Reproductive System & Human Development

Male Reproductive System What do you already know?

Male Reproductive System

Male reproductive system functions Testes – Produce sperm in a process called spermatogenesis Produce testosterone Sperm are produced from puberty until the end of life, but fertility and sperm quality do decline with age. Schizophrenia, autism, preterm birth and certain birth defects increase in dads over 35. Testosterone Causes development of reproductive organs and secondary sexual characteristics (increased hair growth, thickening of bones, deepening of bones, and enlargement of muscles) Responsible for sex drive Supports sperm formation

Male reproductive system functions epididymis – Storage and final site of maturation for sperm Contracts during ejaculation to push sperm into ductus deferens Ductus deferens carries sperm to ejaculatory duct. The ejaculatory duct then joins the urethra. Fun fact: Vasectomy involves severing the ductus deferens (aka vas deferens) so that sperm cannot be carried to the urethra, rendering a man infertile.

Accessory glands & semen The accessory glands (seminal vesicles, prostate, and bulbourethal gland) produce most of the fluid that makes up semen. Seminal vesicles – produce fluid that nourishes and activates sperm Prostate – produces fluid that activates sperm Bulbourethal gland – produces fluid before ejaculation that reduces acidity of urethra and acts as lubricant for sexual intercourse Fun fact: The prostate becomes enlarged in most men with age, making urination more difficult. Prostate cancer second most common cancer in men (after skin), affecting 1 in 7 men. Sperm activation – increase in motility Bulbourethal gland secretion

External genitalia The scrotum contains the testes and helps maintain optimal temperatures for sperm production by hanging loosely (at high temps) or wrinkling up (at low temps). Erection occurs when the erectile tissue of the penis fills with blood, making the penis larger and rigid. Fun fact: Atherosclerosis is the #1 cause of ED Sperm activation – increase in motility Bulbourethal gland secretion

Female Reproductive System What do you already know? Sperm activation – increase in motility Bulbourethal gland secretion

Female Reproductive System Sperm activation – increase in motility Bulbourethal gland secretion

Female Reproductive System Functions Ovaries Produce oocytes (eggs) Produces estrogens develop female sexual characteristics Establish menstrual cycle and supports growth of endometrium Produces progesterone Establishes menstrual cycle Supports pregnancy and milk production Fun Fact: A woman is born with all the oocytes she will ever have, all paused at an early stage of development. Starting at puberty, several oocytes finish developing every month, with the ‘best’ of these rupturing through the ovary wall during ovulation An ultrasound of an ovary showing 4(?) developing follicles

Female Reproductive System Functions Uterine (Fallopian) tubes Beating of cilia within tubes carries the egg from the ovary to the uterus Not attached to ovary. Egg is pulled into uterine tubes by waving of fimbriae (hair-like projections of uterine tubes that partially surround ovary. Normal site of fertilization. Watch me! The egg is only viable for ~24 hours after ovulation, but it takes 3-4 days for it to reach the uterus.

Female Reproductive System Functions Uterus Receives & nourishes fertilized eggs to support pregnancy Normally size of pear Endometrium is inner lining. This builds up every month in order to allow implantation of fertilized egg, but sloughs off (menstruation) if zygote does not successfully implant and grow. Myometrium is muscular wall. Cervix is the opening; prevents premature birth. Opens fully to 10 cm diameter during earliest stages of labor.

Menstrual Cycle Day 0 is first day of menses Normal cycle varies from 22-34 days No matter what cycle length, ovulation occurs ~14 days prior to menstruation Watch me!

Questions??

Pregnancy and Embryonic Development NOVA show (~50 min) Baby center short clips