Category: 12th Zoology

Effects of solar radiation / UV radiation – Skin grafting

Post author By Mr. Padeepz
Post date October 1, 2018
No Comments on Effects of solar radiation / UV radiation – Skin grafting

Effects of solar radiation / UV radiation – Skin grafting

Effects of solar radiation / UV radiation

Invisible light forms a part of the electromagnetic spectrum
immediately beyond the violet end of the visible light spectrum (i.e. between
visible light and X-rays). Long wavelength ultraviolet light (i.e. that nearest
visible light) is often termed as UVA; intermediate wavelength ultraviolet light
is designated UVB; and short wavelength ultraviolet light (i.e. that nearest
X-rays) is called UVC.

The main source of UV radiation is the sunlight; others are UV lamps
and welder’ arcs. UV light penetrates the skin for a few millimeters only so
that its effect is limited to epidermis. In human excessive exposure to UV
rays can cause various forms of skin cancer such as squamous cell carcinoma,
basal cell carcinoma and malignant melanoma.

The efficiency of UV light as carcinogen depends upon the extent of light-absorbing protective melanin pigmetation of the skin. Fair skinned people and whites are more prone to skin complications due to UV exposure. People living close to the equator, outdoor workers and farmers in Tropics are exposed to light radiations.

Skin grafting

Skin grafting is a technique used in plastic surgery to repair areas of
lost or damaged skin. A piece of healthy skin is detached from one part of
the body and transferred to the affected area. New cells grow from the graft
and cover the damaged area with fresh skin.

Skin taken from an identical twin can be used for a graft, but skin from
another person or an animal is soon rejected by the recipient body. A skin
graft is performed because the area is too large to be repaired by stitching or
because natural healing would result in scarring that might be ugly or restrict
movement.

Most grafts are performed by removing skin from the donor site and
transferring to the recipient site.

Melanin functions

Melanin is the brown black, non-haemoglobin-derived pigment
normally present in the hair, skin choroid of the eye, meninges and adrenal
medulla. It is synthesized in the melanocytes and dendritic cells, both of which
are present in the basal cells of the epidermis.

Melanin is stored in the form of cytoplasmic granules in the phagocytic cells called the melanophore, present in the under lying dermis. Melanocytes possess the enzyme tyrosinase necessary for the synthesis of melanin from the amino acid called tyrosine Tyrosine tyrosinase Melanin

Various disorders of melanin pigmentation cause generalized and
localized hyperpigmentation and hypopigmentation.

Generalized hyperpigmentation

a) In Addison’s disease, there is generalized hyperpigmentation of the skin,
especially in areas exposed to light and buccal mucosa.
b) Hyper pigmentation on skin of face, nipples and genitalia during pregnancy
under the influence of oestrogen.
c) In chronic arsenical poisoning, there is characteristic rain-drop pigmentation
of the skin.

Generalized hypopigmentation

Albinism is an extreme degree of generalized hypo pigmentation in
which tyrosinase activity of the melanocytes is genetically defective and no
melanin is formed. Albinoes have blonde hair, poor vision and severe
photophobia. They are highly sensitive to sunlight. Chronic sun exposure
may lead to pre-cancerous lesions, squamous and basal cell cancers of the
skin.

Localised hypopigmentation

a) Leucoderma is a form of partial albinism and is an inherited disorder.
b) Vitiligo is local hypopigmentation in the skin.
c) Acquired local hypopigmentation can result from various causes such as
leprosy, healing of wounds, radiation dermatitis, etc.

Skin – Functions of skin

Skin

The skin is a major organ of the body forming 8% of its total mass
and having an area between 1.1-2.2m2. It is the major interface between the
body and the environment and covers the entire surface. It is continuous with
mucosae at the various orifices and with lining tissue of organs like eyes and
ears

Various structures including sebaceous glands, sweat glands, hair
follicles and nails are formed by modifications of epidermis. Sebaceous glands
secrete an oily substance called sebum and open on the sides of the hair
follicles. Sweat glands are of two types, Merocrine and Apocrine. Merocrine
glands are found throughout the body opening on the surface and secreting a
clear watery fluid. Apocrine glands are found in the regions like axilla, areola,
pubis, scrotum and perianal regions. Their ducts may open on the surface or
into the hair follicle.

Dermis is made up of connective tissue consisting of matrix in which is
embedded elastic and collagen fibres to give strength and elasticity. It also
provides a compartment for blood vessels, lymphatics, nerves and cells
associated with immunity. Receptors for the sensations such as touch, pain,
pressure, warmth, cold and vibration senses are also found in the skin.
Circulation through the skin serves two major functions nutrition and
conduction of heat to the environment.

