Histology of the heart and the great vessels

Question 1

What are the three layers of a blood vessel?

Answer 1

Inner: tunica intima

Middle: tunica media

Outer: tunica adventitia

Question 2

Describe the character of the tunica intima?

Answer 2

a single layer of squamous epithelial cells termed endothelial cells supported by a basal lamina and a thin layer of connective tissue

Question 3

Describe the character of the tunica media?

Answer 3

made up predominately of smooth muscle. Thickness of this layer varies tremendously.

Question 4

Describe the character of the tunica adventitia?

Answer 4

made up of supporting connective tissue

Question 5

What separates the tunica intima and tunica media?

Answer 5

by a layer of elastic tissue called the internal elastic membrane

Question 6

What separates the tunica media and tunica adventitia?

Answer 6

layer of elastic tissue called the external elastic membrane.

Question 7

Describe the character of elastic arteries?

Answer 7

Many sheets of elastic fibres which give stretch

elastic expansion and elastic recoil is possible

Question 8

Do elastic arteries have their own vasculature?

Answer 8

Yes, the vaso vasorum

Question 9

What defines an arteriole?

Answer 9

One to two layers of smooth muscle

Question 10

So arterioles have a vascular supply?

Answer 10

Yes

Question 11

Describe the character of capillaries

Answer 11

endothelial cells and basal lamina

no smooth muscle

Question 12

What special cells are found in capillaries?

Answer 12

often have pericytes at intervals just outside the basal lamina

Question 13

What is a pericyte?

Answer 13

connective tissue with contractile properties and stem cell properties

Question 14

What are the three types of capillaries?

Answer 14

continuous

fenestrated

discontinuous

Question 15

Where are continuous capillaries found?

Answer 15

muscle, connective tissue, lung, skin, nerve.

Question 16

Where are fenestrated capillaries found?

Answer 16

mucosa of the gut, endocrine glands, glomeruli of the kidney

Question 17

What do fenestrated capillaries allow for?

Answer 17

pores allow much easier access out of the lumen to surrounding tissue

Question 18

What do discontinuous capillaries allow for?

Answer 18

no basal lamina and large gaps through which macromolecules and cells can pass

Question 19

Where are discontinuous capillaries found?

Answer 19

liver, spleen and bone marrow.

Question 20

Describe the structure of a microvascular network?

Answer 20

feeding arterioles give rise to a metarteriole which give rise to throughfare channels which meet with postcapillary venules and then venules

Question 21

Describe the structure of a post-capillary venule?

Answer 21

lined by endothelial cells

not much if any smooth muscle

occasional pericytes

some smooth muscle when they become venules and definitely when they become veins

Question 22

Describe the structure of veins?

Answer 22

tunica intima, thin tunica media and extensive tunica adventitia

valves prevent backflow

Question 23

What can be found in the walls of large veins?

Answer 23

in the largest veins there is incorporation of longitudinal bundles of smooth muscle in the tunica intima

Question 24

What are the three histological layers of the heart?

Answer 24

1. endocardium inner
2. myocardium middle
3. epicardium outer

Question 25

Describe the structure of endocardium

Answer 25

endothelium

basal lamina

thin layer of collagen fibres

dense connective tissue
o difference is not always clear

sometimes a sub-endocardial space where the conducting cells are going to be incorporated

Question 26

Describe the structure of myocardium

Answer 26

cardiac muscle cells embedded in a fibrous matrix

Bundles and layers of contractile cardiac muscle fibres.

Individual muscle fibres are surrounded by delicate, collagenous connective tissue with a rich network of capillaries.

single central nucleus (sometimes 2)

cardiac muscle cells have to bolt together by intercalated discs

have intercalated discs passing across the fibres at irregular intervals

Question 27

What is the function of the macula adherens and where is it found?

Answer 27

attach intermediate filaments

within the myocardium

Question 28

What is the function of the fascia adherens and where is it found?

Answer 28

They are anchoring sites for actin which connect to the closest sarcomere in the myocardium

Question 29

Describe the structure of epicardium?

Answer 29

single layer of flattened simple squamous cells on the outside

they are mesothelium

there is a basal lamina

fibroelastic connective tissue and extensive adipose tissue in some cases

on the outside of adipose tissue there will still be connective tissue and mesothelium covering the surface

Question 30

Describe the structure of the fibrous pericardium?

Answer 30

sac of tough fibro-collagenous connective tissue

Question 31

Describe the structure of the serous pericardium?

Answer 31

made up of a layer of simple squamous epithelium (termed mesothelium), backed by a basal lamina and connective tissue

Question 32

what does the serous pericardium line?

Answer 32

lines the inner surface of the fibrous pericardium (where it is termed the parietal serous pericardium), and covers the surface of the heart (where it is termed the visceral serous pericardium)

Question 33

What separates the fibrous and serous pericardium?

Answer 33

thin pericardial cavity which contains a small amount (15-50ml) of pericardial fluid that provides lubrication for heart movement

Question 34

What is the fibrous skeleton of the heart formed by?

Answer 34

thick bands of fibrous connective tissue

Question 35

What is the function of the fibrous skeleton of the heart?

Answer 35

supports valves and provides attachment for the cardiac muscle fibres

Question 36

Describe the structure of heart valves?

Answer 36

Have an outer endothelial layer with basal lamina.

Layer of collagen and elastin fibres.

A core of dense connective tissue, called the lamina fibrosa, that is in continuity with the fibrous skeleton.

There are no blood vessels in the valves.

Question 37

What are the mitral and tricuspid valves adhered to?

Answer 37

anchored to papillary muscles in the wall of the ventricle by collagenous strands called the chordae tendineae, which merge with the lamina fibrosa to form a tough anchoring

Question 38

What is the lamina fibrosa?

Answer 38

dense irregular connective tissue that is continuous with the fibrous skeleton

Question 39

What are pacemaker cells and conducting cells?

Answer 39

Modified muscle cells

NOT nerve cells

Question 40

Describe the character or pacemaker cells?

Answer 40

modified cardiac muscle; much smaller, little actin and myosin because contractile force is not their job

appear pale histologically

Question 41

Where do lymph tissues drain to?

Answer 41

veins at the base of the neck

Question 42

Which tissues have no lymphatic vessels?

Answer 42

brain and the bone

Question 43

Describe the structure of lymph vessels

Answer 43

blind ending vessels, anchored in by filaments in the tissue

extremely thin walled, endothelial cell and nothing else

have valves like veins

Question 44

How is flow generated in lymph vessels?

Answer 44

Lymphatic vessels have no central pump, but smooth muscle in walls, hydrostatic pressure in the tissue and compression of the vessels by voluntary muscle, combined with valves in the vessels, produces flow

Question 45

What is the clinical significance of lymph vessels?

Answer 45

the lymph that is draining from the tissue will pass through a lymph node which can monitor antigens coming back from the region, important front-line defence