2. INTRODUCTION
◦ The special senses are hearing, sight, smell , taste, balance; all
have specialised sensory receptors that collect and transmit
information to specific areas of the brain.
◦ Incoming nerve impulses from the ear, eye , nose and mouth
are integrated and coordinated within the brain, allowing
perception of this information.
3. EAR
◦ The ear is the organ of hearing and is also involved in balance.
◦ It is supplied by the cochlear branch of the 8th cranial (
vestibulocochlear) nerve, which response to the vibrations
generated by sound waves and transmits this information to the
brain.
◦ With the exception of the auricle (pinna), the structures that form
the ear are encased within the petrous portion of the temporal
bone .
4.
5. Structure
◦ The ear is divided into three distinct parts.
1. The outer ear
2. The middle ear (tympanic cavity)
3. The inner ear
6. Outer ear
◦ The outer ear consists of the auricle(pinna) and the external acoustic
meatus (auditory canal).
•Auricle
◦ The auricle is the visible part of the ear that projects from the side of
the head.
◦ It is composed of fibroblastic cartilage and covered with skin .
◦ It is deeply grooved and ridged, the most prominent outer ridge is the
helix.
7. ◦ The lobule(earlobe) is the soft pliable part at the lower extremity,
composed of fibrous and adipose tissue richly supplied with blood.
•Auditory canal
◦ This is a slightly ‘S’-shapped tube about 2.5 cm long, extending from the auricle
to the tympanic membrane (eardrum).
◦ The lateral third is embedded in cartilage and the remainder lies within the
temporal bone.It is lined with skin continuous with that of the auricle.
◦ There are numerous ceruminous glands and hair follicles, with associated
sebaceous gland, in the skin of the lateral third.
◦ Cerumious glands are modified sweat glands that secrete cerumen(earwax), a
sticky material containing protective substance including the bactericidal
enzyme, lysozyme , and immunoglobulins.
8. ◦ Foreign materials, e.g.dust, insect, and microbes, are prevented from
reaching the tympanic membrane by wax, hair and the curvature of
the meatus.
◦ Movement of the temporomandibular joint during chewing and
speaking 'message’ the cartilaginous meatus, moving the wax
towards the exterior.
◦ The tympanic membrane completely separates the external acoustic
meatus from the middle ear.
◦ It is oval shaped with the slightly broader edge upwards and is
formed by three layer of tissue .
1. An outer covering of hairless skin
2. Middle layer of fibrous tissue
3. Inner linning of mucous membrane
9. Middle ear
◦ This is an irregular shaped air-filled cavity within the petrous
portion of the temporal bone.
◦ The cavity , it’s contents and the air sacs that open out of it are
lined with either simple squamous or cuboidal epithelium.
◦ The lateral wall of the middle ear is formed by the tympanic
membrane.
◦ The roof and floor are formed by the temporal bone.
◦ The posterior wall is formed by the temporal bone with opnings
leading to the mastoid antrum, through which air passes to the air
cells within the mastoid process.
10.
11. ◦ The medial wall is thin layer of temporal bone in which there are two
openings:
1. Oval window
2. Round window
◦ The oval window is covered by part of a small bone called the steps and the
round window by a fine sheet of fibrous tissue.
◦ Air reaches the cavity through the pharyngotympanic(auditory or
Eustachin)tube, which links the nasopharynx and middle ear.
◦ It is about 4 cm long and lined with ciliated columnar epithelium.
•Auditory ossicles
◦ These are three very small bones, only a few millimetres in size , that
form a chain across the middle ear from the tympanic membrane to
the oval window.
12. ◦ Between the bones there are synovial joints that allow the bones to
vibrate within the air -filled tympanic cavity.
• Malleus
◦ This is the lateral hammer shaped bone.
◦ The handle is in contact with the tympanic membrane, and the head
forms a synovial joints with the incus.
•Incus
◦ This is the middle evil shaped bone.
◦ It’s body articulates with the malleus,and the long process with the
stapes; it is stabilized by
13. • Stapes
◦ This is the medial stirrup shaped bone.
◦ It’s head articulates with the incus and its footplate fits into
the oval window.
14.
15. Inner ear
◦ The inner ear or labyrinth contains the organ of hearing and
balance.
◦ It is described in two parts : the labyrinth and the membranous
labyrinth.
◦ It is devided into three main regions ;
1. The vestibule, containing the utricle and saccule
2. Three semicircular canals
3. The cochlea.
16. ◦ The inner ear is formed from a network of channel and cavitie
in the temporal bone (the bony labyrinth).
•Bony labyrinth
◦ This is lined with periosteum.within the bony labyrinth, the
membranous labyrinth is suspended in a watery fluid called
perilymph.
17. •Membranous labyrinth
◦ This is filled with endolymph.
•Vestibule
◦ This is the expanded part nearest the middle ear
◦ The oval and round windows are located in its lateral wall.
◦ It contains two membranous sacs, the utricle and the saccule,
which are important in balance.
•Semicircular canal
◦ These are three tubes arranged so that one is situated in each of
the three planes of space.
