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MBBS I CPRS > L28 – Histology and Functions of Blood Vessels > Flashcards

L28 – Histology and Functions of Blood Vessels Flashcards

(123 cards)

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1
Q

What 3 things make up the circulatory system?

A

Heart, Blood vessels, Lymphatic vessels

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2
Q

What are the roles of circulatory system? (Transport, heat… etc)

A
  • Transport blood, nutrient, gases, waste
  • Maintains and regulates blood flow and BP
  • Protect body from infection
  • Thermoregulation
  • Maintain fluid balance
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3
Q

What are 3 categories of blood vessels?

A

arteries, veins, capillaries

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4
Q

What are the layers of blood vessels and heart?

A

Heart: Endocardium, Myocardium, Epicardium

Blood vessels (expt capillaries): Tunica Intima, Tunica Media, Tunica Adventitia

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5
Q

3 layers to heart endocardium?

A

1) endothelium : simple squamous w/ basment membrane
2) sub-endothelial layer of loose connective tissue and smooth muscle cells
3) Subendocardium

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6
Q

What is contained in subendocardium inside endocardium?

A

Purkinje fibers (specialized cardiac muscle cells), small coronary blood vessels, nerve fibres

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7
Q

How does the histology of purkinje fibres compare to regular cardiac myocytes? (think size, colour of cytoplasm and rim, features)

A 
 Larger, 1-2 nuclei
 Lots of pale-staining glycogen, mitochondria in cytoplasm
 Fewer myofibrils at periphery 
 dark rim
 No T-tubules, intercalated discs
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8
Q

What is the purpose of subendocardium?

A

Connects endocardium to myocardium

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9
Q

What is special about heart valve endocardium?

A

heart valves = extensions of endocardium

Dense connective tissue core (annulus fibrosus) instead of regular subendocardium.

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10
Q

What 2 things are found in Myocardium?

A

Cardiac muscle, extensive vasculature

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11
Q

How are myocytes in myocardium arranged?

A

Layers of spirally-arranged cardiac muscle fibers

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12
Q

Is cardiac myocyte branched or not?

A

Branched (unlike skeletal muscle )

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13
Q

What are the types of cell junctions in cardiac myocyte?

A

Intercalated discs connect individual cells by 3 types of cell-cell
junctions:

  1. Gap junctions
  2. Adherens junctions
  3. Desmosomes
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14
Q

What are myocardium myocytes organised into?

A

Fascicles

bounded by connective tissue (contains coronary
vessels, nerve fibers)

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15
Q

What is the tissue type in epicardium?

A

fibroelastic loose connective tissue

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16
Q

What is another name for epicardium?

A

Serous pericardium

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17
Q

What epithelium covers epicardium? What does it do?

A

mesothelium (simple
squamous epithelium):
produces, secretes
pericardial fluid

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18
Q

What are the components to epicardium?

A

fibroelastic loose connective tissue

nerves

adipose tissue

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19
Q

What is Between visceral and parietal layer of serous

pericardium?

A

pericardial cavity

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20
Q

What is the outermost pericardium? made of?

A

fibrous pericardium

adipose tissue

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21
Q

What are the 3 layers of heart valves?

A 
(Endothelium) 
Spongiosa 
Fibrosa 
Ventricularis 
(Endothelium)
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22
Q

What tissue makes up heart valve spongiosa layer?

A

Loose connective tissue (loosely arranged collagen and elastic fibers)

covered by endothelium

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23
Q

What tissue makes up Fibrosa layer of heart valves?

A

Dense Irregular connective tissue

Fibres extend from cardiac skeleton

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24
Q

What tissue makes up Ventricularis of heart valves?

