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online physiology > EXAM 3: SEC 3/Kidneys > Flashcards

EXAM 3: SEC 3/Kidneys Flashcards

1
Q

Function of the kidneys

A
  • regulation of water, inorganic ion balance, and acid-base balance (in corp with lungs)
  • removal of metabolic waste products and foreign chemicals from the blood and their excretion in urine
  • gluconeogensis
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2
Q

Production of hormones/enzymes

A
  • erythropotetin which controls erythrocyet production
  • renin, enzyme that controls formation of angiotensin and influences blood pressure and sodium balance
  • 1, 25 - dihydroxyvitamin D influences calcium balance
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3
Q

Urinary components

A
  • ureters, bladder, urethra
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4
Q

main function of ureters

A
  • transport urine from kidneys to bladder
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5
Q

main function of bladder

A

-stores urine until voided from body

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6
Q

urethra

A
  • carry urine from bladder to the outside of the body
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7
Q

Nephron

A
  • structural and function units of kidneys
  • each kidney has over 1 million
  • each consists of a glomerulus (tuft of capillaries) and a renal tubule
  • tubule forms cup around glomerulus called glomerular/Bowman’s capsule
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8
Q

Juxtaglomerular Cells

A
  • in arteriole wall the granular cells (JG) are enlarged smooth muscle cells that have secretory granules which contain the hormone renin
  • JG cells are mechanoreceptors (sense BP) in afferent arteriole
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9
Q

Macula Densa

A
  • group of tall, closely-packed cells that are adjacent to JG cells
  • macula densa cells are chemoreceptors that respond to changes in NaCl content of filtrate
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10
Q

Juxtaglomerular Apparatus

A
  • JG cells and Macula densa work in tandem and are critical regulators of blood pressure
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11
Q

Gross Anatomy

A
  • paired kidneys form a filtrate of the blood that is modified by reabsorption and secretion ; urine designated for excretion moves along ureters to bladder
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12
Q

Renal cortex

A
  • the outer layer of kidney and is site of glomerular filtration, as well as convulated tubules
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13
Q

Renal Medulla

A
  • inner part of kidney and is located along longer loops of Henle
  • drainage of the collecting ducts into renal pelvis and ureter
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14
Q

Glomerulus

A
  • capillaries of glomerulus are fenestrated, which allows large amounts of solute-rich fluid to pass - there shouldn’t be lots of protein in urine!
  • inner layer contains highly modified branching epithelial cells called podocytes
  • contains smooth muscle like cell = glomerular mesangial cell
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15
Q

Podocytes

A
  • terminate in foot processes which surround the basement membrane of glomerulus
  • the clefts between the foot processes are called filtration slits = where filtrate enters capsular space
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16
Q

Glomerular Mesangial Cell

A
  • help regulate blood flow in glomerulus by contraction and engulf macromolecules that get hung up during filtration
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17
Q

Juxtamedullary nephrons overview

A
  • long loop henle
  • involved in concentration of urine
  • found at border between cortex and medulla
  • about 15% of all nephrons are in this category
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18
Q

Cortical nephrons overview

A
  • most nephrons fall in this category

- short loop of henle

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19
Q

Basic renal processes for sodium and water

A
  • sodium reabsorption is active process occurring in all tubular segments except descending limb of loop of henle
  • water reabsorption is by diffusion and is dependent upon sodium reabsorption
  • water moves through aquaporin channels. pressure of awuaporin varies throughout the tubule segments
  • highly expressed in proximal nephron
  • absent in collecting ducts unless anti-diuretic hormone ADH active
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20
Q

Concentration of urine concentrations and volume

A
  • kidneys maintain plasma osmolarity at 300 mOsm

- it does this through countercurrent mechanisms (fluid in one tube flows oppositely of adjoining tube)

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21
Q

Why countercurrent works

A
  • descending loop of henle is relatively impermeable to solutes and freely permeable to water
  • ascending limb is permeable to solutes, not water
  • urea recycling contributes to medullary osmotic gradient
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22
Q

Dilute Urine

A
  • urine is normally diluted as moves through the ascending limb of loop of Henle
  • to secrete dilute urine, DCT and collecting duct cells secrete substances and then kidney just leaves it alone
  • osmolarity as low as 70 mOsm
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23
Q

