42 - Cardiovascular Histology Flashcards

1
Q

Three layers of heart

A

1) Epicardium 2) Myocardium 3) Endocardium

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2
Q

Epicardium

A

Simple squamous epithelium lies on top of a lot of connective tissue. Blood vessels, fat, nervous tissue in this layer.

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3
Q

Myocardium

A

Cardiac muscle cells and capillaries

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4
Q

Endocardium

A

Endothelial layer, subendocardial connective tissue, conducting tissue.

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5
Q

Why is conductive tissue needed for synchronised heart contraction?

A

Gap junctions only provide local sharing of electric charge.

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6
Q
A
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7
Q

Which cell type is this?

A

Cardiac muscle

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8
Q

Conducting pathway through heart

A
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9
Q

How is the contraction of different heart chambers co-ordinated?

A

Purkinje fibres

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10
Q

Function of Purkinje fibres

A

Conduct signals from SA/AV nodes to ventricles

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11
Q

Purkinje fibres 1) 2) 3) 4)

A

1) Modified cardiac myocytes 2) Limited contractile machinery 3) Full of glycogen 4) Form bundles in subendocardium

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12
Q

Layers of all blood vessel walls

A

1) Tunica intima 2) Tunica media 3) Tunica adventitia

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13
Q

Tunica intima 1) 2) 3)

A

1) Lined with simple squamous epithelium 2) Epithelium lies on basal lamina 3) Supported by a thin subendothelial layer

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14
Q

What is this?

A

Tunica intima of a blood vessel. Note how, as the blood vessel is not full of blood, the endothelial cells bulge into lumen. When blood vessel is full, endothelial cells are taught

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15
Q

Roles of the endothelium 1) 2) 3)

A

1) Actively inhibit clotting by secreting inhibitors (EG: prostacyclin) 2) Prime underlying subendothelial tissue with Von Willebrand factor for clotting 3) Release vasoactive substances to smooth muscle like NO (vasodilatory), endothelin (strongly vasocontrictive)

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16
Q

How is smooth muscle arranged in media?

A

Concentrically or helically

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17
Q

Where does the connective tissue of the tunica media come from?

A

Secreted by smooth muscle. Collagen type III, elastin, ground substance.

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18
Q

Variation in thickness of tunica media muscle

A

From one to 40-50 layers

19
Q

Tunica adventitia composition

A

Type I collagen, elastin, ground substance. Fibroblasts,.

20
Q

Tunica adventita role

A

Anchor to surrounding connective tissue

21
Q

Name for blood supply of larger vessels

A

Vaso vasorum. Supplies tunica adventitia.

22
Q

Two types of arteries

A

Elastic and muscular arteries

23
Q

Location of elastic arteries

A

Near heart, where the blood pressure fluctuations are highest

24
Q

Effect of elastic arteries

A

Ensures continuous, pulsatile blood flow. Means that blood flow doesn’t cease during diastole

25
Q

Role of muscular arteries

A

Regulate blood pressure, redirect blood to tissues

26
Q

Arterioles 1) 2) 3)

A

1) Very small arteries with diameter less than 0.1mm 2) Between 1-3 layers of smooth muscle 3) Contribute most to blood pressure changes

27
Q

What gives rise to capillaries?

A

Arterioles

28
Q

What characterises meta-arterioles?

A

Incomplete smooth muscle coat

29
Q

What controls capillary flow?

A

Single smooth muscle cells in meta-arterioles act as sphincters

30
Q

How do capillaries ensure that there is good contact between RBC and capillary endothelium

A

Diameter is less than RBC width

31
Q

Distance from a capillary that most cells in the body are

A

Within 50 micrometers

32
Q

Thickness of arteriolar media

A

One cell thick

33
Q

Capillary media

A

No smooth muscle associated with media in capillary wall

34
Q

Structure of a capillary 1) 2) 3)

A

1) Single epithelial cell rolled into a tube, with tight junctions. 2) Sometimes associated with a pericyte (media) 3) Surrounded by only a few collagen fibres (adventitia)

35
Q

*Shape of a capillary

A
36
Q

Fenestrated capillaries 1) 2) 3) 4)

A

1) Capillaries with holes (fenestrations) in the walls. 2) Fenestrations are often covered diaphragms. 3) Found in pancreas, intestines, endocrine glands, kidneys. 4) For fast transport of things in blood

37
Q

Difference in structure of veins and arteries

A

Media of veins is thinner, adventitia is thicker than arteries. Veins have valves

38
Q

Why do veins have thicker adventitia than arteries?

A

Withstand hydrostatic forces

39
Q

Venules function

A

Blood form capillaries is collected by venules.

40
Q

Structure of venules

A

Media is initially pericytes, but is replaced by smooth muscle

41
Q

Preferred site of leukocyte diapedesis

A

Venules

42
Q

What do lymphatic vessels collect?

A

Extracellular fluid that leaks from veins

43
Q

Structure of lymphatic vessels

A

Have valves. Have gaps in walls to let in extracellular fluid. Have absence of red cells. Some leukocytes are present

44
Q

Difference in lymph vessel walls as lymph vessels approach heart

A

Grow more substantial