18. ◦ They are continuous with the vestibule and are also important in
balance.
•Cochlea
◦ This resemble a snail‘s shell .
◦ It has a broad base where it is continuous with the vestibule and a
narrow apex, and it spirals round a central bony column.
19. Physiology of hearing
◦ Sound is carried as pressure (sound) waves in the air , which travel
at about 340 M/S .
◦ The auricle, because of it’s shape, collects and concentrate sound
waves and directs them along the auditory canal , causing the
tympanic membrane to vibrate.
◦ Tympanic membrane vibration are transmitted and amplified
through the middle ear by movement of ossicles.The latter fits into
the fenestra ovalis.
◦ The perilymph of the internal ear receives the vibrations through
the membrane covering the fenestra ovalis.
20. ◦ From the perilymph vibrations are transferred to the scala vestibuli
of cochlea and then to scala media through Reissner’s membrane.
◦ Subsequently the movement of endolymph and tectorial membrane
stimulate the sensory hair of the organ of corti.
◦ The impulses thus received by the hair cells are carried to the brain
through the auditory nerve where the sensation of hearing is felt.
◦ It is evident that the external and middle ear serve to transmit sound
waves to the internal ear.
◦ It is in the internal ear that the transformation of the vibrations into
nerve impulses for relay to the brain takes place.
21. ◦ From Scala tympani the sound waves are transmitted to the
tympanic or middle ear cavity through the membrane covering the
fenestra rotunda. From the tympanic cavity the sound waves are
transferred to the pharynx through the Eustachian tube.
22. Equilibrium
◦ The semicircular canals, utricle and saccule of membranous
labyrinth are the structures of equilibrium.
◦ Where the human displaced the hair cells of the cristae and
maculae are stimulated by the movement of the endolymph.
◦ The stimulus is carried to the brain through the auditory nerve and
the change of the position is detected by the medulla oblongata of
the brain. After that, the brain sends impulses to the muscles to
regain the normal conditions.
23. Eye
◦ Eye is the photo receptor organ
◦ Spherical shaped about 2.5 cm in diameter.
◦ It’s lies in a ball shaped cavity of the skull the orbital cavity and is
supplied by optic nerve.
◦ There are six 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, these are superior,
inferior, medial and lateral rectal muscles and two sets are oblique
muscles these are superior and inferior oblique muscles.
24.
25. Structure
◦ Eyeball is a hollow sphere that consist of three layers of tissue know
as tunics.
1. Outer layer
2. Middle layer
3. Inner layer
26. Outer fibrous layer
•Sclera
◦ It is the white part of the eye which is an opaque layer extending
posteriorly over 5/6 of the outer layer of the eyeball.
◦ It is made up of very strong and non-elastic fibrous connective
tissue.
◦ It gives eyeball it’s shape and protects the inner layer of eyeball.
27. •Cornea
◦ Sclera slightly bulges anteriorly (front part of the eye) which is
called cornea.
◦ It is transparent and non- vascular.
◦ It acts as a non- adjustable lens through which light enters into
the eyeball.
◦ A thin transparent membrane behind the eyelids called conjuctiva
terminates into the cornea.
28. •Conjunctiva
◦ The conjuctiva is the tissue that lines the inside of the eyelids and
coveres the sclera.
◦ It is composed of non-keratinized, stratified squamous epithelium
with goblet cells, stratified columnar epithelium and stratified
cuboidal epithelium.
◦ Divided into three regions:
1. The palpebral conjunctiva is further divided into the marginal,
tarsal, and orbital regions.The palpebral conjunctiva lines the
eyelids.
29. 2. The bulbar conjunctiva is divided into the sclera and limbal parts.The
bulbar conjunctiva is found on the eyeball over the anterior sclera.
3. The conjunctival fornices are divided into the superior, inferior, lateral
and medial regions.
Function
◦ Provides protection and lubrication of the eye by the production of
mucus and tears.
◦ Prevents microbial entrance into the eye and plays a role in immune
surveillance. It lines the inside of the eyelids and provides a covering to
the sclera. It is highly vascularized and home to extensive lymphatic
vessels.
30. Middle vascular layer
•Choroid
◦ The middle layer of the eye. Found in between the sclera and
retina.
Function : Providing nutrition for the retina, macula and
optic nerve.
◦ Regulating the temperature of the retina.
◦ Helping control pressure within the eye.
◦ Absorbing light and limiting reflections within the eye that could
harm vision.
31. •Ciliary body
◦ The ciliary body is a circular structure that is an extension of the iris, the
colored part of the eye.
◦ The ciliary body produces the fluid in the eye called aqueous humour. It
also contains the ciliary muscle, which changes the shape of the lens
when your eyes focus on a near object.
•Iris
◦ The iris is the colored part of the eye that controls the amount of light
that enters into the eye. It is the most visible part of the eye.
◦ The iris lies in front of the crystalline lens and separates the anterior
chamber form the posterior chamber.
◦ The contraction and relaxation of iris is a reflex response.
32. • Pupil
◦ The dark center opening in the middle of the iris.
