Histology

Question 1

What are the 4 functions of the kidney?

Answer 1

1. Filter the blood (to remove waste as urine)
2. Regulate water, salt, acid-base balance (homeostatic control of body fluids)
3. Regulate blood pressure
4. Produce hormones/enzymes (erythropoeiten, renin angiotensin, vitamin D)

Question 2

What is the smallest functional unit of the kidney?

Answer 2

The nephron

Question 3

The nephron:
Where is it found?
Number per kidney?
Where does it drain to?

Answer 3

Found in cortex and medulla of kidney
1 million per kidney
Filtration and transportation

Question 4

The nephron:

What is it comprised of?

Answer 4

1. Renal corpuscle (capillary tuft enveloped by the tubule).

2. Proximal, thin, and distal tubules (each further subdivided)

Question 5

Name the 9 sections of the nephron, in order?

Answer 5

1. Renal corpuscle (glomerulus capillary tuft)
2. Proximal convoluted tubule (squiggly)
3. Proximal straight tubule
4. Thin descending limb
5. Thin ascending limb
6. Thick ascending limb
7. Distal convoluted tubule
8. Connecting tubule
9. Collecting duct

Question 6

Name the 4 sections that make up the “Loop of Henle”, in order?

Answer 6

1. Proximal straight tubule
2. Thin descending limb
3. Thin ascending limb
4. Thick ascending limb

Question 7

Name 5 the functions of the nephron, in order?

Answer 7

1. Filtration
2. Reabsorption
3. Water extraction
4. Salt fine tuning
5. Regulation

Question 8

What occurs on the renal corpuscle?

Answer 8

Blood filtration

Mass filtration including - glucose, ions, but not blood cells or proteins.

Question 9

What occurs in the proximal tubules (convoluted and straight)?

Answer 9

Reabsorption

65% of filtrate volume is reabsorbed - removing what should be kept and allowing waste to remain.

Question 10

What occurs in the thin (descending and ascending) and thick ascending limbs?

Answer 10

Water extraction

Question 11

What occurs in the distal convoluted tubule?

Answer 11

Salt fine tuning and pH regulation

Question 12

What occurs in the collecting duct?

Answer 12

Reabsorption of H2O

Question 13

Describe the structure of the renal corpuscle (glomerulus)?

Answer 13

1. Capillary tuft
2. Surrounded by epithelial cells (podocytes and parietal epithelial cells)
3. Podocytes envelope the capillaries
4. Parietal epithelial cells form the outside layer - squamous epithelium (inside layer of Bowman’s capsule)

Question 14

Name the 6 components/areas of the renal corpuscle.

Answer 14

1. Afferent arteriole
2. Vascular pole (pole of the capsule that’s vascular)
3. Podocytes on capillary tuft
4. Parietal epithelium on outside layer (inside later of Bowman’s capsule)
5. Urinary space
6. Urinary pole
   Then the proximal tubule

Question 15

Describe conceptually how embryonic development of the renal corpuscle occurs.

Answer 15

1. The developing glomerulus with afferent and efferent ends is like a bundle of wool on its own.
2. Bowmans capsule is invaginated by glomerulus.
3. Cells on capillaries turn in to podocytes.
4. Cells on the inside of Bowman’s capsule (against the glomerulus) turn in to parietal epithelial cells.

Question 16

What is the glomerular filtration barrier, identify 3?

Answer 16

1. Physical barrier
2. Charge-selective barrier
3. Restricts cells, albumin (most abundant proteins in plasma) and other large proteins

Question 17

Identify the three major components of the glomerular filtration barrier.

Answer 17

1. Endothelium - fenestrated glomerular capillary
2. Basement membrane - Glomerular basement membrane
3. Podocytes - filtration slits

Question 18

Describe the first glomerular filtration barrier, endothelium (fenestrated glomerular capillary).

Answer 18

1. Holes (that are permeable to small molecules, but restricts cells).
2. Negatively charged glycocalyx coat (repels proteins in the plasma, most of which are negatively charged.

Question 19

Describe the second glomerular filtration barrier, glomerular basement membrane.

Answer 19

1. Thick
2. Made up of collagen and negatively charged proteoglycans
3. Has a dense core and less dense outer laters
4. Acts as a physical (inner layer) and charge barrier (outer layers)

Question 20

Describe the third glomerular filtration barrier, podocytes (filtration slits)

Answer 20

1. Adhere to the glomerular filtration barrier
2. Primary and secondary processes that interdigitate
3. Form slits linked by a protein bridge (slit membrane)
4. Covered in a negatively charged glycocalyx coat.

Question 21

Describe the slit membrane

Answer 21

1. Fine filter

2. Covered in glycocalyx coat (negatively charged)

Question 22

Recap - the glomerular filtration barrier.

Answer 22

1. Endothelium glycocalyx (-ve charge)
2. Less dense (-), Dense (physical), Less dense (-)
3. Slit diaphragm (protein bridge)
4. Podocyte glycocalyx (-ve charge)
5. Urinary space

Question 23

Discuss podocyte effacement.

Answer 23

1. Podocytes (octopus cells) are interdigitated units, with a foot process architecture.
2. Effacement is a common pathological feature of glomerular disease where there is no digitation, and it areas appear flattened.
3. Can develop in diuretic neuropathy and severe inflammatory conditions.

