The Digestive System
By: Taneya Jones,
Malina Wong
The system itself
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•Function: The overall function of the Digestive system is the mechanical and chemical break
down of foods, using its nutrients for cells.
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A.
1.) The Digestive system beings with the Alimentary canal. This canal includes the mouth,
pharnyx, esophagus, stomach, small intestine, large intestine, the rectum, and the anus.
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2.) The acsessory organs include the salivary glands, liver, gall bladder, and pancreas.
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3.) But overall, the Digestive system is an enlarged tube, opened on both ends (the mouth and
anus) in order to bring nutrients to the body.
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4.) The alimentary canal is a muscular tube intervening the ventral cavity. Specialized in certain
regions, to carry certain functions.
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5.) The structure of the canal wall determines the movement of food through the body.
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6.) The parts of the canal are:
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submucosa
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Mucous membrane
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Muscular layer
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serous Layer
Alimentary canal
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7. The action of the Alimentary canal is to provide 2 types of
movements: mixing and propelling. Mixing occurs when smooth
muscles in small segments of the tube contract rythmically.
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EX: when the stomach is full, waves of muscular contractions move
along its walls from one end to another. These waves mix foods with
digestive juices that the mucous membranes secrete.
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Propelling, also known as “perstalsis”, occurs when a ring of
contraction appears in the way of the tube.
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EX: when food and waste products are pushed down into the
intestine. After passing through the esophagus. After reaching the
esophagus, the food then goes to the stomach. But peristalsis is what
pushes the food down, to the stomach, no matter what position the
body is in.
The mouth
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1.) The mouth is the first, or beginning portion of the alimentary
canal receiving, and secreting saliva.
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2.) The mouth receives food, and begins digestion by
mechanically reducing the size of solid particles with the help of
saliva. Saliva then mixes in with the food, and decreases both the
size and density as the food gains more and more moisture.
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3.) The lips, cheek, tongue, and palate around the mouth are
referred to as the “ oral cavity”
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4.) The space between the teeth, cheeks, and lips are called
vestibule.
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5.)
Members of the mouth:
The mouth continued
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Cheek: pads of subcutaneous fat muscle associated with expression, chewing, and inner linings
of moist, stratified squamous epithelium.
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Lips: highly mobile structures that surround the mouth opening. They contain skeletal muscles,
along with sensory receptors useful for judging temperature and the texture of foods.
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Tongue: nearly fills the oral cavity, when the mouth is closed. A mucous membrane covers the
tongue, and a membrane fold called “frenulum” connects the midline of the tongue to the floor of
the tongue. The “body” of the tongue is mostly skeletal muscle. These muscles mix food particles,
with saliva during chewing, and move food toward the pharynx during swallowing. Rough
projection on the tongue surface provide friction which helps handle food and sense taste with
the taste buds.
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Palate: forms the roof of the oral cavity. And consist of a hard, anterior part, along with a soft
palate forming an arch, which extends posteriorly and downward as a pear- shaped projection.
During swallowing, the muscle of the soft palate is drawn apart from the uvula. This action closes
the opening between the nasal cavity and the back of the mouth, palatine, and the tonsils.
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Teeth: little molds of calcium that usually shed in the same order they grew. But before this
happens, their roots are reabsorbed Pressure from the developing secondary teeth pushes the
primary teeth out of the sockets. The secondary set consist of 32 teeth total—with 16 in each jaw.
The secondary teeth appearing around the age of 6 , but may not have a complete set until one’s
molars appear, which is from years 17 to 25 years old.
Major organs of the system
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Saliva glands: secrete saliva, which contains enzymes that initiate the breakdown of carbohydrates.
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Liver: produce bile, which emulsifies fat.
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Gallbladder: stores bile, and introduces into the small intestine
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Pancreas: produces and secretes pancreatic juices, containing digestive enzymes and bicarbonate ions into the
small intestine.
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Pharynx: connects mouth with esophagus.
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Esophagus: peristalsis pushes food into the stomach.
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Stomach: a “J” shaped organ, pouch-like that hangs inferior to the diaphragm and upper left portion of the
abdominal cavity that secretes and enzymes, and mixes food with secretions to begin enzymatic digestion proteins.
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Small intestine: mixes food with bile and pancreatic juice. It is the final breakdown of food molecules, and is the
main site of nutrient absorption.
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Salivary secretions and enzymes:
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Amylase: a digestive enzyme that splits starch and glycogen molecules into disaccharides.
Other glands
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Pancreatic lipase: breaks triglyceride molecules into fatty acids and glycerol. It also
contains nucleases which are enzymes that break down nucleic acid molecules into
nucleotides.
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Mucous: secreted by mucous cells, creating a thick liquid, which binds food particles
and helps lubricate the throat for swallowing.
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Parotid glands: largest of the salivary glands, each gland lies anterior or somewhat
inferior to each ear between the skin of the cheek and the masseter muscle. This
gland secretes a clear, watery fluid that is rich in amylase.
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Submandibular glands: located in the floor of the mouth on the inside surface of the
lower jaw, secreting a more viscous fluid than parotid glands.
