(1.1) Embryology

Question 1

Briefly describe the origin of Indifferentiated gonads.

Answer 1

• Intermediate Mesoderm -> Urogenital Ridge
• Primordial germ cells migrate: Yolk Sac -> Dorsal Mesentery -> Urogenital Sinus
• Primordial cells cause regression of Mesonephric Tubules and development of Indifferentiated Gonads.

Question 2

What factor determines the gender of Indifferentiated gonads to develop into?

Answer 2

• Presence of SRY gene on Y chromosome -> Testis

- Absence of SRY gene on Y chromosome -> Ovary

Question 3

Briefly describe the development of Indifferentiated gonads in males.

Answer 3

SRY Gene on Y Chromosome -> Testis by:

• Development of Medullary cells
• Regression of Cortical Cortex
• Thick Tunica Albuginea

Question 4

Briefly describe the development of Indifferentiated gonads in females.

Answer 4

No SRY Gene on Y Chromosome -> Ovary by:

• Regression of Medullary cells
• Development of Cortical Cortex
• Thick Germinative Epithelium

Question 5

What is Paramesonephric Duct also known as?

Answer 5

Mullerian Ducts

Question 6

What is Mesonephric Duct also known as?

Answer 6

Wolffian Duct

Question 7

Briefly describe the development of the reproductive ductal system in males.

Answer 7

Testis produce:

• Sertoli cells -> Mullerian Inhibiting Hormone -> regression of Mullerian Duct
• Leydig cells -> Testosterone -> development of Wolffian Duct
• Wolffian Duct and Uretic Bud make separate entry into Urogenital Sinus
• Wolffian Duct -> Semiferous Tubules & Epididymis & Vas deferens & Seminal Vesicles & Prostate Gland

Question 8

Briefly describe the development of the reproductive ductal system in females.

Answer 8

Without Testis:

• Absence of Testosterone -> regression of Wolffian Duct
• Absence of Sertoli cells -> no Mullerian Inhibiting Hormone -> development of Mullerian Duct
• Mullerian Duct -> Fallopian Tube & Uterus & Fornix & Upper Vagina
• Mullerian Duct (Intermediate Mesoderm) fuse with Urogenital Sinus (Endoderm) , which forms the Lower Vagina

Question 9

Describe the germ cell layers of which Vagina develop from.

Answer 9

• Upper: Intermediate Mesoderm -> Mullerian Duct

- Lower: Endoderm -> Urogenital Sinus

Question 10

Briefly describe the development of the External Genitalia in males.

Answer 10

Testis -> Leydig cells -> Testosterone -> Dihydrotestosterone ->

• Genital Tubercle -> Glans of Penis
• Genital Swellings -> fold -> Shaft of Penis
• Genital Folds -> fuse -> Raphe of Penis
• Labioscrotal Folds -> swell -> Scrotum

Question 11

Briefly describe the development of the External Genitalia in females.

Answer 11

Ovary -> no Dihydrotestosterone ->

• Genital Tubercle -> Glans of Clitoris
• Genital Swellings -> Body of Clitoris
• Genital Folds -> Labia Minora
• Labioscrotal Folds -> Labia Majora

Question 12

How do the male gonads move to the correct anatomical positions in adult?

Answer 12

Gubernaculum attaches to Labioscrotal Fold and Testis -> through Inguinal Canal and pulls

• The part of Gubernaculum in Lumbar region -> obliterates -> Spermatic Cord through Inguinal Canal
• The remnant of Gubernaculum -> suspend Testis in Scrotum -> Scrotal Ligament

Question 13

How do the female gonads move to the correct anatomical positions in adult?

Answer 13

Gubernaculum attaches to Labioscrotal Fold and Ovary -> through Inguinal Canal and pulls

• The part of Gubernaculum attaching Uterus to Labia -> Round Ligament through Inguinal Canal
• The part of Gubernaculum attaching Ovary to Uterus -> Ovarian Ligament

Question 14

How do the Paramesonephric duct appear? What is needed to maintain them?

Answer 14

• Invaginations of Urogenital Ridge Epithelium, near the Mesonephric Duct
• Need nothing, they just keep exist

Question 15

What do the Paramesonephric Ducts make contact with cranially and caudally?

Answer 15

• Cranially: open into abdominal cavity

- Caudally: contact with Cloaca (Urogenital Sinus)