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20. Parturition and Lactation
N/A
114
Anatomy
Undergraduate 2
11/29/2012

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Term
What does parturition require?
Definition
  • dilation of the cervical canal to accomodate passge of the fetus from the uterus from the vagina and to the outside
  • contraction of uterine myometrium that are suffieciently strong to expel the fetus 
  • expulsion of the placenta
Term
What is the function of PGF2alpha in parturition?
Definition
  • it initiates uterine contraction and regression of the CL. 
  • stimulates synthesis of relaxin 
Term
What is the function of relaxin from the CL and the placenta during parturition?
Definition
it softens the cervix as a result of the dissociation of connective tissue
Term
What is the function of oxytocin from the hypothalamus in parturition?
Definition
it initiates true labor; rhythmic directional contractions
Term
What happens during stage one of parturition?
Definition
  • uterine contractions
  • cerzix opens as the calf pushes against it
Term
What happens during stage 2 of parturition?
Definition
the calf moves through the open cervix, hips, and vaginal canal
Term
When does stage 2 end?
Definition
when the calf is born
Term
What happens if the placenta is retained?
Definition
  • immature placentation (non-infectious abortion, premature parturition)
  • periparturient immuno-supression (leukocytes and cotyledon)
  • edema of chorionic villi (C-section, torsion)
  • placentitis, cotyledonitis (infectious abortions)
  • uterine atony (milk fever) 
Term
What is distocia?
Definition
an abnormal or difficult labor
Term
What are some possible causes of dystocia?
Definition
  • incoordinate uterine activity 
  • abnormal fetal lie or position
  • absolute or relative cephalopelvic disproportion
Term
What is commonly used to treat incoordinate uterine activity?
Definition
oxytocin
Term
At fertilization, there is a huge spike in the secretion of the human placental hormone ________________.
Definition
human Chorionic Gonadotropin
Term
At fertilization, what other two hormones gradually start to increase in secretion?
Definition
estrogen and progesterone
Term
What human placental hormone gradually starts to decrease throughout pregnancy? Explain.
Definition
human chorionic gonadotropin starts to gradually decrease but not until after the spike at fertilization
Term
Parturition is accomplished through a __________ cycle.
Definition
positive feedback
Term
What are the teats of a cow like?
Definition
4 teats, one opening
Term
What are the teats of a ewe like?
Definition
2 teats, one opening, sparse hair
Term
What are the teats of a mare like?
Definition
2 teats with 2 openings; short and laterally flattened
Term
What are the teats of a sow like?
Definition
12 to 14 teats, small, long, cylindrical; 2 inguinal pairs, 3 abdominal pairs, 2 thoracic pairs; 2-3 openings
Term
When does development of mammary glands start and finish?
Definition
puberty to gestation
Term
Mammary glands are modified _____________.
Definition
sweat glands
Term
How doe mammary glands develop?
Definition
they develop from a milk line which differentiates into mammary buds 
Term
The development and functioning of mammary glands depends on _________.
Definition
hormones
Term
What other products influence the development of mammary glands?
Definition
GH, TSH, and ACTH
Term
What hormone promotes mammary gland development?
Definition
estrogen
Term
What hormone stimulates lobular alveoli formation?
Definition
progesterone
Term
What hormones induce synthesis of the enzymes required for milk secretion?
Definition
prolactin and somatomammotropin
Term
How do high levels of estrogen and progesterone in late preganancy prevent lactation?
Definition
they block prolactin's stimulatory action on milk production
Term
___________ promotes mammary gland development.
Definition
estrogen
Term
What happens to the human placental hormones at parturition?
Definition
they drop significantly
Term
What are the three main human placental hormones?
Definition
estrogen, progesterone, and human chorionic gonadotropin
Term
Where is corticotrpin releasing hormone secreted from?
Definition
the fetal placenta
Term
What does corticotropin releasing hormone lead to the secretion of?
Definition
ACTH (adrenocorticotropin hormone)
Term
Corticotropin releasing hormone causes the secretion of ACTH. What does this ACTH do?
Definition
it causes the production of cortisol and DHEA
Term
What is the function of the cortisol that is released as a result of ACTH?
Definition
it prepares the lung for breathing by causing the release of surfectant
Term
What is the function of the DHEA that is released as a result of the secretion of ACTH? What does this lead to?
Definition
it is converted to estrogen which leads to an increased level of estrogen
Term
Estrogen promotes the synthesis of _________. What does this prepare for?
Definition
connexins; this prepares for muscle contraction
Term
Estrogen also increases ______ and increases the sensitivity of the uterus to ___________.
Definition
PGF2alpha, oxytocin
Term
How does estrogen increase the sensitivity of the uterus to oxytocin?
Definition
it increases the myometrial receptors for oxytocin
Term
Uterine contractions have a (negative/ positive) feedback for (more/less) __________.
Definition
positive, more, oxytocin
Term
What are the three main functions that oxytocin are responsible for?
Definition
  • uterine contraction
  • milk ejection during lactation
  • maternal behavior
Term
What about oxytocin induces uterine contraction?
