Kidney Function 1 Flashcards
Functions of the kidney
- Control of the body fluid- REGULATION
Volume Regulation- therefore regulate the interstitial flood and therefore intracellular composition
Osmoregulation
pH regulation by secreting and excreting H+ and reabsorbing HCO3-
- Excretion of Metabolites Urea- protein catabolism Uric Acid- nucleic acid breakdown Creatine- muscle creatine breakdown End products of Hb Breakdown Metabolites of hormones Foreign chemicals eg. drugs
- EndocrineHormones that act on the kidney:
ADH, aldosterone, natriuretic peptides, parathyroid hormone, fibroblast growth factor 23Hormones produced by the kidney:
Rennin, vitamin D, erthpoietin, prostaglandins
Gross structure of the kidney
Kidneys positioned either side of the vertebral column between T12- L3. Back of the abdominal cavity, outside of the peritoneum
Concave surface-face each other
Convex surface faces the abdominal wall
Ureter- originates from the the concave surface
Moves urine from the kidney to the bladder by peristalsis.
Urine is stored int he bladder until it is expelled
Renal Corpuscle- Structure
Initial filtering mechanism of the nephron
Consists of glomerulus and bowman’s capsule
Golumerulus consists of a compact loops of interpolated capillary loops
Filtered through the filtering interface enters the bowman’s capsule
Filtering interface
Fenestrated capillarity endothelium- LEAKY
Basement membrane- fixed polyanions-
i) lamina densa
ii) lamina interera
iii) lamina externa
Podacytes- tubular epithelium- speciliased
central body and very long foot processes- these interdigitate and form filtration slits for which fluid can move.
Tubule
Proximal convuluted tubule
proximal straight tubule
descending thin limb of Henle’s loop
Ascending thin limb of Henle’s loop
Ascending thick limb of Henle’s loop
Distal Convoluted loop
Cortical collecting duct
Medullary collecting duct
nephron types-
cortical- outer 2/3 of cortex- short loop of Henle
Juxtamedullary- inner 1/3 cortex- long loop of Henle- concentrated urine- more water conserved
Juxtaglomerular apparatus
Juxtaglomerular cells- secrete renin
Macula densa in the wall of the ascending loop of Henle
Mesangial cells also present
The nephrons blood supply
2 sets of arterioles- afferent and efferent
2sets of capillary beds in series- glomerulus and peritubular- near the tubules forming vasa recta
Basic Renal Processes
Glomerular Filtration- ultrafiltration- the movement of fluid and solutes. GLOMERULR CAPILLARIES - BOWMANS’S SPACE
Tubular Secretion- the secretion of solutes from the peritubular capillaries to the tubules
Tubular reabsorbtion- the movement of materials from the filtrate in the tubules into peritubular capillaries
Metabolism- glutamine
Amount excreted in urine=
Amount filtered + Amount secreted - Amount reabsorbed
1) PAH
filtered and secreted
NOT reabsorbed
2) Water and electrolytes
Filtered
Some reabsorbed
3) glucose
filtered
Completely reabsorbed
What gets through the glomerular filtration barrier
Depends on size, shape and charge
Most plasma constituents are freely filtered except proteins
[Filtered] / [Plasma] =1
This is called free passage
Anionic molecules will have a ratio less than one due to repulsion due to fixed polyanions
Composition of ultra filtrate
it is similar to that plasma except for the fact that there are differences in certain molecules- proteins
Infection + Damage to the glomerulus + High BP
PROTEIN IN URINE - proteinuria
HB IN URINE -haemoglobinuria
RBC IN URINE - haematuria
GFR
Volume of fluid filtered from the glomerulus per minute
What is GFR dependant on?
Starling forces - hydrostatic forces vs Osmotic forces
Surface area of filtration interface
Hydraulic permeability of capillaries
regulated by neural and hormonal input
Changing pressure gradient in relation to GFR
Constricting AA - decreasing GFR
Constricting EA - increasing GFR
Changing SA in relation to GFR
Mesangial cells- contain actin and innervated by sympathetic NS
Symapathetic NS activated due to the Low BP
The SA of the interface decreases due to actin contracting
Decrease in glomerular filtrate rate
Reabsorption
Occurs in the proximal tubule
Na+ coupled transporter- glucose amino acids, phosphate
Passive reabsorption - urea, chloride, potassium and chloride
Secretion in PCT
Organic acids- anions:
Endogenous molecules- bile salts, fatty acids, prostaglandins
Drugs
Diagnostic agents- PAH
Organic bases- cations
Endogenous molecules- creatine, dopamine, choline, guandine, histamine
Drugs- atropine, cimetidine, morphine
How are organic anions secreted in PCT
OA- enters the cell in exchange for DC-
DC-accumialtes in cells by metabolism and Na+ coupled co transport
OA- enters tubule lumen via ATP dependant transporters
How are organic cations secreted in PCT
Enter cell via facilitated organic cation transporters
Enter tubule lumen via multi drug and toxin extrusion proteins anti porter in exchange for H+
