Digestive System Digestive System The digestive system breaks

Digestive System

Digestive System The digestive system breaks down food both mechanically and chemically in order to release nutrient that the body’s cells can absorb and use.

Mouth & Salivary Glands • Teeth grind, hold, tear and chew (mechanical digestion) • Tongue moves food, aids in swallowing = forms a bolus (ball of food) • Pharynx receives food (also air from nose) • Salivary glands-secrete saliva which contains enzymes (breaks down food more) (chemical digestion)

Esophagus • Muscular tube connecting mouth to stomach • Peristalsis (wave-like contractions) push food down (mechanical digestion)

Stomach • Acidic environment (digestive juice containing enzymes (chemical digestion) breaks down food) • Sphincters at start and end of stomach are muscles that control movement of food in/out of stomach • Muscle layers contract to churn and mix food (mechanical digestion) • Mucus part of stomach lining = protects the stomach from digestive juices • Some absorption occurs here (water, alcohol and aspirin)

• 7 m long & large surface area due to finger-like projections called villi (where nutrients are absorbed into the blood) • Where most of the nutrient absorption occurs • Site of chemical digestion (including protein & carbohydrate digestion) • Fat digestion starts here (aided by liver and pancreas) • Pancreatic juices from pancreas & bile from liver enter here Small Intestines

Side note: Celiac Disease • Autoimmune disease: cannot eat gluten • Villi that lines small intestines are damaged by gluten protein • Prevents nutrient absorption.

Accessory Organs • Organs that are involved in digestion, but are not part of the continuous muscular tube of the digestive tract • Include: – Liver – Gall bladder – Pancreas Do not directly digest food themselves… only contribute to the process!

Liver • Produces bile for fat digestion in intestines • Stores carbohydrates & eliminates harmful substances (detoxifier)

Gall Bladder • Stores and concentrates bile from liver • Releases bile into small intestine

Pancreas • Produces pancreatic juice contains enzymes to digest nutrients. • Makes bicarbonate to help lower acidity of stomach • Pancreatic juices enter the small intestine at its upper part. • Releases hormones to control blood sugar levels.

Large Intestines (Colon) • 1. 5 m long • Food is no longer broken down by this point. • Absorbs water (mostly), vitamins and minerals • Secretes mucus to help with movement of food • Stores unused solid material till brain tells it to be voided 32 hours for food to pass!

Rectum • Final straight portion of the large intestine • Stores solid waste and controls its release