1. Chapter 18
DIGESTIVE SYSTEM

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State Standards
8) Outline basic concepts of normal structure and function of all body systems, and explain how homeostasis is maintained.
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Objectives
Students will be able to label major organs and linings of the digestive system
Students will 3 accessory organs that aid in breaking down food.
Students will describe the role of each organ in the digestive system
Students will trace the path of food through the digestive system
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4. Digestive system and homeostasis
Helps to maintain homeostasis through proper pH balance in the gastric environment.
pH is the alkalinity (base) or acidity (acid) of a substance.
Kills unwanted substances and digests food
Discussion
How does the digestive system effect other body systems? Which ones?
What is the normal pH level in the upper stomach? Lower stomach?
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5. LINING OF THE DIGESTIVE SYSTEM
Peritoneum - two-layered membrane
2 parts
Mesentery - part that attaches to posterior wall of abdominal cavity
Greater omentum - anterior portion
Discussion Why do we need mesentery and greater omentum? What would happen if it was not there?
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Omentum
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8. FUNCTIONS OF THE DIGESTIVE SYSTEM
Break food into smaller pieces
Change food chemically into fat, carbohydrates, and protein
Absorb nutrients into blood capillaries of small intestines
Eliminate waste products of digestion
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ORGANS OF DIGESTION
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ORGANS OF DIGESTION
Accessory structures contribute to digestion
Mouth
Teeth
Tongue
Salivary glands
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ORGANS OF DIGESTION
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12. Discussion and Activity
What is the path that food travels through the digestive system?
How do each of the accessory structures contribute to digestion?
Draw the path of the digestive system in your notes. Label each organ and draw arrows tracing the path.
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ESOPHAGUS
The esophagus is a muscular tube beginning at the lower end of the pharynx (back of the mouth) , passes through the diaphragm and connects to the upper portion of the stomach
Discussion
Is the esophagus a voluntary or involuntary muscle?
-What substances do we swallow other than food? What happens to people who have difficulty swallowing?
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STOMACH
Stomach is divided into 3 portions
Fundus - upper part
Greater curvature (body) - middle
Pylorus - lower portion
Gastric juices are secreted by millions of gastric glands
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16. Divisions of the stomach
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17. Discussion and Activity
What is the purpose of gastric juices?
What would happen to the food we eat if we did not have gastric juices?
What is the digested food that leaves the stomach called?
Draw a stomach to add to your notes. Label the different sections.
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SMALL INTESTINE
The final break down of food to be absorbed occurs in the small intestine
Divided into three sections
Duodenum
Jejunum
Ileum
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SMALL INTESTINE
Digestive juices
Secretions from the accessory organs help break down food further so that it can be absorbed once in the small intestine. (will discuss further in the next few slides)
Absorption in the small intestine is accomplished through millions of villi.
The indigestible portion is passed through to the large intestine
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Villi
Increase the surface area of the small intestines
The carbohydrates and proteins in the chyme enter the bloodstream passively via the vein and artery
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22. Discussion and Activity
Compare and contrast the stomach and small intestines jobs/functions
Can you live with only a portion of these organs?
What might happen if you suddenly didn’t have a portion of your small intestine?
Draw the Villi of the small intestines to add to your notes. What do villi resemble?
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23. LIVER/ACCESSORY ORGAN OF DIGESTION
Functions of the liver
Manufactures bile which is necessary for fat digestion
Produces and stores glucose in the form of glucogen
Detoxifies alcohol, drugs and other harmful substances
Manufactures blood proteins
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24. LIVER/ACCESSORY ORGAN OF DIGESTION
Stores vitamins A, D, and B complex
Breaks down hormones no longer useful to the body
Removes old red blood cells and recycles iron content
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26. Discussion and Activity
Can you live with only a portion of a liver?
What body systems would be affected if the liver malfunctions?
What color is the skin of someone who has liver problems? What is this called?
Draw a liver to add to your notes
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GALLBLADDER
The gallbladder stores and concentrates bile when it is not needed by the body
Discussion
Can you live without a gallbladder?
_____ is a common surgical procedure to remove the gallbladder.
Where would the incision be made in relation to the belly button?
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LARGE INTESTINE
Chyme is semi-liquid food in the large intestine
Colon has 3 sections
Ascending
Traverse
Descending
Anal Canal-last portion of the large intestine
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Discussion
The Chyme (digested food) going through the large intestine has already had most of the useful substances removed from it. So why do we have to have a large intestine? What is it doing that is different from the small intestine?
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32. Path through the digestive system
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Activity
Within your small groups Create a flip diagram of the digestive system organs (see example)
Cut out organs and add them to poster board
Label the front of the cut outs (Name of the organ and any sections)
On the backside of the cut outs include
Job of the organ
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