Dr. Mhawi 4 Urinary System Flashcards
What are the two regions of the kidney?
8.6.1
nDivided into 2 regions
–cortex
–medulla
90-95% of blood passing through kidney is in cortex
n5-10% of the blood goes through the medulla
_____ are Sections of kidney reveal series of vertical striations
MEDULLARY RAYS
–consist of:
§straight tubules of the nephrons
§and cortical collecting ducts
Explain the image
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Section of the kidney perpendicular to its surface. Arrows indicate the medullary rays. AA, arcuate artery; AV, arcuate vein; RC, renal corpuscle.
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Regions between medullary rays is called _____
CORTICAL LABYRINTH
Consists of:
nconvoluted tubules of the nephron
renal corpuscles
nand interlobular arteries and veins
Know this image
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Know this image
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Know this image
Explain this image
Solid arrow, cortical labyrinth; dashed arrow, medullary rays.
Explain this image
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Medullary rays visible in cross sections surrounded by the cortical labyrinth.
Renal cortex. MR, medullary ray in cross section; RC, renal corpuscle. The rest of the image is filled with the cortical labyrinth in which the proximal and distal convoluted tubules display round, oval, curved and elongated profiles, depending on the sectioning plane.
Explain this image
This illustration represents small piece of tissue taken from the kidney cortex. In kidney cortex, renal corpuscles (red circles), cortical labyrinth (formed by the winding of proximal and distal convoluted tubules), and straight tubules that constitutes the medullary ray are usually encountered. Because of their highly tortuous course, the sectioned proximal and distal convoluted tubules exhibit variable profiles regardless of the sectioning plane. However, straight tubules of the medullary ray appear as long tubules parallel to each other when they are cut longitudinal to their long exes and as circles when the section is made perpendicular to their long exes.
_____ contains straight tubules and blood vessels involved in the urine concentration
Medulla
–straight tubules of the loop of Henle
–Create the countercurrent multiplier system
–Produces osmotic gradient in the medulla
–medullary collecting ducts
–vasa recta
–blood vessels that run parallel to loop of Henle and collecting ducts
–Create the countercurrent exchange system
A, medulla; B, cortex; 1, renal corpuscle; 4, straight tubule of the nephron; 6, collecting duct; 7, arcuate artery; 8, interlobular artery; 9, afferent arteriole; 10, efferent arteriole; 11, peritubular capillaries; 12, vasa recta; 23, capsule; 24, papillary duct (of Bellini); 25, interlobar artery.
Explain the image
–called renal columns
(of Birtin)
Anchor cortex to medulla
Contains
–interlobar artery, vein and lymphatics
–supportive connective tissue
Renal pyramid is depicted in yellow. Cortex and renal columns are in brown.
What is a lobe compared to a lobule
Each lobe is comprised of lobules:
- Lobule consists of one medullary ray and half of the surrounding cortical labyrinth on either side
What is the arterial blood supply of the kidney?
- Each kidney is supplied by a r_enal artery_ (major blood supply)
- Renal artery branches into interlobar arteries
–Travel between the lobes (in the renal columns) up to the level of the cortex
–Then turn to follow an arched course between the cortex and medulla
–Here they are called the arcuate arteries
•Arcuate arteries branch into
•interlobular arteries
–Ascend in the cortical labyrinth toward the capsule
- Give off afferent arterioles
- One to each renal corpuscle
Explain the image
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In this section the renal artery is injected with colored colloidin and a whole mount prepared to reveal details of the kidney blood supply.
Explain this image
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Kidney vessels injected with dye. Note that the interlobular artery (IA) branches into several afferent arterioles (AA). Each afferent arteriole enters a renal corpuscle to branch again into several capillary loops known as glomerulus (G). Glomerulus is drained by the efferent arterioles (EA), only the initial portion of which is visible in this section.
Explain this image
BS, Bowman’s space; IA, interlobular artery; G, glomerulus; AA, afferent arteriole; EA, efferent arteriole; RT, renal tubules
Explain this image
Scanning electron micrograph of a cast of the kidney cortex. IA, interlobular artery; AA, afferent arteriole; G, glomerulus which is comprised of the glomerular capillary loops (CL).
Explain this image
Scanning electron micrograph of a cast of a glomerulus with its many capillary loops (CL) and adjacent interlobular vessels. The afferent arteriole (AA) takes its origin from an interlobular artery (IA) at lower left. The efferent arteriole (EA) branches to form the peritubular capillary plexus (upper left).
