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Questions and Answers
What role does mucus play in the digestive process?
What role does mucus play in the digestive process?
Which enzyme is responsible for digesting proteins in the stomach?
Which enzyme is responsible for digesting proteins in the stomach?
What pH change does the chyme undergo as it moves into the duodenum?
What pH change does the chyme undergo as it moves into the duodenum?
Why are proteases secreted in an inactive form?
Why are proteases secreted in an inactive form?
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What is the primary function of bile in the digestive system?
What is the primary function of bile in the digestive system?
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Which of the following substances protects the stomach lining from acid and enzymes?
Which of the following substances protects the stomach lining from acid and enzymes?
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What is the role of lipase in the digestive process?
What is the role of lipase in the digestive process?
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What is chyme?
What is chyme?
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What is the primary function of the incisors in the human teeth?
What is the primary function of the incisors in the human teeth?
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Which process involves the breakdown of large insoluble molecules into smaller soluble ones using enzymes?
Which process involves the breakdown of large insoluble molecules into smaller soluble ones using enzymes?
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What type of digestion occurs when teeth chop and grind food into smaller pieces?
What type of digestion occurs when teeth chop and grind food into smaller pieces?
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Which part of the tooth is primarily responsible for sensation?
Which part of the tooth is primarily responsible for sensation?
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Which of the following is NOT a function of saliva?
Which of the following is NOT a function of saliva?
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What is the function of the molars in the mouth?
What is the function of the molars in the mouth?
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Which type of digestion increases the surface area for chemical digestion without changing the food chemically?
Which type of digestion increases the surface area for chemical digestion without changing the food chemically?
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Wisdom teeth are known for growing later than other teeth. What is their primary role?
Wisdom teeth are known for growing later than other teeth. What is their primary role?
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What is the primary function of assimilation in the digestive process?
What is the primary function of assimilation in the digestive process?
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Which type of teeth is primarily responsible for tearing food?
Which type of teeth is primarily responsible for tearing food?
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What process occurs when bile breaks down large fat droplets into smaller ones?
What process occurs when bile breaks down large fat droplets into smaller ones?
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What is the main role of dentine in the structure of a tooth?
What is the main role of dentine in the structure of a tooth?
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Which of the following best describes physical digestion?
Which of the following best describes physical digestion?
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Study Notes
Digestion
- Ingestion: Taking in food and drinks through the mouth.
- Egestion: Passing out undigested food through the anus.
- Absorption: Movement of digested food molecules through the wall of the intestine into the blood.
- Assimilation: Movement of digested food molecules into cells where they are used.
Types of Digestion
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Physical Digestion (Mechanical): Breaking down food into smaller pieces without changing the food molecules.
- Purpose: Increase surface area for chemical digestion.
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Examples:
- Teeth biting, chopping, and grinding food.
- Stomach churning food.
- Emulsification of fats by bile.
- Chemical Digestion: Breaking down large insoluble food molecules into smaller, soluble ones using enzymes (hydrolysis).
Stages of Digestion
In the Mouth
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Physical Digestion by Teeth:
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Structure:
- Enamel: Outer layer, hardest substance in the body, can be dissolved by acids.
- Dentine: Living region with channels of cytoplasm, harder than pulp but softer than enamel.
- Pulp: Contains nerves, blood vessels, and cells that make dentine.
- Cement: Bone-like substance attaching teeth to the jaw, allowing slight movement.
- Wisdom Teeth: Teeth at the back of the jaw, grow later than others.
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Functions:
- Help with ingestion and physical digestion.
- Bite off food.
- Chop, crush, or grind food into smaller pieces.
- Facilitate swallowing.
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Structure:
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Types of Teeth:
- Incisors: Sharp edges, cut and bite food (four in each jaw).
- Canines: Pointed, tear food (two in each jaw).
- Molars: Broad and flat, grind and crush food (four in each jaw).
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Saliva:
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Components:
- Water: Helps with digestion, dissolves food, softens food for chewing and swallowing.
- Mucus: Binds chewed food into a bolus, lubricates food, protects the alimentary canal from enzymes and acids.
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Components:
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Esophagus:
- Peristalsis: Waves of muscle contractions that push food through the esophagus towards the stomach.
In the Stomach
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Gastric Juice:
- Hydrochloric Acid: Kills microbes, activates pepsinogen.
- Pepsinogen: Inactive enzyme activated by hydrochloric acid to form pepsin.
- Pepsin: Digests proteins into polypeptides.
- Mucus: protects the stomach wall from hydrochloric acid and pepsin.
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Pepsin in the Stomach:
- Pepsin is secreted in an inactive form.
- Stomach secretes a protective layer of mucus.
- Pepsin breaks down proteins into polypeptides.
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Trypsin in the Small Intestine:
- Proteases: Enzymes that digest proteins (secreted in an inactive form to protect cells).
- Salivary amylase stops acting in the stomach because it is slightly alkaline.
- Chyme: Acidic mixture of food and gastric juice that leaves the stomach.
