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Nervous tissue: Neuron and Neuroglia Nervous tissue  contains densely packed  nerve cell ( neuron) ,which are specialized for nerve impulse conduction. Origin-  ectoderm Nervous tissue consists of Neuron or nerve cell  (functional unit of Nervous system) Neuroglia (glial cell) Neuron: About 100 billions of neurons are present in nervous system. They are Specialised type of cell, they vary in shape and size, all neurons contains three principle parts-  cell body, dendrites and an axon Cell body Has a large nucleus, which contain prominent nucleolus, as well as other several structures (Nissl bodies, ER,lysosome, mitochondria, neuroflament), responsible for metabolism, growth and repair of neuron Nissl bodies-  made up of RNA, RER and free ribosome, help in protein synthesis Neurofilament and neurotubules  are thread like protein, runs parallel to long process Neurofilament-  semisolid structure that provide skeletal ...

Human Eye: Anatomy, parts and structure The eye is the photo-receptor organ. Size and shape:  Human eye is spherical about 2.5 cm in diameter. Location:  it is situated on an orbit of skull and is supplied by optic nerve. There are 6 sets of muscles attached to outer surface of eye ball which helps to rotate it in different direction. Four sets of these muscles are straight muscles; superior, inferior, medial and lateral rectal muscle and two sets are oblique muscles; superior and inferior oblique muscles. Structurally two eyes are separated but some of their activities are coordinated so that they functions as a pair. Anatomical structure of Eye Eye ball consists of three layers Outer fibrous layer: Sclera, cornea and conjunctiva Middle vascular layer: ciliary body, choroid and iris Inner layer: retina I. Outer fibrous layer: It consists of following parts. 1. Sclera: It is outermost supporting layer consists of thick membrane of tough fibrous c...