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Physiology 300L Renal > PHS 303 Renal Physiology > Flashcards

PHS 303 Renal Physiology Flashcards

1
Q

What is excretion?

A

Removal of metabolic waste products, nitrogenous waste products, poisons and excess drugs

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2
Q

List the main excretory organs

A

Kidney
Ureter
Bladder
Urethra

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3
Q

What is metabolic acidosis

A

A condition in which too much acid accumulates in the body.
Causes of metabolic acidosis can include build-up of body toxins, kidney failure and ingestion of certain drugs or toxins, such as methanol or large doses of aspirin. It can be a rare complication of diabetes.

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4
Q

How can the kidney prevent metabolic acidosis?

A

The kidneys play an important role in preventing metabolic acidosis by regulating the pH of the blood. When the blood becomes too acidic, the kidneys work to restore the balance by excreting hydrogen ions in the urine and reabsorbing bicarbonate ions from the urine. This process is called renal tubular acidosis. The kidneys can also produce new bicarbonate ions to increase the blood pH. These mechanisms help to prevent the blood from becoming too acidic, which can cause serious health problems.

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5
Q

Describe the kidney

A

The kidneys are bean-shaped organs that lie ret- roperitoneally on the posterior abdominal wall, one on each side of the vertebral column at the level of T12–L1 vertebrae. The right kidney lies slightly inferior to the left kidney.
11-15cm

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6
Q

What are the excretory functions of the kidney?

A

Drugs
Metabolites
Toxins

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7
Q

What are the homeostatic functions of the kidney?

A

Maintains water balance
Maintains electrolyte balance
Maintains acid base balance

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8
Q

What are the endocrine (hormone) secreting functions of the kidney?

A
  • Renin by juxtaglomerular cells (JG)
  • Erythropoietin hormone by endothelial cells of pertubular cortex
  • Prostaglandins
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9
Q

Function of Erythropoetin

A

Erythropoietin is a hormone that your kidneys naturally make to stimulate the production of red blood cells

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10
Q

What are the endocrine (hormone) metabolic functions of the kidney?

A

The kidney converts vitamin D3 -› active 1,25-dihydroxycholecalciferol by
alpha one hydroxylase enzyme in cells of PCT under effect of PTH.

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11
Q

What happens to the nephron after age 40?

A

It begins to degenerate and 10% of the kidney degenerates
The nephrons are non-regenerative

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12
Q

Why are nephrons non-regenerative?

A

They are made up of already differentiated cells. They don’t undergo meiotic division just like cardiomyocytes

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13
Q

Each kidney contains how many nephrons?

A

1.2 million

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14
Q

The 2 main parts of the kidney

A

Renal corpuscle: where blood plasma is filtered
Long renal tubule: process the filtrate into urine

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15
Q

Describe the renal tubule and its major regions

A

It leads away from the glomerular capsule and ends at the tip of the medullary pyramid

  1. PCT
  2. Loof of Henle
  3. DCT
  4. Collecting Duct
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16
Q

Describe the PCT

A

Arises frm the glomerular capsule
Longest and moist coiled region
Simple cuboidal epithelium with microvilli, which helps with the great deal of absorption that takes place

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17
Q

Describe the Loop of Henle

A

Parts:
descending limb: passes from cortex to medulla
ascending limb: 180-degree turn and return to the cortex

It is divided into:
- thick segment: simple cuboidal epithelial cells are highly active in the transport of salts (high metabolic activity & mitochondria)

  • thin segment: simple squamous epithelium, low metabolic rate but very permeable to water
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18
Q

Describe the DCT

A

simple cuboidal epithelium but with no microvilli

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19
Q

Describe the CD

A

Passes through the medulla
Collecting ducts merge to form a papillary duct which will drain into the minor calyx

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20
Q

Describe the flow of glomerular filtrate

A
  1. glomerular capsule
  2. PCT
  3. Loop of Henle
  4. DCT
  5. CD
  6. Papillary duct
  7. minor calyx
  8. major calyx
  9. renal pelvis
  10. ureter
  11. urinary bladder
  12. urethra
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21
Q

What are the 2 types of nephrons? Compare them

A
  1. Cortical nephrons or superficial nephrons: Nephrons having the corpuscles in the outer cortex of the kidney near the periphery. In human kidneys, 85% of nephrons are cortical nephrons.
    A short loop of Henle
    Blood supply to tubules: peritubular capillaries
    Function: formation of urine
  2. Juxtamedullary nephrons: Nephrons having the corpuscles in the inner cortex near the medulla or corticomedullary junction.
    a long loop of Henle
    It makes up 15% of nephrons
    Blood supply to tubules: vasa recta
    Function: concentration and formation of urine
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22
Q

The kidney account for____% of body weight and receives ___% of cardiac output

A

0.4%
25%

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23
Q

What is cardiac output?

