Urinary Histology Flashcards
1
Q
What is the kidney covered by?
A
The kidney is covered by a connective tissue capsule.
2
Q
Are Pyramids located in the medulla or the cortex?
A
medulla
3
Q
What is the apex of a pyramid called?
A
the renal papilla
4
Q
What is a renal column?
A
The tissue between adjacent pyramids
5
Q
What is a renal lobe?
A
is a medullary pyramid and the overlying cortex plus 1/2 of the renal columns on each side of pyramid
6
Q
What are Calyces?
A
extensions of the renal pelvis
7
Q
What does a minor calyx surround?
A
one renal papilla
8
Q
What is a major calyx
A
A major calyx is the combination of two or more minor calyces
9
Q
How do the kidneys enable continuous monitoring of the blood and ensure optimal properties of the blood?
A
- Remove waste from the blood and excrete it as urine
- Regulate electrolyte balance (Na+, H+, K+, and Ca2+)
- Regulate plasma volume & blood pressure
- Produce hormones
10
Q
What hormones do the kidneys produce?
A
Erythropoietin, renin, and Converts vitamin D precursor to active form of vitamin D
11
Q
What does erythropoietin do?
A
regulation of red-blood cell formation
12
Q
What does renin do?
A
involved in control of blood pressure and
volume
13
Q
What is the structural and functional unit in the kidney
A
The nephron
14
Q
What does a nephron consist of?
A
a renal corpuscle and its tubule
15
Q
What is a renal corpuscle?
A
the beginning of a nephron and site for filtering blood
16
Q
Where does a nephron tubule originate? where does it end?
A
from renal corpuscles and ends at collecting duct
Collecting ducts are not part of nephron
17
Q
What does a nephron do?
A
blood is filtered and urine is produced by the nephron
– Eliminates waste from the body
– regulates H2O concentration
– regulates blood volume and pressure – produce hormones
18
Q
In humans, a normal kidney contains how many nephrons?
A
800,000 to 1,000,000 nephrons
19
Q
What are the segments of a nephron tubule?
A
1) proximal thick segment
2) thin segment
3) distal thick segment
20
Q
What are the segments of the proximal thick segment?
A
first the Prox. convoluted tubule (PCT), and then continuous with the Prox. straight tubule (PST)
21
Q
Where are the renal corpuscle and the proximal convoluted tubule located in the nephron?
A
the cortex
22
Q
Where is the proximal straight tubule located in the nephron?
A
in the outer stripe of the outer medulla
23
Q
What segment comes after the proximal straight tubule? Where is it located in the nephron?
A
the thin segment, which extends from the inner stripe of the outer medulla and down into the inner medulla where it forms a loop back up to the edge of the inner medulla
24
Q
What comes after the thin limb in the nephron tubule?
A
the Medullary thick ascending limb (MTAL) of the distal thick segment and then the cortical thick ascending limb (CTAL) that ends approximately at the edge of the medulla
25
What is the macula densa? Where is it?
an area of closely packed specialized cells lining the wall of the cortical thick ascending limb, at the transition to the distal convoluted tubule.
26
What does the macula densa do?
The cells of the macula densa are sensitive to the concentration of sodium chloride in the late thick ascending limb. A decrease in sodium chloride concentration initiates a signal from the macula densa that has two effects:
(1) it decreases resistance to blood flow in the afferent arterioles via vasodilation, which increases glomerular capillary hydrostatic pressure and helps return glomerulus filtration rate (GFR) toward normal, and (2) it increases renin release from the juxtaglomerular cells of the afferent and efferent arterioles, which are the major storage sites for renin.[1]
27
What are the components of the Loop of Henle?
PST, TL, & MTAL
28
What is next in the nephron tubule after the CTAL?
the distal convoluted tubule (DCT)
29
Where is the DCT?
in the cortex. The DCT connects to the connecting segment (CS), which connects to the cortical collecting duct
30
What are the parts of the proximal nephron tubule?
PCT to the macula densa
31
What are the parts of the distal nephron tubule?
distal to the macula densa. contains the DCT and the connecting segment (CS)
32
What do collecting ducts do?
conducts urine from nephron tubules to renal papillae
33
Are Collecting ducts are part of the nephron?
No. Many nephron tubules will contribute to a single collecting duct
34
What are the components of collecting ducts?
Cortical collecting duct (CCD)- ends at edge of cortex
Medullary collecting duct (MCD)
35
Where do the collecting ducts dump into the minor calyces?
in the ducts of Bellini in the apex of the renal papilla (in the 'area cribrosa')
36
What are some ways to distinguish between proximal and distal convoluted tubules in the cortex?
* The lumen of a proximal tubule has a star-shaped lumen and a brush border. The lumen of distal tubule is more rounded and the luminal surface of the cells is sharper.
* The outside diameters of proximal tubules are generally larger than those of the distal tubules.
