Why do animals need nutrition ?

Nutrition is what we need for energy, for our growth and for maintenance of our body.   The animals need nutrition for getting energy , so that their organs may function smoothly, they can resist the diseases, they can grow and maintain their bodies.

But how do we get the nutrition? We get it by feeding on food. There are many types of living organisms in our Earth. Autotrophic and Heterotrophic. Here in this post we shall learn about only heterotrophic organisms or, rather all the living organisms on Earth else the plants. We are to study the nutrition in animals here .

 

The Human Digestive system

Nutrition-animals

It is a long journey made by the food that we eat. The Human digestive system is an interesting  system to learn about. What happens to the food we eat? How we get nutrition from the eaten food? What happens to the part of food (nutrition) that is absorbed? What happens to the part of food that is not absorbed by our body? How do our digestive system work? All these mysteries are going to be solved through this article. We will begin with the very beginning of the Human Digestive system from buccal cavity and end with Anus. So let us begin.

 

Buccal Cavity

Buccal cavity is the part of digestive system from where the food begins its journey inside our body. The process of intake of our food is termed as INGESTION. The Buccal cavity contains teeth and tongue in it. Both teeth and tongue play their role. The teeth helps cutting (Incisors), tearing (canines), and chewing(premolar and molar) the food. The salivary glands near buccal cavity releases saliva and tongue helps the crushed and chewed to get mixed with it well, so that it may enter into the esophagus (Food pipe ) in a paste form. 

Esophagus

Esophagus (Food Pipe ) is also a very important organ of the Human digestive system. The food pipe contracts and expands in such a way that the chewed food after getting mixed with saliva enters into it and then is sent to the stomach.

Stomach

The food reservoir of our body is Stomach. It is the most important organ of our digestive system. The food after passing through esophagus reaches stomach. Here the stomach keeps churning in such a way that the food starts digesting rapidly. The Bile juices extracted from the biggest gland of human body (LIVER)  helps oils and fats of the food to be digested easily. The PANCREAS make pancreatic juices called enzymes which break down sugar, fats and starches.The GALL BLADDER stores bile produced by LIVER. Stomach itself contains acids in it so that bacteria and other microorganisms that enter into the stomach via food may get killed by it.

It is noteworthy to write here that the stomach does not play a big role in absorption of food. It only absorbs water, alcohol and some drugs. During the 2 to 3 hours stay of food in Stomach it gets mixed and broke down and converted into simple thick , acidic , soupy mixture.

Small Intestine

Small intestine although named small is very long. In fact the small intestine is about 7.5 meter long coiled and intermingled organ of our digestive system. It is that part of the digestive system which contributes for the most amount of digestion. The inner walls of the small intestine contain small finger like outgrowths  called villi. These villi are having large surface area and they absorb all the nutrition from the digested food. The process is called ABSORPTION.

The absorbed nutrition are transported via blood vessels to different organs of the body, where they are used to build complex substances such as the proteins required by the body. The process is termed as ASSIMILATION. The food that remains undigested and absorbed enters into the large intestine.

Large Intestine

Large intestine is wider and shorter than small intestine.  It absorbs water, and some undigested salts from the undigested food material. The remaining waste passes into the rectum and remain there as semi liquid faeces.

Anus

The faeccal matter in the rectum gets ejected out through anus from time to time. This removal of undigested food in the form of faeces  is termed as EGESTION.

The Digestive System of Ruminants

What are Ruminants? Why cattle are called ruminants?These are some of the queries that must be addressed before understanding their digestive system.

What are Ruminants?

All those animals which are having a special type of bag like structure in or near their stomach called rumen are called as Ruminants. The ruminants are special animals which can feed on raw leaves and digest them. We the Human beings as well as any other carnivorous animal can never digest green grass, if we eat it. The green grass contains cellulose which is not digestible. But the Ruminants can digest it easily. It is because the rumen of ruminants are containing specific bacteria in it which help digest cellulose and convert it into simpler form.

The Insights about Digestive system of Ruminants.

The Ruminants have rumen in addition to all the organs of a normal digestive system. Whenever a ruminant ingests food, it stores in its rumen, so that it may take it out from there and keep it chewing till it gets digested . It is a process which goes on throughout the day. This long chewing of CUD (Pasted food) along with bacteria present in rumen enables the green grass eating animals to digest the cellulose easily.

The Microrganism like Amoeba and its Digestive System

Amoeba are unicellular Microorganisms. They do not have a digestive system as big as that of any animal.The Amoeba ingest food with the help of their fast feet called pseudopodia. The food ingested is sent to food vacuole where it gets digested.The absorbed food id used for growth, development and multiplication, and the undigested food get ejected out through egestion.

