Flexion- bending of the embryo along the anterior-posterior axis. In amniotes the tip of the head bends towards the heart. Types of flexion: cranial flexion, cervical flexion, pontine flexure, dorsal flexure, caudal flexure.
^Cervical flexure- ventral bend in embryo at transition between myelencephalon and spinal cord
^Dosal Flexure- a ventral bend in the midbody making the back confex
^Pontine flexure- a ventral bend in the head region between the metencephalon and the myelencephalon. Visible in 120 hour chick embryo (5 day).
^cranial flexure- ventral bend at mesencephalon
Amnion- fluid –filled sac that is one of the 3 extra-embryonic membranes. Fromed from somatopleure. Sourround embryo.
Chorion- one of the three extracellular membranes in amniotes. Functions in gas exchange in birds and reptiles. In mammals it is derived from trophoblast and becomes part of the placenta.
Rathke’s pouch- dorsal ectoderm evagination from stomodeum that gives rise to the anterior pituitary gland
Aortic Arch- six pariered arteries emanating from the aortic sac and transversing though the pharyngeal arches (1, 2, and 5 degenerate)
AER (Apical ectodermal ridge)- thickened ridge on anterior-post surface of limb bud
Torsion- twisting of the embryo along the left-right axis (similar to the twist of the body when a golfer swings at the ball). MOST prominent in the 48-hour chick embryo
Flexion- bending of the embryo along the anterior-posterior axis. In amniotes the tip of the head bends towards the heart. Types of flexion: cranial flexion, cervical flexion, pontine flexure, dorsal flexure, caudal flexure.
^Cervical flexure- ventral bend in embryo at transition between myelencephalon and spinal cord
^Dosal Flexure- a ventral bend in the midbody making the back confex
^Pontine flexure- a ventral bend in the