Human Digestive System

Objectives1) Describe the structure of the inner wall of the small

intestine and explain it’s role in terms of increased surface area for absorption of nutrients.

2) Explain the role of a lacteal and blood capillaries in the transport and absorption of nutrients.

3) Describe the functions of the colon, rectum and anus in relation to absorption of water and mineral salts, temporary storage and egestion of faeces.

Small IntestineWhat happens to the digested food?

Digested food products, mineral salts and water are

absorbed throughout the small

intestine especially in the ileum.

Video Time! As you watch the video clip, observe the inner walls of the small intestine .

Inner wall of small intestine

Folds

Villi – minute finger like projections

Inner wall of small intestine

Fold

Villi – minute finger like projections

Microvilli

Inner wall of small intestineWhy is there a need for numerous folds, villi

and microvilli?

To increase surface area for absorption of digested food substances – Increasing the absorption rate of

water and digested food products

Bloodcapillaries

Lacteal

Sugars, amino acids, are absorbed by diffusion into the blood capillaries

Blood capillaries transport sugars and amino acids away from the small intestine.

Glycerol and fatty acids diffuse into the epithelium – form fat globules – enter the lacteals

Lacteal transport fats away from the small intestine.

Epithelium

Villi

One cell thick

Faster diffusion of the digested food products

What is the epithelium one cell

thick?

Would the absorption of nutrients be affected if digested food substances cannot be transported away by the blood capillaries?

Explain your answer.

Yes. To a certain extent

The continual transport of digested food substances maintains a concentration gradient for the absorption of digested food substances by diffusion

Lower concentration of digested food substances in the lumen of the small intestine, glucose and amino acids are absorbed by active transport

Mineral salts enter the blood capillaries by active transport

Activity time!I need a doctor!

I need a doctor!You are a doctor that specializes on

the ileum. As the doctor of a

patient who is overweight and has

the intentions to lose weight, what

procedures can be done to help the

patient lose weight? Explain your

answer.

Work in pairs/trios.

You have 3 minutes

Large intestineColon

• Absorb water and mineral salts from undigested food materials

Rectum • Temporarily stores the faeces

• When the rectum contracts, faeces is expelled through the anus

Anus – Egestion/defaecation of faeces

Let’s Review1) Describe the structure of the inner wall of the small

intestine and explain it’s role in terms of increased surface area for absorption of nutrients.

2) Explain the role of a lacteal and blood capillaries in the transport and absorption of nutrients.

3) Describe the functions of the colon, rectum and anus in relation to absorption of water and mineral salts, temporary storage and egestion of faeces.

Write 3 key things that you learn today

What am I still unsure about?