Chapter 18 pregnancy, development, and lactation Flashcards
What is copulation?
- the act of breeding -mounting
- intromission - insertion of penis into the vagina
- thrusting and ejaculation (semen is usually deposited in the upper portion of the vagina) - spermatozoa transported by swimming, by contractions of uterus and oviducts, and by action of cilia in oviducts
What does copulation trigger?
oxytocin release from posterior pituitary gland of the female
0xytocin causes contraction of smooth muscle of the female reproductive organs
What is capacitation?
series of changes that spermatozoa undergo in the female reproductive tract to increase changes of successfully fertilizing the ovum
- changes in ion movement through the cell
membranes; increase in cells metabolic rates
- release of digestive enzymes from acrosome
- help the spermatozoa penetrate through
layers surrounding the ovum to accomplish
fertilization
What do spermatozoa do in the fertilization process?
- large number of spermatozoa find and swarm around the ovum in the oviduct
- some begin tunneling through the layers surrounding the ovum - aided by digestive enzymes of their acrosomes
- once a single spermatozoon penetrates cell membrane of the ovum, a change in the membrane blocks other sperm from entering
What is the zygote?
- once the ovum is fertilized, it gets another name change and becomes a zygote
- immediately after fertilization the nucleus of the
spermatozoon is called the male pronucleus; - the nucleus of the ovum is called the female
pronucleus - each pronuclues contains the haploid chromosome
number - male and female pronuclei join together - restores the diploid chromosome number
What is cleavage?
- rapid mitosis of zygote
- overall size of zygote does not change
- morula stage - solid mass of cells
- blastocyst - hollow ball of cells - ready to implant
itself in the lining of the uterus
What is implantation?
when the enzymes produced by the blastocyst dissolve away a small pit in the endometrium. - blastocyst attaches to endometrium in this pit
- in multiparous species, the multiple blastocysts randomly space along the horns and body of the uterus
- placenta begins to form as soon as the blastocyst implants in the uterus
What is the placenta?
a life support system for the developing fetus
- multilayered, fluid-filled, membranous sac
- outermost layer of placenta attaches to uterine lining in some areas
- fetal and maternal blood vessels are in close proximity to each other in this area
- site of exchange of blood nutrients and wastes
In the placenta, there are layers of soft membranes that form two fluid-filled sacs around the developing fetus. What are those layers?
amnion
allantois
chorion
What is the amnion in the placenta?
membranous layer immediately surrounding the fetus
- forms the amniotic sac
- fetus floats in amniotic fluid inside the amniotic sac
What is the allantois in the placenta?
layer surrounding amniotic sac; forms the allantoic sac, which accumulates wastes
What is the chorion in the placenta?
- covers the allantoic sac
- attaches to the lining of uterus
- linked to fetus by the umbilical cord
Placental attachments varies between species, what are those attachments?
- diffuse attachments
- cotyledonary attachment
- zonary attachment
- discoid attachment
What is diffuse attachments?
attachment sites are spread over the whole surface of the placenta and uterine lining
What is cotyledonary attachment?
many small, separate attachment sites (placentome): cotyledon on placental surface joins with caruncle in the uterine lining
The attachment type cotyledonary are found in what kind of animals?
ruminants (cattle, sheep, and goats)
What is the zonary attachment?
belt-shaped attachment that encircles the placenta
What animal is the zonary attachment found in the uterus?
cats and dogs
What is discoid attachment?
placenta and uterus attached at a single disk-shaped area
What animal is the discoid attachment found in the uterus?
primates, rabbits and many rodents
also Humans
What is the gestation period?
time from fertilization of ovum to delivery of newborn
- time varies in different species
- divided into three segments (trimesters)
1st, 2nd, 3rd
What is the 1st trimester in the gestation period?
embryonic period - placenta develops
What is the 2nd trimester in the gestation period?
fetal period - body tissues, organs, and systems devleop
What is the 3rd trimester in the gestation period?
fetal growth period
What is the gestation period of cats?
56 - 69 days - approx. 2 months
What is the gestation period of dogs?
59 - 68 days - approx. 2 months
What is the gestation period of goats?
146 - 155 days - approx. 5 months
What is the gestation period of horses?
321 - 346 days - approx. 11 months
What is the gestation period of pigs?
110 - 116 days - approx. 3 months, 3 weeks, and 3 days
What is the gestation period of rabbits?
