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the kidneys Flashcards

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1
Q

what is the most important function of the kidney

A

homeostatic regulation of the water and ion content of the blood (known as salt and water balance or fluid and electrolyte balance)

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2
Q

kidney functions can be divided into six general areas

A
  1. regulation of ECF volume and BP: decreased ECF lead to decreased BP
  2. regulation of osmolarity: maintain around 290 mOsM
  3. maintain ion balance: balance dietary intake with urinary loss
  4. homeostatic regulation of pH: by removing H+ and conserving bicarbonate ions
  5. production of hormones: synthesize erythropoietin for RBC synthesis
  6. excretion of wastes: remove waste products like creatinine, urea, and uric acid
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3
Q

urine production starts when

A

water and solutes move from plasma into the nephrons of the kidneys

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4
Q

nephrons

A

modify the fluid, when then becomes urine and moves into the ureters (tube that links a kidney to the bladder)

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5
Q

each kidney has a ureter that transports

A

urine to the urinary bladder

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6
Q

the bladder stores urine until it is expelled through the

A

urethra

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7
Q

women are more prone to urinary tract infections due to

A

the shorter urethra and proximity to bacteria from large intestine

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8
Q

what is the most common cause of UTIs

A

the bacterium e. coli found in the large intestine

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9
Q

the kidneys are responsible for urine formation and are located on

A

either side of the spine about the level of 11th and 12th ribs just above the waist. they are outside the abdominal cavity (retroperitoneal)

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10
Q

the concave surface of each kidney faces the

A

spine, where renal blood vessels, nerves, lymphatics, and ureters emerge

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11
Q

renal arteries

A

branching from the abdominal aorta, supply blood to the kidneys, while renal veins carry blood from the kidneys to the inferior vena cava (deoxygenated)

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12
Q

the kidneys receive how much of the cardiac output

A

20-25% highlighting the important of their high blood flow for renal function

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13
Q

the kidney’s interior is organized into two layers

A

an outer cortex and an inner medulla

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14
Q

nephrons

A

the functional units of the kidney, are microscopic tubules that form these layers

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15
Q

80% of nephrons are

A

entirely within the cortex (known as cortical nephrons)

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16
Q

the remaining 20% of the nephrons

A

extend into the medulla (juxtamedullary nephrons)

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17
Q

each kidney contain about how many nephrons

A

1 million

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18
Q

blood enter the kidney through

A

the renal artery, flows into smaller arteries then into arterioles in the cortex

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19
Q

the arrangement of blood vessels in the kidney forms

A

a portal system, consisting of two capillary beds inseries

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20
Q

gout

A

is a metabolic disease marked by high uric acid levels in the blood, causing inflammation and severe pain (in feet, ankles, and knees)

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21
Q

uric acid crystal (from gout) can also form

A

kidney stones in the renal pelvis

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22
Q

blood exits the glomerulus via

A

an efferent (away) arteriole and enters the pertubular capillaries, which surround the tubule

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23
Q

in juxtamedullary nephrons, the peritubular capillaries that extend into the medulla are called

A

vasa recta

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24
Q

peritubular capillaries converge to form

A

venules and small veins, which send blood out of the kidney through the renal vein

