Histology of Kidney Tissue Flashcards

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1
Q

What does the urinary system consist of?

A
  • two kidneys
  • two ureters
  • one bladder
  • one urethra
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2
Q

Explain what happens to urine after it is produced in the kidney

A

It is conducted by the ureters to the bladder where it is stored and leaves the body via the urethra.

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3
Q

Explain the blood supply and drainage to and from the kidney

A

Renal arteries arise from the abdominal aorta. One of more renal veins drain each kidney to the inferior vena cava.

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4
Q

Give and explain the 4 functions of the kidney

A
  • Homeostasis (of water, electrolytes, acid/base)
  • Excretion (of soluble toxic metabolic waste products, particularly nitrogenous urea and creatinine
  • Hormonal (synthesis of renin, synthesis of erythropoietin)
  • Metabolic (vitamin D is converted to active form in kidney)
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5
Q

What are the 3 parts to kidney function?

A
  1. Filtration (of most small molecules from blood plasma to form ultra filtrate of plasma - most negative molecules repelled and do not enter filtrate)
  2. Selective reabsorption (of most water and some molecules from ultra filtrate, leaving behind excess and waste to be excreted)
  3. Secretion (of soluble waste products from blood, and of H+ ions for acid/base balance
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6
Q

Is the filtrate further processed after the kidney?

A

No

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7
Q

Give details on kidney structure

A
  • consists of outer cortex and inner medulla
  • medullary pyramids project into subdivisions of the renal pelvis
  • the renal pelvis narrows as it leaves the kidney to give the ureter
  • the hilum: site of entry and exit of renal blood vessels and ureter
  • the whole kidney is surrounded by a fibrous capsule, which also surrounds the attached adrenal gland (sits ontop of the kidney), also surrounded by a thick layer of fat
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8
Q

How is the kidney organised?

A

A medullary pyramid and its associated cortex forms a lobe.
A human kidney has 10-18 lobes.
The functional unit of a kidney is the nephron.
Kidney donation reflects the way the 10^6 nephrons are arranged.
Accurate and interlobular vessels. The renal artery brings the blood in and then then divides to form the individual filtration units.

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9
Q

What does a nephron consist of?

A

A renal corpuscle and a renal tubule.

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10
Q

What happens in a nephron when the cortex is met again?

A

blood flows into the distal convoluted tubule

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11
Q

What is most of the cortex formed of?

A

The proximal convoluted tubule

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12
Q
Give details on each of these 
Renal corpuscle 
Bowmans capsule
Glomerulus 
Renal tubule
A

rc - plasma filtration, consists of 2 structures
bc - distended, blind end of the renal tubule
g - packed capillaries that invaginate Bowmans capsule derive from the afferent arteriole
rt - reabsorption, extends from Bowmans capsule to the collecting duct, convoluted in shape and has 4 zones (proximal convolutes tubule, loop of henle, distal convoluted tubule, collecting tubule

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13
Q

What does the renal cortex contain?
Tubules make up the vast bulk of the —– between the ——.
What is parenchyma?

A

Renal corpuscles

parenchyma, corpuscles

Surrounding tissue of the tubules

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14
Q

Explain the movement of the afferent and efferent arterioles

A

Wide afferent arteriole enters the Bowmans Capsule at the vascular pole, branches to form a network of capillaries.
Efferent arterioles is smaller in diameter, so to maintain a pressure gradient that drives filtration of plasma into Bowmans space

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15
Q

What do parietal cells do?

Where do podocytes sit?

A

Surround the Bowmans capsule

On the outside of the Bowmans capsule

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16
Q

What is the purpose of a mesangial cell?

A

They are phagocytic. They pick up dead matter such as if you had kidney damage or an infection.

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17
Q

What are the 3 layers which the filtrate must pass through before entering the renal tubule? Give some details

A
  1. Capillary endothelium (fenestrated)
  2. Glomerular basement membrane (thick as formed by 2 basal laminae of podocytes and endothelia. contains type 4 collagen
  3. Between the podocytes lining the capsule (indigitating pedicels). Gaps between pedicles are filtration slits
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18
Q

Give information about what would be seen under EM microscope of the podocyte filter

A

Primary and secondary pedicels resemble octopus tentacles that completely cover the endothelia. These create very small spaces.

Cells are flat with large bulging nuclei. Each podocyte has several long primary processes that can cover more than one capillary.
At greater magnification, the secondary pedicles can be seen as lateral extensions of the primary processes.

19
Q

What gives rise to regularly spaced filtration slits of uniform width?

A

Interdigitation of processes

20
Q

Why is there a darkening seen under the microscope where the pedicles come together?

A

A collection of proteins with a negative charge.

21
Q

Give details on the proximal convolted tubule

A

Longest part of the renal tubule. Approximately 75% of filtrate is reabsorbed at the PCT. Simple tall columnar epithelium with large brush border (BB) of tall microvilli. Many capillaries (C) arise from efferent arteriole - receive molecules reabsorbed by PCT.

