Lecture 16: Male Reproductive System

SRY gene

gene that produces the sex determining Y protein, master regulatory gene for masculinization, acts as transcription factor

Undifferentiated structures

genital tubercle, genital fold, genital swelling

female external development

clitoris, labia minora (urethral orifice and vaginal opening), labia majora

male external development

glans penis, shaft of penis, scrotum

Female internal reproductive development

wolffian ducts degrade, mullerian ducts form uterine tubes and uterus

Male internal reproductive development

Mullerian ducts degrade, Wolffian ducts form epididymis and vas deferens

Swyer syndrome

XY individual with a mutated dysfunctional SRY gene, causes external female traits but undeveloped internal sex organs. No menstruation, no breast development.

Aromatase inhibitor

drug that inhibits conversion of testosterone to estrogen, reduces side effects of testosterone use (so u don’t get forcibly feminized)

Functions of the male reproductive system

produce androgens and sex hormones, spermatogenesis 100-300 mil daily, sperm delivery via sexual intercourse

Testis anatomy

tunica albuginea outer layer, seminiferous tubules looping inside

Sertoli cells

support and protect germ cells, and form blood-testis barrier, aka nurse cells

Epididymis

area adjacent to testes where sperm mature and grow flagella

Vas deferens

tube that carries sperm to the penis

Seminal gland

Gland that produces light yellow alkaline secretion containing fructose and citric acid, provides nourishment for sperm. Also releases prostaglandins for motility

Prostate gland

Gland that produces milky, acidic fluid secretion containing citric acid and PSA

PSA

antigen used to test for prostate cancer

Bulbo-urethral gland

gland that produces clear, alkaline mucus that lubricates the tip of penis for copulation and neutralizes traces of acidic urine in the urethra prior to ejaculation

Sperm Structure

head contains DNA, midpiece contains mitochondria, tail provides motility

Testosterone

primary male hormone responsible for regulating sex differentiation, characteristics, spermatogenesis, and fertility

leydig cells

cells that produce testosterone, located outside seminiferous tubules, 6-7 mg daily

Effects of testosterone

Increase libido, sperm production, voice change, increased, penile development, secondary phenotypic characteristics, bone strength, muscle mass, body hair

Organs besides testes that produce testosterone in small amounts

Ovaries (become estradiol) and adrenal glands

Regulation pathway of testosterone production

GnRH → FSH + LH → stimulate leydig, sertoli release ABP to stabilize, inhibin and testosterone start negative feedback loop to stop overproduction