Structure of eye

The eye is a very complex organ that sends a huge amount of information to the brain. It has a very specific design to capture and analyze light. In its simplest description, the eye is a box, with a lens to focus the light that enters it, and cells to process the light.It is a window to our emotions, and some say, to the soul. Explore the complexities of the human eye.

                                                         fig. Structural of human eye.

Optic nerve :
                 This carries the impulses generated by the retina to the brain to be turned into images in the   brain.

Retina :
          This is a membrane layer in the inside of the eye that contains rod cells (lets you see in the dark
          because they are sensitive to low light intensities) and cone cells (lets you see in bright light because its
          works best at higher light intensities).
          It converts the light into electric impulses to be sent to the brain via the optic nerve. This conversion is  
          called photoelectric conversion.

pupil : The pupil is actually the gap created by the iris.
           The pupil either dilates or contracts with the help of the iris.
           This controls the amount of light entering the eye so that the retina and lens doesn't get damaged.
           In bright light the pupil becomes small by relaxing the muscles in the iris in dim light it dilates (becomes
          big) by contracting the muscles in the iris.

Iris :    This is the muscle surrounding the pupil gap.This helps in dilating and making the pupil smaller.
           Its made up of radial and radial muscles (antagonistic pairs).The longitudinal muscles contract and the
           radial muscles relax to make the pupil big. The vise verse  happens to make the pupil smaller.
cornea :This is the transparent layer of the sclera, which is also thinner than the sclera, that covers the front    
             part of the eye (that is the iris, pupil, and anterior chamber of the eye).
             It has 2 functions. Its most important functions is to help in the double refraction of light tot he retina    
             with the help of the lens.
             The light first gets refracted by the cornea then this light travels to the lens to get refracted further      
            thereby bringing about vision. The other function is for it to act as a protection layer.

lens  :  This is an transparent organ in the inner eye that is filled with a liquid. It helps the refraction of light,
           with the help of the cornea, onto the retina.
           The lens helps in seeing far and near objects be contracting and relaxing with the help of the ciliary
            bodies (muscles) that are connected to them.
           The ciliary muscles contract to make the lens thin and help see distance objects by refracting the light
           accordingly on the retina.
           The ciliary bodies relax to make the lens fatten up to see near objects by refracting the light
           accordingly on the retina.
         When this method of lens contraction and relaxation malfunctions you get either short sightedness or
          near sightedness.
Ciliary body  :
                      Part of the eye between the iris and the choroid.
                   
                 

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Human ear

The ear is the organ that detects sound.
It not only receives sound, but also aids in balance and body position.
The ear is part of the auditory system.
It has external, middle, and inner portions.
The outer ear is called the pinna and is made of ridged cartilage covered by skin.
Sound funnels through the pinna into the external auditory canal, a short tube
 that ends at the eardrum (tympanic membrane).

Human Ear:
The human ear has three main sections, which consist of the outer ear, the middle ear, and the inner ear.
Sound waves enter your outer ear and travel through your ear canal to the middle ear.
The ear canal channels the waves to your eardrum, a thin, sensitive membrane stretched tightly over the entrance to your middle ear.
The waves cause your eardrum to vibrate.

The human ear can respond to minute pressure variations in the air if they     are in the audible frequency range, roughly 20 Hz - 20 kHz.
It is capable of detecting pressure variations of less than one billionth of atmospheric pressure.
The threshold of hearing corresponds to air vibrations on the order of a tenth of an atomic diameter.
This incredible sensitivity is enhanced by an effective amplification of the sound signal by the outer and middle ear structures.
Contributing to the wide dynamic range of human hearing are protective mechanisms that reduce the ear's response to very loud sounds.
Sound intensities over this wide range are usually expressed in decibels.

It passes these vibrations on to the hammer, one of three tiny bones in your ear.
The hammer vibrating causes the anvil, the small bone touching the hammer, to vibrate. The anvil passes these vibrations to the stirrup, another small bone which touches the anvil.
From the stirrup, the vibrations pass into the inner ear.
The stirrup touches a liquid filled sack and the vibrations travel into the cochlea, which is shaped like a shell.
Inside the cochlea, there are hundreds of special cells attached to nerve fibers, which can transmit information to the brain. The brain processes the information from the ear and lets us distinguish between different types of sounds.


