Physiology Topics
The kidney has many functions:
The kidneys receive about 1/4 of the cardiac output. When one kidney is lost, the remaining kidney's cells will hypertrophy due to IGF-1 and can perform up to 80% of the original renal function. Kidney cells cannot regenerate.
The kidney has two distinct regions: the outer cortex and the inner medulla. They contain about a million nephrons, the functional unit of the kidney. Each nephron consists of two portions: a renal corpuscle and a renal tubule. Each corpuscle has two components: the glomerulus and the glomerular capsule.
Each nephron receives one afferent arteriole, which divides into a capillary network called the glomerulus. The glomerular capillaries reunite to form an efferent arteriole that drains blood out of the glomerulus. Coordinated vasodilation and vasoconstriction of the afferent and efferent arterioles can produce large changes in renal flow. The efferent arterioles divide to form a network of peritubular capillaries that surround portions of the nephron in the renal cortex.
Renal nerves are part of the sympathetic division of the autonomic nervous system. Most renal nerves innervate blood vessels and regulate blood flow through the kidney by altering the diameter of the arterioles.
From the capsule, filtrate passes into the tubule, which has 3 main sections: proximal convoluted tubule, loop of Henle and distal convoluted tubule. The corpuscle and renal tubule lie within the renal cortex, while the loop of Henle extend into the medulla. Distal tubules of several nephrons empty into a single collecting duct.
Cortical nephrons (80-85%) have their corpuscles in the outer cortex and have short loops of Henle that penetrate only into the superficial medulla. Juxtamedullary nephrons (15-20% have their corpuscles deep in the cortex and long loops of Henle that extend deep into the medulla. Nephrons with long loops of Henle allow for excretion of very diluted or very concentrated urine.
The final portion of the ascending loop of Henle makes contact with the afferent arteriole at a region known as the macula densa. Alongside the macula densa, the wall of the afferent arteriole contains juxtaglomerular cells (modified smooth muscle). Together macula densa and juxtaglomerular cells constitute the juxtaglomerular apparatus.
At the end of the distal convoluted tubule and continuing into the collecting duct are principal cells and intercalated cells. Principal cells have receptors for antidiuretic hormone (ADH) and aldosterone. Intercalated cells id blood pH homeostasis.
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1- List the 5 major functions of the kidney.
2-