Prac 4 Blood vessels and nerves Flashcards
3 major types of blood vessel
Arteries (Thick wall)
Capillaries (Thin wall)
Veins (Thicker wall)
two major circulatory systems in the body
1 the longer systemic circulation through which blood is transported from the heart to all the tissues of the body
2 shorter pulmonary circulation between the heart to the lungs for the re-oxygenation of the blood.
Describe structure and function of lymphatic vessels
lood plasma which leaves the circulation at the capillaries to bathe the adjoining tissues is returned to the general circulation by a series of vein-like lymphatics. These vessels are generally devoid of blood cells, apart from some of those of the immune system
Difference in appearance between artery and vein
The artery normally has a thicker, more muscular wall and appears circular in outline while the accompanying vein is often larger in diameter, has a thinner, less muscular wall and often has an irregular profile.
what does the The innermost intimal layer consist of
It consists of an endothelium with a small amount of connective tissue beneath. It is separated from the medial layer by a wavy internal elastic lamina (it glistens), a tube-like sheet of elastic tissue
3 layers of arteries and veins
an innermost intimal layer, a medial layer and an outermost adventitial layer.
In muscular arteries what is the medial layer composed of
the media layer is composed mainly of smooth muscle arranged circumferentially. When this muscle contracts it reduces the diameter of the vessel.
VASA VASORUM
Vessels of vessels – Blood vessels near heart are so big they have blood vessels of their own
What classifies as an arteriole?
. As a guideline, arterial vessels with three or less layers of smooth muscle in the medial layer (or which are 100 um or less in diameter) are generally regarded as arterioles
also These vessels normally lack an external elastic lamina and often the internal elastic lamina is poorly developed.
What happens as a result of retrials being small in diameter
They can be closed down completely as a result of the contraction of the smooth muscle in their walls. As a consequence blood is temporarily shunted down a different route.
Describe venues compared to arterioles
Venules are thinner walled and have very little or no muscle. Their walls often consist of an endothelium reinforced only by connective tissues.
Characteristics of lymphatics `
They have an irregular outline and thin walls composed of a mixture of collagen and elastic fibres with a few smooth muscle cells. Like many veins, they contain valves
Typically they are filled with an amorphous colloid (plasma) that stains pink with the H&E stain.
What are lymphatic valves made of
Covered by the endothelium that lines all blood vessels and lymphatics. Inside are some strands of collagen
How do continuous capillaries work
In continuous (closed) capillaries substances are transported across the capillary wall by diffusion or by pinocytosis
How do fenestrated capillaries work
Fenestrated capillaries have pores in them and products can pass fairly freely through the pores (fenestrae - windows).
Each part of nervous system contains supporting cells called
oligodendrocytes (CNS) or Schwann cells (PNS) that often produce an insulating layer of myelin around the axons.
Nerve cells contain
a complex cytoskeleton of fibrous proteins which confer the characteristic shape to neurons and are involved in forward (anterograde) and backward (retrograde) movement of organelles and substances along axons.
Neurones consist of
Neurons consist of cell bodies containing the cell nucleus and cell processes called axons and dendrites. Axonal processes can be extremely long; those of the nerves which supply muscles in the foot for example being over 1 meter long.
Most nerve cell bodies lie within the CNS (brain or spinal cord). But what are the exceptions
The exceptions are the periperal sensory nerve cell bodies that are located within the dorsal root ganglia and those of the autonomic nervous system which are located in peripheral ganglia either alongside the spinal column (mainly sympathetic ganglia) or embedded within the organs that they innervate (mainly parasympathetic ganglia).
Why is it difficult to distinguish myelinated from unmyelinated axons in histological sections
most of the myelin is lost during tissue processing.
Explain the relationship between myelination and ratio of schwann cells
When axons are myelinated they are supported by their own Schwann cell (1:1 relationship) but a single Schwann cell is capable of supporting several unmyelinated axons.
what the difference in structure between myelinated and unmyelinated axons and what does this cause?
Myelinated axons are generally larger (greater diameter) than unmyelinated ones and their conduction velocity is faster.
How can the structure of peripheral nerves best ben seen?
The structure of a peripheral nerve can be seen best if the lipids of the myelin sheaths are preserved by treating isolated nerves with osmium tetroxide. This renders the myelin insoluble and it appears brown/black in colour.
What is myelin mainly composed of?
Bilipid layer with portions inserted into it and spanning between the layers
Sphingomyelin is the predominant phospholipid
What is a mesaxon
Point where two limbs of the schwann cell or oligdendrocyte that engulf the axon fuses
Focal point where myelin is inserted into the myelin sheath
Why do the cell bodies of sensory neurones appear more rounded in outline than motor neurones
these large cell bodies have only one axon and one major dendrite
Nissl substance,
an alternative name for rough endoplasmic reticulum.
perikaryon
(cytoplasm surrounding the nucelus
perikaryon
(cytoplasm surrounding the nucleus