* A cross section or a proximal tubules display a smaller number of nuclei than cross-section of distal tubules.
* Proximal tubules are twice as long as distal tubules and thus most of the tubules observe in the cortical labyrinth will be proximal tubules.
37
What are some ways to distinguish between collecting ducts, thin segments, and cortical straight segments?
* Collecting ducts have outside diameters comparable to those of the proximal tubules and larger than those of distal tubules.
* The cells forming the wall of collecting ducts are cuboidal and smaller than those of proximal tubules; thus, they also display a relatively larger number of nuclei than do comparable segments of proximal tubules.
* Thin limbs have thinner walls than tubules. Their wall is made of low cuboidal or simple squamous epithelium.
38
What is the connective tissue of the kidney parenchyma?
the interstitum
39
What does interstitium surround?
Surrounds the nephrons, ducts, and blood and lymphatic vessels (won't see many of the cells)
40
Is interstitium higher concentrated in the cortex or the medulla?
Medulla.
Increases considerably in amount from the cortex (7% of volume) to medulla and papilla (20%)
41
In cortex, what are the interstitial cells?
fibroblasts and macrophages
42
In medulla, interstitial cells resemble what?
myofibroblasts- (compress the tubule through actin).
Oriented in the long axes if the tubular structures and may have role in compressing these structure
43
What is the beginning of the nephron?
| What happens there?
The renal corpuscle is the beginning of the nephron. Blood is filtered in the renal corpuscle and provisional urine (the utlrafiltrate) is produced
44
Describe the organization of the renal corpuscle in relation to blood flow
Blood enters the vascular pole via afferent arterioles and then goes to the glomeruli where it is filtrated (not deoxygenated). The filtrate is called the ultra filtrate (precursor of urine) and sits in the urinary space (which is formed by the visceral and parietal layers of Bowman's capsule). Filtrated blood then exits the corpuscle through the efferent arteriole at the vascular pole. Ultra filtrate then exits then corpuscle through the urinary pole at the PCT
45
What kind of cells does the visceral layer of Bowman's capsule have?
podocytes
46
The renal corpuscle also contains mesangial cells. What do these cells do?
Mesangial cells surround the capillaries phagocytose debris, provide structural support, and secrete interleukin I platelet derived growth factor for repair of glomerulus
47
What are the types of nephrons? What are they categorized based on?
1) corticol (subcapsular) nephrons
2) Juxtamedullary nephrons
3) Intermediate nephrons
Nephrons are categorized based on their locations in the cortex
48
Where are Juxtamedullary nephrons found?
close to the medullary boundary
49
Describe the loop of henle of the corticol nephrons
they are really short and only extend down into the outer strip of the medulla (so it will have a different role in urine production)
50
Describe the loop of henle of the juxtamedullary nephrons.
it is really long and extends deeply into the medulla
Intermediate nephrons have intemediate sized loops
51
What are the two subdivisions of the cortex?
cortical labyrinths and medullary rays
52
What do cortical labyrinths consist of?
consist of renal corpuscles, proximal convoluted and distal convoluted tubules.
53
What do medullary rays consist of?
consist of aggregation of straight & ascending tubules and collecting ducts - lies between cortical labyrinth
54
The cortical labyrinths and medullary rays are organized into what? What do they consist of?
lobules. Lobules consist of a medullary ray and adjacent one-half labyrinths
55
T or F. the medulla has no labyrinths or medullary rays, only tubules and collecting ducts
T. The tubules are the segments that make up the loop of Henle: proximal straight, thin limb,
and distal straight (note you will not be able to distinguish between PST and DST)
56
The kidney receives __% of cardiac output
25% (via the renal artery)
57
How much of the 25% of cardiac output received by the kidney goes to the cortex?
90%
58
Describe kidney blood flow
renal arteries branch into Lobar arteries, which branch into interlobar arteries.
• Interlobar arteries branch into arcuate arteries – arteries that “arc” around the boundaries of papillae
• Arcuate arteries branch into interlobular arteries
• Interlobular arteries branch into afferent arterioles
• The afferent arteriole give rise to tuft of capillaries that form the glomerulus
• Capillaries in the glomerulus reunite to form the efferent arteriole
• The efferent arteriole give rise to a second network of capillaries
59
What is the capillary network formed by the efferent arteriole of a cortical corpuscle called?
a peritubular capillary network that surrounds the local tubules
60
What is the capillary network formed by the efferent arteriole of a juxtamedullary corpuscle called?
vasa rectae
61
What are the three principal activities of
| nephrons in producing urine?
• Filtration of blood, occurs in the renal corpuscle: creates ultrafiltrate (aka provisional urine)
• Reabsorption occurs most abundantly from the proximal convoluted tubule:
– The filtered products - water, electrolytes, and glucose - are reabsorbed back into the capillaries
• Secretion: substances (H+, K+, NH3 and certain drugs) are secreted from the blood into the the tubules (where urine exists)
62
Glomeruli contain a filtration apparatus. What are the components?
