Histology of the CV system Flashcards
what is the fibrous pericardium?
= 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
what are the 2 different layers of the serous pericardium?
- parietal pericardium — adheres to the inside of the fibrous pericardium
- visceral pericardium — adheres tightly to the surface of the heart
what does the pericardial cavity contain? function?
tissue fluid — allows heart to move without any friction
describe the 3 layers of the heart wall
- endocardium = inner layer - endothelium
- myocardium = middle layer - thickest - cardiac muscle
- epicardium = outer layer - visceral pericardium
what do the coronary vessels run within?
the epicardium
what does the epicardium contain various amounts of?
fat
name 4 features of cardiac muscle
- branched fibres
- centrally located nuclei
- up to 5 nuclei per fibre
- intercalated discs between fibres
why type of epithelium is present in the endocardium?
simple squamous epithelium
what do nerves and vessels run through?
loose connective tissue over the visceral epicardium
what can be seen in this heart valve?
single layer of simple squamous epithelium and a core of dense connective tissue
are purkinje fibres contractile or non-contractile?
non-contractile
which arteries are elastic and why?
aorta and its large branches — stabilise blood flow so must be able to withstand fluctuations in pressure
arteries vs veins
artery:
- has a thicker wall
- appears to have a smaller lumen
- maintains its shape
- is more resilient
- does not have valves
why do veins contain valves?
prevent backflow of blood
what are the 3 layers of blood vessels?
- tunica intima
- tunica media
- tunica adventitia (externa)
describe the tunica intima of blood vessels
- endothelium
- lined with simple squamous epithelium
- basal lamina
- subendothelial connective tissue
describe the tunica media of blood vessels
muscle layer
describe the tunica adventitia of blood vessels
- connective tissue
- +/- vasa vasorum (in large vessels — supply the vessel itself)
describe and give examples of elastic arteries
- aorta
- brachiocephalic
- common carotid
- subclavian
- diameter up to 2.5 cm
- must withstand changes in pressure and ensure continuous blood flow
adaptations of elastic arteries?
thick tunica media with many elastic fibres and few smooth muscles cells
describe large veins + example
- vena cava
- low pressure system
- easily distension (capacitance)
structural adaptations of large veins?
- thin walled
- narrow tunica intima
- several layers of smooth muscle in tunica media
- thick tunica externa
- may possess valves to aid blood flow
superior and inferior vena cava adaptations
- distinct tunica intima — fibroelastic
- narrow tunica media
- thick adventitia — collagen and smooth muscle fibres
what are muscular arteries capable of and why is this important?
capable of vasodilation and vasoconstriction in order to control the rate of blood floe to suit the needs of the organ
structural adaptations of muscular arteries?
- smooth muscle cells +++ in tunica media
- distinct internal (IEL) and external (EEL) elastic laminae
- thick tunica externa
structural adaptations of small and medium veins?
- thin walled
- tunica externa is predominant
are small and medium veins easily distensible or not
they are easily distensible
