L28 – Histology and Functions of Blood Vessels Flashcards Preview

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Flashcards in L28 – Histology and Functions of Blood Vessels Deck (123):
1

What 3 things make up the circulatory system?

Heart, Blood vessels, Lymphatic vessels

2

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

- Transport blood, nutrient, gases, waste

- Maintains and regulates blood flow and BP

- Protect body from infection

- Thermoregulation

-Maintain fluid balance

3

What are 3 categories of blood vessels?

arteries, veins, capillaries

4

What are the layers of blood vessels and heart?

Heart: Endocardium, Myocardium, Epicardium

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

5

3 layers to heart endocardium?

1) endothelium : simple squamous w/ basment membrane

2) sub-endothelial layer of loose connective tissue and smooth muscle cells

3) Subendocardium

6

What is contained in subendocardium inside endocardium?

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

7

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

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

8

What is the purpose of subendocardium?

Connects endocardium to myocardium

9

What is special about heart valve endocardium?

heart valves = extensions of endocardium

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

10

What 2 things are found in Myocardium?

Cardiac muscle, extensive vasculature

11

How are myocytes in myocardium arranged?

Layers of spirally-arranged cardiac muscle fibers

12

Is cardiac myocyte branched or not?

Branched (unlike skeletal muscle )

13

What are the types of cell junctions in cardiac myocyte?

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

1. Gap junctions
2. Adherens junctions
3. Desmosomes

14

What are myocardium myocytes organised into?

Fascicles

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

15

What is the tissue type in epicardium?

fibroelastic loose connective tissue

16

What is another name for epicardium?

Serous pericardium

17

What epithelium covers epicardium? What does it do?

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

18

What are the components to epicardium?

fibroelastic loose connective tissue

nerves

adipose tissue

19

What is Between visceral and parietal layer of serous
pericardium?

pericardial cavity

20

What is the outermost pericardium? made of?

fibrous pericardium

adipose tissue

21

What are the 3 layers of heart valves?

(Endothelium)
Spongiosa
Fibrosa
Ventricularis
(Endothelium)

22

What tissue makes up heart valve spongiosa layer?

Loose connective tissue (loosely arranged collagen and elastic fibers)

covered by endothelium

23

What tissue makes up Fibrosa layer of heart valves?

Dense Irregular connective tissue

Fibres extend from cardiac skeleton

24

What tissue makes up Ventricularis of heart valves?

Dense connective tissue covered by endothelium

Many layers of elastic fibres

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

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