1. Digestive, Respiratory, and Circulatory Systems Working Together
Nutrient Absorption
Digestive, Respiratory, and Circulatory Systems
Working Together

2. Nutrition  The Vital Nutrients
- Six basic kinds of nutrients can be found:
1. Carbohydrates
Main source of energy
2. Fats
Used to store energy
3. Proteins
Form part of muscles and many cell structures, including the cell membrane

3. Serve as structural materials 5. Vitamins Ca
4. Minerals
Serve as structural materials
5. Vitamins
Needed for growth and metabolism
6. Water
Facilitates chemical reactions, helps dissolve materials and helps maintain the body’s temperature Cr Mg
Vitamin D
Vitamin C
B12

4. Following the Digestion of a Meal
Functions of the Digestive System
Main function is to disassemble the food you eat into its component molecules so that it can be used as energy (ATP) by your body.

5. All of these organs work together to break down food into simpler compounds that can be absorbed by the body.

6. Four Stages of Digestion
Ingestion- the act or process of taking food or other substances into the body.
Digestion- the process of converting food to an absorbable form by breaking it down to simpler compounds.
Absorption- the process of moving water and solutes from outside of the cell into the interior.
Elimination-the process of the body ridding itself of any indigestible material.

7. Digestion/Absorption Summary
Digestion begins as soon as you start eating. Enzymes in your saliva start the process of converting food into energy.
Via mechanical and chemical mechanisms, large nutrient molecules are broken down into smaller ones that your intestine absorbs into the blood stream.
Cells then take up these nutrient molecules and use them to build new molecules and provide their cellular energy needs.
Cells can also store the molecules for later use.

8.  The Mouth - The disassembly line STARTS at the mouth
What happens when you chew?
Your tongue moves food around & helps position it between your teeth
Chewing is a form mechanical digestion = the physical process of breaking down food into smaller pieces. This prepares food for chemical digestion
Chemical digestion = the process of changing food on a molecular level through the action of enzymes

9. Chemical Digestion begins in Mouth
Saliva in mouth contains digestive enzymes, called amylase, which breaks down starch into smaller molecules
In the stomach, amylase continues to digest food for about 30 min.

10. Starch

11. Swallowing Your Food Chewed food becomes a ball and is swallowed
Swallowing forces food into throat and then to the esophagus = a muscular tube that connects the mouth to the stomach
Food moves through the esophagus by peristalsis = a series of involuntary smooth muscle contraction along the walls of the digestive tract

12. Peristalsis

14. The epiglottis = a flap of cartilage that closes over the opening to the respiratory tract as you swallow, keeping food out
After food passes, epiglottis opens again
If you talk or laugh as you swallow, food may enter the upper portion of the respiratory tract
Your response is to choke & cough, forcing food out of the respiratory tract

16.  The Stomach
Stomach = a muscular pouchlike enlargement of the digestive tract
Muscle Churning
The walls of the stomach are composed of 3 layers of involuntary muscles
When the muscles contract, they work to physically breakdown food, creating smaller pieces
The pieces mix with digestive juices produced by the stomach

17. Chemical Digestion in the stomach
The lining of the stomach contains millions of glands that secrete a mixture of chemicals called gastric juice
Gastric juice contains pepsin & hydrochloric aced
Pepsin = an enzyme that begins the chemical digestion of proteins in food

18. The lining of the stomach secretes mucus that forms a protective layer b/t it and the acidic environment of the stomach
Food remains in stomach for about 2-4 hrs
When food leaves it is the consistency of tomato soup (YUMMY!)

19.  The Small Intestine
- Small intestine = a muscular tube about 6 m long
Called “small” because of how narrow it is (only 2.5 cm in diameter)
- Digestion is COMPLETED here
- First 25 cm of the small intestine called the duodenum

21. Secretions of the Pancreas
Pancreas = soft, flattened gland that secretes both digestive enzymes & hormones
The mixture of enzymes it releases break down carbs, proteins, & fats

22. Secretions of the Liver
Liver = large, complex organ that produces bile
Bile = chemical substance that helps break down fats
Made by the liver, but stored in the gallbladder
From the gallbladder, bile passes into duodenum
Bile causes further digestion by breaking large drops of fat into smaller droplets
Gallstones form when bile in the gallbladder becomes too concentrated due to high levels of cholesterol in you diet

