“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 300m 2 ~ 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

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 Stomach Small Intestine Large Intestine All parts of the body

Ingestion The intake of food into our body via the mouth

Digestion The 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

Digestion Mechanical Digestion Chemical Digestion 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 Teeth Salivary 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 Muscles Longitudinal 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

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?