Category Human Body

When is the appendix used in digestion?

The appendix is a narrow tube-like piece of gut resembling a tail, which is located at the end of the large intestine. The tip of the tube is closed; the other end joins on to the large intestine. It is only found in humans, certain species of apes and in the wombat. Other animals have an organ in the same position as the appendix that acts as an additional stomach, where the fibrous part of plants and cellulose is digested by bacteria. It seems that a we evolved through the ages and began to eat less cellulose in favour of meat, a special organ was no longer needed for its digestion.

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The only time we are aware of the appendix is when it becomes infected and this is known as appendicitis. For the most part it is a useless part of the large intestine with no known function.

 

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When does food reach our intestines?

Everything you eat has to be chopped up and broken down before the nutrients or goodness in it can be taken into your blood and used by your body cells to make energy. This takes place in your digestive system or gut. The food leaves your stomach a little at a time and goes into your small intestine. This is where most of the digestion takes place by adding digestive chemicals and absorbing the digested chemicals and absorbing the digested nutrients into the body. The lining of the intestine is folded into millions of tiny fingers called villi. Undigested food continues its journey on to the large intestine where excess water and minerals are extracted from the leftover food.

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How much energy do we use?

Sitting or lying: 43-72 cals per hour

Walking: 144-216 cals per hour

Running: 432-575 cals per hour

 

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When do we produce saliva?

The major function of saliva is to help in the process of digestion. It keeps the mouth moist and comfortable when we eat and helps to moisten dry food, allowing it to be chewed and swallowed more easily. The mucus in saliva coats the bolus (or chewed food) and acts as a lubricant to help us to swallow.

The enzyme ptyalin which is found in saliva begins the first stage of digestion. It begins to break down starchy food into simpler sugars. Saliva also allows us to taste our food and drink. Each day we all usually produce about 1.7 litres (3 pints) of saliva.

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The four main tastes are sweet, salt, bitter and sour, and you can taste them with different parts of your tongue. You can check where the four tastes are by dabbing it with a little salt, sugar, coffee grounds (bitter) and lemon juice (sour).

 

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When do we learn to talk?

As air flows out of the lungs, we can use it to make the sounds of speech and other noises. At the top of the windpipe, in the sides of the voice box or larynx, are two stiff, shelf-like folds – called the vocal cords. Criss-crossed muscles in the voice box can pull them together so that air passes through a narrow slit between them and makes them vibrate, creating sounds. As the vocal cords are pulled tighter, they make higher-pitched sounds. As the vocal cords loosen, they make lower-pitched sounds. Of course, when we actually learn to talk, our speech depends on the development of the brain and its ability to copy the sounds that we hear.

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Although many people think of speech as our main way of communicating, we do not have to use spoken words. People who can’t speak learn a language called signing, in which hands and fingers are used to signal letters and words.

 

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When do red and white blood cells die?

Both white and red blood cells are formed in the bone marrow. Each red blood cell measures about 7.5 microns (thousandths of a milimetre) in diameter and is shaped a little like a doughnut. Red blood cells contain haemoglobin, which gives them their red pigment. There are 5 to 6 million red cells per cubic mm of blood. The red cell only survives about 120 days and the damaged and old cells are removed by the spleen and liver.

A white blood cell is not really white but almost transparent. It can change shape, push out folds and finger-like projections and crawling like an amoeba in a pond. These cells survive less than a week.

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An average adult body has about 5 litres of blood. At any one time, about 1,250 ml are in the arteries, 3,500 ml in the veins and about 250 ml in the capillaries. The cells in blood flow through a capillary for only half a second before they move into the next type of vessels, small veins.

 

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When are our blood groups determined?

Our individual blood group is determined by our parents at the time of our conception. Blood groups are determined by the presence of antigens (a substance capable of stimulating an immune response) on the surfaces of the red cells. Although the red blood cells in different people look the same they are, in fact, dissimilar. They can be divided up into four main groups: A, B, AB and O.

Blood can be transplanted from one person to another by what we call a blood transfusion. It is very important that the blood given matches the person’s group, because if the wrong types of blood are mixed together the result can be serious blood clots.

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Blood begins to clot as soon as it is exposed to the air, plugging the wound. White blood cells gather around the wound to kill invading microbes, and new skin cells grow into the healing wound beneath the scab.

 

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