Digestive System 2

• DIGESTIVE SYSTEM

  • Also known as Alimentary Tract and Gastrointestinal Tract
  • A system of organs and glands which are involved in obtaining food, its crushing, digestion, absorption, assimilation, and elimination of indigestible matter
  • The main responsibility of the digestive system is to convert the food that we eat into their simplest forms (Like Glucose, Amino acids, and Fatty acids)
  • The broken-down food is then absorbed into the bloodstream from the small intestine and the nutrients are carried to each cell in the body

  
• Chemical digestion


  enzymes and acids help breakdown the food
• Mechanical digestion


  chewing the food into smaller pieces
• 2 PHASES OF DIGESTION

  Mechanical and Chemical digestion
• The GI Tract (gastrointestinal tract) is the mascular alimentary canal


  • mouth

  • pharynx

  • esophagus

  • stomach

  • small intestine

  • large intestine

  • anus
• The accessory digestive organs supply secretions contributing to the breakdown of food


  • teeth and tongue

  • salivary glands

  • gallbladder

  • liver

  • pancreas
• Digestion - taking in food
• The mouth contains the following structures:

  1. Teeth - break down food into small pieces
  2. Tongue - muscular organ that mixes the food with saliva and aids in swallowing. It contains taste buds that enable us to taste food
  3. Duct of Salivary Glands - secrete saliva that lubricates food
  4. Palate - roof of the mouth; hard palate (made of soft bone), soft palate (made of muscle) and are important for eating and speech sounds
• MOUTH


  • Ingestion and Digestion begins in the mouth or oral cavity.
  • Food is mechanically and chemically digested.
  • Food that enters in this part is lubricated and chewed until it forms into a ball - shaped mass called bolus.

  
• Digestion - break down of large food molecules into smaller molecules
• ESOPHAGUS


  • is a muscular tube through which food passes from the pharynx to the stomach.
  • during swallowing, the bolus is conveyed into the stomach via a wave-like contraction and relaxation of involuntary muscles called peristalsis. It push and transport foods and liquids in small sections to the stomach.

  
• PHARYNX


  • also known as Throat.
  • located posterior of the mouth.
  • about 5 to 6 inch long.
  • common passage way for digestion and respiration.
  • breathing and swallowing don't happen at the same time.
  • during swallowing, the sphincter muscle relaxes and raises the epiglottis to cover the opening of the trachea so food find its right way and the passing of air temporarily stops. The opiglottis prevents bolus from entering the trachea.

  
• Absorption - process of absorbing simple water-soluble fragments into the bloodstream
• SMALL INTESTINE


  • considered as the organ of the complete digestion and absorption.
  • longest organ in the digestive system.
  • Secretes digestive enzymes that change food materials into their simplest components.
  • It has finger - like projections called villi.
  • Each villus contains blood capillaries that enable it to absorb water, glucose, amino acids, vitamins, minerals, and fatty acids.
  • Villi increase the surface area available for the absorption of nutrients
  • divided into three sections:

  
• SMALL INTESTINE

  1. Duodenum - first and shortest part; continuous breaking-down process and resumes chemical digestion uses bile
  2. Jejunum - middle and freely movable portions
  3. lleum - longest and highly coiled part
• Assimilation - the process of carrying absorbed simple molecules to different parts of the body by blood vessels


  • It is the movement of digested food nutrients into the blood vessels of the small intestine through diffusion and use of nutrients into the body cells through the microvilli - microscopic cellular membrane projections that serves to expand the surface area for diffusion and also to lessen any increase in volume.

  
• LARGE INTESTINE

  • Also called as colon.
  • Three functions:

  1. Temporary stores fecal materials
  2. Absorbs vitamins produced by symbiotic bacteria present in the colon
  3. Reabsorbs water from the undigested residue

  • It secretes mucus to aid in the formation of feces and maintains alkaline conditions
  • divided into 5: caecum, ascending colon, transverse colon, descending colon, and sigmoid colon.
  • caecum - a blind sac that bears the vermiform appendix.

  
• Eggestion - release of undigested food
• RECTUM


  • Located at the distal end of sigmoid colon
  • Serves as warehouse for the undigested residue or feces

  
• ANUS


  • Feces is pushed out of the body through the anus by defecation.

  
• ACCESSORY ORGANS


  • described as exocrine glands.
  • it has ducts and openings that secrete chemical substances into the organs of digestion to aid in the digestive process
• SALIVARY GLANDS


  • Located in the mouth
  • Secretes saliva, a chemical substance that is a combination of watery fluid (serous fluid) and mucus.
  • About 1 liter of saliva is secreted by these glands everyday.
  • mucus - lubricates
  • serous - contains salivary amylase, ptyalin (digest carbohydrates)

  
• GALL BLADDER


  • Small sac - shaped organ beneath the liver
  • Stores and concentrates bile from the liver, releases it into the small intestine.

  
• LIVER


  • The largest internal organ in the body
  • Produces bile (emulsification of fats and neutralization of partly digested food (chyme) comes from the stomach)
  • It stores some nutrients, and releases them into the blood according to the activities and needs of the body (homeostasis)

  
• PANCREAS


  • A large, elongated gland located at the back of the stomach
  • It functions as exocrine and endocrine glands
  • Produces digestive enzymes to digest carbohydrates, proteins and fats
  • a gland that makes hormones, digestive enzymes, and insulin, which is a protein that grabs a sugar molecule in the bloodstream and carries it into each cell

  
• DIGESTIVE ENZYMES


  • Mouth

  Salivary Amylase

  • Stomach

  Hydrochloric Acid

  Pepsin

  • Duodenum

  Pancreatic Amylase

  Pancreatic Lipase

  Trypsin

  • Small Intestine

  Lactase

  Maltase

  Sucrase-Isomaltase
• DIGESTIVE ENZYMES

  • Carbohydrates are broken down into sugars by enzymes like amylase. sucrase-isomaltase, maltase, and lactase.
  • Proteins are broken down into amino acids by enzymes like pepsin, trypsin, and peptidase.
  • Fats are broken down into fatty acids by the enzyme lipase.