Animal Gestation

Gestation-Unit 6 Frameworks Objectives

6.1 Define Terms

6.3 Describe female reproductive systems

6.3 Label reproductive parts

Comparative analysis of sheep and pig uterus

Gestation in Animals

Review these Terms: Embryo Fetus Gestation Parturition Open Bred Settled

We will define these together: Placenta Amniotic Sac Amniotic fluid Chorion Amnion Umbilical Cord Cotyledon Caruncle placentome

Gestation Periods in Animals

Mare – 336 Cow – 283 Ewe – 150 Sow – 114 Gyp - 63

The Placenta – a temporary organ present only in female placental mammals during gestation.

composed of two parts, one is part of the fetus, the other part of the mother.

implanted in the wall of the uterus, receives nutrients and oxygen from the mother's blood and

passes out waste. filters out some substances which could harm the fetus. produces progesterone, which is important in maintaining the

pregnancy; estrogen, and other hormones delivered after the fetus ,and is called the afterbirth.

Non-placental mammals Monotremes and marsupials-egg-laying mammals found in

Australia and New Guinea, Birds are non placental

Amniotic sac

Tough, thin, transparent pair of membranes, which hold a developing fetus.

The inner membrane, the amnion, contains the amniotic fluid and the fetus.

The outer membrane, the chorion, contains the amnion and is attached to the placenta.

The Umbilical Cord

Attaches the placenta to the fetus The site of the former umbilical cord

attachment is the umbilicus,

or navel.

Placental Classifications

Classification is based on:

1. Shape

2. The number of layers of tissue between maternal and fetal vascular systems.

http://arbl.cvmbs.colostate.edu/hbooks/pathphys/reprod/placenta/plac_types.jpg

Type of Placenta Common Examples

Diffuse Horses and pigs

CotyledonaryRuminants (cattle, sheep,

goats, deer)

Zonary Carnivores (dog, cat, ferret)

DiscoidHumans, apes, monkeys and

rodents

http://arbl.cvmbs.colostate.edu/hbooks/pathphys/reprod/placenta/structure.html

Diffuse Placenta – Equine and Porcine

Attached smoothly to entire uterus

Equine Placenta with fetus

Cotyledonary Placenta - Ruminants Multiple areas of attachment

called cotyledons.

Cotyledons - fetal portions of this type of placenta

Caruncles - maternal contact sites

Placentome - cotyledon-caruncle complex

Cotoledenary Placenta – Uterus Partially Removed

Caruncles

In membranes Cross-section

Cotyledon: the fetal side of the placenta

Caruncle: the maternal side of the placenta

Placentome: a cotyledon and caruncle together

Zonary Placenta – Dogs, Cats…

Placenta is attached in band-like zones in the uterus.

This image shows the end of one uterine horn of the cat.

The zonary placenta of two fetuses are clearly visible through the uterine wall.

Uterus Removed

Chorioallantois Removed

Placenta Opened, showing vascular structure

Discoid Placental Attachment

Primates Rodents

Review – Quiz

Name an animal with each type of placenta:

1. Cotelydonary 2. Discoid 3. Zonal 4. Diffuse

Bonus – what type of placenta do humans have.

Fetal Development

Cattle - 60 DAYS

21/2-3IN CLAW BUDS and SCROTUM

RECOGNIZABLE PALATE and STERNUM

CLOSED

PLACENTA ATTACHED

COTYLEDONS PRESENT.

Cattle 90 days

5-7 INCHES RAT SIZE FINE HAIR ON

EYEBROWS CLAWS DEVELOPED Cotyledons PRESENT

ON AMNION HORN PITS PRESENT

• 5-7in small cat size find hair on eyebrow claws develop

150 days 180 days

18-23cm 7-9in large cat size hair on eyebrow and

lips

40-60 cm (15-24 in ) hair on inside of the

ear, around the horn pits tip of tail, & muzzle.

210 days 240 days

22-30 in long hair on tip of tail Hair on the metatarsal,

metacarpal and phalangeal region

24-34 in Fine short hair all over

the body Incisor teeth not

erupted

210 days

70-100 cm (28-40 in ) Hair coat complete incisor teeth erupted

Cattle Gestation – 283 days

28 day pig embryos

28 day pig embryos

60 day old pig embryo

Relaxin: protein hormone that acts with progesterone to maintain pregnancy and to promote loosening of pelvic ligaments at the time of parturition.

One of the first signs of birth is the water bag.

First sign of the calf should be two front legs facing downward.

Parturition!