Question | Answer |
kidneys are (___) organs | homeostatic |
filters and maintain body fluids | kidneys |
the kidneys filter how many liters of fluid/day? | ~200 |
retain important molecules removes toxins, waste, excess ions regulates fluid volume, pH, salts have endocrine function | kidneys |
what does the kidneys produce? | renin (regulates b.p.) - erythropoietin (stimulates R.B.C. production |
metabolizes vitamin D to active form | kidneys |
What shape and size is the kidneys? | bean-shaped-size=bar of soap |
The kidneys are (____), which means they are a free floating organ, but they get (____). | -retroperitoneal -some protection from the rib cage |
What is the renal hilus? | vertical cleft on medial surface of kidney. Entry site for: blood vessels, lymphatics, nerves. |
What is a strong barrier on the kidneys surface? | renal capsule |
a fatty mass that cusions the kidneys | adipose capsule |
dense fibrous connective tissue - anchors kidneys | renal fascia |
outer granular tissue of the kidneys | renal cortex |
reddish-brown, cone shaped masses or medullary (renal pyramids) appear striped due to parallel bundles of tubules | Renal medulla |
cortical tissue between pyramids positive pyramid = lobe | renal columns |
funnel-shaped tube continuous w/ ureter at hilus | renal pelvis |
branches into major clyces - divide into minor calyces - enclose papillae/apex of pyramid | renal pelvis |
collect urine-pelvis-ureter-bladder | calyces |
urine propelled by peristalsis of (____). | calyces, pelvis, and ureter. |
deliver 25% of total cardiac output/min | Renal Arteries |
What does the renal arteries divide into? | -5 segmental artieries (enter at hilus)
-Divide into lobar arteries
-Divide into interlobar arteries (between pyramids)
-Divide into arcuate arteries
-Divide into cortical radiate arteries
-Fan out in cortical tissue |
(____) trace path of arterial supply in reverse but no lobar or segmental veins. | Veins |
Kidneys have a nerve network or renal plexus controlled by? | sympathetic fibers |
1 million per kidney | nephrons |
what is the nephrons function? | to form urine |
several nephrons connect up to? | 1 collecting duct. |
What does a nephron consist of? | -a glomerulus
-a renal tubule - end is cup-shaped called glomerular (bowman's) capsule - completely surround glomerulus
-glomerulus and glomerular capsule=renal corpuscle |
Endothelium of glomerulus is? | fenestrated - leaky |
Because the endothelium of the golmerulus is leaky, what does this allow? | -allows large volumes of fluid to filter from blood into glomerular capsule
-this filtrate is unprocessed urine
-gets processed in kidney tubules to urine |
In the edothelium of glomerular capsule the (____) is simple squamous epithelium. | outer parietal layer |
In the endothelium of glomerular capsule the (____) has unique epithelia cells-octopus like-podocytes | inner visceral layer |
-legs of octopus have extensions (pedicles) -interdigitate with pedicles of adjacent podocytes -between pedicles are filtration slits or slit pores | the inner visceral layer of the endothelium of glomerular capsule |
-Cuboidal epithelial cells -Actively reabsorb solutes -secrete molecules -have dense microvilli | PCT |
-simple squamous epithelia -freely permeable to water | Loop of Henle (thin segment) |
-Cuboidal -No microvilli -Secrete solutes into filtrate -little solute reabsorption | Loop of Henle (thick segment) and DCT |
-85% of nephrons in the kidney | Cortical neprhons |
-located in cortex-except for tip of loop of Henle | Cortical nephrons |
-located close to medulla -loop of Henle goes deep into medulla -very long thin segments -role is to concentrate urine | juxtamedullary nephrons |
-arise from interlobar arteries -feed the glomerulus --has high b.p. --easily forces fluid and solutes out of glomerulus | afferent arterioles |
drain glomerulus | efferent arterioles |
-arise from efferent arterioles draining glomeruli -cling to renal tubules -adapted for absorption -low pressure -porous -readily absorb solutes and water | Peritubular capillaries |
have an important role in forming concentrated urine | efferent nephrons from juxtamedullary nephrons that form a vasa recta |
glomerulus produces a filtrate, what reclaims most of that filtrate? | peritubular capillaries and vasa recta |
a portion of the DCT is nestled between the afferent and efferent arterioles of glomerulus. | juxtaglomerular apparatus |
in walls of arterioles are (____) | juxtaglomerular cells |
what are the juxtaglomerular cells and what do they do? | -large smooth muscle cells containing renin -sense blood pressure in afferent arterioles |
(____) acts to increase blood pressure. | renin |