22
Q

Where does material which is reabsorbed go?

A

Taken into capillaries which filter into the renal vein

23
Q

What does the EM of PCT show?

A

EM reveals microvilli (Mv), many vesicles (M) and lysosomes (L). Capillaries (Cap) under the basal lamella (BM) take the reabsorbed solutes after transport accords the epithelial cells.

Many lysosomes because the cell is also phagocytic taking up particulate matter that gets though the kidney filter.

24
Q

Which loop of henle is the thin loop?

What happens here?

A

The descending limb and a small amount of the ascending limb.
This is so water can leave the filtrate passively.

25
Q

What makes the ascending loop thicker?

Which limb is shorter?

A

It has more columnar cells

Thin ascending limb

26
Q

Give details on where the loop of Henle is

A

Arises in cortex, dips into medulla (descending limb), returns to cortex as ascending limb

27
Q

Where is the distal convoluted tubule found?
What occurs here?
Explain the cell histology

A

Found in the cortex
Reabsoprtion of sodium ions from tubule lumen (aldosterone control)
Simple cuboidal epithelium, no brush border, many mitochondria

28
Q

Explain the juxtaglomerular apparatus

A

It is a specialisation of the afferent arteriole and the DCT of the same nephron. Regulates blood pressure via renin-angiotensin-aldosterone system.

29
Q

What is the macula densa?

A

An area of large closely packed tall epithelial cells - DCT adjacent to the juxtaglomerular apparatus. These cells are sensitive to the ionic composition and the blood pressure.

30
Q

What are Lacis cells derived from and what do they secrete?

A

Derived from mesangial cells and secrete erythopoietin

31
Q

What are proximal collecting tubules and distal collecting tubules lined by?

A

Proximal - mixture of DCT cells and collecting tubule cells

Distal - principal cells with interspersed intercalated cells

32
Q

Give histology and role of principal cells and intercalated cells

A

Principal - pale cytoplasm, scanty organelles, short microvilli. Actively reabsorbs Na+ and secretes K+.

Intercalated - darker cytoplasm, mitochondria, polyribosomes and vesivles. Important for acid-bases homeostasis as secretes H+ and reabsorbs K+ and HCO3-

33
Q

Where do collecting tubules extend from?

What do several collecting tubules converge to form?

A

The DCT.

Collecting ducts

34
Q

Urine is concentrated by passive —– of water into medullary —– following the —– gradient created by the counter current —– systems of loops of Henle. This is controlled by —–

A

Reabsorption
Interstitium
Osmotic
Multiplier

ADH

35
Q

What are the ducts called which are formed from collecting ducts and drain urine from tip of renal papilla into renal pelvis?

A

Ducts of Bellini

36
Q

Give details on the renal papilla

A

Forms the apex of the medullary pyramid; projects into the proximal renal pelvis or pelivicalceal space.
Ducts of Bellini converge to drain urine at the tip of the papilla.

37
Q

What is the pelvicalceal space lined with?

A

Transitional epithelium

38
Q

What is the ureter?

A

A muscular tube that connects urine from the kidney to the bladder. This is a passive process.
Urine moved by peristaltic action of ureteric wall.

39
Q

Explain the smooth msucle in the ureter?

What is the lumen of the ureter lined with?

A

Two layers of smooth muscle.
Longitudinal inner layer and circular outer layer.

Lumen of ureter is lined with transitional epithelium, with deeps lamina propriety rich in collagen (LP).

40
Q

Urinary (transitional) epithelium

Where is it found?
What type of epithelium is it?
Give any more details

A

Found within the conducting passages of the urinary system.

It is stratified epithelium. It is only squamous when it is distended (swollen).

Cytoplasm consists of thick iflexible plaques with narrow zones of normal membrane.
It leads to much folding and formation of deep clefts of fusiform vesicle - renders epithelium impermeable to urine.

41
Q

How many smooth muscle layers does the bladder have?

What are each of these?

A

3 layers.

Inner longitudinal layer, outer circular and outermost longitudinal.

42
Q

Explain the countercurrent multiplier mechanism

A

Loop of Henle - produces an increasing osmotic gradient from the cortex to the tip of the renal papilla.
Active transport of sodium and chloride ions into the medullary interstitium by the ascending thin limb, which is impermeable to water.

Think descending limb contains water and ions from PCT at low osmotic concentration. Epithelial lining is freely permeable.

43
Q

The juxtaglomerular cells monitor blood pressure. Explain it does so.

A

Reduced blood pressure means reduced filtration and a lower concentration of sodium ions in DCT. Cells of mucula densa sense this and promote renin secretion.

Renin in bloodstream catalyses conversion of plasma angiotensinogen to angiotension 1. This constrict blood vessels and promotes release of aldosterone from adrenal cortex.