1. Digestion, Respiration, and Circulation.
By: (Your name)

2. Introduction Body contains multiple organ systems.
Focus on three systems
Digestive system
Respiratory system
Circulatory system
The body has multiple organ systems that work together for a common goal.
Here I will focus on three that carry out three essential everyday tasks. I will describe the purpose of each system along with the pathway that material travels through it.

3. Digestion
Purpose - break down ingested materials into their most basic units
Pathway - oral cavity, esophagus, stomach, small intestine, large intestine.
Purpose
To break down ingested materials into their most basic units
This provides energy
This provides materials to repair cells
Pathway
Oral cavity, esophagus, stomach, small intestine, large intestine.
The liver, pancreas, and gallbladder are all also involved although the food is never directly passed through these organs.

4. Organs Involved Primary Organs Stomach Small Intestine Large Intestine
Secondary Organs
Pancreas
Liver
Gallbladder
Primary Organs – food passes and is actively digested here.
Secondary organs – secrete chemicals that pass through ducts into one of the primary organs to aid in digestion.
Stomach – churns food and regulates the amount of food that enters the small intestine at one time.
Small Intestine – site of most digestion.
Large Intestine – no digestion occurs here, but it works to reabsorb water.

5. Molecular Digestion Carbohydrates Proteins Fats
Carbohydrate digestion begins in the mouth with the enzyme amylase and continues in the small intestine with pancreatic amylase.
Protein digestion begins in the stomach with the enzyme pepsin and also conitinues in the small intestine with various chemicals.
Fat digestion begins in the small intestine with the enzyme lipase.

6. Respiration
Purpose - provide the lungs with oxygen to replenish deoxygenated tissues and to remove carbon dioxide from the body.
Pathway - Mouth/nose, trachea, lungs
Purpose
Trade oxygen for carbon dioxide.
Provide the body with the oxygen needed for life
Eliminate toxic carbon dioxide from the body.
Pathway - Mouth/nose, trachea, lungs (bronchi, bronchioles, alveoli)
This is for inhalation
Air travels the opposite way in exhalation
Lungs, trachea, moth/nose.

7. Circulation Purpose - to supply the body with oxygenated blood.
Pathway
Two separate pathways
Pulmonary circuit
Systemic circuit
Purpose
To supply the body with oxygenated blood.
To take carbon dioxide to the lungs to be eliminated
To transport hormones to the appropriate target organs
To carry energy to cells.
Pathway
Two separate pathways
Pulmonary circuit (heart – lungs – heart)
Systemic circuit (heart – body – heart)

8. Circulatory Accessories
Heart
Arteries
Veins
Capillaries
Heart is the primary organ of the circulatory system
Arteries carry oxygenated blood away from the heart
Veins return deoxygenated blood to the heart
Capillaries are the sites where the blood is mixed with the interstitial fluid allowing things to flow either into or out of the blood
Picture
The red represents the oxygenated blood in the arteries
The blue represents the deoxygenated blood in the veins

9. Interrelationships Respiratory and Circulatory
Digestive and Circulatory
Respiratory and Digestive
The respiratory system exchanges oxygen with carbon dioxide in the alveoli of the lungs, but the circulatory system is the actual transportation mechanism that carries these two compounds throughout the body.
There are distinct organs where digestions begins, but the circulatory system is used to transport hormones so that digestion can begin. After the molecules are broken down they are absorbed into the circulatory system and transported to where they are needed.
The portal of entry for both the respiratory system and the digestive system is the oral cavity.

10. References
How Digestion Works. Retrieved January 17, 2009, from Children Memorial Hospital Web site:
Retrieved January 17, 2009, Web site:
Retrieved January 17, 2009, Web site:
The Human Heart. Retrieved January 17, 2009, from The Franklin Institute Web site: