POST RN BScN SEMESTER II

1. 1
Year 1
Semester
2 UNIT
IX
Life saving son
Post Rn BScN NIAMAT ULLAH

2. unit ix metabolism of
carbohydrates, FATS, PROTIEN
There are four (4) stages of food processing:
Ingestion (eating): taking in nutrients (important part in
food)
Digestion: using physical and chemical means to break down
Complex organic molecules into smaller usable parts
Absorption: pulling in digested molecules into the cells of the
digestive tract, then into the blood
Egestion: the removal of waste food materials (e.g. cellulose =
fiber) from the body. These four steps are done by the digestive
system. The steps occur in the gastrointestinal tract (a long
tube open at both ends). Accessory glands Such as the liver
and pancreas help during the process. The GI tract is also
called the Alimentary tract.
1. Ingestion: The mouth food enters the gastrointestinal
tract through the mouth.
2. Digestion:
A) Mouth – both physical (mechanical) and chemical digestion
begins here
Physical - Two main structures involved: teeth and tongue
i) TEETH - four types (normal adult has 32 teeth on average).
Tooth type Number Function
a) Incisors 8 cut food
b) Canine 4 pierce and tear food
c) Bicuspids 8 pierce and tear

3. d) Molars 12 crush and grind
ii) Tongue - both tongue and teeth help to physically break
apart food.
Chemical digestion: using enzymes to break up food
In the mouth, Salivary glands produce Saliva which contains
the enzyme amylase which acts on starch, breaking it into
maltose.
STARCH amylase maltose
Bolus: the resulting ball of food in the mouth made by the
actions of the teeth, tongue, and saliva.
PERISTALSIS: the rhythmic muscular contractions that push
digested food in one direction through the gastrointestinal
tract. The bolus is swallowed and travels down the esophagus
into the stomach. It moves down the esophagus by peristalsis.
B. STOMACH: physical and chemical digestion the bolus
passes through the Cardiac Sphincter, the top opening in the
stomach.
Sphincter: a muscle that controls the opening
i) Cardiac: esophagus & stomach
ii) Pyloric: stomach and duodenum
Physical: the stomach is a muscular storage organ that
churns the food
Chemical: Gastric juice mixes with bolus- stomach
contents now called Chyme (Gastric juice contains: a) HCl –
hydrochloric acid
b) Pepsin – enzyme that breaks down protein HCl: - helps
breakdown fibrous tissue - kills bacteria- helps pepsin work
properly (ph = 2 optimal pH for pepsin).
PEPSIN: - enzyme begins to break down PROTEIN into
smaller polypeptides.
MUCUS: - also made by stomach to protect itself from strong
acid, Chyme stays in stomach until adequate protein digestion
has occurred. This is why you feel less hungry between meals

4. if you have eaten some protein. The chyme is kept in the
stomach by the pyloric sphincter.
C. SMALL INTESTINE
A.Final area where most digestion occurs and absorption
begins.
Physical – villi and microvilli help separate food particles
Chemical – where many enzymes complete the digestive
process, many enzymes from accessory glands (liver, gall
bladder, and pancreas) are dumped into the SI to help with
digestion
SMALL INTESTINE – STRUCTURE
The small intestine is a long tube (7 m) in length and 2.5 cm in
diameter with a total inner surface area of 30 m2 (due to the
villi and microvillus).
The SI is also divided into three sections:
a) Duodenum
b) Jejunum
c) Ileum
Duodenum: - first 25 cm portion
- means 12 fingers in Latin (duo = 2, den = 10)
- Pancreas and liver dump enzymes here to help digestion
- most digestion occurs here
- produces intestinal enzymes: maltase maltose
peptidase polypeptides
Chyme leaves the stomach through the pyloric sphincter where
it is mixed with intestinal and pancreatic enzymes, bile and
sodium bicarbonate, which neutralizes the acidic chyme.
Accessory glands:
Pancreas: - releases sodium bicarbonate to neutralize acidic
chyme
(PH 2.5 8)
- releases digestive enzymes: pancreatic amylase starch

