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HUBS EXAM 3 > the renal system > Flashcards

the renal system Flashcards

1
Q

structure of kidneys

A

shaped like a bean with a hilum (indentation) on the medial surface which is the entry/ exit point for vessels, nerves, lymph vessels and the uterus

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2
Q

function of the kidneys

A
  • regulate blood volume and blood pressure
  • adjusting water levels and electrolyte concentrations in plasma
  • stabilising blood PH levels
  • excreting wastes, drugs and toxins from the body
  • producing hormones
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3
Q

what is the structure and function of the ureter

A

slender tubes that enter the bladder. they are lined with transitional epithelium surrounded by a double layer of smooth muscle that produces peristalsis. they transport urine from the kidneys to the bladder and prevents back flow of urine as the bladder fills

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4
Q

what is the structure and function of the bladder

A

it is lined with transitional epithelium and surrounded by the detrusor muscle. it temporarily stores and expels urine from the body
it stretches to fill with urine and then contracts to push it out

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5
Q

what is the structure and function of the urethra

A
  • extends from the bladder to the exterior of the body, allowing urine to pass out of the body
  • it is a thin walled muscular tube lined with epithelium that has mucous glands
  • secrete alkaline mucus to protect against the acidic urine
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6
Q

what is the anatomy of the kidneys

A

they are protected by the lower ribs and diaphragm and are retroperitoneal. they are surrounded by 3 layers

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7
Q

what are the 3 layers surrounding the kidneys

A
  1. renal fascia- superficial layer of dense fibrous Ct which anchors to the surrounding abdominal tissue
  2. perirenal adipose capsule- fatty mass lying underneath the renal fascia that provides cushioning
  3. fibrous capsule- fibrous connective tissue capsule surrounding each kidney that prevents passage of substance into the kidney from the surrounding area
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8
Q

what is the outermost layer of the kidney

A

the renal cortex that lies underneath the fibrous capsule

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9
Q

what is the medulla composed of

A

medullary pyramids separated by renal columns.

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10
Q

what is the cortex composed of

A

numerous nephrons- the structural and functional units of the kidneys

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11
Q

what are nephrons

A

long tubular structures composed of a renal corpuscle and renal tubule.The various components of the nephron, and its associated capillary beds, allow the nephron to perform the necessary functions of filtration, reabsorption and secretion, which ultimately result in the formation of urine.These three major processes balance body fluids (e.g. plasma concentrations of electrolytes, blood pH, nutrient levels) and ensure the removal of wastes, drugs and toxins from the blood.

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12
Q

what are cortical nephrons (85% of nephrons)

A
  • reside mostly within the cortex of the kidney
  • short loops of henle that just dip into the medulla
  • 85% of nephrons
  • associated with peritubular capillaries
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13
Q

what are juxtamedullary nephrons (15% of nephrons)

A
  • associated with vasa recta
  • important for urine concentration
  • long loops of henle
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14
Q

what do the proximal and distal convoluted tubes do

A
  • proximal- site of bulk reabsorption including: 100% of nutrients reabsorbed, most of the water, electrolytes and bases are reabsorbed
  • distal- reabsorption of water and ions regulated by hormones
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15
Q

what are the 3 major capillary beds associated with nephrons

A
  1. glomerus
  2. peritubular capillaries
  3. vasa recta
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16
Q

what are the glomerulus capillary beds

A

a tuft of fenestrated capillaries found in the renal corpuscle of every nephron.
- its purpose is for the filtration of plasma. the glomerulus is fed and drained by arterioles- the afferent arteriole delivers blood into the glomerulus and the efferent arteriole drains the glomerulus

17
Q

what are the peritubular capillaries

A

continuous capillaries which surround the PCT, loop of henle and DCT of cortical nephrons, allowing reabsorption and secretion to occur in addition to internal respiration

18
Q

what are the vasa recta capillary beds

A

continuous capillaries surrounding the loops of henle of juxtamedullary nephrons and play a role in the concentration of urine- through the reabsorption of water and solutes- in addition to permitting internal respiration

19
Q

what are the 3 steps of the nephron process so they are able to perform the functions of filtration, reabsorption and secretion which forms urine

A
  1. glomerular filtration- the filtration of plasma through the glomerulus forming the filtrate, which travels through the renal tubule GFR= 125mL/min
  2. tubular reabsorption- water and filtered solutes that the body needs to keep move from the filtrate back into blood
  3. tubular secretion- additional waste products or excess substances are moved into the filtrate from blood
20
Q

how many litres of plasma do kidneys filter a day

A

180L of plasma and 1.5L of urine is produced daily

21
Q

what is glomerular filtration

A

it is a passive process in which pressure forces result in the movement of water and solutes from plasma through the filtration membrane of the renal corpuscle into the glomerular (bowman’s) capsule, creating the filtrate.

