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MBChB Year 1 Principles Embryology, Histology & Radiology > Histology - Blood and Blood Vessels > Flashcards

Histology - Blood and Blood Vessels Flashcards

1
Q

3 layers of blood vessles

A

Tunica intima, tunica media and tunica adventitia

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2
Q

Tunica intima

A

Single layer, squamous epithelium with a basal lamina and and a thin connective tissue layer

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3
Q

Tunica Media

A

Mostly smooth muscle, varying level of tissue thickness

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4
Q

Tunica Adventitia

A

Supporting connective tissue

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5
Q

Separation of tunica intima and tunica media

A

Internal elastic membrane - layer of elastic tissue

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6
Q

Separation of tunica media and tunica adventitia

A

External elastic membrane - layer of elastic tissue

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7
Q

Staining elastic fibres

A

Not using common stains eg H&E but special ones (not named)

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8
Q

Variation in blood vessel structure

A

In large arteries (eg Aorta) a significant amount of smooth muscle in tunica media is replaced by sheets of elastic fibres - elastic arteries

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9
Q

What is the purpose of ‘Elastic Arteries’

A

To provide elastic recoil

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10
Q

Vascular supply in elastic arteries

A

They have their own vascular supply - ‘vaso vasorum’ as only the inner part of the wall can get nutrients from the lumen

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11
Q

Tissue layers in Arterioles

A

Only one or two layers of smooth muscle in tunica media and miniscule amounts of adventitia

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12
Q

How are arterioles formed?

A

Arteries become smaller losing smooth muscle from tunica media. (they are around 30-200µm)

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13
Q

Why are arterioles important?

A

Help to control blood flow in tissues

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14
Q

Capillaries

A

Composed of endothelial cells and a basal lamina and have diameters of 4-8µm, they also form networks

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15
Q

3 types of capillaries

A

Continuous, fenestrated and discontinuous/sinusoidal

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16
Q

Continuous capillaries

A

An uninterrupted lining which only allows small molecules (eg water to pass)

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17
Q

Location of continuous capillaries

A

Muscle, nerve, lung, skin

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18
Q

Fenestrated capillaries

A

Have small pores (50nm) to allow extensive molecular exchange. more permeable than continuous

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19
Q

Location of fenestrated capillaries

A

Gut mucosa, endocrine glands, kidney

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20
Q

Discontinuous capillaries

A

Have much larger gaps (remember also sinusoids)

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21
Q

Location of discontinuous capillaries

A

Liver, spleen, bone marrow and lymph nodes

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22
Q

Microvasculature

A

(Basically) a small arteriole connected to a postcapillary venule through a network of metarterioles, thoroughfare channels and capillaries.

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23
Q

What is a metarteriole?

A

A short microvessel that links arterioles and capillaries. No continuous tunica media instead spaced smooth muscle that forms a precapillary sphincter.

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24
Q

What is a thoroughfare channel?

A

Links metarterioles to venules. Form arteriovenous anastomoses

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25
Q

Precapillary sphincters and their function

A

(a band of) smooth muscle at the beginning of the capillary to help blood flow

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26
Q

What are post-capillary venules?

A

endothelial lined vessels, containing a thin layer of connective tissue that capillary networks drain into. diameter of 10-30µm.

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27
Q

Why are post-capillary venules important?

A

Sites for exchange eg cells moving into the tissue in inflamation

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28
Q

What are venules?

A

When a vessel begins to acquire intermittent smooth muscle cells in the tunica media (>50µm) - in basic terms a small vein

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29
Q

Composition of veins

A

tunica intima, a thin, continuous tunica media (a few smooth muscle layers) and a large tunica adventitia

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30
Q

Special features of large veins

A

a thick tunica adventitia with bundles of longitudinally oriented smooth muscle

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31
Q

Special features of many small veins

A

valves (formed by an inward extension of tunica intima) to prevent backflow of blood

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32
Q

Structure of the lymph vascular system

A

thin walled vessels. no central pump but smooth muscle in walls, hydrostatic pressure in tissue and compression of tissues by voluntary muscle & valves = flow

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33
Q

Function of lymph vascular system

A

drains excess tissue fluid (lymph) into the . blood stream. transports lymph to lymph nodes for immune surveillance

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34
Q

Where in the body is your blood?

A

The majority is in peripheral veins (around 65%), then heart and lungs (around 20%), peripheral arteries (around 10%) and capillaries (around 5%)

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35
Q

How much of blood is formed elements?

A

45%

36
Q

How much of blood is plasma?

A

55%

37
Q

What 3 types of cells make up formed elements?

A

Red cells, white cells and platelets

38
Q

What are the 2 types of white cells in blood?

A

Granulocytes and Agranulocytes

39
Q

3 types of granulocytes?

A

neutrophils, eosinophils and basophils

40
Q

2 types of agranulocytes?

A

lymphocytes and monocytes

41
Q

What is plasma composed of?

A

water (roughly 90%), proteins, nutrients and salts

42
Q

What are the main proteins in plasma?

A

Albumin, immunoglobulins and clotting factors

43
Q

What is the average adult blood volume?

A

4.5-6 litres

44
Q

What technique is used to separate blood?

A

Centrifugation (in a centrifuge)

45
Q

What factor determines layers in blood separation?

