SUGER Flashcards
How much of cardiac output do the kidneys receive and through which arteries
- about 1/5 of cardiac output
- through the renal arteries that arise directly from the abdominal aorta
What hormones do the kidney produce and what do these hormones do
- erythropoietin for control of red blood cell production
- renin for regulation of water and salt concentration
Describe the cortex and medulla of a kidney
- cortex is pale
- medulla is dark
- kidney contains 10 to 15 medullary pyramids whose apices point towards the hilum of the kidney
- cortex contains all of the glomeruli of the kidney and convoluted (coiled) parts of the proximal and distal tubules, first parts of collecting ducts
- medullary pyramids contains straight portions of the proximal and distal tubules, loops of Henle and distal part of collecting ducts
Describe the blood supply of the kidneys
-abdominal aorta
-renal artery (at L1)
-anterior and posterior division
-interlobar artery
-arcuate arteries (at the cortico-medullary junction)
-interlobular arteries (penetrate and divide cortex into lobules)
-afferent arterioles
-efferent arterioles (renal corpuscle)
-peritubular capillaries
descends into medulla
-vasa recta
-renal veins
-inferior vena cava
Where is blood filtered in the kidney and how
- in the glomerulus
- the glomerulus is made up of fenestrated capillaries ensheathed by podocytes
- the basement membrane between the endothelial cells of the capillaries and the podocytes of the epithelium constitutes the filtration barrier of the kidney
Where are the mesangial cells found
-between the coiled loops of the glomerular tuft
What do mesangial cells do
- they provide structural support for the kidney
- they have smooth muscle which contract and tighten capillaries to reduce the glomerular filtration rate
- produce matrix
- phagocytosis of glomerular breakdown products
Where are macula densa cells found
In the distal convuluted tubules
Where are the renin producing cells of the kidneys found
-the afferent arteriole
What do the macula densa cells do
- they sense low sodium and chloride levels
- stimulate the juxtaglomerular cells in the afferent arterioles of the kidney to release renin
Under how many Daltons do solutes need to be to pass into the urinary space of the kidney as primary filtrate
-50,000 Daltons
Describe the structure of the proximal tubules
- prominent brush border
- complex invaginations on their baso-lateral membrane
- cuboidal epithelium
- eosinophilic cytoplasm
What occurs in the proximal tubules
- re-absorption of filtrate
- sodium and glucose are actively transported
- protein and polypeptide uptake by endocytosis
- contain lysosome that break proteins down
List 2 important proteins that normally pass from the blood into primary filtrate but are recovered (reabsorbed) by the proximal tubule
- albumin
- haemoglobin
- almost any small negatively charged protein
What does the loop of henle consist of
- thick straight descending portion
- thin loop
- thick ascending portion
What does the thin ascending portion of the loop of Henle do
-retains water
-actively re-absorb chloride and sodium
So produces a dilute filtrate (urine) and a hypertonic interstitium (liquid in surroundings)
-vasa recta run alongside these tubules
What is the difference between the permeability of water in the thin descending and ascending loop of Henle and what does this cause
- the thin descending limb has low permeability to ions and urea but is highly permeable to water
- the thin ascending limb is not permeable to water but is permeable to ions
- this creates a concentration gradient within the renal medulla
Describe the distal tubules
- contains macula densa cells
- few short microvilli but no brush border
- cells often appear paler stained than those of proximal tubule
- deep invaginations on basal plasma membrane
- lots of mitochondria
- cuboidal epithelium
What do the distal tubules do
- under influence of aldosterone, sodium ions are reaborbed and potassium ions are excreted
- bicarbonate ions are re-absorbed and hydrogen ions excreted making urine acidic (through cellular carbonic anhydrase)
-acid/base balance and concentrations of urine
Which structures are known as medullary rays
The collecting ducts (and apparently the thin parts of the loop of Henle)
How does anti-duiretic hormone (ADH) affect the collecting duct cells
- increases permeability to water
- more aquaporins insert into its membrane and reabsorb water back
What is special about collecting ducts cells of the kidney
-dark intercalated cells with high concentrations of mitochondria
What structures make up the juxtaglomerular apparatus
-Apparantly just afferent arteriole and distal convoluted tubule but keep the ones below in mind
- afferent arteriole
- efferent arteriole
- macula densa
- lacis cells (specialised cell of the glomerular matrix)
Where in the body is angiotensin 2 produced
Renin secreted by modified muscle cells in the walls of the afferent arterioles of the glomerulus catalyses the conversion of angiotensinogen that is produced by the liver into angiotensin I. This is converted to angiotensin II mainly in the lungs. This goes on to stimulate the release of aldosterone by glomerular cells in the cortex of the suprarenal gland. This in turn promotes the reabsorption of sodium and water from the glomerular filtrate mainly by the cells of the distal tubule and collecting ducts.