Functions of skin

1. Skin forms an effective barrier against infection by microbes.
2. It prevents dehydration and provides defense against chemical, osmotic,
thermal and photic damage.
3. It limits and regulates heat loss.
4. It provides a major sensory surface with a range of receptors.
5. It has limited excretory and absorptive functions.
6. Skin also helps in the formation of vitamin D.
7. Its keratinization and high friction coefficient gives the skin a
characteristic texture and helps in movement and handling of various
substances.

Hearing Aid – Noise pollution

Post author By Mr. Padeepz
Post date September 27, 2018
No Comments on Hearing Aid – Noise pollution

Hearing Aid – Noise pollution

Hearing Aid

Patients with a conductive defect which does not respond fully to
treatment may be helped with a hearing aid.
A hearing aid is an electronic, battery-operated device that
amplifies and changes sound to allow for improved communication. Hearing
aids receive sound through a tiny microphone, which then
converts the sound waves to electrical signals. The amplifier increases the
loudness of the signals and then sends the sound to the ear through a speaker
in an ear piece which fits into an outer ear canal. The electric signals are
converted back to sound waves.

A volume control on the aid usually operated by turning a tiny wheel
enables the level of incoming sound to be adjusted.
More powerful aids that amplify sound to a greater
degree are available. In these aids the microphone, amplifier and
battery are contained in a larger case worn on the body; the currents is
carried to the ear piece by a thin wire. Some people with conductive
deafness especially if there is an infection or discharge in the ear canal may
be given a bone condution hearing aid. This type of hearing aid may be fitted
to a glass frame or hair band.

Other devices available for the hard-of-hearing include
amplified telephone receivers, flashing lights instead of door bells and
telephone bells, vibrators that respond to sound, head phone for
television sets, teletype writers and guide dogs for the deaf.

Noise pollution

The term noise is derived from the Latin word Nausea refering to the
feeling of sickness in the stomach with an urge to vomit. Any unpleasant and
unwanted sound is considered as noise. It is one form of pollution. Noise
pollution can be defined as unwanted or offensive sounds that unreasonably
intrude into our daily activities. It is responsible for various adverse effects.
In recent years noise is recognized as a major pollutant on par with other
chemical pollutants of air, water and biosphere. Noise has many harmful
effects on man and the damage incurred is irreversible.

There are various sources of noises and the sources are broadly
classified into industrial sources and non industrial sources. The noise dumped
into the atmosphere by the industires due to the functioning of machineries
form the industrial sources. On the other hand the noise associated with
urban development; road, air and rail transport; loud speakers, radio and
television stations, construction sites, neighbourhood and recreational noise
levels, and activities associated with urban living generally lead to increased
noise levels.

Sound is measured by several complex systems. The best known
unit of measurement is the measurement of sound in decibel which is named
after Sir Alfred Bell. The industrial noise survey of India recognized noise
levels from 81dB to 120dB as permissible levels.

Loud noises (above 130 dB) can cause immediate and permanent
damage to the muscles in the middle ear, altering the stiffness of the ossicles,
damaging the hair cells of the cochlea and casuing the rupture of ear drum
thereby reducing the efficiency of hearing.

Prolonged exposure to unpleasant noises may lead to severe mental
distubances and violent behaviour. Noise is also partially responsible for the
increased consumption of alcohol, drugs, tranquillzers and sleeping pills. Noise
pollution further contributes to a few cardiovascular problems. Peptic ulcers
and asthma are aggravated. Small vessels to glomerular circulation are
subjected to vaso constriction and ultimately the output of urine is reduced.

Persons exposed to excessive noise at work place have temporary
impairment of hearing.

Defects of the ear

Several defects of the ear lead to hearing loss or even deafness.
Hearing loss, or hearing impairment, happens when there is a problem with
one or more parts of the ear or ears.

Types of Hearing Loss

There are a few different types of hearing loss: conductive, sensory, mixed (conductive and sensory combined), and neural. Conductive hearing loss:- This happens when there is a problem with a part of the outer or middle ear. Most kids with conductive hearing loss have a mild hearing loss and it is usually temporary because in most cases medical treatment can help. (Defects of the ear)

Sensory hearing loss

This happens when the cochlea is not working correctly because the tiny hair cells are damaged or destroyed. Depending on the loss, a person may be able to hear most sounds (although they would be muffled); only some sounds; or no sounds at all. Sensory hearing impairment is almost always permanent and the ability to talk normally may be affected. (Defects of the ear)

Neural hearing loss

This happens when there is a problem with the connection from the cochlea to the brain. The hearing loss may be congenital or due to middle ear fluid, serious
infections, such as meningitis, head injury, listening to very loud music,
especially through headphones, repeated exposure to loud sounds, such as
machinery.

