Urinary Histo Flashcards
1
Q
Exocrine function (4)
A
- Removes metabolic wastes and foreign substances
- Regulates body fluid
- Regulates body salt content
- Controls acid-base balance
2
Q
Endocrine function (3)
A
- Renin secretion: regulation of blood pressure
- Erythropoietin secretion: stimulates production of red blood cells
- Controls calcium metabolism by activating 1,25-(OH)2: vitamin D3
3
Q
Gross anatomy of kidney
A
- bean shaped
- connected to blood vessels and ureter
4
Q
2 regions of anatomy of kidney
A
Cortex: outer, reddish area
which receives ~ 90% - 95% of
the blood passing through the
kidney
Medulla: inner, lighter colored
5
Q
Regions of kidney labeled
A
6
Q
Portions of cortex
A
- Cortical labyrinth (area with corpuscles)
- Medullary ray (same tissue as medulla)
7
Q
Portions of cortex labeled
A
8
Q
Number of lobes: major and minor calyces
A
major: 2-3
minor: 5-11
9
Q
How many lobes do humans have?
A
8-12 lobes per kidney (3-4 are sufficient for life)
10
Q
Lobe labeled
A
11
Q
What are lobes divided into?
A
Lobules
12
Q
What does a lobule consist of?
A
- medullary ray (center)
- surrounding cortical material
13
Q
Lobule structure image
A
14
Q
What does a renal secretory duct consist of?
A
- collecting duct
- group of nephrons that drain into that duct
15
Q
What is the functional unit of the kidney?
A
Nephron
16
Q
2 types of nephrons:
A
- juxtamedullary
- cortical
17
Q
What gives the layers and striations in a hemi-sected kidney?
A
Arrangement of the tubules
18
Q
Filtration units (4)
A
- Renal corpuscle: glomerulus, Bowman’s cap
- Proximal thick: convoluted and thick
- Distal thick: convoluted and thick
- This segment: descending, ascending
19
Q
Filtration units in the cortex (2)
A
- cortical labyrinth
- medullary ray
20
Q
Filtration units in the medulla
A
- outer medulla (o)
- outer medulla (i)
- inner medulla
21
Q
cortical labyrinth segments
A
- renal corpuscles
- PCT
- DCT
22
Q
medullary ray segments
A
- PST
- DST
- CD
23
Q
outer medulla (o)
A
- PST
- DST
- CD
24
Q
outer medulla (i)
A
- thin seg of Henle’s Loop
- DST
- CD
25
inner medulla
- thin seg of Henle's Loop
- CD
26
Which 2 segments of the nephron have the same composition?
Medullary Ray and Outer Medulla (outer stripe):
- PST
- DST
- CD
27
Juxtamedullary vs Cortical Image
28
Renal corpuscle poles
29
Renal corpuscle image
30
Bowman's capsule layers:
– parietal layer, simple squamous
– visceral layer, podocytes w/ foot processes (pedicels)
– bowman’s space (urinary/capsular space)
31
Renal corpuscle layer formation
32
Renal corpuscle image
33
Visceral/podocyte image
34
Filtration Apparatus Components (3)
1. Glomerular capillary endothelium
2. Glomerular basement membrane
3. Visceral/podocyte layer of Bowman’s capsule
35
Filtration Apparatus EM
36
Filtration Apparatus EM
37
FA: Glomerular Capillary Endothelium
- fenestration diameter
- lacks a diaphragm
- aquaporin-1 water channels
- thick glycocalyx on the luminal side
38
FA: Glomerular Basement Membrane
- physical & charge barrier
- 3 areas:
1. lamina rara interna
2. lamina densa
3. lamina rara externa
39
FA: Visceral Layer of Bowman’s Capsule
- contains podocytes
- cells are coated with podocalyxin (negatively charged)
- podocytes extend processes that surround the capillaries
40
Podocyte slit diaphragms EM
41
Slit diaphragms EM
42
What is the purpose of slit diaphragm?
- increase filtering power of the podocyte
43
What type of junction is the slit diaphragm?
modified adherens junction
44
Which transmembrane protein is associated with the slit diaphragm?
