Digestion – “How do we acquire…”

Diary of a toast you are about to eat Mouth Anus Mouth Epiglottis large intestine Esophagus pyloric sphincter cardiac sphincter stomach small intestine tongue pharynx rectum anus

Two modes of digestion Mechanical Chemical Breaking down of food physically Increases Surface area Chemical Enzymes break down organic molecules into smaller pieces Use two different colours to label where these two modes of digestion occur

Job of Salivary glands Three pairs of salivary glands secrete juices Sides of the face: below & in front of the ears Ducts open on the inner surface of cheek Beneath the tongue Beneath the floor of oral cavity Ducts open under the tongue Saliva contains salivary amylase Starts to break down starch

Chewing & swallowing in detail In the Pharynx: food & air passage cross Trachea in front of esophagus Swallowing = reflex action (done without conscious thought) To stop food going up the nose: Soft palate moves back to close off the nasopharynx To stop food going into the lungs: Trachea moves up under the epiglottis to cover the glottis (opening to voice box/”larynx”) Swallowing & breathing does not occur simultaneously

Job of the Esophagus Transfer food from mouth to stomach “Sphincters” = muscles encircling tubes that can act as valves Heartburn = when stomach contents escape into the esophagus Vomiting = abs (abdominal muscles) & diaphragm propels stomach contents up

Job of the Stomach (“gastric”) 25cm (10 inches) in length Can hold up to 4 liters!!! Both Mechanical & Chemical digestion: Muscular wall – churns to mix food with gastric juice Produces juices – gastric glands produce gastric juice Empties in about 2-6 hours

Entrance & Exit Doors of the Stomach

Job of the Stomach (“gastric”) Pepsinogen Turns into pepsin with help of HCl Hydrochloric acid / HCl Kills most of the bacteria at pH 2 Breaks down connective tissue of meat Mucus Think layer of mucus protects wall

What do these organs look like in real life? Look at the microscopic slides of: Salivary glands Esophagus Stomach Draw what you see Label parts using the internet/textbook Relate structure to function

Job of the Small Intestine Smaller diameter than the large intestine Length? 6 meters (18 ft) in length “Duodenum” = first 25cm of small intestine Receives Bile from Liver Receives Pancreatic juice from the Pancreas Full of villi: microscopic extensions called microvilli Absorbs nutrients

Villus in detail Blood capillaries absorbs sugars and amino acids Lacteal absorbs lipoprotein droplets Glycerol & fatty acids enter epithelial cells / lining where they are packaged into lipoprotein droplets

Job of the Large Intestine Larger in diameter than the small intestine Absorbs water, salts and some vitamins Stores indigestible material Bacteria living in it break down indigestible material & produce some vitamins (i.e. vitamin K = important for blood clotting) Bacteria from yogurt can increase the amount of bacteria living here

Large Intestine in detail

Poop ¾ Water ¼ Solids (Bacteria, fiber, other indigestible materials) BROWN because of broken down bilirubin (breakdown product of hemoglobin) & oxidized iron in hemoglobin ¾ Water ¼ Solids (Bacteria, fiber, other indigestible materials) Bacteria reacting with indigestible materials cause FART and SMELLY POOP “Defecation Reflex:” stretching of rectum wall → Nerve impulses to spinal cord → Contraction of rectal muscle & Relaxation of internal anal sphincters

Other Poops Diarrhea Infection of the lower intestinal tract: Increase in peristalsis Water not absorbed Nervous stimulation 2. Constipation Inhibition of defecation

What do these organs look like in real life? Look at the microscopic slides of: Duodenum Small intestines Large intestines Draw what you see. Is there a significant difference among the three parts? Label parts using the internet/textbook Relate structure to function