Digestive System

• Main Groups of the Digestive Groups 


  the organs of the digestive system r split into 2 main groups

  = those of the alimentary canal + the accessory digestive organs
• Alimentary Canal


  the alimentary canal/GI tract = contionus muscular tube that winds thru the body from the mouth to the anus

  it digests food - breaks it into smaller fragments - + absorbsthe digested gragments thru its lining into the blood
• Organs of the Alimentary Canal

  mouth

  pharynx

  oesophagus

  stomach

  small intestine

  large intestine

  
• Accessory Digestive Organs & Glands

  teeth

  tongue

  gallbladder

  glands - salivary, liver + pancreas
• Major Processes During Digestion - Ingestion

  ingestion = taking food into the digestive tract by eating
• Propulsion


  propulsion moves food thru the tract

  inc swallowing, which is initated voluntarily, + peristalsis
• Peristalsis


  peristalsis = major means of propulsion

  involves alternating waves of contraction + relaxation of muscles in the organ walls

  main effect = squeeze food along the tract, but some mixing also occurs

  
• Mechanical Breakdown


  mechanical breakdown increases SA of ingested food, physically prepping it for digestion by enzymes

  inc chewing, mixing food w saliva by the tongue, churning food in stomach + segmentation
• Segmentation

  rhythmic local constrictions of the small inestine

  nonadjacent segments of the canal organs contract + relax

  food is moved forward, then backward

  primarily mixes food + breaks it down mechanically

  some propulsion may occur

  mixes food w digestive juices + makes absorption more efficient by repeatedly moving diff parts of the food mass over the intestinal wall
• Digestion


  digestion involves a series of steps in which enzymes secreted into the lumen of the canal break down complex food mols to their chemical building blocks

  = catabolic process
• Absorption


  absorption = passage of digested end products (plus vitamins, minerals + water) from the lumen of the GI tract

  thru the mucosal cells by active/passive transport into the blood/lymph
• Defecation


  defecation eliminates indigestible substances from the body via the anus in the form of feces