By Carly Hart
Curriculum Expectations
E2.1 use appropriate terminology related to animal anatomy
E2.2 perform a laboratory or computer-simulated dissection of a representative animal, or use a mounted anatomical model, to analyse the relationships between the respiratory, circulatory, and digestive systems
E3.2 explain the anatomy of the digestive system and the importance of digestion in providing nutrients needed for energy and growth
E3.3 describe the anatomy and physiology of the digestive system (including the mouth, epiglottis, esophagus, stomach, intestines, liver, and pancreas), the mechanisms of peristalsis, absorption, and mechanical and chemical digestion, and the function of the kidneys
E3.4 describe some disorders related to the respiratory, digestive, and circulatory systems describe how organelles and other cell components carry out various cell processes (e.g., digestion, transportation, gas exchange, excretion) and explain how these processes are related to the function of organs
Learning Goals
Students will be able to:
1) Explain the purpose of the digestive system.
2) Describe the parts of the digestive system.3) Identify parts of the digestive system on a diagram.
4) Construct a model of the parts of the digestive system to show chemical and mechanical digestion.
5) Make observations and perform experiments on the process of digestion.
6) Explain how food moves through the digestive system.
7) Discuss various disorders related to the digestive system
E2.2 perform a laboratory or computer-simulated dissection of a representative animal, or use a mounted anatomical model, to analyse the relationships between the respiratory, circulatory, and digestive systems
E3.2 explain the anatomy of the digestive system and the importance of digestion in providing nutrients needed for energy and growth
E3.3 describe the anatomy and physiology of the digestive system (including the mouth, epiglottis, esophagus, stomach, intestines, liver, and pancreas), the mechanisms of peristalsis, absorption, and mechanical and chemical digestion, and the function of the kidneys
E3.4 describe some disorders related to the respiratory, digestive, and circulatory systems describe how organelles and other cell components carry out various cell processes (e.g., digestion, transportation, gas exchange, excretion) and explain how these processes are related to the function of organs
Learning Goals
Students will be able to:
1) Explain the purpose of the digestive system.
2) Describe the parts of the digestive system.3) Identify parts of the digestive system on a diagram.
4) Construct a model of the parts of the digestive system to show chemical and mechanical digestion.
5) Make observations and perform experiments on the process of digestion.
6) Explain how food moves through the digestive system.
7) Discuss various disorders related to the digestive system
Content
DIGESTIVE SYSTEM
Reasons for Digestion:
Animals cannot use food ingested directly because:
1) the food macromolecules are too large to pass through membranes and enter the cells of the animal
- molecules must be broken down small enough to be absorbed by diffusion, facilitated diffusion and/or active transport
- must be broken down and reassembled in a form that is needed by the animal
Food Processing
Purpose of digestive system:
Digestion = process of breaking food down into small molecules for absorption
Types of digestion: mechanical digestion & chemical digestion
Hook/Activity:
Mechanical Digestion Demonstration (6)
Take a piece of chalk and break it in half. Break one of the halves up into
smaller pieces. Have students predict which half of the chalk will dissolve more quickly in a jar of vinegar. Place the pieces of chalk into the vinegar and observe during class time. Relate the dissolution and the size of chalk particles to the need for mechanical digestion.
Have students try the experiment in groups, with each group using a different concentration of vinegar. Have the students record the time it takes the chalk to dissolve.
