Two Flashcards

(24 cards)

1
Q

Describe the renal cortex. What is located there? What are the 2 parts of it? What is located in each?

A

One cm thick​
Covers base, sides (Columns of Bertin) of medulla pyramids​
Contains glomeruli, convoluted and straight tubules, cortical collecting ducts

Cortical labyrinth: glomeruli, proximal, distal convoluted tubules, interlobular vessels, capillaries, connecting tubules, initial collecting tubules.​

Medullary ray: parallel striations, straight part of proximal, distal tubules, collecting ducts. ​

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2
Q

Describe the renal medulla. What are the different layers and what is located there?

A

Internal to cortex, divided into 8-12 conical pyramids​
Base faces cortex (corticomedullary junction)​
Tip (papilla) faces minor calyx.

Outer juxtacortical medulla (next to cortex) ​
Corticomedullary junction ​
Inner and outer stripe ​

Inner medulla includes papilla (pyramid apex) ​
Mostly collecting ducts​
Papilla perforated by collecting ducts, protrudes into a minor calyx

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3
Q

What is the functional unit of the kidney? What are the components? How many are there in the kidney?

A
Functional unit of kidney​
1,000,000 nephrons/kidney​
Includes renal corpuscle, attached tubule with 3 segments​
Proximal tubule​
Loop of Henle​
Distal tubule
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4
Q

What are the two steps in urine formation?

A

Ultrafiltration of blood plasma across semi-permeable filtration barrier in glomerulus ​
Reabsorption and secretion in tubules.

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5
Q

What are the parts of the renal corpuscle?

A

Bowman’s Capsule​
Bowman’s (Urinary) Space​
Glomerulus – “the filter”

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6
Q

What is a glomerulus? How are glomerular capillaries unique? What tonic control are they under? What does their unique anatomy insure?

A

Ball of 10-20 interconnected capillaries wrapped around central mesangium ​
Glomerular capillaries are unique ​
Capillary bed between 2 muscular arterioles: afferent + efferent arterioles (not arteriole + venule). ​
Under tonic control by vasoactive substances (eicosanoids, nitric oxide, etc.) ​
Anatomy insures high capillary hydrostatic pressure, drives filtration.

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7
Q

What is Bowman’s capsule? What is its function? What cells is it made up of? Describe its poles.

A

Pouch of proximal tubule around glomerular capillary loops​

Captures filtrate; sends it to proximal tubule ​
Simple squamous parietal epithelium​
Two poles ​
Vascular pole: Afferent and efferent arterioles ​
Urinary (tubular) pole: Proximal tubule attachment

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8
Q

What is Bowman’s space? What cells are located their?

A
Between glomerulus and capsule​
Continuous with proximal tubule lumen​
Lined by ​
Parietal epithelial cells ​
Visceral epithelial cells (VEC, podocytes)
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9
Q

How does the structure of the glomerulus relate to its function? What are its 4 components?

A

Maximum surface area for filtration ​
13 km capillary length; 1.6 m2 surface area​
High permeability to water, small solutes​
Low permeability to plasma proteins the size of albumin (MW 68,000) and larger, cells

Visceral epithelium (podocyte)​
Glomerular basement membrane​
Endothelium ​
Mesangium

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10
Q

What is the mesangium? What are the two parts? Subparts?

A

In center of glomerulus ​
Mesos middle + angeion vessel​
Structural support for capillary network​
Includes ​
Mesangial matrix​
Mesangial cells​
Phagocytic cells derived from circulating monocytes​
Contractile cells – modified smooth muscle cells

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11
Q

What is the mesangial matrix made up of?

A

Mesangial cells synthesize and are surrounded by extracellular matrix. ​
Matrix has a similar (but not identical) composition to GBM ​
Type IV collagen, fibronectin, laminin, decorin, tenascin, proteoglycans

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12
Q

Describe the two types of mesangial cells and their function. Overall, what are their functions?

A

Specialized pericytes/smooth muscle cells​
Vasoactive hormone receptors ​
Angiotensin II, atrial natriuetic peptide, prostaglandins ​
Actin-myosin filaments ​
Receptors + filaments allow contraction, response to hormones, vasoactive agents ​
Capillary closure, change in filtration surface area, filtration volume.

“Clean” GBM of “junk” accumulated during filtration. ​
Phagocytize, catabolize filtered/trapped macromolecules (e.g., lipoproteins, immune complexes) ​
Make inflammatory, fibrogenic cytokines with role in glomerular injury response​
IL-1, PDGF, TNF, TGF-, prostaglandins, metalloproteinases

Phagocytosis​
Structural support ​
Secretion​
Regulate GBF, GFR​
Respond to injury​
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13
Q

Describe the structure and function and other names of podocytes.

