1. SBI 3U- The Human Digestive Systems and Disorders
Zachary Lamacraft

2. Overview/Agenda Curriculum expectations Introduction of human systems
Enzymes
Ingestion-activities
Stomach and Digestion- with a case study
Small intestine and pancreas- video and activity examples
Accessory organs
Absorption- activity examples
Homeostasis
Energy, Nutrients and Minerals

3. Curriculum Expectations
Specific Expectations
E1.1 evaluate the importance of various technologies, including Canadian contributions, to our understanding of internal body systems (e.g., endoscopes can be used to locate, diagnose, and surgically remove digestive system tumours; lasers can be used during surgery to destroy lung tumours; nuclear magnetic resonance [NMR] imaging can be used to diagnose injuries and cardiovascular disorders, such as aneurysms) [AI, C]
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 [PR, AI]
E3.2 explain the anatomy of the digestive system and the importance of digestion in providing nutrients needed for energy and growth (e.g., the body’s mechanical and chemical processes digest food, which provides the proteins needed to build muscle, and the fibre, water, vitamins, and minerals needed to regulate body processes)
E3.4 describe some disorders related to the respiratory, digestive, and circulatory systems (e.g., asthma, emphysema, ulcers, colitis, cardiac arrest, arteriosclerosis

4. Human Systems
Organs: groups of different tissues that specialize to carry out specific or particular functions.
Organ systems: a group of organs that have related functions
Important to note that several organ systems interact and depend on each other to function

5. Importance of Digestion/the Digestive System
Heterotrophs: organisms that must consume organic compounds to survive
Organic compounds (carbohydrates, fats, proteins, minerals and vitamins) are digested/ broken down in gastrointestinal tract and then absorbed and transported
Supplies body with energy and raw materials for synthesis of chemical compounds
After being absorbed they are transported via the circulatory system
Nutrients aid in GROWTH, MAINTENCE and REPAIR for tissues

6. Enzymes in Digestion
Recall enzymes are proteins that increase the rate at which biochemical reactions occur
The enzymes in the digestive system are hydrolytic : use water to breakdown various molecules
Two factors effect digestive enzymes: -Temperature -pH
Generally increase in temperature= increase enzyme activity
Enzymes work in specific pH ranges

7. Enzyme Activity Figure 1: Effect of temperature on human enzymes
Figure 2: Effect of pH on digestive enzymes blue= pepsin grey= amylase
Green- trypsin
Above are two graphs that show the effect of temperature and pH on human enzymes
Example: pepsin (acid- works in the stomach at a low pH) - amylase in the mouth (salivary glads)- works at a neutral pH
- Typsin (works in small intestine at a high pH- basic environment

8. Discussion Question
Question/Reflection for Student: “Why do most human enzymes have efficiency peaks at 37oC
What impacts do cold and heat have on our body functioning?
Why is it dangerous to have a fever? What may happen to our enzymes?

9. Recap: Physical vs. Chemical Digestion
Physical/Mechanical: is the act of breaking down food using teeth, beaks or other structures in many animals as well as contractions of the stomach
Chemical: enzymes and water to break down food so that it can eventually be absorbed by body cells
Physical also known as mechanical

10. 4 Main Processes of The Digestion System
1. Ingestion
2. Digestion
3. Absorption
4. Egestion/ or Elimination
Humans among other animals have a digestion which is considered an ALIMENTARY CANAL -Begins at the mouth and finishes at the anus (with separate openings for each)
-Food is broken down in one direction as it moves from end to end
Ingestion : the taking in of nutrients
Digestion: the breakdown of complex organic molecules into smaller components by enzymes
Absorption: the transport of digested nutrients to tissues of the body
- Egestion: removal of waste food materials from the body

11. Ingestion Saliva Fluid secreted by salivary glands
Contains amylase which breaks down complex to simpler carbohydrates
Lubricates food to be swallowed
Dissolves food particles
At this point food can be “tasted”
Breaks down starches into simpler sugars
There are taste buds on both your tongue and check. There are different receptors for specific flavours. They have a specific shape in which chemical compounds fill these receptor sites. If you dry off your tongue for instance and place a bit of salt or sugar on your tongue you will not taste anything until it dissolves (with aid from saliva) - there are tiny projections on your tongue which is where the majority buds are… they are called papillae

12. Activities:
Great part of the digestive system is that there are so many simple activities/demos that can be done while teaching this unit which will connect to the students to help them understand Cracker eating (few volunteers)—chew for a few minutes, observe change from bland to sweet as amylase breaks down complex starch molecules to simpler sugar forms
This is a tremendous activity that can be found in Biology 11 -basically you are measuring amylase’s effect on two different solutions - both are carbohydrate solutions and students will have a better understanding of how enzyme amylase works in digestive system
- I will post this on the website

