Guyton Renal Tubular Filtration
Chapter 26
Multiple Fxns of Kidneys in Homeostasis 1. Excretion of metabolic waste products and foreign chemicals 2. Regulation of Water and electrolyte balance 3. Regulation of Arterial pressure
--long term: excreting variable amounts of sodium and water
--short term: secreting vasoactive factors or substances such as rennin
4. Regulation of Acid-Base balance --the only means of eliminating sulfuric acid and phosphoric acid
5. Regulation of Erythrocyte Production --secretion of erythropoietin
6. Regulation of 1, 25-dihydroxyvitamin D3 (calcitriol) production
7. Gluconeogenesis --synthesis of glucose from amino acids during prolonged fasting
Renal Blood Supply
=blood flow to the two kidneys is normally about 22% of the cardiac output or 1100 ml/min
=renal circulation has two capillary beds: glomerular and peritubular capillaries --- arranged in series and separated by the efferent arterioles (help regulate the hyrostatic pressure in both capillaries)
=glomerular capillaries have high hydrostatic pressure (60 mmHg) which causes rapid fluid filtration
=peritubular capillaries have lower hydrostatic pressure (13 mmHg) which permits rapid fluid reabsorption
=kidneys can regulate the hydrostatic pressure in both capillaries by: a) adjusting the resistance of the afferent and efferent arterioles b) changing the rate of glomerular filtration, tubular reabsorption, or both in response to body homeostatic demands
The Nephron is the Functional Unit of the Kidney
=each kidney contains 800,000 to 1 million nephrons
=the kidney cannot regenerate new nephrons
=after age 40, the number of functioning nephrons decreases about 10% every 10 years
Micturition
=process by which the urinary bladder empties when it becomes filled
=involves two main steps: 1) bladder fills progressively until the tension in its walls rises above a threshold level; this elicits 2) 2) a nervous reflex called
Multiple Fxns of Kidneys in Homeostasis 1. Excretion of metabolic waste products and foreign chemicals 2. Regulation of Water and electrolyte balance 3. Regulation of Arterial pressure
--long term: excreting variable amounts of sodium and water
--short term: secreting vasoactive factors or substances such as rennin
4. Regulation of Acid-Base balance --the only means of eliminating sulfuric acid and phosphoric acid
5. Regulation of Erythrocyte Production --secretion of erythropoietin
6. Regulation of 1, 25-dihydroxyvitamin D3 (calcitriol) production
7. Gluconeogenesis --synthesis of glucose from amino acids during prolonged fasting
Renal Blood Supply
=blood flow to the two kidneys is normally about 22% of the cardiac output or 1100 ml/min
=renal circulation has two capillary beds: glomerular and peritubular capillaries --- arranged in series and separated by the efferent arterioles (help regulate the hyrostatic pressure in both capillaries)
=glomerular capillaries have high hydrostatic pressure (60 mmHg) which causes rapid fluid filtration
=peritubular capillaries have lower hydrostatic pressure (13 mmHg) which permits rapid fluid reabsorption
=kidneys can regulate the hydrostatic pressure in both capillaries by: a) adjusting the resistance of the afferent and efferent arterioles b) changing the rate of glomerular filtration, tubular reabsorption, or both in response to body homeostatic demands
The Nephron is the Functional Unit of the Kidney
=each kidney contains 800,000 to 1 million nephrons
=the kidney cannot regenerate new nephrons
=after age 40, the number of functioning nephrons decreases about 10% every 10 years
Micturition
=process by which the urinary bladder empties when it becomes filled
=involves two main steps: 1) bladder fills progressively until the tension in its walls rises above a threshold level; this elicits 2) 2) a nervous reflex called