AP BIOLOGY

ANIMAL PHYSIOLOGY

EXCRETION

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
The ____ are made up of millions of ____
A
kidneys, ureters
B
nephrons, kidneys
C
lungs, nephrons
D
kidneys, nephrons
Explanation: 

Detailed explanation-1: -Each of your kidneys is made up of about a million filtering units called nephrons. Each nephron includes a filter, called the glomerulus, and a tubule. The nephrons work through a two-step process: the glomerulus filters your blood, and the tubule returns needed substances to your blood and removes wastes.

Detailed explanation-2: -Whereas the studies agree that average nephron number is approximately 900, 000 to 1 million per kidney, numbers for individual kidneys range from approximately 200, 000 to >2.5 million.

Detailed explanation-3: -Each nephron is composed of a renal corpuscle (glomerulus within Bowman’s capsule), a proximal tubule (convoluted and straight components), an intermediate tubule (loop of Henle), a distal convoluted tubule, a connecting tubule, and cortical, outer medullary, and inner medullary collecting ducts.

Detailed explanation-4: -Cortical nephrons (the majority of nephrons) start high in the cortex and have a short loop of Henle which does not penetrate deeply into the medulla. Cortical nephrons can be subdivided into superficial cortical nephrons and midcortical nephrons.

Detailed explanation-5: -The nephrons found in the kidneys (mesonephros) of amphibians and most fish, and in the late embryonic development of more advanced vertebrates, are only slightly more advanced in structure. The most advanced nephrons occur in the adult kidneys, or metanephros, of land vertebrates, such as reptiles, birds, and mammals.

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