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)
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
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
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
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)
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
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)
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
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
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)
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
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
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