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Cardiology > Histology > Flashcards

Histology Flashcards

1
Q

describe the inner layer (tunica intima) of blood vessels?

A
  • single layer of squamous epithelial cells termed endothelial cells
  • supported by a basal lamina and a thin layer of connective tissue
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2
Q

describe the middle layer (tunica media) of blood vessels?

A
  • made up of smooth muscle

- thickness of this layer varies

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3
Q

describe the outer layer (tunica adventitia) of blood vessels?

A
  • made of supporting connective tissue
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4
Q

what separates the tunica intima from the media?

A
  • by a layer of elastic tissue called the internal elastic membrane
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5
Q

what separates the tunica media from the tunica adventitia?

A
  • a layer of elastic tissue called the external elastic membrane
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6
Q

what are elastic arteries?

A
  • eg aorta

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

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7
Q

why do elastic arteries require their own vascular supply? (vasa vasorum)

A
  • in large vessels, only the inner part of the wall can obtain nutrients from the lumen
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8
Q

what is the histology of arterioles?

A
  • 1 or 2 smooth muscle layers in their tunica media

- almost no adventitia

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9
Q

what is the histology of a capillary?

A
  • endothelial cells and a basal lamina
  • they often have pericytes (P) at intervals outside the basal lamina, these are connective tissue cells which have contractile properties
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10
Q

what are the 3 types of capillaries?

A
  • continuous
  • fenestrated
  • sinusoidal or discontinuous
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11
Q

what are continuous capillaries?

A
  • common

- found in muscle, connective tissues, lung, skin, nerve

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12
Q

what are fenestrated capillaries?

A
  • 50nm pores in their walls

- found in mucosa of gut, endocrine glands, glomeruli of kidney

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13
Q

what are sinusoidal or discontinuous capillaries?

A
  • lack a basal lamina and have large gaps in their walls

- found in liver, spleen and bone marrow

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14
Q

what is a microvascular network?

A
  • small arterioles connect to a post capillary venuele though a network made up of metarterioles, throughfare channels and capillaries
  • precapillary sphincters, composed of smooth muscle, at the beginning of the capillary help control flow through the network
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15
Q

what is a postcapillary venule?

A
  • where capillary networks drain into
  • they are endothelial cell-lined and contain a thin layer of connective tissue and occasional pericytes
  • import sites for exchange eg cells moving into the tissue during inflammation
  • once the vessels has intermittent smooth muscle in the tunica media layer they are termed venules
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16
Q

what is the histology of veins?

A
  • tunica intima and media (thin)
  • largest veins (vena cava) have a thick tunica adventitia which incorporates bundles of longitudinally orientated smooth muscle
  • veins are flexible
17
Q

what is the endocardium?

A
  • lines entire inner surface of the heart including valves

- made of endothelium, basal lamina, thin layer of collagen fibres, layer of dense connective tissue

18
Q

what is the subendocardium?

A
  • loose connective tissue containing small blood vessels and nerves and the branches of the impulse conducting system
  • has purkinje fibres
19
Q

what is the myocardium?

A
  • thick middle layer
  • bundles and layers of contractile cardia muscle fibres
  • individual muscle fibres are surrounded by delicate, collagenous connective tissue with a rich network of capillaries
  • cardiac muscle cells have a single central nucleus
  • have intercalated discs passing across the fibers at irregular intervals
20
Q

what is the epicardium?

A
  • outer layer of the heart
  • 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
21
Q

what is the fibrous pericardium?

A
  • a sac of tough fibrocollagenous connective tissue
22
Q

what is the serous pericardium?

A
  • made up of a layer of simple squamous epithelium (mesothelioma) and backed by a basal lamina and connective tissue
  • the serous pricaridum lines the inner surface of the fibrous pericardium (parietal serous pericardium) and covers the surface of the heart (visceral serous pericardium)
23
Q

what is the fibrous skeleton of the heart?

A
  • formed by thick bands of fibrous connective tissues around the heart valves, between the atria and between the ventricles
  • the connective tissue supports the valves but also provides the attachment for the cardiac muslce fibres
24
Q

what is the histology of the heart valves?

A
  • have an outer endothelial layer with basal lamina
  • layer of collagen and elastin fibres
  • a core of dense irreglar connective tissue (lamina fibrosa)
  • the leaflets of the valves separating the atria from the ventricles (mitral and tricuspid) and anchored to papillary muslces in the wall of the ventricles by collagenous strands called the chordae tendineae, which merge with the lamina fibrosa
  • there are no blood vessels in the valves
25
Q

what are the 3 types of cardiac muscle cells?

A
  • contractile cells
  • pacemaker cells
  • conducting cells
26
Q

what are pacemaker cells?

A
  • highly specialised muscle cells
  • smaller than contractile cardiac myocytes
  • embedded in a more extensive matrix of connective tissue
  • pale because of paucity of organelles within them
  • they have a few myofibrils
  • little collagen
    no proper t-tubule system
27
Q

what is an important role of the fibrous skeleton?

A
  • electrically isolating the atria from the ventricles
28
Q

what is the histology of purkinje fibres?

A
  • larger than cardiac muscle cells
  • found in the subendocaridal layer
  • have abundant glycogen, no t-tubules, no intercalated discs,
  • sparse actin and myosin filaments (found at periphery of cells)
  • appear pale
29
Q

what is the role of purkinje fibres?

A
  • to distribute excitatory activity such that the ventricular contraction generally occurs from inferior to superior
30
Q

what is the lymph vascular system?

A
  • thin walled vessels that drain excess interstitial fluid into the blood stream
  • the fluid contains ions, lipids, proteins, cells
  • the lymph passes through lymph nodes providing immunological surveillance
  • lymph vessles have no central pump, but have smooth muscles in walls, hydrostatic pressure in tissues and compression of the vessels by voluntary muscles combined with valves in the vessels, produces flow

Cardiology (40 decks)

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