One of the common causes of conductive hearing loss is blockade of
the external auditory meatus with wax secreted from ceruminous glands in
the skin lining the meatus. In some people wax accumulates in the meatus
and hardens, sometimes pressing against the eardrum. Normal hearing is
usually restored after the hardened wax is removed with a special syringe.

Another cause of conductive hearing loss, is a perforated eardrum.
Perforation can be caused by infection in the middle ear or by
mechanical injury resulting from a nearby explosion or a sudden blow to the
head. Injury to the head can also cause the ossicles of the middle ear to
become disconnected from one another, thus breaking the
conductive path to the cochlea. (Defects of the ear)

Malfunction of the cochlea and acoustic nerve can be the cause of
hearing loss, even though vibrations are conducted perfectly into the inner
ear. Such hearing loss is called sensorineural (perceptive) hearing loss.
Acquired forms of this condition can result from infection, head injury, blast
from explosions or exposure to excessive noise. (Defects of the ear)

Mechanism of hearing

Functions of External Ear

Sound waves enter the external auditory meatus, pass along the external eustachian canal and fall on the tympanic membrane (TM). This causes the TM to vibrate. (Mechanism of hearing)

Functions of Middle Ear

The middle ear is an air filled cavity in the temporal bone which opens via the eustachian tube into the nasopharynx. The auditory tube opens during chewing, swallowing and yawning thus keeping the pressures on both sides of the tympanic membrane equal.

The three auditory ossicles are localised in the middle ear. Of these,
the malleus is attached to the TM, and the stapes to the membranous oval
window on the medial wall. Incus articulates with these two bones. Thus
vibrations of the TM are transmitted to the oval window. As the TM has an
area of 90mm2 and the foot plate of the stapes 3.2mm2 and the lever system
formed by the ossicles multiplies the force 1.3 times. (Mechanism of hearing)

The vibrations of the oval window generate pressure waves in the
fluid filling the vestibular canal. The pressure waves pass to the median canal
and vibrate the basilar membrane. The tympanic canal is connected to a
circular membrane called the round window just beneath the oval window.
This arragement allows the pressure waves to transmit through the cochlear
fluid. (Mechanism of hearing)

Functions of Cochlea

The inner ear (labyrinth) is made up of the cochlea and the vestibule. The cochlear portion of the labyrinth is a tubule coiled 2.75 times. Throughout its length the cochlea is divided into three compartments by the basilar and the Reissner’s membranes. (Mechanism of hearing)

The middle compartment (scala media) contains endolymph and the other two (scala vestibuli & scala tympani) contain perilymph.

Organ of Corti

Located on the basilar membrane is the Organ of Corti which
contains the auditory receptors. Four rows of hair cells arise from the basilar
membrane. (Mechanism of hearing)

Stimulation of hair cells

Movements of the foot plate of the stapes set up a series of waves in the perilymph of the scala vestibuli. This in turn causes vibrations of the vestibular membrane and hence of the endolymph in the scala media. These waves deflect the Reissner’s membrane and this in turn produces disturbances in the basilar
membrane which bend the hairs of hair cells in the organ of Corti. This leads
to development of action potentials in the related nerve fibres which are
transmitted along the auditory nerve. (Mechanism of hearing)

The site of maximum distortion in the organ of Corti is
determined by the frequency of sound, for high pitched sounds the
maximum height of the waves is near the base of the cochlea and for low
pitched near the apex. The extent of distortion is determined by the loudness
of the sound. Interpretation of these impulses is made in the auditory cortex.

Sound waves ® vibrate tymphanic membrane ® movements in ear ossicle
chain ® vibration of oval window ® waves in perilymph (scala vestibuli) ®
waves in endolymph ® deflection in the Reissner’s membrane ® basilar
membrane disturbed ® bending of hair cells ® action potential ®
transmission by auditory nerve. (Mechanism of hearing)

EARS

Our ears provide us with two vital but very different senses : hearing
and balance. Sound detected by the ears provides essential information about
our external sourounding and allow us to communicate. In addition our ears
contribute to our sense of balance to maintain upright posture and move
without falling over.