13. Ingestion cont.
Teeth: -incisors: specific for cutting -canine: sharp for tearing -pre-molars: grinding -molars: crushing
Used for mechanical/physical digestion. They are necessary for making food into smaller particles

14. Ingestion cont. Esophagus
Peristalsis: rhythmic, wavelike contraction of smooth muscle that moves food through the esophagus
Food formed in a bolus after being broken down by saliva and teeth enters the esophagus
This occurs quickly, in the matter of seconds
Start video at 0:47 Another activity to help with this is allowing for students to have a pantyhose and table tennis/golfball. -Note it is contraction followed by relaxation

15. The Stomach and Digestion
Site of food storage and protein digestion
J-Shape organ that can store up to 1.5 L of food
Movement of food in and out of stomach is regulated by sphincters
Cardiac sphincter: regulates food from esophagus
Pyloric sphincter: regulates food from stomach to small intestine
A good way to describe what a sphincter to your students is like a drawstring
Grade 11 focuses more on the chemical digestion but you can see in the picture at the bottom 3 layers of smooth muscle running in different directions
- Because of this it allows the stomach to churn the food from contractions and relaxations

16. The Stomach and Digestion cont.
There are millions of cells that line the wall of the stomach that secrete many fluids which called collectively called gastric juice
Gastric juice : Hydrochloric acid (HCl) mucus, pepsinogens and other materials
Pepsinogens: enzymes that when exposed to a low pH such as conditions in the stomach, turns into its active form pepsin which is a enzyme the digests proteins
What do we know about HCl?
Good way to get your students thinking… HCl, we know is acidic, low pH, could burn through a carpet or even your hand if touched Acidic, low pH (1-3)
Kills many harmful substances that are ingested by food
Pepsinogens: enzymes that when exposed to a low pH such as conditions in the stomach, turns into its active form pepsin which is a enzyme the digests proteins
Both break down food into a thick liquid form called chyme and moved to the intestines

17. What stops HCl from burning a hole in your stomach?

18. Mucus
A protein produced by a layer of epithelial cells that provide a protective coating
It is alkaline in nature which is basic and protects lining of the stomach from both acid from HCl and pepsin from breaking down proteins of stomach lining
However when mucus is destroyed or not being produced…

19. Disorder: Stomach Ulcer
Ulcer: a lesion along the surface of an organ -when the mucus membrane is destroyed a peptic ulcer can be formed resulting in tissue being burned and an allergic reaction can become stronger resulting in blood vessels breaking down

20. Heliobacter pylori
- Useful tool to students would be showing them a picture of this bacteria Heliobacter pylori - introduce that along with stress, diet and other factors this bacteria is thought to be the main cause of peptic ulcers

21. Stomach Disorders: Ulcers cont.
Case Study
Have students in pairs or small groups uncover this bacteria Heliobacter pylori and other information about ulcers
Prevalence, demographics, how to detect this bacteria, bacterial weight/amount, effects on every day living/side effects, treatment etc. are all topics the students could discover
Could be in the form of a report, or a presentation, or even a jigsaw activity
Will post on website

22. Small Intestine Introduction Activities
Easy way to get the students thinking about the small intestine is having 7m of yard, tubing etc. and having it passed around the classroom
After this have them put it in a small box
Small intestine is not named small because of its length rather its diameter!

23. Small Intestine Cont. 3 parts of the small intestine are the:
Duodenum: - most digestion occurs here
Jejnum: has many folds that continue breakdown and absorption of remaining proteins and carbohydrates
Ileum: less absorption occurs here, unabsorbed particles are pushed through and continued

24. Digestion in the Small Intestine
How is the small intestine protected if HCl and pepsin- soaked food is sent to it from the stomach?

