Digestion & Excretory System | Grade 6 | Unit 1 - Concept 2 - Lesson 4 | Science

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شرح ساينس سادسة ابتدائي - ترم أول

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In This Lesson:
Getting fuel (energy):
▌body systems need energy from food we eat to do their functions.
▌Food contains different nutrients such as carbohydrates, fats and proteins.
▌The human digestive system converts the complex food into simpler substances that the body can use for energy and growth in a process called "Digestion process".

Digestion process:
❶ Digestion begins when you put food in your mouth.
▌Jaw muscles move to help your teeth to chew the food.
▌Chewing breaks up the food into smaller parts .
▌ When you chew food, saliva (a liquid in your mouth that contains enzyme) can easily soften the food and begins the chemical breakdown of food.

❷ After you swallow the food, muscles push it down to your esophagus, then to stomach.
▌The continuous churning movement of the stomach and secreting the stomach's digestive fluids that contain an acid and some enzymes leads to more food breakdown.

❸ Enzymes secreted from pancreas and gallbladder help in the chemical breakdown of food once it moves into the small intestine.
▌Absorption of nutrients (digested food) starts in the small intestine.
▌The walls of the small intestine absorb these nutrients through blood vessels to carry them to all the body parts.
❹ The undigested food is passed to the large intestine.
▌Then, the large intestine absorbs most of water from the undigested food.
▌The last part of the large intestine is known as rectum that
stores the feces until it leaves the body.
▌The feces leaves the body through a muscular opening at
the end of the rectum known as anus.

Transporting nutrients:
▌Nutrients are transported to different organs through the circulatory system.
▌Some nutrients are used at once and others are stored as sugar and fats.

Example:
1. The liver and muscles can store glucose sugar and convert it into a special
storage substance called glycogen.
2. The liver and muscles convert glycogen into glucose sugar again and release it when your body needs energy.

 
The Excretory System




Excretion process:
▌It is one of the important vital processes inside the body, where the excretory system collects the waste materials produced by cells and removes them from the body.

What are the body parts responsible for excretion process?
1. Skin
When you sweat, waste leaves the body through pores in your skin.

2. Respiratory system
When you exhale, your body gets rid of another waste material which is carbon dioxide.

3. Urinary system
Its structure:
It consists of: • Two kidneys. • Ureters.
• Bladder. • Urethra.
Its function:
It removes waste materials from the blood in the form of urine.

 
Two kidneys:
They play a very important role in the urinary system as they continuously clean and filter the blood up to 300 times a day, where:

❶ A large artery brings blood to each kidney.

❷ One of the most important waste materials removed by the kidney is called urea which is formed due to the breakdown of proteins inside the body cells.

❸ After the filtering is completed urea, other waste materials and water become urine.
❹ Urine leaves each kidney through a narrow tube called ureter and collects in
the bladder
❺ Urine is removed from the bladder through another tube called the urethra.





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