Digestive systems

• What are the three types of digestive system?

  -Monogastric

  -ruminant

  -hind gut fermenter
• Examples of animals with monogastric digestive systems are pigs, dogs, cats and humans.
• Examples of animals with ruminant digestive systems Are cows, sheep, goats and deers.
• Examples of animals with a hind gut fermenter digestive systems are rabbits, horses, rhinos and rodents.
• Monogastric digestive systems

  • one chambered stomach
  • digests animal and plant material
  • short system
  • no regurgitation
  • recreated enzymes to digest proteins
• What are the components of the digestve system?


  Mouth

  oesophagus

  stomach

  small intestine

  large intestine

  pancreas

  gall bladder

  salivary glands
• oral cavity (mouth)

  • where digestion begins
  • breaks down food using mechanical digestion
  • enzymes begin to chemically digest (amylase for starch and lipase for fats)
• Dentition (teeth)

  • incisor (front of mouth to bite into food)
  • canine (either side of incisors for tearing and ripping food)
  • premolar (behind canines for tearing and grinding food)
  • molars (back teeth for chewing and grinding food)
• Oesophagus

  • food passes through from pharynx to stomach (aided by peristalsis)
  • behind trachea and heart
  • emptied into top of stomach
  • When swallowing the epiglottis tilts backwards to prevent food going through the larynx into the lungs
• Stomach

  • muscular organ used for digestion
  • stores food
  • extremely acidic (pH between 1.5-2.5) to help enzymes with digestion
  • gastric juices continue digestion process
  • leads to small intestine
• Small intestine

  • breaks down food further
  • enzymes produced by the liver, small intestine and pancreas for chemical digestion
  • nutrients absorbed into bloodstream across epithelial cells (they line the wall of the small intestine)
  • divided into three sections
• duodenum (first part of the small intestine)

  • recieves gastric chyme from stomach
  • first third of the small intestine
• Jejunum (second part of the small intestine)

  • contains circular folds and intestinal villi increasing surface area
  • second third Of the small intestine
• lleum (third part of the small intestine)

  • contains villi to increase surface area
  • final third of the small intestine
• Large intestine

  • waste material travels to large intestine where water is absorbed
  • split into three sections
  • stores faeces until removed
  • houses good bacteria and digests remaining nutrients
• Caecum (first part of the large intestine)

  • connects small and large intestine to the colon
  • absorbs fluids and salts
• Colon (second part of the large intestine)

  • absorbs water and minerals
  • formation of faeces
• Rectum (third part of the large intestine)

  • temporary storage of faecal matter
• hind gut fermenter digestive system

  • found in monogastric herbivores (still a single chambered stomach)
  • cellulose is digested with the aid of symbiotic bacteria
  • microbial fermentation
  • can digest somethings that humans cant
  • reduces the chance of bacteria multiplying
• cecum

  • pouch connected to the large intestine
  • herbivores have this greatly enlarged
  • storage organ for bacteria and microbes for cellulose digestion
• ruminant digestive system

  • multi-chambered complex stomach
  • herbivores
  • digests plant materials
  • lacks enzymes to digest proteins
  • regurgitation during digestion
  • four chambers to the stomach
• what are the four chambers of the stomach in ruminants?


  - rumen

  - reticulorumen

  - omasum

  - abomasum
• dentition

  • molars crush and grind plant material in ruminants
  • saliva aids chewing and swallowing and contains enzymes to break down fat and starch
  • ruminants use tongue to grab food
• reticulorumen

  • ruminants swallow feed without chewing
  • oesophagus functions bi-directly allowing for regurigation for further chewing
  • usually the rumen and retiuclorumen are classed as one organ because of their similar functions and because they're only separated by a thin muscular wall
• rumen

  • lined with papillae for nutrient absorption
  • divided by muscular pillars into dorsal, ventral, caudodorsal and caudoventral sacs
  • 50-60% of starch +soluable sugar consumed is digested in the rumen
  • microorganisms digest cellulose, (complex) starch, sythnthesise proteins and synthesise vitamins B and K
• reticulum

  • collects smaller particles + moves them to the omasum
  • larger particles remain in the rumen for digestion
  • solid portion of the cud slowly moves into the rumen and remains there for 48 hours, where it forms into a dense mat
• omasum

  • has many folds increasing surface area to absorb nutrients
  • water absorption occuring
  • pumps food to abomasum
  • cattle have highly developed + large omasum
• abomasum

  • a secretory stomach - walls produce emzymes + hydrochloric acid
  • hydrolyse proteins in food ready for absorption in the small intestine once hydrochloric acid breaks down
  • almost constant flow compared to monogastrics
• liver

  • produces bile
  • fats aren't water soluble to stop it form clumping the body uses emulsifier (bile salts)
• role of microbial organisms in fermentation

  • large epithelial cells found in the intestines don't produce enzymes but have lots of bacteria
  • cellulose is common in animal diets but no mammalian cells produce enzymes to specifically break it down
  • many bacteria species synthesise cellulases + digest cellulose producing short-chain fatty acids and gas
  • fermentation happens in foreguts of ruminants