Blood Vessels and Nerves Flashcards
What is the common structure of the blood vessels - inside out
Lumen
Endothelium
Basement membrane
Initima
Internal elastic lamina (thin)
Media (thick)
External elastic lamina (thin)
Adventitia
In elastic artery what does the media contain
Abundant concentric sheets of elastin
Where are elastic arteries found
Arteries near the heart
e.g. aorta, pulmonary arteries
What are most arteries in the body
Muscular arteries
e.g. radial artery, splenic artery
What does the media comprise of in muscular arteries
Layers of smooth muscle
Little elastin
What are arterioles
Resistance vessels
Elastic laminae poorly defined
How are arterioles defined
Having 3 or fewer muscle layers in their media
OR
Up to 100um in diameter
What is the structure of capillaries (from inside)
Lumen
Endothelium (some capillaries is incomplete for movement of materials - fenestrated capillaries)
Basement membrane
Present on outside - pericyte
Describe capillaries
Composed entirely thin-walled endothelial cells with no surrounding muscle or connective tissue
Do most cells have closed or fenestrated capillaries
Most have closed
Fenestrated e.g. kidney and liver
What is the structure of veins
Same as arteries but no external elastic laminae
Arteries and arterioles have thicker muscular walls and smaller lumens
Describe venules
Associated with arterioles
Thin walled
Contractile pericytes wrap around outside of endothelial cells and form a complete layer as venules get larger
Pericytes relaces by smooth muscle as venules become veins
Describe veins
Larger veins are thick walled (compared to venules)
Thin walled compared to corresponding artery
Smooth muscle in wall may be circular or longitudinal
Describe lymphatics
Thin walled, similar to capillaries and veins
Have valves
Do not contain blood
Contain eosinophilic lymph and may contain lymphocytes
Describe peripheral nerves
Composed of axons
Supported by Schwann cells
What is myelin produced by
Shwann cells
Are most peripheral nerves myelinated or unmyelinated
Myelinated - insulting sheath
Define epineurium
Binds fascicles together to form nerve fibres
Define perineurium
Surrounds the groups of axons to form fascicles
Define endoneurium
Present between individual axons
What are commonly found together on stains as neuro-vascular bundles
Nerve
Arteriole
Venule
What does not stain myelin readily
H&E
Can be stained with silver stains
Describe myelin
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 them
What are the gaps between Schwann cells called
Nodes of Ranvier
Define Schwann cells
Support one or more axons and produce myelin in some cases
Define myelinated axons
Larger and transmit impulses faster than unmyelinated ones
What is the difference between myelinated and unmyelinated axons
Myelinated - one Schwann cells to one axon in one point
Unmyelinated - on Schwann cell multiple axon in one point
Do axons stain
No, remain white
Where are motor neurons found
Cell bodies in grey matter of spinal cord
Where are sensory neurons found
Cell bodies in dorsal root of ganglion
Where are sympathetic neurons found
Cell bodies in grey matter of cord
AND
in adjacent sympathetic ganglia
Where are parasympathetic neurones found
Cell bodies in brain and local ganglia
