BIO 121 Lecture Notes - Lecture 18: Pylorus, Gastric Glands, Esophagus
24 Jul 2020
School
Department
Course
Professor
Document Summary
Food subjected to physical/chem changes for absorption food nutrients too large (cannot pass thru cell membrane) Physical breakdown of food into small particles increase tsa. Req jaws, jaw muscles & teeth: incisors cutting, chopping, gnawing, canines stabbing, ripping, shredding, molars/premolars shearing, crushing, grinding. In most, digestion is extracellular (external to the body) Food mixed with saliva & amylase from salivary glands as chewing breaks big sugars into smaller saccharides. Food triggers sensory nerves that cause reflex swallowing action. Goes through pharynx & thru oesophagus: larynx & epiglottis closed to ensure food doesn"t go down trachea. Peristalsis wave of smooth muscle contraction moving food down: oesophageal sphincter maintains unidirectional flow of food into stomach. Lining consists of pitted, folded (increases tsa) layer /w gastric glands: there are cells that prod mucus, enzymes & secrete acids. Zymogen secrets pepsinogen pepsinogen activated by hcl to convert to pepsin (active form: pepsin acts on large polypeptide chains & breaks them down.
