Presentation on theme: "The Digestive System The organs of the digestive system can be separated into two groups The alimentary canal or gastrointestinal tract – perform all."— Presentation transcript:
1 The Digestive SystemThe organs of the digestive system can be separated into two groupsThe alimentary canal or gastrointestinal tract – perform all the functions of digestion as the long, coiled, hallow, muscular tube winds through the bodyAccessory digestive organs – assist the digestive process
3 Mouth Also known as the oral cavity This is where food enters the body. As it enters the body it is mixed with saliva and masticated (chewed)It is a mucous membrane lined cavityIt is protected by the lipsThe cheeks form the sides of the mouth, the hard palate forms the anterior roof, and the soft palate forms the posterior roofThe floor of the mouth is occupied by the muscular tongueAt the anterior portion of the mouth are the paired palatine tonsils (sides) and lingual tonsil (base)
4 Pharynx Subdivided into three parts Nasopharynx – the section that part if the respiratory systemOropharynx – posterior to the oral cavityLaryngopharnyx – part that connects to the esophagusThis area helps to propel food, which is also known as peristalsis
5 Esophagus Also known as the gullet Runs from the pharynx, through the diaphragm, and to the stomachIt is essentially a passageway for peristalsisIt is composed of the same four basic layers of all the other organs from the esophagus to the large intestine
6 The Four LayersMucosa – the moist, innermost layer that lines the cavitySubmucosa – a soft connective tissue layer just below the mucosa that contains blood vessels, nerve endings, and lymphatic vesselsMuscularis externa – the smooth muscle layer which is made up of a circular inner layer and longitudinal outer layerSerosa – the outermost wall
7 StomachC-shaped organ on the left side of the abdominal cavity that is hidden by the liver and diaphragmThe stomach acts as a temporary storage tank for food as well as a site for food breakdownThe stomach has an additional muscle layer so that it can move and churn its contentsIt also has various cells that produce digestive enzymes and gastric juice to break down the food as well as mucous producing cells to protect the stomach.The processed food is called chyme as it leaves the stomach and heads for the small intestine.
8 Small Intestine It is the main digestive and food absorption organ It is the longest part (8-18 feet) of the alimentary canal and is a long twisted passagewayIt is composed of three areas called the duodenum, jejunum, and ileumWalls of the small intestine have microvilli, villi and circular folds to help increase the surface area and therefore increase absorption
9 Large IntestineLarger in diameter, but shorter in length than the small intestineIts main purpose is to dry out the indigestible food residue by absorbing water and to eliminate this residue from the body as feces through the anus
11 Salivary glands Produce saliva – a mixture of mucus and serous fluids Saliva moistens and binds food together into a mass called a bolusAmylase in the serous fluid begins the digestive process by breaking down the starch in food
12 TeethHelps process food by breaking the food down into smaller pieces while helping the food mix with the salivaNormally an adult will have 32 teeth
13 PancreasA soft, pink, triangular gland that extends across the abdomen from the spleen to the duodenumProduces a multitude of enzymes that chemically break down foodThe enzyme secretions form the pancreas enter the small intestine at the duodenum
14 Liver Largest gland of the body Its function in digestion is bile production, which emulsifies fatsThis means the large fat molecules are separated into smaller molecules. This increases the surface area and gives fat digesting enzymes more places where they can work.
15 Gallbladder Small, thin-walled green sac Stores bile while digestion is not occurringWhile being stored, the bile is concentrated by removing waterIf bile is stored too long or too much water is removed, the cholesterol it contains may crystallize forming gallstones.
16 Functions of the Digestive System Ingestion – the voluntary act of putting food in the mouthPropulsion – movement of materials through the digestive system by peristalsisFood Breakdown by Mechanical Digestion – physically fragmenting the materialsFood Breakdown by Chemical Digestion – chemically fragmenting the materialsAbsorption – moving usable digested food into the bodyDefecation - moving unusable digested food out of the body