URINARY SYSTEM
Overall Function Blood homeostasis Excretes waste Regulates blood pressure Erythropoeisis Activates Vitamin D
Kidneys Renal, Nephr- T12-L3 region Retroperitoneal Protective layers – Renal capsule – Adipose capsule – Renal fascia
Kidney Hilus Cortex Medulla – Renal pyramids (8-18) – Renal papilla Pelvis – Minor calyx – Major calyx
Kidney Microstructure Nephron Functional unit of the kidney Glomerulus Network of blood capillaries Afferent & Efferent arterioles Slits & Pores
Nephron - Tubules Glomerular capsule (Bowman’s capsule) – Renal corpuscle Proximal convoluted tubule Descending limb of loop of nephron (Henle) Loop of nephron Ascending limb of loop of nephron Distal convoluted tubule Collecting tubule
Blood supply 1200 ml/min Filters blood volume 60 x/day 1/5 CO
Nephron Physiology Controls blood concentration & volume Helps regulate blood pH Removes toxic waste from blood Urine production (2-4 pts/day)
Glomerular filtration 45 gallons of filtrate/day! Passive process Glomerulus to capsule
Glomerular filtration Net filtration pressure favors filtration Glomerular blood pressure (60 mm Hg, other caps are mm Hg) Capsular pressure – Opposes filtration Colloid osmotic pressure – Opposes filtration
Arterial blood pressure Stable glomerular filtration rate Urine output increases/decreases as blood pressure increases/decreases
Sympathetic stimulation
Tubular Reabsorption & Secretion Proximal convoluted tubule Permeable to solutes & they are actively reabsorbed Permeable to water & it is passively reabsorbed Some tubular secretion (H+ and K+)
Descending limb Relatively impermeable to solutes Permeable to water, it is reabsorbed Interstitial gradient promotes reabsorption
Loop Urea is recycled
Ascending limb Permeable to NaCl, it is reabsorbed Impermeable to water
Distal Convoluted Tubule Aldosterone Anti-diuretic hormone Secretion occurs (H+, NH3, drugs) Juxtaglomerular apparatus (where precursors of erythropoeitin & renin are made)
Collecting tubule (ducts) Aldosterone causes sodium reabsorption ADH causes water reabsorption Urea to interstitial space
Vasa recta Thin walled blood vessels serving tubules Counter-current Maintains interstitial concentrations Aids in concentrating urine Some water reabsorption
Other renal functions Vitamin D activations Erythropoietin precursor Blood pressure - renin
Minimum urine volume.5 liters/day Maximum urine concentration is 1200 milliosmoles/liter Make about 600 mosmol of waste/day 600 mosmol waste/day / 1200 mosmol/liter =.5 liters/day
Ureter Kidney to bladder Peristalsis
Urinary Bladder Holds up to about 800 mls of urine in pelvic cavity Internal & External sphincters Micturition = Urination Micturition reflex Voluntary urination
Urethra Urinary bladder to external urethral orifice Long in males, short in females