Renin converts angiotensin into (1), then (2) converts angiotensin I into (3). It acts to (4) which (5) or as a (6) which (7). | 1. Angiotensin I
2. ACE
3. Angiotensin II
4. Stimulate the adrenal cortex to release aldosterone
5. stimulates renal tubule to reclaim more Na from filtrate
6. Vasoconstrictor
7. constricts efferent arteriole |
When angiotensin II acts as a vasoconstictor and constricts the efferent arteriole what happens? | dec blood flow out of the glom. which increases glom. hydrostatic pressure, whic increases GFR. |
-columnar cells in distal tubule next to JG cells
-Are chemoreptors and sense filtrate flow
-Act to regulate rate of filtration in kidneys | Macula Densa |
chemoreceptors that respond to changes in the NaCl content of the filtrate | Macula Densa |
What is unprocessed filtrate? | like plasma but no proteins |
As unprocessed filtrate flows thru the tubules? | most water, nutrients, and ions are reclaimed. Also all glucose. Urine is waste and XS substances. |
What does the urine formation process include and how is it regulated? | 1. glomerular filtration
2. tubular reabsorption
3. tubular secretion
Regulated by renal and hormonal controls |
Characteristics of glomerular filtration | a. passive b. non-selective c. due to hydrostatic pressure which is high ~55 mm Hg |
The rate of glomerular filtration is dependent of (____). | forces that increase filtration verses forces that decrease it. |
Forces that increase glomerular filtration | glomerular hydrostatic pressure |
forces that decrease glomerular filtration | -osmotic pressure of blood -hydrostatic pressure in glom capsule |
The net effect of the forces of glomerular filtration determines that the overall filtration pressure is? | 55mmHg - (30mmHg and 15mmHg) = 10mmHg |
A net filtration pressure of (1) produces a glomerular filtration rate of (2). | 1. 10mmHg 2. ~180L/day |
What stops glomerular filtration? | A 15% drop in glomerular pressure |
regulates diameter of afferent arterioles | renal autoregulation |
smooth muscle contracts when stretched | Myogenic regulation |
During myogenic regulation, if b.p. increases and vessels stretch, then what happens? | vasoconstriction-decrease flow-maintain GFR. |
During myogenic regulation, if b.p. decreases which causes decreased blood flow, then what happens? | vasodilation-increases flow-maintain GFR. |
Macula densa cells detect filtrate flow and osmotic levels | Tubuloglomerular feedback |
Due to the tubuloglomerular feedback mechanism, if a large volume of filtrate is produced or high osmolarity is reached, what happens? | this causes the M.D. cells to release a vasoconstrictor chemical that causes intense constriction of the afferent arteriole. This constriction hinders blood flow into the glomer., which decreases the NFP and GFR, allowing more time for filt. processing. |
Due to the tubuloglomerular feedback mechanism, if a low volume of filtrate is produced or low osmolarity is reached, what happens? | ATP release is inhibited causing vasodilation of the afferent arterioles. This allows more blood to flow into the glomerulus, thus increasing the NFP and GFR. |
-vasoconstriction restores GFR -Aldosterone lowers osmolarity | Renin-angiotensin mechanism |
regulates renal flow only during extreme stress e.g. shock | Sympathetic nervous system |
-vasoconstriction -shunts blood to vital organs -reduces fluid loss -helps maitain b.p | Sympathetic nerves |
Tubular reabsorption occurs in the? | PCT |
-mostly transcellular -sodium most abundant ion in filtrate -actively transported from tubule cell by sodium/potassium ATPase pump --produces electrochemical gradient that pulls sodium into cell from filtrate. | Tubular reabsorption-PCT |
Inside of the tubule cell is left with a? | small negative charge |
(____) follows salt | water |
Because water follows salt, it is reabsorbed by (1), and it is called (2). | 1. diffusion (osmosis) 2. obligatory water reabsorption |
What types of molecules does the gradient caused by the sodium/potassium pump draw across tubule cells? | glucose, amino acids, lactate, vitamins |
How does the sodium/potassium pump draw some molecules across tubule cells? | The carrier that transports sodium across luminal membrane is a symport, hence it will also transport another molecule in the same direction. |
In the loop of Henle, water is (1). Water can leave the (2). Solutes (NaCl) can leave the (3) via (4). | 1. reabsorbed by osmosis 2. descending limb only. 3. ascending limb only. 4. a sodium/potassium/2chloride symporter |
What is the job of the vasa recta? | to maintain salt concentration in the kidney |
Na/Cl symporters reabsorb Na and Cl in the?
What is also reabsorbed? | DCT and collecting ducts
Water |
In the DCT most reabsorption is regulated by?
