The Digestive System

What is digestion? How is the food we consume digested?

What is the digestive tract? Flexible & ________ tube Total length: approximately ____________ Composed of numerous structures and ________ Digestive tract_____________ Organs MouthSalivary glands PharynxLiver ______________Gallbladder StomachPancreas Small and large intestine Rectum and ______

Purpose of the digestive tract The Overall Idea: To ingest and __________ your food into forms that can be absorbed and used by the body. To digest food to its _____________ and then to absorb and ____ the nutrients and some non-nutrients in the body, leaving behind the substances, such as fibre, that are appropriate to __________.

4 processes of the digestive system Digestion ___________ and break down foods into ___________ that can be absorbed by the body 2. _____________ Secrete numerous substances including ______________ ______ (stomach), ______ (liver), etc.

4 processes of the digestive system Absorption Absorb ____________ produced by _____________ Across layer of _____________ cells lining the gastrointestinal wall to enter blood or lymph  circulatory system distribute to body 4. _____________ Muscular _______________ that move the contents of the digestive tract __________.

Overview of digestion Step 1 - Mastication Begins in the _________ – chewing breaks down food into smaller pieces, called a __________. Saliva produced by three salivary glands contains _________ that moistens and _____________ food ___________, an enzyme, begins the digestion of carbohydrates

Overview of digestion Step 2 - Swallowing and Peristalsis ____________ act of swallowing the bolus Movement of bolus into pharynx and _____________ _______________ muscular contractions (peristalsis) move food down into stomach

Overview of digestion Step 3 - Secretion/Absorption Stomach (sac-like organ) = ___________ site, dissolves & ___________ digests food, prepares food for digestion & absorption in small intestine Glands in stomach lining secrete hydrochloric acid to _____________ food (except fat), also kills __________ Little absorption occurs across stomach wall

Taking a Look at the pH Scale

Overview of digestion Step 3 - Secretion/Absorption ________ intestine: digestion is completed and most absorption occurs Nine feet in length Comprised of: _____________, ___________, & _________. Most absorption (including vitamins, minerals, & water) occurs in ____________ and ____________ Molecules of carbohydrates, proteins, & fats further broken down by hydrolytic enzymes into __________________, amino acids, and fatty acids (absorbable units)

Overview of digestion Step 3 - Secretion/Absorption ___________ – secretes digestive enzymes & alkaline fluid Alkaline fluid Bicarbonate ions ________________ acidic contents coming from stomach to prevent damage to small intestine wall Provide optimal pH for enzyme function __________ Secretes ________ Bile contains cholesterol, bicarbonate ions, & bile salts _________ _________ essential to digestion & absorption of dietary fats (solubilize fats that are otherwise insoluble in water & convert large fat globules into smaller fat droplets)

Overview of digestion Step 3 - Secretion/Absorption ______________ __________ site for bile (secreted from the liver) until it is needed to __________ (to make into) fat During a meal, walls of gallbladder contract to move concentrated bile into duodenum via ________

Overview of digestion Step 4 - On the Way to Excretion Large intestine Very little water, salts, and undigested material are left Temporarily store materials & concentrate them by reabsorbing salt & water Fibre passes through the large intestine mostly unabsorbed Material moved to the __________ to be eliminated from body

Overview of digestion Step 4 - Excretion Material is now ____________ from the body through contractile activities, including associated ____________ muscles. Also known as “______________”. Overview of digestion