42 - Cardiovascular Histology

Question 1

Three layers of heart

Answer 1

1) Epicardium 2) Myocardium 3) Endocardium

Question 2

Epicardium

Answer 2

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

Question 3

Myocardium

Answer 3

Cardiac muscle cells and capillaries

Question 4

Endocardium

Answer 4

Endothelial layer, subendocardial connective tissue, conducting tissue.

Question 5

Why is conductive tissue needed for synchronised heart contraction?

Answer 5

Gap junctions only provide local sharing of electric charge.

Question 6

Answer 6

Question 7

Which cell type is this?

Answer 7

Cardiac muscle

Question 8

Conducting pathway through heart

Answer 8

Question 9

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

Answer 9

Purkinje fibres

Question 10

Function of Purkinje fibres

Answer 10

Conduct signals from SA/AV nodes to ventricles

Question 11

Purkinje fibres 1) 2) 3) 4)

Answer 11

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

Question 12

Layers of all blood vessel walls

Answer 12

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

Question 13

Tunica intima 1) 2) 3)

Answer 13

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

Question 14

What is this?

Answer 14

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

Question 15

Roles of the endothelium 1) 2) 3)

Answer 15

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)

Question 16

How is smooth muscle arranged in media?

Answer 16

Concentrically or helically

Question 17

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

Answer 17

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

Question 18

Variation in thickness of tunica media muscle

Answer 18

From one to 40-50 layers

Question 19

Tunica adventitia composition

Answer 19

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

Question 20

Tunica adventita role

Answer 20

Anchor to surrounding connective tissue

Question 21

Name for blood supply of larger vessels

Answer 21

Vaso vasorum. Supplies tunica adventitia.

Question 22

Two types of arteries

Answer 22

Elastic and muscular arteries

Question 23

Location of elastic arteries

Answer 23

Near heart, where the blood pressure fluctuations are highest

Question 24

Effect of elastic arteries

Answer 24

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

Question 25

Role of muscular arteries

Answer 25

Regulate blood pressure, redirect blood to tissues

Question 26

Arterioles 1) 2) 3)

Answer 26

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

Question 27

What gives rise to capillaries?

Answer 27

Arterioles

Question 28

What characterises meta-arterioles?

Answer 28

Incomplete smooth muscle coat

Question 29

What controls capillary flow?

Answer 29

Single smooth muscle cells in meta-arterioles act as sphincters

Question 30

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

Answer 30

Diameter is less than RBC width

Question 31

Distance from a capillary that most cells in the body are

Answer 31

Within 50 micrometers

Question 32

Thickness of arteriolar media

Answer 32

One cell thick

Question 33

Capillary media

Answer 33

No smooth muscle associated with media in capillary wall

Question 34

Structure of a capillary 1) 2) 3)

Answer 34

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)

Question 35

\*Shape of a capillary

Answer 35

Question 36

Fenestrated capillaries 1) 2) 3) 4)

Answer 36

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

Question 37

Difference in structure of veins and arteries

Answer 37

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

Question 38

Why do veins have thicker adventitia than arteries?

Answer 38

Withstand hydrostatic forces

Question 39

Venules function

Answer 39

Blood form capillaries is collected by venules.

Question 40

Structure of venules

Answer 40

Media is initially pericytes, but is replaced by smooth muscle

Question 41

Preferred site of leukocyte diapedesis

Answer 41

Venules

Question 42

What do lymphatic vessels collect?

Answer 42

Extracellular fluid that leaks from veins

Question 43

Structure of lymphatic vessels

Answer 43

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

Question 44

Difference in lymph vessel walls as lymph vessels approach heart

Answer 44

Grow more substantial