Genitourinary System Part 2

Spermatogenesis The production of spermatozoa Produced in the testis:

Seminiferous Tubules Micrograph

Stages of Spermatogenesis

Oogenesis – the production of an ovum

Ovary cross sectional micrograph

Stages of Oogenesis

Gametes Human Sperm – structure

Hormonal Control of Spermatogenesis

Semen Production 3 main structures play a role Epididymis – storage/holding area where sperm mature and become fully motile Seminal vesicle and prostate gland – produce, store and expel fluid during ejaculation –Fluid mixes with sperm to increase volume of ejaculate; s.v. fluid contains nutrients (including fructose) and mucus (protection); –Fluid from p.g. contains mineral ions, and is alkaline (protection)

Human Egg – structure: (n) nucleus; corona radiata; cortical granules; diameter 100um (1/10 th mm)

Spermatogenesis vs. oogenesis Guys Millions daily Released during ejaculation Starts during puberty Production continues throughout adult life Four functional gametes per meiosis Girls 1/28 days Released via ovulation Starts prenatally Stops at menopause 1 functional gamete per meiosis

Fertilization

Stages of Fertilization

Stages of Early embryological Development

Development of the Fetus

Development of Fetus cont’d By 8 weeks of development, bone and tissue start to develop, embryo now referred to as a fetus. Placenta and umbilical cord develop

Development of Fetus: Placenta cont’d Site of nutrient and gas exchange No mixing of maternal and fetal blood

Amniotic Sac and Fluid Support and protection Basis for amniocentesis

Hormonal Control of Pregnancy Estrogen and progesterone – needed to stimulate the development of uterine lining throughout pregnancy. Secreted by corpus luteum (c.l.) for first week following fertilization Following implantation embryo secretes HCG = prevents degeneration of c.l. = continued secretion of est. and progest. C.l. degenerates middle of term, placental cells now produce est. and progest. Until end of pregnancy

Childbirth

Childbirth cont’d End of pregnancy signalled by fall in progesterone level Oxytocin begins being secreted = stimulates smooth muscle (uterus) contraction Positive feedback loop