Science3

System of Human Body

Skeleton System

The Human body is supported on an interna skeleton consisting of 202 long,short and irregular bones.These are joined together in several modes.The main function of the skeleton are :

To stiffen the body;

To provide levers upon which muscles of the body work;

To give shape to the body and

To protect the internal organs.

Muscular System

Muscles are thik at the centre and thin at the ends.

In the human body there are over 300 muscles.These are of Two types :

1.Voluntary Muscles ; these are under our control,such as muscles of head,legs,neck,etc these cause the external movements of the body.These are situated on the bones.

2.Involuntary Muscles : These are not under our control or will,such as lungs,heart,kidnys,etc.These cause the internal movements of the body.These are situated on the wall of the internal organ.

Circulatory System

This consist of Heart and Blood vessels which by carrying blood to all part of the body ,supply nourishment to the various tissues,and by bringing it back ,remove the waste products of the body.

The heart, by contraction ,pumps the blood into vessels called arteries which carry the blood to every tissues.

In the substance of every organ,the arteries divide into a very fine network of extremely small hair like tubes called capillaries.

Through the wall of capillaries ,the organs receive nourishment.

The capillaries reunite and pour the blood into veins which carry the blood containing waste product back to the heart.

The impure blood gather from all part of the body on the right auricle of the heart,from where it is purified by the oxygen breathed in.

The purified blood then goes to the left hand side of heart.Finally then blood is back from where it started.

The process goes on again and again till our last breath.

Heart

Heart is a Muscular conical organ located in the rib cage in between the two lungs.

Its weight is about 300 gram in male and 200 gm in female.

The heart is divided into four chambers.The lower two chambers are called ventricles.

The right auricle receive the impure blood and the left auricle receive pure blood.

The left ventricle pumps the pure blood to various parts of the body through the aorta.

When the ventricle are full of blood this condition is called diastole.The contracted condition of the ventricles is called systole.

The diastole and systole alternates and this is called the heart beat.

A healthy human heart beats for 70-80 times.

The blood is forced out of the heart this can be felt in the artery near the wrist.This is called the pulse(70-80 in one munite)

The pulse recorded by stethoscope.

Function of the Lungs

The main function of the lungs are :

To purify the blood,i.e., to separate the carbon-di-oxide and water vapour from blood;and

to give oxygen to the blood.

Digestive System

It consists of a very long(31 feet) tube,known as alimentary canal.

Its main parts are mouth,gullet,stomach,small intestines and large intestines.

The digestive fluids such saliva,gastric juice,bile and intestinal juices are poured in the canal by the neighbouring glands and walls of the tubes itself while the food is passing through the various regions.

The objects of the digestion is to convert the food into a fluid state so that it is capable of being absorbed by the blood.

Saliva

It is secreted by the three pairs of salivary glands situated in the mouth.

It is alkaline in reaction and contains a ferment which convert starch into sugar.

Gastric Juice

It is secreted by gastric glands in the stomach.

It converts insoluble proteins into soluble proteins and coagulates milk.

Stomach

Its main Functions are :

to stop the action of saliva,a juice which converts starch into sugar.

Convert starch into sugar.

to change insoluble protein into soluble protein and

to coagulate milk.

Bile Fluid

It is a greenish alkaline fluid poured into duodenum (part of small intestine)by the liver through the gal bladder.

It is antiseptic and emulsifies fat and food.

Pancreatic Juice

It is secreted by pancreas which are situated in the bend of duodenum.

It secretes insulin which acts upon the carbohydrates,the fat and proteins.

It digests food and keeps sugar balance in the body.

It is the biggest organ of the body.

Liver

It is dark red in colour and weight about 40 to 60 ounce.It is the largest gland in the body.

It nhelps in digesting food.Its main functions are :

to acts as a store of digested sugar for use when required in the body.

to help in digesting food.

to separate nitrogenous waste,and to kill poisons produced in the body.

Respiratory System

The respiratory system in the human body is an apparatus to get oxygen into the blood and carbon dioxide out of it.

The system consists of two lungs and the passages leading to lungs ,a nose ,wind pipe,etc.