1. Fenestrated endothelium of glomerulus (i.e., capillary)- prevents blood cells from passing but allows blood plasma
2. Basement membrane of the glomerulus (the loops of capillaries)
3. Basement membrane of podocytes
63
The basement membrane of the glomerulus (the loops of capillaries) and the Basement membrane of podocytes make up what?
glomerular basement membrane
The glomerular basal lamina restricts the movement of particles based on size:
• proteins like albumin and hemoglobin, for example, are too large
64
What are pedicles?
* Podocyte processes form numerous secondary processes called pedicels (or foot processes) around glomerulus
* Pedicels from different podocytes interdigitate around the glomerulus to form 'filtration slit (membranes)" where filtration can occur in between the pedicels
65
What are the three layers of the basement membrane of the glomerulus?
Outside to inside:
lamina rara externa
lamina densa
lamina rara interna
66
What is the ultimate barrier of the basement membrane of the glomerulus that excludes molecules based on size?
the lamina densa (if molecules are neutrally charged and less than 70,000 Daltons, they will pass)
67
T or F. albumin generally excluded, but is so close to the minimal passage size that if the filter is damaged, albumin will appear in the urine
T.
Also, negative charges due to heparan sulfate and sialic acid tend to impede the passage of negatively charged molecules that are small enough to pass
68
What happens to the basement membrane of the glomerulus in diabetes mallitis? What results?
The basal lamina is physically thicker than normal, but is functionally leaky so an excessive amount of protein is lost in the urine (proteinurea). May lead to low blood albumin (hypoalbuminemia). This in turn leads to a low colloidal osmotic pressure in blood with resulting (edema)
69
Edema, proteinurea, and hypoalbuninemia together are called?
Nephrotic Syndrome
70
The greatest amount of reabsorption into peritubular capillaries is from where?
proximal convoluted tubule (Reabsorption occurs to lesser degree from other tubules)
71
What is reabsorbed into the PCT?
most of the water and electrolytes and all of the glucose are reabsorbed
72
Secretion from peritubular capillaries of most products (H+, K+,, NH3 and certain drugs) occurs where?
in distal parts of nephron (thin limb and distal tubules) and the collecting ducts
73
As the ultrafiltrate journeys through the nephrons and collecting ducts, reabsorption and secretion is largely managed by what?
electrochemical reactions, (causing the urine to become more concentrated)
A person typically excretes 1.5 to 3 liters of urine daily.
74
What does the juxtamedullary apparatus consist of?
consists of macula densa, the juxtaglomerular cells (on afferent and efferent arterioles) and extraglomerular mesangial cells
75
What does the juxtamedullary apparatus do?
regulates BP
76
T or F. The macula densa cells are narrower, usually taller, and more crowded (macula densa) than adjacent tubule cells
T. Thejuxtaglomerular cells of the afferent
| and efferent arterioles are specialized smooth muscle cells
77
What do the macula densa cells do in the juxtamedullary apparatus?
monitor blood volume and Na+ concentration
78
What do JG cells do?
under certain physiological conditions (low Na+ intake or decreased volume of circulating blood) are responsible for activating a system (renin-angiotensin- aldosterone) for restoring homeostasis
79
Overview of regulation of blood pressure by JG apparatus
* The macula densa cells monitors physiological conditions and communicate with the JG cells.
* The JG cells contain granules, renin, which is synthesized, stored, and released when signaled to by the macula densa cells.
80
What initiates the renin-angiotensin-aldosterone system?
Release of renin
81
All excretory passages of the kidney (except the lower part of the urethra are lined by what kind of epithelium?
transitional epithelium
Note that urinary transitional epithelium is aka urothelium
82
All excretory passages except the urethra have the same general organization: what is it?
mucosa, thin (if present) submucosa, muscularis, and adventitia (or serosa)
– Note that urinary passages do not have muscularis mucosa
83
The lower part of the urethra
| has what kind of epithelium?
stratified or pseudostratified
| columnar epithelium.
84
Where is the muscularis found?
ureter and bladder
85
What does the muscularis of the ureter look like and what does it do?
3 layers- an inner longitudinal layer, a middle circular layer, and an outer longitudinal layer.
(The outer longitudinal layer is present only in the distal end of the ureter)
• Regular peristaltic contractions of the muscularis muscles contribute to the flow of urine.
86
The lumen of the bladder is lined with what?
transitional epithelium (aka urothelium)
87
What does the muscularis of the bladder look like?
Muscularis: inner longitudinal, middle circle, & outer longitudinal layer, muscularis is thicker in bladder than ureter
88
Does the bladder have adventitia or serosa?
Adventitia except where superior surface has serosa
