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Block E -- Renal > Histology Lecture 1 -- Kidney and Urinary System > Flashcards

Histology Lecture 1 -- Kidney and Urinary System Flashcards

1
Q

Structures that leave or enter the kidney at the hilum

A

Branches of the:

  • Renal arter yand vein
  • Lymph vessels
  • Ureter
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2
Q

Define the renal pelvis

A

Expanded ureter at the level of the hilum of the kidney

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3
Q

What does the kidney parenchyma surround

A

Renal sinus

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4
Q

Describe the appearance of the cortex and medulla of the kidney in fresh tissue

A
  • Cortex = granular and dark brown
  • Medulla = lighter and striated
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5
Q

Components of the medulla

A

6 - 12 pyramid-shaped regions = renal pyramids

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6
Q

Define the renal papilla

A

Apex of each renal pyramid bulging into the renal sinus

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7
Q

What perforated the renal papilla?

A

Approximately 20 openings of the ducts of Bellini (area cribosa)

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8
Q

Define the tissue between the renal pyramids. Are they part of the medulla or the cortex?

A

Cortical columns / Columns of Bertin

Part of the medulla (even though they are extensions of cortical tissue)

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9
Q

What covers each renal papilla

A

Minor calyx

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10
Q

What forms a major calyx?

A

2 to 3 adjacent minor calyces that fuse

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11
Q

Where do major calyces open into?

A

The renal pelvis

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12
Q

3 types of structures that can be observed in the cortex

A
  • Renal corpuscles
  • Convoluted tubules and longitudinal striations
  • Medullary rays
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13
Q

How many lobes in a rat kidney?

A

1

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14
Q

Define a kidney lobe

A

One renal pyramid and its surrounding cortical tissue

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15
Q

Define a kidney lobule

A

One medullary ray and surrounding area of convoluted tubules and renal corpuscles

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16
Q

Define the uriniferous tubule

A

The functional unit of the kidney

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17
Q

2 parts of the uriniferous tubule and how they are differentiated

A
  • Nephron
  • Collecting tubule

Differentiated by different embryological origins

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18
Q

Number of nephrons per kidney

A

1 - 4 million

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19
Q

2 types of nephron

A
  • Cortical
  • Juxtamedullary
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20
Q

3 characteristics of cortical nephrons

A
  • Located in the cortex
  • Short
  • Short loops of Henle
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21
Q

3 characteristics of the juxtamedullary nephron

A
  • Located close to the medulla
  • Very long loops of Henle that penetrate the medulla
  • About 40 mm long
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22
Q

4 components of the nephron

A
  • Renal corpuscle
  • Proximal convoluted tubule
  • Loop of Henle
  • Distal convoluted tubule
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23
Q

Diameter of renal corpuscle

A

200 micrometers

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24
Q

2 components of the renal corpuscle

A
  • Glomerulus
  • Bowman’s capsule
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25
Q

2 epithelial layers of the Bowman’s capsule and their cell types

A
  • Visceral = podocytes
  • Parietal layer = simple squamous
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26
Q

Space between the two epithelial layers of the Bowman’s capsule

A

Urinary space / capsular space/ Bowman’s space

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27
Q

2 poles of the renal corpuscle

A
  • Vascular pole (afferent arteriole enters glomerulus and efferent arteriole leaves)
  • Urinary [ole (beginning of PCT)
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28
Q

Where does the parietal epithelium of the Bowman’s capsule change cell type and to what type does it change?

A
  • At the urinary pole
  • Changes to simple columnar epithelium
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29
Q

3 structural components of podocytes

A
  • Cell body
  • Several primary processes
  • Abundant secondary processes (pedicels)
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30
Q

2 characteristics of pedicels

A
  • Embrace the capillary loops of the glomerulus
  • Interdigitate with pedicels from adjacent podocytes to form filtration slits
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31
Q

Width of filtration slits

A

25 nm

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32
Q

What bridges the filtration slits

A

A very thin (about 6 nm) diaphragm

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33
Q

Only part of the podocyte that touches the basement membrane of the capillaries

A

Pedicels

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34
Q

4 characteristics of podocyte cell bodies

A
  • Numerous free ribosomes
  • A few cisternae of rER
  • Prominent Golgi
  • Very few mitochondria
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35
Q

2 characteristics of the processes of podocytes

A
  • Very few organelles
  • Contains actin filaments for contractility
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36
Q

3 characteristics of the epithelial layer of the glomerular capillaries

A
  • Fenestrated
  • Bigger fenestra (70 - 90 nm in diameter) than in similar capillaries in other organs
  • No diaphragm (also in contrast to others)
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37
Q

