The Digestive System Nutrients Nutrients substances in food

The Digestive System

Nutrients • Nutrients: substances in food that supply energy and raw materials for growth, repair, and maintenance • Nutrients needed by body are: water, carbohydrates, fats, proteins, vitamins, and minerals

Water • Most important nutrient • many body processes & chem rxns take place in water • Composes most body fluids

Carbohydrates • main energy source • Sugars broken down by digestive system and placed in blood stream • Sugars are stored in tissue to create ATP

Fats • Mainly used for cell membranes • Insulation and protection • Also used for hormones and myelin sheaths

• Raw materials for growth and repair structures – Skin and muscle • Hormones and enzymes – Insulin – hemoglobin Proteins

Vitamins • Vitamins: organic molecules that regulate body processes • Work with enzymes • From our food; We cannot make them (except vitamin D)

Minerals • Minerals: inorganic nutrients needed in small amounts • Calcium: bones • Iron: hemoglobin

• Gastrointestinal tract: long, winding tube which begins with the mouth and ends with the anus • Digestion: process of breaking down food into molecules the body can use

Mechanical Digestion • Teeth tear food into smaller pieces • Tongue and palate form a small ball of food called a bolus • Esophagus moves food to stomach by a series of wavelike contractions called peristalsis • Stomach mixes and churns the food

Chemical Digestion • Salivary amylase in saliva starts to break down starch into smaller sugars (glucose) • Pepsin in stomach starts to break down proteins* Reason why diabetics have to inject insulin. If taken by mouth the peptide hormone insulin will be broken down into smaller subunits of proteins called amino acids.

Esophagus • 10 inch tube that connects the pharynx with stomach • Located between trachea and spine • Peristalsis moves food from pharynx to stomach • Mucus is secreted in lining to moisten and aid in movement of food

Stomach • Located between the esophagus and the small intestines • sphincters at each end control movement of material in and out • Contains pepsin • Contains HCL(hydrochloric acid); acidic environment aids digestion • Lining secretes mucus to protect stomach wall against being burned by HCL

Ulcer

Liver- Accessory Organ of Digestive System • Produces bile - emulsifies fat to help digestion by enzymes • Also filter blood of harmful and toxic substances like alcohol, and drugs

Gall Bladder-Accessory Organ • Stores bile • After eating a meal the gall bladder will contract and squirt bile into small intestine.

Pancreas – accessory organ • Helps neutralize stomach acid • Pancreatic enzymes digest carbs, lipids, proteins, and nucleic acids

Small Intestines • Located between the stomach and the large intestines • About 23 ft. long • About 1 inch in diameter • Site of absorption of nutrients • Contain villi and microvilli-fingerlike extensions that increase surface area • Chemical digestion of lipids, proteins and carbohydrates • Receives bile from gall bladder/liver, and enzymes from the pancreas

Villi (Villus sing. )

Large Intestines • absorption of water from undigested material occurs • Bacteria present which aid in production of vitamin K • Taking antibiotics can cause a vitamin K deficiency

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Appendix www. kucau. net/. . . /uploads/2007/10/appendix. jpg