Small Intestine

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Periodontal/Gum Disease

• Periodontal/gum diseases are serious infections
  that, left untreated, can lead to tooth loss
• The word periodontal literally means "around the
  tooth
• Periodontal disease is a chronic bacterial
  infection that affects the gums and bones
  supporting the teeth
• Periodontal disease can affect one tooth or many
  teeth. It begins when the bacteria in plaque
  causes the gums to become inflamed

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Do you have gum disease???

• Do you ever have pain in your mouth?
• Do your gums ever bleed when you brush your teeth
  or when you eat hard food?
• Have you noticed any spaces developing between
  your teeth?
• Do your gums ever feel swollen or tender?
• Have you noticed that your gums are receding
  (pulling back from your teeth) or your teeth
  appear longer than before?
• Do you have persistent bad breath?
• Have you noticed pus between your teeth and gums?
  
• Have you noticed any change in the way your teeth
  fit together when you bite?
• Do you ever develop sores in your mouth?

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How to look after your teeth
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How to Brush
Place your toothbrush next to the teeth so that
it rests on the gums forming a 45-degree angle
against the gums.
Move the toothbrush from the gums towards the
edge of teeth to move the dental plaque away from
the gum line.
After brushing, one by one tooth, all the outer
teeth surfaces do the same for the inner
surfaces. 
Brush the chewing surfaces of the teeth with
horizontal moves.
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How to Floss
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Human Torso Model
Please refer to your handout of the human
digestive system
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Human Digestive System

• Alimentary Canal Associated Glands

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Alimentary Canal and Associated Glands

• Mouth
• Pharynx
• Oesophagus
• Stomach
• Small Intestine
• Large Intestine
• Anus

• Salivary Glands
• Gastric Glands
• Pancreas
• Liver
• Intestinal Glands

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Digestion
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Digestion

• Digestion is the process of breaking down large,
  complex substances into smaller, simpler
  molecules for absorption
• Carbohydrates -gt glucose/fructose/galactose
• Proteins -gt amino acids
• Fats -gt fatty acids and glycerol
• Vitamins, minerals and water can be absorbed
  directly without digestion

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Mechanical Digestion vs. Chemical Digestion

• Mechanical process
• Chewing of teeth
• Churning of stomach
• Food is changed physically but
  not chemically
• Increase surface area of food substances

• Chemical process
• Involves action of digestive enzymes secreted
  from glands
• Different types of enzymes break down different
  food types

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Protease
Breaks down protein molecules
A protein molecule is made of many different
amino acids
Amino acids
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Carbohydrase
Breaks down carbohydrate molecules
A starch molecule is made of many glucose
molecules
Glucose
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Lipase
Breaks down fat molecules
Fatty acids
A fat molecule is made up of fatty acids and
glycerol molecules
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Example of Carbohydrase Amylase

• In saliva and pancreatic juice
• Helps break down starch into simple sugars in
  mouth and in small intestine

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Example of Protease Pepsin

• In gastric juice
• Helps break down proteins into amino acids in
  stomach

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Example Lipase

• In pancreatic juice
• Helps break down oil droplets into fatty acids
  and glycerol in small intestine

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Saliva

• The taste, smell and sight of food can stimulate
  salivary glands to secrete saliva into the mouth
  via salivary ducts
• Saliva contains water, mucus and salivary
  amylase. Slightly alkaline
• Water moistens and softens food
• Mucus lubricate food for swallowing
• Salivary amylase starch -gt maltose

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Swallowing

1. Food is chewed and mixed with saliva
2. Tongue rolls the food into a bolus
3. Food is swallowed down the oesophagus through
   the pharynx
4. Tongue moves upwards and backwards to prevent
   food from entering the trachea/nasal cavity
5. The soft palate moves up to block the nasal
   cavity
6. The larynx moves upwards to so that the glottis
   (the opening to the larynx) is covered by the
   epiglottis to prevent food from entering the
   trachea

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Movement of Food Along the Alimentary Canal

• Inner surface of alimentary canal is lined with
  one to several layers of cells epithelium
• Some epithelial cells produce mucus, which acts
  as a lubricant

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Peristalsis
The small intestine has two muscle layers that
work together in peristalsis and segmentation
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Peristalsis
The inner circular muscles contract, tightening
the tube and pushing the food forward in the
intestine
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Peristalsis
When the circular muscles relax, the outer
longitudinal muscles contract, and the intestinal
tube is shortened
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Peristalsis
As the circular and longitudinal muscles tighten
and relax, the food moves forward
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Stomach

• a muscular, elastic, pear-shaped bag, lying
  crosswise in the abdominal cavity
• food enters the stomach from the esophagus. The
  connection between the stomach and the esophagus
  is called the cardiac sphincter
• The other end of the stomach empties into the
  duodenum, the first section of the small
  intestine. The pyloric sphincter separates the
  stomach from the duodenum

