Urinary System physiology Flashcards
What are the main functions of the kidneys?
Excretion of wastes, H2O balance, Plasma volume control, Blood pressure control, Renin production, Acid-base balance, Blood cell production (erythropoietin), Vitamin D activation
What components make up the urinary system?
Kidneys, Ureters, Urinary bladder, Urethra, Blood supply (20% of total flow)
What is the functional unit of the kidney?
Nephron
How many nephrons are typically found in one kidney?
Approximately 1 million
What are the parts of the kidney?
-Renal calyces
-Renal cortex (outer)
-Renal medulla (inner)
-Renal pelvis
What are the two types of nephrons?
- Cortical (85%): shorter
- Juxtamedullary (15%): longer looped and important in establishing the osmostic gradient
Vascular components of nephron
1) renal artery
2) afferent arteriole
3) glomerulus
4) efferent arteriole
5) peritubular capillaries
6) renal vein
What is the glomerulus?
-Tuft of capillaries that filters a protein-free plasma into the tubular component
-Very permeabled because they are genestrated capillaries
What do the peritubular capillaries do?
supply the renal tissue with exchanges from the blood
Tubular components of nephrons
1) bowman’s capsule (surrounding glomerulus)
2) proximal tubule
3) loop of henle - ascending and descending
4) distal tubule
5) collecting duct
What is glomerular filtration?
Nondiscriminant filtration of protein-free plasma from the glomerulus (blood) into Bowman’s capsule (tubule)
What is tubular reabsorption?
Movement from tubule back into blood
What is tubular secretion?
Molecules that are too big that we move from blood into the tubule
What processes result in urine formation?
Glomerular filtration, Tubular reabsorption, Tubular secretion
Sites of action for filtration, reabsorption, secretion
Filtration: bowman’s capsule
Reabsorption: loop of henle, proximal tubule, distal tubule, collecting ducts
Secretion: proximal tubule, distal tubule, collecting ducts
Is the proximal or distal tubule free for all or hormonally controlled?
Proximal: free for all
Distal: hormone controlled
What does glomerular filtration filter?
All but RBCs and proteins (too big)
-Peptides are ok though
What gets reabsorbed?
Na, Cl, Ca, PO4, water, glucose
What gets secreted?
potassium, hydrogren, large organics
What is the role of podocytes in the glomerulus?
They encircle the glomerulus tuft and can change shape of filtration slit to control filtration
Which layers does glomerular filtration have to pass?
-Glomerular capillary wall through pores
-Basement membrane: acellular gelatinous layer made of collagen and glycoproteins
-Inner layer of Bowman’s capsule
How much glomerular filtration occurs per day?
160 to 180 L/day
Urine is composed of _______% of filtrate
1%
What happens to podocytes in renal failure?
Large slits which allow proteins and RBCs in