Tuesday, July 25, 2006
Some Male Reproduction and Female Reproduction
(Contributed by Nancy Rumore)
Erection: psychic turns on Parasympathetic – smooth muscle relaxes and blood flows into vessels
Emission: encouragement Sympathetic causes peristalsis
Ejaculation: spinal cord reflex triggered by semen entering the prostatic urethra
Produce 3.5 ml per ejaculate
120 million sperm/ml
Corpora cavernosa – make up most of the penis and are bound by fibrous tunica albuginea
Space for drawing
Corpus spongiosum – surrounds the urethra and forms the bulb of the penis
When flaccid, the smooth muscles in the penis are constricted
FEMALE REPRODUCTION
Ovaries – female gonads
Two purposes: produce gametes and hormones
Hormones: progesterone and estrogen
Accessory ducts are: uterine tubes, uterus and vagina
OVARIES
Ovaries are served by ovarian arteries-branches of abdominal aorta and ovarian branch of uterine arteries
Ovaries are surrounded by tunica albuginea which is surrounded by germinal epithelium.
The ovary has a cortex where the oogonia are housed. (millions of oogonia- most immature sex cell)
The medulla in the ovary is where the blood vessels are.
In the female fetus, the oogonnia undergo mitosis, enter a growth phase and lay in nutrient reserves.
The female baby is born with primary oocytes (46 chromosomes). There are 7 million of these.
These primary oocytes are embedded in stroma and are surrounded with follicle cells. This is the primordial follicle.
At puberty, 700,000 oocytes remain. GH plays a big role in getting to puberty.
Ovarian cycle 1-28 days
Day 1 -10
Hypothalamus releases FSHRH and LHRH
Goes to the ant pit gland which releases FSH and LH
FSH “picks” 25 primordial follicles and tells them to mature. FSH attaches to the cells on the follicles and tell them to make estrogen.
The follicle cells take on the name granulose cells. The primordial follicle becomes the primary follicle when the follicle matures and the oocyte grows. Some of the oocytes die along the way.
A layer of connective tissue surrounds the follicle called the theca folliculi. Theca and granulose cells produce estrogens with some of the theca cells making androgens (converted to estrogen along the way).
The granulosum cells will secrete a thick transparent membrane called the zona pellucida around the oocyte. A clear liquid will accumulate between the granulose cells called antrum. The primary follicle is now a secondary follicle.
Because Inhibin is released by the granulose cells exhibiting negative feedback on FSH and LH because the estrogen levels are rising. LH and FSH levels drop.
Day 10-13 Graffian follicle (mature follicle)
When estrogen levels are very high, there is positive feedback on FSH and LH causing their levels to surge, mostly LH levels.
LH does two things: causse the primary oocyte of the dominant follicle to form a polar body (secondary oocyte) and causes tunica albuginea to thin and rupture. Day 14
Day 14- 28 The theca caves in and grows. It now transforms into the corpus luteum (CL). The secondary ooccyte is now encased in corona rediata (no longer granulosa cells)
Other follicles are absorbed.
The corpus luteum (CL) becomes an endocrine gland secreting progesterone and some estrogen. If pregnancy does not occur, the CL will degenerate in about ten days and a white scar will form (corpus albicans). If pregnancy occurs, the CL will continue to secrete progesterone until the placenta takes over in three months.
The secondary oocyte sill move into the uterine tube where in the upper 1/3 of the tube is where fertilization begins.
The Menstrual cycle
Days 1 – 5 Menstrual phase
Shedding of endomentrium (doesn’t shed its deepest part, however)
FHS and LH are low; estrogen and progesterone are also low
Day 5
Follicles are beginning to produce estrogen so these levels rise, progesterone is still low,
Day 6-14 Proliferative phase
Endometrium rebuilds itself, thickening and engorged with blood. Progesterone receptors are being synthesized. Cervical mucus becomes thin.
Ovulation occurs – LH levels are high, FSH levels are higher here, estrogen is at peak, then drops as progesterone levels increase. Ruptured follicle converts to CL.
Day 15 – 28 Secondary Phase
Endometrium prepares for implantation of fertilized egg. Progesterone levels are soaring. Uterine glands enlarge and secrete glycogen into the uterine cavity. The cervix mucus becomes thick.
LH is inhibited.
If no pregnancy occurs, the CL disintegrates and the progesterone levels fall, the endometrium sloughs off, lysosomes of endometrial cells rupture, functional layers self digest and a period begins.
Estrogen promotes fat deposits, growth of breasts, widening of pelvis, feminizing the body, growth of pubic hair, mainitain low blood cholesterol levels, facilitating Ca2+ uptake (bone density)
Progesterone works with estrogen to regulate the uterine cycle, promote changes in cervical mucus, lactation in the breasts
During pregnancy, the main source of estrogen and progesterone is the placenta.
