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Biology - Digestive System

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Digestive System

Breaks down food mechanically and chemically in order to release nutrient molecules that the body's cells can absorb and use. It removes solid waste from the body.

Parts of the digestive systems

Salivary glands

Parotid Glands

Submandibular Glands

Sublingual Glands


The back of the throat

The mouth

The mouth breaks down food mechanically with the teeth and tongue.

Breaks down food chemically with enzymes that are released into the mouth.


Consists of smooth muscle tissue and contracts and relaxes without conscious thought (called peristalsis)

The Stomach

The main functions are to hold food and churn it using smooth muscles

Stomach lining contains cells that produce digestive enzymes (pepsin) and acids (HCL).

The small intestine

Long and narrow

Consists of the duodenum, jejunum, ileum

Most of the digestion occurs

Large Intestine

The large intestines are smaller than a small intestine but are wider, they absorb water from food and the remain are excreted in feces.


The liver produces the bile and helps the breakdown of fats

Gall bladder

The gallbladder stores and concentrates the bile releasing it into the small intestine


Produces pancreatic fluids that breakdown fat, carbohydrates and proteins

Respiratory System

Organs of a respiratory system are responsible for the body's gas exchange, bringing oxygen in the body and getting rid of carbon dioxide.

The respiratory system and the circulatory system are connected and one cannot function properly without the other.

Parts of the respiratory system

Nasal Cavity

Filters, warms and moistens incoming air


The back of the throat


Prevents food from entering the trachea


Contains the vocal chords


Carries air to the bronchus


Carries air to the lungs


carries air to the alveoli


The Nose

Air passed by the epithelial cells that have microscopic, hair like projections called cilia

These cells create secrete mucus

The cilia and mucus help keep foreign parties such as dust and bacteria out of your body

The Lungs

Once through the nasal passage and pharynx the air moves into the trachea.

The air passes into branching tubes called the bronchus.

Each bronchus continues to branch sales tubes called bronchiole.

Gas Exchange

Air passes into smaller tubes until it ends up in tiny sacs called alveoli

Alveoli have thin walls and are surrounded by a network of capillaries

O2 and CO2 diffuse across the walls into and out of the bloodstream

The Circulatory System

The circulatory systems transports nutrients and oxygen to cells and to carry wastes to organs.

The Heart

The muscular organ between the lungs

Has four chambers, 2 upper thin-walled atrias and 2 lower thick- walled ventricles.

The septum is a wall dividing the right and left side

Passage of blood through the heart

Superior/ inferior vena cava→ right atrium→right ventricles→pulmonary arteries→lungs→pulmonary veins→left atrium→left ventricle→aorta→to the body.

Blood Vessels

Has 3 blood vessels: arteries, capillaries and veins.


Take blood away from the heart

Largest artery is the aorta

Have thick muscular walls

All carry oxygenated blood


Have walls only one cell thick to allow the exchange of gas and nutrients in the tissues and lungs.


Drain blood from the capillaries

Take blood from the heart

Have thin walls and valves that prevents backward flow of blood

All veins except for pulmonary veins carry deoxygenated blood

Parts of the circulatory system

Superior Vena Cava

Blood vessels bring deoxygenated blood from the upper body back to the heart.

Inferior Vena Cava

Blood vessels bring deoxygenated blood from the lower body back to the heart.




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