Blood and Nerves Flashcards
1
Q
Structure of Arteries
A
- Lumen-channel which blood flows.
- Bounded by squamous endothelium cells which rest on basement membrane.
- Surrounded by thin layer loose ct called intima.
- Intima bound by layer of elastic tissue-internal elastic lamina.
- When media becomes filled with elastic sheets, prominence of elastic lamina diminishes.
- Around this there is thick layer of ct- comprising of smooth muscle and some fibroblast and varying amounts of collagen and elastin. This is media of blood vessel.
- Surrounded on outer surface by another layer of elastic tissue- external elastic lamina.
- Layer of loose connective tissue called Adventitia.
2
Q
Elastic Arteries
A
- Large arteries near the heart e.g. aorta, pulmonary arteries.
- Media contains abundant concentric sheets of elastin. Seen in this pic as red lines.
3
Q
Muscular Arteries
A
Muscular arteries:
- Most arteries in the body aren’t elastic they are muscular.
- Media comprises layers of smooth muscle.
- Little elastin in media
- e.g. radial artery in wrist and splenic artery.
4
Q
Arterioles
A
- Resistance vessels
- Arbitrarily defines as having 3 or fewer muscle layers in their media
- Up to 100um diameter
- Elastic laminae poorly defined but with special; stains can be seen.
5
Q
Capillaries
A
- Comprise only a layer of vascular endothelial cells resting on inside of basement membrane.
- -Composed entirely of thin-walled endothelial cells with no surrounding muscle or connective tissue.
- Most tissues have closed capillaries but some tissues (kidney & liver) have more leaky fenestrated ones.
6
Q
Pericytes
A
- Can constrict or relax vascular channels. Present on outside of capillaries
- In smallest capillaries, pericytes form a discontinuous layer on outside of capillary which becomes continuous as capillaries get larger.
7
Q
Fenestrated capillaries
A
-Fenestrated capillaries- vascular endothelial layer is incomplete forming windows that facilitate the movement of materials out of the circulation and into surrounding tissues.
8
Q
Veins
A
- Larger lumen and thinner media
- Has same 3 layers of tissue as artery, but thinner.
- Comprises same as arteries except external elastic lamina.
- Arterioles have thicker muscular wall and a smaller lumen than veins and venules.
- Large veins are thick walled compared to venules and corresponding arteries.
- Smooth muscle in wall may be circular or longitudinal.
9
Q
Venules
A
- Associated with arterioles
- Thin walled
- Contractile pericytes wrap around outside of endothelial cells and form a complete layer as venules get longer.
- Pericytes replaced by smooth muscle as venules become veins.
10
Q
Lymphatics
A
-Thin walled, similar to capillaries and veins
-Have valves
-Do not contain blood
-Contains eosinophilic lymph and may contain
lymphocytes.
-Lymphatic valves covered by endothelium that lines all blood vessels and lymphatics. Inside are some strands of collagen.
11
Q
Peripheral Nerves
A
- Composed of axons
- Supported by Schwann cells
- Most are myelinated insulating sheath
- Myelin produced by Schwann cells
12
Q
Small Peripheral Nerve Fibre
A
- Bundle of axons interspersed with endoneurium and surrounded by perineurium and epineurium.
- Consider nerves alongside blood vessels as commonly found together as a Neuro-vascular bundle. i.e. in trachea.
13
Q
Myelinated Peripheral Nerve
A
- Endoneurium-present between individual axons.
- Perineurium-surrounds the groups of axons to form fascicles.
- Epineurium- Binds fascicles together to form nerve fibres.
14
Q
Myelin
A
- Produced by Schwann cells
- Insulates axons
- A spiral of apposed Schwann cell membranes
- Multiple Schwann cells per myelinated axon. One axon per Schwann cell.
- Schwann cell envelops and spirals around the axon.
- Gaps between Schwann cells are Nodes of Ranvier.
- Doesn’t stain easily with H&E, use silver stain.
15
Q
Myelinated and Unmyelinated Axons
A
- Schwann cells support one or more axons and produce myelin in some cases.
- Myelinated axons are larger and transmit impulses faster than unmyelinated ones.
- Unmyelinated axon/fibre-multiple axons associated with a single schwann cell at any 1 point whereas in myelinated only a single axon related to a single schwann cell.
