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HUMAN REPRODUCTION BIOLOGY 269

HUMAN REPRODUCTION BIOLOGY 269. Recall:. Male Reproductive System: 1) Produce testosterone for sexual characteristics Produce large numbers of sperm & store them until ejaculation Produce fluids to add to semen Sexual intercourse; ejaculate semen high into vagina. Female Reproductive System

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HUMAN REPRODUCTION BIOLOGY 269

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  1. HUMAN REPRODUCTIONBIOLOGY 269

  2. Recall: • Male Reproductive System: • 1) Produce testosterone for sexual characteristics • Produce large numbers of sperm & store them until ejaculation • Produce fluids to add to semen • Sexual intercourse; ejaculate semen high into vagina Female Reproductive System • Produce estrogen and progesterone for sexual characteristics • Produce and release one large oocyte at regular intervals • Sexual intercourse, receive semen • Produce hormones to prepare endometrium for pregnancy each cycle; shed functional layer by menstruation • Protect/nourish embryo/fetus; expel it during childbirth • Produce milk to nourish newborn

  3. Testis: Approximately 4cm x 2 cm x 2 cm Outside body cavity in scrotum Divided into + 20 compartments; Each compartment contains a long, coiled seminiferous tubule Seminiferous tubules are site of spermatogenesis

  4. Hundreds of millions of sperm produced per day Entire process takes about sixty days

  5. Spermatogenesis is initiated and stimulated by follicle stimulating hormone (FSH) secreted by the pituitary gland FSH is the same hormone that stimulates oogenesis in the ovary. However, secretion of FSH in women rises and falls each cycle, resulting in the production of just one oocyte; Secretion of FSH in men remains relatively steady so spermatogenesis is continuously stimulated and sperm are continuously produced.

  6. The pituitary gland also secretes luteinizing hormone (LH) in male. LH stimulates formation of the corpus luteum and production of progesterone in the ovary. In the testicle, LH stimulates the production of testosterone by interstitial cells, which are located between the seminiferous tubules

  7. Unlike oogenesis, in which the developing oocyte is surrounded and protected by a follicle, sperm are not produced within follicles However: developing sperm are protected and supported by a special cell called a sustentacular or Sertoli cell.

  8. Sperm leaving the testis next enter a long (>6 meters) coiled tube called the epididymis. Also located in scrotum, behind the testis Sperm take about 40 days to pass through the epididymis, maturing and becoming fertile

  9. From the epididymis, sperm enter the vas deferens or ductus deferens which passes upward into the abdominal cavity

  10. As it passes from the scrotum to the abdominal cavity, the vas deferens is accompanied by the artery, veins, and nerves supplying the testis.All of these are surrounded by a thick covering of connective tissue, and the entire structure is called the spermatic cord

  11. The spermatic cord passes through a tunnel called the inguinal canal

  12. Within the abdomen, the vas deferens on each side curves backward, then downward and forward, along the side of the bladder. The end of the vas deferens, called its ampulla, is enlarged. This is where sperm are stored until ejaculation.

  13. Male Accessory Glands: Seminal Vesicles: Paired, posterior to bladder. Ducts join vas deferens to form ejaculatory duct. Produce + 60% of semen volume. Contains nutrients for sperm. Contains chemicals to decrease viscosity of cervical mucous, and to stimulate peristalsis of cervix

  14. Male Accessory Glands: Prostate: Inferior to bladder, ejaculatory ducts embedded within it. Surrounds proximal part of urethra as it leaves the bladder Produces + 30% of semen volume. Contains chemicals to: - Neutralize acidity of vagina; - Increase sperm motility; - Cause semen to clot, then liquify.

  15. During ejaculation: a) Sperm from the vas deferens b) Fluid from the seminal vesicles c) Fluid from the prostateAll enter the urethra as it passes through the prostate The urethra then passes through the penis to its tip.

  16. Penis: Root: Embedded in perineum; + 50% of total length Body or shaft: Outside, covered with skin Glans: Tip, not covered with skin

  17. Penis: Three erectile bodies: - Two corpora cavernosa - One corpus spongiosum Fill with blood during erection, causing shaft to line up with root of penis When blood leaves erectile bodies, shaft of penis droops down into normal position

  18. Semen: Mixture of sperm, seminal vesicle fluid, prostate fluid Normal ejaculate: 4 – 6 milliliters 50-100 million sperm per milliliter Alkaline to neutralize acidity of vagina Contains nutrients for sperm, chemicals to decrease viscosity of cervical mucous and to stimulate peristalsis of cervix Semen clots immediately after ejaculation to hold it in vagina, then liquifies gradually over 5 to 10 minutes to release sperm X

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