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DIGESTIVE SYSTEM

4 Types of Tissues

1. Epithelial (cover exposed surfaces, line inner passages, forms glands, skin)

2. Connective (fill internal spaces, support other tissue, transport material, store energy, tendons, ligaments)

3. Muscle (contraction, skeletal muscle, provide heat, wall of organ tissues)

4. Neural (carries electrical impulses from brain to rest of the body) 

Muscular System 

Voluntary - Consciously

Involuntary - Naturally; subconsciously  

5 Phases of Digestion

1. Ingestion 

2. Movement 

3. Mechanical & Chemical Digestion 

4. Absorption 

5. Elimination 

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Mechanical Digestion 

- Physical 

- Chew (mastication), tear, grind, mix etc.  

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Chemical Digestion 

- Chemically using enzymes to break down food into simpler substances, e.g. carbs, fats, protein, minerals, vitamin, fibre 

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Gastro Intestinal Tract (GI Tract)

- 1 long tube from mouth to rectum 

- Connecting following organs with it: 

  • Mouth 

  • Esophagus

  • Liver

  • Gall Bladder 

  • Stomach

  • Pancreas

  • Small and Large Intestine

  • Rectum 

 

Mouth 

- Mechanical 

  • Teeth breaking down food

  • Tongue mixing food with saliva 

- Chemical 

  • Saliva contains amylase (digests starch - carbohydrates)

- Food becomes 'bolus' which goes through the epiglottis and through the esophagus ​

- Bucal Cavity: Mouth area

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Esophagus

- Approximately 10" long (leaves space for respiratory system)

- Allows food time to digest 

- Secretes mucus (to lubricate bolus) 

- Mucus traps bacteria 

- Peristalisis moves bolus from the mouth to the stomach (antagonistc muscle pair [work in opposites] present in esophagus)

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Stomach

- Mechanical 

  • Muscles churn chyme in stomach constantly 

- Chemical

  • Enzymes

  • Hydrochloric Acid (HCl) 1.5 pH 

- HCl (digestive juice inside stomach) kills all trapped bacteria in mucus

- Protease (digests protein) and lypase (digests lipids/fats) present in stomach

- Food/HCl mix is called chyme 

- Not enough mucus lining the stomach causes heartburn (stomach starts digesting itself) 

- Approximately 4 hours in the stomach

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Small Intestine 

- Approximately 7 meters long 

- Absorbs digested food material 

- Pancreatic amylase (for all nutrients)

- Has villi and micro villi -> increases S.A. : V & allows materials to be absorbed quicker 

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Large Intestine 

- Approximately 5 feet 

- Accepts waste from small intestine, stays for 4 hours 

- Allows: 

  • Bacterial Digestion 

  • Water Absorption (Also in small intestine)

  • Concentrates waste

- Waste leaves via rectum 

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Appendix 

- Huge in herbivores (diet consists mainly of fibre)

- Contains bacteria (natural flora) to digest cellulose in fibre

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Pharynx - Throat

Larynx - Voice Box 

Bucal Cavity - Mouth 

Figure 1. Entire GI Tract connected with various organs 

Figure 2. Mouth 

Figure 3. Esophagus 

Figure 4. Stomach 

Figure 5. Intestines

Figure 6. Villi 

Accessory Organs

Liver 

  • Largest organ in body

  • Produces bile 

    • A digestive fluid, stored in the gall bladder. Created by the breakdown of RBCs. Helps emulsify fats (breaks down fat globules into smaller globules so that enzymes can work faster [have greater S.A.]) â€‹

  • Filters and breaks down toxins 

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Gall Bladder 

  • Stores bile and releases it in small intestine 

  • Fatty diet causes gallstones 

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Pancreas

  • Production of digestive enzymes

    • Lypase (lipids)

    • Amylase (carbohydrates) 

    • Protease (proteins)

    • Pancreatic Amylase (all)

  • ​Regulates blood sugar by making insulin

    • If brain does not get sugar, there will be cellular damage  

Figure 7. To sum it all up 

Figure 8. Emulsification of fat

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