Sound is the sensation produced by longitudinal vibrations in the
external environment. Loudness of sound is correlated with amplitude of sound
wave and pitch with frequency (No.of waves / unit time). Audible
frequencies to humans is in the range 20 – 20,000 cycles per second (cps,
Hz). Only the young people are able to hear this full range.
Sound perception depends on the loudness as well as frequency.

The human ear is most sensitive to 50 – 5000 Hz range. But most sounds we
normally hear fall within 500 – 5000 Hz. Since the human ear can differentiate a wide range of sound energy (the loudest noise perceived is
approximately 1012 times more intense than the softest whisper) the decibel
(dB) scale is used to measure the intensity of sound.

Our ability to hear depends on a complex series of events that occur
in the ear. Sound waves in the air are transmitted as vibrations through a
series of structures to the receptor for hearing. The physical vibrations are
detected and converted into electrical signals. Nerves carry the electrical
signals to the brain where they are interpreted. The interpreted messages
allow us to perceive the subtleties of sounds such as speech and music.

Eye Infections and Eye Care

Post author By Mr. Padeepz
Post date September 26, 2018
No Comments on Eye Infections and Eye Care

Eye Infections and Eye Care

Eye Infections

1. Stye

A stye is an acute infection of the glands located at the eyelid
margin. There is swelling, pain, itching and redness in a small area at the lid
margin. Treatment consists of using frequent warm compresses on the eye. (Eye Infections)

2. Conjunctivitis:

Infection in the conjuctiva is called conjunctivitis. Due to
the infection the invisible blood vessels within the conjunctiva become
engorged. Inflammation of the conjuctiva causes redness, discomfort and a
discharge from the affected eye. The most common causes for
conjunctivitis are infections (in children) and allergy (in adults). (Eye Infections)

2a. Infective conjunctivitis :

Most conjunctival infection are caused by
bacteria (e.g staphylococci) and are spread by hand-to-eye contact or by
viruses associated with a cold, sore throat, or illness such as measles, viral
conjunctivitis sometimes occurs in epidemics, spreading rapidly through
schools and other groups. (Eye Infections)

2b. Allergic conjunctivitis :

An allergic response of the conjunctive may be
provoked by a variety of substances including cosmetics (mascara),
contact lens cleaning solution and pollen. (Eye Infections)

Symptoms

All types of conjunctivitis cause redness, irritation,
itching, discharge and occasionally photophobia (abnormal sensitivity to bright light). In infective conjunctivitis the discharge contains pus and may cause
the eyelids to be stuck together in the morning. In allergy conjunctivitis the
discharge is clear and the eyelids are often swollen. (Eye Infections)

Treatment

Warm water is used to wash away the discharge and remove
any crust on the eyelid. Infections are treated with eye drops or ointment
containing an antibiotic drug. Allergic conjunctivitis may be relieved by
use of eye drops containing an anti histamine drug. (Eye Infections)

Eye care

Eye is an important organ and it is to be taken care of.

1. Eye examination should be periodically done to determine the cause of
visual disturbance or other symptoms relating to the eye.

2. Foreign particles in the eye are very common and it may penetrate in the
eye ball. So care should be taken while removing the dust to avoid damage.

3. The retina should be periodically examined to assess conditions such as
hypertensive retinopathy for hypertension and diabetic patients.

4. Self medication should be avoided. A doctor should be consulted immediatly
if there is any sudden pain or blurry vision.

Cataract – Lens Replacement – Glaucoma – Nyctalopia

Post author By Mr. Padeepz
Post date September 26, 2018
No Comments on Cataract – Lens Replacement – Glaucoma – Nyctalopia

Cataract – Lens Replacement – Glaucoma – Nyctalopia

Cataract

Cataract is the opacity in the lens of the eye. The normal lens allows
light to reach the retina when it becomes opaque and does not allow light to
reach the retina, the person is unable to see clearly. Cataract is due to
(coagulation) changes in the delicate protein fibres within the lens, cataract
never causes complete blindness but causes increased loss of transparency.
The clarity and the detail of the image is progressively lost. The front part of
the lens becomes densely opaque and whiteness is visible in the pupil.
The causes for cataract formation in the adult is related to aging, sun
light exposure, smoking, poor nutrition, eye trauma, systematic diseases like
diabetes mellitus, infection and injuries and certain medications such as
steroids. Sometimes German measles in pregnant mothers causes cataract in
the child.

To delay the onset of cataract one should have nourishing diet,
protect eye from excessive exposure to sun rays, X-rays, intense heat and
injuries. Diseases like diabetes and syphilis should be treated early and
effectively.