Define the filtration barrier separating the blood from the urinary space

A

Thick basement membrane derived from the fusion of the basal laminas from podocytes and endothelial cells

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38
Q

4 components of the glomerular basement membrane

A
  • Type IV collagen
  • Laminin
  • Fibronectin
  • Proteoglycans rich in heparan sulfate
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39
Q

2 groups of mesangial cells and their locations

A
  • Extraglomerular mesangial cells (vascular pole)
  • Intraglomerular cells (in between capillary loops inside the glomerulus)
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40
Q

3 functions of the intraglomerular mesangial cells

A
  • Likely phagocytic (involved in digestion of basement membrane)
  • May be contractile (contribute to reduced blood flow in glomerulus)
  • Support capillary loops in regions where podocytes are not in contact with them
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41
Q

Size of molecules that are trapped by the basement membrane

A

> 69 kDa (i.e. albumin)

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42
Q

Charge of molecuels prevented from crossing the basement membrane and how

A

Negatively charged molecules due to anions in the basement membrane

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43
Q

Define the glomerular ultrafiltrate

A

Fluid that enters the capsular (or urinary) space

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44
Q

How does the glomerulus prevent the clogging of the basement membrane by large trapped molecules?

A
  • Continuous renewal through phagocytosis by mesangial cells
  • De novo synthesis by podocytes and endothelial cells
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45
Q

Epithelium type of the PCT

A
  • Simple cuboidal to columnar epithelium
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46
Q

4 histological characteristics of the PCT

A
  • Highly acidophilic (numerous elongated mitochondria)
  • Brush border (numerous elongated microvilli)
  • Cells larger than those of DCT
  • Indistinct cell membrane limits (extensive interdigitations of membranes)
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47
Q

4 ultrastructural characteristics of the PCT

A
  • Numeroud endocytic structures in apical cytoplasm between bases of microvilli
  • Basal parts have muiltiple membrane invaginations and laterla interdigitations with adjacent cells
  • Parallel mitochondria to long axis
  • Na-K-ATPase at basolateral membrane
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48
Q

3 parts of the loop of Henle

A
  • Thick straight descending limb
  • Thin limb
  • Thick straight ascending limb
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49
Q

Type of epithelium at the thin limb

A

Squamous

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50
Q

Importance of juxtamedullary nephrons

A

Unique capability of contributing (with the blood vessel loops) to the establishment of the gradient of hypertonicity in the medulla required for urine concentration (counter-current exchange system)

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51
Q

Part of the loop of henle that is permeable to water

A

Thin descending limb

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52
Q

Part of the loop of henle that is impermeable to water

A

Entire ascending limb (both thick and thin)

53
Q

Epithelium type of distal convoluted tubule

A

Simple cuboidal epithelium without microvilli

54
Q

5 differences between the DCT and PCT histologically

A
  • DCT cells are smaller and flatter
  • DCT lumens are larger and normally appear wide open
  • DCT has no brush border
  • DCT cells are less acidophilic
  • DCT have more cells (more nuclei close to apical border)
55
Q

Define the macula densa

A

Elongated epithelial cells with crowded nuclei of the DCT where it contacts the vascular pole of the bowman’s capsule of its parent nephron

56
Q

Function of PCT

A

Reabsorption of 85% of water, solutes, and proteins

57
Q

Describe water reabsorption in the PCT

A
  • Apical membrane = passive
  • Basolateral = active resorption via Na/K/ATPase pump
58
Q

Describe generally how solutes are reabsorbed in the PCT

A

Isotonically –> osmotic potential of the fluid leaving the PCT = that of the initial glomerular filtrate

59
Q

Function of DCT

A

Partly responsible for the regulation of K+, Ca++, Na+ and pH

60
Q

Primary site for the kidney’s hormone-based regulation of Ca++

A

DCT

61
Q

2 carriers in the luminal membrane of the DCT

A
  • Na+/Cl- co-transporter (symporter)
  • Calcium-selective channel
62
Q

3 carriers in the basolateral membrane of the DCT

A
  • ATP dependent Na+/K+ antiport pump
  • Active Na+/Ca++ transporter antiport
  • ATP dependent Ca transporter
63
Q

Describe the function of the DCT’s basolateral transporters

A
  • Na+/K+ ATP dependent pump produces Na+ gradient
  • Na+ absorbed from the apical surface via the Na/Cl symporter
  • Gradient allows Ca++ to be reclaimed into the blood by the Na/Ca antiport
64
Q

Describe how the DCT regulates pH

A
  • Absorb bicarbonate and secrete protons into the filtrate

OR

  • Absorb protons and secrete bicarbonate into the filtrate
65
Q

Describe how the DCT controls sodium and potassium levels

A
  • K+ secretion
  • Na+ absorption
66
Q

What mediates sodium absorption by the DCT?

