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Physiology 1 > Functional histology of the kidney > Flashcards

Functional histology of the kidney Flashcards

1
Q

What are the functions of the urinary system?

A

It is involved with the homeostasis of:

  • Plasma composition - by regulated excretion of water, ions and organic waste products into urine.
  • Blood pressure - through the enzyme renin;
  • RBC content - through secretion of erythropoietin.
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2
Q

Describe the structure of the kidney and low power histology section of whole human kidney

A

This is revision from the previous lecture

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3
Q

Describe the structure of what it is seen on a low power histological section of the kidney

A

On image

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4
Q

Describe the parts of the nephron

A
  1. Bowmans capsule
  2. Glomerulus
  3. Proximal convoluted tubule
  4. Loop of Henle - thin arm
  5. Loop of Henle - thick arm
    6 Distal convoluted tubule
    6a Collecting tubule (straighter, epithelium like 7)
  6. Collecting duct
  7. Papilla

Renal corpusule = 1+2
Renal tunile = 3-6a
Nephron = 1-6a

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5
Q

Describe the structures seen as a cross-section of a kidney cortex

A
  1. Renal corpuscle (glomerulus and Bowman’s capsule)
  2. Proximal convoluted tubules
  3. Distal convoluted tubules (paler)
  4. Collecting ducts in medullary ray
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6
Q

Describe the structure of the glomerulus

What can it be seen by?

A
  1. A knot of capillaries

2. Can be seen on an SEM

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7
Q

Look at the structure of the glomerulus and Bowmans capsule

Can it been seen on an SEM and with what magnification?

A

SEM can be used to see them

High magnification

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8
Q

What does P show on the diagram of the glomerulus and Bowmans capsule?

A

showing part of the filter formed by the specialized epithelial cells coating the capillaries, the podocytes (P)

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9
Q

What makes up the first part of the glomerulus filter?

What is the size of these structures?

What can they be seen by?

A
  1. Capillary fenestrations
  2. 50-100nm
  3. SEM
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10
Q

Describe the diagram showing the movement of fluid in ultrafiltration

2nd and 3rd stages of filter: Basement membrane & Podocytes

A

On image

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11
Q

What are the three layers of the glomerular filtrate?

Show these on the diagram

A
  1. The cytoplasm of the capillary endothelial cell of the glomerulus
  2. Thick, fused basement membranes of capillary and podocytes
  3. Filtration slit membranes (with = 4nm pores)
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12
Q

What is the filter cut - off of the glomerular filter?

A

70Kda (albumin)

This size and larger molecules retained in the blood. Many proteins, nutrients (e.g) sugars and ions come through

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13
Q

Describe the views of the 3 layers of the glomerular filtration (3D view)

A

On image

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14
Q

Describe the parts of a podocyte seen on an SEM

A
  1. Podocyte cell body

2. Filtration slits

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15
Q

What can be seen on a Histological section of a normal glomerulus (H&E), “longitudinal”

A

refer to image

A: afferent arteriole
BC: Bowman’s capsule
PC: beginning of proximal convoluted tubule
White = fluid: blood or filtrate.

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16
Q

What is the function of the renal tubule?

A

In short, adjusting composition of ultrafiltrate, to recover nutrients, water etc, and to regulate plasma composition

17
Q

What are the functions of the proximal convoluted tubule?

A

Reabsorption from ultrafiltrate:

  • By active transport across membrane into cell: small molecules like Na+, glucose, amino acids
  • By pinocytosis: macromolecules, especially proteins. These broken down in lysosomes and returned to blood.
  • By passive flux: water, Cl-
18
Q

Describe the structure of the proximal convoluted tubule (PCT) epithelial cell, as seen by TEM

A
  • Long microvilli for high surface area for reabsorption, also lytic enzymes on surface to break down macromolecules
  • Pinocytotic vesicles carrying macromolecules to lysosomes
  • Many lysosomes to break down and recycle macromolecules
  • Many mitochondria to fuel active transport (seen especially near the basolateral sodium pumps)
19
Q

What is the function of the Loop of Henle, thin limb?

A

Reabsorption of water and salts from filtrate - passive flux across epithelium, by osmosis & concentration gradients.

20
Q

Describe the structure of the thin loop of Henle, epithelial cell

A
  • Thin, squamous epithelium to allow passive fluxes

- A minimum of organelles

21
Q

What is the function of the Distal convoluted tubule and thick ascending loop of Henle

A

Homeostasis by regulated active transport & exchange of ions :

(Na+/K+, H+/HCO3-)

22
Q

What is the function of the Collecting duct and collecting tubule?

A

Functions:

  • Transport of urine to ureter.
  • Water homeostasis: passive reabsorption of water, regulated through epithelial permeability
23
Q

Describe the structure of the collecting duct epithelial cell

A

Structure:

  • Cuboidal to columnar epithelium, to prevent passive flux of water (and urea etc)
  • Specialized dense membranes at cell contacts [red].
    Function unclear – probably also helping to prevent passive flux.
24
Q

Describe the Sketch of differential appearance of parts of the renal tubule & collecting ducts

A

On image

25
Q

Describe the structure of the proximal & distal convoluted tubules in cortex - H&E

Describe the structure of the Medulla, section of various tubules

A

On image

26
Q

Have a look at the the juxtaglomerular apparatus (and regulation of blood pressure)

A

This is where the DCT loops back to meet arterioles of same nephron

27
Q

What is the function of the Macula densa?

A

Macula densa - sensing [Na+] in the DCT fluid. Appears to signal to….

28
Q

What is the function of the juxtaglomerular cells?

A

Juxtaglomerular cells - release renin – more so in response to lower [Na+] in DCT. Renin indirectly increases vascular tone and sodium resorption.

29
Q

What is the function of the Lacis cells?

A

Lacis cells – function unknown. (Signalling between the other two?) Also called extraglomerular mesangial cells.

30
Q

Describe the Section showing juxtaglomerular apparatus (H&E)

A

On image

31
Q

Describe the structure of the Ureter (transverse section, Masson’s trichrome, low magnification)

A

On image

32
Q

What is Transitional epithelium?

Where is it found?

How is it specialised?

Describe its structure

A

A special stratified epithelium, found only in ureters and bladder

  • Specialized to be impermeable to urine.
  • Changes appearance on stretching.
  • Somewhat like stratified squamous epithelium when distended,
  • but apical cells are biggest and have much apical cytoplasm.
  • (In stratified squamous epithelium, basal cells are biggest, apical cells very flat.)
33
Q

What is an an oddity?

Describe its structure when distended and contracted

A

Plaques of specialized (urine-resistant) plasma membrane in apical cells of transitional epithelium

On image

34
Q

What is the downside of the transitional epithelium?

A

Cystitis

Why are urinary infections quite common?

Transitional epithelium highly impermeable - leukocytes of immune system cannot readily penetrate.

Why commoner in females?

Female urethra shorter. More risk of contamination, e.g. from anal region.

Advice on prevention?

Plenty of fluids.

Physiology 1 (72 decks)

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