Histology of the CV system

Question 1

what is the fibrous pericardium?

Answer 1

= inelastic sac of dense connective tissue

• fuses inferiorly with the diaphragm and superiorly with the great vessels
• prevents overfilling of heart and anchors the heart in position

Question 2

what are the 2 different layers of the serous pericardium?

Answer 2

• parietal pericardium — adheres to the inside of the fibrous pericardium
• visceral pericardium — adheres tightly to the surface of the heart

Question 3

what does the pericardial cavity contain? function?

Answer 3

tissue fluid — allows heart to move without any friction

Question 4

describe the 3 layers of the heart wall

Answer 4

1. endocardium = inner layer - endothelium
2. myocardium = middle layer - thickest - cardiac muscle
3. epicardium = outer layer - visceral pericardium

Question 5

what do the coronary vessels run within?

Answer 5

the epicardium

Question 6

what does the epicardium contain various amounts of?

Answer 6

fat

Question 7

name 4 features of cardiac muscle

Answer 7

• branched fibres
• centrally located nuclei
• up to 5 nuclei per fibre
• intercalated discs between fibres

Question 8

why type of epithelium is present in the endocardium?

Answer 8

simple squamous epithelium

Question 9

what do nerves and vessels run through?

Answer 9

loose connective tissue over the visceral epicardium

Question 10

what can be seen in this heart valve?

Answer 10

single layer of simple squamous epithelium and a core of dense connective tissue

Question 11

are purkinje fibres contractile or non-contractile?

Answer 11

non-contractile

Question 12

which arteries are elastic and why?

Answer 12

aorta and its large branches — stabilise blood flow so must be able to withstand fluctuations in pressure

Question 13

arteries vs veins

Answer 13

artery:

• has a thicker wall
• appears to have a smaller lumen
• maintains its shape
• is more resilient
• does not have valves

Question 14

why do veins contain valves?

Answer 14

prevent backflow of blood

Question 15

what are the 3 layers of blood vessels?

Answer 15

1. tunica intima
2. tunica media
3. tunica adventitia (externa)

Question 16

describe the tunica intima of blood vessels

Answer 16

• endothelium
• lined with simple squamous epithelium
• basal lamina
• subendothelial connective tissue

Question 17

describe the tunica media of blood vessels

Answer 17

muscle layer

Question 18

describe the tunica adventitia of blood vessels

Answer 18

• connective tissue

- +/- vasa vasorum (in large vessels — supply the vessel itself)

Question 19

describe and give examples of elastic arteries

Answer 19

• aorta
• brachiocephalic
• common carotid
• subclavian
• diameter up to 2.5 cm
• must withstand changes in pressure and ensure continuous blood flow

Question 20

adaptations of elastic arteries?

Answer 20

thick tunica media with many elastic fibres and few smooth muscles cells

Question 21

describe large veins + example

Answer 21

• vena cava
• low pressure system
• easily distension (capacitance)

Question 22

structural adaptations of large veins?

Answer 22

• thin walled
• narrow tunica intima
• several layers of smooth muscle in tunica media
• thick tunica externa
• may possess valves to aid blood flow

Question 23

superior and inferior vena cava adaptations

Answer 23

• distinct tunica intima — fibroelastic
• narrow tunica media
• thick adventitia — collagen and smooth muscle fibres

Question 24

what are muscular arteries capable of and why is this important?

Answer 24

capable of vasodilation and vasoconstriction in order to control the rate of blood floe to suit the needs of the organ

Question 25

structural adaptations of muscular arteries?

Answer 25

• smooth muscle cells +++ in tunica media
• distinct internal (IEL) and external (EEL) elastic laminae
• thick tunica externa

Question 26

structural adaptations of small and medium veins?

Answer 26

• thin walled

- tunica externa is predominant

Question 27

are small and medium veins easily distensible or not

Answer 27

they are easily distensible