The Continuity of Life:

1. The Continuity of Life: Reproduction  Chapter 46 Campbell & Reece

2. Sexual reproduction • Involves 2 events: Meiosis + Fertilization • Meiosis produces Haploid (1/2 Chromosomes) Gametes, specialized for: • 1) Motility (sperm) • 2) Nutrient storage (eggs) • Fertilization unites haploid gametes from two individuals • Restores diploid in offspring • New combinations of genes in offspring = unique

3. The Male Reproductive System • Testes: sperm and testosterone production • Epididymus: sperm maturation (~18 hrs.); motility • Vas Deferens: storage, Leads sperm from scrotum into abdominal cavity, thru glands, and around bladder • Glands: add seminal fluids • Cowper's Gland • Prostate- add fructose (carbohydrate) • Seminal vesicles- add alkaline fluids (semen) • Urethra • Penis • bulbourethral glands-lubricants

4. In the Testes: • Spermatogenesis • each testis is divided into about 250 compartments, each packed with coiled seminiferous tubules which produce the sperm cells. Interstitial cells (between the tubules secrete testosterone) • Semeniferous tubules contain 2 types of cells: • 1) Spermatogenic (sperm-producing) cells: • 2) Sertoli cells (nourish & support developing cells)

5. 1st stage: "spermatogonia" (diploid): proliferate continuously by mitosis--> some differentiate into --> 2nd stage: "Primary Spermatocytes" • => 1st meiotic division (Now Haploid) • 3rd stage: "secondary spermatocytes" • => 2nd meiotic division • 4th stage: "spermatids“, mature into"spermatozoa" (sperm cell)

6. Sperm diagram • Tail • Neck • Head • axial filament • Mitochondria (in sheath) • Nucleus • Acrosome (contains enzymes to penetrate egge membrane) • Axial filament contains 9+2 array of microtubules (typical of cilia and flagella)

7. Ejaculation • a. Erection of the Penis • erectile tissues: • 2 Corpus Cavernosa • 1 Corpus Spongiosum • fill with blood • b. Ejaculation • Mechanoreceptor stimulation causes reflexive nerve arc to smooth muscles which propels semen thru tract, up vas deferens, into urethra. • 3-4 ml per ejaculation; only 10% is actually sperm cells (300-400 billion)

8. The Role of Hormones in the Male • Androgens-produced in testes and adrenal cortex • Testosterone- • sperm production • secondary sex characteristics • aggression • Under control of Secretion from Pituitary: • LH -> testosterone • FSH -> acts on Sertoli cells

9. The Female Reproductive System • 2 ovaries (3 cm each) • Outer layers form oocytes (immature egg cells) • 2 oviducts (Fallopian tubes) • Uterus • Cervix • Vagina • outer stuctures: labia, clitoris

10. primary oocytes already forming in fetal female; reach prophase of 1st meiotic division • secondary oocytes continue meiosis at sexual maturity + polar body ("extra" cytoplasm-not fertile) • grow, mature • ovulation (released from ovary) • produces 2nd meiotic division (occurs after fertilization) • = OVUM and one additional polar body

11. Ovulation • Oocytes develop near surface of ovary and are surrounded by special cells • Called "ovarian follicle“, comprised of oocyte, follicular cells • During ovulation, the follicle ruptures and releases the 2nd degree oocyte • Follicle secretes Estrogens (grows Endometrium) • The follicle then enlarges and forms the Corpus Luteum "yellow body" which increases levels of progesterone to maintain pregnancy.

12. Fertilization • Secondary oocyte (egg) is "swept" into fallopian tubes by cilia. • Then, egg is propelled by waves of muscle contractions down the oviducts. • Oocyte breaks down after 72 hours. • Fertilization takes place in oviducts • The fertilized egg will reach uterus in 3 days.

13. Female Hormonal Controls • Controlled by Hypothalamus • GnRH, which triggers pituitary… • Pituitary Gland—releases-->LH, FSH which triggers… • Ovaries----> Estrogens + Progesterone • Under "feedback control system”