THE DIGESTIVE SYSTEM J.KEMP TPJ3M

THE DIGESTIVE SYSTEM The digestive system breaks down food: 1. physically 2. chemically so it can be absorbed for use by the cells.  The system also eliminates solid waste from the body.

THE DIGESTIVE SYSTEM The digestive system is made up of the: 1. Alimentary canal 2. Accessory organs ALIMENTARY CANAL The alimentary canal is a long tube (about 30 feet stretched out end to end) that extends from the mouth to the anus.  It digests food by breaking it down into smaller fragments and absorbs the fragments into the bloodstream  Food is moved along the digestive system by peristalsis (involuntary muscle contractions)

THE DIGESTIVE SYSTEM The components of the alimentary canal are the:  Mouth  Pharynx  Esophagus  Stomach  Small intestine  Large intestine

THE DIGESTIVE SYSTEM THE MOUTH  Food enters the digestive tract through the mouth  It is then mixed with saliva and chewed  The tongue continuously mixes the food with saliva and initiates swallowing

THE DIGESTIVE SYSTEM THE PHARYNX  From the mouth, the food passes into the pharynx  The pharynx has 2 muscular layers that contract and propel food into the esophagus. THE ESOPHAGUS  Runs from the pharynx through the diaphragm to the stomach.  It is a passageway to the stomach

THE DIGESTIVE SYSTEM THE STOMACH  The C shaped stomach is on the left side of the abd. cavity, hidden by the liver and diaphragm.  It is approx 10 inches long but its diameter depends on how much food is in it  When it is full it can hold 4 litres of food.  The stomach acts like a temporary storage container for food and as a site to break food down physically and chemically. Physically, by churning, mixing and turning the food Chemically, by secreting gastric juices  After food is processed it is called chyme  It then enters the small intestine

THE DIGESTIVE SYSTEM THE SMALL INTESTINE  The small intestine is the body’s major digestive organ and is approx. 20 feet long  It has 3 sections: 1. The duodenum – adds more digestive juices, including bile (greenish liquid produced by the liver and stored in the gallbladder) 2. The jejunum – absorption takes place here 3. The Ileum – absorption takes place here  The small intestine is lined with villi. Villi absorb the digested food into the capillaries

THE DIGESTIVE SYSTEM THE LARGE INTESTINE  Larger in diametre but shorter in length (approx 5 feet) than the small intestine  Also called the colon  The large intestine also contains the appendix, rectum, and anus  Its function is to absorb water from undigested food and eliminate feces  The large intestine is subdivided into 4 sections 1. The ascending colon 2. The transverse colon 3. The descending colon 4. The sigmoid colon

THE DIGESTIVE SYSTEM The accessory organs are:  Teeth  Tongue  Salivary glands  Liver  Gallbladder  Pancreas

THE DIGESTIVE SYSTEM  Give the definition and/or function for each of the accessory organs using the textbook.  Use pg’s as well as the texbook’s index  Describe/summarize how food moves through the digestive system

THE DIGESTIVE SYSTEM  Digestion begins at the mouth (receives food and prepares it for digestion).  Using chewing, the teeth cut, chop and grind food for digestion and swallowing.  The tongue helps with chewing and swallowing.  Salivary glands create saliva, which moistens food for easier swallowing and begins to digest food.  During swallowing, the tongue pushes the food to the pharynx (throat).

THE DIGESTIVE SYSTEM  This is a muscular tube and as it contracts, the food is pushed into the esophagus.  The esophagus is another muscular tube which extends from the pharynx to the stomach.  Involuntary muscle contractions called peristalsis moves the food down the esophagus into the stomac h.

THE DIGESTIVE SYSTEM  The stomach is a pouch like sac which stirs and churns food to break it up.  The stomach secretes gastric juices to aid in this process until it becomes chyme (a semiliquid substance).  Via peristalsis, the chyme is pushed from the stomach into the small intestine.  The small intestine is about 6 metres long and has 3 parts. The first part is the duodenum.  When chyme gets to the duodenum, more gastric juices are added. One of these juices is called bile. Bile is a greenish liquid produced by the liver and stored in the gallbladder. Juices from the pancreas are also added to the chyme.

THE DIGESTIVE SYSTEM  All of these digestive juices break down food so it can be absorbed.  Next, peristalsis moves the chyme to the jejunum and the ileum. Tiny villi line the small intestine. They absorb digested food into the capillaries.  Most of absorption takes place in the jejunum and ileum.  Some chyme remains undigested and is absorbed by the colon or large intestine..

THE DIGESTIVE SYSTEM  The remaining semi solid material is called feces.  Feces consists of a small amount of water, solid wastes and some mucus and microorganisms.  Feces passes through the colon into the rectum and finally through the anus.  The process of excreting feces is called defecation.  Feces that has been excreted is called stool