General Histology Practical Lab 7 Nervous System Nerve

General Histology Practical Lab 7

Nervous System Nerve endings: 3. Meissner corpuscles: • Located in some dermal papillae of the finger tips and lips. • as pear- shaped encapsulated mechanoreceptors specialized to respond to touch senstivity. • composed of stratified flatted epithelial cells and surrounded by fibrous connective tissue capsule. • These receptors are most common in areas of the skin especially sensitive to tactile stimulation.

skin

4. Pacinian corpuscles: The encapsulated mechanoreceptor located in the dermis and hypodermis. • specialized to perceive pressure, and vibration. • Pacinian corpuscles are large ovoid receptors. The core of the corpuscle contain the non myelinated nerves terminal surrounded by layers of modified fibroblasts and enveloped by connective tissue, forming the capsule. • It is found in the pancreas and skin of human ( dermis and hypodermis). •

Peripheral nerves • Peripheral nerves are bundles of nerve fibers (axons) surrounded by several investments of connective tissue sheaths. • The epineurium is the outermost layer of the three investments. • composed of dense irregular fibrous connective tissue. • containing some thick elastic fibers , collagen fibers are function to prevent damage by over stretching of the nerve bundle.

• The perineurium • the middle layer of connective tissue investments. • composed of dense connective tissue but is thinner than epineurium. • its inner surface is lined by several layers of epithelial cells. • Between the layers of epithelial cells are spare collagen fibers with a few elastic fibers, fibroblasts and blood vessel.

• The endoneurium, • the inner most layer of the investments, surrounds each axon. • It is a loose connective tissue composed of a thin layer of reticular fibers, fibroblasts , macrophages, capillaries, and mast cells • it is contact with the basal lamina of the Schwann cells.

(endoneurium)

(endoneurium)

Ganglia • are aggregations of cell bodies of neurons located outside the CNS. • There are two types, sensory ganglia and autonomic ganglia. • Spinal ganglia: Sensory neurons of the spinal nerves are called dorsal root ganglia. Sensory ganglia house pseudounipolar cell bodies of the sensory nerve enveloped by dense connective tissue capsule composed of satellite cells , collagen and blood vessels.

P (sensory ganglia)

e

. R O F U O Y G K N I N N A I T H T LIS