The human body is made up of different parts. Some parts are inside the body while others are outside. Some parts of the body are the head, eyes, nose, ears, teeth, skin, hands, fingers, nails and feet.
Structure and parts of the hair
Each hair grows from a narrow tube in the skin called hair follicle. Each follicle has a tiny oil gland near its base (See fig. 3.3). The gland produces oil that lubricates the hair and softens the skin around it.
Functions of the hair
- It protects the head.
- It keeps the head warm in cold whether.
- It improves personal appearance and adds beauty to a person.
Types of hair
There are different hair types. These include:
- Dry hair: This is dry, dull and unattractive. It can result from insufficient production of oil by the oil glands, poor food, illness or damage to the hair as a result of improper care.
- Oily or greasy hair: This occurs when the oil glands are over-active and produce more oil than is needed.
- Soft hair: This type is often light and can easily be blown about by the wind.
- Tough or coarse hair: This is thick and could be difficult to comb or manage.
- Short hair: Some people can inherit short hair while others have long hair.
- Long hair: Some people have and wear long hair. This type of hair can also result from heredity, good food and proper care of the hair. Long hair can be kept tidy by plaiting and/or packing.
The eye is one of the five sense organs. It is for seeing. It is very important for normal life. It also affects the physical appearance.
Structure of the eye
The eye is made up of different parts. Each part performs a special function. An understanding of the different parts of the eye will help you take good care of your eyes.
Parts of the eyes
- The eyebrow: Prevents sweat from running down into the eyes.
- The eye lashes: Protects the eyes from dust and dirt.
- The eye lids: Can close to protect the eye from foreign objects.
- The eye balls: These are the organs of sight. Each is connected to the brain by the sensory nerve called optical nerve.
- Cornea: A protective layer. It keeps dust and dirt from passing through the pupil of the eye.
- The iris: The coloured part of the eye. It surrounds the pupil. It can increase or decrease the size of the pupil.
- The pupil: The hole in front of the eyeball through which light rays pass into the eye.
- The lens: A glass-like part of the eye. It focuses the light rays into one spot on the retina thus forming the image.
- The retina: A light sensitive spot where image is formed.
- Aqueous humour/Vitreous humour: Both keep the eye ball round. They enable the eye to maintain its shape.
- Tear gland: Pours out tear over the front of the eye. The tear washes away any dust which enters the eye.
The nose is one of the five sense organs. It is for smelling. It is very important for normal life. It affects the appearance of an individual.
Structure of the nose
The nose is the organ of smell. The very top of the nose consists of bone. The rest is made of cartilage, small muscles and skin lined with a fine moist mucous membrane. The lining of the membrane contains small glands which produce watery secretion. This secretion keeps the lining moist. The nose is divided into two nostrils by a partition called septum. The nerves of smell which run from the nose to the brain are called the olfactory nerves. There are tiny hairs at the entrance of the nose. They act as filters for the air that goes to the lung.
Functions of the nose
- It is the sense organ of smell.
- It acts as a passage or channel through which the air we breathe passes in and out of the lungs.
- The air entering the lungs is filtered and warmed by the tiny hairs at the entrance of the nostrils.
The ear is one of the five sense organs of the body. It is used for hearing and balance.
Structure of the ear
The ear is divided into three parts – the outer ear, the middle ear and the inner ear.
The outer ear is the part we see. It looks like a funnel. It picks sounds or vibrations. The vibrations are carried to the eardrum, which is between the outer ear and the middle ear. The sound then passes through the auditory nerve.
There are tiny hairs at the entrance of the outer ear. These trap dust and any tiny insects or objects that try to enter the inner parts of the ear. The passage also contains wax which further helps to trap the dust and other objects.
Functions of the ear
- It is the sense organ for hearing.
- It helps us to maintain balance.
Your teeth can affect your health and appearance. A set of clean strong and healthy teeth can make you look attractive. The teeth are also useful for chewing most of the food you eat, thereby aiding digestion. Human beings grow two sets of teeth. The first is the milk or temporary teeth during childhood. These are 24 in number. They loosen and fall out. They are replaced by the permanent teeth in adulthood. The permanent teeth are usually 32 in number.
