EXAM 4: Animal Repro: Lab Gestation parturition lactation

Zygote

Diploid cell resulting from the fusion of the male and female pronuclei (syngamy)

Embryo

Organism in the early stages of development; not recognizable as a member of a specific species

Maternal recognition of pregnancy

- Necessary to prevent luteolysis

- Occurs prior to implantation/placentation

- Differs among species

1st cleavage yields a

2 celled embryo, each cell is called a blastomere and is totipotent.

Division continued rapidly until the 32 cell stage

The zygote undergoes several mitotic divisions inside the

zona pellucida (overall size does not change)

Differentiation

- Formation of three germ layers

- Formation of the extraembryonic membranes (placenta)

- Formation of organs

- Rapid changes in relative size

Three Embryonic germ layers: Ectoderm

Nervous system skin hair

Three embryonic germ layers: Mesoderm

Muscle, skeleton Cariovascular system Reproductive System

Three embryonic Germ layers: Endoderm

Digestive system, lungs. endocrine system

Yolk Sac

Originates from fetal midgut. Nutrient supply for early embryo. Absorbs uterine secretions from endometrium to stimulate early embryonic development

Amnion

Innermost membrane directly surrounding the fetus. Protects fetus from injury and provides lubrication for paturition. Prevents lung collapse and opens digestive tract

Allantois

Originates from the gut and forms the umbilcus. Supports blood vessels. Reservoir of nutrients and wastes

Chorion

Outermost membrane in direct contact with uterine tissue. Becomes vascularized by allantoic vessels. Site of hormone prodution nutrient and gas exchange

Diffuse placental shapes

Noninvasie

Cotyledonary placental shapes

Placentomes are the point of high throughput maternal/fetal ontact

Zonary/Discoid

Incasive; most direct contact between fetal and maternal blood

Placenta

Organ of nutrient and waste exchange between the fetal blood and maternal blood

Placental shape

Defines the proportion of surface area shared between fetal membranes and maternal uterine tissue where exchange occurs

Placental type

Defines the structure of cell layers separating fetal blood from maternal blood

Cow placentation

Cotyledonary / Epitheliochorial

Equine Chorionic Gonadotropin

Maintains primary CL responsible for formation and maintenance of accessory CL

Human Chorionic Gonadotropin

Maintain CL

Progesterone

In some species the placenta takes over progesterone production later in gestation.

Progesterone block

inhibits myometrail contractions

Estrogen

Peak of E2 signals preparturient period in some species

Placental lactogen

Stimulates growth of fetus and mammary glands

Relaxin

Softens connective tissue in the cervix and relaxes pelvic ligaments

Growth

Period of development from emryo to fully developed fetus prior to parturition

Calcification of Bone Matrix in bovine

70 days

Bovine tooth formation

110 days

Bovine Hair, eyes, muzzel

150 days

Bovine Extensive bone formation

180 days

Bovine Hair over entire body

230 days

Parturition

The process by which the uterus expels the products of conception

Stage I of parturition

Preparatory stage involving cervical dilation and positioning of the fetus in the virth canal via myometrial contractions

Stage II of parturition

Time of hard labor and expulsion of the fetus

Stage III

Expulsion of the placental membranes and subsequent uterine involution

Dystocia

Difficult birth

Presentation

Direction of fetal delivery, anterior posterior or transverse

Position

Orientation of the fetus

Dorsal or vental side up or lateral

Posture

Location of the legs, head, and neck

Relates to normal abnormal posture

Relative Dystocia

Normal sized calf and a small birth canal

Absolute dystocia

abnormally large calf and a normally sized birth canal

Most common cause

Hiplock

shoulders of the calf "lock" onto the bones of the pelvis during delivery

Cattle stage I last

1-4 hours (selfom notice)

Cattle stage II begins with?

Rupture of the allantochorion

Cattle stage III begins after?

Expulsion of the getus

It is crucial that the foal is born within when?

30 minutes of the beginnng of stage II. Failure to do so will most likely lead to death of the foal

ACTH

Induces parturition in response to fetal stress

Fetal cortisol

induces the release of PGF2a and produces the enzymes needed to convert placental progesterone to estradiol

Placental progesterone

maintains pregnancy and will be converted to estradiol during parturition

Estradiol

Enhances secretions of female tract and myometrial contractions as well as enhance the receptors for PGF2 alpha oxytocin

PGF2a

enhances myometrial contractions, induces luteolysis and the release/secretion of relaxin

Relaxin

relaxes pelvic ligaments allowing them to strech for expulsion of the fetus

Oxytocin

Enhances myometrial contractions produces the most foreful contractions

Inducing parturition can enhance ?

Reproductive management by controlling the time of parturition

Hormones required for lactation

1. Estrogen: stimulates duct growth

2. Progesterone: stimulates alveolar development

3. Growth Hormone (somatotropin): stimulates milk production

4. Thyroid Hormones: enhance development and function of mammary

tissue

5. Corticoids: enhance synthesis of enzymes necessary for milk

biosynthesis

6. Prolactin: initiation of lactogenesis

7. Oxytocin: stimulate myometrial contractions to release milk from

alveoli to ducts

8. Insulin: maintain function and survival of secretory cells

9. Placental Lactogen: general mammary tissue growth

Tissue of mammary gland

-Secretory cells

-Alveoli

-Myoepithelial cells

-Ducts

-Blood Vessels

What is the placenta shape in primates

Discoid