Pregnancy, Parturition and Lactation

Question 1

what is the zona pellucida of the ovum? what does this trigger in the sperm?

Answer 1

a mucus mesh of 3 glycoproteins around the egg

sperm undergo the acrosomal reaction triggered by sperm binding to one of the glycoproteins

Question 2

what intracellular event causes the acrosomal reaction and what does the acrosome contain?

Answer 2

rise inintracellular calcium triggers exocytosis of the acrosome
contains hydrolytic enzymes that dissolve the zona pellucida

Question 3

what part of the sperm enters the oocyte and how?

Answer 3

the cytoplasmic portion of the sperm head and tail enter

the cell membranes of the sperm and oocyte fuse

Question 4

what is a cortical reaction?

Answer 4

a calcium/ IP3 dependant process that prevents other sperm from entering by hardening the zona pellucida

Question 5

other than the cortical reaction, what other event is prompted by the increase in oocyte calcium?

Answer 5

a second meiotic division with expulsion of a second polar body

Question 6

what happens to the contents of the sperm when they enter the oocyte?

Answer 6

the sperm head condenses and becomes the male pronucleus. the cytoplasmic portion of the tail degenerates

Question 7

what event leads to the formation of the zygote?

Answer 7

the fusion of the male and female pronuclei

Question 8

where does fertilization typically occur? how long does it take for the embryo to be implanted?

Answer 8

in the fallopian tube

4-7 days

Question 9

what facilitates sperm transport in the female reproductive tract?

Answer 9

flagella motility
uterine, cervix and fallopian tube contraction in response to oxytocin released in the female orgasm and prostaglandins in male seminal fluid

Question 10

what maintains pregnancy at the early stage before the placenta develops?

Answer 10

the corpus luteum produces hormones to maintain pregnancy

Question 11

what does the placenta develop from?

Answer 11

trophoblasts and adjacent cells

Question 12

what is human chorionic gonadotropin produced by? what is its function?

Answer 12

syncytiotrophoblasts by the blastocyst

sustains the corpus luteum even without maternal LH

Question 13

what is HCG used for clinically? what else does it stimulate in the mother and fetus?

Answer 13

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)

Question 14

what provides the fetus with nutrition?

Answer 14

early weeks: endometrial decidua

later: nutrition provided by diffusion through the placenta

Question 15

what does the placenta produce?

Answer 15

steroid hormones, amines, polypeptides, proteins and glycoproteins

Question 16

what is the most important placental peptide hormone?

Answer 16

HCG

Question 17

what is human somatomammotrophins related to and what is their purpose?

Answer 17

related to growth hormone

contribute to conversion of glucose to fatty acids and ketones. also promote mammary gland development in the mother

Question 18

what happens to steroid hormones in the mother during pregnancy?

Answer 18

estrogens and progesterone rise rapidly and remain elevated

Question 19

what is the maternal-fetal-placental unit?

Answer 19

placenta requires the assistance of the mother and the fetus to produce steroid hormones

Question 20

what does the placenta lack with respect to steroid hormone synthesis?

Answer 20

cannot manufacture enough cholesterol
lacks 2 enzymes needed for estrone and estradiol
lacks enzyme needed for estriol synthesis

Question 21

how is the placenta supplied with cholesterol?

Answer 21

the mother supplies it as LDL particles

Question 22

how does the fetus contribute to steroid hormone synthesis?

Answer 22

the fetal adrenal gland and liver supply the three enzymes lacking in the placenta

Question 23

why does the fetus not have the enzymes that catalyze the final steps in estrogen synthesis?

Answer 23

because the fetus would be exposed to too much estrogen that is needed by the mother

Question 24

what is the average duration of pregnancy?

Answer 24

38 weeks from the time of ovulation of 40 weeks from the first day of the last menstrual period

Question 25

what occurs to the blood in pregnancy?

Answer 25

there is increased plasma volume and erythrocyte number. mean arterial volume decreases in mid pregnancy and rises in the third trimester

Question 26

what happens to cardiac output in pregnancy? where does the extra output go?

Answer 26

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

Question 27

what occurs in the lungs with pregnancy? what is the effect on blood gasses?