In the Small Intestine
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Duodenum:
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Functions:
- Emulsifies fats (bile).
- Changes pH of food from acidic to alkaline.
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Functions:
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Ileum:
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Functions:
- Completes digestion of all food types.
- Absorbs digested food.
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Functions:
Bile
- Production: Liver
- Storage: Gall bladder
- Function: Emulsifies fats (breaks down large droplets into smaller droplets)
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Components:
- Bile Pigment: Formed from the breakdown of dead red blood cells, excreted in urine and feces.
- Bile Salts: Emulsify fats.
- Hydrogen Carbonate: Alkaline component of bile.
Enzymes in the Small Intestine
- Lipase: Digests lipids into fatty acids and glycerol.
- Peptidase: Digests polypeptides into amino acids.
- Maltase: Digests maltose into glucose.
Ingestion & Egestion
- Ingestion is the process of taking in food & drinks through the mouth.
- Egestion is the process of excreting undigested food through the anus.
Absorption & Assimilation
- Absorption is the movement of digested food molecules from the small intestine into the bloodstream.
- Assimilation is the process of digested food molecules moving into body cells for use and becoming part of the cells.
Types of Digestion
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Physical Digestion (Mechanical): Breaks down food into smaller pieces without changing the chemical structure of the food molecules. This increases the surface area for chemical digestion.
-
Examples:
- Teeth: Bite, chop, and grind food.
- Stomach: Churns food.
- Emulsification: Bile breaks down large fat droplets into smaller ones.
-
Examples:
- Chemical Digestion: Breakdown of large insoluble molecules into smaller soluble ones using enzymes. This involves breaking down bonds (hydrolysis).
Stages of Digestion: Mouth
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Physical Digestion by Teeth:
- Enamel: The hardest substance in the body, outer layer of tooth, can be dissolved by acids.
- Dentine: Living region containing channels of cytoplasm, hard but not as hard as enamel.
- Pulp: Contains nerves for sensation, blood vessels for supply of food and oxygen, and cells that make dentine.
- Cement: Bone-like substance with fibers attaching the tooth to the jaw bone, allowing slight tooth movement.
- Wisdom teeth: Located at the back of the jaw, develop later than other teeth.
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General Functions of Teeth:
- Help with ingestion and physical digestion.
- Bite off pieces of food.
- Chop, crush, or grind food into smaller pieces, increasing surface area for enzyme action.
- Facilitate swallowing.
-
Types of Teeth:
- Incisors: Sharp edges for biting and cutting food, located at the front of the mouth (four in each jaw).
- Canines: Pointed for tearing food, two in each jaw.
- Molars: Four in each jaw (two on each side), broad for grinding and crushing food, one or two cusps and roots.
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Saliva: Contains:
- Water: Aids digestion, dissolves food, softens food for chewing and swallowing.
- Mucus: Binds chewed food to form a bolus, lubricates food for easy movement down the alimentary canal, covers the inner surface of the alimentary canal to protect it from enzymes and acidic juices in the stomach.
Stages of Digestion: Oesophagus
- Peristalsis: Waves of contraction and relaxation of muscle walls in the alimentary canal push food towards the stomach.
Stages of Digestion: Stomach
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Stomach Secretes:
- Hydrochloric Acid: Kills microbes, activates pepsinogen into pepsin.
- Pepsinogen: Inactive enzyme activated by hydrochloric acid to form pepsin. Pepsin digests proteins into polypeptides.
- Mucus: Protects the stomach wall from hydrochloric acid and pepsin.
- Pepsin: Digests proteins into polypeptides.
- Chyme: Food mixed with gastric juice and leaving the stomach, acidic.
Stages of Digestion: Small Intestine
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Duodenum:
- Functions: Emulsifies fat, changes the pH of food from acidic to alkaline.
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Ileum:
- Functions: Completes the digestion of all food types, absorbs digested food.
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Bile:
- Formed in the liver.
- Stored in the gall bladder.
- Contains:
- Bile pigments: Formed in the liver from the breakdown of red blood cells, excreted in urine and feces.
- Bile salts: Emulsify fats (break down large fat droplets into smaller droplets), contain hydrogen carbonate (alkali).
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Pancreatic juice contains:
- Lipase: Acts on lipids, digesting them into fatty acids and glycerol.
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Trypsin: Acts on proteins, breaking them down into polypeptides.
- Note: Proteases (enzymes that digest proteins) are secreted in inactive form to prevent them from digesting the cells that produce them.
- Amylase: Acts on starch, digesting it into maltose.
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Intestinal juice contains:
- Peptidase: Acts on polypeptides, digesting them into amino acids.
- Maltase: Acts on maltose, digesting it into glucose.
- Salivary amylase: Stops working in the stomach because it acts in slightly alkaline conditions.
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Description
Test your knowledge on the digestion process, including stages such as ingestion, egestion, absorption, and assimilation. Explore physical and chemical digestion methods and their significance in human health.
