Digestive system
Learning objectives
To outline the digestive system and
metabolism.
To identify the source of energy.
To describe the process of digestion and
absorption of food.
To describe energy conversion.
Learning objectives
To describe the storage of energy.
To define metabolic rate.
To describe energy balance of human body.
To stat the metabolic rate of the liver.
Human’s Nutrition
Ingestion
Digestion
Absorption
Assimilation
Egestion
Ingestion
The process of food intake
 Chewing : Teeth ~ Incisor, canine, premolar
& molar
Tongue
Mouth
 Swallowing
Digestion
Mechanical( mastication & peristalsis) +
Chemical process
 solid food  smaller pieces
 large molecule  smaller molecules
 soluble forms
 simple ones
Processes of digestion
Mouth: teeth, saliva
Food
Oesophagus: peristalsis
Stomach: gastric juice
Digested food
Intestine: intestinal juice
Digestion in Mouth cavity
Mechanical digestion ~ chewing
Chemical digestion
~ salivary amylase ( Starch  maltose)
~ lysozyme ( Pathogenic microbes)
~ Salts ( provide alkaline condition)
~ Mucus ( lubrication)
Swallowing
Digestion in stomach
Mechanical ( peristalsis)
Chemical ( gastric juice)
~ Pepsin (protein  polypeptides)
~ Renin ( coagulate casinogen)
~ HCl activator
kills or inhibit bacterial growth
stimulates gastric secretion
~ Mucus ( lubrication)
Digestion in small intestine I
Duodenum (25cm) + Jejunum(2.5m) + ileum
(3.6m)
 Bile
~ produced by liver
~ contain no enzyme
~ Sodium bicarbonate, bile salts, bile pigments
Digestion in small intestine II
Pancreatic juice
~ produced by pancreas
~ sodium bicarbonate
~ enzymes
amylase
lipase
trysinogen
nuclease
Digestion in small intestine III
 Intestinal juice
~ produced in the intestinal wall
~ alkaline mucus
~ enzymes
maltase amylase
sucrase
peptidase
lactase
Digestion in small intestine IV
Mechanical
~ the chyme is mixed with
intestinal juices by
intestinal movement.
 Peristalsis- rhythmic
contraction & relaxation
of gut wall
 Dividing movement
Absorption
No absorption in mouth
& oesophagus
Absorption of alcohol &
water in stomach
Absorption in small &
large intestine
Adaptation for absorption in
small intestine
Thin surface ~ easier to pass through
Transport vessels ~ current of blood
Great surface area ~ numerous finger-like cilli
& microvilli
Absorption via blood vessels
Amino acids. Monosaccharides, water soluble
vitamins, salts & water
 Carbohydrates
~ galactose >glucose >fructose
~ by active transport
 Amino acids ~ by active transport
 vitamins & mineral
 water ~ by osmosis
Absorption via lacteal
Glycerines, fatty acids &fat soluble vitamins
Absorbed through epithelial cell into the
lymphatic ducts

superior vena cava

Heart

Different parts of body
Absorption in large intestine
Water & mineral salts
 excess water, nutrients & undigested
materials  faeces
Others
 bacteria ~ produces Vitamin B & K as byproducts
Diarrhoea & Constipation
Assimilation of food
Carbohydrate
~ mainly glucose
~ as chief energy source
~ excess glucose
converted into glycogen
& subcutaneous fat
Amino acids
~ synthesis protein
~ excess not stored but
deaminated
~ Amino acid urea+CO2
Fats
~ as energy source
~ as structural substances
~ secreted as oil
~ excess stored as adipose
tissues
Function of liver
Regulation
~ glucose  glycogen
~ amino acid  urea+CO2
~ Fat & oil  glycogen
Production
~ Heat
~Bile
~Cholesterol
~ Red blood cells
Storage
~ blood & vitamins
Elimination of
hemoglobin
Detoxification
Homeostasis
~ blood clotting
Defense
~ phagocyte cells
Pancreas
It is a mixed gland consisting of exocrine and
endocrine tissues;
It is an elongated gland lying in the loop
formed by duodenum and the under surface of
stomach.
Function of pancreas
Exocrine secretion:
~ pancreatic juice ( amylase, maltose, trypsin)
Endocrine secretion
~ insulin: glucose in blood  glycogen in liver;
 blood glucose level
 lacking of insulin: Diabetes mellitus
~ glucagons: glycogen in liver  glucose in blood
  blood glucose level
Balanced diet
It is a diet contains all
the essential nutrients in
the correct proportion
so as to provide enough
energy, mineral salts
and vitamins for
regulation and
protection.
Component of a balanced diet
Carbohydrate (55%)
Lipid (<30%)
Protein (15-20%)
Water
Roughage
Mineral salt and vitamin