The Harvard Medical School Guide to Men’s Health

Harvey B. Simon,M.D.

Chapter 144 autosomes (22 pairs)

2 sex chromosomes

( 1 pair, XX or XY)DNA in these 46

chromosomes has 30,000 genes

with genetic information

Y chromosome small

40 genes

SRY gene makes the man

“sex –determined region y”

SRY 1) MIS 2) T during fetal development

Gnrh ( hypothalamus)

FSH and LH (pituitary)

LH goes to testicle and makes “T” which with FSH initiates sperm production

In Testicle, Leydig cells use cholesterol

androstenedione T

T secondary sex characteristics

RBCs

Behavior Sexual function

Primary characteristics High LDL Low HDL

T DHT prostate, skin, scalp,

body hair follicles ….

T production

Testicles 95% of T

Adrenals 5% T –independent of FSH or LH and precursor is DHEA

T finally Estradiol in fat cells.

T in Life Cycle

Week 7 in embryo

Rest of embryo life

3-6 months of age

6-8 years ( adrenal androgens)

Puberty, Gnrh LH T till 16 years old

Decline after 40 at 1% per year

Reproductive Cells in testicles

Leydig cells Make T

Germ cells Make sperm

Sertoli cells Nurture sperm

Movin ‘em out!

Sperm cells within 2 months

epididymis within 2 weeks to vas

deferens ampulla ejaculatory duct.

Sperm fluid(10%) gets joined by fluid from prostate (20%) and seminal fluid(70%).

Semen = 10% +20%+70%.

Sexual Arousal

Erotic (CNS) sensory

( autonomic nerves)

Nerves Penile artery widening

Vein compression erection

Ejaculation

Under control of autonomic nervous system:

Fluids move into ejaculatory ductMuscles at bladder neck contractPelvis, prostate and penis muscular

contractions ejaculationPenile arteries recontract flacidity