Download Chapter 15: The Urinary System

Chapter 15: The Urinary System
Maintains homeostasis of body fluids, osmotic regulation and pH control. Filters
blood, excretes wastes and excesses.
I. Anatomy
Kidneys produce urine, passes through ureters into bladder, then out from
urethra.
(A) Urine Production – occurs within nephrons: tiny tubular structures,
each is surrounded by circulatory elements, produces urine from blood. There
are more than a million nephrons per kidney.
Nephron = Bowman’s capsule proximal convoluted tubule  loop of
Henle  distal convoluted tubule  collecting duct (shared by several
nephrons.
Blood provided by an afferent arteriole  glomerulus (knot of ‘leaky’
capillaries)  efferent arteriole  peritubular capillaries.
Process involves:
-1- filtration: movement from glomerulus to Bowman’s capsule.
-2- reabsorption: from renal tubule into peritubular capillaries.
-3- secretion: form peritubular capillaries into renal tubule.
(B) Regulation – water reabsorption varies to obtain water balance.
Hormones:
-1- ADH: increases water reabsorption
-2- aldosterone: increases sodium reabsorption
-3- renin: stimulated by angiotensin and aldosterone, increases BP
-4- ANP from heart decreases BP, via decreased Na+ reabsorption.
Kidneys also produce erythropoietin to increase RBC production.
Caffeine decreases Na+ reabsorption, alcohol inhibits ADH.
II. Disorders
Kidney stones- may be linked to diet; UTIs (urinary tract infections)- usually E.
coli; renal failure (acute vs. chronic)- treated with dialysis.