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Sphincter Opened
Sphincter Closed
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Functions of Stomach

• Storage
• Mechanical digestion turns food into chyme
• Chemical digestion

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• The lining of the stomach contains deep
  collections of cells organized into gastric
  glands
• The openings of the gastric glands into the
  surface of the stomach are called gastric pits
• The mucous cells in the gastric pits secrete
  mucus
• In the deeper part of the gland, the parietal
  cells secrete hydrochloric acid
• The chief cells secrete pepsinogen (an inactive
  form of the protein-digesting enzyme pepsin)

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Rennin

• In young children, the gastric juice also
  contains a type of protease called rennin
• Rennin coagulates milk allow the proteins to
  stay in stomach longer for digestion
• Rennin can be used to curdle milk to make
  cheese!

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Ulcer/Peptic Ulcer

• A small erosion in the gastrointestinal tract
• A weakening of the mucus coating acid erodes
  the wall of the GI tract
• Stomach gastric ulcer
• Small intestine duodenal ulcer
• Main cause bacterial infection
• Can be treated with antibiotics

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Small Intestine

• The small intestine is divided into 3
  sections
• Duodenum
• Jejunum
• Ileum
• In the small intestine, both digestion and
  absorption occur

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Bile

• Bile is a dark green fluid containing
• 1) bile salts
• 2) sodium hydrogen carbonate
• 3) bile pigments
• Bile does NOT contain digestive enzymes
• Made by the liver
• Stored in the gall bladder

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• The gall bladder contracts to release bile into
  the duodenum via the bile duct
• Stimulated by the arrival of chyme in the duodenum

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Bile

• 1) Bile salts EMULSIFICATION
• Bile salts break up (emulsify) lipids into small
  oil droplets
• This allows enzymes to have a larger surface area
  to break down the fat molecules
• Lipids
  Small oil droplets
• Bile salts (emulsification)

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Bile

• 2) Sodium Hydrogen Carbonate NEUTRALIZATION
• It neutralizes stomach acid to provide the
  necessary alkaline condition (pH 8) for the
  pancreatic and intestinal enzymes to work

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The pH Scale
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The Need for Different pH Levels

• The stomach releases hydrochloric acid to provide
  an acidic condition (pH1 - 2) for stomach
  proteases (e.g. pepsin) to work. Acid also kills
  germs
• The activity of salivary amylase is stopped in
  the stomach since it cannot work in acidic
  conditions. Pancreatic amylase also requires an
  alkaline condition to work

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The Need for Different pH Levels

• 3) The gall bladder releases bile into the
  small intestine to provide an alkaline condition
  (pH 8) for the pancreatic and intestinal enzymes
  to work

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Bile

• 3) Bile pigments
• Waste products formed from the breakdown of old
  red blood cells in the liver

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Investigation 1 Investigating the
effect of bile
salts on oil
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Pancreas

• A yellowish organ found beneath the stomach and
  is connected to the small intestine at the
  duodenum
• Produces pancreatic juice that flows into the
  duodenum through the pancreatic duct

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Pancreas

• Pancreatic juice contains 3 types of digestive
  
• enzymes
• Tryptase
• Amylase
• Lipase
• Pancreas also produces the hormones
  glucagon
• and insulin to regulate the level of blood
  glucose

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Intestinal Juice

• Alkaline solution containing digestive enzymes,
  hormones, mucus, neutralizing substances, etc.
• Secreted by intestinal glands in the wall of the
  duodenum
• e.g. carbohydrases catalyze the breakdown of
  double sugars into simple sugars

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Carbohydrase

• Maltase Maltose -gt Glucose Glucose
• 2) Sucrase Sucrose -gt Glucose Fructose
• 3) Lactase Lactose -gt Glucose Galactose

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Lactose Intolerance

• Inability to digest significant amount of
  lactose, the predominant sugar of milk, due to a
  shortage of the enzyme lactase
• Common symptoms include nausea, cramps, bloating,
  gas, and diarrhoea
• The undigested lactose will serve as food for
  bacteria found in the large intestine

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Digestion in Ileum

• Completion of digestion
• Food is churned by peristaltic movement and is
  mixed with digestive juices
• Food becomes watery fluid called chyle
• Food is now present in simplest form

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Absorption
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Absorption

• Absorption is the uptake of simple and small food
  molecules from the alimentary canal into the
  blood stream
• Food molecules can be absorbed into blood by
  diffusion or active transport
• Absorption occurs in the stomach, the small
  intestine and the large intestine

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Absorption in Stomach

• Food substances that are absorbed in the
• stomach
• Water
• Minerals
• Alcohol
• Simple sugars
• Water-soluble vitamins

