Digestive System of a Human
Process
of food Digestion
Human
body is like some kind of a machine. Every machine use different source of
energy to operate. Energy which is required for different biological processes
that take place in human body is obtained from the foods we eat. These food
contain various nutrients such as carbohydrates, lipids and proteins.
Carbohydrates, lipids and proteins are complex organic molecules that do not
dissolve in water. These compounds cannot be absorbed into the human body as in
the form it is. Therefore they should be broken down into small particles.
The process by which the complex organic compounds are converted into simple organic products to be absorbed into the human body is called
digestion of food or the Process of Food Digestion.
There
are two main process of Food digestion. Namely mechanical processes and chemical
processes. During mechanical process the physical nature of the food is
altered by breaking down of food into small pieces by teeth inside mouth. During
chemical process, the insoluble complex compounds are broken down into simple
molecules by the action of enzymes.
As an example, by using salivary amylase (ptyalin) enzyme
inside the mouth Starch is converted into maltose.
Some nutrients such as mineral salts, some vitamins, glucose, fructose and
galactose can be used by the body without any digestion.
The organs involved in food digestion, are collectively called as digestive
system.
Human
digestive system
Human digestive system is a complex system which consist of ,
Buccal
cavity
Oesophagus
Diaphragm
Salivary glands
Epiglottis
Small intestine
Stomach
Liver
Gall bladder
Pancreas
Large intestine
Appendix
Caecum
Rectum
Anus
Although
it contain so many different parts it is actually a single tube which runs from
mouth to anus. The functions take place in the digestive system are "food
digestion, absorption of digested end products and removal of
undigested materials" from the body.
Assignment
- 6'1
Digestion
in the buccal cavity
Digestion
of food starts in the mouth. Mouth is the opening of the buccal cavity to the
environment. The buccal cavity is made up of upper and lower jaws and it is
surrounded by muscular lips at the bottom and top. Buccal cavity is surrounded
by cheeks. Although Teeth are present in both jaws. Only the lower jaw can be
moved. The tongue is attached to the floor of the buccal cavity and there are three
salivary glands present in the buccal cavity. They secrete saliva and the tongue
helps in identification of taste, mixing of food with saliva and swallowing.
Initially
digested food is formed into a bolus and pushed to the posterior part of the buccal
cavity. Then the food is pushed into the pharynx. Pharynx is a common
area to both digestive and respiratory systems. There is a movable organ called
epiglottis found just above the opening of trachea. When bolus is
swallowed the epiglottis moves down to close the opening of trachea.
Then bolus enters into oesophagus without entering into trachea.
Epiglottis
helps to prevent entering food into the trachea. When food enters to pharynx,
respiratory track is blocked by epiglottis. This prolong blockage of trachea may
cause death. If the food is not removed instantly, the person may die due to blockage
of respiratory tract.
Oesophagus is a constricted tube.
How
is food moved along a constricted tube?
The bolus passes through the oesophagus by peristaltic movements. As oesophagus
is a muscular structure, due to contractions and relaxations of its wall the peristaltic
movements appear as waves. These peristaltic movements provide the force to
propel the bolus forward. Then food is moved into stomach by peristaltic
movements.
Digestion
in the stomach
The
stomach is an organ which is like a dilated sac. Due to the peristaltic
activity of muscles in
the stomach wall the bolus is broken down and mixed well into a chyme.
Several enzymes ooze out into the stomach. It is collectively called the gastric
juice. The gastric juice contains mainly hydrochloric acid (HCl) and
pepsin enzyme.
HCl activates pepsin and pepsin starts the
protein digestion to produce polypeptides. Renin present in infants causes
coagulation of milk. Food retain in stomach for about three to four hours.
Although the digested end products are not absorbed but some water, glucose and
some drugs may absorb. Chyme containing partially digested proteins, digested
and undigested carbohydrates, undigested lipids, water, minerals and vitamins
are released into the proximal part of small intestine, duodenum part by part.
Hunger
is a signal that indicates the need of food. When the stomach is empty, it
continues to contract. So it causes a pain. It gives a sense about hunger.
Hunger is a signal that indicates the need of food.
Digestion
in the small intestine
Small
intestine is the place where the chemical digestion of food mainly happens. Pancreatic
enzymes as well as intestinal enzymes involve in this digestion. In a grown
adult the small intestine is about 7m in length. The duodenum is the
proximal part of the small intestine which is shaped like a C.
The
duct of the pancreas and the gall bladder opens into the duodenum
via a single pore. Pancreatic juice is secreted into the duodenum
through pancreatic duct. It contains three main enzymes. They are trypsin,
amylase and lipase. The bile carried through the bile duct is added to it. Bile
is produced in the liver and stored in the gall bladder and it contains bile
pigments, bile salts, bicarbonate ions and water.
