Adenohypophyseal pouch, which will develop into the anterior pituitary, is defined. Lens vesicle opens to the surface and is nestled within the otptic cup. Otic vesicle increases its size by approximately one-fourth and its endolymphatic appendage is more defined. Nasal plate can be detected by thickened ectoderm. Thorax Esophagus, the tube through which food is swallowed, forms from a groove of tissue that separates from the trachea, which is also visible.
Semilunar valves begin to form in the heart.
Right and left lung sacs lie on either side of the esophagus. Abdomen and Pelvic Regions Ureteric bud appear. Metanephros, which will eventually form the permanent kidney, is developing. Limbs Upper limbs elongate into cylindrically-shaped buds, tapering at tip to eventually form hand plate. Nerve distribution process, innervation, begins in the upper limbs.