Kidney Histology Flashcards
(98 cards)
1
Q
What organ produces urine?
A
Kidneys
2
Q
What structures conduct urine to the bladder?
A
Ureters
3
Q
By what structure is the urine voided from the bladder?
A
Urethra
4
Q
Describe the blood supply to the kidneys
A
Renal arteries arise from abdominal aorta
One or more renal veins drain each kidney to the inferior vena cava
5
Q
What are the 4 general functions of the kidneys?
A
Homeostasis of water, electrolytes and acid/base
Excretion of soluble toxic metabolic waste products
Hormonal
Vitamin D converted to active form
6
Q
Which hormones are synthesised by the kidney?
A
Renin
Erythropoietin
7
Q
What main outcome does renin secretion have?
A
Increase in blood pressure
8
Q
What main outcome does erythropoietin secretion have?
A
Increase oxygen carrying capacity of blood
9
Q
What are the three general stages of kidney function?
A
Filtration
Selective reabsorption
Secretion
10
Q
How many times is the total blood volume circulated through the kidneys per day?
A
~300
11
Q
What is the rate of formation of glomerular filtrate?
A
~120ml/min
12
Q
What is the rate of formation of urine?
A
~1ml/min
13
Q
What is the outer region of the kidney called?
A
Cortex
14
Q
What is the inner region of the kidney called?
A
Medulla
15
Q
What is the hilum?
A
Site of entry/exit of blood vessels and ureter
16
Q
Describe the general/gross structure of the kidney
A
Surrounded by fibrous capsule (and a thick layer of fat) which includes the adrenal glands
Medullary pyramids project into calyces/subdivisions of the renal pelvis
17
Q
What is a lobe?
A
Medullary pyramid and its associated cortex
18
Q
How many lobes are there in a human kidney?
A
10-18
19
Q
What is the functional unit of the kidney?
A
Nephron
20
Q
How are the arteries arranged within a kidney?
A
Renal artery branches into interlobar arteries the arcuate arteries then interlobular arteries
21
Q
Where are interlobar arteries found?
A
Between lobes/pyramids
22
Q
Where are arcuate arteries found?
A
At the border between the cortex and medulla
23
Q
Where are the renal corpuscles found?
A
Cortex
24
Q
What are the flattened epithelial cells lining Bowman’s capsule called?
A
Parietal cells
25
What is the glomerulus?
Packed capillaries which invaginate Bowman's capsule
26
What is Bowman's capsule?
Distended, blind end of renal tubule
27
What blood vessel supplies the glomerulus?
Afferent arteriole
28
What occurs at the renal corpuscle?
Plasma/glomerular filtration
29
What occurs at the renal tubule?
Reabsorption
Secretion
30
What are the four main zones of the renal tubule (after filtration)?
Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
Collecting tubule/duct
31
In what part of the kidney is the majority of the loop of Henle found?
Medulla
32
What is the longest part of the renal tubule?
Proximal convoluted tubule
33
What makes up the vast bulk of parenchyma between renal corpuscles?
Tubules (mostly PCT)
34
Where do the arterioles enter/exit Bowman's capsule?
Vascular pole
35
Which the afferent or efferent arterioles have a wider diameter?
Afferent
36
Why does the efferent arteriole have a smaller diameter than the afferent arteriole?
Maintain pressure gradient to drive plasma filtration
37
How many layers must the plasma filtrate pass through before entering Bowman's space?
3
38
What are the three layers of the glomerular filter?
Fenestrated capillary endothelium
Glomerular basement membrane
Podocytes
39
How thick is the glomerular basement membrane?
300nm
40
What is the glomerular basement membrane formed from?
Basal laminae of podocytes and endothelium
41
What is the normal composition of the glomerular basement membrane?
Collagen IV
Laminin
Proteoglycan rich in heparin sulphate
42
What is the charge of the glomerular basement membrane and how does this affect filtration?
(Proteins =) negative
Repels negatively charged molecules
43
What are filtration slits?
Gaps between interdigitating pedicels of podocytes
44
Describe a podocyte
Large, bulging nucleus with pale cytoplasm
Primary processes cover more than one capillary each
Secondary processes branch off and interdigitate to produce filtration slits
45
How wide are filtration slits?
25nm
46
Why do the edges of podocyte processes (next to filtration slits) appear dark in TEM?
Protein accumulations
To repel negatively charged molecules
47
How much of the filtrate is reabsorbed at the PCT?
~75%
48
Describe how the PCT would appear under a light microscope
Simple tall columnar (may be cuboidal) with brush border
Infolds on basal membrane
Darkly-staining cytoplasm (with vesicles and lysosomes)
Small/indistinct lumen
49
Why does the PCT epithelium have tall microvilli?
Increase surface area for reabsorption
50
Why are the cells lining the PCT darkly-staining?
Packed with mitochondria
51
What does pars recta mean?
Straight part
52
What is the pars recta of the PCT?
Thick descending limb
53
How does the epithelium relate to the function of the thin descending limb?
