Download The Urinary System

The Urinary System
Organs: Kidneys (creates urine),
ureters (transport), urinary bladder
(stores), urethra (transport)
Kidney Function
• Filter fluids from bloodstream and maintain
homeostasis in body
• Rids body of wastes, excess ions, toxins,
and drugs in urine
• Regulate blood volume, pH, salt content
• Secretes renin – regulates blood pressure
• Secretes erythropoietin – increases rbc
production
Kidney Anatomy
•
•
5” long, 2.5” wide
Renal capsule:
– encloses kidney
•
Renal cortex:
–
•
outer region
Renal medulla:
– deep to cortex w/ medullary
pyramids separated by renal
columns
•
Renal hilus:
– medial indentation
•
Rich Blood Supply
– Renal artery  segmental arteries
 lobar arteries  interlobar artery
 afferent arteriole  glomerulus
capillaries  efferent arteriole 
peritubular capillaries  interlobular
vein  arcuate vein  interlobar
vein  renal vein
Nephrons
• Nephrons form urine
• Glomerulus: knot of
capillaries
• Renal tubule w/ enlarged
bowman’s capsule at end
• Proximal convoluted
tubule
• Loop of Henle
• Distal convoluted tubule
• Collecting ducts: receive
urine from many
nephrons; deliver urine to
renal pelvis
Urine Formation
• Filtration
– Water and solutes smaller than proteins are forced thru capillary
walls and pores of glomerular capsule into the renal tubule
• Tubular reabsorption
– Water, glucose, amino acids, and needed ions are transported
out of the filtrate into the tubule cells and then enter the capillary
blood
• Tubular Secretion
– Urea, H+, K+, creatinine, and drugs are removed from the
peritubular blood and secreted by the tubule cells into the filtrate
• Urine: 1-2 L produced every 24 hrs
Ureters
• 10-12” long tubes
• Carry urine from
kidneys to bladder
• Peristalsis propels
urine transport
• Valve-like folds
prevent back flow
from bladder
Urinary Bladder
• Smooth, collapsible
muscular sac
• Temporarily stores
urine
• Empty: 2-3” long
• Full: 5”long and
stores 1-2 pints urine
Urethra
•
•
•
•
Thin walled tube
Carries urine (by peristalsis) from bladder
to outside the body
Females: 3-4” long, opening is anterior to
vaginal opening
Males: 8” long, opening at tip of penis
–
•
internal urethral sphincter:
–
•
Involuntary smooth muscle, keeps closed
when urine is not being passed
External urethral sphincter:
–
•
Double function: passageway for sperm
ejaculation
Voluntary skeletal muscle through pelvic
floor
Micturition – emptying the bladder
–
200mL urine collects and activates stretch
receptors and cause bladder to contract to
force open internal urtheral
sphincter…feel urge to void
Fluid and Electrolyte Balance
• 2/3 water in intracellular fluid (ICF)
• 1/3 water in extracellular fluid (ECF)
• Electrolytes: charged ions that conduct electrical
current, alters blood volume and blood pressure
– Ex. sodium, potassium, calcium ions
• Electrolyte balance maintained by hormones
– Antidiuretic hormone (ADH)
– Aldosterone
Acid-Base Balance
• Proper function, blood pH between 7.35-7.45
– Alkalosis rise in blood pH above 7.45
– Acidosis drop in pH below 7.35
• Blood Buffers
• Respiratory System
• Renal Mechanisms
– Excreting bicarbonate ions
– Reabsorbing or generating new bicarbonate ions