Two types of cataracts are dense nuclear cataract (cataract in the
center of the lens) and Peripheral cataract (cataract in the periphery of the
lens). There is no medical treatment for cataract. The only treatment is
surgery. Once the cataract is removed, the eye is unable to focus, as there is
no lens. So one has to use an artificial lens. This can either be glasses,
contact lenses or insertion of introcular lenses.

Today modern medical advances have made cataract surgery very
successful. New surgical techniques and intracular lenses can restore
excellent vision (97%).

Lens Replacement

For individuals who are over 40 years of age, considering refractive
surgery to decrease dependence on glasses and contact lenses, Clear Lens
Replacement (CLR) is an exciting option. In essence, this procedure entails
removing the natural lens of the eye and replacing it with an intraocular lens
(IOL) implant.

CLR may be an excellent alternative to these procedures for people
already wearing bifocals since CLR requires removal of the natural lens of
the eye, the patient is subsequently unable to focus (accommodate) at near
by objects . This is why CLR is best suited for patients over 40 who are
already wearing bifocals. One potential solution to this problem of
accommodative loss is implantation of the multifocal IOL (Intra Occular Lens)
implant. This implant allows focusing at both near and far objects.

Glaucoma

Glaucoma is a serious disorder of the eye and is a common cause of
blindness. Increased IOP (Increased Occular Pressure) compresses the
optic nerve at the optic disc with degeneration of optic nerve fibres and
cupping of the optic discs with progressive loss of visual acuity starting with
peripheral vision. The retinal artery which enters the eye ball at the optic disc is compressed causing retinal degeneration. In most cases the cause of
glaucoma is unknown but in some cases it may be due to infection or trauma
in the eye. When the IOP is very high (50-70 mm Hg) blindness occurs
within few days.

Nyctalopia

Vitamin A is necessary for resynthesis of visual purple. Nyctalopia
or night blindness is the first sign of vitamin A deficiency. Prolonged
deficiency of vitamin. A leads to degenerative changes in rods and cones and
nervous layers of the retina. Administration of vitamin A before degenerative
changes occur will restore retinal functions. Normal retinal function also
requires the presence of optimal amounts of other vitamins especially the B
complex just as other nerve tissues do.

Optometry – Retinopathy

Optometry

The practice of assessing vision and establishing whether glasses or
contact lenses are needed to correct any visual defect is known as optometry.

The eyes are examined by a qualified optometrist who will assess
the errors of refraction, prescribe and supply glasses or contact lenses
to correct it. Optometrists are not qualified to diagnose or treat disorders of
the eye but will refer patients requiring further to an ophthalmologist.

Retinopathy

Retinopathy is the disease of the retina, usually resulting from either
diabetes mellitus or alternatively from persistent hypertension (high blood
pressure). There are two types of retinopathy.

(1). Diabetic retinopathy is characterized by tiny aneurysms (baloon like
swellings) of the capillaries (tiny blood vessels) in the retina. New abnormal
blood vessels which are fragile and bleed readily grow on the retinal surface.
Haemorrhage into the vitreous humour may occur, fibrous tissues can also
grow forward into vitreous humour. Treatment by laser surgery can often halt
a progress of the conditon.

(2). Hypertensive retinopathy is characterized by narrowing of the retinal
arteries. Areas of the retina may be destroyed and causes haemorrhage and
white deposits may also occur in the retina. It may even lead to retinal
detachment. Remedy is laser treatment.

Effects of solar radiation / UV radiation – Skin grafting

Effects of solar radiation / UV radiation

Skin grafting

Related Topics in Zoology:

Melanin functions

Generalized hyperpigmentation

Generalized hypopigmentation

Localised hypopigmentation

Related Topics in Zoology:

Skin

Functions of skin

Related Topics in Zoology:

Hearing Aid – Noise pollution

Hearing Aid

Noise pollution

Related Topics in Zoology:

Defects of the ear

Types of Hearing Loss

Sensory hearing loss

Neural hearing loss

Related Topics in Zoology:

Mechanism of hearing

Functions of External Ear

Functions of Middle Ear

Functions of Cochlea

Organ of Corti

Stimulation of hair cells

Related Topics in Zoology:

EARS

Related Topics in Zoology:

Eye Infections and Eye Care

Eye Infections

Symptoms

Treatment

Eye care

Related Topics in Zoology:

Cataract – Lens Replacement – Glaucoma – Nyctalopia

Cataract

Lens Replacement

Glaucoma

Nyctalopia

Related Topics in Zoology:

Optometry – Retinopathy

Optometry

Retinopathy

Related Topics in Zoology: