GENITAL EMBRYOLOGY.pdf

7/26/2019 GENITAL EMBRYOLOGY.pdf

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DEVELOPMENTS OF GONADS

1. It starts at 6-7 weeks and is completed by 12-13 weeks

2. The intermediate mesoderm along the dorsal body wall

makes a longitudinal elevation urogenital ridge

3. Proliferation of the mesoderm of the urogenital ridge+ coelomic epithelium gonadal ridge

4. The primordial germ cells (XY/XX) in the wall of the yolk sac (endoderm)

migrate to the gonadal ridge primary sex cords


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DEVELOPMENT OF TESTIS DEVELOPMENT OF OV RY

1. The primary sex cords extend into the medulla of the gonads and loose their

connection with the surface epithelium of the gonads as the thick tunica albuginea

forms ------- medullary cords

2. Under the effect of TDF, the medullary cords ------ semineferous cords, tubuli

recti, and rete testes

3. The seminiferous cords canalize at puberty ------ seminiferous tubulesthat

consist of spermatogoniaand Sertoli cells

4. The mesoderm between the seminiferous cordsform the interstitial cells of

Leydig

1. The primary sex cords form rete ovarii then degenerate and replaced by

CT & blood vesselsto form the medulla of the ovary

2. Proliferation of the coelomic epithelium 2ry sex cords

3. The 2ry sex cords enclose the primordial germ cells which break apart to

form isolated cell clusters = primordial follicles (consists of 1ry oocytes

surrounded by a layer of follicular cells).

4. the ovaries develop in the abdomen then descend to the pelvis due to:

- disproportionate growth of the abdomen from the pelvis.

- the gubernaculum.

Anomalies of the testes:

1- Testicular hypoplasia = small testis (in Klinefelter syndrome).

2- Undescended testes = cryptorchidism.

3- Ectopic testes: present at abnormal site as pubis, perineum, femoral triangle.

4- Congenital inguinal hernia = due to patent processes vaginalis.

5- Hydrocoele + enclosed scrotal cyst.

Abnormalities:

1- Ovarian hypoplasia (in Turner syndrome).

2- Ectopic ovary: the ovary may be found in the inguinal canal or in the

labia majora


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Descent of the testis

The testis originally develops in the abdomen then it descends to the scrotum under the effect of:

1- Increased intra-abdominal pressure.

2- Relative growth of the abdomen away of the pelvis.

3- The gubernaculums (a fibromuscular band stretched between the lower pole of the testis and the scrotum.

4-Testosterone hormone.

Levels of the testis:

4th month iliac fossa

7th month . Inguinal canal

8th month . External inguinal ring

9th months scrotum


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Male duct system Female duct system

1. Sertoli cells secrete Mullerian inhibitory factor

- under the effect of MIFparamesonephric ducts (Mullerian ducts) which

are invaginations of the lateral surface of the urogenital ridge regress

completely

- vestigial remnant may persist

appendix testis

prostatic utricle

2. Interstitial cells of Leydig secrete testosterone

- under the effect of testosteronemesonephric ducts (Wolffian ducts)

differentiate into :

a. efferent ductules (vasa efferentia

b. epididymis

c. vas deference

d. seminal vesiclee. ejaculatory duct

3- Serial endodermalbuds located off the urethraforming the prostate

1. In the absence of Sertoli cells & MIF Mullerian duct persists

- upper part of the paramesonephric(Mullerian) ducts give Fallopian tubes

- lower parts fuse in the midlineuterovaginal primordiumwhich develops into

uterus, cervixand upper 3/5 of the vagina

- uterovaginal primordium projects into the dorsal wall of the urogenital sinus

to form sinovaginal bulbsthat fuseto form solid vaginal plate

- solid vaginal plate canalizesto give the lower 2/5 of the vaginaending with a

thin perforated plate called hymen

2. In the absence of Leydig cells & testosteroneWolffian ducts regress

completely leaving vestigial remnants (epoophron, paroophoron, Gartners duct)

.

Mesodermal origin :

- efferent ductules (vasa efferentia)

- epididymis

- vas deference

- seminal vesicle

- ejaculatory duct

Endodermal origin

- prostate

- sperm (primordial germ

cell from the yolk sac)


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Congenital anomalies of the female ducts

1- Abnormalities due to non-fusion of the Mullarian duct:

- Double uterus with double vagina,

- Double uterus with single vagina,

- Bipartite uterus = uterine septum,

- Arcuate uterus = small indentation of the fundus.

2- Anomalies due to atresia (non canalization) of the Mullarian ducts:

- rudimentry horn of the uterus.

- atresia of the cervix.

- atresia aof the vagina.

3- Imperforate hymen.

4- Wide elastic hymen (single wide opening surrounded by elastic tissue).


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Male External genitalia Female External Genitalia:

- develops at 9-13 weeks.

- mesoderm around the cloacal membrane proliferates and rises the overlying

ectoderm to form 3 structures:

1- Genital tubercle which elongates (under the effect of dihydrotestosterone)

.. corpora cavernosa + glans penis

2- Urethral folds which will fuse . Penile urethra

3- Genital swellings which fuse . scrotum

In the absence of DHT

1- The genital tubercle ------------- Clitoris

2- The genital swellings ------------ Labia majora

3- The urethral folds ---------------- Labia minora

Anomalies of the male external genitalia

1- Small phallus (micro-penis)

2- Bifid scrotum (non-fused scrotal folds)

3- Hypospadius = urethra opens ventrally

on the penis.

4- Epispadius = urethra opens dorsallyon the penis

( associated with Ectopia vesica)

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GENITAL EMBRYOLOGY.pdf