23. LIVER

24. Absorption of Food
Liquid food stays in the intestine for 3-5 hrs. as it is moved through
As food moves it passes over thousands of tiny fingerlike structures called villus = a single projection on the lining of small intestine that function in the absorption of food
Now that food is in the form of small molecules, it can be absorbed directly into the cells of the villi (plural for villus)
Food then diffuses into blood vessels of the villus & enter the bloodstream
* Villi are the link between the digestive system & the circulatory system

26.  The Large Intestine
- All indigestible material from a meal then moves into the large intestine = a muscular tube that is also called the colon
- Large intestine is only about 1.5 m long, but it is much wider that the small intestine ( about 6.5cm in diameter)

27. Water Absorption
As indigestible mixture passes through the large intestine, water and salts are absorbed by the intestinal walls, leaving behind a more solid material
This way water in NOT wasted

28. Bacteria in the large intestine make some B vitamins and Vitamin K, which are absorbed as needed by the body
These bacteria also stop harmful bacteria from colonizing, reducing the risk of intestinal infections

29. Elimination of Wastes
After hrs in the large intestine, the remaining indigestible material, now called feces, reaches the rectum
Rectum = the last part of the digestive system

30. Respiratory/Circulatory Systems Functions
Your respiratory system takes in oxygen from the atmosphere and moves that oxygen into the blood stream by allowing it to move across the membranes of the lungs into the blood vessels.
The circulatory system then carries oxygen to all the cells in the body and picks up carbon dioxide waste, which it returns to the lungs.
Carbon dioxide diffuses from the blood into the lungs , and you exhale it into the atmosphere.

31. Digestive Dependence Upon Respiration
The digestive tract functions by using muscular contractions to break up food and move it along the tract.
These muscles depend upon oxygen in order to function.
Without oxygen, your digestive tract would stop working.

32. Respiratory Dependence Upon Digestion
Your respiratory tract wouldn’t be able to function without the products of digestion.
The process of exhalation is passive; does not require muscular contraction.
Contraction of the diaphragm and intercostal muscles requires fuel.
This fuel is primarily in the form of carbohydrates or lipids.

33. Blood And Energy
Your body relies primarily on carbohydrates and fats from the foods you eat for energy.
The blood transports these chemicals to the cells of your body through the circulatory system.

34. Cellular Dependence Upon All Three Systems
The body cells depend upon products of both the respiratory and digestive systems’ functions in order to maintain themselves
To produce energy, cells burn nutrient molecule fuel in oxygen.
Digestive tract provides nutrient molecules, while the respiratory tract provides oxygen.
Circulatory system transports both products to the cell.

35. Neural and Hormonal Regulation of Digestion
Gastrointestinal activities are coordinated by the nervous system and endocrine system.
Stomach secretions are regulated by food and gastrin.
The passage of chyme into the duodenum inhibits stomach contractions.
Duodenum secretes other hormones that inhibit stomach emptying and promote bile release and bicarbonate secretion.
enterogastrones

36. Hormonal Control of Gastrointestinal Tract

37. Accessory Organs Liver regulatory functions
Liver chemically modifies substances absorbed in the gastrointestinal tract before they reach the rest of the body.
also removes toxins and poisons, and converts them into less toxic forms
Liver regulates many compounds such as steroid hormones, and produces most proteins found in blood plasma.

38. Regulation of Blood Glucose Concentration
After a carbohydrate-rich meal, the liver and skeletal muscles remove excess glucose from blood and store it as glycogen.
stimulated by insulin
When glucose levels decrease, the liver secretes glucose in the blood.
breakdown of glycogen
gluconeogenesis - process of converting other molecules into glucose

39. Actions of Insulin and Glucagon

40. Glucose Feedback Loop Blood Glucose Blood Glucose Insulin Glucagon
HIGH
LOW
Blood Glucose
Blood Glucose
pancreas
secrete
secrete
Insulin
Glucagon
stimulates
stimulates
stimulates
absorption
liver
release
Glucose
Glucose
absorption
Target tissue