◦ The Pupil changes size to adjust for the amount of light available
(smaller for bright light and large for low light)
◦ This opening and closing of light into the eye is much like the
aperture in most 35mm camera which lets in more or less light
depending upon the conditions.
33. •Lens
◦ It is elastic, colourless and transparent biconvex body made up of
epithelial cells lying posterior to iris.
◦ The lens can accommodate and its shape, focusing on different
objects at different distance,e.g. The lens is adjustable.
◦ This accomodation is brought about by ciliary muscles.
34. Inner nervous layer
•Retina
◦ The retina is the innermost lining of the eye.
◦ It is an extremely delicate structure composed of several layers of
nerve cell bodies and their axons, laying on a pigmented layer of
epithelial cells.
◦ The light sensitive layer consists of sensory receptor cells, rods and
cones, which contain photosensitive pigments that convert light
rays into nerve impulses.
◦ The retina lines about three quarters of the eyeball and is thickest
at the back.
35. Blood supply to the eye
◦ Arterial supply is from the ciliary arteries and the central renial
artery.
◦ These are branches of the ophthalmic artery, a branch of the
internal carotid artery.
◦ Venous drainage is by a number of veins, including the central
renial vein, which eventually empty into a deep venous sinus.
◦ The central renial artery and vein are encased in the optic nerve,
which enters the eye at the optic disc.
36. Optic nerve
•Optic chiasma
◦ This is situated immediately in front of and above the pituitary gland,
which lies in the hypophyseal fossa of the sphenoid bone.
◦ In the optic chiasma the nerve fibres of the optic nerve from the
nasal side of each retina cross over to the opposite side.
◦ The fibres from the temporal side do not cross but continue
backwards on the same side
◦ This crossing over provides both cerebral hemispheres with sensory
input from each eye.
37. •Optic tracts
◦ These are the phart of the optic nerve, posterior to the optic
chiasma.
◦ Each tract consists of the nasal fibres from the retina of one eye
and the temporal fibres from the retina of the other.
◦ The optic tracts pass backwards to synapse with nerve cells of the
lateral geniculate bodies of the thalamus. From there the nerve
fibres proceed backwards and medially as the optic radiations, to
terminate in the visual area of the cerebral cortex in the occipital
lobes of the cerebrum.
38. SKIN
◦ The skin is the outer covering of the body. In humans,it is the
largest organ of the integumentary system.
◦ The skin is making up 12-15% of body weight.
◦ The skin has up to seven layers of ectodermal tissue and
guards the underlying muscle, bones, ligaments and
internal organs. Human skin is similar to that of most
other mammals. Though nearly all human skin is covered with
hair follicles, it can appear hairless.
39. LAYERS OF SKIN
◦ Skin is composed of three layers
1. Epidermis
2. Dermis
3. Subcutanious or Hypodermis
40.
41. Epidermis
◦ Epidermis, “epi” coming from the Greek meaning “over” or
“upon” , Is the outermost layer of the skin.
◦ The epidermis has five regions and can range in total
thickness from 0.5mm to 1.5mm.
◦ It forms the waterproof, protection wrap over the body’s
surface which also serves as a barrier to infection and is made
up of statified squamous epithelium with an underlying basal
lamina.
42. Dermis
◦ The dermis is the layer of skin beneath the epidermis that
consist of epithelial tissue and cushions the body from stress
and strain. The dermis is tightly connected to the epidermis
by a basement membrane.
◦ It also harbors many nerve endings that provide the sense of
touch and heat. It contains the hair follicles, sweat glands,
sebaceous glands, apocrine glands, lymphatic vessels and
blood vessels.
◦ The blood vessels in the dermis provide nourishment and
waste removal from its own cells as well as from the stratum
basale of the epidermis.
43. Dermis – 2 layers
1. Papillary layer : superficial layer
◦ Lies directly beneath epidermis
◦ Houses nerve endings (corpuscles) that provide body with
sense of touch - pain ,heat, pressure.
◦ Contains papillae, small, cone shaped projections of elastic
tissue that point upwards.
◦ Papillae contain looped capillaries or nerve fiber endings.
44. 2 . Reticular layer : deeper layer
◦ Contains fat cells, blood and lymph vessels, oil and sweat
glands, hair follicles, arrector pili muscles.
45. SUBCUTANEOUS
◦ The subcutaneous tissue (also Hypothermis ) is not part of
the skin , and lies below the dermis of cutis.
◦ Its purpose is to attach the skin to underlying bone and
muscle as well as supplying it with blood vessels and nerves.
◦ It consists of loose connective tissue, adipose tissue and
elastin.
◦ The main cell types are fibroblasts, macrophages and
adipocytes (subcutaneous tissue contains 50% of body fat) .
Fat serves as padding and insulation for the body.
46. FUNCTION
1. Protection from harmful agent
2. Protection from injury and radiation
3. Covering of the body
4. Synthesis of vitamin D
5. Excretion of some waste product
6. Maintain body temperature by sweating
7. Synthesis of serum to make smoothness of skin
