Download Urinary System

Functions of the Urinary System
 Elimination of N wastes, toxins, drugs
 Regulate aspects of homeostasis
 Water, electrolytes, pH
 Blood pressure
 Red blood cell production
 Activation of vitamin D
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Organs of the Urinary system
 Kidneys
 Ureters
 Urinary bladder
 Urethra
Figure 15.1a
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Nephron
 Basic unit that forms
urine
 Filters fluid and
reabsorbs needed
substances
 Bowman’s capsule
 Tubule: proximal, loop
of Henle, distal,
collecting
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Tubular and Vascular Nephron
Components
Blood vessels
associated with
tubules:
Arterioles:
afferent,
efferent
Capillaries:
glomerular,
peritubular,
vasa recta
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 15.5
Formation of Urine
1. Filtration - passive, nonselective
2. Reabsorption - water, glucose, amino acids
3. Secretion - active; H+, NH4+, K+, drugs
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 15.6
Tubular Reabsorption
 Overall: returns water and
solutes to blood capillaries
 1. Na+ moved by active transport
from tubule cells to interstitial
fluid and diffuses to capillaries
 2. Cl- passively follows Na+
(balanced charge)
 3. Water reabsorbed with salts
 4. glucose and amino acids are
cotransported with Na+ into
tubule cells; then they diffuse
into the interstitial fluid
 ONLY energy input is to move
Na+ out of tubule cell (step 1)
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Tubular Secretion
 Tubular secretion: removes other substances
from blood
 Purposes: regulate chemical levels in
body, excrete harmful chemicals
 Substances secreted: penicillin, cocaine,
marijuana, pesticides, preservatives, H+,
NH4+, potassium
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Formation of Dilute Urine
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 15.10
Regulation of Water and Electrolyte
Reabsorption
 Regulation is primarily by hormones
 Antidiuretic hormone (ADH) prevents excessive
water loss in urine
 Aldosterone regulates Na+ content of
extracellular fluid
 Triggered by the renin-angiotensin mechanism
 Cells in the kidneys (juxtaglomerular apparatus) and
hypothalamus are active monitors
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Regulation of Blood Solutes, Volume
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Maintaining Water Balance
 Water intake must equal water output
 Sources for water intake
 Ingested foods and fluids
 Water produced from metabolic processes
 Sources for water output
 Vaporization out of the lungs
 Lost in perspiration
 Leaves the body in the feces
 Urine production
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Blood Buffers - Review
 Blood pH must remain between 7.35 and 7.45 to
maintain homeostasis
 Buffer molecules react to prevent changes in H+
concentration
 Bind to H+ when pH drops
 Release H+ when pH rises
 Three major chemical buffer systems
 bicarbonate, phosphate, protein
 Respiratory buffer system
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Renal Mechanisms of Acid-Base Balance
 Slower than chemical regulation, but effective
at maintaining blood pH
1. Reabsorption of bicarbonate ions
2. Excretion of H+ (as NH4+)
 Urine pH varies from 4.5 to 8.0
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Urinary Bladder
 Smooth, collapsible, muscular sac
 Temporarily stores urine
Figure 15.6
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Urethra
 Thin-walled tube that carries urine from the
bladder to the outside of the body by
peristalsis
 Release of urine is controlled by two
sphincters
 Internal urethral sphincter (involuntary)
 External urethral sphincter (voluntary)
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Characteristics of Urine Used for Medical
Diagnosis
 Colored yellow due to the pigment urochrome
and solutes
 Sterile
 Slightly aromatic
 Normal pH of around 6
 Specific gravity of 1.001 to 1.035
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Disorders of the Urinary System
 Kidney stones
 Acute and chronic renal failure
 Therapies:
 Dialysis
 Kidney transplant
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings