Unit 4 Ch. 19 Flashcards
What is the role of the kidney?
- regulate ECF volume/ BP
- regulate osmolarity
- ion balance
- pH
- waste excretions
What is the endocrine role of the kidney?
- produces renin
- produces erythropoietin
- converts Vit D3 to active form.
Trace the role of the following in the urinary system: urinary bladder urethra kidney renal artery renal vein renal pelvis
- kidney: urine formation
- renal artery: carried blood to kidney
- renal vein: carries blood from the kidney
- renal pelvis: collection cavity.
- ureter: 2 of them, urine to bladder
- urinary bladder: urine storing sac. relaxes with filling.
- urethra: excretion tube
T/F: once urine is made by the kidney, it is modified in the urinary bladder.
FALSE. once urine is made by the kidney, it is neither altered in composition or volume. EVEN IF YOU ARE DYING OF THIRST!
What is the functional unit of the kidney? Basic anatomy?
- The nephron. Composed of an outer cortex and inner medulla that empties into the renal pelvis and then ureter.
- Vascular and tubular components
What are the individual components of the vascular component of the nephron?
- afferent arteriole: brings blood to the glomerulus
- glomerulus: tuft of capillaries with lots of H2O filtration!
- efferent arterioles: carry 80% of blood not filtered into kidneys
- Peritubular Capillaries: Blood supply, tubular component.
What is the trace of blood flow in the kidneys?
afferent arteriole–> glomerular capillaries (vascular component)–> efferent arteriole–> peritubular capillaries (tubular component)–> cortical radiate vein
What are the components of the tubular component of the nephron?
- Bowmans capsule: cups glomerulus
- Proximal tubule: CORTEX! filtered fluid
- loop of henle: hairpin loop, dips into MEDULLA. descending/ascending segments
- juxtaglomerular apparatus: regulating site. @ 2 forks of afferent/efferent arterioles (which is which??)
- distal tubule: empties into collecting duct
- collecting duct: collects 8 nephron fluid. empties into renal pelvis.
What are the two types of nephrons? Distinguish by their location and length of their structures.
- cortical nephrons. 80% no vasa recta
2. juxtamedullary nephrons. 20% vasa recta. establish vertical osm. gradient/ urine conc.
What is the role of vasa recta?
-peritubular capillaries that closely associate with loop of henle.
What are the 3 basic renal processes?
- Glomerular Filtration (20% of plasma)
- Tubular Reabsorption (filtered to blood)
- Tubular Secretion (filtered back to lumen)
End Result: <1% of plasma leaves
In glomerular filtration, fluid must pass through 3 layers of glomerular membrane, what are they?
- Glomerular capillary wall: perforated, 100x H20 perm v. regular capillaries
- Basement membranes: prevent plasma proteins from entrance (glycoproteins/collagen)
- Inner layer of Bowman’s capsule: podocytes, foot processes (filtration slits).
What three forces are involved in glomerular filtration rate (GFR?) Do they oppose or promote filtration?
- Glomerular capillary blood pressure: driving force filtration.
- Plasma-colloid osmotic pressure: opposes filtration. Water wants to decrease concentration of blood plasma proteins
- Bowman’s Capsule Hydrostatic Pressure: opposes filtration. Fluid pressure.
- *Positive net filtration means inward GFR
How are changes in GFR regulated?
- intrinsically: auto regulation
- extrinsically: sympathetic regulation
What is autoregulation?
- Maintenance of a constant GFR at MAP between 80 and 180 mmHg.
- Result: daily activities don’t disrupt kidney function.
- Myogenic/ Tubuloglomerular feedback
Myogenic autoregulation responds to changes in pressure within the nephron’s vascular compartment. What is the result when blood pressure increases/ decreases?
- BP increases: resistance in afferent arterioles which leads to decreased GFR.
- BP decreases: resistance in efferent arterioles which leads to increased GFR.
