DIGESTIVE SYSTEM

• • The digestive system is a set of organs which change what we eat into substances that can be used in the body.
  • These substances can be used for energy, growth and repair.
• The alimentary canal is a tube that runs from the mouth to the anus
• MOUTH

  1. Chemical digestion (amylase converts starch to maltose)

  2. Physical digestion (teeth break food down into smaller pieces)
• ESOPHAGUS

  Connects mouth to stomach
• STOMACH

  1.Holds the food for a while

  2.Physical digestion (food is churned and mixed)

  3.Chemical digestion (assisted by HCl)
• LIVER

  Produces bile for the digestion of fats
• GALL BLADDER

  • STORES BILE
• SMALL INTESTINE

  1.Chemical digestion

  2.Absorption of nutrients into blood
• LARGE INTESTINE

  1.Elimination of waste

  2.Absorption of water
• PANCREAS

  Produces digestive juices
• RECTUM

  -STORES FECES
• PHYSICAL DIGESTION

  • This is where large pieces of food are broken down into smaller pieces of the same food
• CHEMICAL DIGESTION

  This is where food is broken down into a different substance that can easily pass into the blood
• Saliva is excreted by three pairs of glands:

  • The parotid gland (below the ear)
  • The submandibular (under the tongue)
  • The sublingual (under the tongue)
• • The ball of food that leaves the mouth is known as a bolus.
• 5 TASTES

  • UMAMI
  • SALTY
  • SWEET
  • BITTER
  • SOUR
• • The epiglottis a small flap of cartilage blocks the entrance to the larynx, this stops the food going down the wrong way and prevents choking.
• ESOPHAGUS

  -Food moves along it by a muscular contraction known as peristalsis.
• • The cardiac sphincter, is a valve that stops back flow of the stomach`s contents
• • Food leaves the stomach through the pyloric sphincter into the duodenum (first part of the small intestine).
• STOMACH

  • It kills bacteria by producing hydrochloric acid.
• §Hydrochloric acid neutralises bacteria and activates pepsin.
• §Rennin is an enzyme that curdles milk protein in infants.
• §Pepsin is an enzyme that breaks down proteins into peptones.
• §It is divided into three parts: SMALL INTESTINE

  ØThe duodenum

  ØThe jejunum

  ØThe ileum
• SEVEN METERS LONG

  SMALL INTESTINE
• SI

  • The inner wall is covered in villi, tiny hair like projections which increase the surface area for absorption.
• Pancreatic juice is secreted into the duodenum and contains the following enzymes:

  Trypsin: converts proteins into shorter chains.

  Lipase: converts fats into fatty acids and glycerol.

  Amylase: converts starch into disaccharides.
• §Bile: emulsifies fats (breaks them into smaller droplets).
• §Intestinal Juices have the following enzymes:

  ØMaltase, sucrase, lactase: change disaccharides into monosaccharides.
• The caecum: a small pouch; the ileum empties its contents into the caecum through the ileo-caecal valve.
• 1.5 METERS LONG

  LARGE INTESTINE
• The colon: ascending, transverse, descending colon
• §Defecation: peristalsis pushes waste along the colon and then it is passed out of the body.
• §An enzyme is a biological catalyst

  §A catalyst speeds up chemical reactions

  §Enzymes speed up biological reactions

  §All chemical reactions that take place in living systems require the action of an enzyme
• Amylase converts starch into a sugar called maltose
• §The substance that an enzyme works on is known as its SUBSTRATE
• §The substance formed by the enzyme is known as its PRODUCT
• FOUR STAGES IN HUMAN NUTRITION

  • INGESTION
  • DIGESTION
  • ABSORPTION
  • ELIMINATION
• TEETH

  §An adult human has 32 teeth, 16 in either jaw