A

Cover outer surface of capillary loops​
Large cells with cytoplasmic foot processes (pedicels) attached to outer GBM, provide structural support ​
Foot processes adhere to GBM​
Produce most of GBM

GBM synthesis​
Maintenance of permselectivity ​
Negative charge, slit diaphragm​
Structural support for capillary

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14
Q

Describe the specialized intercellular junctions between podoctyes including the proteins involved and its function.

A

Foot processes attach to each other by 6-nm-thick, 25-60 nm wide filtration slit diaphragm across slit pore​
Nephrin, podocin, -actinin,CD2AP ​

Cytoskeletal filaments regulate slit pore size ​
Actin, tubulin, cytokeratin, synaptopodin

Restricts macromolecule passage​
Slit proteins interact with VEC actin cytoskeleton​
Cytoskeleton rearrangement occurs in proteinuria

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15
Q

What is the anatomy of the GBM? What is the composition? What is its function?

A
300-350 nm thick​
Made by VEC​
Three layers​
Lamina Rara interna​
Lamina Densa​
Lamina Rara externa

Type IV collagen, sialoglycoproteins, noncollagenous glycoproteins (laminin, fibronectin, nidogen), glycosaminoglycans (heparin sulfate)​

Restricts filtration based on molecule size, charge and configuration

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16
Q

Describe the structure and function of glomerular endothelial cells.

A

Line capillaries ​
Fenestrated (perforated) ​
70-100 nm fenestrae without diaphragm​
Larger, more numerous than in other organs​
Negative charged surface ​
Polyanionic glycoproteins contribute to charge selective barrier of GCW ​
Prevent filtration of RBC, WBC, platelets.

17
Q

Where does urine formation begin? What percent of plasma flowing through glomerulus is filtered? What passes through? What doesn’t pass through? Explain what causes this selective filtration.

A

Urine formation begins at GCW ​
20% of plasma that flows thru glomerulus is removed by filtration across GCW ​
GCW permeable to H2O, small MW molecules, electrolytes.
Impermeable to proteins, larger molecules, cells

Two size pores​
A few large pores – minimal large proteins​
Lots of small pores – water, electrolytes, small proteins ​

Negative charge also important​
Negatively charged sialoglycoproteins on GCW impede filtration of anionic proteins

18
Q

What is the function of the tubules? Generally, How do they tubular segments differ? What are 3 different ways to differentiate them?

A

Tubule reabsorbs (water, sodium, bicarbonate, glucose), secretes (creatinine, organic acids and bases, drugs)​

Divided in segments with different functions ​

Epithelial cells in each segment have unique morphology, correlates with function.

Course – Convoluted or straight​
Location – Proximal or distal ​
Wall thickness – Thick or thin ​

19
Q

Describe the tight junctions of the tubular cells.

A

Near lumen​
Bind cells together​
“Tightness” varies with segment​
Early tubules more “leaky” than late

20
Q

Describe the different tubular segments including where they are located.

A

Proximal thick segment​
Proximal convoluted tubule (PCT, pars convoluta) in cortex​
Proximal straight tubule (pars recta, thick descending limb) in outer medulla​

Thin segment - thin limb of loop of Henle​ in medulla (outer and inner)

Distal thick segment​
Distal straight segment (pars recta, thick ascending limb, TAL) ​in outer medulla
Distal convoluted tubule (DCT, pars convoluta) in cortex

21
Q

Contrast the short vs. long loop nephrons. Why are long loop nephrons important?

A

Based on length of thin limb of Henle ​

Short loop nephron (cortical nephron)​
Glomeruli in superficial/mid-cortical region. ​
80-90% of nephrons​

Long loop nephron (juxtamedullary nephron)​
Juxtamedullary glomeruli, deep in cortex at corticomedullary junction.
“Juxtamedullary nephron” ​
Thin limbs are long, descend to tip of papilla ​
10-20% of nephrons ​
Glomeruli slightly larger than those in superficial cortex ​Important for urinary concentration

22
Q

What is the JGA? Where is it located? Describe it. What are its components?

A

Juxtaglomerular Apparatus

Where they all come together:
Thick ascending limb (TAL)​
Parent glomerulus​
Afferent arteriole

Association of distal TAL epithelium, arteriole, extraglomerular mesangial cells at vascular pole of one nephron.

Macula densa​
Granular cells (JG Cells)​
Extraglomerular mesangial (Goormaghtigh) cells ​
23
Q

What Macula Densa cells? What are they like histologically? What is their function?

A
Modified TAL epithelium. ​
Narrow, tall cells  ​
Closely packed nuclei “macula densa”​
Sensitive to ions, flow in tubule​
Promotes signal from adjacent  mesangial cells ​
Regulates GFR, renal blood flow

“Tubuloglomerular feedback”​

24
Q

What are JG cells like? What is their function?

A

Modified afferent arteriole media ​

Smooth muscle (JG) cells have ​ Myoepithelioid appearance​

No elastic lamina ​

Cytoplasmic renin granules​

When BP falls, JG cells produce, secrete protease renin into arteriole, which leads to increased vasoconstrictor, angiotensin II, increased BP