Microanatomy Flashcards

1
Q

Organization of blood vessels

A
  • From lumen out: tunica intima, tunica media, tunica adventitia, vasa vasorum (part of adventitia)
  • Arteries have large tunica media and veins have large tunica adventitia
  • Internal elastic lamina (IEL) separates intima and media (part of intima)
  • External elastic lamina (EEL) separates media and adventitia (part of media)
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2
Q

Tunica intima

A
  • Inner most layer consisting of endothelium and its basal lamina, sub endothelial CT (may contain smooth muscle), and IEL (arteries only)
  • Smallest layer
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3
Q

Tunica media

A
  • Middle layer composed of circumferential smooth muscle (major site for SM), which secrete elastin and collagen, and there may be EEL
  • Largest layer in arteries, mostly SM
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4
Q

Tunica adventitia

A
  • Outer layer composed of collagen (T1) and elastic fibers to anchor to surrounding CT
  • Contains vasa vasorum (small arteries that supply blood to the vessel itself)
  • Largest layer in veins, mostly CT
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5
Q

Layers of the heart 1

A
  • From in-> out: Endocardium, myocardium, epicardium (AKA visceral pericardium), parietal pericardium, fibrous pericardium
  • Endocardium: inside of the heart (where blood is) lined by endothelium (w/ BL) and subendothelial CT. Contains purkinje fibers (modified cardiac muscle) and valves (core of DCT surrounded by endothelium)
  • Myocardium: very abundant cardiac muscle cells, inserting in the fibrous cardiac skeleton (part of myocardium, separates atria from ventricles)
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6
Q

Layers of the heart 2

A
  • Epicardium: outer most layer (synonymous w/ visceral pericardium) composed of mesothelium (simple squamous epithelial layer w/ BL) and LCT
  • The LCT of epicardium contains coronary vessels, nerves, ganglia, and fat
  • Outside of the visceral pericardium is the parietal pericardium, together w/ the visceral pericardium forms the serous pericardium (w/ serous fluid btwn them)
  • The entire structure is enclosed in the fibrous pericardium
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7
Q

Conducting arteries

A
  • Conducting (largest) arteries: aorta and its large branches responsible for maintaining a constant BP
  • Thin IEL and EEL, but thick tunica media consisting of SM and elastic fibers
  • Have thin adventitia w/ vasa vasorum (+ lymphatic vessels and nerves)
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8
Q

Muscular arteries

A
  • Muscular (distributing) arteries display thick tunica media and adventitia w/ scalloped (crescent) lumen
  • Contain thick IEL and thin EEL, with the size of media (SM) and adventitia (fibroelastic CT) being about equal
  • Adventitia may or may not have vasa vasorum
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9
Q

Arterioles

A
  • Arterioles: Smallest arterial vessels, control BP
  • Walls are as thick as the diameter of lumen
  • Intima shows endothelial nuclei bulging into lumen, may or may not have IEL (larger ones do)
  • One to several layers of SM in media, +/- EEL
  • Adventitia is very thin
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10
Q

Capillaries

A
  • Continuous: nonporous endothelial cells w/ tight junction btwn them and complete BL (no leakage)
  • Form BBB and BNB
  • Fenestrated: capillaries w/ opening to facilitate transport (may be covered by diaphragm to monitor the permeability of pores), w/ continuous BL (some leakage)
  • Discontinuous: have wide lumens and large spaces within the capillary (btwn endothelial cells) for most rapid transportation
  • Have discontinuous BL and and fenestrated endothelial cells (found in BM)
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11
Q

Venules

A
  • Post-capillary venules: principal site of action of vasoactive agents (?), no tunica media or adventitia (highly permeable)
  • Site of lymphocyte homing
  • Musclular venules: similar to post-capillary venues but contain very thin media and adventitia
  • Site of lymphocyte diapedesis/extravasation
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12
Q

Veins

A
  • Small veins: tunica intima contains few valves +/- IEL, thin media and thick adventitia +/- vasa vasorum
  • Large veins: thick intima w/ IEL, vlaves, and subendothelial CT, thin media w/ little EEL, thick adventitia w/ vasa vasorum and some SMCs
  • Compared to arteries, veins have larger lumen, thinner walls and are often collapsed in histological sections
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13
Q

Lymphatic vessels

A
  • Blind-ended tubes lined w/ endothelium w/ large spaces and discontinuous BL
  • Allows for transport of larger solutes into lymphatics
  • No tunica media or adventitia for lymphatic capillaries
  • Lymphatic vessels have thin media (some SMCs) and adventitia (vasa vasorum)
  • Vessels empty into ducts (thoracic duct on L or R lymphatic duct) where subclavian + IJV meet
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