5. Lipase lipids
Trypsin polypeptides
These enzymes, as well as intestinal enzymes, have an optimal
pH = 7.5,
Therefore need to have the chyme neutralized before they can
work properly.
Liver: - 1.5 kg organ
- secretes Bile (bile salts)
these help emulsify (separate) fats which increases the
surface area, enabling lipases to break down lipids more
efficiently.
The liver performs a vast number of functions (500),
including production of bile from cholesterol, recycling of red
blood cells, glycogen storage, storage of fat-soluble vitamins,
deamination of amino acids, and detoxification of poisons.
Everything that enters the body must go through the liver to
be cleared.
Gall bladder: - small sac near liver stores bile.
3. Absorption of nutrients
Stomach: - small amounts of water- alcohol some medicines,
e.g. aspirin
Small intestine: jejunum - where most of the absorption takes
place.
Ileum: where the remaining nutrients are absorbed
Absorption is greatly aided by the folded interior structure of
the intestine, particularly due to the presence of the villi and
microvilli.
Structure of Villi: - tiny finger like projections lining the
interior of the intestines
- contain two types of vessels:
capillaries – tiny blood vessels
- collect water soluble nutrients
glucose, amino acids

6. lacteal - contain lymph
- collect products of fat digestion
fatty acids and glycerol
Final products of digestion (or what is absorbed)
Macromolecule Digestion starts Digestion complete Final
product
Starch (CHO) mouth - amylase duodenum (SI) glucose
Protein stomach HCl + pepsin duodenum (SI) amino acids
Lipids duodenum bile + lipase duodenum (SI) fatty acids +
Glycerol small molecules like vitamins, minerals, natural
glucose and amino acids do not need to be digested and are
easily absorbed by the small intestine.
Water is absorbed throughout the alimentary (GI) tract
but the majority of water absorption occurs in the large
intestine also known as the Colon.
The Colon – the large intestine (the bowel)
Structure: - 1.5 m in length, 5 cm in diameter (twice the
diameter of SI)
- made up of four sections:
Ascending
Transverse
Descending
Sigmoid process
-the colon ends with the rectum
Function: - main job is to reabsorb water- bacteria here
produce vitamins k.
4. Egestion of waste
Cellulose: main component of feces, along with living and dead
bacteria and water.
- Fiber, found in plant cell walls, cannot be digested by
humans
Feces: - waste is stored in rectum- removed by body removing
possible toxic materials.

7. Egestion controlled by anal sphincter which allows feces to
leave rectum through the anus. Toilet training is learning how
to control the anal sphincter.
Small Intestine Enzymes
1. Cholecystokinin – Stimulates digestion of proteins and fats
2. Secretin – Controls secretion of duodenum and osmoregulation
3. Sucrase – Convertssucrose to disaccharides and monosaccharide
4. Maltase – Converts maltose to glucose
5. Lactase – Convertslactose to glucose and galactose
6. Isomaltase – Converts maltose to isomaltose
Stomach Enzymes
Pepsin is the main gastric enzyme. It breaks proteins into smaller peptide fragments.
Gelatinase degrades type I and type V gelatin and type IV and V collagen, which are
proteoglycans in meat.
Gastric amylase degrades starch, but is of minor significance.
Gastric lipase is a tributyrase by its biochemical activity, as it acts almost exclusively
on tributyrin, a butter fat enzyme.
Pepsin enzyme is secreted by gastric glands
Renin enzyme change the liquid milk to solid
Mouth Enzymes
1. Ptyalin – Converts starch to simple soluble sugars
2. Amylase – Convertsstarch to soluble sugars
3. Betaine – Maintainscell fluid balance as osmolytes
4. Bromelain – Anti-inflammatory agent, tenderizes meat
Pancreas Enzymes
1. Pancreatic lipase – Degrades triglycerides into fatty acids and glycerol
2. Chymotrypsin – Converts proteins to aromatic amino acids
3. Carboxypeptidase – Degradation of proteinsto amino acids
4. Pancreatic amylase – Degradation of carbohydrates to simple sugars

8. 5. Elastases – Degrade the protein elastin
6. Nucleases – Conversion of nucleic acids to nucleotides and nucleosides
7. Trypsin – Converts proteins to basic amino acids
8. Steapsin – Breakdownof triglycerides to glycerol and fatty acids
9. Phospholipase – Hydrolyzesphospholipidsinto fatty acids and lipophilic substances.
WEBSITES:
http://www.medtropolis.com/VBody.asp
http://www.innerbody.com/htm/body.html
http://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion/smallgut/anatomy.html
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/F/FramesVersion.html