Embryology

Question 1

What is gastrulation?

Answer 1

Formation of trilaminar disc (ectoderm, endoderm, mesoderm)

Question 2

What are the 3 main groups of the mesoderm?

Answer 2

Paraxial
Intermediate
Lateral plate

Question 3

How are the definitive endoderm and mesoderm formed?

Answer 3

Invaginatino of epiblast cells through primitive streak

Question 4

From what layer is the urogenital system derived?

Answer 4

Immediate mesoderm

Question 5

What are the 3 parts to the urinary system?

Answer 5

Pronephric
Mesonephric
Metanephric

Question 6

What will the metanephric system form?

Answer 6

Kidney

Question 7

In what structure will excretory ducts enter?

Answer 7

Cloaca

Question 8

How will primitive germ cells from the yolk sac enter the immediate mesoderm?

Answer 8

Via migration through the dorsal mesentery

Question 9

What weeks will the PGCs from the yolk sac migrate to the mesoderm?

Answer 9

4-6

Question 10

What is the genital ridge?

Answer 10

Coelomic epithelium proliferation

Question 11

What are the primitive sex chords?

Answer 11

Proliferating epithelium forming somatic supportive cells enveloping the PGCs

Question 12

What are the 2 genital ducts?

Answer 12

Mesonephric (wollfian) = male

Paramesonephric (mullerian) = female

Question 13

Where will the mesonephric and paramesonephric ducts connect?

Answer 13

Posterior wall of urogenital sinus

Question 14

At what time will sexual differentiation occur?

Answer 14

Week 7

Question 15

What determines the male development?

Answer 15

Presence of SRY (short arm of Y chromosome) transcription factor

Question 16

What is the function of SRY?

Answer 16

Formation of sertoli cells

Question 17

What will somatic support cells in the male form?

Answer 17

Sertoli cells

Question 18

What will the primary sex cords in the male form?

Answer 18

Testis which engulf the PGCs

Question 19

What will the rete testis connect?

Answer 19

Mesonephric tubules to testis cords

Question 20

What lies between the coelomic epithelium and the testis cords?

Answer 20

Thickened layer of connective tissue; tunica albuginea

Question 21

What will sertoli cells secrete in terms of male development?

Answer 21

AMH

Gonadal ridge cells to form leydig cells (testosterone)

Question 22

What will testosterone help develop in the male?

Answer 22

Epididymis
Vas deferens
Seminal vesicles
External genitalia

Question 23

What will AMH do in male development?

Answer 23

Degeneration of paramesonephric duct

Question 24

What will persistent mullerian duct syndrome present as?

Answer 24

Uterus, vagina and uterine tubes
Testes in ovarian localtion
Male external genitalia

Question 25

At what level do the testes originate?

Answer 25

T10

Question 26

How are the testes pulled through the abdominal cavity?

Answer 26

Fibrous attachment to the gubernaculum

Question 27

What is undescended testes called?

Answer 27

Cryptorchidism

Question 28

When do the male accessory glands develop?

Answer 28

Week 10

Question 29

What are the male accessory glands?

Answer 29

``` Prostate endoderm invagination) Bulbourethral glands Seminal vesicle (mesonephric duct) ```

Question 30

What will germ cells differentiate into?

Answer 30

Oogonia and then to primary oocytes

Question 31

What will somatic support cells in females differentiate into?

Answer 31

Granulosa cells | Surround primary oocyte

Question 32

What will the female gonad form?

Answer 32

Primordial follicles and theca cells

Question 33

What will the paramesonephric ducts in females form?

Answer 33

Uterine tubes Uterus Superior vagina

Question 34

What are the 3 parts to the paramesonephric duct?

Answer 34

Cranial; opens into the coelomic cavity Horizontal; crosses the mesonephric duct Caudal; fuses with the paramesonephric duct on opposite side

Question 35

What forms the uterovaginal canal?

Answer 35

Fused caudal portion of paramesonephric duct

Question 36

What forms the vaginal lumen and fornices?

Answer 36

Vacuolization of paramesonephric portion of vag and sinuvaginal bulbs

Question 37

When will external genitalia be distinguishable?

Answer 37

Around week 14

Question 38

How is the spongy urethra formed?

Answer 38

Proximal to distal zipping of urethral groove

Question 39

How is the prepuce (foreskin) formed?

Answer 39

Circular ingrowth of ectoderm around the periphery of the glans (week 12)

Question 40

What is hypospadias?

Answer 40

External urethral opening lies in an abnormal position along the ventral aspect of penis