CHAPTER I
INTRODUCTION
1.1.BACKGROUND
The
gastrointestinal tract (GIT) consists of a hollow muscular tube starting from
the oral cavity, where food enters the mouth, continuing through the pharynx,
oesophagus, stomach and intestines to the rectum and anus, where food is
expelled. There are various accessory organs that assist the tract by secreting
enzymes to help break down food into its component nutrients. Thus the salivary
glands, liver, pancreas and gall bladder have important functions in the
digestive system. Food is propelled along the length of the GIT by peristaltic
movements of the muscular walls.
The
primary purpose of the gastrointestinal tract is to break food down into
nutrients, which can be absorbed into the body to provide energy. First food
must be ingested into the mouth to be mechanically processed and moistened.
Secondly, digestion occurs mainly in the stomach and small intestine where
proteins, fats and carbohydrates are chemically broken down into their basic
building blocks. Smaller molecules are then absorbed across the epithelium of
the small intestine and subsequently enter the circulation. The large intestine
plays a key role in reabsorbing excess water. Finally, undigested material and
secreted waste products are excreted from the body via defecation (passing of
faeces).
In
the case of gastrointestinal disease or disorders, these functions of the
gastrointestinal tract are not achieved successfully. Patients may develop
symptoms of nausea, vomiting, diarrhea, malabsorption, constipation or
obstruction. Gastrointestinal problems are very common and most people will
have experienced some of the above symptoms several times throughout their
lives.
1.2.PURPOSE
1.2.1. GENERAL PURPOSE
The students and readers understand the importance
of gastrointestinal system.
1.2.2. SPECIFIC PURPOSE
The students be able to :
1)
Explain and
describe anatomy and physiology of Gastrointestinal System
2)
Expressing
various kinds vocabulary about Gastrointestinal System
3)
Apply their
knowledge about Gastrointestinal System in hospital and society
CHAPTER II
THEORETICAL REVIEW
2.1. ANATOMY AND PHYSIOLOGI OF
GASTROINTESTINAL SYSTEM
1. Oral Cavity (Mouth)
Food enters the
gastrointestinal system via the mouth or oral cavity, mucous membrane lined.
The lips (labia) protect its outer opening, cheeks from lateral walls, hard
palate and soft palate form anterior/posterior roof. It communicate with nasal
cavity behind soft palate. Floor is muscular tongue. Tongue has bony
attachments (styloid process, hyoid bone) attached to floor of mouth by
frenulum. Posterior exit from mouth guarded by a ring of palatine/lingual
tonsils. Enlargement of this organ called sore throat or tonsillitis.
Food is first processed
(bitten off) by teeth, especially the anterior incisors. Suitably sized
portions then retained in closed mouth and chewed or masticated (especially by
cheek teeth, premolars, molars) aided by saliva. Ducted salivary glands open at
various points into mouth. This process involves teeth (muscle of mastication
move jaws) and tongue (extrinsic and intrinsic muscles). Mechanical breakdown,
plus some chemical (ptyalin, enzyme in saliva). Taste buds allow appreciation, also
sample potential hazards (chemical, toxins).
2.
Throat
In leaving the mouth a bolus of food must cross the
respiratory tract (trachea is anterior to esophagus) by a complicated mechanism
known as swallowing or deglutination which empties the mouth and ensures that
food does not enter the windpipe swallowing involves coordinated activity of
tongue,soft palate pharynx and esophagus.The first (buccal) phase is voluntary,
food being forced into the pharynx by the tongue. After this the process is
reflex. The tongue blocks the mouth, soft palate closes off the nose and the
larynx rises so that the epiglottis closes off the trachea.Food thus moves into
the pharynx and onwards by peristalsis aided by gravity.if we try to talk
whilst swallowing food may enter the respiratory passages and a cough reflex
expels the bolus.
3.
Esophagus
The esophagus is
the first part of the digestive tract proper and shares its distinctive
structure. Basic tissue layers of the gut are :
1)
Mucosa
Innermost, moist lining
membrane. Epithelium (friction resistant stratified squamous in esophagus,
simple beyond) plus a little connective tissue and smooth muscle.
2)
Submucosa
Soft connective tissue
layer, blood vessels, nerves, lymphatics.
3)
Muscularis
externa
Typically circular
inner layer, longitudinal outer layer of smooth muscle.
4)
Serosal fluid
producing single layer
4.
Stomach
Stomach is located below the body cavity
constriction or above abdominal cavity. Stomach has some primary functions,
such as storing food, mixing food, and preparing the hydrolysis process of
protein enzymes.
Stomach consists of three parts. Firstly, food
enters the stomach through cardiac. Then, it goes toward fundus and pylorus.
Pylorus is close to the lock muscle (valve) that controls food transfer into
the intestine.
Stomach wall is composed of some muscular layers,
longitudinal muscles in the outer layer, circular muscles in the middle layer,
and oblique muscle in the inner layer. When these muscle contract, the food in
gastric will mix all together with gastric acid and become chymus.
Stomach wall has stomach glands producing mucosa,
gastric acid, and gastrin hormone.
