This document summarizes the key systems involved in the nutritional process: digestive, respiratory, circulatory, and excretory. It focuses on the digestive system, including the main parts of the gut and associated glands. The three phases of digestion - digestion, absorption, and expulsion - are described. The stages of digestion that occur in the mouth, stomach, and small intestine involve both physical and chemical breakdown of food. Absorption of nutrients occurs in the small intestine, while waste is expelled through the large intestine and other organs like the lungs and kidneys. Some common digestive illnesses are also briefly mentioned.

1. Unit 3 The Nutritional Process

2. Index
1. Introduction
2. Digestive system
3. Respiratory system
4. Circulatory system
5. Excretory system

3. 1. Introduction
There are 4 system involved in nutrition:
Digestive system:
- digestive tract
-associated glands
Respiratory system:
-respiratory paths
-lungs
Circulatory system:
-heart
-blood
-blood vessels
Excretory system:
-kidneys
-urinary tracts

4. Substances which enter the organism:
• air
• water
• foods
Products expelled by the organism (waste products)
Products expelled
Organ
Carbon dioxide
Lungs
Urea, water and salts
Kidneys
Faeces
Intestin

5. 2. Digestive system
2.1 Main parts
Gut
(digestive tube)
Glands
• mouth
•pharynx
• oesophagus
• stomach
• small intestine
• large intestine
• salivary glands
SALIVA (it contains amylase)
• liver
BILE (it does not contain any enzyme)
• pancreas
(It contains lipase, pancreatic amylase, protease)
PANCREATIC JUICE

6. 2.2 The digestive process
There are three phases in food processing:
-Digestion (mouth, stomach and small intestine) separation of substances (nutrients)
that can be used from the food
-Absorption (small intestine)
 nutrients pass into the
bloodstream
-Expulsion of waste (large intestine) unusable substances
are expelled

7. PERISTALTIC MOVEMENTS = Movement of food through the digestive tract. It consists
on the narrowing of the tube through the contraction of the muscles of the walls,
what pushes the food.

8. 2.3 Digestion
Mechanical digestion  cutting, crushing food
(physical changes)
A. Types of digestion
Chemical digesion  substances attack the food and
break it down into smaller chemical compounds (nutrients)

9. B. Stages of digestion
Physical digestion
Chemical digestion
 In the mouth  mastication and salivation take place
The salivary glands produce saliva, a liquid containing digestive enzymes (which act
chemically on the food)
Chemical digestion in the mouth  amylase breaks down the starch into maltose
DIGESTION
starch
DIGESTION
maltoses

10.  In the stomach begins gastric digestion
(both physical and chemical digestion take place
simultaneously)
Movement of the walls of the stomach
Food is mixed with the gastric juices,
which contain HCl and enzymes
As a result of gastric digestion, a pulp known as chyme leaves the stomach via the pylorus
http://www.youtube.com/watch?v=URHBBE3RKEs = gastric digestion

11.  First section of the small intestine
(duodenum)
Chemical digestion  the chyme is mixed with
intestinal juices.
They come from
• the walls of the duodenum
• the liver  produces bile
• the pancreas  produces pancreatic juice
The result is called chyle

12. 2.4 Absorption (in the jejunum and illeon)
The digested food (nutrients) passes into the
bloodstream through the intestine’s walls.
The walls of the intestine are filled with intestinal hairs (deep folds in the wall and many
blood vessels)  this increases the efficiency of absorption considerably.

13. 2.5 Large intestine
Leftovers and water arrive to the large
intestine.
• water and some ions pass into the bloodstream (absorption of
water and ions)
• Functions
• faeces are released through the anus
http://www.youtube.com/watch?v=IxNpXO8gGFM&feature=related = digestion and absorption
Page 65, activities 1 and 3

15. 2.6 Some illnesses
Cavities  destruction of teeth due to attacks from the bacteria which live in the mouth
Gastritis  inflammation of the walls of the stomach. It makes digestion difficult.
Gastroenteritis  caused by a virus or bacteria, producing vomits, fever or diarrhoea.