Explain this image
•Efferent arterioles from the juxtamedullary glomeruli (circles) descend to the medulla
–Form the vasa recta
- Loops of blood vessels
- Run parallel to loop of Henle
- Two parts:
–Descending arteriolae rectae
–Ascending venulae rectae
•Create countercurrent exchange system
–Maintains osmotic gradient of the medulla
What are the two parts of the nephron
Renal corpuscle
- Tubule system
In bowmans capsule, what are the two layers, the spacesand the two poles
- parietal layer: consists of simple squamous epithelium
- continuous with simple cuboidal epithelium of the proximal convoluted tubules
- visceral layer: consists of the cytoplasmic processes of podocyte cells
- podocytes cover the glomerulus
§The two layers surround space
§Called urinary space (AKA Bowman’s space)
§Receives blood ultrafiltrate
§Bowman’s capsule has two poles:
- Vascular pole: where afferent and efferent arterioles penetrate and exit the capsule, respectively
- Urinary Pole: beginning of the proximal convoluted tubule
Know this image
8.6.1
Where are the poles locate in this image
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Explain this image
Bowmans capsule
ID this image
bowmans capsule
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Id this image
SEM of cortex of rat kidney showing two renal corpuscles, the top one containing a glomerulus, the lower showing parietal epithelium of Bowman’s capsule with a urinary pole (arrow) opening to a proximal convoluted tubule. Proximal (p) and distal (d) convoluted tubules, peritubular capillaries (c), and major blood vessels (v) are seen also.
What are the 3 segments of the tubular nephron system
Following Bowman’s Capsule are:
Proximal thick segment
–Proximal convoluted tubule
–Proximal straight tubule
–Normally referred to as
Thick descending segment of the loop of Henle
Thin Segment
–thin limb of Loop of Henle
nDistal thick Segment
- Distal straight tubule
- Normally referred to as
Thick ascending segment of the loop of Henle
- Distal convoluted tubule
What are 3 types of nephrons?
Cortical or Subcapsular Nephrons
–Corpuscles located in outer cortex
–Have short loops of Henle
Juxtamedullary Nephrons
–Corpuscles located in proximity to base of medullary pyramid
–Have long loops of Henle
Intermediate Nephrons :
–Renal corpuscles in midregion of cortex
–Loops of Henle of intermediate length
What are the three components in the wall of the glomerular capillaries
1- Endothelium of glomerular capillaries
- Possesses numerous large fenestration
- Fenestration has no diaphragm
- Restricts movement of blood cells & formed elements of blood
- Endothelial cells possess large number of water channel aquaporin-1 (AQP-1)
2- Glomerular basement membrane (GBM)
-Located between the endothelial cells and the podocytes
-Joint product of the two cell types
3- Visceral layer of Bowman’s capsule
- Consists of cytoplasmic processes of specialized cells called podocytes
Explain the image
Cross section of one of the glomerular capillaries. The three elements of the filtration apparatus, fenestrated endothelial cell, GBM, and visceral layer of Bowman capsule, which consists of the cytoplasmic processes of podocytes, are visible. The components within the red rectangle will be shown at higher magnification in the next two slides.
Explain the image
The components of the filtration apparatus are highly magnified in this TEM. These components include the fenestrated endothelial cell (E) of the capillary, glomerular basement membrane (GBM), and the visceral layer of bowman’s capsule, which is comprised by specialized epithelial cell, the podocytes processes. Arrow heads point to the endothelial cell fenestrae. Pedicels, the terminal cytoplasmic processes of the podocyte cells are visible (thick arrows). Thin arrows point to the filtration slit diaphragm. RBC, red blood cell.
Explain the image
Electron micrograph of the filtration barrier (apparatus) in a renal corpuscle (this TEM image represents the boxed area of the previous slide). Note the endothelium (E) with open fenestrae (arrowhead), the fused basal laminae (BL) of epithelial and endothelial cells, and the processes of podocytes (P). The basement membrane consists of a central lamina densa bounded on both sides by a light-staining lamina rara. Arrows indicate the thin diaphragms crossing the filtration slits.
_______ constitute the visceral (inner) layer of Bowman’s capsule
Podocytes
Send primary processes around glomerular capillaries
branch into:
Secondary processes
- give rise to pedicels
or foot processes
Interdigitate with pedicels from another podocyte
Spaces between adjacent pedicels are Filtration slits
SEM of the glomerular capillary covered with podocytes.
Explain this image
Id the podocyte
Explain the image
Scanning electron micrograph showing Bowman’s visceral epithelial cells, or podocytes (P), surrounding capillaries of the renal glomerulus. Two orders of branching of the podocyte processes are apparent: the primary processes (1) and the secondary processes (2). Note that pedicels (asterisks) are branching from the secondary processes. The small spaces between adjacent pedicels constitute the filtration slits (arrows).
