|
Summers | end |
IX. Sexual Differentiation back to VIII. Adult Male A. Chromosomes 1. Autosomes a. 22 homologous pair b. control general somatic function 2. Sex chromosomes a. 1 pair, may be dissimilar, but not all vertebrates have sex chromosomes i. turtles, crocodilians + some lizards have temperature dependent sex determination b. X and Y in mammals
| mammals | birds, amphibians, some fish | |||||
| i. | XX | ZW | = | |
= | female |
| ii. | XY | ZZ | = | |
= | male |
B. Gonads
1. Indifferent Stage = Weeks 5-7 of development (in humans)
a. Mesonephric Kidney
i. Mesonephric duct = Wolffian Duct
ii. Paramesonephric duct = Mullerian Duct
b. Genital Ridge
i. epithelium
ii. stroma
c. 4th week (human)
i. Primordial Germ Cells arrive from Yolk Sac
(1) into the genital ridge
(2) ~100 start in yolk sac
(3) ~850 arrive at genital ridge
(a) mitosis
ii. Rete Chords grow into gonad
2. Male
a. Week 7-10 differentiation into Testes
i. Rete Cords
ii. Medullary Cords
b. Week 16-17 (human)
i. Wolffian Duct becomes:
(1) Ductus Epididymis
(2) Vas Deferens
(a) Ejaculatory Duct
(3) Seminal Vesicle
ii. Vasa Efferentia
iii. Rete Testis
iv. Seminiferous Tubule
(1) Spermatogonia
(2) Sertoli Cells
v. Mullerian Duct degenerates
(1) a small piece remains in the prostate
(a) Prostatic Utricle
3. Female
a. Cortical Cords
b. Oogonia
c. Primary Oocyte
d. Mullerian Duct becomes:
i. Fallopian Tubes
ii. Uterus
iii. Cervix
iv. upper 1/3 Vagina
e. Paired Mullerian development
i. fusion
(1) different degree of fusion is represented
in different vertebrate forms
C. Regulation of gonadal sex
1. when sex chromosomes are present,
heterozygous sex chromosomes determine sex
a. via production of regulatory sex determining factors
i. i.e. without biochemical intervention the sex
associated with homozygous sex chromosomes occurs
2. TDF testis determining factor
a. coded for by a gene: SRY
i. Sex determining Region
of the 1A1 on the short arm of the
Y chromosome
b. indifferent gonad becomes testis in the presence of TDF
3. Mullerian Duct Inhibiting Factor (MDIF, MDI, MDIH, MDIS)
a. glycoprotein secreted by Sertoli cells
b. inhibits development of
Mullerian duct-derived structures
c. Anti-cancer agent for cancers
of the Mullerian duct and Ovarian cancer
i. ovarian surface epithelium is homologous
to Mullerian epithelium
ii. includes prostate cancer - prostatic utricle
D. External Genitalia
1. Indifferent 5-7 weeks
a. Genital Tubercle (phallus)
b. Labio-Scrotal Swelling
c. Urogenital Fold
d. Urethral Groove
2. differentiated gonads are necessary for differentiation of external genetalia
| 3. Female 8-10 weeks | 4. Male 7-10 weeks | a. Clitoris from genital tubercle | = | a. Glans Penis |
| b. Labia Majora | = | b. Scrotum |
| i. scrotal raphe | ||
| c. Labia Minora | = | c. Corpus Spongiosum |
| i. penile raphe | ||
| d. Vestibule | = | urogenital sinus |
| e. Vaginal Introitus |
E. Hormones & Factors Necessary for Development
| MALE | INDIFFERENT | FEMALE | ||
| Testis | TDF | Gonad | none | Ovary |
| Vasa Efferentia | T | Mesonephric Tubules | No functional structure Rete Ovari |
|
| Ductus Epididymis Vas Deferens Ejaculatory Duct Seminal Vesicles |
T | Wolffian Ducts (Mesonephric Ducts) |
No functional structure | |
| No functional structure | MDIF | Mullerian Ducts | Fallopian Tube Uterus Cervix Upper 1/3 Vagina |
|
| Glans Penis Corpora Cavernosa of the Penis |
DHT | Genital Tubercle | Glans Corpora Cavernosa of the Clitoris |
|
| Corpus Spongiosum of the Penis |
DHT | Urogenital Folds | Labia Minora | |
| Scrotum | DHT | Labio-Scrotal Swelling | Labia Majora | |
| Prostate Gland Bulbourethral Gland |
DHT | Urethral Tissue | Lesser Vestibular (Skenes) Gland Greater Vestibular (Bartholins) Gland |
1. Structures dependent on DHT convert T intracellularly 2. Development of Female structures does not require hormone intervention F. Intersex 1. ambiguous reproductive tract 2. True Hermaphrodite a. combination gonadal type i. ovotestes ii. 1 ovary and one testis = gynandromorph 3. Pseudohermaphrodite a. gonads normal for that sex i. xx=ovary, xy=testis b. ducts or external genitalia may be of the opposite sex c. Testicular Feminization Syndrome i. genetic defect - no androgen receptors (1) for T or DHT ii. normal testis formed, no testicular descent (1) i.e. cryptorchid testes iii. MDIF causes degeneration of Mullerian Duct iv. no Wolffian Duct Development v. female external genetalia d. Guevedoces i. genetic inability to make 5a-reductase ii. normal testis formed, no testicular descent iii. normal T levels, Leydig cells remain normal iv. normal Wolffian Duct development v. female external genetalia and prostate (lesser vestibular) vi. at puberty high [T + weak androgens] bind A-R (1) voice lowers (2) clitoris becomes penis, scrotum fuses, descent of testes (3) prostate and masculine hair remain undeveloped e. Adrenogenital Syndrome (Congenital Adrenal Hyperplasia) i. genetic inability to convert to cortisol in XX ii. very high ACTH levels iii. high androgens from adrenal iv. ducts remain the same, happens after duct differentiation v. masculinization (1) hirsutism (2) clitoral growth (3) growth of labia majora
| Top |