Mechanical digestion:
Teeth Types:
Incisors: flat, blade-like teeth for biting
Canines: fang-like teeth at front corners of the mouth for shred and tear
Premolars & molars: bigger, round teeth inside mouth for grind and crush
Chemical Digestion
Absorption = process of absorption of molecules in small intestine
Elimination = process of undigested material passing out of the digestive compartment (rectum & anus)
Activity:
Mix it Up and Squeeze: students will make a model of the digestive system that demonstrates mechanical and chemical digestion. (3)
Digestion Process
Video: Quick Overview of the Digestion Pathway
1) Tongue is stimulated by taste and tactile sensations
2) Parts of the nervous system respond to activate salivary glands to secrete saliva
3) Tongue, teeth, and jaw muscles help to dismantle food
4) Food becomes bolus, ball like moistened mass
5) Tongue lifts the bolus to the roof of mouth and pushes it into the pharynx
Peristalsis = a series of coordinated muscular contractions that moves bolus of food
6) Bolus passes through the pharynx and glides over the epiglottis
Epiglottis = trap door that prevents food from entering the trachea (windpipe)
7) Bolus drops into the esophagus
esophagus = thin muscular tube that connects pharynx to stomach
8) Bolus then encounters the lower esophageal sphincter
lower esophageal sphincter = a ring of smooth muscle found at the connection to the stomach
9) The lower esophageal sphincter constrict to prevent reflux of food back to the esophagus
10) The lower esophageal sphincter then relaxes to allow food to enter the stomach
11) Bolus then enters the stomach
stomach = J-shaped stretchable organ that can hold approximately 1.5 L of food
12) The stomach’s muscular walls churn and squeeze the food using the thick layers of smooth muscles and rugae
Rugae = Folds in the stomach muscles
13) Gastric juices are added from cells of the gastric glands to the mechanical digestion in the stomach
14) Food bolus is partially digested and becomes a liquefied paste called chyme
15) Stomach muscular contractions propel the chime through the pyloric sphincter
pyloric sphincter = ring of smooth muscles
16) Chyme enters into the duodenum section of the small intestine
Small intestine: the major site of digestion and absorption
17) Chyme is digested to nutrients in the simplest form in the duodenum
18) Nutrients are absorbed through the walls of the jejunum and ileum
19) Unabsorbed materials of the chyme approaches the ileocaecal valve
ileocaecal valve regulates the entrance into the large intestine
20) Chyme enters the caecum part of the large intestine
Large intestine:
21) Chyme moves slowly through the colon
22) Left over solid waste, called feces, pass through the rectum
23) Feces exit the body through the anus (Defecation)
Activity:
What Am I? (6)
Review the function of the digestive organs. Have students create a table including the digestive system structure and explaining its function. Write all the parts of the human digestive system on self-stick
notes. Stick a self-stick note on the back of each student. Have them ask eac other yes/no questions to figure out the structure posted on their back.
Video: Digestive Disorders (explains various digestive disorders, and how to prevent/improve these conditions)
Video: Digestion Review (review for unit test)
Additional Content Resources
Process of Digestion: The notes above are adapted from this site. This content on this site can be used to explain the process of digestion, and all of the paths involved. Key words are in bold to help students identify key terms. (5)
Digestive Organs/Enzymes (1)
Digestive Tour: This is a PowerPoint presentation that shows the steps of digestion, the 2 types of digestion, structures of digestive organs, and many diagrams. (4)
List of Digestive System Diseases and Disorders
Purpose of digestive system:
- change the foods into chemicals that the body can use
- properly eliminate things that the body cannot use
Digestion = process of breaking food down into small molecules for absorption
- convert food molecules into smaller, simpler units to be absorbed by cells
- carbohydrates broken down to monosaccharides (ie: glucose, fructose,
- proteins broken down to amino acids
- fats broken down to fatty acids and glycerol
Types of digestion: mechanical digestion & chemical digestion
Hook/Activity:
Mechanical Digestion Demonstration (6)
Take a piece of chalk and break it in half. Break one of the halves up into
smaller pieces. Have students predict which half of the chalk will dissolve more quickly in a jar of vinegar. Place the pieces of chalk into the vinegar and observe during class time. Relate the dissolution and the size of chalk particles to the need for mechanical digestion.
Have students try the experiment in groups, with each group using a different concentration of vinegar. Have the students record the time it takes the chalk to dissolve.
