ppt the digestive system jmbf
TRANSCRIPT
THE DIGESTIVE
SYSTEM
Biology and Geology 3rd ESO – Unit 4 (I)
© I.E.S. “Luis de Góngora” .Córdoba. Spain
Dept. Biology and Geology
Juan Manuel Barroso Fernández
ORGAN SYSTEMS RELATED TO
THE PROCESS OF NUTRITION
DIGESTIVE
SYSTEM
RESPIRATORY
SYSTEM
CIRCULATORY
SYSTEM
EXCRETORY
SYSTEM
Remember:
Nutrition is the process through which
organisms obtain, use and transform
nutrients to keep on living.
urine
ORGAN SYSTEMS RELATED TO
THE PROCESS OF NUTRITION
Faeces
nutrients
Cellular activity DIGESTIVE
SYSTEM
RESPIRATORY
SYSTEM
CIRCULATORY
SYSTEM
EXCRETORY
SYSTEM
DIGESTIVE SYSTEM
FUNCTION:
To obtain nutrients from food
To absorb them into the circulatory system.
STRUCTURE:
A tube: the Gastrointestinal Tract
A set of glands secreting into the digestive
tract
Accessory Glands Alimentary canal or
gastrointestinal tract
Mouth
Pharynx
Oesophagus
Stomach
- Cecum
- Colon
- Rectum
Large
intestine
- Duodenum
- Jejunum
- Ileum
Small
intestine
Salivary glands
Gastric glands
Intestinal glands
Pancreras
Liver
Lips
Isthmus of the fauces
Upper oesophageal sphincter
Lower oesophageal sphincter
Pyloric sphincter
Ileocecal sphincter
Anus
Large intestine
Small intestine
Stomach
Oesophagus
Pharynx
Mouth
Intestinal glands
Pancreas
Liver
Salivary glands
Click on each arrow to
learn its name
- BLUE arrows: Accesory Glands
- GREEN arrows: Parts of the
Digestive Tract
Pharynx
Oesophagus
Stomach
Small intestine
Large intestine
Salivary glands
Liver
Pancreas
Intestinal glands
Mouth
Click on each arrow to show
further information
Egestion of non-digested substances (faeces) out of the body (defecation).
PROCESSES:
Absorption of the small
nutrients obtained through
digestion from food.
Chemical breaking down
(chemical digestion) using
enzymes, released by the
accessory glands.
Mechanical breaking down
of food.
Ingestion of food.
Deglutition.
Preparing the Digestive Process
1. INGESTION Food is taken into the digestive tract (mouth)
2. MECHANICAL BREAKING DOWN OF FOOD Mastication (chewing)
Food is broken down into small pieces thanks to the teeth and the tongue. Teeth are small, hard structures that can be classified as: Incisors (for cutting)
Canines (for tearing)
Premolars (for grinding)
Molars (for grinding)
Salivation Saliva has three functions:
It lubricates the bolus.
It kills some bacteria.
(It starts the chemical digestion of starch).
This way the bolus is formed.
Voluntarily, the tongue pushes the bolus into the pharynx and oesophagus.
Involuntary contractions of the oesophafus (peristalsis) drags the bolus along the tube until it reaches the stomach.
3. Deglutition
(swallowing)
4. CHEMICAL DIGESTION
The chemical breakdown of food takes place in:
Mouth: by saliva
Stomach (Gastric glands): by gastric juice
Liver: by bile* (* it only emulsifies fats, without any chemical effect)
Pancreas: by pancreatic juice
Intestinal glands: by intestinal juice
starch Digestive
enzymes
glucose
Stomach digestion
Gastric glands secrete gastric juice, which contains:
An enzyme: pepsin, which starts the breakdown of proteins.
Hydrochloric acid, devoted to three actions:
It activates pepsin.
It dissolves the food fibres.
It kills the bacteria that might still remain within the bolus.
When food enters into the stomach: - The stomach muscles start to contract.
- The bolus is mixed up with gastric juice for 1:30 h (carbohydrates)
3 h (proteins)
4 h (fats)
- Once the stomach digestion is finished, the mixture becomes a fluid paste called “chyme”.
Liver and Pancreas
Liver: It produces bile, which emulsifies fats.
Pancreas: It has a double function:
It acts as an inner gland, secreting insulin.
It acts as a digestive gland, secreting pancreatic juice, which contains enzymes to digest carbohydrates, fats and proteins. It also contains sodium bicarbonate to neutralise the acidity of chyme.
Chyme passes from the stomach to the duodene, where it is mixed up with three different substances secreted by:
Intestinal glands
They are microscopic glands located on the intestinal
mucouse, producing intestinal juice able to produce
enzymes to digest all the different types of biomolecules.
As a result, chyme becomes a white liquid: chyle.
Chyle contains simple molecules that are used as
nutrients by the body cells:
Monosaccharides, obtained from complex carbohydrates.
Glycerol and fatty acids, obtained from fats.
Amino acids, that have been obtained from proteins.
Intestinal
digestion CHYLE Gastric
digestion CHYME
The digestive process
Mechanical
breakdown BOLUS
MOUTH STOMACH SMALL INTESTINE
Teeth
Tonge
Saliva
Gastric juice Bile
Pancreatic juice
Intestinal juice
Chemical digestion:
SALIVA GASTRIC
JUICE
BILE PANCREATIC
JUICE
INTESTINAL JUICE
CARBO-
HYDRATES Starch →
Maltose
Starch →
Maltose
Disaccharides→
Monosaccharides
PROTEINS Proteins→
Polypetides
Polypeptides→
Peptides
Peptides→
Amino acids
FATS
(Bile
emulsifies
fats)
Fats →
Glycedrol, fatty
acids
Fats → Glycedrol,
fatty acids
Certain nutrients, such as water, mineral salts, alcohol and vitamins are direclty
absorbed without prior chemical digestion.
5. Absorption of nutrients
Once the digestive process is finished, nutrients pass from the intestine to the blood, which carries them through the circulatory system to the cells.
In the small intestine that substances, except water, are absorbed. The digestive mucose is folded forming wrinkles called villi. In turn, the cell membrane of the cells of the mucous membrane is folded forming microvilli. This way the absorption surface increases up to 400 m2. Glycerol and fatty acids are not directly delivered to the blood but to lacteals from which, in turn, pass them to the blood.
In the large intestine, water absorption takes place, giving way to the faeces, which are released out of the body through the anus. Faeces contain food remains, cells of the intestinal mucose and bacteria.
6. Egestion (defecation)
Main processes (click on each arrow to show the process)
Mouth Large int. Small int. Stomach Oesophaus Pharynx
Egestion
Absorption
Chemical breakdown
Deglutition
Mechanical breakdown
Ingestion 1
2
3
4
5
6
Web pages:
http://classes.midlandstech.com/carterp/Courses/bio211/chap23/chap23.htm
http://www.ahealthyme.com/Imagebank/digestive.swf
http://www.biographixmedia.com/stew/sbir/digestive.swf
http://hopkins-gi.nts.jhu.edu/images/shared/home/database/DigestiveSystem.swf
http://www.open2.net/everwonderedfood/interactives/digestive_system.swf
http://www.firstresponder.emszone.com/swf/CH04_Fig14.swf
http://www.giassoc.org/anatomy1.swf
http://www.upa.pdx.edu/IMS/currentprojects/TAH_Old%20Backup/Tester/MOD_3_DIGESTION.swf
http://mistupid.com/health/teeth.swf
http://www.tutorvista.com/content/biology/biology-iv/animal-nutrition/digestive-system-animation.php