Digestive System

Unit 9 - Systems

Learning Targets

• Compare and contrast digestive system types of different animals.
• Describe the functions of a digestive system and the organs that are involved.
• Explain how the structure of digestive system parts help with their function.

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Human Digestion

Human Digestion

Overall Goal

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• Allows your body to get the nutrients and energy it needs from the food you eat by breaking it down with all organs

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Order of Structures that food passes through

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• Mouth → esophagus → stomach → small intestine → large intestine → rectum
• AKA the Alimentary Canal

Nutrients Digested

• Macromolecules:
• Carbohydrates
• Main source of energy.
• AKA Sugars.
• Fats
• Needed for cell membranes, myelin sheaths, and certain hormones.
• AKA fatty acids or lipids
• Proteins
• Supply raw material for growth and repair of structures such as skin and muscle.
• AKA peptides or amino acids

• Other Nutrients:

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• Water
• Needed for cell processes.

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• Vitamins
• Regulate body processes.
• Ex: A, B6, B12, C, D, E, K

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• Minerals
• Needed in small amounts for various body functions.
• Ex: Potassium, Calcium, Iron, Sodium

Mechanical vs. Chemical Digestion

• Mechanical:
• Breaks food down into smaller chunks by physically crushing, mixing, or churning food.
• Structures: mouth (teeth & tongue), stomach, small intestine

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• Chemical:
• Breaks food down into its macromolecules using chemicals created by the body
• Macromolecules are smaller, simpler nutrients that cells can absorb.
• Structures: mouth (saliva w/ amylase), stomach (pepsin, hydrochloric acid), small intestine (mix of enzymes), liver/gallbladder (bile), pancreas (insulin and other enzymes).

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Mouth

Mechanical Digestion

• Uses teeth to make the food mushy and easy to swallow.
• Incisors and canines (front teeth) used to bite or tear at food.
• Molars (back teeth) used to grind food.
• Use the tongue to push food around and break it down more.

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Chemical Digestion

• The salivary glands help break down carbohydrates & fats into simpler molecules by releasing enzymes (like amylase) in the saliva.

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Esophagus

• Connects the throat above with the stomach below. Food bolus is not digested here, this is just a path to the stomach.

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• Epiglottis prevents “wrong tube syndrome”- food entering into the respiratory tract / windpipe.
• found at the top of the esophagus, a flap of skin that covers the windpipe when we are swallowing

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• Peristalsis - a process of involuntary muscle contractions that force food down esophagus.
• *This is why we can eat upside down!

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Stomach

3 main functions:

• Storage of food and liquid
• Mix food, liquid, & digestive juice
• Empty contents slowly into small intestine.

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Mechanical Digestion

• Food continues to break down through muscle contractions.

Chemical digestion

• Hydrochloric acid and pepsin (an enzyme) break down food (proteins) further.
• Food mixed with gastric juices is called “chyme”.

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*This yellow portion is not currently in your notes, please add it to your notes!

Chemical Digestion

• Secretes digestive enzymes: Amylase, Trypsin, and Lipase

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Absorption

• Contains villi that are folds which increase surface area = More absorption!
• 2 inches wide x 22 feet long….lots of surface area!
• Food stays here for about 4 hours to optimize absorption.
• Absorbs
• 80% ingested water
• Electrolytes, vitamins, minerals
• Carbs (sugars/starches)
• Proteins (amino acids / peptides)
• Lipids (fats / fatty acids)

Small Intestine

Pancreas

• Accessory organ

Chemical Digestion

• Produces a juice that contains a wide array of enzymes to break down carbohydrates, fats, and proteins in food.

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Liver

• Accessory organ

Chemical Digestion

• Filters out harmful substances or wastes, turning some of the waste into bile—a digestive juice.
• Bile is stored between meals in the gallbladder
• The bile acids dissolve fat into the watery contents of the intestine

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Large Intestine

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• Most indigestible material (waste) comes here. It will eventually be eliminated as feces.

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Absorption

• Last chance to absorb the water and some minerals into the blood.
• Rectum- ~18 to 24 hours the remaining indigestible material exit the body.

White Board Review!

Label the pig with the following terms: anterior, posterior, ventral, dorsal

White Board Review

• What are at least 5 characteristics of animals?

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• How do earthworms, planarian, hydra, and sponges “eat?”
• What are some important structures that help them to do so?

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White Board Review

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• I take a bite of a sandwich and have NO IDEA where the food is going, give me the correct pathway the sandwich will travel through my body.

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• List the parts of the digestive system that we covered and explain what they breakdown.