Lecture 23 Flashcards
Urine flows
Urine flows –> kidney –> down its ureter –> bladder –> the outside via the urethra
Urinary system =
kidneys, ureters, urinary bladder, and urethra
Filter:
the blood and return most of water and solutes to the bloodstream
Overview of Kidney Functions:
- Regulation of blood ionic composition, blood pH, osmolarity, and glucose, blood volume, blood pressure
- Release of erythropoietin and calcitriol
- Excretion of wastes & foreign substances
Regulation of blood ionic composition:
Na+, K+, Ca+2, Cl- and phosphate ions
Regulation of blood volume:
conserving or eliminating water
Regulation of blood pressure
- secreting the enzyme renin
- adjusting renal resistance
Drainage system fills
renal sinus cavity
Drainage system minor and major calyces…
empty into the renal pelvis which empties into the ureter
Blood & Nerve Supply of Kidney: Abundantly supplied with
- blood vessels
- receive 25% of resting cardiac output via renal arteries
Functions of different capillary beds:
- glomerular capillaries
- peritubular capillaries
- vasa recta
glomerular capillaries:
- where filtration of blood occurs
- vasoconstriction & vasodilation of afferent & efferent arterioles produce large changes in renal filtration
peritubular capillaries:
carry away reabsorbed substances from filtrate
vasa recta:
supplies nutrients to medulla without disrupting its osmolarity form
Blood & Nerve Supply of Kidney: regulate blood flow & renal resistance by altering arterioles
Sympathetic vasomotor nerves
Blood Vessels around the Nephron:
Glomerular capillaries
Efferent arterioles
Glomerular capillaries are formed between
the afferent & efferent arterioles
Efferent arterioles give rise to
the peritubular capillaries and vasa recta
The Nephron:
- Renal corpuscle
- Renal tubule
- Collecting ducts and papillary ducts
Renal corpuscle =
site of plasma filtration
Renal corpuscle: 2 components
- glomerulus is capillaries where filtration occurs
2. glomerular (Bowman’s) capsule is double-walled epithelial cup that collects filtrate
Renal tubule=
- proximal convoluted tubule
- loop of Henle dips down into medulla
- distal convoluted tubule
Collecting ducts and papillary ducts:
drain urine to the renal pelvis and ureter
Cortical Nephron:
- 80-85% of nephrons are cortical nephrons
- Renal corpuscles are in outer cortex and loops of Henle lie mainly in cortex
Flow of Fluid through a Cortical Nephron:
Glomenular capsule –> Proximal convoluted tubule –> Descending limb of the loop of Henle –> Ascending limb of the loop of Henle –> Distal convoluted tubule
Juxtamedullary Nephron:
- 15-20% of nephrons are juxtamedullary nephrons
- Renal corpuscles close to medulla and long loops of Henle extend into deepest medulla: excretion of dilute or concentrated urine
Flow of Fluid through a Juxtamedullary Nephron:
Glomenular capsule –> Proximal convoluted tubule –> Descending limb of the loop of Henle –> Thin Ascending limb of the loop of Henle –> Thick ascending limb of the loop of Henle –> Distal convoluted tubule
Histology of the Nephron & Collecting Duct:
- Single layer of epithelial cells forms walls of entire tube
- Distinctive features due to function of each region
Distinctive features due to function of each region:
microvilli
cuboidal versus simple
hormone receptors
Structure of Renal Corpuscle:
Bowman’s capsule
Glomerular capillaries
Structure of Renal Corpuscle:Bowman’s capsule
- surrounds capsular space
1. podocytes
2. simple squamous
podocytes cover
capillaries to form visceral layer
simple squamous cells form
parietal layer of capsule
Glomerular capillaries arise from what and form what?
afferent arteriole & form a ball before emptying into efferent arteriole
capsule space is where
filtrate accumulates
Number of Nephrons:
- Remains constant from birth
2. If injured, no replacement occurs
any increase in size of kidney is
size increase of individual nephrons
Dysfunction is not evident until function:
declines by 25% of normal
Removal of one kidney causes
enlargement of the remaining until it can filter at 80% of normal rate of 2 kidneys
