Transcript Animal Physiology

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 release some energy
for our use if required
while the rest is stored in
adipose tissue beneath the
skin.
 This is used as insulation.
 Each fat is made up of a
glycerol molecule joined to
3 fatty acid molecules.
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Glycerol
Fats
Fatty acid
Fatty acid
Fatty acid
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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.
B1 (Thiamine)
Cereal grains
B3 (Niacin)
Cereal, lean
meat
C (Ascorbic
Citrus fruits
acid)
D
E
Liver, fish, milk
Wheat germ
K
Green veg.
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Night Blindness
Beri beri
Pellagra
Scurvy
Rickets
Reproductive
Disorders
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
Stomach
Liver
Pancreas
Gall bladder
Large intestine
Small intestine
Rectum
Anus
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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
here
Food
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 juices
secreted into
the stomach
Gastric Gland
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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