Ch. 20 Day 2 Flashcards
Procreation
Sexual response varies between genders and individuals
Procreation: excitation
increased muscle tone, vasocongestion of sexual organs; aka arousal
Procreation: plateau
continued vasocongestion
Procreation: orgasm
contraction of uterus/vagina and male ejaculatory organs
Procreation: resolution
body returns to pre-excitation condition
- -men experience refractory period: not able to ejaculate
- -females don’t really have refractory period
T/F: Stimulation or inhibition of erection can occur with or without input from higher brain centers.
True
-whole process of stimulation starts w/ nitric oxide
Parasympathetic stimulates or inhibits?
Stimulates
Sympathetic stimulates or inhibits?
Inhibits
Mechanism of penile vasodilatory response and basis for action of Sildenafil, similar vasoactive drugs work by inhibiting ____.
Phosphodiesterase (PDE-5)
PDE-5 activates Ca2+ channels, stimulates smooth muscle contraction –> vasoconstriction –> no erection
PDE-5 blocks Ca2+ entry, promotes smooth muscle relaxation –> vasodilation –> erection
Are there any comparable drugs currently marketed for female sexual dysfunction?
No
Male contraception
Vasectomy
- a) most widely used and reliable form of male contraception
- b) vas deferens cut and tied to prohibit sperm transport
- c) does NOT affect testosterone production or ejaculation
Newer methods of contraception:
- a) suppressing gonadotropin secretion
- b) gossypol - interferes w/ sperm production
Female contraception
Contraceptive pill
- a) includes synthetic estradiol and progesterone
- b) acts like prolonged luteal phase
- c) promotes negative feedback inhibition of GnRH –> no ovulation
- d) endometrium still proliferates
- e) placebo pills taken for 1 week to allow menstruation
- f) newer pills have reduced risk for endometrial and ovarian cancers and reduction of osteoporosis
The most effective types of female contraceptives are those that?
Require the least effort by the user
–ex: implant, vasectomy, female sterilization
After ovulation, how long are the egg & sperm viable?
Egg is viable for about 1-2 days
Sperm survive 5-6 days in female reproductive tract
After fertilization, describe: Day 1, Days 2-4, Days 4-5, Days 5-9
Day 1: fertilization
Days 2-4: cell division
Days 4-5: blastocyst reaches uterus
Days 5-9: blastocyst implants in uterine wall
In order to become mfertilization-conpetant, sperm must undergo ____ in the female reproductive tract.
Capacitation
–enzymes on head of sperm are removed, sperm is now ready to fertilize egg
Sperm and fertilization
Over 300 million sperm enter female at ejaculation
- only about 100 of these live to enter fallopian tube
- in order to fertilize ovum, sperm must become capacitated; takes at least 7 hours after ejaculation
- -> pH increases
- -> hyperactivation of flagellum
- capacitated sperm guided to oocyte by chemotaxis and thermotaxis
Fertilization occurs in?
Distal part of fallopian tube
sperm penetrates outer layers via enzymatically-mediated acrosomal reaction
Cortical reaction
when sperm enters oocyte, Ca2+ is released from endoplasmic reticulum
- calcium wave travels through oocyte to opposite side from entry of sperm
- Ca2+ has several effects:
- -> prevents other sperm from entering oocyte (polyspermy)
- -> activates oocyte to finish meiosis to become haploid ovum
Fertilization
12 hours after sperm enter oocyte, nuclear envelope around ovum disappears, and chromosomes join to form a diploid zygote
- -a) monozygotic (identical) twins - single ovum splits
- -b) dizygotic (fraternal) twins - 2 eggs fertilized by sperm
Sperm contributes 1/2 chromosomes, centrosome
Egg contributes 1/2 chromosomes, cytoplasm, all other organelles
Are mitochondria maternally or paternally inherited?
Maternally
Why are mitochondria maternally inherited?
Autophagy is cellular process whereby worn-out/damaged proteins and organelles are degraded and their components recycled
There’s a type of autophagy that is mitochondrial-specific: mitophagy
Mitophagy of sperm-derived mitochondria upon fertilization
–unknown why sperm-derived mitochondria are selectively targeted
Zygote
begins dividing in fallopian tube, implants in uterus as a blastocyst (~100 cells) 710 days post-fertilization
High levels of progesterone limit muscular contractions, so movement through fallopian tube to uterus is slow
Blastocyst
hollow ball of cells formed as division of zygote continues
Layers:
- 1) inner cell mass –> fetus
- 2) trophoblast –> chorion –> placenta
Cleavage
rapid mitosis, which form small of cells (Morula) - enters uterus about 3 days post-fertilization
begins 30-36 hours after fertilization
6 days post-fertilization
trophoblast cells secrete enzyme that allows blastocyst to “eat” into endometrium
7-10 days post-fertilization
blastocyst completely implanted
Implantation
Between days 7-12, chorion splits into:
- 1) cytotrophoblast (inner)
- 2) syncytiotrophoblast (outer)
Developing cytotrophoblast and inner cell mass separated by amniotic cavity
Syncytiotrophoblast secretes protein-digesting enzymes and creates blood-filled cavities in endometrium
Cytotrophoblast sends villi into these pools of maternal blood, forming chorion frondosum
Placental structures are “immunologically privileged site” - barrier preventing direct contact between maternal blood and fetal antigens
Fetal part of blastocyst becomes?