Squamous
Little resistance to water reabsorption
54
How does the epithelium relate to the function of the thick ascending limb?
Cuboidal
Prevents passage of water
Pumps sodium ions to create gradients
55
What is the main difference between the thick ascending limb and the collecting tubules (on a histological slide)?
Collecting tubules have wider diameters
56
What is the name given to the capillaries surrounding the loop of Henle?
Vasa recta
57
Describe the epithelium and lumen of the collecting ducts
Pale-staining, tall columnar epithelium
Wide lumen
58
Describe the direction in which blood flows in the vasa recta
Down the ascending limb
Up the descending limb
59
Why does blood in the vasa recta flow in the opposite direction to the loop of Henle?
Maintain counter current multiplier effect
60
What is the main function of the loop of Henle?
Generate the counter current multiplier by diluting the urine/pumping sodium ions into the interstitium
61
In what region of the kidney is the distal convoluted tubule found?
Cortex
62
Describe the epithelium lining the DCT
Simple cuboidal (no brush border)
Darkly staining as packed with mitochondria
63
How can you tell the difference between PCT and DCT on a histological slide?
DCT has a distinct lumen due to lack of tall brush border
64
What is the juxtaglomerular apparatus?
Specialisation of the afferent arteriole and DCT of the same nephron
65
In which part of the renal tubule is the macula densa found?
DCT
66
What is the macula densa?
Area of DCT with large, closely-packed tall epithelial cells
67
What are juxtaglomerular cells and where are they found?
Specialised smooth muscle cells
Adjacent to glomerulus in afferent arteriole wall
68
What are Lacis cells derived from and what is their function?
Derived from mesangial cells
Erythropoietin synthesis and secretion
69
What is the function of mesangial cells?
Phagocytic
70
Is the cytoplasm of mesangial cells pale or dark staining?
Dark
71
How does the juxtaglomerular apparatus regulate blood pressure?
Macula densa is sensitive to the ionic composition of blood and blood pressure
Causes juxtaglomerular cells to change smooth muscle tone and the release/inhibition of renin
72
What is the function of the juxtaglomerular apparatus?
Regulate blood pressure via the renin-angiotensin-aldosterone system
73
What cells contain and secrete renin?
Juxtaglomerular cells
74
What types of cells line the distal COLLECTING tubule?
Mainly principal cells with interspersed intercalated cells
75
What do principal cells look like?
Pale cytoplasm
Scanty organelles
Short microvilli
76
What are the main functions of principal cells?
Actively reabsorb sodium and secrete potassium
ADH-dependent water reabsorption
77
What do intercalated cells look like?
Dark cytoplasm
Due to many organelles (mitochondria, polyribosomes, vesicles)
78
What are the main functions of the intercalated cells?
Secrete H+
Reabsorb bicarbonate and potassium
79
Describe the epithelium lining the distal collecting tubule
Simple cuboidal epithelium
Becomes increasingly tall distally as it merges with columnar epithelium of collecting duct
80
What controls water reabsorption in the collecting duct?
ADH/vasopressin
81
What do Ferrein's pyramids consist of?
Medullary rays (collecting ducts) descending towards the renal medulla
82
What are ducts of Bellini?
Large diameter ducts resulting from the convergence of several collecting ducts
83
What is the renal papilla?
Apex of a medullary pyramid which projects into the pelvicalyceal space (proximal renal pelvis)
84
Where do ducts of Bellini converge?
Tip of renal papilla
85
What type of epithelium lines the pelvicalyceal space?
Transitional epithelium
86
What is a ureter?
Muscular tube which conducts urine from the kidney to the bladder via peristaltic action
87
How many layers of smooth muscle are in the ureter wall?
2
88
Describe the muscle arrangement of the ureter
Longitudinal - inner layer, elongated spiral
Circular - outer layer, tight spiral
89
State the layers of the wall of a ureter
Transitional epithelium
Deep lamina propria rich in collagen
Muscle layers (longitudinal then circular)
Adventitia
90
Where is transitional epithelium found?
Conducting passages of urinary system
91
Describe transitional epithelium (4)
Stratified, greatest number of layers when not distended
Squamous only when distended (all cells have the same shape)
Superficial cytoplasm is heavily stained and indistinct
Lots of folding and formation of deep clefts of fusiform vesicles
92
Why is the superficial cytoplasm of transitional epithelium heavily stained?
Consists of thick, inflexible 'plaques' with narrow zones of normal membrane between which act as hinges
93
What is the function of the folding and formation of deep clefts of fusiform vesicles in transitional epithelium?
Makes epithelium impermeable to toxic urine
94
How many layers of smooth muscle are in the wall of the bladder?
3
95
What are the smooth muscle layers of the bladder?
Inner longitudinal
Outer circular
Outermost longitudinal
96
What does the adventitia of the bladder contain?
Arteries, veins and lymphatics
97
How does the bladder contract (direction)?
Top to bottom
98
What must be open to allow the bladder to be emptied?
Sphincter