A

The volume of blood pumped out of the heart per minute
On average 5L

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24
Q

What is the stroke volume?

A

The volume of blood pumped out of the heart
Average is 70ml per beat

25
Q

The renal artery originates from__________

A

the abdominal aorta

26
Q

Describe renal circulation

A

The renal artery arises directly from the abdominal aorta and enters the kidney throughthe hilum, the renal artery and divides into many segmental arteries.

Segmental artery subdivides into interlobar arteries

The interlobar artery passes in between the medullary pyramids. At the base of the pyramid, it turns and runs parallel to the base of the pyramid forming an arcuate artery

Each arcuate artery gives rise to interlobular arteries.

Interlobular arteries run through the renal cortex perpendicular to the arcuate artery. From each interlobular
artery, numerous afferent arterioles arise.

An afferent arteriole enters the Bowman capsule and forms a glomerular capillary tuft. After entering the Bowman capsule, the afferent arteriole divides into 4 or 5 large capillaries

Glomerular Capillaries
Each large capillary divides into small glomerular capillaries, which form the loops. And, the capillary loops unite to form the efferent arteriole, which leaves
the Bowman capsule.

Efferent Arteriole
Efferent arterioles form a second capillary network called peritubular capillaries, which surround the tubular
portions of the nephrons. Thus, the renal circulation forms a portal system by the presence of two sets of
capillaries namely glomerular capillaries and peritubular capillaries.

Peritubular Capillaries and Vasa Recta
Peritubular capillaries are found around the tubular portion of cortical nephrons only. The tubular portion of
juxtamedullary nephrons is supplied by some specialized capillaries called vasa recta. These capillaries are
straight blood vessels hence the name vasa recta. Vasa recta arise directly from the efferent arteriole of the
juxtamedullary nephrons and run parallel to the renal tubule into the medulla and ascend towards the
cortex

27
Q

Show the flow of renal circulation

A
  1. Renal arteries
  2. Segmental arteries
  3. interlobar
  4. arcuate
  5. interlobular
  6. afferent arteriole
  7. Glomerular capillaries
  8. pertubular capiilaries and vasa recta
28
Q

The kidney utilizes______ % of the total O2 consumption of the body

A

8%

29
Q

Why is high blood flow required in the kidney?

A

àllows a higher rate of glomerular filtration

30
Q

Describe the physiology of the JG apparatus?

A

JG apparatus is important in the regulation of renal blood flow and glomerular filtration It is responsible for autoregulation of the kidney which is why the kidney is independent of the PNS.
It is made up of macula densa cells, JG cells and extraglomerular mesangial cells.

31
Q

Macula densa cells

A

Macula densa is where the DCT touches the Bowman’s capsule. It is situated between afferent and efferent arterioles of the same nephron. It is very close to the afferent arteriole.Macula densa is formed by tightly packed cuboidal epithelial cells.

32
Q

Juxtaglomerular cells/ granular cells

A

Juxtaglomerular cells are specialized smooth muscle cells situated in the wall of afferent arteriole just before it
enters the Bowman capsule.
They produce, store and release renin

33
Q

Extraglomerular mesangial cells/ Lacis cells/ Agranular cells

A

Glomerular mesangial cells support the glomerular capillary loops by surrounding the capillaries in the form
of a cellular network.These cells play an important role in regulating the glomerular filtration by their contractile property

34
Q

The Kidney receives 25% of cardiac output which is the largest in all the reginal organs, briefly discuss the unique features of the kidney that is responsible for this physiological demand

A

Kidney takes blood not just for tissue perfusion but also for ultrafiltration
Explain the concept of a physiological shunt

35
Q

The kidney is a low concentration O2 compound compared T/F

A

True because it requires a low amount of O2 to survive

35
Q

What can pass through a filtration barrier

A

water
electrolytes
glucose
fatty acids
amino acids
nitrogenous waste
vitamins

35
Q

3 Stages of urine formation

A
  1. Glomerular filtration
  2. Tubular reabsorption
  3. Tubular secretion
35
Q

Describe the innervation of the kidney

A

nerves arise from the superior mesenteric ganglion and enter the hikum if the kidney

They follow the renal artery and innervate the afferent and efferent arterioles

Contain sympathetic fibers taht regulate blood flow into and out of each nephron: thus control the rate of filtration and urine formation

If BP falla, they stimulate the secretiob of renin (enzyme) that activates hormonal mechanism for restoring BP

35
Q

What are the 3 barriers of the filtration barrier?