A

Dense connective tissue covered by endothelium

Many layers of elastic fibres

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25
What structure of heart valve is continous with chordae tendineae?
Ventricularis layer
26
4 classes of arteries and veins?
Arteries: Large Elastic, Medium Muscular, Small, Arterioles Veins: Large, Medium, Small, Venules
27
Run through route of blood circulation from heart back to heart?
Aorta > Muscular arteries > small arteries and arterioles > capillaries > venules and small veins > medium veins > S/I Vena Cava > Heart
28
What are the three components to Tunica intima?
Simple squamous epithelium w/ basement membrane Subendothelial layer Internal elastic membrane (In arteries and arterioles)
29
What is found in subendothelial layer of tunica intima?
Loose connective tissue Sometimes smooth muscle
30
What is internal elastic membrane for?
Fenestrated elastic material boundary between tunica intima and media
31
Is the epithelium in tunica intima continous from arteries to capillaries?
Yes
32
What connects the endothelial cells in tunica intima?
Endothelial cell Junctional complexes
33
What are the two roles of tunica media?
Regulate blood flow Provide structural support
34
What are the structures of either side of tunica media in large arteries?
Internal elastic membrane External elastic membrane
35
What is found in the tunica media predominantly in arteries?
Layers of vascular smooth muscle cells
36
What structure exists between smooth muscle cells in tunica media?
Fenestrated lamellae of elastin and collagen interposed between SM cells
37
Which layer of blood vessels is thickest in arteries?
Tunica media
38
Which layer of blood vessels is thickest in Veins?
Tunica Adventitia
39
What is tunica adventitia of vein mainly made of?
Longitudinally arranged loose collagen and few elastic fibres Smooth muscle cells (can be longitudinal or circular)
40
What two structures are specially located in tunica adventitia?
Vasa Vasorum Nervi Vasorum
41
``` Artery vs veins. Wall Thickness? Shape? Lumen size? Valves? ```
Thickness: Artery thicker, vein thinner Shape: Artery more uniform and circular, vein appears irregularly shaped and weaker flaccid walls Lumen size: Vein lumen larger than artery lumen Valves: Only in veins
42
Why is artery walls thicker than veins?
Thicker walls = withstand pulsatile flow from heart and higher BP Veins have Less elastic tissue, less smooth muscle = much thinner media
43
Artery or veins hold more blood?
Veins 2/3 of all circulating blood
44
What 2 membranes are found only in arteries but not veins?
Internal and External elastic membrane surrounding tunica media
45
Compare the smooth muscle orientation between artery and vein tunica media and adventitia?
Tunica media: Artery= circular SM , Vein = circular SM Tunica Externa: Vein= Longitudinal SM
46
What are the three types of capillaries?
Continuous, Fenestrated, Discontinuous/ Sinusoidal
47
Large elastic/ conducting arteries can maintain blood flow with what structure?
abundant elastic fibers in tunica media > expand during systole , RECOIL during diastole accommodate pressure changes
48
What are the two effects of high elastin content in tunica media of larger arteries?
o maintain BP, blood flow and accommodate pressure changes o Propel blood forward transport blood from heart to smaller arteries
49
Give examples of Large elastic arteries?
Aorta, pulmonary trunk (plus main branches e.g. bronchiocephalic artery)
50
What blast cell is found in tunica adventitia of both artery of vein?
Fibroblast
51
Are internal and external elastic membranes easily observed in large elastic arteries?
No, hard to distinguish from nearby elastic lamellae
52
Is the tunica intima of large elastic arteries thick or thin? contains what?
Thick subendothelial layer but thin overall tunica intima Contains SM, collagen, elastic fibres
53
How is the elastin arranged in tunica media in large elastic arteries?
Elastin arranged in Fenestrated Concentric lamellae
54
How many lamellae of elastin does Aorta have?
40-70
55
What tissue makes up tunica adventitia in large elastic arteries
Loose connective
56
Which of 4 types of arteries regulate blood distribution to organs by altering lumen size?
Medium muscular arteries Regulate circulatory dynamics through vasoconstriction/ dilation > control distribution of blood to body parts