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Sublingual glands: the smallest of the major salivary glands on the tongue. Their
sensory cells are primarily the mucous type, making their secretions thick and
mucus-like.
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Gastrin: increase the secretory activity of gastric glands
Mixing and emptying actions
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Mixing and emptying actions: following a meal the mixing movements of the stomach wall aid in producing a
semi-fluid paste of food particles and gastric juice called chime accumulates near the pyloric sphincter, the
muscle begins to relax. Stomach contractions push chime little by little into the small intestine.
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Swallowing mechanisms: swallowing has three stages. The first stage, which is voluntary, food is chewed and
mixed with saliva. Then the tongue rolls this mixture into a mass, or collection and forces it into the pharynx. The
second stage begins as food stimulates sensory receptors around the pharyngeal opening. This triggers the final
stage, swallowing reflex, which includes the following actions.
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Chyme: semi-fluid paste of food particles and gastric juice.
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Hepatic lobules: the liver’s functional units, consisting of many hepatic cells radiating outward from a central vein.
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Hepatic sinusoids: separate plate- like groups of the hepatic cells from each other, and bold from the digestive
track which is carried in the hepatic portal vein brings newly absorbed nutrients into the sinusoids and nourishes
the cells.
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Hepatic ducts: ductile of neighboring lobules unite that form larger bile ducts.
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Common hepatic duct: the merged ducts.
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Bile: a yellowish green liquid continuously secreted from hepatic cells.
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Gall bladder: a pear- shaped sac located in the depression on the liver’s inferior surface, connecting to the cystic
duct, which in turn joins the common hepatic duct. The gall bladder is lined up with epithelial cells and has a
strong, muscular layer on its wall. It stores bile between meals, reabsorbs water to concentrate bile, and contracts
to release bile into the small intestine.
Clinical aspect (connection)
* The process of digestion helps to explain the apparent paradoxical
association of eating excess refined carbohydrates, rather than access
fats with increased cardiovascular risk factors. Excess carbohydrates
are converted to triglycerides which in adipose cells, are enzymatically
dismantled and repackaged as LDL.
Suggestive Dietary Plan:
 Grains
 Vegetables
 Fruit
 oils
 Milk
 Meat& beans
 Daily activity of some sort
Diseases and other conditions
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Diseases and other conditions:
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1.)Ulcers are open sores or lesions that develop on the walls of the esophagus, stomach and duodenum. This condition can be caused by various factors, like stress, lifestyle
and medication. While duodenal ulcers are very common, stomach ulcers are not rare.
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2.) Gastro esophageal Reflux Disease (GERD) is also common in humans. The characteristic feature of this condition is heartburn. Otherwise known as acid reflux disease,
this condition is caused by the abnormal reflux of the stomach contents (including acids) to the esophagus.
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3.) Gastritis is a digestive disease that is caused by bacterial infection, regular use of medication like NSAIDs, and excess alcohol consumption. Gastritis can cause bloating,
vomiting, diarrhea, indigestion, and abdominal pain.
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When the movement of food from the stomach to the small intestine gets too slow or stops totally, the condition is called gastro paresis. The symptoms of gastro paresis
include nausea, heartburn, and upper abdominal pain, vomiting, and bloating. This condition is caused by malfunctioning of the stomach muscles; and is treated with
medication to stimulate the muscles.
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4.) Celiac disease or gluten intolerance is another common digestive system disease. It is a type of autoimmune disease that affects the small intestine. In people with this
condition, the immune system reacts to gluten in some food products, like wheat. This causes damage to the small intestine walls, which in turn, hinders nutrient absorption.
Celiac disease symptoms include diarrhea, pain, bloating, pain and anemia.
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6.) Ulcerative colitis is another inflammatory condition that affects the large intestine. This condition is characterized by ulcers, blood in stools and abdominal pain. Untreated
ulcerative colitis can lead to perforation of the colon and other complications.
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7.) Diverticulosis is a condition that affects the large intestine or colon, and is characterized by formation of pouches on the colon wall. These pouches bulge outwards,
thereby causing pain and discomfort, along with bloating and constipation. Inflammation of these pouches is called diverticulitis that can cause fever, nausea and severe
pain.
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8) Constipation is a common digestive system disorder. It can be caused by different factors, like lifestyle, diet, medication, and medical conditions. It can be defined as
infrequent bowel movements (less than three times a week), and hard to pass dry stools. Constipation can be relieved with laxatives. Lifestyle changes and treatment of the
underlying problem can relieve this condition.
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9.) Rectal prolapse is a common condition, wherein the walls of the rectum bulge outward through the anal opening. This condition is categorized into three types, as per
the degree of prolapse. Rectal prolapse is mostly seen in elderly people and those with constipation.
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10.) Anal fissures are cracks or cuts on the skin that lines the lower part of the sex, syphilis and HIV. Most of the acute anal fissures disappear within a few days; chronic ones
may take two to four weeks to subside. rectum, called the anus. This condition is characterized by rectal bleeding and pain. It is mainly caused by hard stools that are
difficult to expel. Other causes include anal