A

Aldosterone (increases Na+ absorption)

67
Q

What kind of vasopressin receptor is expressed in the DCT and its effect

A
  • Arginine vasopressin receptor 2
  • Increases permeability to water in the presence of ADH (normally pretty impermeable) –> concentration of urine
68
Q

3 components of the juxtaglomerular apparatus

A
  • Macula dense of the DCT
  • Juxtaglomerular cells of the afferent arteriole
  • Extraglomerular mesangial cells
69
Q

Define juxtaglomerular cells

A

Modified smooth muscle cells of the tunica media of the afferent arteriole

70
Q

3 characteristics of the juxtaglomerular cells

A
  • Round nuclei (not elongated)
  • Cytoplasm rich in granules containing renin
  • Basal lamina absent at the level of contact with the macula densa
71
Q

4 boundaries of the space that the extraglomerular mesangial cells occupy

A
  • Afferent arteriole
  • Macula densa
  • Efferent arteriole
  • Vascular pole of Bowman’s capsule
72
Q

2 hormones secretes by the juxtaglomerular cells

A
  • Renin
  • Erythropoietin (probably; in response to hypoxia)
73
Q

Functions of the macula densa

A
  • Production of nitric oxide –> counteract angiotensin II-mediated contraction of the A.A. –> increase ultrafiltration
  • Promotion of renin release in response to ionic content and water volume of the tubular fluid
74
Q

Describe the epithelium cell type and diameter of the collecting tubules and ducts

A
  • Small collecting tubuels = cuboidal epithelium (40 - 50 µm diameter)
  • Collecting ducts = columnar epithelium (increased diameter)
  • Ducts of Bellini reach 200 µm at the tip of the pyramids
75
Q

3 common features of all collecting tubules and ducts

A
  • Cytoplasm stains weakly in routine preps
  • No microvilli
  • Cell limits are easy to see
76
Q

Where in the nephron is creatinine secreted?

A

Proximal tubule

77
Q

Site of ADH action

A

Collecting duct

78
Q

Give the order of the vessels of the kidney starting from the renal artery

A
  • Renal artery
  • Anterior and posterior branches of renal artery
  • Interlobar arteries
  • Arcuate arteries
  • Lobular arteries
  • Afferent arterioles
  • Glomerular capillaries
  • Efferent arteriole
  • Peritubular capillary network of cortical tubules OR vasa rectae
  • Stellate veins
  • Interlobular veins
  • Arcuate veins (also receive blood from venae rectae)
  • Interlobar veins
  • Renal vein
79
Q

Where are the interlobar arteries located?

A

Renal columns of Bertin

80
Q

Where are arcuate arteries formed?

A

At the level of the cortico-medullary junction

81
Q

What forms the outer limits of the lobules?

A

Lobular arteries

82
Q

What hormone is probably produced by the endothelial cells of the peritubular capillary network?

A

Erythropoietin

83
Q

Purpose of vasa rectae

A

Essential for the maintenance of the osmotic gradient in the medulla (do not carry away the high osmotic gradient in the interstitium set up by the loop of Henle) –> countercurrent exchange mechanism

84
Q

What forms the stellate veins

A

Capillaries of the outer cortex and capsule

85
Q

From where do arcuate veins receive blood?

A

Interlobular veins

Venae rectae

86
Q

What forms interlobar veins?

A

Arcuate veins

87
Q

3 interstitial elements of the cortex

A
  • Delicate connective tissue elements, mostly associated with basement membranes investing the epithelial elements and their vascular supply
  • Fibroblasts
  • Macrophages
88
Q

4 interstitial elements of the medulla

A
  • More connective tissue than cortex (more abundant in the lower medulla)
  • Fibroblasts
  • Macrophages
  • Interstitial cells
89
Q

2 characeristics of interstitial cells

A
  • Lipid droplets in cytoplasm
  • Hormonal function (produce medullipin I)
90
Q

What is medullipin I

A

Precursor of a vasodilator

91
Q

Describe the thickness of the wall in the urinary passages approaching the bladder

A

The calyces, pelvis and ureters’ wall thicknesses increase progressivley with proximity to the bladder

92
Q

Where is transitional epithelium found?

