Kidney Microanatomy Flashcards
Why do the proximal tubule cells have a lot of microvilli?
To increase the surface area for reabsorption
True or False: The cells of the proximal tubule interdigitate with each other
True
What kind of cells are in the descending loop of henle?
squamous
What type of cell is in the collecting duct?
Columnar
Explain some of the differences between the tubule cross sections under EM.
The ascending thick limb has a lot of mitochondria (black spots) which show that there is a lot of ion transfer.
The collecting tubule has fewer mitochondria so it’s still capable of transport.
The descending thin limb is thinner. Not many mitochondria if at all.
The vasa recta is the thinnest of all. Vasa recta has visible RBCs if using a light microscope.
What’s the difference between vasa recta and peritubular capillaries?
Peritubular capillaries are tiny blood vessels that travel alongside nephrons allowing reabsorption and secretion between blood and the inner lumen of the nephron. Peritubular capillaries surround the proximal and distal tubules, as well as the loop of henle, where they are known as vasa recta.
In other words, vasa recta are the peritubular capillaries that run parallel to the loop of henle.
What are the macula densa?
In the kidney, the macula densa is an area of closely packed specialized cells lining the wall of the cortical thick ascending limb, at the transition to the distal convoluted tubule.
The cells of the macula densa are sensitive to the concentration of sodium chloride in the late thick ascending limb. A decrease in sodium chloride concentration initiates a signal from the macula densa that has two effects: (1) it decreases resistance to blood flow in the afferent arterioles via vasodilation, which increases glomerular capillary hydrostatic pressure and helps increase the glomerulus filtration rate (GFR) toward normal, and (2) it increases renin release from the juxtaglomerular cells of the afferent and efferent arterioles, which are the major storage sites for renin.
As such, an increase in sodium chloride concentration would result in vasoconstriction of afferent arterioles, and reduced paracrine stimulation of juxtaglomerular cells. This demonstrates the macula densa feedback, where compensatory mechanisms act in order to return GFR to normal.
What are juxtaglomerular cells?
The juxtaglomerular cells (JG cells, or granular cells) are cells in the kidney that synthesize, store, and secrete the enzyme renin. They are specialized smooth muscle cells mainly in the walls of the afferent arterioles, and some in the efferent arterioles, that deliver blood to the glomerulus. In synthesizing renin, they play a critical role in the renin-angiotensin system and thus in autoregulation of the kidney.
Juxtaglomerular cells secrete renin in response to a drop in pressure detected by stretch receptors in the vascular walls, or when stimulated by macula densa cells. Macula densa cells are located in the distal convoluted tubule, and stimulate juxtaglomerular cells to release renin when they detect a drop in sodium concentration in tubular fluid. Together, juxtaglomerular cells, extraglomerular mesangial cells and macula densa cells comprise the juxtaglomerular complex.
Describe the epithelium of the bladder
Epithelium of the bladder is transitional epithelium. Transitional epithelium cells stretch readily in order to accommodate fluctuation of volume of the liquid.
What is the general region of the kidney being shown here?
What are A, B, and C?
What’s the web-like stuff?
This is the cortex. You can tell because of the presence of renal corpuscles.
A = outer capsule
B = glomeruli
C = blood vessels
The web-like stuff is proximal and distal tubules.
What is A?
What is the thing circled in black?
What region of the kidney is circled in yellow?
What region is circled in blue?
A - arcuate vessel
Black circle - glomerulus in the juxtamedullary region (these have loops of henles that run deepest into the medullary region)
Yellow circle - (renal corpuscles in the) juxtamedullary region
Blue circle - medullary region
What is important about nephrons in the juxtamedullary region?
They are important for concentrating urine because their loops of henles go deepest into the medullary region.
The structures labeled A may be part of what cells?
B forms part of ____?
C forms part of ____?
Which are proximal tubules and which are distal?
The structures labeled A are nuclei that may be part of podocytes, capillary endothelial cells, and mesangial cells. We are not expected to know which kind of cell based on the nuclei.
B form part of the parietal epithelium of the bowman’s capsule.
C forms part of the macula densa.
The proximal tubules have a fuzzy inner wall because of the microvilli and the distal tubules do not have the fuzzy inner wall.
What is A? What is normally inside of A?
What is normally inside of B?
C is the lumen of?
What is one function of the cells labeled E?
Following the little black arrow, what 3 layers are crossed?
A - arteriole (either afferent or efferent), normally blood is inside A
B - urinary (plasma) filtrate
C - proximal tubule (you can see the fuzzy microvilli)
E - secrete renin (juxtaglomerular cells)
Arrow crosses the filtration barrier (1. fenestrated endothelial cell, 2. basal lamina, 3. podocytes)
What maintains the basal lamina of glomeruli?
Podocytes and endothelial cells
Would water flow from A to B or B to A?
A is in the lumen of?
The tips of the arrows point at?
What is the circled thing at number 4?
What is 2?
What is 6?
Water flows from A to B.
A is in the lumen of glomerular capillary.
The tips of the arrows point at the fenestrated endothelium.
The circled thing at number 4 is the filtration barrier.
2 is the nucleus of the endothelial cell.
6 is the mesangial cell.
What part of the kidney is shown?
What is A in the lumen of?
What is B in the lumen of?
What is C in the lumen of?
Medulla.
A is in the lumen of a collecting duct (columnar cells). The main role of this epithelium is for water reabsorption in the presence of vasopressin (ADH).
B is in the lumen of either an ascending or descending thick limb of a loop of henle (cuboidal cells).
C is in the lumen of vasa recta (because you can see RBCs).
What portion of the kidney is shown here?
What is A in the lumen of?
What are B?
These are the papillary ducts (ducts of bellini) which represent the most distal portion of the collecting duct system.
Within the lumen of collecting ducts.
B - these are either vasa recta or portions of the loop of henle of the juxtamedullary nephrons (the ones that go very deep into the medulla). We won’t be expected to tell the difference between these.
What are A, B, and C?
A is a continuous epithelial layer
B is the minor calyx.
C is a duct of bellini.
What is the yellow line?
What is the green line?
What are the two vessels in the top left?
What is the rest of the pink stuff?
Yellow line - transitional epithelium
Green line - lamina propria (highly stretchy elastic fibers)
The round vessel is the arteriole (layers of smooth muscle) and the wiggly one is the vein.
The rest is stretchy connective tissue of the bladder.
