T3 L2 Intro to kidney & renal function Flashcards
What are the 2 functions of the urinary system?
Excretion - removal of organic waste products from body fluids
Elimination - discharge of waste products in the environment
What are the 3 essential renal functions?
Excretion of endogenous waste products, drugs & their metabolites
Homeostasis - water & electrolyte balance, acid-base balance
Regulation - production of hormones such as erythropoietin and renin
What is renal dysfunction?
Reduction in renal excretory function
Inability to maintain salt & water balance & acid-base balance
Compromised hormone function - anaemia, hypertension
What happens if renal failure is severe & untreated?
Can lead to death
What happens if renal failure is rapid?
Acute kidney injury
10% of renal failure
If you remove the problem the kidneys tend to recover
What happens if renal failure develops over months/years?
Chronic kidney disease
90% of renal failure
Where are the kidneys situated?
Posterior wall of abdomen
Behind peritoneum
On either side of vertebral column
Joined at medial side to renal artery, vein, nerves & ureter
What is the size of a kidney?
120-170g in adults
11cm x 6cm x 3cm
What is the cortex?
Outer layer
Composed of around 1.25million nephrons
What is the medulla?
Inner layer
Has pyramids which drain into pelvis which drains to ureter
What is the nephron?
Basic functional unit of the kidney responsible for urine formation & composition
How many nephrons per kidney?
1.25million
Number & renal function declines with age
What are the 5 distinct sections of the nephron?
Glomerulus Proximal tubule Loop of Henle Distal tubule Collecting duct
What are the 2 types of nephron?
Cortical nephron
Juxtamedullary nephron
Describe the cortical nephron
70-80% of nephrons in the human kidney
Located in cortex
Short look of Henle into medulla
Describe the juxtamedullary nephron
20-30% of all nephrons in human kidneys
Situated closer to medulla
Loop of Henle extends deep into renal pyamids
What are the functions of the nephron?
Filtration of blood to produce a filtrate
Reabsorption of water, ions & organic nutrients from filtrate
Secretion of waste products into tubular fluid
Transcellular transport
Paracellular transport
What is transcellular transport?
Movement through cells
What is paracellular transport?
Movement between cells
How are the cells in the cortex adapted to provide energy for reabsorption & filtration?
Full of mitochondria
Describe the pathway of blood flow from the renal artery to the nephrons
Renal artery –> segmental arteries –> interlobar arteries –> accurate arteries –> interlobular arteries –> afferent arterioles –> nephrons
Describe the pathway of blood flow from the nephron to the renal vein
Nephrons –> venules –> interlobular veins –> arcurate veins –> interlobar veins –> renal vein
What do the sympathetic postganglionic fibres from the sympathetic chain & fibres from coeliac ganglion supply?
The arteries
Afferent & efferent arterioles
Granular cells
Reduces blood supply to kidney during stress
What does the parasympathetic supply from the vagus nerve supply?
May control tone of efferent arteries
May modify glomerular filtration rate & renal blood flow
What is glomerular filtration?
Initial step in urine formation
All small molecules are filtered
What small molecules are filtered in glomerular filtration?
Electrolytes Amino acids Glucose Metabolic waste Some drugs, metabolites
What molecules remain in the blood after glomerular filtration?
Red blood cells
Lipids
Proteins
Most drugs, metabolites
Describe tubular reabsorption
More than 99% of filtered water, electrolytes & nutrients are reabsorbed into the blood
Some solutes such as Na+ are reabsorbed down concentration and/or electrochemical gradient
Other molecules can undergo co-transport
Water follows passively along osmotic gradient created by solute reuptake via aquaporins
Reabsorption of solutes requires energy in form of ATP
Describe tubular secretion
Some endogenous substances & drugs can’t be filtered a glomerulus
Specialised pumps in proximal tubule can transport compounds from plasma into nephron for excretin
What are the 2 kinds of pumps used in tubular secretion?
Organic acids or drugs - uric acid, diuretics, antibiotics
Organic bases or drugs - creatinine, procainamide
