Unit 5: Kidneys Flashcards
What are the 6 main functions of the kidneys?
1) regulation of ECF volume and blood pressure
2) regulation of osmolarity
3) maintenance of ion balance
4) Homeostatic regulation of pH
5) excretion of wastes
6) production of hormones
Where are the kidneys located?
- in the back of the abdominal cavity, between the peritoneum and the bones/muscles of the back
What is the outer portion of the kidney called? The inside portion?
outer portion = renal cortex
inner portion = renal medulla
What is the hollow tube leading from the kidney to the bladder?
ureter
What is the nephron
- functional unit of the kidney
- smaller unit that can perform all of the functions of the kidney
- between 800,000 and 1.5 million nephrons per kidney
What are the two types of nephrons are how are they classified?
- classified by their location and their length
- juxtamedullary nephrons and cortical nephrons (80% of nephrons)
What are the two components of the nephron? And what do each of them do?
Vascular Component:
- afferent arteriole: carries blood into the glomerulus
- glomerulus: a tuft of capillaries that filters aa protein-free plasma into the tubular component
- efferent arteriole: carries blood from the glomerulus
- peritubular capillaries: supply the renal tissue; involved in the exchanges with the fluid in the tubular lumen
Tubular Component:
- Bowman’s Capsule: collects the glomerular filtrate
- Proximal tubule: uncontrolled reabsorption and secretion of selected substances
- loop of Henle: establishes an osmotic gradient in the renal medulla that is important in the kidney’s ability to produce urine of varying concentration
- distal tubule and collecting duct: variable, controlled reabsorption of Na+ and H20 and secretion of K+ and H+ occur here; fluid leaving the collecting duct is urine, which enters the renal pelvis
What are the steps in renal blood flow?
renal artery–> afferent arterioles–> glomerular capillaries–> efferent arterioles–>proximal peritubular capillaries–> vasa recta–> distal peritubular capillaries–> collecting duct (capillaries and veins) –> renal venules
What are the 3 basic renal processes?
1) glomerular filtration: movement of the fluid from the blood into the lumen of the nephron
2) tubular reabsorption: substances from filtrate moved back into the blood (peritubular capillaries)
3) tubular secretion: removes molecules from blood and adds them in filtrate in the lumen
What are the three filtration barriers in the first step in urine formation?
1) glomerular wall capillary wall
2) basal lamina (basement membrane)
3) epithelium of Bowman’s Capsule
What are the 3 forces involved in glomerular filtration?
1) glomerular capillary blood (hydrostatic) pressure (55mmHg out of glomerulus)
2) plasma-colloid osmotic pressure (30mmHg back into glomerulus)
3) Bowman’s capsule hydrostatic pressure (15 mmHg back into glomerular
- -> net 10mmHg outward pressure
What is glomerular filtration rate (GFR)?
- the volume of fluid that filters into Bowman’s capsule per unit time
- influenced by: surface area of glomerular capillaries available for filtration and permeability of interface between the capillary and Bowman’s capsule
What kind of adjustments occur when GFR is too high? Too low?
- if it is too high: excess water and solutes is lost due to high urine output
if it is too low: waste builds up
List and describe the two control mechanisms of control adjustments made to the GFR?
- auto regulation: prevents spontaneous changes to GFR
- extrinsic sympathetic control: overrides auto regulatory responses, aimed at long-term regulation of arterial blood pressure
Where does most of tubular reabsorption occur?
Mostly in the proximal tubule but some occurs in the distal segments.
Where does tubular reabsorption occur?
- from the tubular lumen into the peritubular capillaries
What are the 5 barriers in tubular reabsorption?
1) luminal membrane of tubular cell
2) pass through cytosol of tubular cell
3) basolateral membrane of the tubular cell
4) diffuse through interstitial fluid
5) pass through capillary wall to enter blood plasma
Where is the Na+-K+-ATPase pump located?
in the basolateral membrane of tubular cells
Where does tubular secretion occur?
-substances transfer from peritubular capillaries into the tubular lumen
What are the most important secretory system for and where are they secreted?
1) H+ (regulating acid-base balance)
- proximal, distal and collecting ducts
2) K+ (maintained membrane excitability in muscles and nerves)
- distal and collecting tubules controlled by aldosterone
3) Organic ions (waste removal)
- proximal tubule
What does excretion rate of a substance rely on?
1) filtration rate of the substance
2) whether the substance is reabsorbed and/or secreted
If less solute appears in the urine than the blood then _________________
reabsorption must have occurred
If more solute appears in the urine than the blood then __________________
secretion must have occurred.
What is the internal sphincter made of? The external sphincter?
internal sphincter: is the continuation of the bladder wall
external sphincter: ring of skeletal muscle controlled by somatic motor neurons
