introduction to kidney & renal function Flashcards
what are the 2 functions of the urinary system?
1) excretion
2) elimination
what is excretion?
the removal of organic waste products from body fluids
what is elimination?
the discharge of waste products into the environment
what are the essential renal functions?
- excretion
- homeostasis
- regulation
what is excreted from the renal system?
endogenous waste products, drugs and their metabolites
what is regulated by homeostasis in the renal system?
- water and electrolyte balance
- acid-base balance
what is produced in the renal system by an essential function?
hormones (erythropoietin, renin…)
what happens in renal dysfunction (failure)?
- reduction in renal excretory function (uraemia, azotaemia)
- reduction in renal excretory function (drug toxicity)
- inability to maintain salt and water balance and acid-base balance (metabolic consequences)
- compromised hormone function (anaemia, hypertension…)
what type of renal failure accounts for 10% of renal failure?
acute kidney injury (AKI) - rapid
what type of renal failure accounts for 90% of renal failure?
chronic kidney disease (CKD) - months or years to develop
where are the kidneys located?
on the posterior wall of the abdomen behind the peritoneum on either side of the vertebral kidney
roughly how much does an adult human kidney weigh?
120-170g
what is the average size of a kidney?
11cm long, 6cm wide, 3cm thick
where is the kidney joined?
at the medial side to the renal artery and vein, nerves and ureter
what are the 2 major layers of the kidney?
- cortex (outer layer)
- medulla (middle layer)
how many nephrons make up the cortex?
approximately 1.25 million
what is a nephron?
the functional unit of the kidney responsible for urine formation and composition
what is the structure of the medulla like?
pyramids that drain into the pelvis which drains into the ureters
what are the 5 distinct sections of the nephron?
1) glomerulus (renal corpuscle)
2) proximal tubule (PT)
3) loop of Henle (LOH)
4) distal tubule (DT)
5) collecting duct (CD)
what are the 2 types of nephron?
- cortical nephrons
- juxtamedullary nephrons
how many of the nephrons in the kidney are cortical and juxtamedullary?
- cortical = 70-80%
- juxtamedullary = 20-30%
where are the cortical nephrons found?
located in the cortex
what is the loop of Henle like in cortical nephrons?
short into the medulla
where are the juxtamedullary nephrons found?
situated closer to the medulla
what is the loop of Henle like in juxtamedullary nephrons?
loop of Henle extends deep into the renal pyramids
how much of the cardiac output does the kidney receive?
20%
what are the nerves supplying the kidney?
- sympathetic postganglionic fibres from sympathetic chain and fibres from coeliac gangion
- parasympathetic efferent supply from vagus nerve: ganglion in hilum
what blood vessels surround the cortical nephron’s loop of Henle?
peritubular capillaries
what blood vessels surround the juxtamedullary’s loop of Henle?
vasa recta
what is the function of the sympathetic postgangionic supply of the kidney?
- supplies arteries, afferent and efferent articles and granular cells
- reduces blood supply to the kidney during stress
what is the function of the parasympathetic efferent supply of the kidney?
- may control tone of efferent arterioles
- may modify glomerular filtrate rate (GFR) and renal blood flow (RBF)
what are the 3 major functions of the nephron?
1) filtration of blood to produce filtrate
2) reabsorption of water, ions and organic nutrients from filtrate
3) secretion of waste products into tubular fluid
what is transcellular transport?
movement through cells
what is paracellular transport?
movement between cells
where does filtration occur?
at the glomerulus
what small molecules are filtered during filtration?
- electrolytes
- amino acids
- glucose
- metabolic waste
- some drugs, metabolites
what cells and large molecules remain in the blood during filtration?
- red blood cells
- lipids
- proteins
- most drugs, metabolites
what is tubular reabsorption and its key stages?
- more than 99% of filtered water, electrolytes and nutrients are reabsorbed back into the blood
- some solutes are reabsorbed down concentration and/or electrochemical gradients
- other molecules can undergo co-transport
- water follows passively along the osmotic gradient created by solute reuptake via aquaporins
- reabsorption of solutes requires energy in the form of ATP which drives Na+ reabsorption via the Na+/K+/ATPase transporter
what is tubular secretion and its key stages?
- some endogenous substances and drugs cannot be filtered at the glomerulus which may be due to their size or due to protein binding
- specialised pumps in the PT can transport compounds from the plasma into the nephron for excretion
- uses 2 pumps
what are the 2 pumps in tubular secretion?
1) for organic acids or drugs
2) for organic bases or drugs
