Bird, uterus (LM, Low)

Structure List Columnar epithelium Lamellae Lumen Circular muscle Tract Diagram View

UTERUS (SHELL GLAND) OF BIRDS. The oviduct of birds has five parts. The uterus is a sack-like region that does not have a distinct demarcation from the isthmus. It has longitudinal folds of mucosa, called lamellae, which are lined by pseudostratified, columnar epithelium with cilia. When an egg is in the uterus, the lamellae are flat against the developing shell. The egg occupies the uterus for about 20 hours. During the first 8 hours most of the activity is the addition of water, leading to a doubling of the weight of the albumen. During the last 12 hours, the shell is calcified by the secretion of calcium from the glands.