22
Q

what is the glomerular filtration rate

A

the volume of filtrate formed each minute by the kidneys. it is 125mL/ min

23
Q

what factors influence the glomerular filtration rate

A
  1. the total filtration surface area (surface area of all glomeruli in both kidneys)
  2. filtration membrane permeability
  3. pressure forces acting at the glomerulus which are:
    - glomerular hydrostatic (blood) pressure- blood pressure within the glomerulus which forces water and solutes out of the blood
    - capsular/filtrate hydrostatic pressure- pressure exerted by filtrate within the glomerular capsule which forces water and solutes back into the glomerulus
    - colloid osmotic pressure- attractive force of plasma proteins of water which pulls water toward them keeping fluid within the plasma
24
Q

what are the factors that regulate the glomerulus filtration rate

A
  1. auto regulatory mechanisms (intrinsic control)

2. extrinsic controls; sympathetic NS and renin-angiotensin-aldosterone system (RAAS)

25
Q

what is the auto regulatory mechanism

A
  1. myogenic mechanism: vasoconstriction or vasodilation of the afferent arteriole occurs in response to changes in systemic blood pressure to maintain adequate blood flow
  2. tubuloglomerular feedback mechanism; vasoconstriction or vasodilation of the afferent arteriole occurs in response to levels of sodium chloride in the filtrate
    - high sodium chloride levels stimulate vasoconstriction, reducing renal blood flow and GFR
    - low sodium chloride levels stimulate vasodilation, increasing renal blood flow and GFR
26
Q

what is the sympathetic NS and RAAS regulating mechanism (extrinsic control)

A

these stimulate vasoconstriction of the afferent arteriole, reducing renal blood flow and GFR. this ensures cardiac output can be redistributed, as necessary, to different body structures according to body activities (sympathetic NS) or to restore blood volume and blood pressure (sympathetic NS and RAAS)

27
Q

what is tubular reabsorption

A

the process of filtered substances being reabsorbed into the bloodstream. different substances are reabsorbed in different amounts in different locations of the nephron.

28
Q

what is tubular secretion. the PCT is the main site of tubular secretion, but it occurs in the DCT or collecting duct as well

A

the movement of substances from the blood into the filtrate to:

  • dispose of substances that were bound to plasma proteins and therefore nor filtered
  • eliminate undesirable substances or end products that were reabsorbed
  • rid the body of excess potassium
  • help maintain PH homeostasis by removing excess acids
29
Q

reabsorption in the proximal convoluted tubule

A

site of bulk reabsorption including:

  • 100% of nutrients reabsorbed
  • most of the water, electrolytes and bases are reabsorbed
30
Q

reabsorption in the loop of henle

A

only water and sodium chloride reabsorbed- this reabsorption is directly related to the concentration of urine

  • descending loop- only water is reabsorbed
  • ascending loop- only sodium chloride ions are reabsorbed
31
Q

reabsorption in the distal convoluted tubule (DCT) and collecting ducts

A

reabsorption of water and ions are regulated by hormones

  • aldosterone- stimulates sodium reabsorption in the DCT, water always follows due to the osmotic gradient
  • antidiuretic hormone- enhancing reabsorption of water based on the medullary osmotic gradient
  • parathyroid hormone- enhances reabsorption of calcium in the DCT, as necessary
32
Q

can urine amounts be adjusted

A

it can be adjusted to ensure adequate hydration in the body. this involves the action of ADH and is based on the establishment of the medullary osmotic gradient.

33
Q

the process of urine concentration

A
  • a concentration gradient exists between the urine and the surrounding renal medulla, and the renal medulla becomes progressively concentrated from the cortical end to the pelvic end.
  • the differences in concentration means water moves from less concentrated urine to more concentrated renal medulla. this can only happen if aquaporins are present within the collecting ducts.
  • ADH stimulates the insertion of aquaporins into the collecting duct, without ADH there are no aquaporins and water is not able to move out of the urine, therefore urine remains dilute.
34
Q

what is micturition

A

the expulsion of urine from the bladder due to contractions of the detrusor muscle. urine is continuously produced and filling the bladder, when the bladder holds 200-300ml a reflex action is stimulated that will lead to micturition

35
Q

what is the process of micturition

A
  1. bladder wall stretches, which initiates involuntary signals which stimulate bladder contraction and relaxation of internal urethral sphincter (smooth muscle)
  2. bladder wall stretches more, signals to the brain give conscious awareness of the need to urinate
  3. micturition occurs due to the voluntary signals that relax (open) the external urethral sphincter, allowing the pass of urine out of the body. conscious control of the external bladder can be maintained until the bladder reaches full capacity and then is will open automatically
36
Q

what is the medullary osmotic gradient

A

the osmolarity of the interstitial fluid of the renal medulla. the osmolarity is established by the flow of water out of the descending limb of the loop of henle and the flow of sodium chloride out of the ascending limb.

37
Q

how does the kidneys regulate blood volume and pressure

A

they do it via activation of the renin-angiotensin-aldosterone system (RAAS). detection of low blood pressure or low filtrate sodium chloride levels by the juxtaglomerular apparatus (JGA) of the nephron results in the release of the enzyme renin.

38
Q

how does RAAS regulate blood volume and pressure

A

renin causes angiotensinogen to be cleaved into angiotensin 1 which is then converted into angiotensin 2 by ACE. Angiotensin 2 then stimulates;
- release of aldosterone to increase reabsorption of sodium (water follows)
- release of ADH to increase water reabsorption
- increased thirst to stimulate increased consumption of water
- vasoconstriction to increase total peripheral resistance (TPR)
these actions result in an increase in blood volume and blood pressure

HUBS EXAM 3 (9 decks)

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