A
  • Urinary bladder
  • Urinary passages
    • Minor and major calyces
    • Renal pelvis
    • Ureter
93
Q

Describe the lamina propria of the urinary bladder and the calyces, pelvis and ureter

A

Loose to dense connective tissue

94
Q

General layers of the urinary bladder and urinary passages (calyces, pelvis, ureters)

A
  • Mucosa
    • Transitional epithelium
    • Lamina propria
  • Smooth muscle
  • Adventitia
95
Q

Arrangement of the smooth muscle in the minor calyces

A

Helical

96
Q

Describe the mucosa of the ureter and how it varies

A

Mucosa has several folds that project into the lumen when the ureter is empty, but disappear when it is full

97
Q

Describe the lamina propria of the ureters

A

Dense, irrgular connective tissue

98
Q

Thickness of the transitional epithelium in the ureters

A

3 - 5 cells thick

99
Q

Describe the muscularis of the ureters

A

Most of the ureter = 2 layers:

  • Outer circular
  • Inner longitudinal

Lower third = 3 layers:

  • Outer longitudinal
  • Middle circular
  • Inner longitudinal
100
Q

Function of the bladder

A

Store the urine until the pressure inside induces the urge to urinate

101
Q

Purpose of the epithelium in the bladder

A

Osmotic barrier isolating the urine from the wall of the organ

102
Q

Describe the mucosa of the bladder

A

Numerous folds when the bladder is empty –> disappear when full

Always smooth in the area of the trigone

103
Q

Describe the superficial cells of the transitional epithelium found in the bladder

A

Large and dome-shaped

Become flattened (stretch) during distension

104
Q

Why are the surface transitional cells of the bladder able to change shape during distension?

A

Unique device in the plasma membrane = mosaic of specialized, rigid, thick plaques in between areas of normal plasma membrane

Empty = plaque regions fold into irregular, angular contours

Distended = folds disappear

105
Q

Describe the apical cytoplasm of the bladder’s epithelial cells

A

Contains fusiform vesicles with thickened membranes like the plaques

106
Q

Define the trigone

A

The area in between the openings of the ureter and the urethra

107
Q

Describe the lamina propria of the bladder

A

Superficial part of dense connective tissue

Deeper part of loose connective tissue

108
Q

Where are glands found in the bladder and what kind are they?

A

Only in the area around the urethra (mucous glands extending into the lamina propria)

109
Q

Describe the muscularis of the bladder

A
  • Smooth muscle fibers running in every direction
  • Only well-defined layers in the nack of the bladder:
    • Thick internal sphincter muscle (circular)
    • Inner and outer longitudinal
110
Q

Describe the outer layer of the bladder

A
  • Adventitia of dense, irregular connective tissue with many elastic fibers
  • Certain areas covered by serosa
  • Other regions surrounded by fat
111
Q

Describe the general musculature of the urethra as it pierces the perineum

A
  • Skeletal muscle fibres are organized as the external sphincter of the urethra (voluntary)
  • Still has an involuntary internal sphincter
112
Q

When does urinary incontinence occur?

A

Loss of voluntary control over the striated muscle of the urethra

113
Q

Describe 2 general features of the female urethra

A
  • Short
  • Normally collapsed lumen except during micturition
114
Q

Describe the epithelium of the female urethra

A
  • Transitional epithelium near the bladder
  • Stratified squamous non-keratinized epithelium along the rest of its length
115
Q

Describe the mucosa of the female urethra

A
  • Elongated folds
  • Numerous mucous glands of Littré
116
Q

Describe the tissue surrounding the mucosa of the female urethra

A

Thin, vascular coat of erectile tissue

117
Q

Describe the muscular layer of the female urethra

A
  • Inner longitudinal
  • Outer circular
118
Q

3 regions of the male urethra

A
  • Prostatic urethra
  • Membranous urethra
  • Spongy or cavernous urethra
119
Q

What surrounds the entirety of the prostatic urethra

A

Prostate gland

120
Q

Describe the epithelium of the prostatic urethra

A

Transitional epithelium

121
Q

What opens into the prostatic urethra?

A
  • 2 ejaculatory ducts
  • Multiple excretory ducts of the prostate gland
  • Prostate utriculus (a rudimentary duct)
122
Q

Where does the membranous urethra occur?

A

At the level of passage of the perineal membrane

123
Q

Define the epithelium of the membranous urethra

A
  • Stratified columnar
  • Patches of pseudostratified columnar
124
Q

What does the spongy/cavernoud urethra correspond to?

A

The part IN the penis –> terminates at the tip of the glans penis

125
Q

Describe the epithlium of the spongy or cavernous epithelium

A
  • Stratified columnar
  • Patches of pseudostratified columnar or stratified squamous non-keratinized epithelia
126
Q

Special feature of the spongy or cavernous urethra

A

Presence of mucous intraepithelial glands and periurethral mucous glands

127
Q

Describe the epithelium of the dilated terminal part in the glans penis (navicular fossa)

A

Stratified squamous non-keratinized epithelium

128
Q

Describe the lamina propria of the entire male urethra

A

Loose connective tissue that is highly vascularized

Block E -- Renal (4 decks)

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