Immune , Circulatory and Digestive Systems – Grade 7 Science Worksheets
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The immune system protects the human body against diseases with the help of a group of cells, organs, and tissues.
- Our immune system gets stronger everyday right from our birth.
- Our body is exposed to several germs every day, and we are unharmed because of our immunity.
- Our immune system fights also has a record of the germs which have previously affected us this helps to restore and fight back when the same gets into our body.
What are the main organs in the immune system?
- 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.
Lymph nodes and lymphatic system
Lymph nodes help to carry WBCs wherever needed and destroys the bacteria and virus which enters our body.
White blood cells
The white blood cells are the fighter cells in our body. They originate in the bone marrow and developing from the stem cells.
The circulatory system is made up of our heart, blood vessels and blood. Our circulatory system transports oxygen and nutrients to every cell, tissue and organ in our body. It transports electrolytes, hormones, immunity cells throughout our body.
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.
- Red blood cells (RBC): These blood cells carry food, oxygen and other substances to various parts of the body. Also, removes the waste from the body.
- White blood cells (WBC):These cells are defense cells or work for the immune system. They fight against enemy particles entering the body which seem harmful.
- Platelets:Platelets help in clotting of blood when we have a wound/ cut.
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.
It is an organ located at the chest but slightly tilted towards the left. It works non-stop. Oxygenated blood and deoxygenated blood is mixed in the four chambers of the heart. Two atria and two ventricles form the four chambers of the heart.
The human circulatory system is a little more complex than that of other animals like fish, reptiles and the others.
In the human body, blood flows through the heart twice. Hence, circulation in human beings is called double circulation.
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 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.
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.
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.
The small intestine is actually the longest part our digestive system. It is made in such a way that it is highly coiled; it’s quite thin tubular form but still about 7.5 meters long. Nutrients get digested here. The enzymes in the intestine convert the carbohydrates into glucose, proteins to amino acids and fats into fatty acids and glycerol.
The liver releases bile. This neutralizes the acidity level of the food. The pancreatic juice digests the proteins and lipids. Once the food is broken down into the simple particles, it is ready to be absorbed by the body. The absorbed food is then carried to different parts of the body through the blood vessels for cell activities.
The large intestine is a thicker tube than the small intestine. The large intestine absorbs water and left over nutrients from the remaining food with the help of many bacteria in it. The remaining food waste passes into the rectum, where it is ready to get out as semi-solid wastes. Feces then are excreted by the body through the anus.
Fill in the blanks –
- The skin is an important organ of the ……………..…………… that keeps harmful substances out of the body and essential items within.
- The ……………… is the outer layer of the skin of the human body. It is specifically designed to prevent external germs from entering our body.
- ………………. is an organ of the size of a fist set at the chest but slightly tilted towards the left.
- ………………. help in clotting of blood at the time of wound/ cut.
- The ……………………… ……….. is the long tube through which the food that we eat is passed.
- Foodstarts its journey through the digestive system in the mouth, also known as the…………….. cavity
- The ……………… …………….. digests the proteins and lipids.
Fill In the blanks –
- Immune system
- Blood platelets
- Alimentary canal
- Buccal /oral
- Pancreatic juice