Digestion There are 2 types of digestion: Mechanical Digestion – breaks food into smaller pieces to increase surface area exposure to digestive enzymes Chemical Digestion – breaks organic compounds into their building blocks
Mechanical/ Chemical Digestion Chewing Salivary glands release saliva which moistens the chewed food, now called a Bolus. The tongue pushes the bolus to the back of the throat, called the Pharynx. A flap of skin called the Epiglottis flips down and covers the entrance to the Trachea during swallowing Swallowing Swallowing Digestion Overview Digestion Overview
Peristalsis/Alimentary Canal The bolus passes through the esophagus by peristalsis Peristalsis Peristalsis Food continues to pass through the Alimentary Canal (any part that food passes through) Mouth-Pharynx-Esophagus-Stomach- Small Intestine-Large Intestine-Anus Accessory organs play a role in digestion, but food never enters them Salivary glands-Pancreas-Gall Bladder- Liver
Chemical Digestion Enzymes break down the organic compounds (polymers) into their building blocks (monomers) so they can be absorbed into the blood stream and transported to all cells Carbohydrates – Simple sugars Protein – Amino acids Lipids – Glycerol and 3 Fatty acids Nucleic acids - Nucleotides
Look in your textbook Chapter 38-2 Compare the digestion of Carbohydrates and Protein. Follow the digestion of Carbs from the time they enter your mouth until the end products are absorbed into your blood. Do the same for Protein.
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Digestion of Carbohydrates Mouth – Mechanical digestion breaks the carbs into smaller pieces to increase the surface area exposure to enzymes. Saliva lubricates the bolus. It contains the enzyme Amylase which begins the Chemical digestion of Carbs. Polysaccharides are broken into shorter chains. Swallowing pushes the bolus into the esophagus
Carbs in the Stomach Peristalsis moves the bolus to the stomach. Cardiac sphincter opens and bolus enters the stomach Bolus now mixes with the gastric juices of the stomach. This acidic mixture is now called Chyme Mechanical digestion (churning) continues No chemical digestion of Carbs here because of the acidity of the chyme Protein is digested here
Carbs in the Duodenum Pyloric sphincter opens and chyme moves into the duodenum. Pancreas secretes: Alkaline secretion that neutralizes the acidic chyme Pancreatic amylase and disaccharase continue the breakdown of carbs into simple sugars
Absorption of Simple Sugars Small intestine is about 6 meters long! The lumen of the small intestine is lined with Villi.
Absorption of Carbs Each villi has microvilli on it’s surface The infolds increase surface area contact so the simple sugars can pass into the blood by diffusion.
Small Intestine Absorption is complete here. Peristalsis moves the digested food mass to the Large Intestine (Colon)
Large Intestine Main function is to absorb water from the unusable waste that remains. Too much water absorption – constipation! Not enough water absorption – diarrhea! Bacteria in colon produce Vitamin K Feces passes from descending colon to rectum and then is excreted through the anus (anal sphincter)
Accessory organs and their Functions Salivary glands – Amylase Pancreas – Amylase - Disacharase Liver – produces bile which is stored in the Gall Bladder and secreted into the duodenum through the Common Bile Duct - Bile emulsifies fats
Digestion Human Digestion Human Digestion Have another look Have another look Digestion Animation Digestion Animation
Digestive Problems Heart burn – acidic gastric juice enters the esophagus Gastric ulcer – mucus lining of the stomach deteriorates and the gastric juice of the stomach begins to digest the stomach wall Pig Dissection Pig Dissection