Gestation

Question 1

Review of fertilisation and implantation

Answer 1

Sperm capacitation 
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Hyperactivation
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Binding to zona pellucida
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Acrosome reaction
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Penetration of zona pellucida
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Sperm – Oocyte binding Fertilisation
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Zygote cleavage 
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Blastocyst formation and hatching

Question 2

Maintenance of pregnancy

Answer 2

• Progesterone is required to maintain pregnancy
• Progesterone secreted by the corpus luteum (CL) throughout
pregnancy in some species
• The placenta takes over the secretion of progesterone during gestation in some species
• Increase in the oestrogen:progesterone ratio induces parturition

Question 3

Placenta

Answer 3

• Diverse range of placental structures
• Classified by extent and type of attachment, distribution of chorionic villus,
shape, type of implantation.
• Facilitate gas and nutrient exchange and endocrine support for the developing embryo and foetus

Question 4

Foetal membranes

Answer 4

• There are four foetal membranes in mammals. 1. chorion
2. yolk sac 3. amnion 4. allantois
• They are derived from the zygote. Their main functions are to isolate and protect the foetus and to form the placenta.

Question 5

Foetal Membranes

Answer 5

• Two types of foetal membranes that form: Choriovitelline (Non mammals and marsupials) Chorioallantoic (ruminants, pigs)
• Horses, carnivores and rodents are Choriovitelline then chorioallantoic

Question 6

Choriovitelline

Answer 6

A choriovitelline placenta is a placenta formed by the yolk sac and chorion. In a choriovitelline placenta, the yolk sac fuses with the chorion and subsequently wrinkles develop that hold the embryo to the uterine wall and the embryo, thus forming the choriovitelline placenta.

Question 7

Chorioallantoic

Answer 7

A placenta in which the allantoic mesoderm and vessels fuse with the inner face of the serosa to form the chorion.

Question 8

Horses, carnivores and rodents are

Answer 8

Choriovitelline then chorioallantoic

Question 9

Placental type 2; Shape and point of villous contact

Answer 9

• Discoid (rodents)
• Cotyledonary (ruminants)
• Zonary (dogs and cats)
• Diffuse (horses and pigs)

Question 10

Discoid

Answer 10

A placenta in which part of the chorion remains smooth, while the other part interacts with the endometrium to form the placenta. The maternal blood cells are in direct contact with the fetal chorion.

Question 11

• Cotyledonary

Answer 11

A type of chorioallantoic placenta in which the villi are grouped into tufts or balls separated by regions of smooth chorion

Question 12

Zonary

Answer 12

The placenta takes the form of a complete or incomplete band of tissue surrounding the fetus. Seen in carnivores like dogs and cats, seals, bears, and elephants

Question 13

Diffuse

Answer 13

a placenta made up of villi diffusely scattered over almost the whole surface of the chorion (as in whales, swine, and horses)

Question 14

maternal; Foetal interface

Answer 14

The maternal-fetal interface is composed of the maternally derived decidua and the fetally derived placenta (Fig. 1). In both mice and humans, the placenta develops from the trophectoderm of the blastocyst. During implantation, invading trophoblasts anchor the blastocyst to the specialized uterine epithelium (the decidua), on which placentation ensues.

Question 15

Foetal membranes of the dog

Answer 15

• choriovitelline then chorioallantoic, • zonary, central,

* endotheliochorial

Question 16

Mammary Gland

Answer 16

• Structure of mammary gland, supportive tissues, circulation
• Species diversity
• Hormonal control of mammogenesis, lactogenesis, galactopoiesis • Mechanism of milk ejection
• Milk composition and its affecting factors

Question 17

Streak canal

Answer 17

-Functions to keep milk in udder and bacteria out of udder

Question 18

Teat cistern

Answer 18

• Duct in teat with capacity of 30-45 millilitres. Separated from streak canal by folds of tissue called Furstenberg’s rosette

Question 19

Gland cistern

Answer 19

Separated from teat cistern by the cricoid fold. Holds up to 400 millilitres of milk, collecting area for the mammary ducts

Question 20

Lactogenesis

Answer 20

The onset of milk secretion, changes in oestrogen and progesterone concentrations and prolactin upon expulsion of the placenta

Question 21

Galactopoiesis

Answer 21

The maintenance of lactation, stimulated by suckling and prolactin hormone

Question 22

Involution

Answer 22

Termination of milk secretion and mammary gland regression

Question 23

Parturition

Answer 23

• Process by which conceptus is expelled from the uterus (Conceptus consists of foetus, placenta and foetal membranes)
• Parturition requires Cervical remodelling
• Initiated by foetus by activation of foetal HPA axis
• Co-ordinated
• Uterine contractions regulated by Oxytocin and prostaglandins F2α • Delivery of placenta regulated by Oxytocin

Question 24

Stages of labour.

Answer 24

Stage 1: Contractions and cervical dilation
Stage 2: Foetal Expulsion
Stage 3: Placental Expulsion

Question 25

Regulation of parturition

Answer 25

Foetal stress stimulates release of cortisol (from foetus)
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prostaglandins and oestrogen> oxytocin
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Myometrial contractions increase and Cervical softening luteolysis
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Pressure increase
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cervical stimulation
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oxytocin> Myometrial contractions increase

Question 26

Myometrium

Answer 26

consists of non-striated smooth muscle fibres with gap junctions to create a syncytium

• Muscle cell hypertrophy x10 during pregnancy under influence of oestrogen

Question 27

Two hormones directly regulate myometrial contraction

Answer 27

• Oxytocin Lowers the excitation threshold of muscle cells

* Prostaglandins Stimulates liberation of Calcium ions from intracellular stores

Question 28

Brachystasis

Answer 28

fibres contract but remain shortened on relaxation gradually shortening the uterus