3.3 DIGESTIVE SYSTEM
Digestive System One long muscular tube Approximately 10 m in length (adult) Generally a one-way tract Break down the food we eat into small molecules that can be metabolized (used for energy) by individual cells in our body We must eat food that contains nutrients Ex: Carbohydrates, lipids, proteins, vitamins, minerals, water
Digestive System 4 processes Ingestion – taking in of food Digestion – breakdown of food into small components Absorption – cells soak up digested material Egestion – elimination of waste from the body
Digestive System - Structure
MOUTH Structure Function Teeth, tongue, salivary glands, saliva Teeth and tongue mechanically break down food Salivary glands secrete enzymes that break apart the food. Saliva softens food
ESOPHOGUS Structure Function Muscular tube connecting mouth to stomach Smooth muscle tissue contracts/relaxes to move food slowly along Peristalsis – Rhythmic contractions independent of gravity
STOMACH Structure Function Muscular bag that can stretch 3 muscle layers Muscle layers contract and mix food with gastric juices (HCl, mucous)
SMALL INTESTINE Structure Function 7m long, 2.5cm wide Duodenum, jejunum, ileum Folded to increase surface area Digestion of food is completed here Nutrients are absorbed into the blood stream
LARGE INTESTINE Structure Function 1.5m long, 8cm wide The lining absorbs water from any indigestible food Solid matter excreted as feces from anus
RECTUM Structure Function 12 cm long Begins at end of sigmoid colon temporary storage for feces When urge to defecate, rectum shortens and expels feces If urge is ignored, feces moves back up colon where more water is absorbed and constipation occurs
ANUS Structure Function External opening of the rectum Comprised of 2 sphincters Inner sphincter is involuntary Outer sphincter is voluntary Control the exit of feces during defecation
ACCESSORY ORGANS Liver Gallbladder Pancreas produce/ release chemicals that aid in the breakdown of food
Homework P 82 # 3-5 Digestive CROSSWORD Digestive System WKST