Digestive System

Organs of Digestion

Four components of digestion:

Component RoleIngestion The taking in of nutrientsDigestion Break down of molecules into

complexesAbsorption Transport complexes to body tissuesEgestion Removal of indigestible materials

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Digestive tract = Alimentary Canal

Alimentary Canal = Open ended muscular tube around 7meters long.

Two types of digestion

Physical Digestion: Breaking up food using forceeg. Teeth chewing, Stomach churning

Chemical Digestion: Breakdown of food using chemical reactions.eg. Stomach acid,

Beginning of Digestion

Chewing: Physical digestion that mixes food with saliva produced by the salivary glands. The chewing and mixing with saliva creates a food bolus

Function of saliva: 1) Activate taste buds 2) Lubricate food so it slides easily down the esophagus. 3) Contains the digestive enzyme amylase4) Dissolves food particles which can activate the taste

buds

Amylase Enzyme

Amylase Enzyme: Breaks down starches to smaller-chain sugars, dextrins

Teeth and Their StructureComparing Different types of teeth for different

animals.

Understanding Human TeethCarnivores: All teeth are wedge shaped (no flat

molars) Teeth come together in a scissors like motion for tearing meat off the bone and breaking bones. Large canines for holding onto prey

Carnivore Teeth

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Teeth and Their Structure

Herbivores: Flat like incisors. Large flat grinding molars

Teeth and Their StructureOmnivores (Bear, Pig): Multipurpose teeth. - carnivore-like: Sharp incisors, Wedge like premolars, large

canines- Herbivore-like: Slightly flattened grinding molars in the very

back

Teeth and Their StructureHumans: Mainly herbivorous teeth. Some minor modifications- Omnivore-like: Sharp incisors, - Herbivore-like: Flat grinding molars in the back. Reduced

canines

Teeth and Their StructureHumans: Mainly herbivorous teeth. Some minor modifications- Omnivore-like: Sharp incisors, - Herbivore-like: Flat grinding molars in the back. Reduced

canines

Oral Cavity to Stomach

After food is chewed and mixed with saliva:

Esophagus: A muscular tube that runs from the mouth to the stomach

Peristalsis: The muscular contractions that occur in the esophagus pushing food towards the stomach.

Peristalsis

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Stomach

Stomach: A acid filled, muscular, mucus lined sack

Function:1) Storage of food (1.5 L)2) Initial digestion of

proteins

StomachSphincter: A circular muscle that

controls the passage of materials

Cardiac Sphincter: Controls the amount of food that enters the stomach. Prevents stomach acid from leaking into the esophagus.

Heartburn: cardac sphincter allows some stomach acid to leak into esophagus and break down the esophagus wall

Stomach

Sphincter: A circular muscle that controls the passage of materials

Cardiac Sphincter: Controls the amount of food that enters the stomach. Prevents stomach acid from leaking into the esophagus.

Heartburn: cardac sphincter allows some stomach acid to leak into esophagus and break down the esophagus wall

Stomach

Pyloric Sphincter: Regulates the amount of food entering the small intestine from the stomach.

Cells in the Stomach Wall

Cell FunctionMucous Cell

Secrete a protective mucous lining

Parietal Cell

Secrete Hydrochloric acid

Peptic Cell

Secretes a protein digesting enzyme, Pepsinogen.

Pepsin

Pepsinogen (inactive form): gets converted to pepsin (active form) once it reaches the acid.

Pepsin (active): breaks Protein chains into smaller chains called Peptones

Rennin

Rennin: Slows the passage of milk through the digestive tract. This increases the time allowed for it to breakdown (more nutrients can be extracted)

Adults: Cannot function in the acid stomach of an adult.

Baby: Allows the milk to curdle (forms solid clumps) Solids move through the digestive tract at a slower pace.

Assignment

Questions: