The Testes •Gamete Development (sperm)•Hormonal Production

(testosterone)

Male Reproductive Biology

The Sperm’s Journey

• Spermatids released into lumen of seminiferous tubules

• Move through tubules• Stored in Epididymis

The SPERM

Middle piece

Head

Tail

Enzymes dissolve

egg membrane genetic material

microtubules (cilia and flagella)

Seminal vesicles & Prostate gland: Provide seminal fluid Cowper’s gland: Provide pre-ejaculatory fluid (lubricant)

Erection

•Facilitates penetration•Occurs when sexually aroused (mostly)•Mechanism: artery dilation filling of corpora

VIAGRA: •Not an aphrodisiac •Sildenafil increases levels of cGMP which causes

vasodilation of the corpora•Without sexual arousal, it can not cause an erection

Male Hormonal Functioning

Male hormonal function

HYPOTHALAMUS

PITUITARY

TESTES

GnRH

LH FSH

TESTOSTERONE

FSH -> + spermatogenesis

LH -> + testosterone

testosterone -> - GnRH.

Testosterone• Sperm maturation• development of penis and testes• Male secondary sexual characteristics

– Axillary hair, – larynx, – oil and sweat gland secretion

• Threshold for sexual activity and libido• muscle anabolism

• Risk of prostate cancer

Testosterone and Aggression• Differences in testosterone don’t tell us

about individual differences in levels of aggression

Individuals with more T not more aggressive

Effect of Social cues on hormonal and sexual behavior

The sexually dominant male (bottom) has vivid coloration and special markings.

HYPOTHALAMUS

ANTERIOR PITUITARY

OVARYFollicle

FSH LH

Estrogens

GnRH Follicular phase

(first half of cycle)

Female reproductive biologyMenstrual Cycle

Estrogen effects• increases progesterone receptor density in

breasts

• Initiates proliferative phase in uterus

• Causes changes in cervical mucous

cervix closes soon after ovulation

tangled fibers to line up, allowing sperm to get

through

Copyright © Allyn & Bacon 2004

HYPOTHALAMUS

ANTERIOR PITUITARY

OVARY

Follicle Corpus Luteum

UTERUS

FSH LH

ProgesteroneEstrogens

GnRH

Endometrium, Cervix, Vagina

• P is secreted by the Corpus Luteum after ovulation

• Increased concentration in breast in luteal phase– increases tenderness– increases nipple sensitivity

• Initiates secretory phase of endometrium– Heavy vascularization– Secretion of nutrient rich medium for embryonic growth

• Signals the pituitary to stop producing LH

Progesterone Effects

Secretory Phase of Uterus

• No fertilization– Corpus Luteum regresses after about 12

days– Progesterone products drops off sharply– Endometrium sloughs off (menstruation)

• Fertilization– Corpus luteum remains active– Progesterone levels remain high uterine

lining remains strong– Implantation occurs– hCG from fetus takes over

• In rabbits, the act of coitus stimulates the pituitary gland to release gonadotropin which induces ovulation & increases the probability of pregnancy.

– Organizational effect:• The effect of a hormone on tissue differentiation and

development.

– Activational effect:• The effect of a hormone that occurs in the fully developed

organism; may depend on the organism’s prior exposure to the organizational effects of hormones.

defeminization masculinization

Copyright © Allyn & Bacon 2004

Vomeronasal organ (VNO):, mediates the effects of some pheromones

Lesion to VNO: female rat fails to recognize male as suchBehaves as maleThis suggests bipotentiality of adult female brain (male/female)

Pheromone:A chemical released by one animal that affects the behavior or physiology of another animal; usually smelled or tasted.

– Effects of Pheromones• female animals housed together -> stop estrous cycle• synchronization of estrous cycle by pheromone in a

male’s urine.• female animals housed with males -> early onset of

puberty • Termination of pregnancy when new male other than the

one that impregnated the female.