Animal Physiology by sW5qEPE

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									Animal Physiology

 Mammalian Nutrition
               Composition of Food
Humans are adapted for feeding and
 digestion so that food molecules can
 reach the body cells.
The main groups of food we eat are:
     Carbohydrates
     Fats
     Proteins
     Vitamins
     Minerals
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               Composition of Food
Carbohydrates contain the elements
 carbon, hydrogen & oxygen
Fats contain the elements carbon,
 hydrogen & oxygen
Proteins contain the elements carbon,
 hydrogen, oxygen & nitrogen



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                        Carbohydrates
Carbohydrates provide us with energy
 for our normal activities.
They consist of long chains of glucose
 molecules.


                                             Glucose


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                            Fats
 Fats release some energy
  for our use if required
  while the rest is stored in
  adipose tissue beneath the                            Fatty acid




                                             Glycerol
  skin.
                                                        Fatty acid
 This is used as insulation.
 Each fat is made up of a                              Fatty acid
  glycerol molecule joined to
  3 fatty acid molecules.

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                            Proteins
Our body requires protein to build it up
 and for growth and repairing damaged
 tissue.
Proteins are built up from long chains of
 amino acids.
There are only about 20 different amino
 acids.
   Amino acid


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                            Vitamins
Vitamins are required for good health.
They do not provide energy.
They act as coenzymes which are
 required in the various biochemical
 activities within cells.
Some examples of vitamins, their source
 and the deficiency disease are given in
 the table.
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                              Vitamins
   Vitamin                   Source          Deficiency Disease
         A     Milk, fresh veg.                     Night Blindness
 B1 (Thiamine)  Cereal grains                          Beri beri
 B3 (Niacin)     Cereal, lean                          Pellagra
                     meat
  C (Ascorbic   Citrus fruits                           Scurvy
       acid)
         D              Liver, fish, milk               Rickets
         E                  Wheat germ                Reproductive
                                                       Disorders
         K                  Green veg.             Blood doesn’t clot
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                            Minerals
Minerals are chemical elements which
 are required in very small quantities.
They have a whole variety of functions,
 some of which are shown in the
 following table.




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                               Minerals

 Mineral                           Required For:
     Iron                   Haemoglobin in Red Blood Cells
   Iodine                              Thyroxine
   Sodium                                All cells
  Calcium                      Healthy teeth & bones
Potassium                      Contraction of muscles


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                     Alimentary Canal
 The food we eat passes from the mouth to
  the anus through the “alimentary canal” or
  gut.
 As food passes through this canal it is
  processed in a number of ways and by a
  number of organs.
 Other organs, such as the salivary glands,
  liver and gall bladder are attached to the
  alimentary canal by ducts, and these are
  called associated organs.

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                     Alimentary Canal
                   Mouth                    Salivary gland


          Oesophagus

              Liver                             Stomach


        Gall bladder                            Pancreas

   Large intestine                              Small intestine


                Anus                            Rectum


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                            The Mouth
The food is physically broken down into
 manageable sizes by the teeth.
It is mixed with a fluid called saliva,
 which contains the enzyme salivary
 amylase, to digest starch.




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                            The Mouth
Saliva also contains mucus which makes
 the food easier to swallow.
The food is then moved through the
 gullet (oesophagus) to the stomach by a
 process called peristalsis.




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                              Peristalsis

Muscles
contract                                            Food
  here                                            moves this
                                                     way


                                                    Muscles
                                                     relax
                                                     here



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                            Stomach
The stomach is a muscular bag with a
 valve at either end.
The CARDIAC sphincter at the top
 allows food in.
The PYLORIC sphincter at the bottom
 allows food to leave.



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                            Stomach
The stomach wall produces digestive
 juices from gastric glands which
 secrete mucus, acid and enzymes.
For digestion to work properly the food
 must be well mixed with these juices.
The stomach muscles contract and relax
 to mix up the juices and food.


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Mucus and                    Gastric Gland
gastric juices
secreted into
the stomach
                                    Mucus-secreting cell


                                    Acid-secreting cell


                                    Enzyme-secreting cell



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                        Gastric Glands
The mucus-secreting cells release a
 slimy mucus which sticks to the wall of
 the stomach and protects it from
 damage by the strong digestive
 enzymes.




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                        Gastric Glands
The acid-secreting cells release
 hydrochloric acid which has 2
 functions:
     It creates conditions needed to produce
      active pepsin.
     It provides the optimum pH for the
      enzymes to work.



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                        Gastric Glands
The enzyme-secreting cells release an
 inactive enzyme called pepsinogen.
Once the pepsinogen comes in contact
 with the acid, it is converted to an
 active enzyme called pepsin.
The pepsin can now break down proteins
 in the stomach to peptides, which will
 later be broken down further into amino
 acids.
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                            Stomach
The longitudinal muscles contract to
 make the stomach shorter and fatter.
The circular muscles contract to
 squeeze the stomach.
Once the food has been in the stomach
 for a while, it is released slowly, small
 drops at a time into the small intestine.


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                       Small Intestine
The food enters the small intestine
 from the stomach and is moved along by
 peristalsis.
A number of digestive enzymes break
 down the large insoluble food molecules
 to small soluble food molecules before
 they are absorbed out of the intestine.


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                       Small Intestine
 The small intestine’s function is to absorb
  soluble food molecules and it is well suited to
  this job in a number of ways.
     It is very long (About 6m). The inner surface is
      folded into thousands of finger-like villi.
     The lining of each villus is very thin. (Only one cell
      thick)
     Each villus has a network of vessels for absorbing
      the food, both blood capillaries and lymphatic
      vessels. (Lacteals)

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                            A Villus

        Thin wall

                                              Blood capillary

       Lacteal




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                            Absorption
The glucose and the amino acids are
 absorbed into the blood capillaries.
These tiny blood capillaries all join up to
 form the hepatic portal vein and
 transport the absorbed food to the
 liver.



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                            Absorption
The liver stores most of the glucose as
 glycogen until it is required, but some
 glucose remains in the blood.
The amino acids are used in the body
 for growth and repair, but if there are
 any excess amino acids, these are
 broken down by the liver into urea.


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                            Absorption
This is later removed by the kidneys
 and released in the urine.
Vitamins and minerals are transported
 to cells where they have special
 functions which help to keep the body
 healthy.
Any excess vitamins and minerals are
 either stored or excreted.

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                            Absorption
Fats and fatty acids are absorbed by
 the lacteals which contain a fluid called
 lymph.
This lymph is transported in the lymph
 vessels which will eventually drain into
 the blood system.
The products of fat digestion can be
 used for energy, as insulation or simply
 stored until required.
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                      Large Intestine
When the food eventually reaches the
 large intestine (Colon), it is mainly water
 and indigestible waste materials.
The function of the large intestine is to
 absorb water back into the bloodstream
 leaving a semi-solid called faeces.
The faeces is passed into the rectum
 (bowel) where it is stored until it is
 eventually eliminated through the anus.
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