“Some people eat to live, others live to eat…”

In both ways, nutrition is important. But before we look at the food, we need to study the

structures…

Do you know?The lining of the small

intestine is about 300m2 ~ the size of a tennis court

Do you know?It takes about 12 to 24 hours for materials to travel along

the length of the large intestine

Do you know?More than one litre of saliva is secreted each day

Chapter 6: Nutrition in Humans

Topical Learning Objectives

Identify the main regions of the alimentary canal and the associated organs

Describe the main functions of these parts

Describe peristalsis

Topical Learning Objectives

Explain why most food must be digested

Describe absorption as the passage of soluble products of digestion through the wall of the small intestine and into the blood capillaries

State the role of liver in digestion.

The following activity is purely fictional. No organs will be harmed in any way.

Have you always want to do a job that just requires you to eat?

Do you want a dream job requires you to taste yummy food?

Look no further !!!

Calling out to ALL mouth and stomach!

The DIGESTIVE SYSTEM® is currently hiring!!!

Please send in your resume right now to get this dream job

WE WANT YOU!

Writing a resume for the “digestion job”

Activity

Each of you will either choose to be the ‘mouth’ or the ‘stomach’ and write a resume for it to apply for the digestion job.

What should I include?

• In your resume, you may include:1. Name (Mr Lim’s Stomach)2. A picture of yourself (label/state the physical

parts)3. Education Background (What kind of food do

you specialise in?)4. Work experience (What can you do? What

enzyme can you offer?)

Holozoic Nutrition

What is Holozoic Nutrition ?• Holozoic nutrition is the intake of food and the processes

that convert food substances into living matter.

• Comprises of four stages : Ingestion / Feeding

Digestion

Absorption

Assimilation

Mouth

• Mouth

• Stomach

• Small Intestine

• Small Intestine

• Large Intestine

All parts of the body

IngestionThe intake of food into our body via the

mouth

DigestionThe process whereby large food molecules are

broken down into soluble and diffusible molecules that can be absorbed into the body cells

LET’S RECALL!

Why must food be digested?

• Food we ingest is made up of large molecules that cannot pass through the walls of the intestine and into the blood vessels.

• Food must be digested to break down the large molecules into simple molecules that can pass through the walls of the intestine and into the blood vessels.

• Blood can then transport the simple food molecules to other parts of the body to be used for various processes.

Two types

of Digestion

1. Mechanical Digestion

2. Chemical Digestion

DigestionDigestion

Mechanical Digestion

ChemicalDigestion

Physical process of chewing, mashing and breaking up food into

smaller particles

Process of hydrolysing food into smaller

particles via enzyme action.

Mouth

Stomach

Mouth

Stomach

Small Intestine

The Mouth and the Buccal cavity

The mouth leads into the buccal cavity which

consists of:

• Teeth

• Salivary glands

• Tongue

The Mouth and the Buccal Cavity:: Structure

The Mouth and the Buccal Cavity: Functions

• Both mechanical and chemical digestion

• Teeth mechanical digestion

Chewing action of teeth breaks large to small food particles

Increases surface

area for enzyme action

The Mouth and the Buccal Cavity: Functions

• Tongue

• Mixing of food with saliva

• Rolls food particles into boli

The Mouth and the Buccal Cavity: Functions

• Salivary glands chemical digestion

Secrete saliva through salivary duct

• Mucin: dilutes and moistens the food

• Salivary amylase aid in digestion

Saliva

Begins at the Mouth…

Saliva

Contain amylase

maltose

TeethSalivary Glands

Break into smaller pieces

The Pharynx (for your information) During swallowing, food is

prevented from entering the trachea by the epiglottis

The epiglottis is a flap like cartilage just above the larynx (voice box)

When food gets into the trachea, the person will cough to force the food out

What happens if you eat and talk

at the same time?

Choking

Think and Ponder!

The Oesophagus : Structure

• Narrow, muscular tube • Continues from the pharynx to the stomach• The wall consists of two layers of muscles

Circular MusclesLongitudinal Muscles

The Oesophagus : Functions

• The oesophagus transports food from the pharynx to the stomach via:

Gravity Peristalsis

• Peristalsis is the rhythmic, wave-like contractions of the gut wall

Peristalsis Peristalsis is the rhythmic, wave-like contractions of the gut wall

How does peristalsis occur?

• When circular muscle contracts,

• longitudinal muscle relaxes

Wall constricts

The Oesophagus : Functions

The Oesophagus : Functions

• When circular muscle relaxes,

• longitudinal muscles contracts

Wall dilates

• Moves the food along the gut

Do you know?We can eat even when we are ‘upside down’!!

Summary

What is the holozoic nutrition?

What are the structures and functions of the mouth?

Explain briefly, the mechanism of peristalsis in the oesophagus

MUDDIEST POINT?