Urinary System Flashcards
What are metabolic waste problems?
potentially harmful substances to the body
-must be eliminated
ex: CO2, H2O, bile salts, nitrogenous waste
What is the urinary system?
single most important route for removal of waste products
*removes nearly all soluble waste from blood
-transports soluble waste out of body
-eliminates excess water
Parts of urinary system
-kidneys (2)
-ureters (2)
-urinary bladder
-urethra
Functions of Kidney
production of urine to facilitate elimination of metabolic waste materials
Kidneys help maintain homeostasis through:
-blood filtration: reabsorption, secretion
-fluid balance regulation
-acid base balance regulation
-production of hormones
-blood pressure regulation
Kidney location
-located in dorsal abdominal area
-near lumbar vertebrae
retroperitoneal to the abdominal cavity
-surrounded by layer of perirenal fat
-right kidney more cranial than left (except pigs)
Gross anatomy of Kidney
-bean shaped in most
*covered by fibrous c.t. capsule
-hilus: indented area on medial side
Nephron
basic functional unit
-numbers varies with size of animal
Nephron is composed of:
- renal corpuscle
- proximal convoluted tubule
- loop of Henle
- distal convoluted tubule
Renal corpuscle
-located in renal cortex
-made up of glomerulus
-surrounded by Bowman’s capsule
-filters blood in first stage of urine production: glomerular filtrate
Proximal Convoluted Tubule
-continuation of capsular space of Bowman’s capsule
-longest part of nephron
*reabsorption and secretion functions
-glomerular filtrate now called tubular filtrate
Loop of Henle
-continues from PCT, descends in medulla, makes U turn then heads back into cortex
-descending wall is thinner, ascending wall becomes thicker again
-resorb water, Na+, Cl-
Distal convoluted tubule
-continuation of ascending loop of Henle
-all nephrons empty into collecting ducts
(renal pelvis)
Collecting ducts
primary site of ADH action and regulation of potassium and acid-base balance
Nerve supply to Kidneys
-sympathetic portion of autonomic ns
-not essential for function
-sympathetic stimulation causes vasoconstriction or renal vessels= *temporarily decreases urine function
Blood supply to the kidney
comes from renal artery, enters at hilus
-subdivides to become a series of afferent glomerular arterioles
- Afferent glomerular arterioles
carry blood to renal corpuscle
- Glomerular capillaries
filter some plasma out of the blood: glomerular filtrate
-then vessels turn into efferent glomerular arterioles
- Peritubular capillaries
O2 transfer to cells of nephron
- Tubular
reabsorption and tubular secretion occur at this level
Mechanisms of Renal Action
- filtration of blood
- reabsorption of useful substances - back into bloodstream
- secretion of waste products - from the blood
Filtration of the blood
-occurs in renal corpuscle
High blood pressure in glomerular capillaries forces
some plasma into capsular space of Bowman’s capsule
-fenestrations in capillary endothelium
-glomerular filtrate formed (similar to plasma but no protein)
Glomerular Filtration Rate
-how fast plasma is filtered as it passes through the glomerulus
-depends on rate of blood flow to kidney
Reabsorption
useful substances leave tubules of nephron and enter into blood of peritubular capillaries
ex: Na, K+, glucose, amino acids, etc
Sodium reabsorption
-sodium actively pumped out of cell into interstitial fluid, where it moves into peritubular capillaries
-in tubular filtrate attaches to carrier protein
*also reabsorbed in ascending loop of Henle and DCT
Secretion
primarily in DCT
ex: H+, K+, ammonia
Urine Volume Regulation
urine volume is determined by amount of water contained in tubular filtrate when it reaches the renal pelvis
What is urine volume controlled by
actions of 2 hormones:
1. antidiuretic hormone (ADH) - prevents loss of water
2. aldosterone
Angiotensin II
causes arterial constriction to increase blood pressure and stimulates release of aldosterone
Ureters
-continuation of the renal pelvis
-move urine from kidneys to bladder
-each ureter leaves its kidney at the hilus
-composed of 3 layers
How do ureters enter the bladder
at an oblique angle
-openings collapse when bladder is full
-prevent backup of urine into ureters
Urinary bladder
-stores urine as it is produced
-release urine periodically from body
- 2 parts: muscular sac and neck
What muscle contracts to expel urine?
detrusor muscle
Urination Step 1
urine accumulation:
-bladder accumulates urine
-stretch receptors in bladder wall are activated
-pressure of filling bladder reaches certain trigger point
Urination Step 2
muscle contraction:
-spinal reflex is activated
-motor impulse sent to detrusor muscle
-smooth muscle in bladder wall contracts
-bladder emptied if animal is not house broken
Urination Step 3
sphincter muscle control:
-voluntary control of sphincter around heck of bladder offer temporary control of urination
-eventually it relaxes, urine is released
Urethra
-continuation of neck of bladder
-carries urine from bladder to external environment
-runs through pelvic canal