Nephrin contributes to the structure and function of the diaphragm
45
Mutations in the nephrin gene?
- congenital nephrotic syndrome
- blood in urine
46
Filtration Apparatus Summary
1. Glomerular capillary endothelium -
water channels, size, and ion barrier
2. Glomerular basement membrane –
physical barrier and an ion-selective filter
3. Podocytes – filtration slit membrane =
physical barrier (true size-selective barrier)
47
Mesangium refers to
mesangial cells and extracellular matrix between the glomerular capillaries
48
Where are mesangial cells most evident?
vascular pole
49
What are extraglomerular mesangial / lacis cells?
mesangial cells that are located outside of the renal corpuscle
50
Lacis and mesangial cells image
51
Mesangial cells EM
52
How are mesangial cells able to contract?
Because they are modified SM cells (and surrounded by a basal lamina)
53
What do mesangial cells secrete?
Erythropoitin
54
4 major functions of mesangium:
1. Phagocytosis/endocytosis – remove trapped molecules and renew the basal lamina
2. Structural support
3. Contraction to regulate blood flow
4. Secretion – IL-1, PDGF
55
Mesangial cell image
56
Mesangial cell image
57
Prox tubule location
Cortical labyrinth
58
Prox tubule function
– REABSORPTION
– 65% H2O, electrolytes
– 100% glucose, amino acids
– Protein resorption by endocytosis (microvilli)
– pH modification: secretion of organic
acids & bases
59
Prox tubule image labeled
60
Prox convoluted tubule image labeled
61
Prox convoluted tubule brush border image
62
Prox convoluted tubule brush border and glycocalyx image
63
Prox convoluted tubule reabsorption by endocytosis image
64
Purpose of basal striations (with elongate mitochondria) in prox convoluted tubule?
- increase SA of cell
- area has active pumps that require energy (Na/K ATPase Pump)
- the pumps allow Na, Cl, and H2O into intercellular space
65
PST location
- medullary ray
- outer medulla (o)
66
PST function
- reabsorption, but ells are not as
specialized for reabsorption than PCT cells
67
PST characteristics
- cuboidal epithelium
- STAR-shaped nucleus
- larger lumen than DST
- permeable to H2O
68
PST image
69
Henle's Loop Location
- entire U shaped segment
- PST
- DST
- thin segment
70
Henle's Loop Functions
- descending limb is highly permeable
to water & less permeable to solutes
→ tubular fluid osmolality increases
- ascending limb is highly permeable to
NaCl, but impermeable to H2O
→ tubular fluid becomes hypo-osmotic
71
What type of epi is in tubules?
cuboidal
72
What type of epi is in Bowmans Cap and Henle's Loop?
simple squamous
73
Henle's Loop Image
74
Is Henle's Loop longer in cortical or juxtamedullary nephrons?
Juxtamedullary nephrons
75
DST location
- medullary ray
- outer medulla
76
DCT location
- cortical labyrinth
77
DST image
78
DST Functions
- apical membrane has symporters
→ NaCl pumps
- is impermeable to water
→ separation of water from its solutes
occurs here
79
DCT Functions (4)
1. reabsorption of Na+ and secretion of K+
2. reabsorption of bicarbonate ions and
secretion of H+
3. secretion of ammonium
4. is impermeable to water unless ADH is present
80
DCT histo
- cuboidal
- few short microvilli (no brush border)
- mitochondria have a ‘longitudinal’ orientation in the basal portion of the cell - no prominent apical vesicles
- nucleus more apically located: nuclei appear to bulge into the lumen
81
DCT image
82
PCT vs DCT Characteristics
83
PCT vs DCT Image
84
PCT vs DCT Image
85
Macula densa
- specialized region of DT
- located at vascular pole
- senses the amount of sodium and chloride in distal tubule
86
Macula densa image
87
Macula densa image
88
Juxtaglomerular Apparatus Functions
- regulates blood pressure
- maintains sodium homeostasis and renal hemodynamics
89
What does the juxtaglomerular apparatus include?