A
  1. Fenestrated endothelium of the capillary
  2. Basement membrane
  3. Filtration slits
36
Q

Describe filtration slits

A

produces by the podocyte cells, produce negative charged filtration slits, allow partivles <3nm to pass

36
Q

Describe the fenestrated endothelium of the capillary

A

Honeycomb capillaries with large holes (70-90nm)
Highly permeable but small enough to exclude blood cells from the filtrate

36
Q

Describe the basement membrane

A

Proteoglycan gel produce a negative charge, smaller fenestration, smaller fenestrations excludes any particle > 8nm.

Some smaller molecules are held up by negative electrical charge, produced by the proteoglycan gel

37
Q

Damage to filtration barriers can cause

A

Proteinuria (albuminuria) and hematuria caused by trauma, kidney infection and strenous excercise.

37
Q

Types of filtration pressure

A

Hydrostatic Pressure is the physical force exerted against a surface, (capillary), by a liquid. BP is one of the examples of hydrostatic pressure.

Colloid osmotic pressure (COP) - the portion of osmotic pressue due to protein. Blood has a COP of about 28mm Hg mainly due to albumin

37
Q

What does glomerular filtration involve?

A

High blood hydrostatic pressure (BHP)(60mmHg) due to the larger afferent arteriole compared to efferent

Hydrostatic pressure in the capsular space is about 18mmHg, resulting in high rate of filtration, and constant accumulation of fluid in capsular space

COP = 28-32nm

38
Q

What is GFR?

A

Glomerular filtration refers to the process of ultrafiltration of plasma from the glomerular capillaries into the Bowman’s capsule

39
Q

What are the factors that affect the GFR?

A
  1. Filtration coefficient
    - Permeability increased in hypoxia and toxicity
    -Contraction and relaxation of mesangial cells
  2. Hydrostatic pressure in Bowman’s capsule decreases the GFR in acute obstruction of the urinary tract
  3. Blood hydrostatic pressure
    (GFR is constant from 80mmHg t 200mmHg) this decreases in acute renal failure, leading to a decline in GFR
  4. Renal blood flow and afferent and efferent arteriole resistance
  5. Blood oncotic pressure (Hyperproteinemia leads to a decrease in GFR)
  6. Sympathetic (little important) leads to a decrease in GFR
  7. State of glomerular membrane
40
Q

Briefly discuss the myogenic theory

A

According to this theory, the vascular
smooth muscle (VSM) responds to wall tension. An increase in the arterial pressure initially stretches the smooth muscle fibres; in response to which the VSM contracts and increases the resistance compensates for the higher arterial pressure, returning the blood flow to control levels.

41
Q

Homeostatic mechanisms for GFR

A
  1. Renal autoregulation
  2. Sympathetic control
  3. Hormonal control (renin and angiotensin)
42
Q

Renal autoregualtion

A

The ability of nephrons to adjust their own blood flow and GFR without external (nervous, hormonal) control

42
Q

Mechanisms of autoregulation

A
  1. Myogenic mechanism
  2. Tubuloglomerular feedback
43
Q

Examples of vasoconstrictors

A

norepinephrine and epinephrine
angiotensin II
thromboxane A2 (from macula densa)
prostacycline
prostaglandin

43
Q

If afferent arteriole constrict it leads to

A

decrease in GFR

43
Q

If afferent arteriole dilate it leads to

A

increase in GFR

44
Q

If efferent arteriole dilate it leads to

A

decrease in GFR

45
Q

processing glomerular filtrate to produce urine includes

A

Tubular reabsorption and tubular secretion

46
Q

What is tubular reabsorption?

A

A process that reclaims useful materials from the glomerular filtrate such as water, glucose, urea, uric acid, amino acid, vitamins, minerals, creatine and creatinine

47
Q

Factors facilitating tubular reabsorption
Explain each

A

Nature of substance
Nature of absorptive SA
Route of absorption
Presence of transport mechanisms
Influence of hormone

48
Q
A

Physiology 300L Renal (2 decks)

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