1)
Mucus is
produced by mucose cells.
2)
Gastric acid
consists of several substances as follows :
a.
Hydrochloride
acid (HCl) is produced by parietal cells. It is necessary to kill germs, create
acidic environment (with a pH nearly to 1), stimulate secretion of intestine
juice, stimulate the opening and closing of pylorus sphincter, and activate
pepsinogen into pepsin.
b.
Pepsin is a
protease enzyme which breaks down protein into pepton.
c.
Rennin is an
enzyme which has function to curdle the milk protein (casein). Generally, it is
found in young mammals.
d.
Lipase is an
enzyme which breaks down lipid into fatty acid and glycerol. It is produced by
salivary gland that is accumulated in gastric.
3)
Gastrin hormone
is a hormone that stimulates secretion of gastric acid in gastric.
5.
Small Intestine
Small intestine has the length of about
8.5 meters. On the wall, there are some glands producing intestine secretion.
Small intestine is composed of three parts which are as follows :
a)
Duodenum
(twelve-finger intestion) is the inferior section of small intestine with about
25 cm in length, U-shaped, and an end section of gall bladder and pancreas.
b)
Jejunum is the
central section of small intestine with the length of about 7 m.
c)
Ileum
(absorption intestine) is the final section of small intestine with the length
of about 1 m.
Intestinal cells absorb
nutrient needed by body. The waste material that cannot be used by body is
transferred to large intestine.
In lipid absorption,
fatty acid reacts with bile salt to form an emulsion, and with glycerol, it is
absorbed by villous. In villous, fatty acid is separated from bile salt, and it
bonds glycerin to form lipid (phospholipid). Phospholipid is released into
lymph system in the form of small spheres layered with protein (chylomicron)
and then it is carried to venous.
Other nutrients, such
as vitamin, mineral, and water, will be absorbed by capillary vessel. The remain
bile salt will enter the blood, and then it is carried to liver to be converted
into bile again.
6.
Large Intestine
(Colon) and Anus
Human colon is divided
into three sections, ascendence, transcendence, and descendence. The colon
tract ends in an area which is so-called rectum. Rectum ends in a hole at body
surface which is called anus. Rectum has muscle that plays a role to hold the feces
not to go into the anus, known as Houston valve.
Large intestine and
small intestine are separated by a valve called ileosecum which is necessary to
prevent food from coming back into small intestine. At the end of ileosecum,
there is a appendix and cecum. Colon reabsorbs water and mineral that come from
material waste of small intestine.
Large intestine
contains a population of symbion bacteria that function in the substrate of
plant cellulose, pectin, removed intestinal cells, and polysaccharide from
intestinal mucosa. The fermentation results are organic acid, metan gas, and
hydrogen. During digestion, there are also bacteria population producing
vitamin B and K. The vitamin is absorbed by the cell of large intestinal
surface. The waste materials of digestive process is thrown away through anus
(defecation).
7. Accessory Digestive
Organs
7.1. Salivary Glands
Three pairs of salivary
glands communicate with the oral cavity. Each is a complex gland with numerous
acini lined by secretory epithelium. The acini secrete their contents into
specialised ducts. Each gland is divided into smaller segments called lobes.
Salivation occurs in response to the taste, smell or even appearance of food.
This occurs due to nerve signals that tell the salivary glands to secrete
saliva to prepare and moisten the mouth. Each pair of salivary glands secretes
saliva with slightly different compositions.
7.2. Pancreas
The pancreas is a lobular, pinkish-grey organ that lies behind
the stomach. Its head communicates with the duodenum and its tail extends to
the spleen. The organ is approximately 15cm in length with a long, slender body
connecting the head and tail segments. The pancreas has both exocrine and
endocrine functions. Endocrine refers to production of hormones which occurs in
the Islets of Langerhans. The Islets
produce insulin, glucagon and other substances and these are the areas damaged
in diabetes mellitus. The exocrine (secretrory) portion makes up 80-85% of the
pancreas and is the area relevant to the gastrointestinal tract.
It is made up of
numerous acini (small glands) that secrete contents into ducts which eventually
lead to the duodenum. The pancreas secretes fluid rich in carbohydrates and
inactive enzymes. Secretion is triggered by the hormones released by the
duodenum in the presence of food. Pancreatic enzymes include carbohydrases,
lipases, nucleases and proteolytic enzymes that can break down different
components of food. These are secreted in an inactive form to prevent digestion
of the pancreas itself. The enzymes become active once they reach the duodenum.
7.3. Liver and Gallbladder
Bile, a watery greenish
fluid is produced by the liver and secreted via the hepatic duct and cystic
duct to the gall bladder for storage, and thence on demand via the common bile
duct to an opening near the pancreatic duct in the duodenum. It contains bile
salts, bile pigments (mainly billirubin, essentially the non-iron part of
haemoglobin) cholesterol and phospholipids. Bile salts and phospholipids
emulsify fats, the rest are just being excreted. Gallstone are usually
cholesterol based, may block the hepatic or common bile duct causing pain,
jaundice.
