Nutrition The Digestive System

Nutrition in Protozoa Intracellular digestion Amoebae use pseudopods to engulf food through phagocytosis. Lysosomes contain digestive enzymes to break down macromolecules into building blocks In paramecium, cilia sweep microscopic food into the oral groove – solid wastes are expelled at the anal pore

Nutrition in Cnidirians Hydra employ both intracellular and extracellular digestion. Tenticles bring food to the mouth, and bring the food into a gastrovascular cavity. Once the particles are broken down small enough they are taken into the cells to be completely digested. Undigested material released through the mouth

Nutrition in Annelida They have a complete one way, two opening digestive tract. In order – mouth, pharynx, esophagus, crop (to store food), gizzard (to grind food), Intestings (digestion and aborption), and anus (undigested food released)

Nutrition in Arthropod Similar to annelids except that they have jaws for chewing and salivary glands for better digestion.

Human Digestive System Consists of the alimentary canal and the associated glands. The pathway of the food through the body is: The oral cavity, pharynx, esophagus, stomach, small intestine, large intesting, and rectum. The accessory organs consist of of the Liver and pancreas which deliver secretions into the canal via ducts.

Types of digestion Mechanical digestion Food is crushed and liquified by the teeth, toungue, and peristaltic contractions of the stomach and small intestines This increases the surface area for the digestive enzymes to work on Peristalsis is wavelike muscular action conducted by smooth muscle that lines the digestive system

Chemical Digestion Exocrine glands associated with the digestive system produce secretions involved in breaking moleucules into simple molecules that can be absorbed REVIEW BUILDING BLOCKS OF ORGANIC FAMILIES Chemical digestion of carbohydrates begins in the mouth. Amylase breaks down polysaccharides before food is swallowed

Chemical Digestion In the stomach, gastric glands produce hydrochloric acid and the enzyme pepsin (breaks down protein). Chyme (partially digested food in the stomach) enters the duodenum through the pyloric sphincter. The liver produces bile (used for fat digestions) bile is stored in the gall bladder before being released in the small intestines.

Chemical Digestion The liver also helps regulate blood glucose (excess glucose stored here as glycogen so that in times of need can be released to raise sugar levels) levels and produces urea by breaking down red blood cells. The Pancreas releases pancreatic lipase and makes amylase, trypsin, and chymotrypsin (protein digestion)

Absorption All digestion is completed in the small intestines Small intestines are lined with villi (folds) to increase surface area for more absorption of nutrients Villi contain cappillaries and lacteals (projections of the lymphatic system) and microvilli (little hairs) Nutrients move into blood stream through digestion The large intestines are for water and vitamin K absorption.

Villi