The Human Digestive SystemWhat do you already know?

• Complete the Digestive System Handout to the best of your ability without looking in any text or your notes.

• You may work in groups.

• Do not complete the bottom overview.

The Human Digestive System

Video Overview

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

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

Why do we need a Digestive System?

Components of the Digestive System?• 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

Oral Cavity (mouth)

Small Intestine

Esophagus

Components of the Digestive System?• 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 enzymes2. Moves materials along the tube

Digestive Enzymes• Digestive Enzymes help to break

food into smaller pieces so that it is easier to digest

Digestive Enzymes Video

The Mouth• Digestion begins in the oral cavity

(mouth) where 2 types of digestion take place:

1) Mechanical Digestion2) Chemical Digestion

Mechanical Digestion• Chewing breaks up large

pieces of food into smaller ones

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

Chemical Digestion• Saliva also contains mucus and

water which makes food easier to swallow.

Chewing Crackers Activity – Part 1

Put a regular cracker into your mouth and chew

What did it taste like?• Sweet? Plain? Record your

observations

Chewing Crackers Part 2 – 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 1.5 minutes before chowing down?

• When the cracker is in your mouth your saliva starts to break it down get’s softer

Chewing Crackers Discussion

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

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

Grab a ruler and have a look

Esophagus

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).

Esophagus

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.

Esophagus

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

Demo

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 4 L of food!!

Stomach

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 - Video

Stomach

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

Stomach

Bread in bag experiment:1) Take 1 piece of bread per two students. Rip in half so

each student has ½ of a slice2) Obtain a small sandwich bag from the front of the room3) Tear your ½ slice of bread into smaller pieces and place

it into your sandwich bag (What does this represent?)

4) Your teacher will come around now and pour a small amount of juice into the bag

5) Close your bag and squish the bread with your fingers until all of the pieces are really small (What does this represent?)

6) Put all of the contents of the bag into the garbage (What does this represent?)

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

Small Intestine

Receives many digestive enzymes from the pancreas and liver to help break down food

• Moves food using smooth muscle cell contraction

• The lining of the intestine secretes protective mucus to protect it from the enzymes

• Is about 7 m (22 feet 6 inches) long, 2.5 cm (1 inch) in diameter and has a surface area of 250 square meters (2,700 square feet) – the size of a tennis court!

Small Intestine

• Sometimes called the Colon.

Its function is to absorb water and vitamins from the remaining food.• Also stores the remains of

the food that cannot be absorbed (wastes) before they are flushed from the body.

• About 1.5 m (5 feet) long and 6.5 cm (2.5 inches) in diameter

Called the large intestine because it has a much larger diameter than the small intestine

Large Intestine

The rectum acts as a temporary storage facility for feces before it is excreted from the body.

Uranus

Rectum

• 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

Accessory Organs

- Produces bile which is stored in the gall bladder.

- Bile is then sent to the small intestine to break down fats.

Gall Bladder

Liver

1) Is involved in supplying enzymes required for digestion directly into the small intestine.

2) 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.

If insulin is not used effectively, diabetes can result.

Insulin Video

Pancreas

Review and Revisit

• Name that Digestive System Organ

1) Liver2) Esophagus3) Stomach4) Pancreas5) Small Intestine6) Large Intestine7) Rectum

1 2 3

7

5

6

4

The Human Digestive System Handout RevisitedWhat do you already know?

• Complete the Digestive System Handout to the best of your ability without looking in any text or your notes.

• Complete the bottom section using information from this Power Point

Excellent Digestive System Interactive Activities – Please Click to Visit