Renal: Of, relating to, or in the region of the kidneys
What are the four components of the Urinary system?
3. Urinary bladder
What is filtrate?
Fluid filtered from blood that enters nephron
What are the two regions of the Kidney?
1. Outer renal cortex
2. Inner medulla with pyramids
What is the pathway for drainage of filtrate?
Within the Inner medulla there are pyramids which drain into a minor calyx to a major calyx then the renal pelvis.
Where is urine made? What is the pathway of Urine?
2. a. Pools in renal pelvis
b. Down ureter
c. Into urinary bladder
d. Exits body through urethra
What are the sphicnters surrounding the urethra? What muscle is each one made of?
1. Internal urethral sphincter
2. External urethral sphincter
How many nephrons are in each kidney? Where does filtration occur?
1. Each kidney has a million microscpic nephrons
2. Filtration occurs in the renal corpuscle of the cortex
Is The Loop of Hendle part of the renal cortex or medulla? What is urine formed from? What is the pathway of filtrate into urine?
1. The loop of helde dips down from the cortex into the medulla
2. Urine is formed from filtrate
3. Bowman's capsule to proximal convoluted tubule to loop of hendle to distal convoluted tubule to collecting duct
What are the functions of the kidney? How does it do this?
1. Regulates the extracellular fluid in the body
2. Removal of waste products from blood and excretion from body as urine
What are the functions of the nephron?
Where does filtration occur? What is the structure of it's capillaries?
1. Filtration occurs in the glomerular corpuscle where fluid if filtered out of the blood and into nephron
2. The capillaries of the glomerular corpuscle are fenestrated
-the large pores allows water and solutes to leave but not blood cells and plasma proteins
What does the glomerular filtration rate measure? At what rate does it filter?
1. Glormeruler filtration rate: volume of fluid produced by both kidneys that filters into the renal corpuscle per unit time
2. Average is 180 L/day or 125 mL/min
What are the three factors that influence net filtration in the Glomerular? How do they effect Filtrate?
1. Bp in glomerulus
-Cuases pressure to filter out of capillaries into nephron
2. Blood proteins in capillaries
-causes fluid to be pulled in the capilaries by osmosis
3. Fluid in Bowman's capsule
-opposes filtration in cappilaries and pushes back in
What are the two types of absorption? WHat membranes do they cross?
1. Active or passive
2. Apical and basolateral membrane
What are the principles of the reabsorption of solutes?
1. Na+ is reabsorbed by active transport
2. Electrochemical gradient drives anion reabsoprtion
3. Water moves by osmosis following solute reabsorption
-concentrations of other solutes increase as fluid volume in lumen increase
4. Permeable solutes are reabsorbed by diffusion through membrane transporters or by paracelluler pathway (junctions between epithelial cells)
How much filtered water is excreted as urine?
Of the 180L of water filtered, only 1-2L is excreted as urine
What percentage of plasma is filtered as it passes the glomerulus? What percentage is excreted? Describe this process.
1. Only 20% of the plasma is filtered
2. Less than 1% is filtered
3. a. 100% of the plasma volume enters the afferent arteriole
b. 80% of the plasma passes through to efferent arteriole while the other 20% filters out in the glomerulus
c. Less then 19% of filtrate is reabsorbed
d. The original 80% that passed unfiltered as well as the >19% that was reabsorbed equals >99% of plasma entering the kidney that returns to the systemic circulation
e. the remaining <1% is excreted to the external environment
What does the proximal convoluted tubule reabsorb? What are the physical means of reabsorbing
1. The PCT reabsorbs most Na+ and water. The PCT completely reabsorbs glucose and amino acids by:
2. a. 2nd active transport with Na+ into cell
b. 1st active transport of Na+ out of cell basolateral membrane
c. facilitated diffusion
d. simple diffusion
How is salt pumped into interstitial fluid via the ascending loop of henle?
Na+ is reabsorbed down its gradient from filtrate into tubule cells with 2nd active transport of CL- and K+
- Na+ is moved into interstitial space by Na+ and K+ pumps
- Because the cellls of the loops of hendle are not permeable to water, the active reabsoprtion of ions in this region creates a dilute filtrate.
Where does the countercurrent exchange system occur? Which limb is permeabel to either water or salt?