The human ear can perceive frequencies from 16 cycles per second, which is a very deep bass, to 28,000 cycles per second, which is a very high pitch.
Bats and dolphins can detect frequencies higher than 100,000 cycles per second.
The human ear can detect pitch changes as small as 3 hundredths of one percent of the original frequency in some frequency ranges.
Some people have "perfect pitch", which is the ability to map a tone precisely on the musical scale without reference to an external standard.
It is estimated that less than one in ten thousand people have perfect pitch, but speakers of tonal languages like Vietnamese and Mandarin show remarkably precise absolute pitch in reading out lists of words because pitch is an essential feature in conveying
the meaning of words in tone languages.
The Eguchi Method teaches perfect pitch to children starting before they are 4 years old. After age 7, the ability to recognize notes does not improve much.

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Blood types

                                    Blood is a specialized fluid connective tissue in which there is liquid intercellular substance (plasma) and formed elements - (RBC,WBC and platelets ) suspended in the plasma which circulates in closed system of blood vessels. It is red , thick and slightly alkaline.
                     Blood is circulated around the body through blood vessels by the pumping action of the heart.
In animals with lungs, arterial blood carries oxygen from inhaled air to the tissues of the body, and venous blood carries carbon dioxide, a waste product of metabolism produced by cells, from the tissues to the lungs to be exhaled.

Blood is composed of -

                   A. Cellular substances:  45% (42%-45%)

                                                        1)  Erythrocytes or red blood corpuscles (RBC) 

                                                        2)  Leukocytes or white blood corpuscles (WBC)

                                                        3)  Platelets or thrombocytes. 

                   B. Liquid intercellular substance : i.e. plasma -55%(55%-58%) -

                                                                    Plasma contains -

1) Liquid( 91-92%)- water

2) Solid :(8-9%)

Blood 

Properties of Blood 

1) Blood volume : 5-6 liters

2) Normal reaction : Slightly alkaline , pH =7.36-7.45

3) Specific gravity : 1.052- 1.060

4) Viscosity : 4.5 times more viscus than water. 

5) Temperature : 36-38'c

6) Osmotic pressure : Average 25 mm of Hg .

7) Colour    : Red , due to presence of hemoglobin inside RBC.

8) Taste : Salty. 

Blood cell 

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Vitamins essential

Vitamin:

Vitamin means vital amine . Vitamin may be defined as a protent organic compounds which is found in food in variable  and minute quantity and must supplied to the animal organism from external sources, so that specific physiological function vital to life may go on normally .

*Vitamins * 

Depending upon their solubility in water , fat  and oils as well as fat solvent vitamins are divided into (two) 2 groups : 

• Fat soluble vitamins : Those present in fats and soluble in fat solvents ; Example: A,D,E & K .

• Water soluble vitamins : These are water soluble and includes vitamin B- complex   and vitamin C. It does   not stored in the body more than 48-72 hours except B12.

        Amount of daily required vitamins:
Vitamin A                                    - 5000 IU
Vitamin D                                     - 400 IU
Vitamin E                                      -15    IU
Vitamin K                                     -70    micro gm
Thiamine (B1)                                - 1.5   mg
Riboflavin (B2)                               -1.8   mg
Pantothenic acid (B)                      -   Unknown
Niacin                                           -20    mg
Folic acid                                      - 0.4  mg
Pyridoxine (B6)                             -2       mg
Vit.B12    3 micro mg
Vit. C or Ascorbic acid                 - 45 mg.

Different types of vitamins:

Vitamin A (Retinol and beta-carotene) 

 Vitamin B-complex 

 Vitamin B1 (Thiamine) 

 Vitamin B2 (Riboflavin) 

 Vitamin B3 (Nicotinic acid / nicotinamide) 

 Vitamin B5 (Pantothenic acid) 

 Vitamin B6 (Pyridoxine) 

 Vitamin B11 (Folic acid) 

 Vitamin B12 (Cobalamin) 

 Vitamin C (L-Ascorbic acid) 

 Vitamin D (Cholecalciferol / Ergocalciferol) 

 Vitamin E (Tocopherol) 

 Vitamin H (Biotin) 

 Vitamin K (Phylloquinone)

Essential food for vitamin supply 

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