Digestive System Anatomy and Function Functions Convert food into smaller molecules that can be absorbed by cells Remove solid waste B. 2 Major components 1. The Alimentary Canal (your food tube) 2. Digestive glands How does digestion relate to cellular respiration?

Digestive System II. The Alimentary Canal Mouth – Two types of digestion Mechanical digestion – Tear & crush food (chewing) Chemical digestion Saliva – produced by salivary glands, moisten food making it easier to chew Contains amylase (breaks down carbs) and lysozyme (kills bacteria) Release of saliva is triggered by the nervous system by the scent of food. Amylase breaks the chemical bonds in starches and releases sugar, which is why if you eat a cracker long enough, it will start to taste sweet. Lysozymes fight infection by digesting the cell wall of many bacteria.

Digestive System Pharynx (throat) Connects mouth to esophagus Swallow chewed up food ball called a bolus Epiglottis covers the trachea – Why? Epiglottis

Digestive System Esophagus Moves food to the stomach by peristalsis (Fig. 38-11) Cardiac Sphincter Thick ring of muscle that closes the esophagus after food enters the stomach. Why is this important? Heartburn What causes it? Gravity is not the cause for food traveling to stomach; wave of contraction push food down

Digestive System Stomach Food mixes with hydrochloric acid (HCl) and pepsin to form chyme. Stomach can hold up to 2 L of food or liquid. HCl kills bacteria and disrupts the extracelliular matrix that binds cells in meat and plants.

Digestive System HCl activates pepsin Pepsin breaks down large protein molecules into small chains of ???? Stomach can hold up to 2 L of food or liquid. HCl kills bacteria and disrupts the extracelliular matrix that binds cells in meat and plants. What protects the stomach from pepsin and HCl?

What is pyloric stenosis? Digestive System After 1-2 hours, pyloric valve opens and chyme flows into the small intestine. What is pyloric stenosis?

Digestive System F. Small Intestine Duodenum (~ 1 foot long) This is where most of your food is digested and absorbed 3 Sections: Duodenum (~ 1 foot long) Digestive enzymes from the pancreas and the liver are added to the food. The gall bladder adds bile The pancreas adds sodium bicarbonate is also added…WHY? 10 feet long

Digestive System Jejunum (~ 3 feet) and Ileum (~ 6 feet) The inside of the intestine is not smooth but has many small folds called villi and the villi have many microscopic folds called microvilli. Why all of the folds? Once absorbed, how do nutrients get to cells? Villi Microvilli

Where is your appendix? Appendix

Digestive System Large Intestine (Colon) Reabsorbs water from undigested material What happens when too much water is absorbed? Too little? Bacteria in colon produce Vitamin K and live off undigested organic material (e.g. E. coli) Bacteria generate gases (methane and hydrogen sulfide) as a by-product of their metabolism  Remaining undigested material (feces) is excreted through the rectum and anus 5 feet long. Vit K controls blood clotting

Large Intestine (Colon)

Alimentary Canal (Gastrointestinal “GI” Tract) 1. Mouth 2. Pharynx 3. Esophagus 4. Stomach 6. Large Intestine 5. Small Intestine 7. Rectum

Accessory Organs Glands 10. Liver 9. Pancreas (behind stomach) 8. Salivary Glands 10. Liver 9. Pancreas (behind stomach) 11. Gall Bladder

III. Digestive Glands Liver Detoxifies the blood Stores vitamins and minerals Converts foodstuffs from one form to another Produces bile Bile contains no digestive enzymes, but it has salts which help digest fats. Bile also contains pigments that are by products of RBC destruction in the liver.

III. Digestive Glands (cont) Gall Bladder 1. Stores and releases bile 2. Bile emulsifies fats Pancreas Produces ???? And ???? Digestion Recap…