MedPhys Unit 4: Male Reproductive System

What gene encodes for testis determining factor (TDF)?

SRY

What does the secretion of AMH do?

Blocks the formation of the mullerian duct (female reproductive duct)

Androgen dependent events include

T secretion

Wolfian duct develop

5a DHT

Reproductive axis

Hypothalamus

Ant. Pit

Testes

What does the hypothalamus secrete?

GnRH

What does the anterior pituitary secrete?

Gonadotropins (FSH and LH)

LH function

Hormone production (Testosterone)

FSH hormone

Sperm production

Testes release

Hormones

Sperm

Spermatogenesis

300-400 mil everyday

25-250 mil in ejaculate

1.5-5.0 mL of semen

Parts of the sperm

Acrosome

Head*

Mid piece

Tail

Acrosome

Bag of enzymes to penetrate egg

Head

DNA

Only part that actually enters egg

Midpiece

Mitochondria for ATP production

Tail

Flagella for motility

How does testosterone travel in the blood?

Bound to proteins like...

B-globulin

Albumin

Others

How is testosterone inactivated?

In the liver by conjugation w/andorsterone and etiocholonone

Role of testes in fetus

Internal Urogenital system

External gen

Brain differentiation

When do leydig cells become active ?

By gonadotropins LH+FSH

Average puberty age male

14 years

When pubarche occurs (appearance of pubic/axillary hair?

Adrenarche age

8 years

Secretion of androgens

Increased growth in puberty due to?

GH

IGF

What is inhibin

Produced by Sertoli cells inhibiting FSH

Inhibin subunits

Alpha

Beta A

Beta B

Increased serum testosterone inhibits ?

FSH and LH

By release of inhibin by Sertoli cells

FSH mechanism of action

FSH bind to sertoli

CAMP production

Protein kinase activated

ABP synthesis

ABP to seminiferous tubule lumen

LH mechanism of action

LH bind to Leydigs

CAMP production

T secreted

T binds to ABP

ABP brings T to epididymis

LH and FSH summary

FSH makes ABP

LH makes T that binds to ABP

ABP takes T to epididymis for sperm maturation

Male pseudohermaphroditism

Have testes but underdeveloped external genitalia

Female pseudohermaphroditism

Have ovaries but enlarged external genitalia appearing masculine

Guevodoces

Lack of 5-a-reductase

Cannot convert T to DHT

Testicular feminization syndrome

Androgen insensitivity due to receptor defect

Testicular feminization characteristics

XY chromosomes...appear female

Wolffian/Mullerian ducts fail to differentiate

Testosterone at puberty

Accessory glands produce semen

Sebacous gland activity

Hair growth

Pubic pigment

PCT in kidney differ

As T levels decline in aging men...

Muscle mass

Bone density

Energy

Libido

...all decline

Estrogen in males

Fluid regulation

Environmental E can decrease sperm

Bone growth/plate closure

HDL levels

Antiandrogen effects

Decrease libido

Reverse acne/baldness

Treats hircitism in females

Cyproterone acetate is a...

Potent antiandrogen

Precocious puberty

Early develop of secondary sex characters

Mutation in LH receptor or GPCR

Constant gonadotropin secretion

Hypogonadism results from...

Defect in...

GnRH

LH

FSH

Hypergonadism results from...

Tumors that secrete androgens

Tumors that secrete estrogens (feminization)

Receptor (-) androgen insensitivity

Receptor mutation = hormone cant bind

Receptor (+) androgen insensitivity

T can bind to R

TR complex cant bind DNA

Gynecomastia

Decreased T/E2 or increased E2/T

Prol producing tumor

Adult leydig cell tumor

Result of mumphs

Decreased T

Similar effect to menopause

Benign Prostatic Hyperplasia

DHT buildup in prostate

Carcinoma

80% are androgen-dependent

Medicinal castration and given GnRH or 5-a-reductase inhibitors

Impotence (erectile dysfunction)

Relaxation of smooth muscle that produces erection

How does viagra treat impotence?

Blocks PDE5

Cannabanoid effects

Decrease T and Sperm

Atrophy of internal teste structures

Alcohol abuse

Leydig cell failure (LH)

Increase E2:T ratio

Sexual response

Erection via PSNS

Emission via SNS

Ejaculation via SNS