When the diaphragm (in the body)contracts ,a large cavity is formed in the throat.

In order to fill up that cavity ,fresh air from the nostrils is sucked in and this is called respiration.

Now the diaphragm comes to its real form and cavity becomes smaller and we exhale the impure air and expiration takes place.

Excretory System

Kidneys and skin are the chief organs of excretion.

They throw out the waste product of the body in the form of urine and sweat respectively.

Kidneys are two in numbers.

They filter the nitrogenous wastes of the body from the blood and throw them out in the form of urine.

Urine filtered by kidneys is stored in the bladder.

Skin is the outer covering of the body,its main functions are :

to protect the inner organs.

to regulate the temperature of the body,to acts as the organ of the touch.

to throw out the nitrogenous waste;and to give shape to the body.

Nervous System

The system consist of nerves,brain and spinal cord.

They control the working of various organs of the body.

The brain controls thought ,memory,intelligence,etc.

The spinal cord controls the reflex action and works when brain is asleep.

This part is called Autonomic Nervous System.

Cerebrum:It is the seat of memory coordination and intelligence in brain.

It is the largest part of brain.

Reproductive System

There are certain organs in the body which are set apart for the reproduction of the species.

They are of different types in male and females.

Sex determination :

Sex chromosomes determine the sex in human beings.

In males there are 44+ XY chromosome,whereas in female there are 44+ XX .

44 represents autosomes and X and Y chromosome determines the sex in human being.

The sex is established at the time of fertilisation.If male gamete with y-chromosome undergoes fusion with female gamet with X-chromosome the zygote will have XY chromosome and the child born would be a male.

If male gamet with X-chromosome undergoes fusion with female gamete having X chromosome ,the zygote will have XX-chromosome and the child born would be a female.

Blood

Blood is a connective tissue which is made to circulate by the muscular pumping organ,the heart.

In about human beings,there is 5.5 to 6 liters of blood.

Plasma (fluid part of blood)consists of RBC,WBC and blood platelets.

Red Blood Corpuscles(RBC)

Red Blood Corpuscle(RBC) or Erythrocytes number is about 5 to 5.5 million in 1 ml blood.The total number is about 30 billion.Each RBC is devoid of nucleus.

RBCs contain haemoglobin that consists of globin and Fe2,i.e. heme

100 ml of blood contains 15 mg of haemoglobin.An individual may suffer from anaemia if the haemoglobin is lesser than this specified amount.

Haemoglobin carries oxygen to different cells of the body and brings carbon dioxide from the cells.

Life span of RBC is 120 days.

White Blood Corpuscles(WBC)

The number of leukocytes is 5000-6000 in 1 ml of blood.

The total number of WBC is about 75 million.

The number of leukocytes increases in infections like pneumonia,blood cancer(Leukaemia)etc.

These contains nucleus.

Plateletes

These are small and without nucleus.

Their number varies from 0.15 to 0.45 million in 1 ml of blood.

Their normal life span is one week.

These help in blood cloting at the site of injury by liberating thromboplastin

Blood Pressure

The normal blood pressure of a person is 120/80 mm of Hg.

During contracted or systolic condition it is 120 and during diastolic it is 80.

The maximum normal blood pressure should not exceed 150 in males and 140 in females.

The blood pressure is measured by sphygmomanometer

Arteries

Blood flows from heart to body.

Mostly oxygenated blood flows throw the veins except in pulmonary artery.

Veins

Blood flows body organs to heart.

Mostly de-oxygenated blood flows through the veins except in pulmonery vein.

Gene

It is a unit of Hereditary information and responsible for inheritance from one generation to nest.

This word was coined by Johnson.

A little bit or segment of DNA is called gene.

