Pregnancy, Parturition and Lactation Flashcards
what is the zona pellucida of the ovum? what does this trigger in the sperm?
a mucus mesh of 3 glycoproteins around the egg
sperm undergo the acrosomal reaction triggered by sperm binding to one of the glycoproteins
what intracellular event causes the acrosomal reaction and what does the acrosome contain?
rise inintracellular calcium triggers exocytosis of the acrosome
contains hydrolytic enzymes that dissolve the zona pellucida
what part of the sperm enters the oocyte and how?
the cytoplasmic portion of the sperm head and tail enter
the cell membranes of the sperm and oocyte fuse
what is a cortical reaction?
a calcium/ IP3 dependant process that prevents other sperm from entering by hardening the zona pellucida
other than the cortical reaction, what other event is prompted by the increase in oocyte calcium?
a second meiotic division with expulsion of a second polar body
what happens to the contents of the sperm when they enter the oocyte?
the sperm head condenses and becomes the male pronucleus. the cytoplasmic portion of the tail degenerates
what event leads to the formation of the zygote?
the fusion of the male and female pronuclei
where does fertilization typically occur? how long does it take for the embryo to be implanted?
in the fallopian tube
4-7 days
what facilitates sperm transport in the female reproductive tract?
flagella motility
uterine, cervix and fallopian tube contraction in response to oxytocin released in the female orgasm and prostaglandins in male seminal fluid
what maintains pregnancy at the early stage before the placenta develops?
the corpus luteum produces hormones to maintain pregnancy
what does the placenta develop from?
trophoblasts and adjacent cells
what is human chorionic gonadotropin produced by? what is its function?
syncytiotrophoblasts by the blastocyst
sustains the corpus luteum even without maternal LH
what is HCG used for clinically? what else does it stimulate in the mother and fetus?
measured in urine for pregnancy tests
immunosupressive agent, promotes placental development and stimulates the testes of the male fetus to produce testosterone (male sex development)
what provides the fetus with nutrition?
early weeks: endometrial decidua
later: nutrition provided by diffusion through the placenta
what does the placenta produce?
steroid hormones, amines, polypeptides, proteins and glycoproteins
what is the most important placental peptide hormone?
HCG
what is human somatomammotrophins related to and what is their purpose?
related to growth hormone
contribute to conversion of glucose to fatty acids and ketones. also promote mammary gland development in the mother
what happens to steroid hormones in the mother during pregnancy?
estrogens and progesterone rise rapidly and remain elevated
what is the maternal-fetal-placental unit?
placenta requires the assistance of the mother and the fetus to produce steroid hormones
what does the placenta lack with respect to steroid hormone synthesis?
cannot manufacture enough cholesterol
lacks 2 enzymes needed for estrone and estradiol
lacks enzyme needed for estriol synthesis
how is the placenta supplied with cholesterol?
the mother supplies it as LDL particles
how does the fetus contribute to steroid hormone synthesis?
the fetal adrenal gland and liver supply the three enzymes lacking in the placenta
why does the fetus not have the enzymes that catalyze the final steps in estrogen synthesis?
because the fetus would be exposed to too much estrogen that is needed by the mother
what is the average duration of pregnancy?
38 weeks from the time of ovulation of 40 weeks from the first day of the last menstrual period
what occurs to the blood in pregnancy?
there is increased plasma volume and erythrocyte number. mean arterial volume decreases in mid pregnancy and rises in the third trimester
what happens to cardiac output in pregnancy? where does the extra output go?
increases in the first trimester due to increase in stroke volume
extra flow is to the kidney and uterus with some increase to heart, skin and breast
what occurs in the lungs with pregnancy? what is the effect on blood gasses?
increased tidal volume due to steroid effects on medullary repiratory centers
decreases the maternal arterial pCO2
what increase in dietary needs is seen during pregnancy?
increased demand for dietary protein, iron and folic acid
what happens to the breasts and uterus during pregnancy?
the breasts double in size and the uterus increases from 50g-> 1100 g
what is the average weight gain in pregnancy? what happens to BMR?
weight gain is 25-35lbs
BMR increases by 15%
what is parturition? what is the probably cause?
the birth of the baby
may be triggered by increase in fetal production of cortisol near term-> increases estrogen/progesterone ratio
what causes uterus quiescence through the pregnancy?
presence of progestogens and relaxins
what happens in the last month of pregnancy until labor?
irregular braxton hicks contractions
what initiates contractions and what sustains them? what do they cause?
prostaglandins
oxytocin and prostaglandins maintain
paracrine stimulation of uterine smooth muscle walls and formation of gap junctions between the cells. dilation of the cervix
what happens to oxytocin receptors in the uterus and what causes it?
estrogen increases number of receptors during pregnancy
what is the ferguson reflex?
distension of the cervix that releases maternal oxytocin in bursts with increasing frequency
what type of feedback is exhibited during labor?
positive feedback
where is relaxin produced and what does it do?
produced by the corpus luteum, placenta and decidua
softens and dilates the cervix (also involved in breast development)
what happens to the uterus ost delivery?
involution
describe hormonal involvement in lactation and breast feeding
oxytocin promotes milk letdown
prolactin promotes milk synthesis
both are released in response to suckling
define the terms mammogenic, lactogenic, galactokinetic and galactopoietic.
M- promote cell proliferation
L- promote initiation of milk production
GK-promote milk ejection
GP-maintain milk production
what type of hormone is progesterone in the breast? what does it do?
mammogenic
acts synergistically with estrogen to cause additional growth of breast lobules with alveoli budding
what is the functional secretory unit of the breast?
the alveolus. organized into lobules that drain into a ductule
what promotes milk letdown?
myoepithelial cells surround the alveolus and contract to eject milk
what comprises the alveolus? what does it respond to?
secretory epithelial cells that secrete milk in response to prolactin and cortisol
name 5 mammogenic hormones
estrogen, growth hormone, cortisol, prolactin, and relaxin
name 5 lactogenic hormones and another event that promotes initiation of milk production
prolactin, cortisol, insulin, thyroid hormone, growth hormone and removal of estrogens and progesterone
name two galactokinetic hormones and two galactopoetic hormones
GK- oxytocin and vasopressin
GP- prolactin and cortisol
what is secreted upon initiation of lactation? what is the function?
colostrum
concentrated, low volume nutrition with little or no fat (more protein) and with protective antibodies
describe the composition of breast milk
low protein (casein and lactalbumin), high fat emulsion containing lactose and electrolytes
what are the main differences between cows milk and human milk?
cows milk has higher electrolyte concentration and significantly more casein (protein)
what do progesterone and estrogen do for breast development and milk secretion?
critical for development but prevent milk secretion
what does suckling inhibit the release of?
GnRH-> inhibits release of FSH and LH and preventing ovarian cycle
what is the effect of suckling on the paraventricular nuclei of the hypothalamus? the arcuate nucleus?
PVN- triggers production and release of oxytocin from posterior pituitary
Arcuate- inhibits dopamine release that would inhibit prolactin release (prolactin is released)