25. Small Intestine and Pancreas Interaction
Process:
HCl enters the duodenum from the stomach - HCl stimulates the coversion of prosecretin into secretin
When acids enter the small intestine an inactive chemical called prosecretin is converted to secretin - it is then absorbed into the bloodstream and carried to the pancreas, which released biocarbonate ions
Discussion
What do we know about bicarbonate ions?– basic, they can neutralize acids
-so basic that it raises the pH from about 2.5 to 9 which alternatively inactivates PEPSIN = therefore no digestion of proteins of the small intestine lining

26. Small Intestine and Pancreas Interaction
Bicarbonate ions are not the only molecules secreted by the pancreas The pancreas continues to secrete several enzymes to aid in digestion within the small intestine
First is trypsinogen which is inactive until it is converted from enterokinase (an enzyme within the small intestine) which activates it to trypsin which acts on partially digested proteins. - breaks these long chain polypeptides into shorter chains in which EREPSIN another enzyme foundin both pancreas and small intestine complete breaking down these polypeptides into amino acids
Also above is a chart of other various enzymes secreted by the pancreas and small intestine which aid in digestion

27. Liver and Gall Bladder: Role in Digestion
COAL- UH -SIS –TO- KINE- IN
CEAR ROSES Produces a fluid called bile which contains bile salts
They speed up fat digestion; which stomach is empty it is stored and concentrated in the gall bladder
Cholecystokinin (CCK) is released when fat is in the small intestine
CCK is carried to the gall bladder and it triggers the release of bile salts which break down fat into droplets
Gall-stones, jaundice and cirrhosis are a few disorders associated with these organs
This breakdown into droplets is physical digestion. It aids in chemical digestion as the breakdown of lipids into fat droplets results in an increase of surface area = increase of digestion from lipases
- STUDENTS CAN DO CASE STUDIES ON THOSE DISORDERS AND WHY IT MAY AFFECT DIGESTION

28. Absorption and Large Intestine
Colon is largest part of large intestine stores waste so that water as well as some inorganic salts, minerals and vitamins can be absorbed
There are several bacteria in the large intestine such as types of E.coli that can synthesize vitamins B and K
Cellulose is a carbohydrate that cannot be broken down by humans but provides bulk
Chemical digestion is finished at the large intestine
Some water, vitamins, medicines and alcohol can be absorbed in the stomach
which over time results in signals going to the CNS resulting in the removal of wastes (bowel movements)

29. Absorption: Villi, Microvilli and Lacteals
Villi: small finger-like projects that extend into the small intestine which increase surface area for absorption.
Microvilli: are a microscopic projection on cell membrane
Lacteals: are small vessels that transport fat to the circulatory system
Two ways to show this to students:
-one you could go to a butcher and bring in an intestine from an animal; it is easy to see the villi throughout the intestine
-or it can be compared to a shaggy carpet
- With a shaggy carpet a good demonstration could be to have a glass of water same amounts poor onto a carpet with no shag (takes up more room) and one with shag (wet on let parts) therefore more room for absorption

30. Homeostatic Control in Digestion
The last three workshops were on homeostasis so I will not go into much detail
Blood sugar: The last three workshops were on homeostasis so I will not go into much detail
Blood sugar The body ideally has an internal temperature of 37 C and blood pH of 7.35 HOWEVER it is rare that external environment cooperates with this
Air temperature fluctuates greatly, food pH is rarely 7.35 and various activities place demands on the body
Ex. Blood Sugar: - many reactions in the body help blood sugar levels stay level - eating causes the level to rise; which in turn chemical receptors cause the pancreas to release insulin. - insulin acts on the liver and muscle cells and allow them to become more glucose permeable resulting in glucose being converted to glycogen in the liver for storage - on the contrary when blood sugar levels are low glucagon is released which converts glycogen to glucose
Another example is gastrin : partial digested protein is in the stomach gastrin releases gastric juices to digest protein

31. Build a Body: SPONGELAB Biology
-Build a body - shows function and diagram - case studies investigates organs of the digestive system that are affected by a specific condition or disease

32. Food energy
In Canada energy is measured in joules (J) or kilojoules (kJ)
One calorie = 4.18 J One kcal = 4.18kJ
Basal metabolic rate: the minimum amount of energy that a resting person needs to maintain life processes

33. Daily Energy Requirements

34. Calculating Energy Requirements
There is a way to calculate energy requirements. The equation is
Energy required for 1 day= energy factor x body mass (kg) x time (24hr)
Energy required for an activity= energy factor x body mass (kg) x time (hr)
If you have athletes in the class that do activities in this chart this is a good idea to calculate what kind of energy is required for extended exercise use.
On a piece of paper, calculate your weight in kg, and assume you are comparing two different activities you do often for a 2h period
It is important for students to realize that different activities have different energy requirements and several things affect energy intake

35. Essential Nutrients
Vitamins: organic molecules needed in trace amounts for normal growth and metabolic processes
Minerals: elements required by the body. There are inorganic

36. Nutrients
Nutrients and minerals are important to learn about however can be kind of boring - can use techniques such as jigsaws to get students to learn the important information

37. Minerals