Life Processes- Nutrition in Human Beings Flashcards
define alimentary canal
Alimentary canal in humans is a long tube of varying diameter.
It starts with the mouth and ends with the anus.
Oesophagus, stomach, small intestine and large intestine are the parts of the alimentary canal.
why should food particles be small and of same texture? how is this acheived?
We eat various types of food which has to pass through the same
digestive tract.Naturally the food has to be processed to generate
particles which are small and of the same texture. This is achieved by
crushing the food with our teeth. Since the lining of the canal is soft, the
food is also wetted to make its passage smooth.
what is saliva
saliva is a fluid secreted by our salivary glands
how are complex substances brokendownin the mouth
Another aspect of the food
we ingest is its complex nature. If it is to be absorbed from the alimentary
canal, it has to be broken into smaller molecules. This is done with the
help of biological catalysts called
enzymes. The saliva contains an
enzyme called salivary amylase that
breaks down starch which is a complex
molecule to give simple sugar. The food
is mixed thoroughly with saliva and
moved around the mouth while
chewing by the muscular tongue.
what is peristalsis and its significance
It is necessary to move the food in
a regulated manner along the digestive
tube so that it can be processed
properly in each part. The lining of
canal has muscles that contract
rhythmically in order to push the food
forward. These peristaltic movements
occur all along the gut. this phenomena is known as peristalsis
what is the stomach?
The stomach is a large
organ which expands when food
enters it. The muscular walls of the
stomach help in mixing the food
thoroughly with more digestive juices.
describe the digestion taking place in stomach
The digestion in stomach is taken
care of by the gastric glands present in the wall of the stomach. These
release hydrochloric acid, a protein digesting enzyme called pepsin,
and mucus. The hydrochloric acid creates an acidic medium which
facilitates the action of the enzyme pepsin. The hydrochloric acid also kills the bacteria and microbes that enter in along with our food. The mucus protects the inner lining of the
stomach from the action of the acid under normal conditions.
what is acidity as claimed by some
Acidity can be described as a condition wherein there is an excess of acid secreted by the gastric glands of stomach.
how does food exit the stomach
The exit of food from the stomach is regulated by the pyloric sphincter muscle
which releases it in small amounts into the small intestine.
why does small intestine legth vary
The length of the small intestine differs in various
animals depending on the food they eat. Herbivores eating grass need a
longer small intestine to allow the cellulose to be digested. Meat is easier
to digest, hence carnivores like tigers have a shorter small intestine.
The small intestine is the site of the complete digestion of
carbohydrates, proteins and fats, explain
The small intestine is the site of the complete digestion of
carbohydrates, proteins and fats. It receives the secretions of the liver
and pancreas for this purpose. The food coming from the stomach is
acidic and has to be made alkaline for the pancreatic enzymes to act.
Bile juice from the liver accomplishes this in addition to acting on fats.
Fats are present in the intestine in the form of large globules which makes
it difficult for enzymes to act on them. Bile salts break them down into
smaller globules increasing the efficiency of enzyme action. This is similar
to the emulsifying action of soaps on dirt that we have learnt about in
Chapter 4. The pancreas secretes pancreatic juice which contains
enzymes like trypsin for digesting proteins and lipase for breaking down
emulsified fats. The walls of the small intestine contain glands which
secrete intestinal juice. The enzymes present in it finally convert the
proteins to amino acids, complex carbohydrates into glucose and fats
into fatty acids and glycerol.
how is digested food taken up by the small intestine?
Digested food is taken up by the walls of the intestine. The inner
lining of the small intestine has numerous finger-like projections called
villi which increase the surface area for absorption. The villi are richly
supplied with blood vessels which take the absorbed food to each and
every cell of the body, where it is utilised for obtaining energy, building
up new tissues and the repair of old tissues.
what is the function of large intestine
The unabsorbed food is sent into the large intestine where its wall
absorb more water and electrolyte from this material.
how is undigsted and unwanted waste materal removed from body
The rest of the material is removed
from the body via the anus. The exit of this waste material is regulated
by the anal sphincter.
Why is nutrition a necessity for an organism
Nutrition is required for the following purposes:
(i) it is needed to provide energy for the various metabolic activities taking place in the body.
(ii) it is essential for the growth of new cells and replacement or repairing of worn-out cells.
(iii) it is required to develop resistance against various diseases.
