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Microscopic Anatomy of Selected Male and Female Reproductive Organs

Microscopic Anatomy of Selected Male and Female Reproductive Organs. Testes. Each lobule contains one to four seminiferous tubules Tightly coiled structures Function as sperm-forming factories Empty sperm into the rete testis . Figure 16.1. Testes.

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Microscopic Anatomy of Selected Male and Female Reproductive Organs

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  1. Microscopic Anatomy of Selected Male and Female Reproductive Organs

  2. Testes • Each lobule contains one to four seminiferous tubules • Tightly coiled structures • Function as sperm-forming factories • Empty sperm into the rete testis Figure 16.1

  3. Testes • Each lobule contains one to four seminiferous tubules • Tightly coiled structures • Function as sperm-forming factories • Empty sperm into the rete testis (first part of the duct system) • Sperm travels through the rete testis to the epididymis • Interstitial cells in the seminiferous tubules produce androgens such as testosterone

  4. External Genitalia Erections occur when spongy erectile tissue fills with blood during sexual excitement Figure 16.2a

  5. External Genitalia • Internally there are three areas of spongy erectile tissue around the urethra • Erections occur when this erectile tissue fills with blood during sexual excitement

  6. Testes Figure 16.1

  7. The ruptured follicle is transformed into a corpus luteum Ovaries • Each follicle consists of • Oocyte (immature egg) • Follicular cells—surround the oocyte Primary follicle—contains an immature oocyte Graafian (vesicular) follicle—growing follicle with a maturing oocyte Figure 16.7

  8. Ovaries • Composed of ovarian follicles (sac-like structures) • Each follicle consists of • Oocyte (immature egg) • Follicular cells—surround the oocyte

  9. Ovarian Follicle Stages • Primary follicle—contains an immature oocyte • Graafian (vesicular) follicle—growing follicle with a maturing oocyte • Ovulation—when the egg is mature, the follicle ruptures; occurs about every 28 days • The ruptured follicle is transformed into a corpus luteum

  10. Hormone Production by the Ovaries • Estrogens • Produced by follicle cells • Cause secondary sex characteristics • Enlargement of accessory organs • Development of breasts • Appearance of axillary and pubic hair • Increase in fat beneath the skin, particularly in hips and breasts • Widening and lightening of the pelvis • Onset of menses (menstrual cycle)

  11. Hormone Production by the Ovaries • Progesterone • Produced by the corpus luteum • Production continues until LH diminishes in the blood • Does not contribute to the appearance of secondary sex characteristics • Other major effects • Helps maintain pregnancy • Prepare the breasts for milk production

  12. Meiotic Events Follicle Developmentin Ovary Before birth 2n Oogonium (stem cell) Follicle cells Mitosis Oocyte Primaryfollicle 2n Primary oocyte Growth Primary oocyte(arrested in prophase I;present at birth) Primaryfollicle 2n (ovary inactive) Childhood Each month frompuberty to menopause Primaryfollicle Primary oocyte (stillarrested in prophase I) 2n Growingfollicle Maturevesicular(Graafian)follicle Meiosis I (completed by oneprimary oocyte each month) Secondary oocyte(arrested inmetaphase II) n First polar body Ovulation Sperm Ovulatedsecondaryoocyte Meiosis II of polar body(may or may not occur) Meiosis II completed(only if spermpenetration occurs) n n n n Polar bodies(all polar bodiesdegenerate) Secondpolar body Ovum Oogenesis Figure 16.10, step 9

  13. Oogenesis and the Ovarian Cycle • Oogonia—female stem cells found in a developing fetus • Oogonia undergo mitosis to produce primary oocytes • Primary oocytes are surrounded by cells that form primary follicles in the ovary • Oogonia no longer exist by the time of birth

  14. Oogenesis and the Ovarian Cycle • Primary oocytes are inactive until puberty • Follicle stimulating hormone (FSH) causes some primary follicles to mature each month • Cyclic monthly changes constitute the ovarian cycle

  15. Oogenesis and the Ovarian Cycle • Meiosis starts inside maturing follicle • Produces a secondary oocyte and the first polar body • Follicle development to the stage of a vesicular follicle takes about 14 days • Ovulation of a secondary oocyte occurs with the release of luteinizing hormone (LH) • Secondary oocyte is released and surrounded by a corona radiata

  16. Ovulation Figure 16.11

  17. Oogenesis and the Ovarian Cycle • Meiosis is completed after ovulation only if sperm penetrates • Ovum is produced • Two additional polar bodies are produced • Once ovum is formed, the 23 chromosomes can be combined with those of the sperm to form the fertilized egg (zygote) • If the secondary oocyte is not penetrated by a sperm, it dies and does not complete meiosis to form an ovum

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