Explain the image
Electron micrograph showing the cell bodies of 2 podocytes and the alternation of secondary processes from 2 different cells (arrows). The urinary space and the glomerular capillary are indicated.
Explain the image
•Podocytes:
–Described as epithelial cells
•Because they are polarized and resting on a basal lamina
–Possess similarity to smooth muscles
•Due to the presence of actin filaments in their cytoplasm
None dividing
Explain the image
filtraition
–Spaces between two pedicels
–40 nm wide
–allow blood filtrate to enter urinary (Bowman’s) space
–exclude plasma proteins
–permit water, glucose, amino acids and metabolic waste products to pass
–In healthy people glucose is reabsorbed in the kidney tubules
–act as physical barriers to bulk flow and free diffusion
Explain the image
filtarition slits
Explain the filtration slit membrane
Filtration slits are controlled by a filtration slit membrane (diaphragm)
Size-selective barrier to filtration of proteins
- porous 4-6 nm thick membrane
- formed by transmembrane protein nephrins
- have long extracellular domain
- extracellular domains from adjacent pedicels interdigitate with
each other
- intracellular domain is anchored to actin filaments of podocyte
cytoplasm
- mutation to the genes encoding nephrin leads to proteinuria
What is the ground basement membrane?
Thick, 300-350 nm
–j_oint product of endothelium and podocyte_
–Visible in PAS-stained sections
Serves as size-selective and charge-selective barrier
Becomes thicker in patient with diabetes type 1 or 2
Explain the image
MC, mesengeal cell,
Explain the image
glomerulus Capiliary, mesengial cell found between them, podocyte on outside
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What are the 3 cells of the juxtaglomerular apparatus?
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1- Juxtaglomerular cells
2- Macula densa
3- Extraglomerular
mesangial cells (Lacis
cells)
Explain the image of juxtaglomerular cells.
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They are modified smooth muscle cells of the afferent arterioles at the site of entry into the renal corpuscle
- occasionally found in the efferent arteriole
- mechanoreceptors
–contain secretory granules
–Granules contain RENIN
- angiotensin, rening regulates BP
–have spherical nuclei (unlike smooth muscle)
Photomicrograph of an afferent arteriole entering a renal corpuscle. The wall of this arteriole shows the renin-producing juxtaglomerular cells (arrow heads). Note the presence of renin granules stored in the cytoplasm of these cells. Arrow indicates the direction of blood flow.
Explain the image
Afferent arteriole (solid arrow) enters the renal corpuscle (RC). The smooth muscle cells in the wall of the afferent arteriole at its entry into the renal corpuscle are called juxtaglomerular cells. They are cuboidal cells with round nuclei rather than elongated. They synthesize and store renin granules in their cytoplasm (not visible at this magnification). The efferent arteriole, indicated by the dashed arrow, drains the blood from the glomerulus and branches into peritubular capillaries.
Explain the role of the macula densa and the image
MACULA DENSA
–Marks the very beginning of the distal convoluted tubule (DCT) of the nephron
–Monitor Na+ concentration in DCT
–i.e., they are osmoreceptors
–Regulates renin secretion from the juxtaglomerular cells
Macula densa cells, mark the beginning of the DCT, are indicated by the asterisk. Note the presence of the juxtaglomerular cells (solid arrows) in the wall of the afferent arteriole (AA) and Lacis cells (dashed arrow).
Explain image
Photomicrograph of renal cortex. A macula densa is clearly seen (arrow) at the vascular pole of a renal corpuscle. Picrosirius-hematoxylin (PSH) stain. Medium magnification
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Explain image
Explain the image
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White arrow indicates macula densa. Green arrow demonstrates Lacis cells.
Explain the image
Transmission electron micrograph of juxtaglomerular apparatus from rabbit kidney, illustrating macula densa (MD), extraglomerular mesangium (EM), and a portion of afferent arteriole (AA), of which a juxtaglomerular cell containing numerous renin granules (star) is visible. DCT, distal convoluted tubules.
RAAS
8.6.1
What are the characteristics of proximal convoluted tubules
Located in the cortical labyrinth
Wider in outer diameter than the DCT
Longer than DCT
More sections in field of view
Most of the ultrafiltrate is reabsorbed here
Cuboidal cells
Cells possess features required for absorption
Long microvilli apically
Reason for fuzzy or star-shaped lumen in LM
Explain the image
Renal cortex section showing a proximal convoluted tubule (PCT) with its large cuboidal cells presenting a brush border formed by numerous microvilli. Distal convoluted tubules (DCT) are also present. PT stain. Medium magnification.