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25
the renal portal system filters
fluid out of the blood into the nephron lumen at the glomerular capillaries and reabsorbs fluid from the tubule lumen back into the blood at the peritubular capillaries
26
the kidney tubule is composed of
a single layer of epithelial cells with apical surfaces folded into microvilli and the basal side resting on a basement membrane
27
cell to cell junctions in the tubule are mostly
tight but some allow selective ion permeability
28
where does the nephron start?
with bowman's capsule, a hollow structure surrounding the glomerulus. the endothelium of the glomerulus is fused to bowman's capsule, allowing fluid to pass directly into the tubule lumen
29
the renal corpuscle
is the combination of the glomerulus and bowman's capsule
30
filtered fluid flow from bowman's capsule into the proximal tubule then into the loop of Henle (a hairpin shaped segment divided into two limbs)
the two limbs has a descending limp and an ascending limb with thin and thick segments
31
fluid then moves into the distal tubule, which drains into a larger tube called
the collecting duct. the distal tubule and collecting duct together form the distal nephron.
32
collecting ducts pass through
the cortex and the medulla, draining into the renal pelvis. from there urine flows into the ureter for excretion
33
the nephron twists and fold, with the ascending limp of the loop of Henle passes between
afferent and efferent arterioles forming the juxtaglomerular apparatus. this allow form paracrine communication, crucial for kidney auto regulation.
34
what are the three basic processes occurring in the nephron:
filtration, reabsorption, and secretion
35
filtration involves the movement of fluid from the blood into the
lumen of the nephrons an occurs only in the renal corpuscle
36
the filtered fluid enters the lumen of the nephron and is consider part of the body's
external environment (substances in the filtrate are destines for excretion unless it's reabsorbed)
37
reabsorption move substances from the lumen of the tubule back into the blood in the
peritubular capillaries
38
secretion selectively removes molecules from the blood and assed them to the
filtered fluids in the tubule lumen
39
secretion is more selective than
glomerular filtration and typically involved membrane proteins to transport molecules across the tubule epithelium
40
in the proximal tubule 70% of the filtrate volume is reabsorbed, the primary function
is the isosmotic reabsorption of solutes and water
41
the loop of Henle reabsorbs more solute than
water making the filtrate hyposmotic and reducing its volume to 18 liters/day
42
the distal tubule and collecting duct fin-tune salt and water balance under
hormonal control, determining the final urine volume and osmolarity
43
secretion involves
moving solutes from plasma to the tubule lumen while excretion is the removal of substance from the body
44
filtration occurs in the
renal corpuscle, while reabsorption and secretion happen along the tubule affecting the final urine composition
45
the amount excreted in the urine is calculated as
amount excreted = amount filtered - amount reabsorbed + amount secreted
46
filtration of plasma into the kidney tubule is the initial step in urine formation, producing a filtrate similar to
plasma but without plasma proteins
47
blood cells typically remain in the
capillary, so the filtrate consists of mainly water and dissolved solutes
48
only about one-fifth of the plasma entering the kidneys filters into the nephrons, the rest
including most plasma and blood cells, continues into the peritubular capillaries
49
the filtration fraction is the
percentage of renal plasma flow that filters into the tubule
50
filtration in the renal corpuscle involves three barriers:
the glomerular capillary endothelium, the basement membrane, and the epithelium of Bowman's capsule
51
the glomerular capillary endothelium is fenestrated (has windows)
allowing most plasma components to pass through while preventing blood cells form leaving. the glycocalyx negatively charges glycoprotein layer, repels negatively charged plasma proteins
52
the basement membrane, an acellular extracellular matrix layer, contains
negatively charged glycoproteins and collagen, excluding most plasma proteins
53
the epithelium of Bowman's capsule consists of podocytes with foot precesses that interlace to form arrow filtration slits,
closed by a slit diaphragm containing proteins like nephrin and podocin. Mutation in these proteins can lead to congenital kidney diseases where proteins leak in the urine
54
glomerular mesangial cells support the capillaries, influence
filtration by altering the surface area of filtration slits, and secretes cytokines involved in the immune and inflammatory responses. disruptions in the mesangial cell function are linked to kidney diseases
55
diabetic nephropathy begins with increased
glomerular filtration, followed by proteinuria, indicating an altered filtration barrier. later stages filtration rates decline due to thickening of the glomerular basal lamina
56
abnormal growth of mesangial cells compresses glomerular capillaries, reducing
blood flow and further decreasing glomerular filtration.
57
patients with advanced diabetic nephropathy often require
dialysis and eventually may need a kidney transplant
58
filtration across the glomerular capillaries is driven by three main pressures
capillary blood pressure, capillary colloid osomotic pressure, and capsule fluid pressure
59
capillary blood pressure (Ph)
averages 55 mm Hg and favors filtration into Bowman’s capsule, maintaining a higher pressure than opposing forces along the capillaries.
60
colloid osmotic pressure (pi)
inside the glomerular capillaries, averaging 30 mmHg is due to plasma proteins and favors fluid movement back into the capillaries
61
hydrostatic fluid pressure (Pflu) in bowman's capsule
averages 15 mmHg and opposes filtration by creating resistance to fluid movement into the capsule
62
the net driving force for filtration is 10 mmHg which combined with leaky nature of the glomerular capillaries, results in
rapid fluid filtration
63
glomerular filtration rate (GFR)
is the volume of fluid filtered into Bowman's capsule per unit time, averaging 125 mL/min or 180 L/day
64
the kidneys filter the entire plasma volume approximately
60 times a day, necessitating significant reabsorption to prevent plasma depletion
65
GFR is influenced by net filtration pressure and the filtration coefficient, which depends on the
surface area of the glomerular capillaries and the permeability of the filtration slits
66
filtration pressure is primarily determined by
renal blood flow and blood pressure
67
the filtration coefficient is comparable to factors influencing gas exchange at the alveoli,
such as partial pressure differences, surface area, and permeability of diffusion barrier
68
most reabsorption occurs in the proximal tubule with
additional reabsorption in the distal segments of the nephrons
69
regulated reabsorption in the distal nephron
allows selective return of ions and water to the plasma to maintain homeostasis
70
the high filtration rate (GFR) services two main purposes
1. main foreign substances are filtered into the tubule and not reabsorbed, aiding rapid clearance from plasma 2. desirable nutrients like glucose are filtered in large amounts but efficiently reabsorbed by transporters in the proximal tubule
71
the filtrate in the proximal tubule has the same solute concentrations as
extracellular fluid, necessitating active transport to create concentration or electrochemical gradients
72
active transport of Na+ from the tubule lumen to the ECF fluid creates a
transepithelial electrical gradient, making the lumen more negative than the ECF
73
anions follow the positively charged Na+ out of the lumen, and
water follow osmotically due to the resulting concentration gradient
74
the removal of Na+ and anions form the lumen dilutes the
luminal fluid and increased the ECF concentration causing water to leave the tubule by osmosis
75
the loss of volume from the lumen increase the concentration of
remaining solutes (K+, Ca2+, and urea), leading to higher solute concentration in the filtrate
76
when solute in the kidney tubule are more concentrated than the ECF, they can move out of the tubule if
the wall is permeable
77

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