The Kidneys: Structure and Function Flashcards
10 functions of the kidney?
- Water and salt balance
- Maintenance of:
• Plasma volume
• Plasma osmolarity - Acid-base balance
- Excretion of:
• Metabolic waste products, e.g:
• Exogenous foreign compounds, e.g: - Secretion of:
• Renin (control of ABP)
• Erythropoietin (RBC production) - Conversion of vitamin D into its active form (calcitriol), which allows Ca2+ absorption from the GI tract
Primary function of the kidney?
Regulation of the following factors of the body fluids:
• Volume
• Composition
• Osmolarity
Explain homeostasis and how this applies to water and ion balance
Balance concept of any substance (input = output), e.g:
• Water balance variable inc. thirst (input) and urinary loss (output)
• Na+, K+, H+, Ca+, Cl-, PO42-
2 constituents of the urinary system and their functions?
- Kidneys produce urine
- Structures that store and carry the urine from the kidneys to the outside for elimination
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Describe the divisions and structure of the kidney
- Renal cortex and medulla (consists of pyramids)
2. Renal pelvis continues into the ureter
What is the nephron?
Functional unit of the kidney with each being composed of ~1 million neprhons
Functional mechanisms of the nephron?
- Filtration
- Reabsorption
- Secretion
Label the regions of the nephron?
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2 types of nephron?
- Juxtamedullary (~20%)
2. Cortical (~80%)
Label the image of the nephron?
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Label the image of the Bowman’s capsule and glomerulus?
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Label the juxtaglomerular apparatus?
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What is urine?
Modified filtrate of the blood
Kidney components that allow production of urine?
- Filtration system
- Rich blood supply
- Mechanisms for urine modification:
• Reabsorption
• Secretion
Renal PROCESSES that allows production of urine?
- Glomerular filtration
- Tubular reabsorption
- Tubular secretion
Within the renal tubule, substance are added/removed as the urinary filtrate moves from the proximal to distal end
What happens to the plasma that enters the glomerulus?
20% is filtered
80% is not filtered and leaves via the efferent arteriole
Label the image of the glomerulus and the kidney tubule?
IMAGE
Equation for the rate of excretion?
Filtration (GF) + Secretion (TS) = Reabsorption (TR) + Excretion
OR
Rate of excretion = rate of filtration + rate of secretion + rate of reabsorption
How are movements of substances within the kidney described?
In terms of concentration x flow
Calculate:
• Rate of filtration of a substance?
Rate of filtration of X =
mass of X filtered into the Bowman’s capsule per unit time
For a freely filterable substance (X):
Rate of filtration of X = [X]plasma x GFR
GFR = glomerular filtration rate
Calculate:
• Rate of excretion of a substance?
Rate of excretion of X =
mass of X excreted per unit time
Rate of excretion of X = [X]urine x Vu
Vu = urine flow rate
Calculate:
• Rate of reabsorption of a substance?
If rate of filtration > rate of excretion, net reabsorption of the substance has occurred
Rate of reabsorption of X = rate of filtration of X - rate of excretion of X
Calculate:
• Rate of secretion of a substance?
If rate of filtrated < rate of excretion, net secretion of that substance has occured
Rate of secretion of X = rate of excretion of X - rate of filtration of X
How are the rates of filtration and excretion measured?
Relatively easy
How are the rates of reabsorption and secretion measured?
Reflect tubular modification of the filtrate, i.e: they are obtained as the DIFFERENCE between filtration and excretion
Calculate the typical renal chloride balance?
Cl- filtered
= [Cl-]plasma x GFR
= 110 mmol/L x 0.12 L/min
= 13.2 mmol/min
Cl- excreted
= [Cl-]urine x Vu
= 200 mmol/L x 0.001 L/min
= 0.2 mmol/min
Thus, rate of filtration is > rate of excretion and so net reabsorption of Cl- has occurred
Cl- reabsorbed
= 13.2 - 0.2
= 13 mmol/min
