Function and structure: gi tract wall, enteric nervous system, cephalic brain control, regulating the gi tract, digestion-cv relationship. Provide defenses to prevent both infection and autodigestion, remove waste. Protects against pathogens that may have been ingested. Huge role of immune here, and protection of enzymes restricted to gi tract. Tubular gi tract: huge tube and is modified of appearance and function as you move through. Accessory organs: helps break down and digest material and is very important. Teeth, tongue, salivary glands, liver, gall bladder, pancreas. Receptacle for food with specialized structures to facilitate delivery into the gi tract. Provides a swallowing reflex and pushes food nito the esophagus. Split up into different parts of the pharynx: naso, oro, laryngo - pharynx. Epiglottis folds down bc of the pressure of the food, ensuring it doesn"t go into the lungs. Muscular tube with no digestion - passes food from mouth into stomach.