When you eat foods -such as bread, meat, and vegetables - they are not in a form that the body can use as nourishment.

Food and drink consumed must be broken down into smaller molecules so that they can be absorbed into the body

The Digestive Tract is a series of hollow organs joined in a long, twisted tube from the mouth to the anus.

Organs involved: Mouth Esophagus Stomach Liver

Pancreas Small Intestine

Large Intestine Rectum

E

Oral Cavity (mouth)

Small Intestine

Esophagus

Digestive enzymes help to break the food into smaller pieces so that it is easier to digest

Enzymes Video

Digestion Video Bill Nye

The entire length of the digestive tract is lined with epithelial tissue.

Contains lots of goblet cells which secrete mucus. The mucus does two things

1.Protects tract from digestive enzymes

2. Moves materials along the tube

Digestion begins in the oral cavity (mouth) where 2 types of digestion take place:

&

Mechanical Digestion: Chewing breaks up large pieces of food into smaller ones

FOOD

Chemical Digestion: The Human Body releases 1 – 1.5L of saliva per day from glands in your cheeks (salivary glands)

Saliva converts Carbohydrates into simple sugars like Glucose.

Glucose

Saliva also contains mucus and water which makes food easier to swallow.

Chewing Crackers Part 2 – Copy down a new chart and record your observations

What it feels like initially in your mouth

- Is it sweet/bland?

What is feels like after 1 min. in your mouth- Is it sweet/bland?

What it feels like after 1.5 min. in your mouth

What it feels like when you chew it

Place a cracker in your mouth and let it sit for 1.5 min. before chewing

What was the main texture (feeling) difference in your mouth between chewing right away and waiting before?

When the cracker is in your mouth your saliva is starting to break it down Get’s softer

Food enters the esophagus which is a narrow, muscular tube about 25 cm long.

Food is swallowed by voluntary action (you control) of the tongue.

Ruler

The Trachea (Wind Pipe) and Esophagus are connected: – Why does food not go into lungs?

There is a small flap consisting of connective tissue

which prevents food from entering the trachea when swallowing (Epiglottis).

Trachea

The wall of the esophagus is made up of two layers of smooth muscles which push the food down into the stomach

If a person were to swallow while being upside down you could see the muscles in action.

1)Place your hand over your throat then swallow- What do you feel?

2)Turn to someone next to you. • Have your partner tilt their

head up• Watch their neck as they

swallow – reverse roles

The stomach acts as a storage place for food as well as a place of digestion.

It is also described as an elastic “bag” made of muscle which expands.

- It can hold up to 4L

Chemical Digestion :-Stomach cells produce acid (HCl) which helps break down proteins

-The stomach cells also secrete mucus to protect its lining from the acid.

- Sometimes this acid exits the stomach and enter the esophagus

Can lead to heart burn

Mechanical Digestion: The muscles of the stomach wall contract and expand to churn food and move it towards the small intestine

The growling sound you sometimes here is your stomach moving.

This is smooth muscle

The small intestine further splits food into smaller pieces. Most of the nutrients we take in are absorbed in the small intestine.

Small Intestine VideoBlood

Recieves many digestive enzymes from pancreas and liver

• Move food through using smooth muscle cell contraction

• The lining of the intestine secretes protective mucus

Sometimes called the Colon

Its function is to absorb water and some vitamins from the remaining food

, as well as store the useless nutrients and wastes before they are flushed from the body.

It has a much larger diameter, that’s why it is called the large intestine

The rectum acts as a temporary storage facility for feces

before it is excreted from the body.

The Liver, Pancreas, and Gall Bladder all help with the digestion by supplying digestive enzymes

The Liver also produces bile which helps digest fats

These substances are delivered into the small intestine

- It produces bile which is stored in the gall bladder. Bile is then sent to the small intestine to break down fats.

Gall Bladder

• The pancreas is involved in supplying enzymes required for digestion directly into the small intestine.

• It also secretes a hormone called insulin directly into the blood stream.

Insulin causes most of the body's cells to take up circulating glucose (cell food) from the blood.

Insulin Video