- Endoderm –> gut organs
2. Ectoderm –> skin and nervous system
Mesoderm
develops later –> muscle, bones and CT
Chorion
portion of trophoblast layer which becomes embryonic portion of placenta
ICM –> ?
embryo and extra embryonic membrane, including amnion, yolk sac
Placenta and amniotic sac formation
As blastocyst develops, endometrium also changes to form decide basalis
-1) joins w/ chorion frondosum to form placenta
part of chorion envelops the growing embryo
- 1) fluid-filled space between becomes amniotic sac
- 2) amniotic fluid becomes from isotonic secretion, urine from fetus, and sloughed cells
Circulation of blood in placenta
Umbilical arteries deliver fetal blood to placental vessels
Blood circulates w/in placenta and returns to fetus via umbilical vein
Maternal blood is also delivered to/from placenta
Thus, maternal and fetal blood do NOT mix; are separated by only 2 cell layers
Molecules (oxygen and nutrients) diffuse across tissues of placenta for exchange, from maternal blood to fetal blood
Carbon dioxide and wastes diffuse from fetal blood to maternal blood
Placenta degrades maternal molecules that may harm fetus
Human chorionic gonadotropin (hCG)
Secreted from chorionic villi and placenta
Binds to LH receptors on corpus luteum
Maintains viability of C.L., which continues to produce progesterone
By roughly 2-3 months, placenta takes over production of hormones
Progesterone: supports endometrium, inhibits uterine contractions
Estrogen: supports endometrium, development of milk glands
From the 2nd trimester-parturition, ____ takes over production of progesterone, estrogen.
Placenta
What is used in pregnancy tests to determine if pregnancy has occurred?
hCG
Human placental lactogen (hPL)
Secreted by placenta in proportion to placental development
Main function: induce metabolic shift in favor of fetus
decreased maternal sensitivity –> increased maternal blood glucose
decreased maternal glucose utilization –> spares glucose for fetus
increased lipolysis –> increased free fatty acids for use by mother; glucose and ketone bodies used by fetus
*Supports fetal nutrition even under conditions of maternal malnutrition
Labor and Delivery
roughly 40 weeks
precise initial trigger not clear, but probably due to combination of various factors:
- 1) secretion of CRH by placenta –> uterine production of prostaglandins –> uterine contractions
- 2) stretch of cervix induced by baby’s head –> central reflex –> oxytocin secretion –> uterine contractions
- 3) decrease of progesterone secretion by placenta –> removes inhibition of uterine contractions
Mammary gland structure and lactation
composed of 15-20 lobes separated by adipose tissue
each lobe made up of lobules composed of glandular alveoli that secrete milk in lactation
milk flows from secondary tubules –> mammary ducts –> lactiferous duct –> nipple
during pregnancy, cortisol, thyroxine, and insulin make mammary glands more sensitive to rising progesterone and estradiol levels
- -progesterone stimulates alveoli growth
- -estradiol stimulates tubule and duct growth
Control of lactation
prolactin from pituitary gland stimulates production of milk proteins, casein and lactalbumin
prolactin is inhibited by PIH (dopamine) from pituitary gland. PIH stimulated by estradiol secretion
–when placenta is shed at birth, estradiol levels drop, lifting inhibition or prolactin
Breast feeding and immunity
IgG antibodies passed from mother to child in utero
IgA antibodies passed to child from breast milk
- 1) these provide passive immunity for the first several months of life until baby can develop its own antibodies
- 2) also promotes development of baby’s own active immmunity
Menopause
female (usually > 50 years)
cessation of reproduction-competent phase of life - ovulation, menstrual cycles gradually becomes erratic and ultimately cease
appears to be due to development of insensitivity to FSH, LH in ovaries –> decreased production of estrogen, progesterone
Symptoms of menopause are due to loss of ____.
Estradiol
Symptoms of menopause
a) hot flashes are produced by vasomotor disturbances
b) walls of urethra and vagina atrophy, and vaginal glands no longer produce lubrication
c) after menopause, risk for atherosclerosis and osteoporosis increases
- -> estradiol is needed for bone deposition, so menopausal women are at increased risk for osteoporosis
- -> adipose tissue does make a weak form of estradiol called estrone. Thus, heavier women have reduced risk of osteoporosis
Andropause
male
Testosterone production decreases with aging, but precise role of decreased testosterone is not clear, since physical and psychological symptoms of aging in men and have not been clearly linked to a decline in testosterone
