Physiology Flashcards
What are the three roles of the kidneys
Maintain balance of salt, water and pH
Endocrine function - secreting hormones
Excrete products
What is the renal blood flow
Cardiac output
Renal blood flow
Urine flow
Cardiac output approx. 5 L/min
Renal blood flow approx. 1L/min
Urine flow approx. 1 mL/min
What is the order of renal blood supply
Renal artery
Interlobar artery
Arcuate artery
Interlobar artery
Afferent arteriole
(Nephron) - glomerular capillary then peritubular capillary
What are the two capillary beds in the nephron
Glomerular capillary
Peritubular capillary
What does the passage of fluid from the blood into Bowman’s space form
Filtrate
What is the approx surface area involved in glomerular filtration
1m2
What is the distal part of the nephron responsible for
Secretion and reabsorption
What are the five determinants which effecting the movement across the filtration barrier
- Pressure
- Size of the molecule
- Charge of the molecule
- Rate of blood flow
- Binding to plasma proteins e.g. calcium, hormones such as thyroxine
What can freely pass the filtration barrier
Small molecules and ions up to 10kDa
Name examples of ions which are up to 10kDa
Glucose
Uric acid
Potassium
Creatine
What is restricted crossing the filtration barrier
Larger molecules
What cannot cross the filtration barrier
Negatively charged anions
Due to the fixed negative charge in the glomerular basement membrane repels these
What are the key features of Albumin
66kDa - molecular weight
Negatively charged
What is the protein called in urine which is produced by tubule
Tamm Horsfall protein
What is filtered fluid free from
Proteins
What is the renal blood flow ml/min
1250
What is the renal plasma flow ml/min
700ml/min
What is the glomerular filtration rate ml/min
120ml/min
What is the urine flow rate ml/min
1ml/min
What is the bodies normal pH (hydrogen ion) range
7.35-7.45
What is the bodies normal pH (hydrogen ion) range
7.35-7.45
What is the minimum urine hydrogen ion concentration (pH)
4.5
Define Base
Accepts hydrogen ions
Define acid
Donates hydrogen ions
Carbohydrates + fats =
Carbonic acid
Number the buffers involved in dietary acid load
Plasma protein
Haemoglobin
Extracellular bicarbonate
Intracellular carbonate
Phosphate
What is the name of the protein which is present in urine produced by the tubule
Tamm Horsfall
What is the renal corpuscle made up of
Glomerulus (tuft capillaries) + Bowman’s capsule
What goes is the blood flowing into the glomerulus
Afferent arteriole
What is the blood flowing out of the glomerulus
Efferent arteriole
What does the glomerulus contain
Endothelial layer
Glomerular basement membrane
What does the endothelial layer contain
Fenestrated capillaries
What is the role of fenestrated capillaries
Cannot filter formed elements e.g. blood cells
Can filter elements less than 100nm in diameter
What are the layer of the glomerular basement membrane and its role
Lamina rara interna (heparin sulphate)
Lamina Densa (type 4 collagen with laminas)
Lamina rare externa (heparin sulphate)
What is the role of the glomerular basement membrane
Negatively charged on both sides
Cannot pass negative molecules e.g. plasma proteins
Easily pass positively charged molecules e.g. sodium
Can pass (but not as well as positively charged) negatively charged molecules e.g. chloride
What is the Bowman’s capsule made up of
Parietal layer
Visceral layer (podocytes)
What is the role of podocytes
Slit diaphragm in-between made of nephrin
Only allows less than 10nm through
What can pass through the renal corpusal
Charged ions less than 10nm
What can pass through the endothelial layer
Most substances
50-100nm
What cannot pass through the glomerular basement membrane
Negative molecules repelled
What can pass through the visceral layer of the renal corpuscle
Less than 10nm
What happens in the Renal corpuscle if a macromolecule e.g. plasma protein was to get stuck in the slit diaphragm
Phagocytosed by mesangial cells
What are the role of mesangial cells
Phagocytosis
Control the amount of blood flow
Gap junctions with juxtaglomerular cells
Define glomerular filtration rate
Filtration rate per unit of time (minutes)
What percentage of blood that passes into the renal corpuscle will be filtered
20%
What happens to hydrostatic pressure along the length of the capillary
Constant along the length
What happens to osmotic pressure along the length of the capillary
Rises along the length
What affects GFR
Net filtration rate
Surface area
Permeability of glomerulus