Definition
increasing oxytocin receptor concentration
Term
Name the process that occurs prior to parturition starting with the release of CRH up to the release of cortisol and DHEA.
Definition
  • the placenta releases CRH which increases CRH level
  • this goes into fetal circulation until it reaches the fetuses anterior pituitary
  • this leads to a release of ACTH 
  • this increase in ACTH goes to the fetal adrenal cortex 
  • the adrenal cortex then releases cortisol and DHEA
Term
Explain what happens after cortisol level increases prior to parturition.
Definition
  • the increased cortisol level reaches the fetus's lungs causing the release of pulmonary surfectant 
  • this leads to lung maturation in preparation for breathing air
Term
Explain what happens as a result of DHEA secretion up to progesterone and estroegn secretion.
Definition
  • the increase in the level of DHEA goes to the placenta where it is converted to estrogen
  • this leads to an increase in estrogen concentration and a decrease in progesterone secretion 
Term
What three things does the incerase in estrogen and a decrease in progesterone secretion lead to?
Definition
  • gap junctions between myometrial cells
  • and increase in the number of oxytocin receptors in the myometrium
  • an increase in prostaglandin production
Term
What does an increase in the number of gap junctions bewteen myometrial cells lead to? What does this lead to?
Definition
the uterus is then able to contract as a coordinated unit; the uterus is then responsive to low levels of oxytocin
Term
What does in increase in the number of myometrial oxytocin receptors lead to?
Definition
it increases uterine responsiveness to low levels of oxytocin
Term
What does an increase in prostaglandin production lead to?
Definition
cervical softening
Term
What does an increase in reposniveness of the uterus to low levels of oxytocin lead to?
Definition
an increase in uterine contractions which causes the fetus to push against the cervix which causes more oxytocin to be released which leads to an increase in prostaglandins which causes more uterine contractions
Term
Explain the pathway for placentantal synthesis of progesterone.
Definition
  • cholesterol in the maternal blood enters the placenta
  • cholesterol in the placenta causes the releases of progesterone from the placenta which enters the maternal blood
Term
Explain the pathway for placental synthesis of estrogen.
Definition
  • cholesterol from the maternal blood enters the placenta which enters the fetal blood which enters the fetal adrenal cortex
  • this leads to the synthesis of DHEA
  • the DHEA enters the fetal blood which enters the placenta 
  • here the DHEA is converted to etrogen and this estrogen enters the maternal blood
Term
What does puberty estrogen stimulate the growth of with regards to mammary glands?
Definition
the ducts and cisterns
Term
Where does puberty estroegn come from?
Definition
the ovaries
Term
What does puberty progesterone stimulate the growth of with regards to mammary glands?
Definition
aveoli
Term
What are estrogen and progesterone under the control of?
Definition
FSH and LH from the anterior pituitary
Term
_________ stimulate lobular aveoli formation.
Definition
progesterone
Term
_____________ and ____________ induce the synthesis of enzymes required for milk production.
Definition
prolactin, chorionic somatomammotropin
Term
How is lactation prevented?
Definition
the high level of estrogen and progesterone in the last half of pregnancy prevent lactation by blocking prolactin's stimulatory action on milk secretion
Term
What happens causes lactation to begin?
Definition
an abrupt decline in estrogen and progesterone
Term
Once lactation begins as a result in the ubrupt drop in estrogen and progesterone, what happens?
Definition
  • prolactin acts on aveolar epithelium to promote milk production 
  • oxytocin induces milk ejection from aveoli to lactiferous sinus 
Term
What is the capsule surrounding the aveoli made of?
Definition
connective tissue
Term
What kind of cells produce milk?
Definition
epithelial cells
Term
What kind of cells suround epithelial cells and what do they do?
Definition
  • myoepithelial cells suroound epithelial cells and they contract in response to oxytocin
Term
How many aveoli are there per lobule?
Definition
200
Term
What is the diameter of aveoli?
Definition
1 mm
Term
What do aveoli drain into?
Definition
small intra lobular (excretory) ducts
Term
Aveoli contain both _________ cells and _________ cells.
Definition
myoepithelial, secretory
Term
Intra-lobular ducts join to form large ______________ ducts which lead into a system of wide ____________ ducts.
Definition
interlobular, lactiferous
Term
What is the conformation of the lactiferous ducts of a cow like?
Definition
they have irregular luminal diameters and converge, in the cow, upon a single lactiferous sinus
Term
What are lactiferous sinuses sub-divided into?
Definition
a gland sinus and a teat sinus by a vascular annular ring 
Term
How do the vascular annular rings connect to the exterior?
Definition
by the narrow teat canal (also called a streak canal)
Term
What is initiation of lactation called?
Definition
lactogenesis
Term
What is the first stage of lactation?
Definition
when the aveoli gain the ability to secrete milk
Term
When does the first stage of lactation occur? How is it facilitated?
Definition
it occurs before parturition and is facilitated by enzymatic activity and differentiation of cellular organelles
Term
What is the second stage of lactation?
