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tandem pregnancies → 2 offspring (or litters) are delivered at intervals equal to 1 or 2 estrous/menstrual cycles
* live offspring, normal birthweight, normal developmental signs
obstacles to superfetation (4)
1. ovulation during pregnancy
2. estrus, sperm transport through cervix, etc.
3. embryo transport to uterus
4. controlled contractions of uterus at 1st delivery
problems associated with superfetation (3)
1. competition within the uterus
*note: freemartinism is not a problem
what is the term for the mammary gland and what type of gland is it?
mammae = breast or milk-forming gland → skin gland
mammary glands are specialized glands that consist of...
a teat or nipple and their associated ducts & alveoli
mammary gland species variation:
1. 4 mammary glands; inguinal region
2. 14 teats; thor-abdom-inguinal region
3. 2 mammary glands; thoracic region
4. 8-10 glands; thor-abdom-inguinal region
relationships between lactation & reproduction (3)
1. lactation occurs after conception & pregnancy → ovaries affect MGs
2. lactational anestrus (varies among species)
3. endocrine changes during lactation lead to suppressed FSH & LH secretion and affect ovarian function
species variation in length of lactational anestrus
cow < ewe & mare < sow & rodents (entire length of lactation)
specific links between reproductive organs & mammary glands (3)
1. onset of puberty in female → increased mammary growth caused by E2 & P4 from ovaries
2. MGs grow & regress with each estrous cycle
3. most mammary cell mitotic division occurs during pregnancy (induced by E2, P4, PRL & PL (placental lactogen))
mammary life cycle (4 stages + details)
1. mammogenesis → development of MG to point where it can secrete milk
2. lactogenesis → beginning of milk secretion
3. galactopoiesis → maintenance of milk secretion once it begins
4. involution → regression of MG to non-functional status ("dry period")
why do newborns need milk? (5)
1. milk has readily digestible energy for homeothermy
2. colostrum: immunoglobulins for passive immunity
3. milk is easily digested
4. acts as a probiotic
5. hormonal effects and more...
composition of milk: notable feature in...
1. high lactose
2. high protein
3. low water & high fat → important for warmth
benefits of breast feeding in humans (5)
1. maternal-infant psychological bonding
2. economical (very important for poor people)
3. reduces later development of bovine milk allergies
4. provides mom with some protection against breast cancer
5. decreases likelihood of obesity in child
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