Diseases

Diseases caused by Virus :

Chickenpox,Smallpox,Common Cold,Influenza flu,Measies,Mumps,Viral Encephalitis,Polomyelitis,Rabies,Dengue fever,Acquiredd Immuno Deficiency Syndrome(AIDS)

Diseases caused by Bacteria :

Diphtheria,Pneumonia,Tuberculosis,Plague,Tetanus,Typhoid,Cholera,Bacillary,Dysentery,Whooping Cough,Gonorhoea,Syphilis and Leprosy

Diseases caused by Protozoans :

Malaria,Amoebic Dysentery,Kala-Azar,Sleeping Sickness,Diarhoea

Diseases caused by Fungi :

Ringworm,Athlete's foot

Nutrients

Nutrients and their functions

The principles of a healthy balanced diet:

Foods provide us with energy in the form of calories (Kcal). Calories effectively act as the fuel that powers our bodies and enables us to function, in the same way that petrol fuels a car. Some foods provide us with more energy than others, but by eating a wide variety of foods in the correct balance we can meet our requirements. Foods that provide many nutrients relative to the amount of energy they contain are known as “nutrient rich” foods e.g. milk and dairy foods. Energy requirements vary depending on age, sex, size, metabolic rate and activity level. If we consume more energy/calories than we need, we deposit the excess energy in the form of fat or adipose tissue. Conversely if we use more energy than we consume we use up fat to provide us with more energy.

Carbohydrate

Carbohydrates can be divided into two broad categories: available carbohydrate and unavailable carbohydrate.

Available carbohydrate

Sugars and starch are categorised as available carbohydrate.

Sugars are present naturally in fruit, vegetables and milk and are also added to many processed foods such as confectionery, cakes and biscuits.

Starch is found in foods such as bread, cereals and potatoes.

Both starch and sugars are digested in the body and converted to simple sugars (mainly glucose), which are then used by the body to provide energy.

Unavailable carbohydrate

Unavailable carbohydrate includes dietary fibre or NSP (non starch polysaccharide). The term “unavailable” is used because fibre can’t be digested and therefore doesn’t provide us with energy. However it is helpful in many other ways described below.

Dietary fibre can be divided into two categories: insoluble fibre and soluble fibre.

Insoluble fibre

Insoluble fibre (found in wholegrain cereals and grains, and some fruits and vegetables) adds bulk to the contents of the gut, speeding their transit and it is thought to help protect against constipation and other bowel disorders

Soluble fibre

Soluble fibre (found in pulses such as beans and lentils, fruit, vegetables and also oats, barley and rye) helps to reduce blood cholesterol levels and to regulate blood sugar levels.

At present the average intake of fibre in the UK is 14g/day in adults. Experts recommend that fibre intakes should be as high as 18g/day.

Consumption of brown, wholegrain, wholemeal and high fibre varieties of carbohydrate will help to increase fibre intake.

Protein

Proteins are essential for growth and maintenance of body tissues and for the production of substances such as hormones and enzymes which help to control many functions within the body. If insufficient carbohydrate and fat are available in the diet, then protein may also be used to provide the body with energy.

Proteins are made from building blocks known as amino acids.

There are 20 different amino acids.

Some amino acids can be made in the body and others can only be supplied by the diet -these are known as the essential amino acids.

Some foods are better providers of these amino acids than others. Those which contain all the essential amino acids are known as “high biological value” foods e.g. milk and dairy foods, meat, eggs etc.

Those which contain fewer of the essential amino acids are known as “low biological value” foods e.g. cereals, beans, lentils and nuts.

However if a wide variety of foods are consumed in the correct proportions the different protein sources can work together to provide the ideal levels of the different amino acids.

Fat

Fats are essential for many reasons:

They are a provider of energy

They are involved in forming cell membranes

They are a vehicle for the provision of fat soluble vitamins such as Vitamins A, E, D and K

They are involved in making hormones

They provide insulation; keeping us warm.

They provide us with a shock absorbing, protective layer

Fats are made from building blocks called fatty acids.

There are three types of fatty acids - saturated, monounsaturated and polyunsaturated fatty acids.

The fat in food contains a mixture of all three fatty acids, in different proportions in different foods.

Saturated fats

Foods that contain the higher proportion of saturated fatty acids include fats and oils (e.g. butter, hard margarine, some blended cooking oils), meat and its products (e.g. pies, lard, suet), whole milk and its products, coconut and palm oil.