When the teeth are neglected they can become infected. Such infection can lead to bad mouth odour and even serious illness, It is therefore very important that you take good care of your teeth.
Structure of the tooth
A tooth is made up of the following parts:
- The crown: the part of the tooth projecting above the gum.
- The root: the part buried in the jaw-bone.
- The neck: the space between the crown and the root.
- The dentine: the tough centre of the tooth which surrounds and protects the pulp cavity.
- The pulp cavity: contains blood vessels and nerves.
- The enamel: a very hard substance which covers the crown of the tooth.
Types of teeth and their functions
- The incisors: These are in the centre of the front of the jaw. They are used for cutting off lumps of food.
- The canine: These are beside the incisors. They are pointed and used for tearing food. They are sometimes called “dog” teeth.
- Premolars: These are next to the canine. Each has one or more points for cutting. They may also have flat surfaces for grinding food.
- Molars: These are behind the premolars. They are similar to the premolars. They are however only present in the permanent dentition. Children do not therefore have molars
The skin is the outer covering of the body. It performs very important functions. It is necessary to understand the structure of the skin and how to care for it.
Structure of the skin
The skin is made up of two main layers-the epidermis and the dermis or “true skin”.
A) The epidermis: This is the outer layer. It has no blood vessels or nerves. It is covered with hairs and tiny holes called sweat pores. Sweat or perspiration passes out through the pores.
B) The dermis: This is the inner layer of the skin. It is made up of the following:
- Sweat glands which produce sweat.
- Oil glands which produce oil that keeps the skin and hair fresh and soft.
- Blood vessels and nerves which keep the skin healthy and help it to perform its functions.
- Fat deposits which reduce heat loss from the body.
Functions of the skin
- It protects the body from bacterial infection (germs), poor weather and injury.
- It helps the body to get rid of waste products through sweating.
- It helps to keep the body temperature normal (i.e. at 98.6°F or 37°C), by producing sweat during hot weather. As the sweat dries up it cools the body.
- It also keeps the body warm in cold weather.
- When the sun shines on the skin, vitamin D is produced by the skin.
Types of skin
It is important to know your skin type. This helps you to know how to care for it properly.
There are the following types:
- Normal skin: is soft, clear, smooth and without spots or blemishes.
- Dry skin: is usually thin, sensitive and wrinkles easily, especially around the mouth and eyes. This can result from poor feeding, ill health, dry weather, and lack of care.
- Oily skin: is greasy and occurs when the oil gland produces too much oil.
- Combination skin (oily and dry skin): has some part of the skin oily e.g. the nose and fore-head, while other parts are dry e.g. the cheeks.
Hands, Fingers, Nails and Feet
The hands, fingers, nails and feet are very important parts of the body. We even put them into our mouths. The legs are in close contact with the ground, dust and dirt. They can also become hiding places for disease germs. The ways your hands, fingers, nails and feet are maintained and cared for affect your appearance. It is therefore very important that we take good care of these parts of the body.
- Dirty hands can harbour disease germs especially under the finger nails. And it is easy for the germs to pass from the hands to the mouth.
- Clean hands and feet are important for personal appearance.
- Dirty hands and feet can be repulsive to other people. People will not want to play, work or eat with a person that has dirty hands and feet.
- Dirty feet can harbour harmful disease germs.
These germs can lead to very serious diseases.
Structure of the hands, nails and feet
The hands and the feet are parts of the upper and lower limbs as shown in fig.3.9. The hand starts from the wrist. It is made up of the palm, the fingers and the nails. The first finger is called thumb.
The leg starts from the ankle and consists of the heel, sole, toes and nails. Each nail consists of:
- The nail plate.
- The nail crescent, which is the white crescent at the base of the nail plate.
- The cuticle which is the thin protective band of skin around the nail.
- The nail bed is the base of the nail.
Functions of hands and feet
- The hands and fingers are used for touching things.
- They are also used for doing different types of work.
- The legs give us support.
- The legs are used for walking about.
- The legs also perform many other useful activities, such as playing games, dancing, etc.