gritti 17 Flashcards
the urinary system is composed of
-kidney
-ureter
-urinary bladder
-urethra
the kidney parenchyma is divided in 2 regions
outer renal cortex: that contains the glomeruli (filtration units)
inner medulla: tubules and ducts->appear striated because of that
corticomedullary junction
formed between the base of the renal pyramids and the cortical tissue
renal pyramids
the medulla is formed by 8-15 renal pyramids that are separated by cortical tissue (renal columns)
renal lobe
renal pyramid+ the tissue surrounding it
what’s the name of the tip of each renal pyramid?
renal papilla-> project into a minor calix that collect urine formed by one renal lobe
->the urine then goes into the ureter
the nephron, how is its structure?
-functional unit of the kidney
composed of
-renal corpuscle, made of the glomerulus and the Bownman’s capsule located entirely in the cortex
-proximal convoluted tubule: located entirely in the cortex
-loop of henle: made of ascending and descending parts located in the medulla
-distal convoluted tubule: ascending part that goes back in the cortex+a convoluted part entirely in the cortex
Bowman’s capsule
-double walled
-the outer layer’s epithelium is initially simple squamous, becomes simple cuboidal when it reaches the urinary pole (when the filtrate is about to enter to the proximal convoluted tubule)
-visceral layer made by podocytes with pedicels in direct contact (shared basement membrane) with endothelial cells of the glomerural capillaries (fenestrated capillaries)
mesangial cells
cells present in the interstitial tissue that fills the holes left by podocytes and give structural support
NB: cells of the connective tissue, not epithelial cells
what is the primary driving force in the formation of the filtrate?
blood pressure.
kidneys receive a lot of blood to be filtrated.
100-150L of initial filtrate, 99% is reabsorbed
1-1,5L of urine excreted per day
juxtaglomerural apparatus is made of
-macula densa: cells in the distal convoluted tubules (the part in contact with efferent and afferent arterioles) that are sensitive to NaCl conc in the filtrate (if too low, the kidneys are not filtering blood properly, the Glomerural filtration rate is too low)
-juxtaglomerural cells (granular cells) that are in the wall of afferent (and extend to also efferent) arteriole. these cells have renin in their granules. in response to macula densa cells alarm (too low NaCl in the filtrate) and low blood pressure (captured thanks to stretch receptors) renin is released
1. renin converts angiotensinogen in angiotensin I
2. angiotensin I is converted to angiotensin II by angiotensin converting enzyme
3. Angiotensin II is a vasoconstrictor and it also stimulates aldosterone secretion
aldosterone stimulates the re-absorption of water and sodium
renin-angiotensin-aldosterone system leads to vasoconstriction, increase of blood pressure and reabsorption of sodium
–>all of these things lead to the restore of GFR.
the spaces between the pedicels are covered by?
slit diaphragms which are polyanionic glycoproteins
how are the empty spaces between pedicels called?
filtration slits
glomerural filtration barrier, 3 components
-the capillary endothelium, which blocks blood cells and platelets
-the thick basement membrane, which filters organic anion and large proteins
-the filtration slits with slit diaphragms that filter organic anion and smaller proteins
what is the mesangium?
comprise of mesangial cells and their sorrounding matrix.
fills interstices between capillaries that lack podocytes
proximal convoluted tubule type of epithelium
simple tall cuboidal with microvilli
the epithelium almost fills the lumen
loop of Henle type of epithelium
thin descending simple squamous
thin ascending simple squamous
thick ascending simple cuboidal
thin segments->not many organelles, passive transport
thick segment–>many mitochondria, active transport for absorbance
distal convoluted tubule type of epithelium
simple cuboidal with few microvilli
less stained compared to proximal convoluted tubule
collecting tubules and collecting ducts
collecting tubules open into collecting ducts
collecting ducts end in ducts of Bellini or papillary ducts that merge the urine into the minor calix
-simple cuboidal (collecting tubules)
-simple cuboidal/columnar as the duct increase in size (collecting ducts)
where does the majority of what is filtered out from the blood gets reabsorbed? in which part of the tubular system?
proximal convoluted tubule
what is the final site of water resorption from the filtrate?
medullary collecting ducts
ADH and ANP
antidiuretic hormone
released by the posterior pituitary gland when the body is dehydrated
promote water reabsorption
-atrial natriuretic peptide
released by myocardiocytes in the atria of the heart due to high pressure
inhibit water and sodium reabsorption in the distal convoluted tubule(to reduce blood volume and pressure)
inhibit the secretion of renin
Calcitonin and parathyroid hormone
calcitonin inhibit calcium reabsoprtion in the kidney to reduce blood calcium level
PTH increase calcium reabsorption in the distal convoluted tubules to increase blood calcium levels
ureter
-long straight muscle wall, one per kidney
-mucosa, muscolaris externa and adventitia
->the layers become gradually thicker as we get closer to the bladder
-protective transitional epithelium
3 layers of cells
1. single layer of basal cells attached to the basement membrane
2. one or multiple layers of cuboidal/low columnar cells
3. highly differentiated large bulbous or elliptical umbrella cells (sometimes binucleated) that protect the underlying tissue from the possible cytotoxic effects of highly concentrated urine
lamina propria made of dense connective tissue lie underneath the epithelium
the MUCOSA (lamina propria+ epithelium) is protective
what is the epithelium characteristic of the urinary tract?
transitional epithelium
uroplakins
integral membrane proteins that contribute to give the urothelium its protective function by assembling into arrays of stiffened plaques
composition of the muscolaris of the upper 2/3 of the ureter
2 muscle layers
internal longitudinal layer
external circular layer
composition of the muscolaris of the lower 1/3 of the ureter
3 muscle layers
internal longitudinal
middle circular
external longitudinal
detrusor muscle of the bladder layers
3 layers, poorly defined
internal longitudinal
middle circular
external longitudinal
where is muscle more developed in between urether and bladder?
in the bladder
type of epithelium in the urethra
pseudostratified/stratified columnar that transitions into stratified squamous
muscolaris in the urethra
smooth muscle cells oriented longitudinally sorrounded in the middle part by striated muscle cells of the sphincter urethrae
3 segments of the male urethra
prostatic, membranous and penile urethra
epithelium of urethra
close to the bladder: transitional epithelium similar to the bladder one
mid urethra: stratified/pseudostratified columnar epithelium
distal urethra: stratified squamous epithelium