Keywords

  1. Absorption: The process through which the nutrients get absorbed in the body through villi inside the small intestine is called Absorption.
  2. Amino Acid: In the process of digestion, the protein of food item gets absorbed in the form of amino acids. Amino acids are essential for body growth and metabolism.
  3. Amoeba: Amoeba are unicellular living micro organisms having different digestion system.
  4. Assimilation: Assimilation is the process of transportation of digested food(nutrients) through blood into the cells, where it can be used.
  5. Bile: Bile is the digestive juice secreted by Liver for digestion of oils and fats.
  6. Buccal Cavity: It is the part of digestion system through which food gets ingested into the body. In Human beings it comprises of mouth, Tongue and teeth.
  7. Canine: The types of teeth used for tearing the food are canines.
  8. Cellulose: A type of carbohydrate present in green leafy vegetables.
  9. Digestion: The process through which food undergoes and gets digested is called digestion.
  10. Egestion:  Egestion is the process through which the undigested food gets ejected out through body.
  11. Fatty Acid: The acids present in stomach which helps in digestion of food and also kills the harmful bacteria in stomach.
  12. Food vacuole: An important organ of micro organisms where the food of those organisms gets trapped and then digested.
  13. Gall bladder: An small sac like organ located near the liver which stores the bile secreted out by liver.
  14. Glycerol: In the process of digestion, the fats are absorbed by the body in the form of glycerol.
  15. Incisor: Incisor are the types of teeth which are used for cutting the food item.
  16. Ingestion: Ingestion is the process of intake of food by body.
  17. Liver: Liver is the biggest gland of body which secretes out Bile juice helpful for digesting the oils and fats.
  18. Milk Teeth: The type of teeth that grow during infancy of a child and fall off by the age of eight are called milk teeth.
  19. Molar: The types of teeth which are stronger and help us for chewing and grinding the food are molar.
  20. Permanent Teeth: Those set of teeth which replace the milk teeth are called permanent teeth.
  21. Esophagus: The food pipe which connects the buccal cavity with stomach is called esophagus.
  22. Pancreas: Pancreas is the large gland which secrets out pancreatic juices that help in digestion of carbohydrates fats and proteins.
  23. Premolar: Premolar teeth are those teeth which are smaller than molar but help in grinding and chewing the food.
  24. Pseudopodia: Pseudopodia are the body part of amoeba which are finger like projections use to capture the food item and ingest it.
  25. Rumen: Rumen is a sac like body part of ruminants attached with the stomach. It has bacteria in it which help digestion of cellulose.
  26. Ruminant: Ruminant are those animals which have rumen in their digestive system.
  27. Rumination: The process of ruminants by which they are able to convert green grass into cud by chewing it again and again and sending it to rumen and bringing back for chewing. This helps in digestion of food much easily.
  28. Salivary Glands: Salivary Glands are those glands which produce saliva, helpful for mixing food in the buccal cavity.
  29. Villi: The small finger like projections inside the inner wall of small intestine. They help in absorption of nutrients.
  30. Saliva: Saliva is the fluid secreted and produced by salivary glands in the mouth.

Exercise Questions and Solutions

1. Fill in the Blanks:

a) The main steps of nutrition in humans are Ingestion, digestion, absorption, assimilation and egestion.

b) The largest gland in the human body is liver.

c) The stomach releases hydrochloric acid and digestive juices which act on food.

d) The inner wall of the small intestine has many finger like outgrowths called villi.

e) Amoeba digests its food in the food vacuole.

Mark T for true and F for false statements.

a) Digestion of starch starts in the stomach. (F)

b) The tongue helps in mixing food with saliva. (T)

c) The gall bladder temporarily stores bile. (T)

d) The ruminants bring back swallowed grass into their mouth and chew it for some time. (T)

Tick mark the correct answer in each of the following:

a) Fat is completely digested in 

small intestine.

b) Water from the undigested food is absorbed mainly in the

Large intestine.

Match the columns

Column 1

Column 2

Food Components

Products of Digestion

Carbohydrates

Sugar

Proteins

Amino acids

Fats

Fatty acids and Glycerol

5. What are villi? What is their Location and function?

Answer-

Villi- Villi are small finger like projections inside the inner walls of small intestine.

Location- Inner walls of Small Intestine.

Function- The villi absorb the digested food material through their large surface area.

 

6. Where is the Bile produced? Which component of the food does it help to digest?

Answer-

Bile is produced in the largest gland of the body called Liver.

The bile juice helps in digestion of oil and fats.

7. Name the type of carbohydrate that can be digested by ruminants but not by humans. Give the reason also.

Answer-

The type of carbohydrate that can be digested by ruminants but not by humans is cellulose. It is present in raw green leafy plants.

Cellulose isn’t easy to digest. The ruminants by continuously chewing make it cud and then send it to Rumen where some bacteria present in it helps in digestion of cellulose.

8. Why do we get instant energy from glucose?

Answer -We get instant energy from Glucose because glucose gets easily absorbed in blood providing instant energy.

9. Which part of digestive canal is involved in:

(a) Absorption of food – Small intestine

(b) Chewing of food – Buccal cavity

(c) Killing of bacteria – Stomach

(d) Complete digestion of food – Large intestine

(e)Formation of faeces  – Large intestine

10. Write one similarity and one difference between the nutrition in amoeba and human beings.

Answer-

Similarity: In Human beings as well as amoeba, the digestive juices help the food to get broken into simpler substances.

Difference:  Food Vacuole in amoeba is enough for the digestion of food, while in case of Human beings, it is a complex process involving many organs.

11. Match the following:

Column 1

Column 2

a)      Salivary Gland

(iii) Saliva secretion

b)      Stomach

(iv) Acid release.

c)      Liver

(i)Bile juice secretion

d)      Rectum

(ii) Storage of undigested food.

e)      Small Intestine

(v) Digestion is completed

f)       Large Intestine

(ii) Storage of undigested food.

(vi) Absorption of Water

12. List all the main organs of Human Digestive system

Answer-

  1. Buccal Cavity
  2. Esophagus
  3. Stomach
  4. Liver
  5. Gall Bladder
  6.  Small Intestine
  7. Large Intestine
  8. Rectum
  9. Anus
13. Can we survive only on raw , leafy vegetables/grass? Discuss.

Answer-

No we cannot survive only on raw leafy vegetables or grass. Our digestive system is not able to digest the cellulose present in raw grass or green leaves. We have to prepare them well in order to digest. The ruminant can only digest cellulose present in green leafy vegetables or grass, because they have rumen. Rumen are sac like structure attached with stomach of ruminants which contain bacteria that breaks down cellulose into simpler forms and hence digest it.

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