1. Countercurrent exchange system occurs in the medulla as it uses juxtamedullary nephrons and vasa recta capillaries.
2. a. Descending limb is permeable to water only
b. Ascending limb is permeable to salt
What is the countercurrent exchange between in the vasa recta?
- Filtrate entering the descending limbb becomes progressively more concentrated as it looses water
- Blood in the vasa recta removes water leaving the loop og henle
- The ascending limb pumps out Na+, K+ and Cl_ and filtrate becomes hyposmotic
What is secretion?
- The active process using membrane proteins to transfer molecules from blood/ECF filtrae in lumen of nephron
What is excretion? What is it composed of?
1. Excretion is the elimination of material from the body
2. filtration - reabsorption + secretion = excretion
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What is the anti-diuretic hormone? Where is it produced? What is another name for it?
1. ADH causes the body to retain water
2. Produced by neurons of the hypothalamus and secreted by posterior pituitary gland
3. Also called vasopressin
What is the role of aquaporins?
Aquaporins in the collecting duct cause water to be reabsorbed.
What happens when ADH binds to receptors on the collecting duct?
1. Causes vesicles with aquaporin channels to fuse to the plasma membrane
2. Water channels are removed without ADH
What is Aldosterone? What are its functions?
1. It is a steroid hormone secreted by adrenal gland
2. a. regulates Na+ absorption in distal convoluted tubule and collecting duct
b. increases action of Na+,K+, ATPase in epithelial cells
What is ANP? When is it released?
1. Atrial natriuretic peptide: peptide hormone produced by specialized myocardial cells in the wall of atria.
2. Increases Na+ and water excretion
How does the kidney autoregulate glomeruler filtration rate? And renal blood flow?
1. GFR is maintained despite BP fluctuations due to tubuloglomerular feedback:
-macula densa cells sense rise in water and Na+ which signals increased BP
2. Renal blood flow is regulated through mypogenic constriction:
-smooth muscles in arterioles sense BP
What is the relation between fluid and ion levels? What organ regulates fluid?
1. Fluid balance implies a balance of ions
2. Kidneys regulate fluid balance by either loosing or gaining fluid at different rates as needed.
Since the healthy range of plasma protein is narrow, what happens when it is below or above that range?
1. Hypokalemia = below.
-muscle weakness and failure of respiratory muscles and the heart
2. Hyperkalemia = above
What role does: Na+, water, K+, Ca2+, H+, HCO3-, and mass balance play?
1. Na+: ECF volume and osmolarity
2. K+: cardiac and muscle function
3. Ca2+: exocytosis, muscle contractions
4. H+ and HCO3-: pH balance
5. Body mass: excretion routes: kidney, feces, sweat, and lungs
What is the amount of water gained in the body? WHat is the amount of water lost?
1. a. 2.2L/day of water is gained from food and drink
b. 0.3L/day is produced from metabolism
c. This totals about 2.5L/day
2. a. 0.9L/day as insensible water loss through skin and lungs
b. 1.5L/day is lost through urine
c. 0.1L/day is lost through feces
d. This totals 2.5L/day
What is the response to decreased blood pressure and volume?
1. Stimulus: decreased blood volume and pressure
2. Sensor: volume receptors in atria and carotid aortic barorecetors
3. Signal: trigger homeostatic reflexes
4. Targets: Cardiovascular system, behavior, kidneys
5. Tissue response:
a. cardiovascular system: increases cardiac output, vasoconstriction
b. behavior: thirst cuases increased water intake which increases ECF and ICF volume
6. Systemic response:
a. cardiovascular system and behavior: increase BP
b. Kidneys: conserve H20 to minimize further volume loss
What is the normal pH of plasma? HWat happens to proteins in regard to pH? What happens when the pH levels are too high or low?
1. Normal pH of plasma is 7.38-7.42
2. H+ changes can alter the 3-D structure of proteins
3. Abnormal pH effects the nervous system by:
a. Acidosis(low): neurons are less excitable; CNS depression
b. Alkalosis(high): hyperexcitable
How does pH maintain homeostasis? How does each effect pH?
a. protiens, phosphate ions, and hemoglobin
b. most buffers in the body combine with H+
-increases to remove CO2
3. Renal regulation
a. directly excrete or reabsorb H+
b. indirectly by rate of HCO3- reabsorbed or excreted
How does the kidney compensate for acidosis?