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co12 R. = Reproduce H. = Homeostasis C. = Cells A. = Adapt G. = Grow and develop E. = Run energy transformations R. = Respond

12-3 INGESTION – Act of taking in food and drink into body DIGESTION BREAKDOWN – Chemical and Physical ABSORPTION – Nutrient molecules absorbed from gut into bloodstream ELIMINATION – Ridding the body of undigested food waste

During Mechanical digestion food is broken down to create more surface. Food is mushed up and broken apart. Example. Chewing with teeth or churning food in stomach. No new molecules are produced!

During Chemical digestion food molecules are broken down by enzymes to produce brand new smaller molecules. This requires digestive enzymes and water as a substrate to run these hydrolysis reactions.

In many parts of the digestive tract both types of digestion are happening simultaneously. For example: in the stomach.

Fig. 12.1

Fig. 12.2a

Fig. 12.2b

12-10 Tonsils at the back sides of the mouth protect against infections. Tonsillitis results when the tonsils become inflamed; the infection can spread to the middle ears. Three pairs of salivary glands (parotid, sublingual, submandibular) send saliva (containing salivary amylase for digestion of starch to maltose) into the mouth.

Fig. 12.3

12-12

Fig. 12.4

12-14 The esophagus is a muscular tube that conducts food through the thoracic cavity and diaphragm into the stomach. Peristalsis begins in the esophagus; this collapsed tube moves the bolus of food downward after swallowing occurs. Heartburn is a burning pain when acidic stomach contents enter the esophagus. Peristalsis in Esophagus

Fig. 12.5

1. Storage of a meal – most expanded structure along the alimentary canal

2. Mechanical Digestion of food – Stomach is very muscular and it squeezes to churn and mix food to physically break it down

3. Chemical Digestion of food – Adds PEPSIN enzyme to start chemically breaking proteins into small peptide chains

4. Protection against Germs – HCl helps activate enzymes but it also helps kill many of the bacteria that we ingest.

Fig. 12.6

The Duodenum is only about 45 cm (18 inches long) but it plays a couple of very important roles: 1. Receives incoming Stomach Chyme, Pancreatic Juices and Bile from Liver and Gall bladder. 2. Secretes digestive juces/enzymes from duodenal glands

Fig. 12.8

1. Receives undigested waste and helps absorb fluid from those wastes back into the bloodstream, to help keep us from dehydrating 2. Helps compact and form feces. 3. Harbours helpful bacteria which can further break down wastes to free up minerals and some bacteria will help produce and free up some vitamins, such as Vitamin K

Fig. 12.9

Fig

Fig

The gall bladder is a sac-like oran that sits inferior (below) the liver. It stores bile that was produced in the liver. When activated it will secrete this bile into the Duodenum. This bile will help emulsify fats to create more surface area so that hydrolytic lipases (fat enzymes) can break the fat down chemically.

The pancreas is a glandular organ that acts both as an Exocrine Gland and also as an Endocrine Gland. We mostly focus on its exocrine role. It produces a variety of hydrolytic digestive enzymes that help chemically finish off the digestion of Carbohydrates, Fats and Proteins.