6,273
edits
Changes
Jump to navigation
Jump to search
Placenta - Anatomy & Physiology (view source)
Revision as of 19:48, 11 July 2011
, 19:48, 11 July 2011→Formation
<br />
<br />
Maternal sinusoids develop from capillaries of the maternal side which anastamose with these trophoblastic lacunae. The differential pressure between the arterial and venous channels that communicate with the lacunae establishes directional flow from the arteries into the veins resulting in a uteroplacental circulation.
Maternal sinusoids develop from capillaries of the maternal side which anastamose with these trophoblastic lacunae. The differential pressure between the arterial and venous channels that communicate with the lacunae establishes directional flow from the arteries into the veins resulting in a uteroplacental circulation.
==Types of Placenta==
The physical contact surfaces used within the process of circulatory exchange are the fetal membranes and the endometrium and this exchange takes place via microscopic chorionic villi that invade the endometrium. These chorionic villi are covered by epithelium the extent and number of these contact areas forms the basis for the classification of different types of placenta.
<br />
<br />
For example, horses and pigs have many small contacts spread over the entire surface of the fetal membranes and this form of placenta is termed a ''diffuse placenta''. Ruminants have 15-120 button-like contact regions between the fetal membranes and the endometrium and this type of placenta is called a ''cotyledonary placenta''. Predatory species have chorionic villi arranged in a circular band around the fetus, called the "zona placenta".
<br />
<br />
== Exchange ==
== Exchange ==