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Mammalian Reproduction

Mammalian Reproduction. Group 2 III-Cesium. Male reproductive anatomy (overview). Internal reproductive organs: Gonads: produce gametes and hormones Accessory glands: secrete products essential for sperm movement Ducts: carry the sperm and glandular secretions

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Mammalian Reproduction

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  1. Mammalian Reproduction Group 2 III-Cesium

  2. Male reproductive anatomy(overview) • Internal reproductive organs: • Gonads: produce gametes and hormones • Accessory glands: secrete products essential for sperm movement • Ducts: carry the sperm and glandular secretions • External reproductive organs: • scrotum • penis

  3. Testes: the male gonads • Consist of seminiferous tubules interspersed with Leydig cells • Seminiferous tubules: sperm production ( approx. 200 mil/day) • Leydig cells: production of androgens (testosterone) • Following production, sperm pass into the epididymis

  4. Epididymis • Composed of 6 metre-long coiled tubules • Stores sperm for about 20 days • sperm mature and gain: • Ability to fertilize • Motility • Vas deferens • Two ducts, each running from the epididymis to the back of the urinary bladder • Ends in an ejaculatory duct • Opens into the urethra • During ejaculation, sperm are propelled from the epididymis through the vas deferens

  5. Urethra • Tube that runs from the bladder through the prostate gland to the end of the penis • Functions in both the reproductive and the excretory systems: • Exit point for semen and urine • Closing of muscular sphincters 1. Urinary Bladder2. Pelvic Urethra3. Penile Urethra

  6. Accessory glands • Add secretions to semen • Semen: fluid ejaculated • Seminal vesicles • a pair of glands opening into the urethra • contributes 60% of the semen (3-5mL) • Supplies a thick, yellowish, alkaline fluid • Mucus • Fructose sugar (energy) • Coagulating enzyme • Ascorbic acid • prostaglandins

  7. 2) Prostate gland • largest of the glands • Secretes a thin, milky-white fluid directly into the urethra • Anti-coagulant enzymes • Citrate (a sperm nutrient) • Slightly acidic • 3) Bulbourethral glands • Pair of glands along the urethra • Produce a clear, alkaline mucus • Secreted into the urethra before ejaculation • Neutralize acidic urine • Also carries some sperm

  8. External organs • Scrotum • Fold of the body wall • Holds the testes outside the abdominal cavity • Sperm production cannot occur at normal body temperature (98.6F) • Temperature in scrotum: 95-97F • Not present in all mammals (e.g. whales, elephants) • Penis • Serves to deposit the sperm in the female genital tract • 3 cylinders of spongy erectile tissue • Engorges with blood during arousal • Forms an erection necessary for insertion • Baculum: rodents, raccoons, walruses • Bone that helps stiffen the penis • Glans penis: head of the penis • Covered by a prepuce (foreskin) • Also functions in the excretory system

  9. Female Reproductive anatomy (an overview) • Internal reproductive organs: • Gonads: produce the eggs • Ducts and chambers: • channel the gametes • Accommodate the embryo and fetus • External Reproductive organs: • Clitoris • Labia minora • Labia majora

  10. Ovaries: the female gonads • Lie in the abdominal cavity • Enclosed in a tough, protective capsule • Contain the follicles (approx 400 000) • Follicles: one egg cell and its emveloping layers of follicle cells • Formed before birth • Follicle cells: nourish and protect the cells • Produce estrogens • Release the egg during ovulation • Ovulation: release of an egg from the ovaries during the menstrual cycle • Corpus lutaeum: composed of remaining follicular tissue • Grows within the ovary • Secretes estrogens and progesterone • Disintegrates if egg is not fertilized

  11. Oviduct (fallopian tube) • Duct that opens with a funnel-like entrance • Lined with cilia • Collects the egg upon release • Conveys the egg cell from the ovaries to the uterus • Uterus (womb) • Thick, muscular organ • Expands during pregnancy • Endometrium • Inner lining of the uterus • Highly vascularized

  12. Cervix: neck of the uterus • opens into the vagina • Vagina • Thin-walled chamber • Functions: • Birth canal • Repository of sperm during intercourse • Hymen: partial covering of the vagina • Ruptured during copulation/intense physical activity

  13. Vestibule • Contains the vaginal and urethral openings • Bordered by the labia minora • Slender skin folds • Enclosed by the labia majora • Thick, fatty ridges • Clitoris • Located at the front edge of the vestibule • Engorges with blood during arousal • Consists of: • Rounded glans (covered by a prepuce) • Supporting shaft • Erectile tissue

  14. Bartholin’s glands • Secrete mucus into the vestibule • Lubrication • Facilitates intercourse • Mammary glands • Consist of: • Small sacs of epithelial tissue • Secrete milk • Adipose tissue • Function only in women

  15. Human sexual response • Terms: • Coitus: sexual intercourse • Vasocongestion: swelling of body tissues due to increased arterial blood flow • Myotonia: increased muscle tension

  16. The sexual cycle is divided into 4 phases • 1) excitement • Readies the vagina and penis for coitus • Involves: • Enlargement of testes, labia, breasts • Vaginal lubrication • Vasocongestion of vagina and penis • Myotonia in arms and legs • 2) plateau phase • Continues responses begun in excitement phase • Involves: • Increase in breathing and heart rates • Formation of a depression at the back of the vagina • For the reception of sperm

  17. 3) Orgasm: rhythmic, involuntary contractions of reproductive structures • 2 phases: • Emission:contraction of glands and ducts • Forces sperm into the urethra • Ejaculation:expulsion of semen (2-5 mL; 100-650 mil sperm) • Prostaglandins thin mucus at the opening of the female uterus • Stimulates contraction of uterine muscles, moving up the coagulated semen • Anticoagulants liquify the semen • Sperm swim through the female tract

  18. 4) Resolution: final phase • Reverses the effects of the previous stages • Vasocongested organs relax

  19. Structure of the sperm cell • Produced via spermatogenesis • Occurs in the seminiferous tubules • Consists of: • Head • Haploid nucleus • Acrosome: anterior-most organelle • Contains enzymes: sperm penetration • Varied shapes (oval, spherical, comma) • Neck • Middle piece • Mitochondrion: ATP for tail movement • Tail (flagellum)

  20. Structure of the egg cell • Oogenesis: production of ova • Ova: mature, unfertilized egg cells • Consists of: • Yolk: cell substance • Germinal vesicle: nucleus • Germinal spot: nucleolus • Zona pellucida: thick, transparent envelope surrounding the egg cell • Corona radiata: surrounds the zona pellucida • Layers of cells derived from the follicle

  21. FIN

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