Kidney Histology Flashcards
what is the function of the urinary system
- Regulation of blood composition, pressure and volume
- EPO – produced red blood cells
- Electrolyte and acid base balance
- RAAS – pressure and volume of blood
what are the components of the urinary system
- Kidneys
1. Renal parenchyma (nephorns)
2. Passageways for urine calyx – renal pelvis - Ureter
- bladder – reservoir and pump
- Urethra – removes urine
what is the nephron
a funnel shaped epithelial structure where a blood filtrate is processed ultimately leaving urine
what makes up the nephron
= Bowman’s capsule and renal tubule these make up the nephron
describe the structure of the bowman capsule
- it has a parietal wall - this is made out of simple squamous epithelium
- has a visceral wall - this is close to the glomerular and contains podcytes
what cells support the bowman capsule
supported by mesangial cells and their extracellular matrix- mesangium
what are the two poles of the bowman capsule
vascular pole
urinary pole
describe the vascular pole and the urinary pole of the bowman capsule
vascular pole where the site of afferent and efferent arterioles enter
urinary pole- opposite side where the proximal convoluted tubule begins
what makes up the renal corpuscle
• Bowman’s capsule with its glomerulus (tuft of capillary loops) supported by mesangial cells and their extracellular matrix- mesangium
- globular capillaries
what is the function of the renal corpuscle
- ultra-filtration of blood
describe how substances are inhibited from crossing the bowman capsule
- too large - podocytes have spaces between there foot processes, 60,000
- podocytes have a negative charge therefore if the molecule such as protein is negatively charged then it is inhibited from getting through -
in what circumstance can albumin go through the kidney
if it is albumin, if there is damaged to the glomerulus it becomes leaky and the podocyte charges are missing then albumin can filter into the lumen and is lost therefore the patient has oedema as not enough reabsorption into the blood back from the interstitial tissue
what is the function of the mesagnial cells
- produce the mesnaignal matrix
- have immuoreactivity
- cytokines are released by the mesaingal cells
- angiotensin II bindings to the receptors and stimulates mesangial cell contraction
- interacts with the juxtaglomerular system
name the three things that the globular filtration barrier is made out of
- Fenestrated capillary endothelium
- Basement membrane
- Podocyte layer of Bowman’s capsule – end feet that stick down on the basement membrane, between the podocyte process they have membranes and proteins that can regulate and charge
what is the function of the proximal convoluted tubule
reabsorption
- this is facilitated by sodium potassium ATPase in the basolateral membrane - produces a concentration gradient
what does the proximal convoluted tubule reabsorb
- 70-80% of the water, Na+ and Cl-
- ~100% of amino acids and glucose
- some bicarbonate reabsorbed/ H+ secreted
- larger proteins, carbohydrates - endocytosis
what is the appearance of the proximal collated tubule
- microvillus brush border; - increases surface area
- endocytotic vesicles and lysosomes;
- basal and lateral interdigitations - increases surface area
- (ion transport machinery)
what is the function of the loop of Henle
create and maintain the high ionic concentration of the medulla
what epithelium is in the thick ascending limb
simple cuboidal
what does the thick ascending limb do
- actively transports Na+(with Cl-) out of tubule without water (impermeable)
- results in hypotonic urine and hypertonic concentration gradient of NaCl in medulla
- urine become hypotonic as there is not much sodium present in it due to the hypertonic concentration gradient of NaCl in the medulla
what is the function of the distal convoluted tubule
- water balance- tubules reabsorb water in the presence of antidiuretic hormone (ADH)
- electrolyte and acid-base balance- Na+ reabsorption coupled to K+ or H+ secretion under control of aldosterone
what epithelium is int he collecting ducts
simple columnar epithelium
what epithelium is the distal convoluted tubule
simple cuboidal epithelium
what is the appearance of the distal convoluted tubule
- simple cuboidal epithelium;
- few microvilli or endocytotic vesicles;
- basal and lateral interdigitations reflecting ion transport requirements
the proximal convoluted tubule is much less…
defined that the distal convoluted tubule
what else does the distal convoluted tubule contain
macula densa
what does the juntaglomerular apparatus function
- it regulates blood pressure and volume
what is the juxtaglomerular apparatus made out of and what do they do
- Juxtaglomerular cells - afferent arteriole sense decreases in blood pressure and secrete renin (renin- angiotensin- aldosterone system) – renin turns angiotensinogen to angiotensin, also controlled by sympathetic drive
- Macula densa - sense decreased Na+ content of distal tubule
- Extraglomerular mesangial cells or lacis cells - support/ info transfer
what is the function of the collecting duct
- final concentration of urine (ADH sensitive);
- electrolyte and acid base balance (aldosterone sensitive)
urea diffusion helps maintain high solute concentration of the medulla
what helps maintain a high solute concentration of the medulla
urea diffusion helps maintain high solute concentration of the medulla
describe the histology of the collecting duct
simple cuboidal to columnar epithelium;
distinct lateral membranes (few interdigitations)
what are the two types of cells in the collecting duct
principal cell
intercalated cell
describe the role of the principle cell
- has absonant mitochondria
- they reabsorb sodium and water and secrete potassium
- contains polcysitin portions 1 and 2
- responsible for autosomal domains polyscitc kidney disease
what is the role of the intercalated cell
- abdumancce in mitochondria
- they either secrete hydrogen ions or bicarbonate
- important in acid and base balance
name the urinary passageways
- Calyces
- Renal pelvis
- Ureter
- Bladder
- Urethra
what epithelium lines the urinary passageways
Mucosa– transitional epithelium
• ‘plaques’= membrane folds- allow distension
2. tight junctions between cells/ thick impervious cell membranes- ‘barrier to urine’
what is the makeup of the transitional epithelium
lamin propria but no muscalris mucoseae
describe the 3 layers of muscular in the urinary passageway
Muscularis: 2-3 layers of smooth muscle 1st innermost ‘longitudinal’ (loose spiral) 2nd circular (tight spiral) 3rd longitudinal (loose spiral) begins at lower ureter
what is the adventitia
Outer layer of loose connective tissue carrying larger blood vessels and nerves
describe the bladder anatomy
- Distensible reservoir and muscular pump
- Ureters enter at an acute angle in posterolateral wall- filling closes the lumen (muscular and positional effects) Prevents back flow
- Internal sphincter formed by middle circular smooth muscle layer at ‘neck’ at beginning of urethra
- Micturition is controlled by parasympathetic nervous system input
