Vitamin A (retinol) is essential for the synthesis of rhodopsin (visual pigment in rod cells) and maintenance of epithelial tissues. Deficiency causes night blindness (nyctalopia), xerophthalmia, and ultimately permanent blindness. Bone development is related to vitamin D and calcium. Blood clotting is vitamin K, energy metabolism involves B vitamins. Thus, vision is primarily affected.
Explanation:
About 70% CO₂ is carried as bicarbonate. The main stimulus is high CO₂; external respiration is in lungs; diaphragm moves downward (contracts) during inhalation.
Explanation:
The diaphragm is a dome-shaped skeletal muscle that separates the thoracic cavity (lungs, heart) from the abdominal cavity. It is the primary muscle of inspiration. Pleura lines lungs, peritoneum lines abdomen.
Explanation:
Neurulation involves the folding of the neural plate to form the neural tube, which becomes the brain and spinal cord. Gastrulation forms germ layers.
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