Water is controlled by?
Na reabsorption controlled by? When? | hormones
ADH released from posterior pituitary when blood is too concentrated.
aldosterone from adrenal cortex when low blood volume, low blood pressure, or low Na in cell fluids. |
Some substances move from blood of peritubular capillaries-tubule cells-into filtrate. | Tubular secretion |
Most secretion occurs in the? | PCT |
Examples of substances of tubular secretion? | H, K (controlled by aldosterone), creatine, ammonium ions, penicellin, Phenobarbital. |
Secretion is important for? | excreting xs K ions, controlling blood pH. |
How much of filtrate is reabsorbed by PCT? | 65% |
The concentration of body fluids is measured in? | milliosmols (mOsm) |
What is a milliosmol? | number of millimoles of a substance dissolved in 1 liter water. |
Kidneys must keep solute concentration of body fluids around? | 300 mOsm |
Kidneys regulate urine concentration via the? | countercurrent mechanism |
what are the basics of the countercurrent mechanism of the kidney? | -filtrate flowas in one direction through long loop of henle -blood flows in opposite direction through vasa recta -this countercurrent establishes and maintains an osmotic gradient. |
What causes water to leave the descending limb of the loop of henle? | -high osmolarity of interstitial fluid --from NaCl exiting ascending limb --from urea exiting lower collecting duct |
In the presence of (____) more NaCl is reabsorbed from DCT and collecting ducts. | aldosterone |
Due to the countercurrent mechanism, what is the molality of the filtrate at the base of the loop of Henle? | 1200 mOsm |
the vasa recta is different from a normal capillary bed running thru an organ because? | a normal capillary bed would remove an osmotic gradient, but the vasa recta helps to maintain osmotic gradient. |
The desceding limb of vasa recta? | loses water and gains salt so blood becomes more salty or more concentrated. |
The ascending limb of the vasa recta? | gains water and loses salt so blood becomes less salty or less concentrated. |
Approximately how much intracellular fluids do we have? | 25-30L |
Approximately how much extracellular fluids do we have? | 15-20L |
Approximately how much total body fluids do we have? | 50L |
examples of extracellular fluids | 1. plasma 2. Interstitial fluid (IF)-i.e. fluid between cells -Includes: lymph, CSF, eye fluids, synovial, serous, hormone secretion, and GI secretion |
Body fluids are either (1) or (2). | electrolytes or nonelectrolytes |
-no electrical charge -mostly organic molecules-e.g. glucose, lipids, creatine, urea -covalently bonded-do not dissociate in solution | Nonelectrolytes |
-electrically charged -include inorganic acids, bases, and some proteins | electrolytes |
electrolyte concenctrations are expressed in? | milliequivalents/liter=the number of electrical charges in 1 liter of solution. |
how many milliequivalents/liter is Na if the concentration is 3300mg/L? | 143 mEq/L |
in extracellular fluids, the major cation is (1) and the major anion is (2)? | 1. Na 2. Cl |
How much is our water intake per day?
-What percent from water/liquids?
-What percent from food?
-What percent from cellular metabolism? | ~2.5L per day
-60%
-30%
-10% |
How and what percent is our water output? | -evaporation from lungs and skin 28%
-perpiration 8%
-feces 4%
-urine 60% |
(____) in hypothalamus trigger thirst. | osmoreceptors |
How is our water balance regulated?
1-4 | -osmoreceptors in hypothalamus trigger thirst
-kidneys increase or decrease fluid loss
-body temperature regulates perspiration
-diet provides very small changes in water loss via feces except during GI infection-diarrhea-vomiting |
refers to salts in body fluids - e.g. NaCl, CaHPO4 | electrolyte balance |
essential for:
-neuromuscular excitability
-secreation
-membrane permeability
-controlling fluid movement | electrolyte balance |
How do salts enter and exit the body? | enter the body in fluid and food; exit the body in perspiration, feces, and urine. |
What is the role of sodium? | -sodium salts are 90-95% of all solutes in ECF i.e. NaHCO3, NaCl
-contribute 280 mOsm of total 300 mOsm in ECF.
