Page 511 - Anatomy and Physiology of Farm Animals, 8th Edition

496 / Anatomy and Physiology of Farm Animals

(A)
VetBooks.ir

(B)

Figure 28-6. Singleton bovine pregnancies at approximately 38 days (A) and 54 days (B). In (A), the
visible ovary (a) has a corpus luteum, and the cervix (c) is closed. Early placentome formation is evident,
with maternal caruncles (b) and fetal cotelydons (d); the chorion has been removed to demonstrate the
allantois; the amnion (e) is evident encircling the fetus. In (B), the chorion is intact with obvious fetal
villi (*) that will project into the maternal endometrium demonstrating the typical arrangement of the
placentomes. Source: images courtesy of Library of Reproduction Images (LORI: http://lorimainsection.
blogspot.ca).

of the caruncle to contain crypts for the placenta, is shed at the time of parturition.
attachment of the chorionic villi (Fig. 28‐5). Most domestic animals have an indecidu-
Hemochorial placentas are usually ate placenta, in which little or no maternal
attached to the uterus in a disk‐shaped tissue is lost at parturition.
area only. Hence the term discoidal is used
to describe their general area of attach-
ment. The endotheliochorial placenta of Hormones of Pregnancy
carnivores is attached in a girdle‐like band,
so the attachment is known as zonary. The Progesterone
discoidal and zonary types of placental
attachment are deciduate, since a portion Progesterone has several actions that are
of the maternal endometrium, or maternal essential for maintaining a normal pregnancy.