Histology

Question 1

what are the 3 layers of the blood vessels?

Answer 1

tunica intima
tunica media
tunica adventitia

Question 2

describe the tunica intima

Answer 2

inner layer
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 tunica media

Answer 3

middle layer
made up predominantly of smooth muscle
thickness can vary

Question 4

describe the tunica adventitia

Answer 4

outer layer

made up of supporting connective tissue

Question 5

what is the internal elastic membrane?

Answer 5

a layer of elastic tissue which operates the tunica intima from the tunica media

Question 6

what is the external elastic membrane?

Answer 6

a layer of elastic tissue which separates the tunica media from the tunica adventitia

Question 7

why are the largest arteries termed elastic arteries?

Answer 7

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

Question 8

what is the vasa vasorum?

Answer 8

the vascular supply for large vessels as only the inner part of the wall can obtain nutrients from the lumen

Question 9

describe the structure of arterioles

Answer 9

only one or two layers of smooth muscle in their tunica media and almost no adventitia

Question 10

describe the structure of capillaries

Answer 10

essentially composed of endothelial cells and a basal lamina
sometimes have pericytes at intervals just outside the basal lamina

Question 11

what are pericytes?

Answer 11

connective tissue cells that have contractile properties

Question 12

what are the 3 types of capillaries?

Answer 12

continuous
fenestrated
sinusoidal or discontinuous

Question 13

where are continuous capillaries found?

Answer 13

muscle 
connective tissue 
lung 
skin 
nerve

Question 14

describe fenestrated capillaries

Answer 14

have small pores in walls

Question 15

where are fenestrated capillaries found?

Answer 15

mucosa of the gut
endocrine glands
glomeruli of the kidney

Question 16

describe sinusoidal or discontinuous capillaries

Answer 16

lack a basal lamina and have large gaps through which macromolecules can in some cases, even cells, can pass

Question 17

where are sinusoidal or discontinuous capillaries found?

Answer 17

liver
spleen
bone marrow

Question 18

describe the microvasculature

Answer 18

small arterioles connect to a post capillary venule through a network made up of metarterioles, channels and capillaries
precapillary sphincters, composed of smooth muscle, at the beginning of the capillary help control flow through the network

Question 19

describe post capillary venules

Answer 19

endothelial cell lined and contain a thin layer of connective tissue and occasional pericytes

Question 20

what is the role of post capillary venules?

Answer 20

important sites for exchange eg cells moving into the tissue in inflammation

Question 21

describe veins

Answer 21

have a tunica intima and a tunica media consisting of a few layers of smooth muscle
the tunica media is thinner than what would be found in an artery
large veins have a thick tunica adventitia which incorporates bundles of longitudinally orientated smooth muscle
flexible and can accommodate expansion

Question 22

what are valves in veins?

Answer 22

inward extensions of the tunica intima in most small to medium veins

Question 23

what are the 3 layers of the heart?

Answer 23

endocardium
myocardium
epicardium

Question 24

what is the endocardium?

Answer 24

inner layer

lines the entire surface of the heart, including the valves

Question 25

describe the structure of the endocardium

Answer 25

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

Question 26

what is the subendocardium?

Answer 26

in some areas of the endocardium, it is a loose connective tissue containing small blood vessels and nerves and the branches of the impulse conducting system

Question 27

what is the myocardium?

Answer 27

thick middle layer of the heart

Question 28

describe the structure of the myocardium

Answer 28

bundles and layers of contractile cardiac muscle fibres | individual muscle fibres are surrounded by delicate, collagenous connective tissue with a network of capillaries

Question 29

describe cardiac muscle cells

Answer 29

a single central nucleus (sometimes 2) | have intercalated discs passing across the fibres at irregular intervals

Question 30

what is the role of the intercalated discs in cardiac muscle cells?

Answer 30

act to attach cells and allows spread of electrical activity

Question 31

what is the epicardium?

Answer 31

outer layer of the heart

Question 32

describe the structure of the epicardium

Answer 32

on the surface of the heart: a single layer of flattened epithelium called mesothelium basal lamina fibroelastic connective tissue and, in some places, adipose tissue

Question 33

what are the two layers of the pericardium?

Answer 33

fibrous pericardium | serous pericardium

Question 34

describe the fibrous pericardium

Answer 34

a sac of tough fibrocollagenous connective tissue

Question 35

what does the serous pericardium do?

Answer 35

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 36

describe the serous pericardium

Answer 36

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

Question 37

describe the pericardial cavity

Answer 37

separates the two layers of the pericardium and contains a small amount of pericardial fluid which provides lubrication for heart movement

Question 38

what is the role of the fibrous skeleton of the heart?

Answer 38

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

Question 39

describe the fibrous skeleton of the heart

Answer 39

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

Question 40

describe the structure of the heart valves

Answer 40

outer endothelial layer with basal lamina a layer of collagen and elastin fibres lamina fibrosa the leaflets of the valves separating the atria from the ventricles (mitral and tricuspid) are anchored to papillary muscles in the wall of the ventricle by collagenous strands called the chord tendinea, which merges with the lamina fibrosa

Question 41

describe the lamina fibrosa

Answer 41

a core of dense connective tissue, that is in continuity with the fibrous skeleton

Question 42

what are the 3 types of cardiac muscle cells?

Answer 42

contractile cells pacemaker cells conducting cells

Question 43

describe pacemaker cells

Answer 43

highly specialised muscle cells smaller than contractile cardiac myocytes and embedded in a more extensive matrix of connective tissue they appear pale because of the paucity of organelles within them few myofibrils, little glycogen and no proper T-tubule system

Question 44

describe purkinje fibres

Answer 44

larger than normal cardiac muscle cells abundant glycogen no T-tubules no intercalated discs sparse actin and myosin filaments appear pale and have a very pale/clear centre

Question 45

where can purkinje fibres be found?

Answer 45

in the subendocardial layer just deep to the endocardium

Question 46

describe the lymph vascular system

Answer 46

a system of relatively thin walled vessels that drain excess fluid (lymph) into the blood stream along the way the lymph passes through lymph nodes, providing for immunological surveillance

Question 47

describe the interstitial fluid of the lymph vascular system

Answer 47

it contains ions, lipids, proteins and occasional cells most returns to capillaries and venous vessels but some returns to the circulatory system by entering the lymphatic vessels

Question 48

describe lymphatic vessels

Answer 48

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