Glucose concentration/secretion

A
  • the reabsorption of many organic substances such as glucose is accomplished with transport proteins
  • when concentration exceeds the capacity of the transporters, the excess is excreted in the urine
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24
Q

Capillaries Associated with Nephrons

A
  • nephrons are associated with 2 sets of capillaries
  • glomerular
  • pertibular
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25
Q

Glomerular capillaries

A
  • specialized for filtration
  • only capillaries in body that are fed and drained by an arteriole (afferent and efferent)
  • this allows the blood pressure in the capillary bed to be very high and it foreces fluid and solute out of blood into glomerular capsule
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26
Q

Pertibular capillaries

A
  • most of the filtrate is reabsorbed in renal tubule cells and returns to blood though pertibular capillaries
27
Q

Basic Renal Process

A
  • glomerular filtration
  • tubular secretion
  • tubular reabsorption
28
Q

Glomerular Filtration

A
  • glomerular filtration is passive process where hydrostatic pressures force the fluids and solute through a membrane. moves fluid from glomerular capillaries and into bowmans capsule
  • the glomeruli in kidney are much more efficient filter than other capillary beds in the body because large SA and permeable to water and solutes
  • during filtration, important to keep plasma proteins in plasma to maintain osmotic pressure
  • if see blood cells or protein in urine then theres a problem with filtration membrane (untreated = renal disease)
29
Q

Net Flomerular filtration pressure

A

P(GC) = P(BS) = piGC

30
Q

glomerular filtration

A
  • refers to the movements of fluid and solutes from glomerular capillaries into bowmans space
31
Q

tubular secretion

A
  • refers to the secretion of solutes from the pertibular capillaries into the tubules
32
Q

Tubular reabsorption

A
  • begins as soon as filtrate enters the tubular cells
  • paracellular transport occurs between cells (even though they have tight junctions) and is seen mainly with ions
  • transport can be active (requires ATP) or passive (no ATP)
  • moves substrances from pertibular capillaries into tubular lumen
33
Q

sodium reabsorption

A
  • Na+ is most abundant cation in filtrate
  • Na+ reabsorption is almost always active transport
  • active pumping of Na+ generates an electrochemical gradient that couples to passive entrance of other substances via co-transporters
34
Q

Tubular secretion important for:

A
  • disposing of drugs and drug metabolites
  • eliminating undesired substrances or end products that have reabsorped via passive processes (urea and uric acid)
  • removing excess K+
  • controlling blood pH
35
Q

metabolism by the tubule

A
  • renal tubule cells can synthesize glucose during fasting and add it to the blood, and they can catabolize many organic compounds
36
Q

regulation of membrane channels and transporters

A
  • regulation of reabsorption and/or secretion of many substances is achieved by regulating the activity or concentrations of the appropriate transport proteins in response to hormones and paracrnie/autocrine factors
37
Q

Division of labor in tubules

A
  • majority of reabsorption is by proximal tubule and loop of henle
  • extensive reabsorption by proximal tubule and henle’s loop ensures that the masses of solutes and volume of water entering tubular segments beyond henle’s loop are small
  • distal segments do fine-tuning for most substances, determining final amounts excreted in urine by adjusting their rates of reabsorption and in a few cases secretion
38
Q

renal clearance (RC)

A
  • this is the volume of plasma cleared of a substance in one minute (ml/min)
  • creatine can be used but is less accurate, it is freely filtered but also secreted in small amounts
39
Q

RC = UV/P

A
  • RC = renal clearance
  • U = concentration of the substance in urine
  • V = flow rate of urine formation
  • P = concentration of substance in the plasma
40
Q

Micturition

A
  • urine is formed in renal tubules then travels through calyxes until drains into renal pelvis
  • fluid chains from renal pelvis to ureter, leading to urinary bladder
  • bladder stores urine until excreted from body by micturition reflex
  • micturition is initiated by a nervous reflex which causes the smooth muscle of bladder walls to contract and expel urine
  • goes through 2 sphincters
    1) internal urethral sphincter (smooth muscle)
    2) external urethral sphincter (skeletal muscle)
41
Q

Incontinence

A
  • involuntary release of urine
  • most common types are stress incontinence from sneezing, coughing or exercise, and urge incontinence associated with desire to urinate
  • more common in women
  • meds can often help ‘stress’
  • severe cases may require surgery
  • can be treated with drugs but often have side effects
  • irritation to bladder or urethra can cause ‘urge’
42
Q