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Absorption in Small Intestine

• Most of the digested food is absorbed in the
  small intestine
• The inner lining of the small intestine is folded
  to provide a large surface area
• The inner surface of the small intestine is made
  up of a large number of finger-like projections
  called villi (singular villus)
• Peristalsis in the small intestine allows the
  digested food to come into contact with the villi
  for absorption

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Structure of Villi

• Epithelium lining
• Blood capillaries (transportation of simple
  sugars, amino acids and minerals)
• Lacteal (lymph vessel)

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Lacteal

• fatty acids and glycerol recombine in the
  epithelium of the villus to form fat which then
  enters the lacteal as fine fat droplets
• the lymphatic system converges with the
  circulatory system at a duct located in the neck
  area

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Absorption in Large Intestine

• Much of the remaining water and minerals is
  absorbed in the colon
• The appendix, which has no known functions, is
  joined to the caecum
• Appendicitis food materials trapped in the
  appendix causing bacterial infection

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Caecum in Herbivores

• Do not have digestive enzymes to break down
  cellulose
• Rely on bacteria residing in the long caecum to
  provide the enzyme cellulase
• Cellulose -gt Glucose

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Investigation 2 A Model Gut
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• What does the content inside the dialysis tubing
  represent?
• What does the dialysis tubing represent?
• What does the water in the beaker/boiling tube
  represent?

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Assimilation
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Assimilation

• the process by which absorbed food molecules in
  the blood are transported to cells for the use of
  growth, tissue repair and other metabolic
  activities. The actual destiny of each food
  molecule depends not only on its type but also on
  the body requirements at that time (e.g. use
  immediately or put into storage)

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Liver

• Largest organ of the body
• Reddish brown in color
• Lies on the right side of the abdominal cavity
  beneath the diaphragm
• Blood is carried to the liver via two large
  vessels called the hepatic artery and the hepatic
  portal vein
• After processing in the liver, blood leaves the
  liver through the hepatic vein

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Functions of Liver

• Carbohydrate metabolism - the liver converts
  excess glucose into glycogen as a temporary way
  of storing the glucose. Glycogen can also be
  converted back to glucose when needed
• Fat metabolism - the liver converts excess
  protein and carbohydrate into fat. Excess
  glycogen is stored as fat for long term storage
  

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Functions of Liver

• 3) Protein metabolism the liver can synthesize
  new proteins/ amino acids and deaminate excess
  amino acids

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Deamination

• Amino group (NH2) removed
• Ammonia (NH3) produced (toxic)
• Ammonia converted to urea excreted in urine
• Carbon skeleton converted to carbohydrates

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Functions of Liver

• 3) Protein metabolism the liver can synthesize
  new proteins/amino acids and deaminate excess
  amino acids
• 4) Vitamin storage - the liver stores mainly
  vitamins A, D and B12
• 5) Iron storage - the liver stores iron which is
  obtained from the breakdown of red blood cells.
  The iron salts can be used in the formation of
  new RBC

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Functions of Liver

• 6) Bile production emulsification and
  neutralization
• 7) Drug/Alcohol metabolism the liver changes
  the drug into an excretable and harmless form
  (detoxification)
• 8) Disposal of bacteria - The liver filters many
  bacteria, viruses, and other microorganisms from
  the blood

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Egestion
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Egestion

• Faeces semi-solid, greenish brown mass
  containing undigested and unabsorbed food
  substances. Also contains bile pigment (hence
  the color of faeces), dead RBC, cells from
  intestinal wall, bacteria, etc.
• Temporarily stored in rectum
• Anal sphincter relaxes to allow a person to
  defaecate

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Constipation and Diarrhoea

• Peristalsis too slow
• Too much water absorbed
• Some common causes include lack of fibre in diet,
  not enough liquids, lack of exercise, etc.
• Lead to dry, hard faeces
• Difficulty in defaecation
• May damage wall of rectum and cause bleeding or
  form piles

• Peristalsis too fast
• Too little water absorbed
• Some common causes include bacterial / viral /
  parasitic infections, food intolerance, etc.
• Lead to loose, watery stools
• More frequent egestion
• May cause dehydration

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Haemorrhoids

• Also referred to as piles
• Haemorrhoids are enlarged veins just under the
  surface tissue of the rectum or the anus
• Haemorrhoids in the rectum are called internal
  haemorrhoids those that occur around the anus
  are called external haemorrhoids
• May cause bleeding, pain, itching and a sense of
  pressure

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Haemorrhoids

• Increased pressure in the veins around the
  anus is thought to be the cause of haemorrhoids
• straining to pass a bowel motion because of hard,
  dry stools (as in constipation)
• diarrhoea
• heavy lifting
• being very overweight
• sitting or standing for long periods
• pregnancy

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