Page 92 - Headlines Histology2024_Neat

• Efferent visceral (involuntary) innervate cardiac & smooth muscles and
glands

• The visceral efferent fibers form the autonomic nervous system (ANS). The
autonomic pathway consists of two neurons.

• The first one located in the CNS (brain and spinal cords) and is called
periganglionic neurone.

• The cell body of the second neurone is located in autonomic ganglia. The
ANS has two main divisions:

• Sympathetic branch: where the cell bodies of the preganglionic neurons are
located in the thoracic and lumber regions of the spinal cord (thoraco-
lumber).

• Parasympathetic branch: where the cell bodies are located in the brain and
sacral region of the spinal cord (cranio-sacral).

Peripheral nerve

• A nerve is composed of thousands of axons, each is sheathed by
neurolemmocytes.

• Each peripheral nerve is made up of one or more bundles or fascicles of
nerve fibers.

• Within the bundles, each individual nerve, with its investing
neurolemmocyes is surrounded by delicate loose connective tissue
containing few fibroblasts and blood capillaries called endoneurium.

• Each fascicle is surrounded by perineurium that has two layers: fibrous
perineurium that is a condensed layer of collagenous connective tissue; and
perineurium epithelium, consisting of several concentric layers of squamous
epithelial cells.

• In peripheral nerves consisting of more than one fascicle, a further layer of
loose connective tissue called the epineurium binds the fascicles together.
The large blood vessels supplying nerves (vasa nervorum) are found within
the epineurium.

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