Question 24

Discuss the function of podocytes and then the issues associated with effacement.

Answer 24

Podocytes provide a squeezing force on the basal membrane, compressing the filtrate into a ell and acting like a filter.
Without the foot structures you don’t get the filter compression/gel substance.

Question 25

What is the main function of mesangial cells?

Answer 25

Mesangial Man :) | Maintain structure of the capillary tuft.

Question 26

What are mesangial cells, 4 points?

Answer 26

1. Smooth muscle cells packed inside capillary tuft. 2. Supportive/contractile role (maintain tuft shape). 3. Produce extracellular matrix 4. Involved in glomerulosclerosis (glomerular scarring)

Question 27

What occurs when gloremurular are damaged?

Answer 27

In and effort to repair the mesangial cell proliferate and extracellular matrix is deposited - resulting in the formation of scars. Stage 1. Focal segmental glomerulosclerosis Stage 2. Diabetic nephropathy

Question 28

Where is the juxtaglomerular apparatus located?

Answer 28

Thick ascending limb - adjacent to of Bowmans capsule in between the afferent and efferent arterioles.

Question 29

What does the juxtaglomerular apparatus include?

Answer 29

1. JG cells 2. Macular dense cells. 3. Extraglomerular mesangial cells.

Question 30

What are the juxtaglomerular cells?

Answer 30

Modified smooth muscle cells in the wall of afferent arterioles that secrete renin.

Question 31

What are macular dense cells?

Answer 31

Special cells in the wall of the thick ascending limb the sense salt concentration in the filtrate.

Question 32

What are the two major regulatory functions performed by the juxtaglomerular apparatus?

Answer 32

Structural piece that helps nephron regulate its flow by sampling the salt that flows through. * If NaCl (salt) concentration is high in distal tubules then vasoconstriction occurs in afferent arterioles * If NaCl (salt) concentration is low > renin is induced > promotes production of angiotensin > increasing blood pressure > more blood through glomerular.

Question 33

What are the features of the proximal tubule cells: bulk reabsorption?

Answer 33

1. Cuboidal epithelium 2. Prominent brush border (microvilli) on apical surface to increase surface area for transporters. 3. Vesicles (pinocytosis) for uptake of droplets with macromolecules eg. proteins. 4. Lateral processes and inholdings (interdigitation) to increase surface area.

Question 34

What are the main features of the thin limb cells? | very difficult to see in the lab because they are so thin

Answer 34

1. Thin squamous epithelium 2. Role in water reabsorption as part of the Loop of Henle 3. Nuclei bulge into the lumen

Question 35

What are the main features of the distal tubule cells?

Answer 35

1. Cuboidal 2. Interdigitating lateral processes and in-foldings (like proximal tubule cells) 3. No brush border (short microvilli instead) 4. No pinocytosis

Question 36

What are the functions of the distal tubule?

Answer 36

1. Fine tuning salt and pH balance (distal convoluted tubule, and connecting tubule). 2. Urine concentration (thick ascending limb).

Question 37

What are the main features of the collecting duct?

Answer 37

1. Cuboidal and columnar epithelium

Question 38

What are the main functions of the collected duct?

Answer 38

Final modifier of water, salt, and pH of the urine.

Question 39

Describe the higher organisation of the kidney, 3 points.

Answer 39

1. Contained within the renal capsule 2. Made up of lobes (which contain lobules) 3. Divided into cortex and medulla

Question 40

Describe the higher organisation of the cortex?

Answer 40

1. Cortex contains lobules. 2. Lobules encase the medullary rays. 3. The cortex is the location of renal corpuscles and portions of the proximal and distal tubules.

Question 41

What are medullary rays?

Answer 41

Straight bundles within lobules containing collecting duct and proximal and distal tubules going to and from the medulla.

Question 42

Describe the higher organisation of the medulla?

Answer 42

1. Medulla = conical structures called medullary pyramids 2. Apex of medullary pyramid = renal papillae 3. Papilla with slits enveloped by calyces 4. The medulla is the location of the collecting ducts and Loop of Henle. 5. Collecting ducts fuse to form large ducts that open at the renal papillae.

Question 43

What is the pathway of blood into the kidney?

Answer 43

1. Renal artery 2. Interlobar artery 3. Arcuate artery (crosses from medulla to cortex) 4. Interlobular artery 5. Afferent arteriole 6. Glomerulus - capillary tuft

Question 44

What is the pathway of blood out of the kidney?

Answer 44

1. Interlobular vein 2. Arcuate vein 3. Interlobar vein 4. Renal vein

Question 45

Where are the vasa recta located?

Answer 45

Located in medulla along side interlobar vessels.

Question 46

What is the function of the vasa recta?

Answer 46

Maintain salt levels in medulla.

Question 47

What are the main features of the cells within the ureter and bladder?

Answer 47

1. Transitional epithelium - for expansion and contraction. 2. Mucous membrane - for lubrication, protection from urine and pathogens. 3. Sub-epithelial connective tissue's/lamina propria (elastic. 4. Smooth muscle layers (contractile; inner longitudinal and outer circular). 5. Outside later of adventitia (elastic and harbours blood supply.

Question 48

What is the epithelial cell features of the urethra?

Answer 48

Initially lined by transitional epithelium > stratified columnar > stratified squamous