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Pregnancy and Parturition - Horse Anatomy (view source)
Revision as of 17:35, 26 November 2012
, 17:35, 26 November 2012no edit summary
Oxygen and nutrient rich blood returns to the foetus via the '''umbilical vein'''. Maternal blood is supplied to the placenta via 80-100 '''spiral endometrial arteries''' which allow the blood to flow into intervillous spaces facilitating exchnage. The blood pressure within the spiral arteries is much higher than that found in the intervillous spaces resulting in more efficient nutrient exchange within the placenta.
Oxygen and nutrient rich blood returns to the foetus via the '''umbilical vein'''. Maternal blood is supplied to the placenta via 80-100 '''spiral endometrial arteries''' which allow the blood to flow into intervillous spaces facilitating exchnage. The blood pressure within the spiral arteries is much higher than that found in the intervillous spaces resulting in more efficient nutrient exchange within the placenta.
===Exchange===
====Exchange====
The mare is not able to confer immunity via the placenta and instead relies on the passive transfer of antibodies via '''colostrum'''.
The mare is not able to confer immunity via the placenta and instead relies on the passive transfer of antibodies via '''colostrum'''.
====Histotrophic Exchange====
=====Histotrophic Exchange=====
This type of exhange facilitates nourishment of the embryo prior to implantation, i.e. where no placenta exists. In horses, this type of exchnage is very important as there is a long period prior to implantation (up to 35 days). Nutrition is supplied by uterine secretions/debris, often referred to as 'uterine milk'. Uterine milk secretions are usually maintained by '''progesterone'''. Pinocytosis (cellular drinking) is the main exchange mechanism.
This type of exhange facilitates nourishment of the embryo prior to implantation, i.e. where no placenta exists. In horses, this type of exchnage is very important as there is a long period prior to implantation (up to 35 days). Nutrition is supplied by uterine secretions/debris, often referred to as 'uterine milk'. Uterine milk secretions are usually maintained by '''progesterone'''. Pinocytosis (cellular drinking) is the main exchange mechanism.
====Haemotrophic Exchange====
=====Haemotrophic Exchange=====
This type of exchnage utilises direct transfer of nutrients from the maternal to foetal blood via simple diffusion, facillitated diffusion, active transport and complex diffusion.
This type of exchnage utilises direct transfer of nutrients from the maternal to foetal blood via simple diffusion, facillitated diffusion, active transport and complex diffusion.
====Placental Blood Supply and Drainage====
=====Umbilical Arteries=====
The paired umbilical arteries arise from '''Iliac arteries''' along with vesicular arteries to the bladder. In the adult, the remnance of these vessels form the ventral ligament of the bladder. The umbilical arteries carry deoxygenated blood and waste products from the foetus to the placenta.
=====Umbilical Veins=====
A single umbilical veins runs from the fetus and joins the '''hepatic portal vein''', effectively circumventing the liver which is not yet fully patent. The umbilical vein transports oxygen-rich and nutrient-rich blood from the placenta to the fetus.
=== Shunts ===
There are a number of foetal circulatory shunts that are related to the umbilical arteries and veins. The three major shunts are covered in more detail at [[Foetal_Circulation_-_Anatomy_%26_Physiology#Circulatory_Changes_at_Birth|Foetal Circulation]] but are important to ensure that organs are always supplied with oxygen and nutrient rich blood, to prevent waste accumulation and protect organs that are not yet fully patent. The main foetal circulatory shunts are the '''Ductus venosus''', '''Foramen ovale''' and the '''Ductus arteriosus'''.
==Parturition==
==Parturition==