Cardiovascular Histology

Question 1

What are the three layers of the heart?

Answer 1

Epicardium, myocardium, endocardium

Question 2

What does the epicardium look like histologically?

Answer 2

Simple squamous epithelium at its surface and subepicardial connective tissue with blood vessels, fat and nervous tissue within it. Stains purple. Thin relative to myocardium.

Question 3

What does the myocardium look like histologically?

Answer 3

Cardiac muscle with an abundant blood supply. Not very organised, lots of spaces in between. Stains pink

Question 4

What does the endocardium look like histologically?

Answer 4

An endothelial layer, subendothelial connective tissue, conducting tissue. Thin relative to myocardium and epicardium. Homogenous. Stains purple.

Question 5

What do cardiac muscle cells look like histologically?

Answer 5

Small elongated cells, striated, central nuclei, joined by intercalated discs

Question 6

What is the function of the intercalated disc?

Answer 6

anchors actin filaments in one cell’s sarcomere to sarcomere in another cell via fascia adherents

Question 7

What is the function of gap junctions?

Answer 7

Allows neighbouring cells to coordinate their beating

Question 8

What determines how fast the heart beats?

Answer 8

The heat beats at the rate of the fast beating cardiac muscle cells

Question 9

What makes up the conducting system of the heart?

Answer 9

SA node, AV node, bundle of his, purkinje fibres

Question 10

Where are purkinje fibres found?

Answer 10

In the endocardium against the inner wall of the heart

Question 11

How are purkinje fibres different from other cardiac muscle cells?

Answer 11

They are larger, have limited contractile machinery and are full of glycogen

Question 12

What are the three layers of a blood vessel?

Answer 12

Tunica intima, tunica media, tunica adventitia

Question 13

What is the structure of the intima?

Answer 13

Simple squamous epithelium on basal lamina and a thin layer of subendothelial connective tissue. The endothelial cells are elongated in the direction of blood flow.

Question 14

What is the role of the intima?

Answer 14

Secrete anti-clotting factors on the inner surface and pro clotting factors on the outer surface, and also release substances to signal to the media to contract

Question 15

What is the structure of the media?

Answer 15

Smooth muscle that is arranged concentrically

Question 16

What is special about the media?

Answer 16

The cells behave like fibroblasts and secrete this own extracellular matrix of collagen type III, elastin and ground substance - this may contribute to atherosclerosis

Question 17

What is the structure of the adventitia?

Answer 17

Mostly connective tissue (collagen type I, elastin and ground substance) with embedded fibroblasts, anchors to surrounding tissue, has own blood supply (vaso vasorum)

Question 18

What are the three types of arteries?

Answer 18

Elastic arteries, muscular arteries, arterioles

Question 19

Where are elastic arteries located?

Answer 19

The vessels closest to the heart

Question 20

What is the structure of elastic arteries?

Answer 20

Contains lots of layers of elastin in the media

Question 21

What regulates blood flow into capillaries?

Answer 21

precapillary sphincters - the final smooth muscle of the arteriole

Question 22

What is the structure of capillaries?

Answer 22

A single endothelial cell rolled into a tube and joined end to end, no smooth muscle, basal lamina as a barrier to diffusion, sometimes associated with a pericyte and surrounded by only a few collagen fibres

Question 23

Where to white blood cells exit the vasculature?

Answer 23

Venules

Question 24

What is the structure of veins?

Answer 24

Thicker adventitia to withstand hydrostatic pressure, valves, more connective tissue in subendothelial space, sometimes longitudinal smith muscle

Question 25

What is the structure of lymphatics?

Answer 25

Similar to veins