Ch 20 Pregnancy, Development, and Lactation

erection results from a ___ reflex triggered by sexual stimuli

parasympathetic

erection occurs when more blood enters the penis via the ___ than leaves it via the ___

1. enters via arteries

2. leaves via veins

hydraulic pressure

more blood enters the penis than leaves it

What is copulation?

act of breeding

What is ejaculation?

Reflex expulsion of sperm from male reproductive tract

What is the 1st stage of ejaculation?

emission - movement of sperm from epididymis & fluid from accessory repro glands into urethra

What is the 2nd stages of ejaculation?

expulsion - rhythmic contractions around urethra that pump semen

Where in the female reproductive tract does sperm deposit from ejaculation?

- typically upper portion of the vagina

- pigs and horses - directly into the uterus

How does spermatozoa get transported to oviducts?

mainly by contractions of the uterus and oviducts, action of cilia in oviducts, and oxytocin

What is capacitation?

process sperm undergo in the female reproductive tract that increases their fertility before contact w/ ovum

What changes occur during capacitation?

ion and metabolic rates changes in cells, exposure of digestive enzymes on acrosome

acrosome

digestive enzyme containing caplike structure that covers head of spermatozoa

What is fertilization?

physical entry of the head of a spermatozoa into an ovum

corona radiata

layers of cumulus cells from the follicle

zona pellucida

thick, gel-like membrane that surrounds the ovum’s cell membrane

What is a zygote?

fertilized ovum

What is the male pronucleus?

sperm nucleus, after fertilization, but before ovum & sperm nuclei come together

What is the female pronucleus?

nucleus of a fertilized ovum, before ovum & sperm nuclei come together

What is cleavage?

process of very rapid cell division after an ovum has been fertilized, rapid increase of cells, but cell stays same size

How does the zygote move into uterus?

delicate muscle contraction and cilia movements slowly and gently propel zygote down oviduct and toward uterus

What happens during morula stage of zygote development?

solid mass of cells, few days after fertilization, resembles a raspberry

What happens during blastocyst stage of zygote development?

ready for implantation in uterus, shaped like tiny hollow ball of cells with a "bump" on the side

What is implantation?

means by which the blastocyst makes itself a home by embedding itself in the endometrium of the uterus

multiparous species implantation

multiple blastocsyts randomly space themselves along the horns & body of the uterus as they implant

What is an embryo?

developing offspring during first trimester

Described the structure of placenta

multilayered, fluid filled, membranous sac that develops around embryo and is connected by the umbilical cord

Name the fluid filled sacs of placenta

1. amniotic sac

2. allantoic sac

What is the amniotic sac?

the fluid-filled sac that contains and protects a developing fetus

What is the allantoic sac?

fluid filled sac formed by the allantois that surrounds the amniotic sac

What is charion?

outer most layer of placenta, attaches to the uterine lining, linked to fetus by umbilical cord

What do the umbilical arteries do?

carry waste filled, deoxygenated blood from the fetus to the placenta

What does the umbilical vein do?

carries nutrient rich, oxygenated blood from placenta to fetus

What is the urachus?

tube in umbilical cord that drains urine from the fetus's urinary bladder into the allantioic sac of the placenta

Where do the fetal and maternal blood vessels intertwine?

where the chorion attaches to the lining of the uterus

What are the four types of placental attachment?

1. diffuse

2. cotyledonary

3. zonary

4. discoid

Describe diffuse placental attachment

• attachment sites are spread diffusely over surface of placenta

• detaches easily

diffuse placental attachment animals

horses, pigs, camelids

Describe a cotyledonary placental attachment

• most complicated

• attachment site are small, discrete and numerous (placentome)

• sometimes doesn't detach completely

cotyledonary placental attachment animals

ruminants (cattle, sheep, goats)

Describe zonary placental attachment.

• placenta attaches to uterus in a belt shaped zone that encircles the placenta

• detaches easily

zonary placental attachment. animals

1. dogs

2. cats

Describe discoid placental attachment

single, discrete, disc shaped area of attachment

Describe discoid placental attachment animals

1. humans

2. primates

3. rabbits

4. many rodents

What is gestation period?

the time from fertilization of the ovum to delivery of the newborn

trimesters

gestation divided into 3 often unequal segments

What is the first trimester?

period of embryo - organizing and developing of placenta

What is the second trimester?

fetal development period, when fetus starts taking shape - body tissues, organs and systems develop during this period

What is the third trimester?

period of fetal growth, fetus grows dramatically preparing to transition from a parasitic to a free living existence

What is parturition?

the birth process

How does the blood flow change after birth?

foramen ovale and ductus arterious must close fairly quickly

What is relaxin?

hormone released by placenta late in pregnancy

what does relaxin do

helps relax ligaments in bones around the birth canal to ease the passage of the newborn

What are the 3 stage of labor?

1. uterine contractions

2. delivery of newborn

3. delivery of placenta

uterine contractions

myometrium (muscle layer of uterus) contracts as cervix relaxes & dilates

delivery of newborn

• combo of strong uterine & abdominal muscle contractions

• rupture of amniotic & allantoic sacs of placenta

delivery of placenta

• placenta separates from the wall of the uterus

• expelled by weaker uterine contractions

What is involution of the uterus?

process of reduction in size of uterus and return to non-pregnant state

mammary glands

• specialized skin glands

• produce colostrum & milk

Where are the mammary glands located in dog, cat, swine?

inguinal, abdominal & thoracic region

Where are the mammary glands located in cattle, horse?

inguinal region

Number of mammary glands in goats, horses, sheep

2

Number of mammary glands in cattle

4

Number of mammary glands in cats & dogs

10

4 quarters in cow udder

• each quarter is different than the other 3

• have their own milk-secreting systems & ducts leading down to their own teats

mastitis

infection of mammary gland

What is mammary alveoli?

milk secreting units of mammary gland, arranged like clusters of grapes around alveolar duct

What is the mammary gland sinus?

located just dorsal to the teat, large space in mammary gland, large milk ducts empty into it

What is the teat sinus?

large space within the teat of the cow that fills with milk when milk let down occurs, looks like upside down pear

What is the streak canal?

passageway at the tip of the teat of the cow that carries milk from the teat sinus outside the body

What hormones promote mammary development?

1. prolactin

2. growth hormone

3. estrogen

4. progesterone

5. thyroid-stimulating hormone

6. adrenocorticotropic hormone

directly encourage mammary gland development

1. prolactin

2. growth hormone

stimulate ovaries to produce estrogen & progesterone during each heat cycle

1. follicle stimulating hormone FSH

2. Luteinizing hormone (LH)

encourage alveoli & duct systems of mammary glands to develop

1. estrogen

2. progesterone

influence process indirectly thru target organs (thyroid gland & adrenal cortex)

1. thyroid-stimulating hormone

2. adrenocorticotropic hormone

What is colostrum?

initial secretion of the mammary gland before milk is produced

What is colostrum made of?

rich in nutrients, has a laxative effect, contain antibodies

What is meconium?

dark, tarry material in intestine of newborn animal, first feces passed

What is the most critical role of colostrum?

passive immunity

What is lactation?

process of milk production

What is the key to continuation of lactation?

physical stimulation of the teat or nipple, combined with regular removal of milk

What is involution of mammary gland?

"drying up" of the mammary glands

What is milk let-down?

The sudden expulsion of milk after proper stimulation