The lipids in food are broken down into small droplets by the process called emulsification
due to mixing of bile with food at duodenum. So the enzymes get a greater
surface area to act on lipid food.
Intestinal
juice secreted
by the wall of the intestine contains, maltase, sucrose,
lactase, peptidase and mucus. Mucus lubricates food and then ease the passage
of
food materials along the gut. It protects the inner lining of gut wall.
Proteins present
in wall of stomach and intestine is protected by the protein digestive enzymes
as
there is a layer of mucus on the wall.
The
small intestine is adapted to increase its efficiency of absorption by
being a long tube
Presence of circular folds in the inner wall
Presence of finger like projections called villi in the circular folds
Presence of microvilli in the epithelial cells of villi
thin epithelial lining on villi
Villi are highly vascularized
Organ
The
digestive end products like Amino acids,Vitamins,Mineral salts,Monosaccharides
(Glucose/ Galactose/ Fructose) are absorbed into the blood capillaries of
villi.
Fatty acids and glycerol formed by digestion of lipids are absorbed into
lacteals and enter into blood circulatory system. When there is high amount of glucose
in blood, they are converted into glycogen and stored in liver. In the same way
when the concentration of glucose is decreased, glycogen breaks down to form glucose
and is added to blood. The unabsorbed materials in small intestine are sent to
the large intestine.
Processes
in the large intestine
The
large intestine starts with caecum and ends up at anus. Length of
the large intestine of a grown adult is about 1.5 m and dilated part of the
large intestine is the rectum. The materials entering into the large intestine mainly
it contains undigested cellulose and water. A small blind ended tubular
structure starts at the end of the caecum. It is known as the appendix. It is very
small in humans and it may be infected and become swollen. This disease is known
as appendicitis.
The
main function of the large intestine is to absorb water from matter received
from
ileum. Thereby making it into semi solid. The matter entered into large
intestine is
known as faecal matter. Faecal matter is yellow in colour due to bile pigments
in it.
Undigested food, microorganisms, epithelial cells and mucus are present in
faecal
matter. When large intestine fills with faecal matter, it passes out from the
anus.
The
diseases and disorders associated with digestive system
Assignment
- 6'2
Gastritis
Generally
known as acidity. Inflammation of inner lining of mucosa of stomach is known as
gastritis. It is a common disease among people due to
- Skipping
of meals
- Consumption of acidic and spicy food
- Excessive smoking and alcohol consumption
- Mental stress
The
main symptoms are,
- Regurgitation
of acid to mouth,
- Burning
feeling and pain in stomach.
When
the condition becomes worse, ulcers appear in stomach and duodenal wall.
Bleeding
can take place. By following healthy food diets and good habits one can avoid
the above disease.
Constipation
Difficulty
in defecation due to hardening of faecal matter is known as constipation.
Faeces remain in the large intestine for a longer period of time and absorption
of
water takes place excessively, Thereby this condition may occur.
Reasons
for constipation are as follows,
- Consumption
of food with low dietary fires
Not taking required volume of water
Postponing of defecation
By
avoiding above conditions and habits one can avoid this disease. Due to
forceful defecation, the anal canal may damage and bleeding can occur. Haemorrhage
may occur Due to constant constipation
Typhoid
Typhoid
is caused by a bacterium. The pathogen is transmitted through food and water.
It can enter into the body through mouth also while swimming and bathing. It
may enter into the body through faecal matter of patient, consumption of
contaminated food and fles.
The
main symptoms are,
- Pain
in arms and legs.
- Headache
and fever.
It
is a disease which gradually becomes worse. At initial stages constipation can
occur. Tongue is covered by a plaque. After sometime stomachache and diarrhea
can occur. Ulcers can form in the small intestine and cause bleeding. Therefore
blood is released with faecal matter. Due to ulcers, the wall can be damaged.
Disease can be identified by a blood test or stool test. Typhoid can be
prevented by getting a vaccine.
Diarrhoea
Diarrhoea
occurs when the intestines are infected with a virus, bacteria or a parasite.
This is also disease is transmitted by the faeces of an
infected person. The main symptom
is release of faecal matter in liquid state. Dehydration may occur due to loss
of fluid. Absorption of water in the large intestine will not occur properly. If
dehydration becomes worse due to diarrhoea, it may be fatal. So it is needed to
consume more water and consult a doctor immediately.
The above two diseases can be avoided by taking preventive measures given below
Images by
.jpeg)
0 Comments
Your ideas matters