Dr. Mhawi 4 Urinary System Flashcards

Question

Where are the poles locate in this image

Answer 1

## Footnote 8.6.1

Answer 2

Bowmans capsule

Answer 3

bowmans capsule ## Footnote 8.6.1

Answer 4

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.

Answer 5

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_

Answer 6

**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

Answer 7

**_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**

Answer 8

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.

Answer 9

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.

Answer 10

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.

Answer 11

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.

Answer 12

Id the podocyte

Answer 13

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).

Answer 14

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.

Answer 15

•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_

Answer 16

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

Answer 17

filtarition slits

Answer 18

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

Answer 19

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

Answer 20

Lamina rara interna –adjacent to capillary endothelium Lamina rara externa –adjacent to podocyte processes Lamina densa –fused portion of basal laminae –sandwiched between laminae rarae

Answer 21

Laminae rarae –rich in **_polyanion GAGs_** such as _heparan sulfate_ –impede passage of negatively charged molecules _(charge-selective barrier)_ Lamina densa –T**ype IV collagen** concentrated in Lamina densa organized into feltwork (fibrous network) that acts as size-selective barrier prevents movement of particles (proteins) larger than 70,000 Daltons Large amount of albumin in urine (albuminuria) is due to damaged GBM Small amount is normal

Answer 22

Sialoglycoproteins

Answer 23

deposition

Answer 24

Mesangial cells –group of cells in renal corpuscle Located in vascular stalk of glomerulus Mesangial cells secret matrix –mesangial cells & their matrix called mesangium –in diabetes mesangium increased concurrently with the GBM thickening Mesangial cells like pericytes –enclosed by basal lamina of glomerular capillaries

Answer 25

MC, mesengeal cell,

Answer 26

glomerulus Capiliary, mesengial cell found between them, podocyte on outside ## Footnote 8.6.1

Answer 27

P-podocyte; MM-mesangium; M-mesangial cell; BS-Bowman’s space; BC-Bowman’s capsule 8.6.1

Answer 28

1- Juxtaglomerular cells 2- Macula densa 3- Extraglomerular mesangial cells (Lacis cells)

Answer 29

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.

Answer 30

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.

Answer 31

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).

Answer 32

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 8.6.1

Answer 33

White arrow indicates macula densa. Green arrow demonstrates Lacis cells.

Answer 34

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.

Answer 35

## Footnote 8.6.1

Answer 36

Located in the cortical labyrinth **Wider i**n 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 microvill**i apically Reason for fuzzy or **star-shaped lumen** in LM

Answer 37

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.

Answer 38

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.

Answer 39

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.

Answer 40

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.

Answer 41

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.

Answer 42

Lots of mitochondria b/c actively transport Na Cl to surrounding interstitium ## Footnote 8.6.1

Answer 43

Star shaped nucleus of PCT

Answer 44

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.

Answer 45

## Footnote 8.6.1

Answer 46

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.

Answer 47

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.

Answer 48

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.

Answer 49

–resorb water 8.6.1

Answer 50

**Light cells (also called principle cells)** Main cells of system Pale staining Possess w**ater 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.

Answer 51

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** 8. 6.1 8. 6.1

Answer 52

Urteter, transitional ## Footnote 8.6.1