The Digestive System

Functions:

1. Takes food into the body

2. Breaks down food

3. Absorbs digested materials

Two types of Digestion:

Mechanical digestion: food is physically broken down into smaller pieces.

Chemical digestion: chemicals in the body break down the food molecules into smaller molecules.

Enzymes help these chemical reactions happen. Even your saliva contains enzymes and begins the process of chemical digestion in the mouth.

enzyme at work

mouth esophagus stomach small intestines large intestines rectum anus

Food’s path:

Epiglottis: the flap of tissue that covers the windpipe when you swallow

Esophagus: connects the mouth with the stomach.

Peristalsis: food goes down the esophagus pushed by the wave motion of involuntary muscles.

Most mechanical digestion occurs in the stomach.

Small intestine: most chemical digestion takes place here and most of the absorption of nutrients too.

Liver: this organ secrets bile into the small intestines which helps digest fats.

Pancreas: organ that produces enzymes that help break down nutrients in the small intestines.

Villi: structures in the small intestine that absorb the small nutrient molecules to be used by the body to make energy.

Large intestine: here material that is not absorbed passes to the large intestine then to the rectum and finally eliminated through the anus.

Large intestine

The Respiratory System

This system moves oxygen from the outside environment in to the body and removes carbon dioxide from the body

Air moves through the nose or mouth to the pharynx or throat.

From the larynx, air passes through the trachea into two large passageways called the bronchi

Air moves from the pharynx into the trachea, or windpipe

At the top of the trachea is the larynx, which contains the vocal cords.

At the very end of the bronchi you have tiny structures called alveoli. Here blood passes and the gas exchanges take place.

Mouth/nose

Pharynx

Trachea

Bronchi

Alveoli

To blood

Passage of oxygen to blood

throat

windpipe

There is one for each lung

O2 and CO2

Gas exchange to blood vessel

Diaphragm: muscle that allows you to inhale and exhale.

When you inhale the diaphragm move “down”

When you exhale it moves “up”

                                           

The Excretory System

This system collects waste products from your cells and removes this waste from the body. This process is called excretion.

Kidneys: two organs that filter your blood and remove wastes such as urea and excess water. The 2 million filters in the kidneys are called nephrons.

The waste and water are then sent to the 2 tubes called the ureters to your bladder. When you need to pee, the urine travels to the urethra and then out of your body.

Now your blood has been cleaned!

The Circulatory System

This system links all parts of your body through its network of blood vessels.

The system carries needed substances to cells and carries waste products away from cells.

Each time your heart beats it pushes blood through the blood vessels.

When the heart muscle relaxes, it fills with blood, when it contracts, it pushes blood forward.

Blood that has no O2

but a lot of CO2 enters the heart in the right atrium. Then it follows this path:

right atrium

right ventricle

lungs

left atrium

left ventricle

Your body heart pumping

Arteries:   Blood vessels that carries blood away from the heart

Veins:       Carry blood back towards the heart.

Capillaries:   Tiny blood vessels that carry blood to the cells of your body. Capillaries also join the arteries to the veins.

You have different cells in your blood that have different functions:

Red blood cells: carry O2 to all your other cells and CO2 away from them.

White blood cells: these cells fight harmful bacteria and viruses.

Platelets: form clots to injured tissues. (scabs)

The lymphatic System

This system collects all the fluids that leak out of the bloodstream and puts it slowly back in the blood. In this system you also have “lymph nodes” that can help catch harmful bacteria. Your tonsils are lymph nodes.

The lymphatic system has no “pump” so liquids move slowly and mainly by diffusion. The lymph vessels have smooth muscle that help move the fluid along as well.