Explain how the ascending limb of the nephron loop creates the concentration gradient of salts in the renal medulla.
The entire ascending limb is impermeable to water. Na and Cl diffuse out of the thin segment of the asc limb. THe thick segment actively transports Na and Cl outward. The outward movement of salts creates the solute concentration of the renal medulla
Describe the 6 functions of the digestive system.
Mechanical processing- tearing, crushing of food
Digestion- chemical breakdown of food
Secretion- secretes acids and enzymes into GI tract
Absorption- nutrients and water
Excretion- discharge of wastes
Protection- against bacteria and corrosive effects
Explain 3 structural features of the small intestine that lead to an enormous surface area.
Plicae are small permanent folds lining the small intestine that increase surface area. The plicae, villi, and microvilli together give us a small intestine with tremendous surface area.
Describe the 4 functions of the large intestine.
Reabsorption of water and compaction of intestinal contents into feces. Absorption of vitamins liberated by bacterial action. Absorption of some organic wastes. Temporary storage of fecal material.
Explain the 2 key differences between meiosis in the ovary versus in the testes.
The cytoplasm of the primary oocyte is unevenly distributed during the 2 meiotic divisions. The ovary releases a secondary oocyte, whereas the testes release spermatozoa.
Describe in detail the milk let-down reflex.
Neuroendocrine reflex when the infant's sucking stimulates nerve endings of the nipple and areola, which in turn signal the hypothalamus and posterior pituitary to release oxytocin. Oxytocin stimulates myoepithelial cells which squeeze milk to duct.
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