57
Compare the amount of SM and elastin between large and medium arteries.
Medium A have more SM and less elastin compared to Large A in tunica media
58
Compare visibility of internal and external elastic membrane between large and medium arteries?
``` Large = not conspicuous Medium = Clearly distinguishable ```
59
What happens to number of SM cells and Internal/ external elastic membrane in tunica media of medium arteries when it branches?
``` branch and decrease in size:  Number of layers of smooth muscle cells in tunica media decreases  Internal/ external elasti laminae become much less prominent ```
60
Compare the thicknes of tunica intima in large and medium arteries?
Medium arteries have THINNER tunica intima than Large A
61
How may tunica intima of medium A be expanded over time?
Expanded through aging by lipid deposition
62
What makes up the tunica media of Medium muscular arteries?
Almost entirely spirally- arranged smooth muscle Collagen fibres, little elastin
63
Compare thickness of tunica adventitia between Large and medium A?
Medium A has THICKER tunica adventitia than Large A
64
Which of 4 arteries can change peripheral resistance?
Small arteries and Arterioles
65
How can small arteries and arterioles be told apart?
By Number of smooth muscle cell layers in tunica media and size Small arteries = 3-8 layers Arterioles = 1-2 layers
66
What happens to internal and external elastic membrane in transition from small arteries to arterioles?
Membranes become less defined and disappear Arterioles have NO external elastic membrane
67
Explain arteriole changing peripheral resistance?
``` Tunica Media consists of 1-2 layers of smooth muscle cells: vasoconstrict / vasodilate > dramatic changes in lumen diameter > change resistance to blood flow and systemic BP ```
68
Arteriole smooth muscle contraction has 2 effect?
Effects on distribution of blood flow and systemic arterial pressure
69
Explain how arterioles can perform AV shunt?
``` Blood flow from metarteriole/terminal branch into capillaries,  Relax precapillary sphincters: blood flow through capillaries  Contract spincters: blood flow through thoroughfare channel, bypass capillaries (AV shunt) ```
70
What is the SM at the start of a capillary bed and end of arteriole?
Precapillary sphincter
71
What makes up a capillary wall?
Single layer of endothelial cells + basement membrane
72
Diameter of capillary?
Smaller than diameter of RBC | 7-10 µm
73
Role of capillaries?
Allow fluid to move between capillary and interstitial space
74
Where are pericytes found?
Intimately surrounding capillaries, enclosed within basal lamina
75
What are the roles of pericytes?
Undifferentiated mesenchymal cells: Give rise to endothelial cells and SM cells Provide vascular support and stability of capillaries
76
What is diapedesis?
Leukocytes squeezing through intact walls of capillaries to site of inflammation or tissue injury
77
What is the difference in basal lamina between three types of capillaries?
Continuous and fenestrated capillaries = continuous basal lamina Discontinuous capillary = discontinuous or missing basal lamina
78
What is the difference between endothelial cells of three capillary types?
Continuous cap. = Complete endothelial cells Fenestrated cap. = fenestrated endothlial cells perforated by small pores Discontinuous cap. = Incomplete endothelial cells perforated by large pores
79
Compare the permeability of three types of capillaries?
Continous cap.= very limited movement between adjacent endothelial cells Fenestrated cap. = for rapid exchange of substances Discontinuous cap. = Allow direct communication, most permeable, allow proteins or even cells to pass
80
Which capillary type is most common?
Continuous
81
Continuous cap. found where?
Muscle Lung CNS
82
How can larger molecules be transported in continuous cap.?
Macromolecules (e.g. protein) from blood, extracellular space can pass via pinocytotic vesicles
83
Fenestrated cap. found where?
Sites of fluid and metabolite exchange (absorption and excretion): Endocrine glands Gall gladder Kidney Intestinal tract / mucosa, villi
84
What is the fenestrated endothelial lining pores covered by?
60- 80nm pores covered by thin “diaphragm”, except in glomeruli
85
Discontinuous capillaries found where?
