Function of the Urinary System Flashcards
Function of the Urinary System
Removal of metabolic wastes (nitrogenous and acidic)
Removal of hormones, drugs, and other foreign material from the body
Regulation of water, electrolytes and acid-base balance
Secretion of erythropoietin
Activation of vitamin D
Regulation of blood pressure through renin-angiotensin-aldosterone system
Kidneys
Superior portion protected by lower ribs
Cortex (outer layer) contains glomeruli
Medulla (inner section) contains tubules and collecting ducts. Inside the medulla is the renal pelvis and calyces through which urine flows into ureter.
Filtration
A large volume of fluid including wastes, nutrients, electrolytes and other dissolve substances, passes from the blood into the tubule, cells and protein remain in the blood. When pressure is increased, more filtrate forms, more urine is produced.
Three parts of the tubule
Proximal convoluted tubule, loop of Henle, and the distal convoluted tubule
Function of tubule
Reabsorption of essential nutrients, water and electrolytes and secretion of certain wastes and electrolytes.
Main action of proximal tubule
Most water is reabsorbed into blood along with glucose and other nutrients and some electrolytes.
Glucosuria
Limit on reabsorption of glucose (transport or tubular maximum), hyperglycemia associated with diabetes mellitus.
What is the function of hormones in the renal system?
Control the reabsorption of fluid and electrolytes.
ADA
Antidiuretic hormone - from the posterior pituitary, controls reabsorption of water by altering the permeability of the distal convoluted tubule and collecting duct
Aldosterone
Adrenal cortex, control sodium reabsorption and water by exchanging sodium ions for potassium or hydrogen ions in the distal convoluted tubule.
Atrial natriuretic hormone
From the heart, also controls fluid balance by reducing sodium and fluid reabsorption in the kidneys
How much of the cardiac output enters the rental arteries from the aorta?
20-25%
Peritubular capillaries or vasa recta
Flow blood vessels to kidney: afferent arteriole, glomerular capillaries, efferent arteriole, then peritubular capillaries or vasa recta
How many sets of arterioles and capillaries are included in each nephron?
Two arterioles: afferent and efferent
Two capillaries: glomerular and peritubular
Summary of blood flow through kidney
Renal artery, interlobar artery, arcuate artery, interlobal artery, afferent arteriole, glomerular capillaries, efferent arteriole, peritubular capillaries, interlobular vein, arcuate vein, interlobar vein, renal vein.
What is the purpose of dual arterioles (afferent and efferent?)
To control the pressure in the glomerular capillaries and consequently the glomerular filtration pressure. This pressure determines the glomerular filtration rate (GFR)
What three factors control constriction in the arterioles
Local autoregulation - small, local reflex adjustments in the diameter of the arterioles made in response to minor changes in blood flow in the kidneys
Sympathetic nervous system - increases vasoconstriction in both arterioles when stimulated
Renin angiotensin mechanism - Renin is secreted by the juxtaglomerular cells in the kidney when blood flow in the afferent arteriole is reduced for any reason. Renin acts on the plasma protein angiotensinogen to produce angiotensin 1 and as the blood passes through the lung, angiotensin converting enzyme converts angiotensin 1 to angiotensin 2, a powerful systemic vasoconstrictor.
What happens if blood flow to the kidney is seriously impaired? E.g. blood pressure drop
Both the SNS and the renin-angiotensin mechanism are activated to restore blood pressure and flow to vital areas.
The renin-angiotensin-aldosterone
When blood flow decreases for any reason, angiotensin causes systemic vasoconstriction and stimulates production of aldosterone which increased reabsorption of sodium and water to increase blood volume