Sometimes called fibers of Remak. There is no medullary or myelin sheath Axis cylinder is very slender and the thin neurolemma sheath contains scattered nuclei of Schwann cells. There are no nodes of Ranvier, up to a dozen or more of these nerve fibres are enclosed by the cytoplasm of the same sheath of Schwann […]
The medullated nerve fibers of the peripheral nervous system consist of the axon, myelin or medullary sheath and neurolemma. In the central nervous system, instead of the neurolemma, there is an irregular covering made of glial cells. Myelin forming the myelin sheath is glistening while when fresh, but with osmic acid fixation becomes grey or
Neurolemma or sheath of Schwann This is a thin tube like membranes or sheath, containing a nucleus surrounded by cytoplasm and is also known as schwann’s cell. The neurolemma forms sheath of the axon in all peripheral nerves and inside the central nervous system there is no neurolemma but the nerve fibres have a neurolemma and
The single axon arises from a special part of the periphery of cell body called axon hillock. This area is devoid of Nissl bodies and Golgi apparatus. Length of axon varies from a fraction of a millimeter to several feet. Branches arise at right angles form axons and are called collaterals axon is made up
The nervous tissue is specialized to receive stimuli from the environment to transform them into nerve impulses and to transmit them to the nerve centers, from where appropriate response is transmitted to another organ or part of the body which reacts to the response of the original stimulus. Nucleus is pale staining and vesicular but
With slight injury the smooth and skeletal muscle fibres may proliferate but a larger defect of the muscular tissue is made good only by a connective tissue scar. The cardiac muscle has little regenerative capacity and healing is by formation of scar tissue.
Myocardium or heart muscle is composed of an interlacing network of muscle fibres (cells). The muscle net is irregularly and incompletely divided into bundles and laminae which wind about the heart in the form of spirals. The fibres within a bundle are mostly parallel but the bundles themselves course in different directions so that a
The independent units of skeletal muscle are called as muscle fibres. The fibres have many nuclei and are larger than most cells. Fibres are grouped together into bundles of fasciculi. Larger muscles are composed of many fasciculi. The skeletal muscle fibres are elongated and cylindrical and 1.5 cm in length and 10-15 microns in diameter.
Smooth muscles Consists of fusiform or spindle shaped cell 15 to 500 microns in length with abundant cytoplasm in whose central thickest position the nucleus lies. The nucleus is oval elongated or rod-shaped. The nuclei of contracted muscle cells usually have a folded outline. The cytoplasm contains the usual organoids and appears more or less
Three types of muscle viz., smooth, skeletal and cardiac are distinguishable histologically- Smooth or non-striated muscle lacks the cross striations seen in other two muscles. The smooth muscle is involuntary, being especially associated with viscera which are not under the voluntary control. Skeletal muscle is striated and voluntary making up the bulky muscles of the body. Cardiac or heart muscle is striated
