6. Lecture On The Histology Of Peripheral Nerve And Ganglia By Dr. Roomi 3q4x5z

HISTOLOGY OF NERVOUS TISSUE BY DR. MUDASSAR ALI ROOMI (MBBS, M. PHIL)

peripheral nerve • Peripheral nerves include: cranial nerves, spinal nerves. • It is made up of bundle of nerve fibers, both myelinated and unmyelinated. • On naked eye examination, it appears whitish and glistening because of their myelin and collagen content. • Examples: median nerve, ulnar nerve, sciatic nerve

peripheral nerve (cont.) • Epineurium: it is sheath of dense irregular C.T. around peripheral nerve. • Perineuriun: – it is C.T sheath around each fascicle or bundle of nerve fibers. – This is made by many concentric layers of epitheloid cells ed together by tight junctions . – Perineurium acts as a barrier to the age of materials.

• endoneurium: it is thin layer of C.T. around each nerve fiber. It is composed of delicate collagenous and reticular fibers and fibroblasts.

peripheral nerve (l.s.)

How to draw it!

peripheral nerve- identification points • Bundles of nerve fibers • Myelin sheath is seen as unstained area • Endoneurium, perineurium and epineurium is visible

GANGLIA

• Ganglia: It is collection of nerve cell bodies outside the CNS • Ganglia are ovoid structures associated with peripheral nerve. • microsopically and functionally the ganglia are of two types: – Craniospinal (sensory) ganglia – Autonomic ganglia

• Common features of both types of ganglia: – Both types of ganglia have C.T. capsule. – The body of each ganglion cell is surrounded by satellite cells

Cranio Spinal ganglia • • • •

Cranial ganglia Spinal ganlia (dorsal root ganglia) C.T. Capsule Ganglion cells are pseudounipolar neurons *** – Each cell has a single process which bifurcates in a T-shaped manner. – One of the two processes acts as dendrite and es to periphery to terminate at a receptor organ – The othe branch acts as axon and es to CNS.

• The nerve impulses from the periphery to CNS, bying the cell body. • So the cell body form no synapses and performs an exclusively trophic function.

Cranio Spinal ganglia (cont.) • The nerve cell bodies are arranged as groups in the peripheral zone of the ganglion. • Each ganglion cell is surrounded by a single layer of low cuboidal cells are called as satellite cells • Central zone of the sensory ganglion shows great predominance of nerve fibers

Dorsal root ganglion

dorsal root ganglion- identification points • Connective tissue capsule present • Pseudounipolar neurons surrounded by satellite cells

Dorsal root ganglion- how to draw it!

Autonomic Ganglia • These ganglia are associated with sympathetic and parasympathetic ANS. • These ganglia contain multipolar neurons: – Each ganglion cell has many dendrites and a single axon. – Dendrites receive synapses from the incoming preganglionic nerve fibers – Axon es out as postganglionic fiber.

Ganglia Cranio Spinal Cranial nerve ganglia

Autonomic Spinal ganglia

Cranio Spinal ganglia • ganlionic cells are present as groups in the ganglion. •Variable size of the ganglion cells •Pseudo – unipolar cells • Sensory • No synapse • +++ satellite cells • complete capsule of satellite cells

Sympathetic

Parasympathetic

Autonomic ganglia •Evenly distributed • •Uniform size • Multipolar cells • Secretomotor • ++ synapse • + satellite cells • incomplete capsule of satellite cells