respiratory system

• 1. Mechanical or Physical digestion- food is converted into small pieces by physical means such as mastication by the teeth
• chemic digestion - food is converted into simpler forms by the action of enzyme
• 1. Intracellular digestion- inside the cell particularly in the lysosomes, characteristic of unicellular organisms
• 1. Intercellular or extracellular digestion- outside the cell; inside the digestive tube; accomplished through secretions from the digestive glands and with the aid of accessory parts such as the teeth and tongue.
• 2 types of digestion

  as to action and as to location
• 2 types of action digestion

  mechanical and chemical
• 2 types of as to location digestion

  intercellular and intracellular
• DIGESTIVE TUBE

  • Also called as alimentary canal;
  • Over 30 ft long in human, beginning in the mouth and ending in the anus
• Mouth

  • Anterior opening of the digestive tube
  • Guarded by upper and lower lips
  • For ingestion of food
• oral cavity


  site of mastication and lubrication of food
• accessories function of oral cavity

  oral glands, tongue and teeth
• Oral glands- not located in the oral cavity but their ducts open into itsecretes mucus for lubrication of food saliva which contains enzyme used in digestion
• tongue

  • muscular organ for catching prey in frogs as thermoreceptor and chemoreceptor in snakesfor tasting, manipulation of food, and aid in swallowing in human
• teeth

  • und in anterior and lateral sides of oral cavityused for offense and defense-used for mastication of food
• 1. External parts of tooth a. crown- exposed part b. root- hidden part c. neck- between the crown and the root, internal parts of tooth
• namel- outermost and hardest part
• . dentine- slightly elastic, softer part beneath theenamel
• cementum- thin layer of material covering the root
• canines- round pointed teeth at the corners of the mouth, for tearing and gripping the food
• Pre-molars and molars- square teeth with small cusps at the back of the mouth, for grinding the food
• Primary teeth - also called as milk teeth; appear 6 to 24 months after birth and gradually will fall out to be replaced by the permanent teeth; consist of 20 teeth (4 incisors, 2 canines, 4 molars)
• Permanent teeth - appear from the age of 6 and completed by the age of 13;"wisdom tooth" appear as late as 25 consist of 32 teeth (4 incisors, 2 canines, 10 molars)
• 2 types of as appearance of teeth

  primary and permanent
• harynx• Narrow space behind the oral cavity• Common passage of food and air
• Esophagus• Narrow muscular organ between the pharynx and the stomach• Peristalsis (wave-like) movement
• • Stomach
  • The largest and highly muscular part of the digestive tube
  • Suspended by the mesogaster
  • Maximum capacity of 2.5 pint
  • Food stays for about 3-5 hours
  • Churning movement
  • Internally, lined with numerous folds or rugae where gastric glands are located
• parts/ Divisions of the stomach

  Cardiac sphincter, Fundus, Pyloric sphincter
• Cardiac sphincter- anterior end; prevents the backward movement of food to the esophagus
• Fundus- most expanded part of the stomach
• Pyloric sphincter- posterior end; regulates the movement of food to the small intestine
• Small Intestine

  - The longest and most coiled part of the digestive tube

  Site of final digestion and absorption•

  Suspended by the mesentrium•

  About 22 ft long•

  Food stays around 4.5 hours•

  Segmenting movement•

  Internally, lined with numerous folds or villi that increases its surface for absorption
• Parts/ Division of the Small Intestine

  Duodenum, Jejunum, lleum
• Duodenum- si, anterior end;uncoiled, around 12 inches long
• Jejunum- si, middle division; coiled
• lleum- si, posterior end
• Large Intestine• Posterior part of the digestive tube that absorbs water• Joined to the small intestine through the ileocolic junction (vermiform appendix)• Suspended by the mesocolon or mesorectum• Food stays for about 5 to 25 hours or more
• Parts/ Divisions of the Large Intestine

  • Caecum• Colon• Rectum
• Caecum- anterior portion; appendix is located
• Colon- middle portion; divided into ascending colon, transverse colon, descending colon and sigmoid colon
• Rectum- posterior portion; temporary storage of undigested food