Initial vascularisation in the pig placenta: II. Demonstration of gland and areola-gland subunits by histology and corrosion casts.
Tissues from 10 pregnant pigs between 9 1/2 and 43 days post coitum (p.c.) were prepared for histology and vascular corrosion casts to examine the vascularisation of the gland and areola-gland subunits of the early pig placenta. The endometrial vascular networks shown by casts were equal in both glandular and interglandular fields from days 9 1/2 to 14-15 p.c. This represents a cyclic stage uninfluenced by the early implanting embryo on day 13 p.c. By day 15 p.c., the first areola formation was observed both histologically and on casts. The maternal areolar and glandular capillary network developed into a widely meshed loose type, in contrast to the interareolar type which had a dense and parallel architecture. In some cases extremely large, crooked, and highly anastomosed maternal capillaries developed between these two networks. This specialized transition is thought to form the base for the ring-like seal formation (RSF) of the areolar periphery. A firm materno-fetal anchor therefore "seals" the areola and its glandular secretory contents from its interareolar surroundings. Therefore, the glandular and maternal areolar vasculatures are clearly discernable from that of the fetal areolar vasculature. The former are associated with the known maternao-fetal substance transfer of the porcine areolar-gland subunit. This association, however, seems to remain unspecialized in early placentation, as only the regular roundish areola--not the irregular areola--can be distinctly detected.
Leiser
R
R
Institute of Veterinary Anatomy, Histology, and Embryology, Justus-Liebig-University, Giessen, Germany.
Dantzer
V
V
D000818:Animals; D001808:Blood Vessels / Q000033:anatomy & histology; D016319:Corrosion Casting; D005260:Female; D008855:Microscopy, Electron, Scanning; D010920:Placenta / Q000098:blood supply*; D010929:Placentation; D011247:Pregnancy; D013552:Swine / Q000033:anatomy & histology*