A. STRUCTURE AND FUNCTION OF KIDNEY Flashcards
what are the 2 main functions of the kidney
- excretion
- regulation
regulations of the kidney
- control of water and electrolyte (K+, Na+, Cl-) balance
- control of arterial blood pressure (through blood volume as increased blood volume = increased blood pressure)
- control of acid-base balance (H+, HCO3-) as kidney works with lungs to regulate fluid pH and kidney gets rid of excess ie - acid from metabolism
- endocrine: EPO, renin, 1,25-dihydroxyvitamin D3 (calcitriol), PGs
- glucose synthesis (gluconeogenesis) during prolonged fasting
what does the kidney excrete
- metabolic waste
urea (from amino acids)
creatinine (from creatine)
uric acid (from nucleic acid)
end products of haemoglobin breakdown (yellow)
hormone metabolites - foreign substances (drugs - metabolised or unmetabolised, pesticides, food additives)
what happens with kidney failure
disruption of homeostatic functions and we get severe abnormalities in body fluid volumes and composition
where do the kidneys sit
- paired bean-shaped organs
- lie in posterior wall of abdominal cavity and on either side of vertebral column
why is the right kidney lower than the left
due to liver positioning
size and weight of kidney
115-170g
11cm long by 6cm wide by 3cm thick
size of a clenched fist
what is the kidney surrounded by
tough protective fibrous renal capsule and visceral fat
(protects from mechanical trauma and shock)
what does the medial side of the kidney contain
a notch (helium) from which the renal artery, renal vein, nerves, pelvis and ureter pass through
what is the outer layer of kidney called
cortex
what is the inner layer of the kidney called
medulla
divided into multiple cone-shaped pyramids called nephrons (functional units of kidney)
what is the nephron
- functional unit of kidney
- 5 anatomical regions
how many nephrons is the kidney composed of
- 1 million
- we don’t make them
(age >40, natural loss of 10% per 10 years so by 70 we have 30% fewer functioning nephrons) - to see significant changes need 50% lost
what components does the nephron consist of
vascular (blood vessels) and tubular (nephron tube) components
blood supply to kidneys
blood flow to both kidneys is about 20-25% of total cardiac output (1.2L/min)
what are the 2 blood capillary beds
glomerular and peritubular capillaries
where do the afferent arterioles deliver blood to
glomerular capillaries (filtration occurs and this is the start of urine formation) and the glomerular capillaries rejoin to form efferent arterioles
what do the efferent arterioles do
- take unfiltered blood away from glomerulus
- they subdivide into peritubular capillaries and supply blood all around there kidney
difference in afferent and efferent arterioles
- efferent are smaller in diameter
- hence they receive blood with a relatively high hydrostatic pressure
what is the renal corpuscle made up of
Bowman’s capsule and the glomerulus
what are the glomerular capsules encapsulated in
Bowman’s capsule
collects filtered fluid from the capillaries
what is ultrafiltration
the start of urine formation as we are forcing a lot of fluid and solutes out of capillaries into Bowman’s space
where is the proximal convoluted tubule (PCT) and what is its main role
- continues from Bowman’s capsule
- lies entirely in cortex
- reabsorption back into blood
what cells are the PCT composed of
- single layer of cuboidal cells which interlock extensively, connected by tight junctions at their luminal surfaces
- microvilli present which increase the membrane SA
