Life Processes Notes: Nutrition in Animals, Human Digestive System: Parts, Organs and Functions of Digestive system II How Paramecium and Amoeba obtain its Food II Free study material

How do organisms obtain their Nutrition?

Living Organisms obtain their nutrition using their specialized digestive system.

How Paramecium and Amoeba obtain its Food?

1. In Amoeba:

Amoeba is a single celled organism and has no definite body its body shape is not fixed.

Amoeba takes in food using temporary finger-like extensions of the cell surface called as Pseudopodia.

Pseudopodia fuse over the food particle forming a food-vacuole.

Inside the food vacuole, complex substances are broken down into simpler ones which then diffuse into the cytoplasm. 

The remaining undigested material is moved to the surface of the cell and thrown out.

2. In Paramecium:

In Paramecium, which is also a unicellular organism, the cell has a definite shape.

Paramecium is covered all over by Cillia.

Food is taken in at a specific spot. 

Food is moved to this spot by the movement of cilia which cover the entire surface of the cell.

Food vacuole is formed, and the food is then digested.

What is Digestive System ?

Digestive system is a Specialized tissue for digestion of outside material.

Single celled organisms do not have specialized tissue for digestion while Multicellular organism have a well-organized digestive system.

Human Beings have a well-maintained Digestive System.

Digestive System is a long tube extending from mouth to anus and have specialized regions marked for different functions. This long tube is also called as Alimentary canal.

MOUTH:

Food first enters mouth where teeth, tongue and saliva 

Teeth chew the food properly so that food attains same texture and smaller in size.

Mouth helps in mixing of food.

Salivary Glands located in mouth secretes a fluid called saliva that contains an enzyme Salivary amylase, which breaks down the Complex molecules of food to simpler ones.

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ESOPHAGUS:

Food from mouth now enters the Esophagus or Food pipe, here food move down by some rhythmic movement of esophagus called as Peristaltic movement.

FUNCTION: Pushing of food towards Stomach.

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STOMACH:

Food next enters the Stomach, it expands as the food enters and walls of stomach helps in mixing of food,

Stomach wall lining comprises of Gastric glands.

Gastric glands pour mainly three secretions into stomach: HCl, Pepsin and Mucus.

Mucus: Mucus covers the inside walls of Stomach and protects it from HCl (Acid)

HCl: Makes the food acidic so that any microbe- bacteria, virus or fungi which would be harmful get killed by acidic environment.

Pepsin: It is an enzyme that acts on Proteins and digest them.

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SMALL INTESTINE:

Next food enters the largest part of Alimentary canal called Small Intestine; it is longer tube but narrower in size. Food enters the Small Intestine from Stomach by Sphincter muscles.

The size of Small Intestine varies:

In Herbivores it is larger.

In Carnivores it is smaller in size.

FUNCTION: Digestion of Carbohydrates, Proteins and Fats.

Small Intestine receives secretion from Liver and Pancreas.

Liver secretes bile juices into Small Intestine that turns the acidic food alkaline

Bile breaks down the large fat globules to smaller globules so that fats get easy to digest.

Bile helps in emulsification of Fats.

Pancreas secretes pancreatic juice into Small Intestine that contains Trypsin and Lipase.

Trypsin act on proteins while Lipase act on breakdown of fats.

Small Intestine walls contain glands that secretes intestinal juices which converts Proteins to amino acids, Carbohydrates to Glucose and Fats to Fatty Acids and Glycerol.

Wall of Small Intestine also contains finger like projections called as Villi that increases the surface area for absorption and villi are richly supplied with blood vessels which take the absorbed food to each and every cell of the body.

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The unabsorbed food is sent into the large intestine where its wall absorb more water from this material. 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.