Definition
copious milk secretion 
Term
What five things facilitate the second stage of lactation?
Definition
  • prolactin
  • ACTH
  • estrogen
  • growth hormone (STH(somatotropin hormone))
  • very low progesterone
Term
What are prolactin levels like during gestation?
Definition
they are constant during gestation until it increases 24-48 hours before calving
Term
What is casein?
Definition
the main protein present in milk
Term
___________ and __________ allow gene expression for casein synthesis.
Definition
prolactin, glucocorticoids
Term
Why must progesterone decrease in order for lactation to occur?
Definition
because it blocks the binding sites for prolactin
Term
What does prostaglandin do?
Definition
it regresses the CL and minimizes progesterone
Term
When does estrogen reach its maximum? What does the estrogen do at this point?
Definition
it reaches a maximum 30 days before parturition and stimulates the release of prolactin
Term
What does STH (growth homrone) do just before parturition? What is its function?
Definition
it increases and it is assumed to direct nutrients to the mammary gland
Term
What is the lactation curve of cows and sheep like?
Definition
it peaks just after parturition and gradually decreases 
Term
What is the lactation curve of rabbits and rats like?
Definition
after parturition, it starts out low and then gradually increases and then it decreases again (like a parabola)
Term
What causes the decrease in milk production?
Definition
a decrease in milk secreting cells
Term
When lactation in a cow reach its peak?
Definition
2-8 weeks after parturition
Term
What six hormones are involved in the maintenance of lactation?
Definition
  • prolactin 
  • STH (growth homone)
  • thyroid hormone
  • insulin and corticoids
  • PTH (parathyroid hormone)
Term
__________ and _____________ cause the aveoli to regress and thus reduce rate of lactation.
Definition
progesterone, estrogen
Term
What are the two main stimulai for lactation by a cow?
Definition
  • the sound of milking machine or the sight of a calf causes
Term
After these stimuli, what happens and what is released?
Definition
  • the brain sends a signal to the posterior pirutiary which release oxytocin into the blood stream
Term
What happens to the oxytocin that is released into the bloodstream?
Definition
the blood transports the oxytocin to the udder where it stimulates the contraction of the tiny muscles (the myoepithelial cells) surrounding the milk-filled aveoli
Term
When do contractions occur with reference to stimulation?
Definition
20-60 seconds after the stimulation
Term
During milking, what does the squeezing action do?
Definition
it increases the intramammary pressure and forces the milk through the ducts to the gland and teat cistern
Term
How long does the action of oxtocin last? Why?
Definition
only six to eight minutes because its concentration in the blood decreases rapidly 
Term
What is the second discharge of oxytocin like?
Definition
it is usually less effective than the first one
Term
Explain the pathway from suckling to milk ejection.
Definition
  • suckling stimulates mechanorecptors in the nipple
  • this goes to the hypothalamus
  • through a nervous pathway this reaches the posterior pituitary
  • this causes oxytocin to be released which causes myoepithelial cells to contract
  • this causes milk ejection
Term
Explain the pathway from suckling to milk secretion.
Definition
  • suckling stimulates mechanoreceptors in the nipple
  • this goes to the hypothalamus
  • this causes a decrease in prolactin inhibiting hormone or an increase prolactin releasing hormone
  • this goes to the anterior pituitary where prolactin is secreted 
  • this leads to milk secretion
Term
Mamamry gland feeding is advanatageous to the __________ and the _________.
Definition
infant, female
Term
What are the four main reasons that mamamary gland feeding is advantageous?
Definition
  • there is an abundance of immune cells (B and T lymphocytes), macrophages and neutrophils
  • secretory IgA is present in great amounts in mammary gland milk
  • lactoferrin decreases the availability of harmful microorganisms
  • bifidus factor promotes nonpathogenic microorganisms in the infant's digestive tract
Term
What animal has the highest percentage of fat, protein, and solids in its milk?
Definition
sow
Term
What animal has the lowest percenatge of fat and protein in its milk?
Definition
mare
Term
What is colostrum?
Definition
first milk
Term
Colostrum is a source of __________.
Definition
immunoglobins
Term
What are some of the non-immunoglobin components of colostrum?
Definition
  • enzymes and local immunity factors (intestinal protective factors)
  • concentrated energy, proteins, vitamins, and minerals
  • fluid, warmth
Term
What are the two most importanat factors with regards to colostrum?
Definition
total immunoglobin mass and time after birth it is received 
Term
What should the total mass of immunoglobun fed be?
Definition
200-330 grams of IgG
Term
Colostrum must be fed prior to __________.
Definition
gut closure
Term
When should the first feeding of colostrum be given?
Definition
within 2 hours
Term
When should the second feeding of colostrum be given?
Definition
6-12 hours
Term
Are immunoglobin, protein, fat, lactose, calcium, and phosphorus all higher in colostrum?
Definition
yes
Term
Whjat happens to survival rate if an animal isn't fed enough colostrum?
Definition
it decreases greatly
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