Digestive System

• Digestion


  The process wherein food is broken down into smaller molecules that the body cells can absorb and utilize
• Ingestion


  The process of eating, putting food into the mouth
• Secretion


  The secretions of the different digestive glands (saliva, gastric juice, etc.) that lubricate, soften, and liquefy foods, and contain enzymes that simplify complex food materials
• Digestion of food

  1. Physical/mechanical digestion - breaks down food into small pieces

  2. Chemical digestion - changes the composition of food through enzyme action
• Absorption


  The process that brings the final products of digestion (nutrients) from the small intestine for distribution to all parts of the body via blood and lymph vessels
• Excretion


  The process of removing waste products (undigested residue or feces) from the body through the anus in a process called defecation
• A posterior opening called the anus is where the undigested residue called feces exits.
• The digestive system consists of the organs of the alimentary tract

  • Mouth
  • Pharynx
  • Esophagus
  • Stomach
  • Small intestine
  • Large intestine
  • Rectum
  • Anus
• The mouth (oral cavity or buccal cavity) ingests the food. It is adapted to break down food mechanically and chemically.
• Teeth


  break down food into smaller pieces
• Tongue


  enables us to taste food, mixes the food with the saliva secreted by the ducts of the salivary glands located within the mouth, and helps us swallow the partly digested food.
• Saliva


  contains the salivary amylase, also known as ptyalin, that breaks down carbohydrate-rich foods into their simpler equivalents.
• Bolus


  the food that is chewed and lubricated is changed into a ball-shaped mass
• Swallowing pushes the bolus into the pharynx or throat. It is the common passageway for digestion and respiration.
• During swallowing, the swallow reflex raises the flap of muscles called the epiglottis to cover the opening of the trachea, so food finds its right way, and the passing of air temporarily stops.
• The esophagus is the muscular tube that conveys food from the pharynx to the stomach. A wavelike contraction called peristalsis that begins in the middle portion of this facilitates the movement of the bolus down the different organs.
• The stomach is the pear-shaped organ that is connected to the distal end of the esophagus
• The churning action of the stomach changes the bolus into a semi-fluid consistency called chyme.
• The small intestine is a long, coiled tube that fills the abdomen. It consists of three regions: duodenum, jejunum, and ileum. It is considered the organ of complete digestion and absorption because its intestinal glands secrete the final enzymes for digestion.
• The large intestine, also called the colon, is the organ next to the small intestine. It temporarily stores undigested residue or feces. It is divided into three regions: ascending colon, transverse colon, and descending colon.
• The rectum serves as a warehouse for undigested residue or feces. The end part of the rectum is the anal canal or anus which functions as the exit point for fecal materials.
• The liver is the largest organ in the body. Its function is the secretion of bile which is important in digestion.
• Bile is stored and concentrated in the gallbladder. It has two functions: to neutralize the acidity of the chyme and to change fat-rich foods into an emulsion, a consistency that will facilitate enzyme action.
• The pancreas is the large, elongated, and yellowish gland that lies posterior to the stomach. The part of this consisting of a small, berry-like cluster secrets the digestive enzymes directly into the duodenum. The enzymes are amylopsin, trypsin, and steapsin.
• Name the organs of the digestive system

  A) Mouth

  B) Salivary Glands

  C) Esophagus

  D) Liver

  E) Gallbladder

  F) Stomach

  G) Pancreas

  H) Large Intestine

  I) Small intestine

  J) Rectum

  K) Anus