Sites of blood exchange: No barrier to blood exchange: Liver Spleen Bone Marrow
86
What cells in liver associate with discontinuous capillary in liver?
Kupffer cells =macrophages in liver Ito cells
87
What 3 mechanisms assists venous blood return?
Musculovenous pump (external compression) Respiratory pump (via thoracic pressure created in breathing) Artery pulsation (smooth muscle contraction and BP)
88
What is the role of venules?
Drain exchanged blood from cap. to small veins
89
Classify venules. Typical diameters?
Postcapillary venules (smaller) Muscular venules (larger, 1-2 layers of SM) 10 µm – 1 mm
90
Do venules have tunica adventitia?
No
91
Venules have subendo thelial layer?
No
92
Which type of venule has no true tunica media?
Postcapillary
93
Compare small veins and muscular venules tunica adventitia?
Small vein has tunica adventitia
94
Size of small veins?
1-10 mm
95
Compare the tunics of small vein with venules.
All three tunics intact and present in small veins
96
Compare layers of SM in tunica media of small vein vs venule
Muscular venules = 1-2 layers of SM Small vein = 2-3 layers of SM
97
Where are most medium veins found? diameter.
Depp veins that accompany arteries, up to 10mm
98
Where are valves in medium veins found in body?
Inferior portion/ lower limbs
99
Do medium veins have internal elastic membrane and subendothelial layer?
Yes but discontinuous Yes
100
Describe tunica media of medium veins.
Several layers of circularly arranged SM cells with interspersed collagen and elastin
101
Compare the SM layout in tunica media vs adventitia of medium veins?
SM in media = circular SM in adventitia = longitudinal
102
How are Large veins classified vs medium veins?
Large vein = diameter larger than 10mm
103
Give three examples of large veins?
Portal vein Vena Cava Subclavian veins
104
Describe tunica adventitia and role in large veins.
Thickest layer Longitudinally disposed SM Force blood toward heart: contract > shorten > close valves > help venous return
105
Describe tunica media in Large veins.
Thin Circumferentially arranged SM, Collagen, fibroblasts
106
Where are myocardial sleeves found?
Inf. Sup. Vena Cava | Pulmonary trunk
107
What are varicose veins?
Due to leaky valves, weakness in vein wall, prescence of abnormal masses
108
What veins in body most prone to varicose veins?
Veins of lower limb
109
Risk factors > varicose veins?
Hereditary Pregnancy Obesity Aging
110
Difference between simple and portal system in circulatory routes?
Simple pathway = blood pass through one network of capillaries Portal system= blood pass through 2 consecutive capillary networks
111
Give 2 examples of portal system circulation.
Hepatic portal system | Nephron Peritubular capillaries and Vasa Recta
112
What is AV shunt? What does it allow and where is it found?
Arteriovenous anastomosis Allow blood to bypass capillaries by providing direcct route Found in node, lips, fingertips, erectile tissue of penis and clitoris
113
What are 2 other types of anastomosis apart from AV?
Venous and Arterial anastomosis
114
Role of arterial anastomosis?
Backup route for blood in case of blockage e.g. in functional end arteries of coronary circulation, pelvis anastomosis ...etc
115
Which anastomosis type is most common?
Venous
116
Where is interstitial fluid collected?
By blind-ended lymph capillaries from interstitial spaces
117
Sequence of lymph drainage starting at interstitial space.
Interstitial space > Several Afferent lymphatic vessels > lymph nodes> converge to efferent lymphatic vessels > Larger lymphatics and major lymph vessels > Subclavian veins > blood stream
118
Describe lymphatic capillaries.
Tubes of endothelium without continuous basal lamina and tight junction
119
What maintains patency of lymph CAPILLARIES?
Anchoring filaments
120
Is lymph capillary less permeable than blood capillaries?
No, lymph cap. is more permeable
121
Describe lymph VESSELS.
``` Converge from lymph cap. Large lumen Lots of valves Continuous tight junctions Continuous basal lamina surrounded by SM cells ```
122
What 2 mechanisms drive flow of lymphatic vessels?
Adjacent skeletal muscles | Contraction of SM layer surrounding continuous basal lamina of lymph vessels
123
Do venules have 3 layers?
No, only has tunica intima

MBBS I CPRS (78 decks)

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