30- 32 days - approx. 1 month
What is the gestation period of sheep?
143 - 151 days - approx. 5 months
What is the gestation period of elephants?
615 - 650 days - 21 months
What is parturition?
- birth process
- multiple factors trigger parturition
- size and weight of uterus
- hormonal changes
- fetal changes at birth
- lungs expand and start functioning
- formamen ovale and ductus arteriosus close
- increased level of glucocorticoid hormones from
adrenal glands of fetus stimulate estrogen level
increase in dam and release of prostaglandin
F2a (alpha) - oxytocin released from dam’s posterior pituitary gland
What hormone declines in the bloodstream of dam during parturition and during the pregnancy prevented fetus from prematurely expelling?
progesterone
What stimulates myometrium to contract, which starts the labor process?
oxytocin
There are three stages of labor, what is the first stage?
uterine contractions
- myometrium contracts and presses fetus down against the cervix
- sustained contraction cause the cervix to gradually dilate
There are three stages of labor, what is the second stage?
delivery of the newborn
- results from combination of strong uterine and abdominal muscle contractions
- rupture of amniotic and allantoic sacs of the placenta usually precedes actual delivery of the newborn
There are three stages of labor, what is the third stage?
delivery of the placenta
- placenta separates from wall of the uterus and is expelled by weaker uterine contractions
What is involution of the uterus?
- uterus gradually returns to its nonpregnant size
- endometrium sloughs into lumen of uterus at sites of placental attachment
- myometrium continues mild contractions to move remaining uterine contents out through birth canal
- may take from a few weeks to a month or more for involution to be complete
What are mammary glands?
- specialized skin glands
- produce colostrum and milk
- present in both male and female animals
- males do not secrete the proper blend of
hormones to make them work
- males do not secrete the proper blend of
- number and appearance of mammary glands
differs among common species of animals
The udder of a cow consists of?
- 4 mammary glands (quarters
- Quarters are completely separate units from each
other - each quarter has its own milk- secreting systems
and ducts leading down to separate teats
What is mastitis?
infection of the mammary gland
- test for mastitis using California mastitis test
What supports the udder that can weigh more than 100 pounds at milking time?
Medial suspensory ligament - many elastic fibers -
passes between left and right halves of the udder
- lateral suspensory ligaments - strong inelastic
collagen fibers - pass down and around the lateral
sides of each half of the udder
How often do milk cows need to birth to keep milk flowing?
every other year
What are the milk-secreting units of the mammary gland?
- mammary alveoli - saclike arrangement of cells that secrete milk into the alveolar duct
The duct system of the mammary gland is similar to the arrangement of ______ in a tree.
branches
- arranged like clusters of grapes around the alveolar ducts are similar to the leaves
- smaller alevolar ducts joint to form larger ducts similar to small tree branches joining to form larger branches
- largest ducts empty into the gland sinus located just dorsal to the teat similar to the trunk of a tree
- gland sinus is continuous with the teat sinus
inside the teat
- the gland sinus and teat sinus are where milk
accumulates when milk letdown has occurred
What causes mammary gland development?
- mammary glands develop in response to hormones produced at puberty
- prolactin and growth hormone directly encourage mammary gland development
- estrogen and progesterone encourage the mammary alveoli and duct systems to develop
Before it starts to produce milk, the mammary gland produces a sort of premilk secretion called?
colostrum
- contains large amounts of proteins, lipids, amino
acids, and vitamins
- supplies important nutrients to the newborn
- laxative effect helps clear (dark, sticky) meconium from newborn’s intestinal tract
- imparts “passive immunity” - transfer of preformed
antibodies from dam to newborn
What is the most critical of colostrums role?
transfer of passive immunity form the dam to the newborn
Lactation will continue if….
- physical stimulation of teat or nipple and regular
removal of milk from the gland stimulates anterior
pituitary to continue production of hormones that
keep lactation going
What stops lactation?
lack of hormonal stimulation combined with pressure in the mammary gland gradually causes lactation to cease - this is called involution of the mammary gland
What is milk letdown?
immediate effect of nursing or milking
- milk accumulates high up in the mammary gland in
mammary alveoli and small ducts
- physical stimulation of the nipple or teat sends
sensory nerve impulses that cause release of
oxytocin from posterior pituitary
- oxytocin casues contraction of myoepithelial cells
around the alveoli and small ducts
- moves milk down into the large ducts and
sinuses (milk letdown has occurred)
