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.fetus implanted in the wall of the uterus,uterus receives nutrients and oxygen from the mother's blood and passes out waste.blood filters out some substances which could harm the fetus. produces progesterone, which is important in maintaining the pregnancy; estrogen, and other hormonesprogesteroneestrogen delivered after the fetus,and is called the afterbirth. Non-placental mammals Monotremes and marsupials-egg-laying mammals found in Australia and New Guinea, Monotremes AustraliaNew Guinea Birds are non placental

Amniotic sac Tough, thin, transparent pair of membranes, which hold a developing fetus.fetus The inner membrane, the amnion, contains the amniotic fluid and the fetus.amnion The outer membrane, the chorion, contains the amnion and is attached to the placenta.chorionplacenta

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.

Type of PlacentaCommon Examples DiffuseHorses and pigs Cotyledonary Ruminants (cattle, sheep, goats, deer) ZonaryCarnivores (dog, cat, ferret) Discoid Humans, apes, monkeys and rodents

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 membranesCross-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 days180 days 18-23cm 7-9in large cat size hair on eyebrow and lips cm (15-24 in ) hair on inside of the ear, around the horn pits tip of tail, & muzzle.

210 days240 days in long hair on tip of tail Hair on the metatarsal, metacarpal and phalangeal region in Fine short hair all over the body Incisor teeth not erupted

210 days

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

Cattle Gestation – 283 days

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!