sense organs.pptx anatomy and physiology of ear in detail.

Ear ppt in detail and easy language.

1. The sensory organs By Roshni Nursing Tutor

2. The sense organs: The special senses of hearing, sight, smell and taste are all have specialised sensory receptors outside the brain. The sense organs are: Eye – vision. Ear – auditory . Tongue- gustation. Nose- olfactory. Skin- touch.

3. Eye The eye is the organ of sight. It is situated in the orbital cavity and supplied by the optic nerve . It is almost spherical in shape and about 2.5 CM in diameter. Accessory structure of eye:- Eyebrows : they are the two arches of thick skin over the eye, they contain thick hairs. Eyelids : they are the upper and lower eyelids which protect the eye. Lacrimal apparatus : it is concerned with the production of tear and situated in the lateral end of upper eyelid . It containing the orbital structures for tear production and drainage. Conjuctiva : this is a fine transparent membrane that lines the eyelids and the front of the eye, when the eyelids are closed the conjunctiva become closed sac.

4. Structure OR ORGAN OF VISION There are three layers of tissue in the walls of the eye. The outer fibrous layer:- Sclera and cornea Middle vascular layer or uveal tract:- choroid, ciliary body and iris. Inner nervous tissue layer :- Retina Structures inside the eyeballs are:- Lens Aqueous fluid Vitrous body.

5. Sclera and cornea The sclera or white of the eye, forms the outermost layer of the eyeball. It consist of a firm fibrous membrane that maintains the shape of eye and give attachment to the extrinsic muscle of the eye. Light rays pass through the cornea to reach the retina. The cornea is convex anteriorly and is involved in refracting light rays to focus on the retina. CHOROID It is thin and very rich in blood vessel and is deep chocolate brown in colour. It lines the posterior compartment of the eye and lies between the inner surface of Sclera and retina.

6. Ciliary body Ciliary body is the anterior continuation of the choroid consisting of ciliary muscles and secretory epithelial cells. The lens is attached to the ciliary body by radiating suspensory ligament Contraction and relaxation of the ciliary muscle fibres control the shape of the lens. The epithelial cells secrete aqueous fluid into the anterior segment of the eye, that is the space between lens and the cornea.

7. Iris The iris is the visible coloured part of the eye and extend anteriorly from the ciliary body, lying behind the cornea and in front of the lens. It divide into anterior and posterior chambers which contain aqueous fluid secreted by the ciliary body . It is a circular body composed of pigment cell and two layers of smooth muscle fibres. In the centre is an aperture called the pupil . Pupil control the amount of light entering in the eye. In a bright light the pupil are constricted, in a dim light they are dilated.

8. PUPIL An opening created by the actions of the iris where a large pupil is caused by a dilated iris, while a small pupil is created by a constricted iris.

9. Lens The lens is a highly elastic circular biconvex body, lying immediately behind the pupil. It is attached to the ciliary body by means of suspensory ligaments of lens. The thickness of lens is controlled by ciliary muscle through suspensory ligament. Function: The lens bends light rays reflected by objects infront of the eye. It is the only structure in the eye that can vary its refractory power, which is achieved by changing its thickness.

10. Retina Retina is the innermost layer of the wall of the eye. FUNCTION. It consist of sensory receptor, rods and cones. Rods provide vision during dim light or night. Cones provide vision during daytime or at bright light, it is responsible for colour vision. The rods and cones receive the light and this sets up impulses which are transmitted through optic nerve. Near the centre of the posterior part of retina is the macula lutea or yellow spot that processes sharp, clear ahead vision.

11. Macula lutea and all the nerve fibres of the retina converge to form the optic nerve where the optic nerve leaves the eye is the optic disc. Blood supply to the eye: Arterial blood supply by ciliary arteries and Central retinal arteries. Venus drainage by central retinal veins.

12. BLOOD SUPPLY The eye ball is supplied by the branches of ophthalmic artery. The branches are ciliary artery and the central artery of retina. The venous drainage is into cavernous sinus.

13. Interior of the eyewall The interior segment of the eye is divided by iris into anterior and posterior chambers containing aqueous humour and vitreous humour. Aqueous humour is a water-like fluid that lies in front of the lens. Vitreous humour is a gel-like substance that lies behind the lens and in front of the retina. The shape of the eye ball is maintained by the intra ocular pressure exerted by the vitreous humour mainly and partly by aqueous humour, constantly throughout life. Both aqueous humour and vitreous humour function to refract the light rays on the retina.

14. Physiology of vision The normal eye, known as an emmetropic eye, can sufficiently refract light rays from an object 6 m (20 ft.) away to focus a clear object on the retina. The formation of an image on the retina requires four basic processes, all concerned with focusing light rays:
1. Refraction of the light rays
2. Accommodation of lenses
3. Constriction of the pupil
4. Convergence of the eyes

15. Step 1: Light Enters the Eye - Light from an object enters the eye through the cornea (the transparent outer layer).
- The light then passes through the pupil (the opening in the center of the iris). Step 2: Light is Focused - The light is focused by the lens onto the retina (the innermost layer of the eye).
- The shape of the lens changes to adjust focus for near or far objects.
if you have any specific questions or need further clarification. Step 3: Light is Converted to Signals - The focused light hits photoreceptor cells (rods and cones) in the retina.
- These cells convert the light into electrical signals.

16. Step 4: Signals are Transmitted - The electrical signals are transmitted to bipolar cells, which then send them to ganglion cells.
- The ganglion cells collect the signals and send them to the optic nerve. Step 5: Signals Reach the Brain - The optic nerve carries the electrical signals to the brain.
- The brain interprets these signals as visual information, allowing us to see the world around us.

17. Accommodation of reflex When focusing on a near object, the eye undergoes several changes to ensure a clear image. Here’s how it works:
Changes in the Eye:
1. Convergence : The eyes rotate inward to focus on the near object.
2. Pupillary constriction : The pupils constrict to increase the depth of field and reduce peripheral light rays.
3. Lens accommodation : The lens becomes more rounded due to the contraction of the ciliary muscles, increasing its refractive power. Common Issues: - Presbyopia : Age-related decline in accommodation, making it harder to focus on near objects.
- Hyperopia (farsightedness): Difficulty seeing near objects clearly due to the eyeball being too short or the cornea being too flat.

18. When focusing on a distant object, the eye undergoes changes to ensure a clear image. Here’s how accommodation works for distant objects.
Changes in the Eye:
1. Relaxation of ciliary muscles: T he ciliary muscles relax, causing the lens to become flatter.
2. Increased focal length: T he flatter lens has a longer focal length, allowing distant objects to be focused on the retina.
3. Pupillary dilation: T h e pupils may dilate slightly to allow more light to enter the eye. Common Issues: Myopia (near-sightedness): Difficulty seeing distant objects clearly due to the eyeball being too long or the cornea being too curved.
Hyperopia (farsightedness):Difficulty seeing near objects clearly due to the eyeball being too short or the cornea being too flat.