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A.P. Biology Chapter 46
Transcript of A.P. Biology Chapter 46
Animal Reproduction Menstrual (Uterine) Cycle Key Hormones By:
Erik, Lucy, & Flam Gametogenesis The Production of Gametes spermatogenesis - the formation and development of sperm
continuous and prolific in adult males--average man produces hundreds of millions of sperm each day
occurs in the seminiferous tubules coiled within the two testes Spermatogenesis primordial germ cell in embryo (2n) ---mitosis--> spermatogonial stem cell (2n) ---mitosis--> spermatogonium (2n) ---mitosis--> primary spermatocyte (2n) ---meiosis I--> secondary spermatocyte (n) ---meiosis II--> early spermatid (n) ---differentiation--> sperm cell (n) oogenesis - the development of mature oocytes (eggs)
a prolonged process in the human female; immature eggs form in the ovary of the female embryo but do not complete their development until years later
occurs in the ovaries; primary oocytes mature into eggs within follicles (small cavities within the ovary lined with protective cells) Oogenesis primordial germ cell (2n) ---mitosis--> oogonium ---mitosis--> primary oocyte (2n) primary oocytes (present at birth) are arrested in prophase of meiosis I and resume development during puberty primary oocyte ---completion of meiosis I--> secondary oocyte (n) secondary oocyte arrested at metaphase of meiosis II, released at ovulation; resumes meiosis II after sperm penetration secondary oocyte ---completion of meiosis II--> fertilized egg ruptured follicle develops into corpus luteum Differences Between Oogenesis and Spermatogenesis Only in spermatogenesis do all four products of meiosis develop into mature gametes; in oogenesis, meiosis of an oocyte results in one egg and three polar bodies, which degenerate
Spermatogenesis occurs throughout adolescence and adulthood; during oogenesis, mitotic divisions are complete before birth, and production of mature gametes ceases at about age 50
Spermatogenesis occurs in a continuous sequence, while oogenesis has long interruptions 9-estroidil and progesterone secreted by the corpus luteum stimulate continued development and maintenance of the uterine lining
10-after the corpus luteum disintegrates, the rapid drop in ovarian hormone levels causes arteries in the endometrium to constrict. this causes most of the the uterine lining to disintegrate
endometrium- inner lining of the uterus, richly supplied with blood vessels
Average 28 day cycle, but can range from about 20-40 days
endometriosis is a disorder in which some cells of the uterine lining migrate to an abdominal location that is abnormal
can cause bleeding in the abdomen and pelvic pain Hormonal Control of the Menstrual Cycle,
How Oogenesis and Spermatogenesis Differ
Reproductive Organs Ovarian Cycle Cyclical events in the ovaries
1-cycle begins with the realse from the hypothalmus of GnRH
2- stimulates the anterior pituitary to secrete small amounts of FSH and LH
3- FSH stimulates follicle growth, aided by LH
4-cells of the follicle start to make estroidil
5- follicle production of estroidil rises steeply
6- FSH and LH levels increase
7- maturing follicle forms a bulge near the surface of the ovary, ovulation occurs
8- Lh stimulates the left over follicle to transform into the corpus luteum
As the ovarian cycle comes to an end, the negative feedback system in the pituitary gland allows it to initiate the next ovarian cycle Gonartropin- releasing Hormone (GnRH)
Follicle-stimulating Hormone (FSH)
Lutenizing Hormone (LH)
Progesterone Menopause the cessation of ovulation and menstruation
occurs after about 500 cycles
occurs between the ages of 46 and 54
unusual phenomenon because in most other species, both male and female retain reproductive capacity throughout life
Spermatheca: A sac in which sperm may be stored for extended periods.
Cloaca: A common opening for the digestive, excretory, and reproductive systems. Vagina and Vulva:
- Vagina: a muscular and elastic chamber that is the site of desposition of the sperm.
- also serves as the birth canal.
- Vulva: external female genitals.
- Labia majora: thick, fatty ridges that encloses and protects the vilva.
- hymen: partly covers the vaginal opening until intercourse or vigorous physical activity.
- Clitoris: located at the upper intersection of the labia minora.
- Consists largely of erectile tissue that fills with blood and elarges during intercourse. Male Reproductive Organs Gonads:
- Testes: consists of highly coiled tubes surrounded by several layers of connective tissue.
- Seminiferous tubules: where sperm forms.
- Leydig cells: scattered between the seminiferous tubules, produces testosterone.
- Scrotum: a fold of the body wall, maintains testis temperature about 2 degrees (c) lower than the abdominal cavity.
- Testes develop high in the abdominal cavity and descend into the scrotum before birth.
- Epididymis: coiled tubules where sperm passes through after it has passed through the seminiferous tubules
- During this 3 week passage, sperm complete their maturation and become motile.
- Ejaculation: sperm are propelled from each epididymis through a muscular duct called the vas deferens.
- Each vas deferens extends around and behind the urinary bladder, where it joins a duct from the seminal vesicle, forming the ejaculatory duct.
- Urethra: The outlet tube for the excretory and reproductive systems.
- Semen: combination of secretions and sperm that creates a fluid which is ejaculated.
- Seminal Vesicles: two of these contribute to about 60% of the volume of semen.
- Contains fructose (sperm's energy source), coagulating enzyme, ascorbic acid, and prostaglandins.
- Prostate Gland: secretes its products directly into the urethra
- fluid contains anticoagulant enzymes and citrate (sperm nutrient).
- Bulbourethral Glands: secretes mucus that neutralizes acidic urine in the urethra. Male Reproductive Organs (Cont.) Nonmammalian Reproductive Organs Female Reproductive Organs Gonads: The internal organs that produce gametes in most animals
- 2 Ovaries that flank the uterus.
- Follicles: contains developing eggs and secretes estrogen (about 1-2 million in each ovary).
- Oocyte: A partially developed egg that is surrounded by support cells
- Corpus luteum: A mass that forms from the residual follicular tissue within the ovary.
- secretes estradiol and progesterone which helps maintain the uterine lining during pregnancy.
- The corpus luteum will degenerate if the egg is not fertilized, and a new follicle matures during the next cycle.
Oviduct and Uterus:
- Oviduct (fallopian tube): extends from the uterus to each ovary.
- During ovulation, the egg is released into the abdominal cavity near the opening of the oviduct.
- Cilia moves the egg down the oviduct into the uterus.
- Uterus: a thick, muscular organ that expands during pregnancy.
- Endometrium:inner lining of the uterus that is richly supplied with blood vessels.
- Cervix: neck of the uterus that opens into the vagina. Female Reproductive Organs (cont.) - Penis: Contains the urethra and erectile tissue.
- During intercourse, the erectile tissue swells with blood.
- Shaft is covered by relatively thick skin. Bibliography Reece. "Chapter 46." AP Edition- Biology. By Cambell. 8th ed. San Francisco: Benjamin Cummings, 2008. 997-1019. Print.