Briefly describe the structure of the following: 1. Brain (b) Eye (c) Ear
(A) Brain: Brain is the principle coordinating centre of the frame. It is part of fearful gadget that controls and monitors each organ of the frame. It is nicely blanketed via way of means of cranial meninges which can be made from an outer layer referred to as dura mater, a skinny center layer referred to as arachnoid, and an internal layer known as pia mater. It is split into 3 areas - forebrain, midbrain, and hindbrain. Forebrain: It is the primary wondering a part of the mind. It includes cerebrum, thalamus, and hypothalamus. (a) Cerebrum: Cerebrum is the biggest a part of the mind and constitutes approximately 4-5th of its weight. Cerebrum is split into cerebral hemispheres via way of means of a deep longitudinal cerebral fissure. These hemispheres are joined with the aid of using a tract of nerve fibre called corpus callosum. The cerebral hemispheres are protected through a layer of cells called cerebral cortex or gray matter. Cerebrum has sensory areas referred to as affiliation regions that acquire sensory impulses from diverse receptors in addition to from motor areas that manage the motion of diverse muscles. The innermost a part of cerebrum offers an opaque white look to the layer and is called the white matter. (b) Thalamus: Thalamus is the primary centre of coordination for sensory and motor signalling. It is wrapped through cerebrum. (c) Hypothalamus: It lies at the bottom of thalamus and consists of some of centres that adjust frame temperature and the urge for consuming and drinking. Some areas of cerebrum, along side hypothalamus, are concerned withinside the law of sexual behaviour and expression of emotional reactions which include excitement, pleasure, fear, etc. Midbrain: It is positioned among the thalamus location of the forebrain and pons area of hindbrain. The dorsal floor of midbrain includes advanced and inferior corpora bigemina and 4 spherical lobes referred to as corpora quadrigemina. A canal called cerebral aqueduct passes thru the midbrain. Midbrain is worried with the feel of sight and listening to. Hindbrain: It includes 3 areas - pons, cerebellum, and medulla oblongata. (a) Pons is a band of nerve fibre that lies among medulla oblongata and midbrain. It connects the lateral elements of cerebellar hemisphere together. (b) Cerebellum is a big and properly evolved a part of hindbrain. It is positioned under the posterior facets of cerebral hemispheres and above medulla oblongata. It is accountable for keeping posture and equilibrium of the frame.(c) Medulla oblongata is the posterior and only a part of the mind. It is positioned under the cerebellum. Its decrease stop extends withinside the shape of spinal twine and leaves the cranium via foramen magnum. (B) Eye: Eyes are round systems that encompass 3 layers. (a) The outer layer consists of sclera and cornea. (i) Sclera is an opaque tissue this is normally called white of the attention. It consists of a dense connective tissue. (ii) Cornea is a obvious anterior part of eye that lacks blood vessels and is nourished through lymph from the nearby area. It is barely bulged ahead and allows in focusing mild rays with the assist of lens. (b) The center layer of eye is vascular in nature and consists of choroid, ciliary frame, and iris. (i) Choroid lies subsequent to the sclera and includes severa blood vessels that offer vitamins and oxygen to the retina and different tissues. (ii) Ciliary frame: The choroid layer is skinny over posterior area and receives thickened withinside the anterior element to shape ciliary frame. It incorporates blood vessels, ciliary muscles, and ciliary processes. (iii) Iris: At the junction of sclera and cornea, the ciliary frame keeps ahead to shape skinny colored partition referred to as iris. It is the seen colored part of eye. The eye carries a obvious, biconvex, and elastic shape simply in the back of the iris. It is referred to as lens. The lens is held in function with the aid of using suspensory ligaments connected to the ciliary frame. The lens divides the attention ball into chambers - an anterior aqueous and posterior vitreous chamber. (c) The innermost apprehensive coat of eye incorporates retina. Retina is the innermost layer. It includes 3 layers of cells - internal ganglion cells, center bipolar cells, and outermost photoreceptor cells. The receptor cells gift withinside the retina are of types - rod cells and cone cells. (a) Rod cells -The rods include the rhodopsin pigment (visible purple) this is distinctly touchy to dim mild. It is liable for twilight vision. (b) Cone cells -The cones comprise the iodopsin pigment (visible violet) and are fairly touchy to excessive depth mild. They are chargeable for daylight hours and color visions. The innermost ganglionic cells provide upward push to optic nerve fibre that paperwork optic nerve in every eye and is attached with the mind. (C) Ear: Ear is the feel organ for listening to and equilibrium. It includes 3 portions - outside ear, center ear, and inner ear. 1. External ear: It includes pinna, outside auditory meatus, and a tympanic membrane. (a) Pinna is a touchy shape that collects and directs the vibrations into the ear to supply sound. (b) External auditory meatus is a tubular passage supported via way of means of cartilage in outside ear. (c) Tympanic membrane is a skinny membrane that lies near the auditory canal. It separates the center ear from outside ear. 2. Middle ear: It is an air-crammed tympanic hollow space this is related with pharynx thru eustachian tube. Eustachian tube allows to equalize air strain in each facets of tympanic membrane. The center ear consists of a bendy chain of 3 center bones known as ear ossicles. The 3 ear ossicles are malleus, incus, and stapes which are connected to every different. 3. Internal ear:It is likewise called labyrinth. Labyrinth is split into bony labyrinth and a membranous labyrinth. Bony labyrinth is packed with perilymph at the same time as membranous labyrinth is packed with endolymph. Membranous labyrinth is split into 2 components. (a) Vestibular equipment Vestibular equipment is a principal sac-like element this is divided into utriculus and sacculus. A unique organization of sensory cells referred to as macula are found in sacculus and utriculus. Vestibular equipment additionally incorporates 3 semi-round canals. The decrease stop of every semi-round canal carries a projecting ridge known as crista ampularis. Each ampulla has a collection of sensory cells known as crista. Crista and macula are answerable for keeping the stability of frame and posture. (b) Cochlea: Cochlea is an extended and coiled outgrowth of sacculus. It is the primary listening to organ. Cochlea includes 3 membranes. The organ of corti, a listening to organ, is positioned at the basilar membrane that has hair cells.
