Placentation

whta is a zonary placenta and who has it

cat and dog

band of connection across the middle of the foetus chorion

how does the horse MRP happen

1. cycles around the uterus body and horns to distribute prostaglandins and other pregnancy factors across the whole endometrium

   1. trophoblasts form the chorionic girdle betwene the regressing yok sac and allantois which invade the endometrium to form endometrial cups to secrete equine gonadotrophin which causes ovulation and a second CL between days 60-100 but this wasn’t fertilised as the right hormones weren’t in place for oestrus, and the CL secretes progesterone to sustain the pregnancy

how does the sow MRP happen

1. foetus secretes oestradiol from 11-12 days to cause PGF2a secretion to be directed to the uterine lumen and not the submucosal vessels for the ovary so switches from an endocrine to exocrine function

2. oestradiol promotes uterine contractions to help for equal distribution of conceptuses in each horn (at least 2 per horn)

overall is a faster process

what are the three types of microanatomy of placenta

epitheliochorial

endotheliochorial

haemochorial

what are the 4 roles of the placenta

foetal nourishment - gas exchange and nutrient transfer

waste removal of urea and creatinine - not creatine

protection - pathogens in circulation

endocrine function - progesteron, eCG and oestrogen to maintain the pregnancy

3 maternal layers of the placenta

1.       Internal epithelial lining of the endometrium

2.       Maternal CT lining surrounding the vessels of the endometrium

3.       Maternal endothelium lining the blood vessels connecting to maternal circulation

3 foetal layers of the placenta

1.       Chorionic epithelium which is the surface of the chorionic allantois, and divided into chorionic villi

2.       Matrix of foetal CT of the chorioallantois which is the mesoderm surrounding the blood vessels

3.       Foetal endothelium lining the allantoic/chorionic capillaries connecting to foetal circulation

what forms the placental connection in the mother and foetus

mother - endometrium (mucosa of uterus)

foetus - chorioallantois from trophoblasts and mesoderm

what sort of placenta does a horse have

epitheliochorial microcotyledonary diffuse

what sort of placenta does a rodent have

haemochorial discoid - maternal is concave and foetus is convex

what is the point of the umbilical cord

connect the foetus to the placenta

when does the embryo attach to the endometrium in the pig

11-12 days (same as point of oestradiol secretion)

when does the sheep attach to the endometrium

15-18 days