Monounsaturated fats

lives, olive oil and rapeseed oil are the best providers of monounsaturated fatty acids.

Polyunsaturated fats

Fats and oils containing large amounts of polyunsaturated fatty acids are derived mainly from seeds and nuts and include pure sunflower, safflower, sesame, soya, corn oils, and sunflower and soya margarine.

Two polyunsaturated fatty acids, linoleic and alpha-linolenic acids cannot be made in the body and must be provided in the diet. These are called essential fatty acids.

These essential fatty acids are known as the "parent" fatty acids of 2 families of unsaturated fatty acids. The parent fatty acids undergo various different chemical reactions to produce the different fatty acids within each family, which have numerous different and important functions within the body.

Linoleic acid is the parent fatty acid of the n-6 family of fatty acids and alpha-linolenic acid is the parent fatty acid of the n-3 family of fatty acids.

Vegetable oils, eggs and poultry are good providers of n-6 fatty acids which are important for the formation of membranes in the body.

Unrefined fish oils and oily fish such as salmon, mackerel and sardines are good providers of n-3 or Omega 3 fatty acids which are important for the correct formation of nerves and have been linked to numerous health benefits such as reduced risk of cardiovascular disease and improved brain function.

Experts advise that too much fat, in particular saturated fatty acids, may lead to raised levels of blood cholesterol in some people which, in turn, is a risk factor for coronary heart disease.

As a result, government guidelines recommend that fat should provide no more than 35% of daily food energy, with saturates providing no more than 11%, polyunsaturates contributing no more than 6.5% and trans fatty acids no more than 2% of the daily food energy intake.

Trans fats

Trans fats are formed when the structure of monounsaturated and polyunsaturated fats are altered during a process called hydrogenation. They are often found in processed foods such as biscuits, cakes and margarines.

Trans fatty acids found in industrially produced products have been shown to have a negative effect on risk factors for CVD. In the UK efforts have been made to reduce or remove trans fatty acids from margarines and spreads through the use of new techniques and many now have minimal amounts of trans fatty acids.

Trans fatty acids also occur naturally in small amounts in milk and milk products and have been created in the stomach of ruminant animals (such as cows and sheep).

Vitamins, minerals and trace elements

Vitamins, minerals and trace elements are required for numerous functions within the body and deficiencies can lead to serious health problems.

They are required in much smaller amounts than fats, carbohydrates and proteins and are therefore known as micronutrients.

The department of health recommends specific amounts of each micronutrient for certain sub groups of the population known as dietary reference values (DRVs).

These recommendations only apply to healthy people and should only be used as a general guideline as individual requirements are likely to vary.

There are two types of vitamins, water-soluble and fat soluble.

Water-soluble vitamins

Water soluble vitamins travel around the body in the bloodstream and are picked up by cells when they are needed. Water-soluble vitamins that are not required by the body are excreted in the urine.

Fat soluble vitamins

Fat soluble vitamins are stored in body fat (for a few days or as long as 6 months) until the body needs them.

Water soluble vitamins:

Vitamin B1 (thiamin)

Vitamin B2 (riboflavin)

Vitamin B6

Vitamin B12

Folate

Niacin

Biotin

Pantothenic acid

Vitamin C

Fat soluble vitamins:

Vitamin A

Vitamin D

Vitamin E

Vitamin K

Minerals and trace elements

Minerals and trace elements are similar to vitamins and are required in very small or trace amounts to maintain good health.

Minerals tend to be required in milligram (mg) quantities and trace elements tend to be required in much smaller amounts - microgram (μg) quantities.

Some are found only in a few foods, so it is important that these foods are included in the diet on a regular basis e.g. the main providers of calcium in the diet are milk, cheese and yogurt . Some foods are also fortified with minerals, for example, iron is added to some breakfast cereals.

Minerals:

Calcium

Chloride

Fluoride

Iron

Magnesium

Phosphorus

Potassium

Sodium

Zinc

Trace elements:

Copper

Chromium

Iodine

Manganese

Molybdenum

Selenium