29. Cloaca, Uterus, External Genitalia

Question 1

Where do germ cells originate from?

Answer 1

Epiblast

Migrate through primitive streak and develop in the wall of the yolk sac

Question 2

Where do the indifferent gonads develop?

Answer 2

Urogenital ridge

Question 3

Where do the germ cells migrate in weeks 5-6?

Answer 3

To the urogenital ridge

Later migrate into primitive sex cords

Question 4

What is the urogenital ridge covered by?

Answer 4

Epithelial cells of mesodermal origin

-proliferate into a thick layer to form the primitive sex cords

Question 5

What causes sex determination?

Answer 5

Short arm of Y chromosome contains sex determining region

Produce Testis determining factor or SRY

Question 6

What influence does the Y chromosome have on the developing foetus?

Answer 6

Testis develop
Medullary cords develop
No cortical cords
Thick tunica albuginea

Question 7

What is the function of the tunica albuginea?

Answer 7

Prevents blood leaving the penis during an erection

Question 8

What effect does the lack of a Y chromosome have on the foetus?

Answer 8

Ovaries develop
Medullary cords degenerate
Cortical cords develop
No tunica albuginea

Question 9

What do the primitive sex cords become in the male?

Answer 9

Testis cords

Question 10

What happens to the male gonads at 8 weeks?

Answer 10

Testis cords separate from the tunica albuginea

Connections between the testis cords and mesonephric tubules are now the rete testis cords

Question 11

What happens to the male gonads at 4 months?

Answer 11

Testis cords form loops
Germ cells inside communicate with sertoli cells
Rete testis cords connect with the mesonephric tubules

Question 12

What does the connection between the rete testis cords and mesonephric tubules become at puberty?

Answer 12

Seminiferous tubules

Question 13

What are the effects of hormones on the male gonads at 4 months?

Answer 13

Testosterone is produced by Leydig cells
-Stimulates mesonephric duct

Mullerian inhibiting substance by Sertoli cells
-paramesonephric ducts degenerate

Question 14

What does the mesonephric duct become in the male?

Answer 14

Epididymis

Ductus deferens

Question 15

What does the paramesonephric duct become in the male?

Answer 15

Appendix testis

Prostatic utricle

Question 16

What happens to the mesonephric duct in both males and females?

Answer 16

Enters cloaca
Ureteric buds form off sides
Becomes incorporated into the bladder as the trigone

Question 17

Where does the gubernaculum originate from?

Answer 17

Mesoderm

Question 18

What is the function of the gubernaculum?

Answer 18

Pulls gonads down to pelvis

Question 19

What path do the testis take in their descent?

Answer 19

Through inguinal canal to scrotum

Question 20

What is the tunica vaginalis a remnant of?

Answer 20

Processus vaginalis

Question 21

What is cryptorchidis?

Answer 21

Undescended testes by 3 months

Question 22

What is the name of the surgical removal of an undescended testis?

Answer 22

Orchidopexy

Question 23

What happens to the female gonads at 7 weeks?

Answer 23

Primitive sex cords degenerate

Overlying epithelium proliferates to form cortical cords

Question 24

What happens to the female gonads at 4 months?

Answer 24

Cortical cords separate from overlying epithelium

Form follicular cells surrounding oogonia

Question 25

What does the paramesonephric duct become in females?

Answer 25

Fallopian tubes Uterus Cervix and upper vagina

Question 26

What does the mesonephric duct become in females?

Answer 26

Gartner's cyst | Broad ligament

Question 27

What does the gubernaculum remain as in females?

Answer 27

Ovarian and round ligaments

Question 28

What does the cloaca divide into?

Answer 28

Urogenital sinus | Hingut

Question 29

What does the urachas become once it closes off at the umbilicus?

Answer 29

Median ligament

Question 30

What do the external genitalia of both males and females arise from?

Answer 30

Genital tubercle

Question 31

What do the cloacal folds and membrane become?

Answer 31

Anal folds and membrane | Urethral folds and membrane

Question 32

What happens to the female external genitalia after the indifferent stage?

Answer 32

Genital tubercle regresses and bends inferiorly to form the clitoris Phallic segment of urogenital sinus forms vestibule of vagina Urethral folds form the labia minora Genital swellings form labia majora

Question 33

What is formed when the uterine canal connects to the posterior urogenital sinus in the female?

Answer 33

Sinovaginal bulbs

Question 34

What do the sinovaginal bulbs become?

Answer 34

Vagina

Question 35

What is the hymen formed from?

Answer 35

Proliferation of the sinovaginal bulbs

Question 36

What is haematocolpos?

Answer 36

Hymen doesn't perforate | Menstrual blood is retained within the vagina

Question 37

What do the genital swellings form in the male foetus?

Answer 37

Fuse to form a single scrotum

Question 38

What happens to the male external genitalia after the indifferent stage?

Answer 38

Phallus elongates Urethral folds zip together in midline to enclose penile urethra Epithelium invaginates into glans to form external meatus

Question 39

Name 3 forms of intersex states?

Answer 39

5-a-reductase deficiency Klinefelter Syndrome Gonadal dysgenesis

Question 40

What does a 5-a-reductase deficiency result in?

Answer 40

Ambiguous genitalia in males

Question 41

What does klinefelter syndrome result in?

Answer 41

Decreased fertility Small testes Decreased testosterone Gynecomastia

Question 42

What is gonadal dysgenesis?

Answer 42

Failed or incomplete gonadal development | Germ cell deficiency

Question 43

What is XY Female gonadal dysgenesis?

Answer 43

Point mutation or deletion of SRY gene | Appear as normal females but no menstruation or secondary sex characteristics

Question 44

What are the symptoms of Turner Syndrome?

Answer 44

``` Short stature High-arched palate Webbed neck Shield-like chest Cardiac and renal anomalies Inverted nipples ```