Histology

Question 1

what are the three basic layers of blood vessels?

Answer 1

Inner layer - tunica intima
middle layer - tunica media
outer layer - tunica adventitia

Question 2

what is the inner layer of blood vessels made of?

Answer 2

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

Question 3

what is the middle layer of blood vessels made of?

Answer 3

smooth muscle. thickness varies.

Question 4

what is the outer layer of blood vessels made of?

Answer 4

made up of supporting connective tissue.

Question 5

what is the tunica intima and tunica media separated by?

Answer 5

a layer of elastic tissue called the internal elastic membrane.

Question 6

what is the tunica media and tunica adventitia separated by?

Answer 6

a layer of elastic tissue called the external elastic membrane.

Question 7

what are the largest arteries (e.g. aorta) termed? and why?

Answer 7

elastic arteries, because they have many sheets of elastic fibres in their tunica media to provide elastic recoil.

Question 8

In large vessels, only the inner part of the wall can obtain nutrients from the lumen, therefore some those vessels will have to have their own supply, what is it called?

Answer 8

vasa vasorum

Question 9

how many layers of smooth muscle do arterioles have in their tunica media?

Answer 9

one or two.

Question 10

what are capillaries composed of?

Answer 10

endothelial cells and a basal lamina

Question 11

what do capillaries often have at intervals just outside the basal lamina? what are they?

Answer 11

pericytes - connective tissue cells that have contractile properties.

Question 12

what are the three different types of capillaries?

Answer 12

continuous capillaries
fenestrated capillaries
sinusoidal or discontinuous capillaries

Question 13

what are the properties of the three types of capillaries?

Answer 13

• continuous capillaries are more common
• fenestrated capillaries have approx 50nm pore in walls
• sinusoidal capillaries lack a basal lamina and have large gaps through which macromolecules and in some cases even cells, can pass.

Question 14

where can the three types of capillaries be found?

Answer 14

• continuous capillaries - muscle, connective tissue, lung, skin, nerve
• fenestrated capillaries - mucosa of the gut, endocrine glands, glomeruli of the kidney.
• sinusoidal capillaries - liver, spleen and bone marrow.

Question 15

what are post-capillary venules?

Answer 15

capillary networks drain into them. they are endothelial cell-lined and contain a thin layer of connective tissue and occasional pericytes. these are important sites for exchange e.g. cells moving into the tissue in inflammation.

Question 16

when are vessels referred to as venules?

Answer 16

once they begin to acquire intermittent smooth muscle cells in their tunica media layer.

Question 17

what are the properties of veins?

Answer 17

have a tunica intima, a relatively thin but continous tunica media typically consisting of a few layers of smooth muscle. the tunica media is markedly thinner than would be found in a muscular artery.

Question 18

what type of vessel contains most of the blood in the body?

Answer 18

vein

Question 19

what are the three layers of the heart?

Answer 19

endocardium - inner layer
myocardium - middle layer
epicardium - outer layer

Question 20

what is the structure of the endocardium?

Answer 20

endothelium
basal lamina
thin layer of collagen fibres
layer of denser connective tissue.

Question 21

what is a subendocardium?

Answer 21

loose connective tissue containing small blood vessels and nerves and the branches of the impulse conducting system.

Question 22

what is the structure of the myocardium?

Answer 22

bundles and layers of contractile cardiac muscle fibres.

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

Question 23

what do intercalated discs passing across the fibres in the myocardium do?

Answer 23

acts to attach cells but also allows spread of electrical activity.

Question 24

what is the epicardium?

Answer 24

a single layer of flattened epithelium called mesothelium.

Question 25

apart from mesothelium what else does the epicardium contain?

Answer 25

basal lamina

fibroelastic connective tissue and in some places adipose tissue.

Question 26

what are the two parts of the pericardium?

Answer 26

fibrous and serous pericardium

Question 27

what is the fibrous pericardium?

Answer 27

a sac of tough fibrocollagenous connective tissue

Question 28

what is the serous pericardium?

Answer 28

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

Question 29

what is the serous pericardium which lines the inner surface of the fibrous pericardium called?

Answer 29

parietal serous pericardium

Question 30

what is the serous pericardium which lines the heart called?

Answer 30

visceral serous pericardium

Question 31

what is the parietal and visceral serous pericardium separated by?

Answer 31

pericardial cavity - which contains a small amount of pericardial fluid that provides lubrication for the heart movement.

Question 32

what is the heart fibrous ‘skeleton’ formed from?

Answer 32

thick bands of fibrous connective tissue around the heart valves, between the atria and between the ventricles.

Question 33

what does the heart fibrous ‘skeleton’ provide?

Answer 33

supports the valves and provides attachment for the cardiac muscle fibres.

Question 34

what is the structure of heart valves?

Answer 34

• have an outer endothelial layer with basal lamina.
• layer of collagen and elastic fibres.
• a core of dense connective tissue called the lamina fibrosa, that is in continuity with the fibrous skeleton.

Question 35

what are the leaflets of valves separating the atria and ventricles anchored by?

Answer 35

papillary muscles in the wall of the ventricle by collagenous strands called the chordae tendinaea, which merge with the lamina fibrosa.

Question 36

what do heart valves not have?

Answer 36

blood vessels

Question 37

what are the three types of cardiac muscle cells?

Answer 37

contractile cells
pacemaker cells
conducting cells