2.2. TYPES AND CLASSIFICATION
2.2.1. Mechanical
Digestion
Mechanical digestion is
simply the aspects of digestion achieved through a mechanism or movement. There
are two basic types of mechanical digestion.
Mastication: The first
step when it comes to digestion actually begins as soon as food enters the
mouth. Mastication (chewing) begins the process of breaking down food into
nutrients. As a type mechanical digestion, chewing our food is an important
part of the digestive process because smaller pieces are more readily digested
through chemical digestion.
Peristalsis: Mechanical
digestion also involves the process known as peristalsis. Peristalsis is simply
the involuntary contractions responsible for the movement of food through the
esophagus and intestinal tracts.
2.2.2. Chemical
Digestion
Chemical digestion is
much like it sounds – those aspects of digestion achieved with the application
of chemicals to our food. Digestive enzymes and water are responsible for the
breakdown of complex molecules such as fats, proteins, and carbohydrates into
smaller molecules. These smaller molecules can then be absorbed for use by
cells. The presence of these digestive enzymes accelerates the digestion
process, where absence of these enzymes slows overall reaction speed.
Currently, there exist eight digestive enzymes mainly responsible for chemical
digestion.
2.3. ETIOLOGY
2.3.1. Gastritis
Gastritis is an acute
or chronical inflammation on mucosa layer of stomach wall. Weaknesses in the
mucus-lined barrier that protects your stomach wall allow your digestive juices
to damage and inflame your stomach lining. A number of diseases and conditions
can increase your risk of gastritis. Gastritis can develop suddenly (acute
gastritis) or gradually and last for an extended period (chronic gastritis).
2.3.2. Diarrhea
Diarrhea is an
irritation on the membrane of colon wall caused by bacteria dysentriae, bad
diet, poiosonous matters, and stress.
Diarrhea can be described as an abnormal increase in
the frequency, volume or liquidity of your stools. The condition usually lasts
a few hours to a couple of days. Diarrhea is typically associated with
abdominal cramps.
The most common causes of diarrhea include:
-Viruses
-Bacteria
-Parasites
Diarrhea that persists
for more than a couple of days is considered chronic and may be a sign of an
underlying condition, such as inflammatory bowel disease or an infection. In
these cases, diarrhea may lead to dehydration and requires the care of your
doctor. Dehydration occurs when the body has lost too much fluid and
electrolytes -- the salts potassium and sodium. The fluid and electrolytes lost
during diarrhea need to be replaced promptly because the body cannot function
properly without them.
2.3.3. Appendicitis
Appendicitis is an
inflammation and swelling of blind gut. The cause of appendicitis isn't always
clear. Sometimes appendicitis can occur as a result of:
·
An obstruction.
Food waste or a hard piece of stool (fecal stone) can block the opening of the
cavity that runs the length of your appendix.
·
An infection.
Appendicitis may also follow an infection, such as a gastrointestinal viral
infection, or it may result from other types of inflammation.
In both cases, bacteria
inside the appendix multiply rapidly, causing the appendix to become inflamed,
swollen and filled with pus. If not treated promptly, the appendix can rupture.
2.4. CLINICAL APPEARANCES
2.4.1. Gastritis
The signs and symptoms
of gastritis include:
·
Gnawing or
burning ache or pain (indigestion) in your upper abdomen that may become either
worse or better with eating
·
Nausea
·
Vomiting
·
A feeling of
fullness in your upper abdomen after eating
Gastritis doesn't
always cause signs and symptoms.
2.4.2. Diarrhea
Signs and symptoms
associated with diarrhea may include:
·
Frequent loose,
watery stools
·
Abdominal cramps
·
Abdominal pain
·
Fever
·
Bleeding
·
Dizziness from
dehydration
2.4.3. Appendicitis
Signs and
symptoms of appendicitis may include:
·
Aching pain that
begins around your navel and often shifts to your lower right abdomen
·
Pain that
becomes sharper over several hours
·
Tenderness that
occurs when you apply pressure to your lower right abdomen
·
Sharp pain in
your lower right abdomen that occurs when the area is pressed on and then the
pressure is quickly released (rebound tenderness)
·
Pain that
worsens if you cough, walk or make other jarring movements
·
Nausea
·
Vomiting
·
Loss of appetite
·
Low-grade fever
·
Constipation
CHAPTER III
CLOSING
3.1. CONCLUSION
The Gastrointestinal
Tract starting from the mouth and ends at the anus. In every phase of the
movement of food involves many organs and substances, such as : enzyme
(ptyalin, rennin, pepsin, HCl), pancreas, liver, etc.
Nursing students as
candidates for future nurses have to understand about this theme. Because, a nurses
should be give provide nursing care in gastrointestinal disease.
REFERENCES
Nursalam. 2010. English in Nursing-Midwifery Science and
Technology. Jakarta : Salemba Medika
Keshav, Satish and
Bailey, Adam. 2013. The Gastrointestinal
System at a Glance 2nd Edition. UK : Wiley-Blackwell
Martini. 2001. 5th Edition Fundamentals of
Anatomy and Physiology. US : Pearson
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