Immune, Circulatory and Digestive Systems

What are the main organs in the immune system?

The skin

• The epidermis is the name of the outer layer of the skin of the human body. It helps to prevent germs from entering our body from the outside.

• Our skin is like a cover or a wrap to keep germs from getting into your body.

Blood

Plasma, blood cells are the main components of the human blood.

Plasma is the fluid part of blood. 90% of plasma is water.

Blood cells are the blood which is solid in nature. There are three types of blood cells.

Blood Vessels

Blood vessels are the carriers in which blood travels to all body parts. There are two types:

Arteries

These blood vessels carry oxygen containing blood.

Arteries are thick and elastic and carry blood away from the heart.

Veins

These carry carbon dioxide rich blood. Veins are thin and elastic which bring blood to the heart.

The Digestive System

The alimentary canal is the long tube through which the food that we eat is passed.
The digestive system starts at the mouth or the oral cavity going through the pharynx, esophagus or food pipe,stomach, small intestines, large intestines, rectum and anus. The food particles get digested in every stage as they move.

Oral /Mouth and the Buccal Cavity

The mouth has many accessory organs such as the tongue, teeth, and salivary glands, which help in the digestion of food. Food starts the first step of digestion in the mouth, also known as the buccal cavity or the oral cavity. Grinding of the food is done by the teeth.

Salivary amylase

Salivary amylase is the digestive juices secreted by the salivary glands. This helps to moisten the food, and break the food down into usable and absorbable components and then the food is pushed down into the pharynx.

Pharynx

The pharynx acts as a passage for the chewed food from the mouth to the esophagus.

Esophagus or Food Pipe

It is made of flexible muscle to help pushing of food easily. It carries swallowed food down its long tube and pushes it to the stomach.

Stomach

The stomach is like a thick muscular bag that is located on the left side of the abdominal cavity. Stomach slowly digests the food which it gets from the food pipe and sends it to the small intestine. The stomach has acids which help reduce food into further absorbable substances. Mucous protects the inner walls of the stomach. This can otherwise get damaged while digesting food. Because the acid reacts with the bacteria and kills it that enters our body with food. The digestive enzymes break down proteins into simpler substances.

Check Point

Fill in the blanks –

1. The skin is an important organ of the ……………..…………… that keeps harmful substances out of the body and essential items within.
2. The ……………… is the outer layer of the skin of the human body. It is specifically designed to prevent external germs from entering our body.
3. ………………. is an organ of the size of a fist set at the chest but slightly tilted towards the left.
4. ………………. help in clotting of blood at the time of wound/ cut.
5. The ……………………… ……….. is the long tube through which the food that we eat is passed.
6. Foodstarts its journey through the digestive system in the mouth, also known as the…………….. cavity
7. The ……………… …………….. digests the proteins and lipids.

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