Human Excretory System: Kidneys and Their Exterior Aspects -
- Kidneys are reddish-brown, bean-shaped structures situated between the levels of last thoracic and third lumbar vertebra.
- Each kidney of an adult human measures 10-12 cm in length, 5-7 cm in width, 2-3 cm in thickness with an average weight of 120- 170 g.
- These are located in the retroperitoneal space between the parietal peritoneum and the posterior abdominal wall, well protected by muscle, fat, and ribs.
- The kidneys are well vascularized, receiving about 25% of the cardiac output at rest
- The left kidney is located at about the T12 to L3 vertebrae, whereas the right is lower due to slight displacement by the liver.
- Upper portions of the kidneys are somewhat protected by the eleventh and twelfth ribs
- These are directly covered by a fibrous capsule composed of dense, irregular connective tissue that helps to hold their shape and protect them.
- This capsule is covered by a shock-absorbing layer of adipose tissue called the renal fat pad.
- The renal pad is encompassed by a tough renal fascia.
- The fascia and, to a lesser extent, the overlying peritoneum serves to firmly anchor the kidneys to the posterior abdominal wall in a retroperitoneal position.
- On the superior aspect of each kidney is the adrenal gland.
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Kidneys are covered by renal capsule. Hence, the correct option is a. renal capsule
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