Mechanical digestion:
- occurs mainly via teeth and stomach
- solid food masses are shredded, torn, ground, and shaken
- different mammals have different types of teeth
Teeth Types:
Incisors: flat, blade-like teeth for biting
Canines: fang-like teeth at front corners of the mouth for shred and tear
Premolars & molars: bigger, round teeth inside mouth for grind and crush
- Carnivores have enlarged canine teeth – used to shred meat
- Herbivores have incisors for snipping leaves and flat pre-molars and molars for grinding tough fibrous plant into a fine pulp
- Omnivores have all types of teeth
Chemical Digestion
- Mixing of food with various juices from digestive glands and reaction with enzymes to break down further
Absorption = process of absorption of molecules in small intestine
- molecules are considered absorbed when they pass through the wall of the small intestine (via finger like projections from the wall of the small intestine called villi)
- water and some vitamins are absorbed in large intestine
Elimination = process of undigested material passing out of the digestive compartment (rectum & anus)
Activity:
Mix it Up and Squeeze: students will make a model of the digestive system that demonstrates mechanical and chemical digestion. (3)
Digestion Process
Video: Quick Overview of the Digestion Pathway
1) Tongue is stimulated by taste and tactile sensations
2) Parts of the nervous system respond to activate salivary glands to secrete saliva
3) Tongue, teeth, and jaw muscles help to dismantle food
4) Food becomes bolus, ball like moistened mass
5) Tongue lifts the bolus to the roof of mouth and pushes it into the pharynx
- pushing to the pharynx = “Swallowing”
Peristalsis = a series of coordinated muscular contractions that moves bolus of food
6) Bolus passes through the pharynx and glides over the epiglottis
Epiglottis = trap door that prevents food from entering the trachea (windpipe)
7) Bolus drops into the esophagus
esophagus = thin muscular tube that connects pharynx to stomach
8) Bolus then encounters the lower esophageal sphincter
lower esophageal sphincter = a ring of smooth muscle found at the connection to the stomach
9) The lower esophageal sphincter constrict to prevent reflux of food back to the esophagus
10) The lower esophageal sphincter then relaxes to allow food to enter the stomach
11) Bolus then enters the stomach
stomach = J-shaped stretchable organ that can hold approximately 1.5 L of food
12) The stomach’s muscular walls churn and squeeze the food using the thick layers of smooth muscles and rugae
Rugae = Folds in the stomach muscles
13) Gastric juices are added from cells of the gastric glands to the mechanical digestion in the stomach
14) Food bolus is partially digested and becomes a liquefied paste called chyme
15) Stomach muscular contractions propel the chime through the pyloric sphincter
pyloric sphincter = ring of smooth muscles
16) Chyme enters into the duodenum section of the small intestine
Small intestine: the major site of digestion and absorption
- consists of three sections: duodenum, jejunum, ileum
17) Chyme is digested to nutrients in the simplest form in the duodenum
18) Nutrients are absorbed through the walls of the jejunum and ileum
- Approximately 80% of all absorption occurs in the small intestine
- Remaining of absorption occurs in stomach and large intestine
19) Unabsorbed materials of the chyme approaches the ileocaecal valve
ileocaecal valve regulates the entrance into the large intestine
20) Chyme enters the caecum part of the large intestine
Large intestine:
- main functions: reabsorb water and to hold and compact the unabsorbed material from the small intestine
- consists of consecutive sections - caecum, colon, rectum, and anus
21) Chyme moves slowly through the colon
- colon is divided into: ascending, transverse, descending, and sigmoid colon
- absorbs water, salts, and some vitamins into the body
- accumulates waste products of digestion and prepare for
22) Left over solid waste, called feces, pass through the rectum
23) Feces exit the body through the anus (Defecation)
Activity:
What Am I? (6)
Review the function of the digestive organs. Have students create a table including the digestive system structure and explaining its function. Write all the parts of the human digestive system on self-stick
notes. Stick a self-stick note on the back of each student. Have them ask eac other yes/no questions to figure out the structure posted on their back.
Video: Digestive Disorders (explains various digestive disorders, and how to prevent/improve these conditions)
Video: Digestion Review (review for unit test)
Additional Content Resources
Process of Digestion: The notes above are adapted from this site. This content on this site can be used to explain the process of digestion, and all of the paths involved. Key words are in bold to help students identify key terms. (5)
Digestive Organs/Enzymes (1)
Digestive Tour: This is a PowerPoint presentation that shows the steps of digestion, the 2 types of digestion, structures of digestive organs, and many diagrams. (4)
List of Digestive System Diseases and Disorders