoconus
c) Retinitis pigmentosa
d) Marfan syndrome
Fuchs endothelial dystrophy results from progressive degeneration of corneal endothelial cells derived from neural crest. The loss of pump function leads to fluid accumulation and corneal edema, causing blurred vision and morning glare. It is common in older females and may require corneal transplantation.
8) Which part of the developing eye is responsible for inducing corneal formation?
a) Optic vesicle
b) Lens vesicle
c) Surface ectoderm
d) Neural crest
The lens vesicle induces differentiation of the overlying surface ectoderm into corneal epithelium and triggers neural crest migration to form the stroma and endothelium. This inductive interaction is crucial in eye morphogenesis, demonstrating the importance of epithelial-mesenchymal signaling in organ development.
9) Which structure separates the cornea from the iris in adults?
a) Corneal stroma
b) Anterior chamber
c) Aqueous humor
d) Vitreous body
The anterior chamber separates the cornea from the iris. It forms by the resorption of mesenchyme between the developing cornea and iris. Aqueous humor circulates in this space, nourishing avascular corneal and lens tissues and maintaining intraocular pressure.
10) In which embryological week does corneal differentiation begin?
a) 4th week
b) 6th week
c) 7th week
d) 9th week
Corneal differentiation begins around the 6th week of intrauterine life when surface ectoderm interacts with the lens vesicle. Neural crest cells migrate to form the stroma and endothelium. By the 7th week, corneal layers are distinct, and transparency develops later through maturation.
Chapter: Embryology; Topic: Development of Genital System; Subtopic: Development of Female Genital Tract
Keyword Definitions:
Müllerian duct: Also known as the paramesonephric duct; it gives rise to the female reproductive organs such as the uterus, fallopian tubes, and part of the vagina.
Mesonephric duct: Also known as the Wolffian duct; primarily contributes to male genital structures like epididymis and vas deferens.
Genital ridge: The embryonic structure from which gonads develop in both sexes.
Urogenital sinus: The endodermal structure that forms part of the urinary bladder and lower part of the vagina.
Lead Question – 2014
Female genital tract develops from?
a) Mesonephric duct
b) Mesonephric tubules
c) Mullerian duct
d) None
Explanation:
The female genital tract develops from the Müllerian ducts, which form the fallopian tubes, uterus, and upper portion of the vagina. These ducts develop alongside the mesonephric ducts but remain functional only in females. Anti-Müllerian hormone secreted by testes in males causes regression of these ducts, preventing female tract formation.
1) Which structure is derived from the Müllerian duct?
a) Epididymis
b) Vas deferens
c) Fallopian tube
d) Seminal vesicle
The fallopian tubes arise from the cranial unfused parts of the Müllerian ducts. Their epithelial lining originates from the coelomic epithelium. The ducts later fuse caudally to form the uterus and upper vagina, forming the essential pathway for ovum transport and fertilization in females.
2) Failure of fusion of Müllerian ducts results in?
a) Bicornuate uterus
b) Septate uterus
c) Unicornuate uterus
d) Rudimentary uterus
A bicornuate uterus occurs due to incomplete fusion of the Müllerian ducts. It leads to a heart-shaped uterus with two horns, which can cause recurrent abortions or preterm labor. The degree of fusion defect determines the clinical variant—arcuate, didelphys, or septate uterus.
3) The vagina is derived from?
a) Müllerian duct and urogenital sinus
b) Mesonephric duct
c) Cloacal membrane
d) Genital ridge
The vagina is derived from both the Müllerian duct (upper part) and the urogenital sinus (lower part). The sinovaginal bulbs form the vaginal plate, which later canalizes. This dual origin explains certain congenital anomalies like transverse vaginal septum and vaginal agenesis.
4) Which hormone causes regression of Müllerian ducts in males?
a) Testosterone
b) Dihydrotestosterone
c) Anti-Müllerian hormone
d) Estrogen
The Anti-Müllerian hormone (AMH), secreted by Sertoli cells of the testes, causes regression of the Müllerian ducts in males. This hormone prevents the formation of female genital structures. In its absence, Müllerian structures like the uterus and fallopian tubes persist, leading to intersex disorders.
5) Which part of the uterus is formed from the fused Müllerian ducts?
a) Fundus
b) Body and cervix
c) Fallopian tube
d) Vagina
The body and cervix of the uterus develop from the fused caudal parts of the Müllerian ducts. The fusion process also leads to the formation of the uterine cavity. The endometrial lining arises from coelomic epithelium, while the myometrium originates from surrounding mesenchyme.
6) A newborn girl presents with absence of uterus and upper vagina but normal external genitalia. Likely diagnosis?
a) Androgen insensitivity syndrome
b) Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome
c) Turner syndrome
d) Congenital adrenal hyperplasia
In MRKH syndrome, the Müllerian ducts fail to develop, leading to absence of the uterus and upper vagina. Ovarian function and external genitalia remain normal as they are derived from other embryonic sources. It presents with primary amenorrhea and normal secondary sexual characteristics.
7) Persistent Müllerian duct syndrome occurs due to deficiency of?
a) Testosterone
b) DHT
c) AMH or its receptor
d) FSH
Persistent Müllerian duct syndrome results from mutation or deficiency in Anti-Müllerian hormone or its receptor. Males with this defect possess both male external genitalia and internal female structures (uterus, fallopian tubes). Testicular descent may be affected due to mechanical obstruction from persistent Müllerian remnants.
8) Which developmental anomaly leads to double uterus and double vagina?
a) Failure of fusion of Müllerian ducts
b) Failure of septal resorption
c) Unilateral duct agenesis
d) Cloacal persistence
A failure of fusion of Müllerian ducts results in uterus didelphys — a condition with two separate uteri and two vaginal canals. It can be asymptomatic or cause reproductive complications. MRI and ultrasound help in diagnosis, and surgical correction is rarely required unless symptomatic.
9) Which structure connects Müllerian ducts with the urogenital sinus during development?
a) Sinovaginal bulbs
b) Cloacal membrane
c) Genital ridge
d) Mesonephric duct
The sinovaginal bulbs, derived from the urogenital sinus, connect with the fused Müllerian ducts to form the vaginal plate. This structure later canalizes to form the lower vagina. Any developmental arrest here can cause imperforate hymen or vaginal atresia.
10) At which embryological week does the Müllerian duct start developing?
a) 3rd week
b) 5th week
c) 6th week
d) 8th week
The Müllerian ducts begin to develop around the 6th week of intrauterine life as invaginations of the coelomic epithelium. They run parallel to the mesonephric ducts and later fuse to form female internal genital organs. Their proper development is crucial for fertility and normal anatomy.