Inulin

A
  • because filtered but not reabsorbed, or secreted, can be used to estimate glomerular filtration on rate
43
Q

Creatine

A
  • product of muscle metabolism and produced daily
  • gets into nephrons via glomerular filtration
  • 10-15% lost in urine a day
  • NOT reabsorbed once gets into nephron
44
Q

if GFR decreases in kidney disease

A

plasma creatine increases

45
Q

Concentrated Urine

A
  • ADH uses cAMP systems to cause the insertion of aquaporins into the membranes of the principle cells of collecting ducts
  • if water flows out of collecting ducts to be absorbed by the body
  • urine can reach 1200 mOsm
46
Q

Glomerular Filtration Rate

A
  • volume of filtration formed each minute
  • affected by volume of surface available, filtration membrane permeability and NFP, blood pressure/blood flow to glomerular capillaries
  • directly proportional to NFP. in absence of regulation, increase in systemic blood pressure means increase GFR
47
Q

Renal regulation of calcium and phsophate

A
  • calcium reabsorption increase by parathyroid hormone

- phosphate reabsorption decreases by parathyroid hormone

48
Q

glomerulus/bowmans capsule job

A
  • forms ultrafiltrate of plasma
49
Q

proximal tubule job

A
  • bulk reabsorption of solutes and water, secretion of solutes (except K+) and organic acids/bases and secretion of urea
50
Q

descending limb job

A
  • bulk reabsorption of water
51
Q

ascending limb job

A
  • bulk reabsorption of NaCl
52
Q

distal tubule and cortical collecting ducts job

A
  • fine tuning of the reabsorption / secretion of small quantity of solute remaining
53
Q

Cortical and medullary collecting ducts job

A
  • fine-tuning of water reabsorption and reabsorption of urea
54
Q

Diuretics

A
  • substances that promote loss of Na+ and water
  • alcohol inhibits release of ADH
  • osmotic diuretics –> high glucose loads in urine
  • loop diuretics are most powerful diuretics because inhibit formation of medullar gradient
  • hydrochlorithiazide acts on the distal collecting ducts
  • spironolactone is an aldosterone receptor antagonist known as K+ sparing diuretic. acts because K+ in urine is from aldosterone-driven active tubular secretion into the late DCT and collecting ducts
55
Q

Buffering of Hydrogen Ions in body

A
  • major extracellular buffer = CO2 / HCO3- system

- major intracellular buffer = phosphate and proteins

56
Q

Integration of Homeostatic controls

A
  • kidneys and respiratory system work together to regulate hydrogen ion concentrations
57
Q

Renal Mechanisms

A
  • the kidneys eliminate or replenish hydrogen ions from the body by altering plasma bicarbonate concentration
58
Q

Responses to Acidosis

A
  • H+ is secreted to reabsorb all filtered HCO3-
  • still more H+ secreted, contributing to new HCO3- to the plasma as H+ excreted bound to nonbicarbonate urinary buffers such as HPO4-
  • tubular glutamine metabolism and ammonium excretion are enhanced, also contributing new HCO3- ion than usual added
  • overall result: move new HCO3- ion than usual added to blood, and plasma bicarbonate increases, compensating for acidosis
59
Q

Responses to Alkalosis

A
  • overall result: plasma bicarbonate concentration decreases thereby compensating for alkalosis. urine is alkaline > 7.4
60
Q

Kidney disease

A
  • diseases affecting kidneys = bacterial infections, hypertension, and diabetes
  • end stage renal disease is one of the leading causes of death in the world and the leading cause of needed renal transplants
61
Q

Clinical issues with kidneys

A
  • severe cases when kidney swells, abscessess for and pelvis fills with pus. can result in irrepairable damage
  • antibiotics are used to treat this condition
  • renal failure and anuria can result from any situation where nephrons cease to function, including acute nephritis, transfusion reactions, and crash injuries
62
Q

Anuria

A
  • abnormally low urine output (less than 50ml/day)

- may indicate that glomerular blood pressure is too low to cause filtration

63
Q

if issue affects entire kidney

A

pyelonephritis

64
Q

infection of renal pelvis that occurs via bacteria

A

pyelitis

online physiology (13 decks)

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