Histology of the Kidney

Question	Answer
What is the function of the kidney?	The kidney filters things out of the blood that are harmful or not needed for excretion in the urine. It also maintains homeostasis.
What capsule surrounds the kidney?	A connective tissue capsule.
What are the two major regions in the kidney?	The cortex and the medulla.
What two parts form the cortex of the kidney?	The cortical labyrinth and the medullary rays.
Which part of the nephron are in the cortical labyrinth of the cortex?	The renal corpuscles, cross sections of the PCT, DCT and macula densa cells.
What parts of the nephron are in the medullary rays of the cortex?	The collecting tubules, PCT and ascending limb of Henles loop.
True or false: the countercurrent exchange system is held in the medulla of the kidney.	TRUE.
Where are caps of cortical tissue found in the medulla?	Around lateral portions of medullary pyramids and between them forming renal columns. NB the medulla contains some components of cortical tissue but it is still the medulla.
What does the renal artery branch into?	The interlobular arteries.
When the arteries are between the medulla and the cortex what are they called?	Arcuate arteries.
What is the difference in vasculature in cortical nephrons and juxtamedullary nephrons (specifically the laters part of the vasculature)?	Cortical nephrons - form peritubular network Juxtamedullary nephron - form vasa recta in medulla
What is the nephron? What is it responsible for?	The functional unit of the kidney that is responsible for production of urine.
What makes up the renal corpuscle?	Glomerulus, Bowmans capsule and Bowmans Space
What is the glomerulus?	The capillary network responsible for initial filtration of blood.
What percentage of the fenestrated capillaries of the glomerulus do pores occupy?	20% of the total area (allow passage of small molecules)
What is the layer of epithelial cells called that coats the blood vessels in the bowmans capsule (coats the glomerulus)? What are their main features?	Podocytes. Numerous, long, tentacle like extensions called pedicles wrapping around the glomerulus. They leave filtration spaces for fluid to go from glomerular capillaries to BC.
What makes up the filtration membrane of the glomerulus?	Fusion of the endothelial membrane of the glomerulus and the inner epithelial membrane of the bowmans capsule.
What cannot be filtered by the glomerulus?	Plasma proteins, blood, molecules over 1kDa.
What is the function of intraglomerular mesangial cells?	They act like macrophages to remove matter that would otherwise clog filtration sites in the glomerulus. They also secrete mesangial matrix, vasoactive factors and have contractile properties.
What is the name given to extraglomerular mesangial cells?	Lacis cells
True or false: the tubular and collecting systems in the kidney are made up of more than just a single layer of epithelial cells.	FALSE. they are made of a single layer of epithelial cells and have similar basic structure.
Which part of the nephron is the major site of resorption?What kind of epithelia lines this part of the nephron?	The PCT. Simple cuboidal epithelium
What are some of the special features of the PCT to allow it to perform resorption of substances?	Acidophilic cytoplasm, numerous mitochondria for pumps, apical cells have microvili and canaliculi to increase surface area, basolateral side of cells has interdigitations with many Na/K pumps
What is reabsorbed in the PCT?	All glucose, amino acids, some water and sodium chloride.
What does the permeability of the thick and thin parts of the loop of henle depend on?	The type of epithelial cells lining the tubule.
What kind of epithelial cells line the thin limb of the loop of hence?	Squamous epithelial cells.
What kind of epithelial cells line the thick segments of the L of H?	Simple cuboidal epithelial cells.
What three things make up the distal tubules of the nephron in the kidney?	Thick limb of henle, MC cells and DCT
What kind of epithelial cells line the DCT? What are some of the special characteristic of the DCT to assist its function?	Simple cuboidal epithelium. The basolateral membrane interdigitates to increase surface area. There are lots of mitochondria for pumps.
Which part of the kidney is the main site of resorption of Na?	DCT.
What are the two types of cells in the collecting duct?	Clear cells - cuboid or flat with few organelles Dark cells - rich in organelles especially mitochondria
What three types of cells form the juxtaglomerular apparatus?	Macula densa cells (MD), juxtaglomerular cells and extraglomerular mesangial cells (lacis cells)
What are macula densa cells sensitive to? What is the difference in their epithelia?	They are sensitive to flow through the tubule and the concentration of Na and Cl ions in the fluid. Their eipthelial cells are taller, thinner and have more prominent nuclei.
Where would you find juxtaglomerular cells and how are they modified?	They are found in the afferent arteriole before the bowmans capsule. They are modified smooth muscle cells with cytoplasm full of secretory granules.
Where are lacis cells found?	between the afferent and efferent arterioles. Also known as extraglomerular mesangial cells.
What are the two types of cells in the collecting duct? What are their functions.	Principal - few organelles, reabsorb Na and secrete K Intercalated - main organelles, secrete H and reabsorb HCO3. Can alter their permeability to water.
Once urine has been transported through the collecting ducts where does it flow in to?	Ducts of bellini.
What kind of epithelium is found in extra renal tubes? How it is specialised for its function?	Transitional epitelium. It is stratified and can vary the amount of layers it has - 3 when bladder is empty, 6 when bladder is full.

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