1. macula densa
2. juxtaglomerular cells (JG cells)
3. extraglomerular mesangial cells (lacis cells)
90
JG Cells Functions
- modified SM cells of the
afferent arteriole
- have rounded nuclei and SECRETORY GRANULES (renin)
- renin is released in response to paracrine stimulation from the macula densa
91
JG cells image
92
Lacis Cells Functions:
- connect with each other via gap
junctions
- function is unclear; possibly relay info to the JG cells
93
Lacis Cells Image
94
CD function
- collect pre-urine from the nephrons
95
4 Types of CD/CT
1. Connecting tubule: cortical labyrinth, horizontal tubule
2. Cortical duct: medullary rays
3. Medullary duct: medulla
4. Papillary duct: papillary region
96
Epithelial lining of CD:
- Simple cuboidal or columnar epithelium
- Smooth lumen
- Lightly stained
- Clear cell boundaries
- Central and round nuclei,
evenly spaced
97
CD image
98
2 types of cells in the collecting ducts:
- Light cells = principle
- Dark cells = intercalated cells
99
Light/principle cells (majority)
-single cilium
-short microvilli
-basal infoldings
-abundant ADH-regulated water channels
100
Dark/intercalated cells
-less abundant than light cells
-microplicae (folds) on apical surface
-secrete H + (α intercalated) or bicarbonate (β intercalated) cells
101
CD: dark/light cells image
102
Papillary CD:
- In papillary region (inner
medulla)
- Columnar cells
- Openings at the tip
103
Papillary CD Image
104
Interstitium of the kidney is made up of...
Cortical interstitium: ~7%
Medullary interstitium: up to 20%
105
Cortical interstitium:
- fibroblast-like macrophages
- fibroblasts produce EPO in responce to hypoxia or anemia
106
Medullary interstitium
- myofibroblasts oriented to the long axis of the tubules
- secrete prostaglandins (vasodilator)
107
Blood Supply of the Kidney Order
Interlobular artery
Arcuate artery + vein
Interlobar artery + vein
Segmental artery
Renal artery + vein
108
Blood Supply of the Kidney
109
Interlobular and arcuate arteries imagery
110
Juxtamedullary Glomeruli
* 15% of total
* Maintains hypertonicity of the medulla
* Vasa rectae
111
Cortical Glomeruli
* 85%
* Peritubular capillaries
Interlobular veins
* Picks up resorbate from
proximal and distal tubules
112
Countercurrent Systems
in Medulla
1. Countercurrent Multiplier System –
Loop of Henle
2. Countercurrent Exchange System –
Vasa recta
3. Collecting Duct permeability
113
Excretory Passage
Minor calyx → Major calyx → Renal pelvis → Ureter → Bladder → Urethra
114
Excretory passages (besides urethra) general organization:
- mucosa
- muscularis
- adventitia
- serosa (in some regions)
115
excretory passages organization characteristics
1. Mucosa
a. Transitional epithelium
(urothelium): lies the calyces, ureters, bladder and the initial segment of the urethra
b. Lamina propria: dense
collagenous
2. Muscularis
a. longitudinal inner layer b. circular outer layer
3. Adventitia or Serosa
116
Ureter - Histological features
– Transitional epithelium:
impermeable to H20 and salts
– Lamina propria: dense collagenous
– Muscularis: 2 layers (inner longitudinal, outer circular), less regular, mixed w/ CT
– Adventitia or serosa: loose CT
117
Ureter image
118
Urinary epi image
119
Transition epi image
120
Over distended vs not distended (relaxed) bladder images
Distended has thinner epi; relaxed has thicker epi layer
121
Urinary Bladder Characteristics
- distensible reservoir for urine
- Rugae region for extension
- Parasympathetic innervation forms the efferent fibers of the micturition reflex
- compression of the smooth muscle of the bladder also compresses the openings of the ureter into the bladder preventing urine backflow and spread of infection
122
Urinary Bladder Histo
Mucosa:
- has rugae except for the trigone region
- Transitional epithelium; 5-7 layers
- Thick layer of connective tissue with blood vessels & nerves
Muscularis
- generally described as three layers but the layers are indistinct: inner & outer longitudinal, middle circular
Adventitia or Serosa
123
Urethra F vs M
124
Urethra image
125
Urethra image
