Chapter 18 pregnancy, development, and lactation

Question 1

What is copulation?

Answer 1

• 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

Question 2

What does copulation trigger?

Answer 2

oxytocin release from posterior pituitary gland of the female
0xytocin causes contraction of smooth muscle of the female reproductive organs

Question 3

What is capacitation?

Answer 3

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

Question 4

What do spermatozoa do in the fertilization process?

Answer 4

• 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

Question 5

What is the zygote?

Answer 5

• 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

Question 6

What is cleavage?

Answer 6

• 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

Question 7

What is implantation?

Answer 7

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

Question 8

What is the placenta?

Answer 8

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

Question 9

In the placenta, there are layers of soft membranes that form two fluid-filled sacs around the developing fetus. What are those layers?

Answer 9

amnion
allantois
chorion

Question 10

What is the amnion in the placenta?

Answer 10

membranous layer immediately surrounding the fetus

• forms the amniotic sac
• fetus floats in amniotic fluid inside the amniotic sac

Question 11

What is the allantois in the placenta?

Answer 11

layer surrounding amniotic sac; forms the allantoic sac, which accumulates wastes

Question 12

What is the chorion in the placenta?

Answer 12

• covers the allantoic sac
• attaches to the lining of uterus
• linked to fetus by the umbilical cord

Question 13

Placental attachments varies between species, what are those attachments?

Answer 13

1. diffuse attachments
2. cotyledonary attachment
3. zonary attachment
4. discoid attachment

Question 14

What is diffuse attachments?

Answer 14

attachment sites are spread over the whole surface of the placenta and uterine lining

Question 15

What is cotyledonary attachment?

Answer 15

many small, separate attachment sites (placentome): cotyledon on placental surface joins with caruncle in the uterine lining

Question 16

The attachment type cotyledonary are found in what kind of animals?

Answer 16

ruminants (cattle, sheep, and goats)

Question 17

What is the zonary attachment?

Answer 17

belt-shaped attachment that encircles the placenta

Question 18

What animal is the zonary attachment found in the uterus?

Answer 18

cats and dogs

Question 19

What is discoid attachment?

Answer 19

placenta and uterus attached at a single disk-shaped area

Question 20

What animal is the discoid attachment found in the uterus?

Answer 20

primates, rabbits and many rodents

also Humans

Question 21

What is the gestation period?

Answer 21

time from fertilization of ovum to delivery of newborn
- time varies in different species
- divided into three segments (trimesters)
1st, 2nd, 3rd

Question 22

What is the 1st trimester in the gestation period?

Answer 22

embryonic period - placenta develops

Question 23

What is the 2nd trimester in the gestation period?

Answer 23

fetal period - body tissues, organs, and systems devleop

Question 24

What is the 3rd trimester in the gestation period?

Answer 24

fetal growth period

Question 25

What is the gestation period of cats?

Answer 25

56 - 69 days - approx. 2 months

Question 26

What is the gestation period of dogs?

Answer 26

59 - 68 days - approx. 2 months

Question 27

What is the gestation period of goats?

Answer 27

146 - 155 days - approx. 5 months

Question 28

What is the gestation period of horses?

Answer 28

321 - 346 days - approx. 11 months

Question 29

What is the gestation period of pigs?

Answer 29

110 - 116 days - approx. 3 months, 3 weeks, and 3 days

Question 30

What is the gestation period of rabbits?

Answer 30

30- 32 days - approx. 1 month

Question 31

What is the gestation period of sheep?

Answer 31

143 - 151 days - approx. 5 months

Question 32

What is the gestation period of elephants?

Answer 32

615 - 650 days - 21 months

Question 33

What is parturition?

Answer 33

- 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

Question 34

What hormone declines in the bloodstream of dam during parturition and during the pregnancy prevented fetus from prematurely expelling?

Answer 34

progesterone

Question 35

What stimulates myometrium to contract, which starts the labor process?

Answer 35

oxytocin

Question 36

There are three stages of labor, what is the first stage?

Answer 36

uterine contractions - myometrium contracts and presses fetus down against the cervix - sustained contraction cause the cervix to gradually dilate

Question 37

There are three stages of labor, what is the second stage?

Answer 37

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

Question 38

There are three stages of labor, what is the third stage?

Answer 38

delivery of the placenta | - placenta separates from wall of the uterus and is expelled by weaker uterine contractions

Question 39

What is involution of the uterus?

Answer 39

- 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

Question 40

What are mammary glands?

Answer 40

- 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 - number and appearance of mammary glands differs among common species of animals

Question 41

The udder of a cow consists of?

Answer 41

- 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

Question 42

What is mastitis?

Answer 42

infection of the mammary gland | - test for mastitis using California mastitis test

Question 43

What supports the udder that can weigh more than 100 pounds at milking time?

Answer 43

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

Question 44

How often do milk cows need to birth to keep milk flowing?

Answer 44

every other year

Question 45

What are the milk-secreting units of the mammary gland?

Answer 45

- mammary alveoli - saclike arrangement of cells that secrete milk into the alveolar duct

Question 46

The duct system of the mammary gland is similar to the arrangement of ______ in a tree.

Answer 46

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

Question 47

What causes mammary gland development?

Answer 47

- 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

Question 48

Before it starts to produce milk, the mammary gland produces a sort of premilk secretion called?

Answer 48

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

Question 49

What is the most critical of colostrums role?

Answer 49

transfer of passive immunity form the dam to the newborn

Question 50

Lactation will continue if....

Answer 50

- 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

Question 51

What stops lactation?

Answer 51

lack of hormonal stimulation combined with pressure in the mammary gland gradually causes lactation to cease - this is called involution of the mammary gland

Question 52

What is milk letdown?

Answer 52

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)