-normal plasma concentration is 142-143 mEq/L
-sodium is primary controller of ECF volume (water follows salt) |
Regulation of Na levels:
-PCT reabsorbs (1)
-Loop of Henle reclaims (2)
-DCT and collecting ducts (3)
-Na lost in xs perspiration | 1. 65% of Na in renal filtrate
2. 25%
3. reclaim remaining 10% only if Aldosterone is present. |
What is the role of Atrial natriuretic peptide in regulation of Na levels? | -promotes Na excretion
-inhibits Na reabsorption in collecting ducts
-Inhibits release of ADH, renin, and aldosterone |
Main intracellular cation | potassium (K) |
What cation can be extremely toxic | K+ = Kevorkian |
How much K is reabsorbed by nephron? | 85% |
how much K is lost in urine regardless of need? | 15% |
(1) increases K secretion in (2) | 1. aldosterone
2. cortical collecting ducts-i.e. as Na reabsorbed, K is excreted |
99% of body's Ca is in what form? | is in bones in salt form - CaPO4 |
Why is calcium needed? | -blood clotting
-cell membrane permeability
-muscular contractions
-neurosecretion |
how is Ca regulated? | by parathyroid hormone (PTH) and calcitonin |
-activated osteoclasts to breakdown bone and release Ca2+ into blood
-increases intestinal absorption of Ca
-increases reabsorption in renal tubules | PTH |
-released by thyroid gland when blood Ca increases
-Encourages bone deposition of Ca | Cacitonin |
bone formin, decreases blood Ca2+ levels | Calcitonin |
second most abundant intracellular cation | Magnesium |
What is magnesium neededed for? | carbohydrate and protein metabolism
-cardiac function
-neurotransmission
-neuromuscular activity
-cofactor for ATP |
What is the cofactor for ATP? | Magnesium |
1. How much Mg is in bone?
2. How much of filtered Mg is excreted?
3. The control of magnesium is? | 1. 50%
2. 3-5%
3. poorly understood |
What is the major anion? | chloride |
what helps Na maintain osmotic pressure? | chloride |
how much of filtered Cl is reabsorbed? | 99% |
How is Cl reabsorbed and transported? | in PCT Cl reabsorbed passively (paracellular)
in DCT Na and Cl transport is coupled |
arterial blood pH is? | 7.4 |
venous blood and ISF pH is? | 7.35 |
ICF pH is? | 7.0 |
why is ICF ph 7.0? | due to acidic metabolites and Carbon dioxide |
H concentration in blood is regulated by? | -chemical buffer systems
-respiration
-kidneys
-proteins
-HCO3 |
what is the formula for pH? | pH = -log[H+] |
acids are? | proton donors |
bases are? | proton acceptors |
what happens when you increase H? decrease? | -increase acidity, lower pH -decrease acidity, greater pH |
What are the 3 chemical buffer systems in the body? | 1. Bicarbonate 2. Phosphate 3. Proteins |
important ECF buffers | 1. Bicarbonate 2. Proteins |
gives off H in bicarbonate buffer system? | H2CO3 (carbonic acid) |
takes up H in bicarbonate buffer system? | HCO3 (carbonate) |
If ECF becomes more acidic what happens? | H+ + HCO3 = H2CO3, so H+ ions are mopped up and pH will not change. |
If ECF becomes more alkali what happens? | H2CO3 = H+ + HCO3 |
Concentration of HCO3 in ECF is regulated by? | kidneys |
concentration of H2CO3 in ECF is regulated by? | respiration as: CO2 + H2O = H2CO3 |
(____) are very effective in urine and ICF | Phosphate buffers |
what are the components of phosphate buffers? | dihydrogen phosphate - monohydrogen phosphate |
Most plentiful and powerful source of buffers in plasma and ICF | proteins |
proteins are made up of? | amino acids |
Example of how amino acids (proteins) mop up H+ when levels rise? | COO- + H+ = COOH |
Example of how amino acids (proteins) give off H+ when levels fall? | NH3+ = NH2 + H+ |
All cases of acidosis and alkalosis are classed as either? | respirator or metabolic depending on the cause. |
most common cause of acid-base imbalance | respiratory acidosis |
-respiration is insufficient-e.g. pneumonia, cystic fibrosis -blood CO2 rises -pH falls | respiratory acidosis |
-CO2 is eliminated faster than it is produced -respiration is too fast-hyperventilation -blood CO2 falls -pH rises | respiratory alkalosis |
normal blood CO2 is? | 35-45 mmHG |
when acid-base imbalance is not caused by CO2 levels the problem is? | metabolic |
Which is less common, respiratory alkalosis or metabolic alkalosis? | metabolic alkalosis |
-low blood HCO3 levels -causes-too much alcohol (metabolized to acetic acid), diarrhea (excessive loss of HCO3), too much lactic acid -blood HCO3 low -pH low | metabolic acidosis |
-less common -causes-loss of stomach acids due to vomiting, GI cleaning, overdosing on antacids -blood HCO3 is high -pH high | metabolic alkalosis |
causes-loss of stomach acids due to vomiting, GI cleaning, overdosing on antacids | metabolic alkalosis |