Microanatomy renal system Flashcards
What are the functions of the renal system?
- Filter blood to form filtrate
- Eliminate toxic nitrogenous waste
- balance composition and volume of blood to maintain homeostasis
Describe the anatomy of a kidney?
- multilobar
- each lobe made up of outer cortex and inner medulla with a renal papilla
Through what vessels does urine flow through?
- papillae release urine to minor calyces
- minor calyces > Major calyces > renal pelvis > Ureter
What are the main blood vessels in entering kidneys?
Renal vein and renal artery which join the abdominal aorta and inferior vena cava
What are Calyces?
vessels with cup like heads found at the base of the medulla
What is the function of nephrons?
filtration, reabsorption and excretion
What is a nephron?
Blind-ending (closed at one end) epithelium lined hollow tubule
What are the parts of the nephron?
- renal corpuscle (Bowmans capsule + glomerulus)
- proximal convoluted tubule
- loop of Henle
- distal convoluted tubule
Where does the urine drain into after leaving the nephron?
Collecting duct (not technically part of nephron)
How does the renal corpuscle develop?
Glomerulus invaginates into bowman capsule pushing the ‘visceral layer’ back into itself
Where is the juxtaglomerular complex located?
intersection of distal convoluted tubule and the efferent and afferent arteriole
What cells are located at the JG complex?
1) Macula Densa (part of distal convoluted tubule)
2) Juxtaglomerular cells (tunica media of afferent arteriole
3) Lacis cells (in-between two arterioles)
What is the function of macula dense?
- chemoreceptors which monitor luminal sodium concentration and if need to will adjust glomerular filtration rate
- signal JG within wall of afferent arteriole which secrete renin
What type of epithelium is the visceral layer of bowman capsule and what is the name of the cells?
Simple squamous
podocytes
What vessels drain urine from kidneys and from bladder?
Ureters = from kidneys urethra = from bladder
What structure enter and leave the hilum of the kidneys?
Renal vein and artery and the ureters
Where are the renal papillae located?
at the base of the medulla, before calyx
Can damage to nephrons be reversed?
No
Which part of the nephron is the closed end?
renal corpuscle
What parts of the nephrons are in the cortex and what parts are in the medulla?
cortex: proximal and distal convoluted tubules and renal corpuscle
Medulla: loop of Henle and major of blood vessels which form vasa recta
At what point is filtrate classed as urine?
When enters collecting duct
What are the exit and entry points of the glomerulus called?
Vascular pole = where afferent (entry) and efferent arteriole (exit)
Urinary pole = exit point of the filtrate
Describe the structure of the renal corpuscle?
- outer layer is the parietal epithelium
- also contain inner visceral epithelial layer
- space between layer is the bowman space
- glomerulus (bundle of blood vessels) is at centre surrounded by the visceral epithelium
What is the difference between the afferent and efferent arteriole?
- efferent has a smaller lumen - blood exiting nephron is under higher pressure
- means blood back up in the glomerulus and so has more time to be filtered
What cells makes up the blood-filtration barrier in the renal corpuscle?
- fenestrated endothelium of glomerular capillaries
- fused basal laminae of capillaries and podocytes
- podocytes of visceral epithelium
What is the function of the JG cells?
secrete renin which stimulates release of Ang II into blood which causes vasoconstriction of efferent arteriole to increase in GFR due to pressure difference
What is the chain of blood vessels which supply the kidney?
Renal artery > Interlobar artery > Arcuate Artery > Cortical radial/interlobular a. > Afferent arteriole > Glomeruli > Efferent arteriole > Peritubular/intertubular capillaries > Venous return
Where would you find the interloper arteries?
Between lobes run up the medullary area
Where are arcuate arteries located?
In between cortex and medulla
Where do cortical radial arteries travel?
Up through cortex toward bowmen capsule of kidney
Where are the intertubular capillaries located?
wrap around the proximal tubule and down to the medulla and help to from vasa recta which surrounds the loop of henle
What are the adaptions of the podocytes?
- wrap around capillaries of glomerulus
- develop primary and secondary processes
- secondary are fingerlike extensions which are used as site of filtration (contain filtration slits)
- means only smaller sized molecules can move through
Describe the histology of the proximal convoluted tubules?
- epithelial lining contains numerous microvilli and basal invaginations which contain sodium complexes
What epithelial lining does the proximal convoluted tubule have?
Simple cuboidal epithelium
What is the function of the sodium complexes in the proximal convoluted tubule?
- reabsorb water, potassium, ions, glucose and amino acids
- these are returned to efferent arteriole
What are the epithelial linings in the loop of Henlé?
thin portion has simple squamous
thick portion has simple cuboidal
By what process is urine concentrated in the loop of henle?
Counter-current multiplier
What blood vessels can be found running alongside the loop of henle?
Vasa recta
What is the difference between the histology of the distal and proximal tubules?
- Distal has the cuboidal epithelium but no microvilli
- Less convoluted (coiled)
- less reabsorption in distal
- contain macula densa
What can be regulated in the distal convoluted tubule?
Potassium, sodium, calcium and PH
What three vessels is liquid passed down after leaving nephrons to reach the papillae and then calyces?
Collecting tubules > Collecting ducts > Ducts of Bellini
What epithelium is found in the collecting ducts?
Simple cuboidal (tubule) simple columnar (Bellini)
What epithelium can be found in renal calyces?
Transitional epithelium 2-3 cell thick
What features of the calyces help in movement to the bladder?
- well developed smooth muscle
- no defined layers
- able to create peristaltic contractions promoting emptying of urine from papillae to calyces
Describe the histology of the ureter?
- transitional epithelium 4-5 cell thick
- contains lamina propria and elastic fibres
- Then two layer of smooth muscle (longitudinal and circular)
- except at distal end where three layers
- smooth muscle allows for peristaltic contraction
What structures in the urinary system contain transitional epithelium and what is it?
- Bladder, ureter and calyces
- able to change shape
- when structure empty cells rounded and fat, when structure distends (fills) then flatten and become squamous
Describe histology of bladder?
- Transitional epithelium 6-8 cell thick
- Epithelium also contain Umbrella cells which are able to open to flatten them and close to make themselves more rounded
- Layer of lamina propriety with fibroelastic connective tissue and blood vessels within
- 3 large indistinct layers of smooth muscle