Answer 27

increased tidal volume due to steroid effects on medullary repiratory centers decreases the maternal arterial pCO2

Question 28

what increase in dietary needs is seen during pregnancy?

Answer 28

increased demand for dietary protein, iron and folic acid

Question 29

what happens to the breasts and uterus during pregnancy?

Answer 29

the breasts double in size and the uterus increases from 50g-> 1100 g

Question 30

what is the average weight gain in pregnancy? what happens to BMR?

Answer 30

weight gain is 25-35lbs | BMR increases by 15%

Question 31

what is parturition? what is the probably cause?

Answer 31

the birth of the baby | may be triggered by increase in fetal production of cortisol near term-> increases estrogen/progesterone ratio

Question 32

what causes uterus quiescence through the pregnancy?

Answer 32

presence of progestogens and relaxins

Question 33

what happens in the last month of pregnancy until labor?

Answer 33

irregular braxton hicks contractions

Question 34

what initiates contractions and what sustains them? what do they cause?

Answer 34

prostaglandins oxytocin and prostaglandins maintain paracrine stimulation of uterine smooth muscle walls and formation of gap junctions between the cells. dilation of the cervix

Question 35

what happens to oxytocin receptors in the uterus and what causes it?

Answer 35

estrogen increases number of receptors during pregnancy

Question 36

what is the ferguson reflex?

Answer 36

distension of the cervix that releases maternal oxytocin in bursts with increasing frequency

Question 37

what type of feedback is exhibited during labor?

Answer 37

positive feedback

Question 38

where is relaxin produced and what does it do?

Answer 38

produced by the corpus luteum, placenta and decidua | softens and dilates the cervix (also involved in breast development)

Question 39

what happens to the uterus ost delivery?

Answer 39

involution

Question 40

describe hormonal involvement in lactation and breast feeding

Answer 40

oxytocin promotes milk letdown prolactin promotes milk synthesis both are released in response to suckling

Question 41

define the terms mammogenic, lactogenic, galactokinetic and galactopoietic.

Answer 41

M- promote cell proliferation L- promote initiation of milk production GK-promote milk ejection GP-maintain milk production

Question 42

what type of hormone is progesterone in the breast? what does it do?

Answer 42

mammogenic | acts synergistically with estrogen to cause additional growth of breast lobules with alveoli budding

Question 43

what is the functional secretory unit of the breast?

Answer 43

the alveolus. organized into lobules that drain into a ductule

Question 44

what promotes milk letdown?

Answer 44

myoepithelial cells surround the alveolus and contract to eject milk

Question 45

what comprises the alveolus? what does it respond to?

Answer 45

secretory epithelial cells that secrete milk in response to prolactin and cortisol

Question 46

name 5 mammogenic hormones

Answer 46

estrogen, growth hormone, cortisol, prolactin, and relaxin

Question 47

name 5 lactogenic hormones and another event that promotes initiation of milk production

Answer 47

prolactin, cortisol, insulin, thyroid hormone, growth hormone and removal of estrogens and progesterone

Question 48

name two galactokinetic hormones and two galactopoetic hormones

Answer 48

GK- oxytocin and vasopressin | GP- prolactin and cortisol

Question 49

what is secreted upon initiation of lactation? what is the function?

Answer 49

colostrum | concentrated, low volume nutrition with little or no fat (more protein) and with protective antibodies

Question 50

describe the composition of breast milk

Answer 50

low protein (casein and lactalbumin), high fat emulsion containing lactose and electrolytes

Question 51

what are the main differences between cows milk and human milk?

Answer 51

cows milk has higher electrolyte concentration and significantly more casein (protein)

Question 52

what do progesterone and estrogen do for breast development and milk secretion?

Answer 52

critical for development but prevent milk secretion

Question 53

what does suckling inhibit the release of?

Answer 53

GnRH-> inhibits release of FSH and LH and preventing ovarian cycle

Question 54

what is the effect of suckling on the paraventricular nuclei of the hypothalamus? the arcuate nucleus?

Answer 54

PVN- triggers production and release of oxytocin from posterior pituitary Arcuate- inhibits dopamine release that would inhibit prolactin release (prolactin is released)