MODERN SCHOOL, DUNGARPUR SUBJECT:-SCIENCE CLASS- … 5 class 7 science.pdfmaterial. RECTUM Undigested waste from large intestine passes into rectum and is stored here as semi-solid

MODERN SCHOOL, DUNGARPUR

SUBJECT:-SCIENCE

CLASS- VII

LESSON- 2 NUTRITION IN ANIMALS

TOPIC- NUTRITION IN ANIMALS (Part B)

DAY- 5 Assignment

MOUTH

Mouth contains tongue, teeth and salivary glands.

Digestion begins in mouth.

Teeth help in breaking bigger food particles into smaller

pieces by the process of chewing or mastication.

Chewing or Mastication:- It is a mechanical process of

breaking the bigger food particles into smaller pieces.

Tongue helps in mixing saliva with the food.

Saliva:- The watery substance present in the mouth,

secreted by the three pairs of salivary glands.

The juices present in saliva help in the chemical digestion

of starch into sugars.

After the breakdown of food into smaller pieces, and

mixed with saliva, it is swallowed down into the digestive

system and enters the food pipe or oesophagus.

Fig-1 Salivary glands in humans

TEETH

Teeth are located in our jaws(upper and lower) in the

mouth cavity, fixed to the gums.

Based on the structure and function, teeth are of four

types:- incisors, canines, premolars and molars.

Fig-2 Different types of teeth in humans and their arrangements.

DEFINITION

The arrangement of teeth in the jaws.

MILK TEETH

The first set of 20 temporary teeth in a baby .

Fig-3 Type, number, and functions of teeth in humans

Temporary milk teeth and permanent teeth

At birth, a human infant has no teeth. The first teeth appear

after 6 months or so and fall off between 6 to 8 years of age.

These are called milk teeth and they are temporary. There are

20 milk teeth. Milk teeth are replaced by permanent teeth at

around the age of 6.Permanent teeth are 32 in number.

Tongue

Fleshy-muscular organ, attached at the back and

free at the front.

Movable in all directions.

Functions:- It helps in

mixing the chewed food with saliva.

swallowing the food.

to detect different tastes of food, with the

help of taste buds.

Fig-4 Location of taste buds on the tongue.

OESOPHAGUS (Food pipe)

Food pipe or oesophagus is a passage or pipe from

the mouth to the stomach through which swallowed

food passes.

It runs along the neck and the chest.

Food is pushed down by the peristaltic movements

of the wall of the food pipe. No digestion takes place

here.

Fig-5 Movement of food in oesophagus

STOMACH

Thick-walled flattened bag present in the upper

abdomen.

Widest part of alimentary canal

Functions- It receives food from the food pipe.

Inner lining of the stomach secretes mucus,

hydrochloric acid and digestive juices.

Mucus- protects the inner lining of the stomach.

Acid – kills bacteria enter along with food and makes

the medium acidic, so the digestive juices can act.

Digestive juices- helps to breakdown the proteins

into simpler substances.

Partially digested food from the stomach goes into

the small intestine.

SMALL INTESTINE

Highly coiled, about 7.5 m long tube.

Digestion fully completes here and absorption of

food also.

Absorbed food is passed into the blood system,

through which nutrients reach all parts of the body.

Digestion in small intestine is carried out with the

help of a) secretions from the liver and pancreas b)

digestive juices secreted by the small intestine.

Liver-

Largest gland in the body. Reddish-brown gland,

located in the upper part of abdomen on the right side.

Secretes bile juice(helps in the digestion of fats) , stored in a

sac called the gall bladder.

Pancreas-

Cream-coloured and located just below the stomach.

Pancreatic juice acts on proteins, starch, fats and

breaks them to simpler forms. Carbohydrates-

converted into glucose.

Fats- converted into fatty acids and glycerols.

Proteins- converted into amino acids.

Fig-6 Location of associated glands-liver and pancreas

Absorption in small intestine-

The inner wall of small intestine contain small

finger-like projections called villi, they increase the

surface area for absorption of the digested food.

Villi contains blood vessels.

Assimilation in small intestine-

Food substances are absorbed by the villi and then

transported through the blood vessels to different

organs of the body.

The undigested and unabsorbed food enters the

large intestine.

LARGE INTESTINE

Shorter in length(1.5m) , wider than the small intestine

No digestion occurs here.

Function- To absorb water from the undigested food

material.

RECTUM

Undigested waste from large intestine passes into

rectum and is stored here as semi-solid faeces.

ANUS

The faecal matter is passed out through an opening

called anus. This process is called egestion.

ACTIVITIES

1. Draw the different types of teeth and

label them?

2. Which part of the alimentary canal is

involved in-

a) Ingestion of food?

b) Chewing of food?

c) Pushing down of food?

d) Killing of bacteria?

e) Complete absorption of food?

f) Absorption of digested food?

g) Absorption of water?

h) Storage of undigested waste food?

3) What are the two roles performed by the

small intestine in humans?

4) What are villi? What is their location and

function?

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