Tubuloglomerular feedback is associated with changing NaCl concentrations in filtrate. What does inc/ dec. NaCl result in? What detects changing salt conc.?
- Inc. NaCl. (retain water) decrease GFR
- dec NaCl. increase GFR
- Macula densa cells in distal tubule detect NaCl changes.
- What is Tubular Reabsorption?
- Distal or proximal tubule?
- What 2 processes?
- Tubular reabsorption is highly selective resulting in reabsorption into ECF and capillaries of necessary materials
- Mostly in proximal tubule (closest one to glomerulus)
- transepithelial and paracellular movement.
Explain Na+ reabsorption
- Uniquely, varies along tubule length
- 67% in proximal tubule (the girl that everyone follows ie. glucose, amino acids, water, Cl-, and urea)
- 25% reabsorbed in loop of hence
- 8% reabsorbed in distal/ collecting tubule. Role in ECF volume (RAAS!!)
What are the [Na+] in tubule lumen, proximal tubule cells, and ISF? How is Na+ transported?
- Requires Na+-K+ ATPase (ATP pump!) to move from tubes to ISF
- Tubule lumen: High [Na+] salty pee
- Tubule Cell: Low [Na+] movement here is passive (diffusion)
- ISF: high [Na+] so moves against gradient to here
How is glucose reabsorbed? What are the relative concentrations of glucose in lumen, tubule cells, and ISF?
- Glucose concentrations opposite sodium!
- Co-transport with sodium (the best friend)
- First against gradient (co-trans) then by diffusion. Just think glucose (fuel) doesn’t want to be peed out!!! It will escape lumen at all costs
How is Cl- reabsorbed?
- Results from active Na+ reabsorption
- passive
- down it’s E gradient and between (not through) cells
How is H2O reabsorbed?
- travels via aquaporins
- also travels through “leaky” junctions
- directed by osmotic gradient to capillaries
- proximal tubules: always open
- distal tubules: vasopressin!
How is urea reabsorbed?
- passive reabsorption
- down concentration gradient
- only waste product small enough to diffuse
- conc. increases as you travel down proximal tubule. (due to Na and H2O leavings together like BFFS)
What is tubular secretion?
- secretion INTO tubules
- active process (transepithelial transport)
When are H+ and K+ secreted?
- H+ : proximal, distal, collecting tubules. Inc. Acidity= Inc. Secretion (get rid of acid!!!)
- K+: proximal tubules, reabsorbed. Distal tubules, secreted (conc. maintenance).
Trace the mechanism of K+ secretion from peritubular capillary-> IF-> Tubular Cell-> Lumen
- Peritubular capillary-> IF (diffusion)
- IF -> Tubular Cell (Active transport)
- Tubular cell-> Lumen (Passive transport via channel)
How is K+ secretion controlled?
- Controlled by aldosterone
- Inc. plasma [K+], increased aldosterone.
- Increased aldosterone, Inc. K+ secretion
- Increased secretion, you pee out more potassium!
What is the purpose of the organic ion secretory system?
- Promote secretion of substances (organic ions) and remove them from blood
- Encourages release from carrier and elimination (they’ve served their purpose)
- Localized in the proximal tubule (get rid of faster!)
What is plasma clearance?
- The VOLUME (not amount) of plasma cleared of a particular substance per minute.
- can measure GFR.
- ex: glucose clearance=0 because it’s all reabsorbed.
- clearance>GFR: secretion
How does plasma clearance rate compare to GFR during reabsorption/secretion/equal parts?
- secreted but not reabsorbed (adding more substance to urine to get ride of): clearance>GFR
- reabsorbed but not secreted (removing substance to use, glucose) : clearance<GFR
- not reabsorbed or secreted: clearance=GFR
What are the roles of the bladder and urethra?
- Bladder: stores urine until micturition. Folded until full. Parasympathetic fibers.
- Urethra: tube. 2 sphincters. Internal, smooth (not a true sphincter). External, skeletal.