Explain the image
TEM of renal cortex showing portions of three proximal convoluted tubules (PCT) in transverse section, with part of one distal convoluted tubule (DCT). The proximal tubules show apical microvilli of the brush border (arrow), elongated mitochondria, dense endocytotic bodies, and spherical nuclei with prominent nucleoli. The distal tubule here is lined by low cuboidal epithelium with a few scattered apical microvilli (dashed arrow). Intertubular capillaries (CAP) are in close vicinity of the kidney tubules.
Explain this image
Section of the cortical labyrinth where proximal convoluted tubules (PCT) and distal convoluted tubules (DCT) are found. Note that the lumen of PCT exhibits a star shape when cut transversely. Lumen of the DCT looks cleaner.
Explain this image
Found in the medullary rays
Epithelial Cells are cuboidal
Fewer short microvilli
Lumen still looks fuzzy or star-shaped
Section through the medullary ray and cortical labyrinth. Descending thick segment of the loop of Henle (DT) are located in the medullary ray . The microvilli in their epithelial cells gives the star-shaped appearance of the lumen. They are wider in diameter than the ascending thick segment of the loop of Henle (AT). Note that the lumens of the latter look smooth and clean due to the presence of less microvilli. On the right lower part of the micrograph the cortical labyrinth reveals some proximal convoluted tubules (PCT). CD, collecting duct. Dashed line is the border between the medullary ray and the cortical labyrinth.
Explain this image
Electron micrograph of the thin limb of Henle’s loop (H) composed entirely of squamous cells. Note the adjacent capillaries (C) with erythrocytes and the interstitium (I) with bundles of collagen fibrils.
Explain the characteristics of AT
Lots of mitochondria b/c actively transport Na Cl to surrounding interstitium
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How to tell PCT from DCT?
Star shaped nucleus of PCT
Explain the image
Electron micrograph of atrial heart muscle cell (hamster). The central nucleus (N) is bounded laterally by myofibrils. Under the nucleus there is a region of sarcoplasm containing mitochondria (M), a Golgi (G), and darkly stained atrial granules (ag) that contain atrial natriuretic factor.
Compare and contrast PCT and DCT
Explain the characteristics of collecting tubules and collecting ducts
8.6.1
Explain the image
Renal papilla and calyx. a. This scanning electron micrograph shows the conical structure that represents the renal papilla, projecting into the renal calyx. The apex of the papilla contains openings (arrows) of the collecting ducts (of Bellini). These ducts deliver urine from the pyramids to the minor calyx. The surface of the papilla containing the openings is designated the area cribrosa. (Courtesy of Dr. C. Craig Tisher.) b. Photomicrograph of an H&E–stained specimen of the papilla, showing the distal portion of the collecting ducts opening into the minor calyx.
Explain the image
Collecting ducts. (a): Longitudinally sectioned renal pyramid showing two collecting ducts (CD) and their distinct lateral cell boundaries (arrows), with interstitial connective tissue. X400. H&E. (b): Similar features are seen in transversely sectioned collecting ducts, with vasa recta (VR) present in the interstitium. X600. PT. Collecting ducts adjust the ionic composition of urine in their lumens and allow increased water reabsorption from this urine when fluid levels in the body are low. This occurs under the influence of the posterior pituitary hormone ADH, which causes a greatly increased number of aquaporin water channels to be temporarily inserted into the apical cell membranes of these cells.
Explain the image
Cross section through the medulla demonstrating descending thick (DT) and ascending thick (AT) segments of loop of Henle, collecting duct (CD), and thin segments of loop of Henle (T). Collecting ducts are exhibiting outer diameter almost similar to that of the DT segment of the loop of Henle. However, they can be distinguished from the descending thick segment of loop of Henle by the well defined lateral plasma membrane and by the clean and circular luminal face. One segment of loop of Henle has been cut in the transition face from thick to thin segment (double arrows). Blood capillaries of the vasa recta (VR) are distributed among the nephron and collecting tubules.
What are the two cell types lining the collecting tubules and ducts
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Light cells (also called principle cells)
Main cells of system
Pale staining
Possess water channel
Have basal membrane infoldings
Possess a single cilium with few microvilli
–Dark Cells also called
intercalated cells
Few in number
Many mitochondria (cause of dark cytoplasm)
Provide energy for pumping H+
H+ makes urine acidic
Many microvilli on the apical surface
Increase surface area to insert H+ pumps
Scanning electron micrograph illustrating the luminal surface of a rat cortical collecting duct. The principal cells possess few short microvilli and a single cilium (arrows). The intercalated cells (stars) are few and possess many microvilli.
What are the interstitial cells of the cortex?
Cells resembling fibroblasts (arrows)
located between the tubules and adjacent peritubular capillaries
synthesize and secrete collagen (type III) and GAGs
Evidence of erythropoietin production
–Occasional macrophages
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What is this image and what is its main epithelium
Urteter, transitional
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