A

Density of components

46
Q

Which is the densest blood component?

A

Red blood cells and are found at the bottom of the tube.

47
Q

Which is the 2nd densest blood component?

A

White blood cells

48
Q

Which is the least dense blood component?

A

Plasma (the liquid portion of blood)

49
Q

What is serum?

A

Blood with its clotting factors removed

50
Q

How is serum obtained?

A

Allow blood to clot and then remove the clot before centrifugation

51
Q

What are erythrocytes?

A

(red blood cells) biconcave discs about 7µm in diameter.

52
Q

Are erythrocytes true cells? reason

A

No as they don’t have a nucleus or any organelles.

53
Q

How much of erythrocytes’ volume is haemoglobin?

A

1/3

54
Q

Structural feature of erythrocytes

A

Flexible cytoskeleton network which allow them to deform and get through spaces smaller than themselves

55
Q

Lifespan of erythrocytes

A

Last approx 4 months and then are removed (usually) by the spleen and liver.

56
Q

What is a leukocyte?

A

White blood cell

57
Q

Proportion of leukocyte cell types

A 
neutrophils (40-75%)
eosinphils (5%)
basophils (0.5%)
lymphocytes (20-50%)
monocytes (1-5%)
58
Q

Neutrophils structure

A

many granules in the cytoplasm but they don’t stain well with acidic or basic dyes = neutro. multi lobed nucleus

59
Q

Role of neutrophils

A

are inactive in circulation until stimulated (eg by presence of bacteria or inflammation) when they enter tissue with high motile phagocytes

60
Q

Life of neutrophils

A

They are abundant and short lived so lots of bone marrow is dedicated to their production.

61
Q

Eosinophils structure

A

Prominent granules with an affinity for red acidic dye (eosin), slightly larger that neutrophils and have a bilobed nucleus.

62
Q

Life of eosinophils

A

released from marrow, circulate for 8-12 hours then move into tissue (usually spleen, lymph nodes and GI tract) to live.

63
Q

Role of eosinophils

A

induce and maintain inflammation (especially in allergic reaction and asthma) as their granules contain a variety of hydrolytic enzymes. they also help fight parasitic infection.

64
Q

Structure of Basophils

A

prominent granules have a high affinity for basic dyes (eg methylene blue) so stain blue/purple. bilobed nucleus (often obscured by granules)

65
Q

What components are in basophils’ granules?

A

histamine, heparin and other inflammatory mediators

66
Q

Function of basophils

A

Effector cells in allergic reactions. high affinity IgE receptors in the membrane are directed against a specific antigen so when it binds to that antigen the cell is stimulated to degranulate. this causes hayfever, allergic asthma, allergic dermatitis etc

67
Q

Structure of monocytes

A

many small lysosomal granules in their cytoplasm. largest cells in blood circulation and have a non-lobulated nucleus (looks like a kidney bean)

68
Q

Function of monocytes

A

precursors of macrophages and together they form the mononuclear phagocyte system. macrophages are all over the body but mainly in loose connective tissue.

69
Q

Distribution of the mononuclear phagocyte system

A

Many move all around the body but some stay resident in a specific tissue eg Kupffer cells in the liver, microglia in the brain and Langerhan’s cells in the skin

70
Q

Structure of lymphocytes

A

Round nucleus with a thin/moderate rim of cytoplasm. no visible granules.

71
Q

How many classes of lymphocyte are there?

A

2 - B cells and T cells

72
Q

How do you differentiate between T and B cells in routine staining?

A

You can’t.

73
Q

Where are B and T cells made?

A

Bone marrow

74
Q

Where do T cells differentiate?

A

Thymus (lymphoid organ in the immune system)

75
Q

What is B cells function?

A

Specific immune response - give rise to antibody secreting plasma cells

76
Q

What is the function of T cells?

A

Specific immune response - form a complex set of cells to perform defence functions (aid other immune cells, kill defective cells etc)

77
Q

Structure of platelets

A

small cell fragments, about 2µm in length with a well developed cytoskeleton which is important in extruding granules and retracting clots. they have visible granules that contain (alongside others) coagulation factors. they have some organells but no nucleus

78
Q

Function of platelets

A

have a key role in preventing blood loss ( hemostatis)

79
Q

What is hemopoiesis?

A

The process of making blood from stem cells in bone marrow

80
Q

Where does hemopoiesis happen during fetal development?

A

(Principally) the liver and occasionally the spleen

81
Q

Where does hemopoiesis happen at birth?

A

The bone marrow, all bones participate. as bones grow there is excess capacity so hemopoiesis is shut down in many bones.

82
Q

Where does hemopoiesis happen at skeletal maturity?

A

The vertebrae, ribs, skull, pelvis and proximal femurs.

83
Q

What is the marrow not being used for hemopoiesis used for?

A

Mainly adipose (fatty) tissue however in emergencies it can revert to blood formation

84
Q

Megakaryocytes’ function

A

Large (30-100µm) cells of bone marrow that produce platelets.

85
Q

Duplication of megakaryocytes

A

its nuclear material is duplicated but it doesn’t actually undergo nuclear or cell division - ie very large nucleus. Platelets are essentially the extensions at the cells outer margin which fragments as it grows larger.

MBChB Year 1 Principles Embryology, Histology & Radiology (5 decks)

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