Download Digestive System

1/18/2017
Digestive System
Main Organs of the Digestive System
The main organs of the Digestive System form a tube open at both
ends. This tube runs all the way through the ventral cavities of the
body. It is called the GI Tract or Alimentary Canal.
Wall of the GI Tract
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Mouth
(Oral Cavity)
• Lips
Lips
• Covered externally
by skin
• Covered internally
by mucous
membrane
• Cheeks
• Tongue +
its muscles
• Hard + Soft Palates
Cheeks
• Continuous with the lips in front and lined by mucous
membrane which continues with the gums and soft palate.
• Formed primarily by the buccinator muscle. This muscle
and a generous amount of fat are sandwiched between the
outer skin and mucous membrane.
• Junction between
skin and mucous
membrane is VERY
sensitive and easily
irritated.
Tongue
The tongue is a solid mass of skeletal muscle components
covered by mucous membrane. These muscle fibers are oriented
in all directions, giving the tongue extreme maneuverability.
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Papillae
Rich supply of
blood vessels
• Taste buds are located on the sides of vallate papillae
and fungiform papillae.
• Filiform papillae do not contain taste buds.
Palates
Hard Palate:
• made up of parts of
4 bones = 2 maxillae
and 2 palatines
Soft Palate:
• made up of muscle
• forms a partition
between the mouth
and the nasopharynx
Cleft Palate
Occurs when the roof of the mouth does not
completely close, leaving an opening that can
extend into the nasal cavity. The cleft may
involve either side of the palate and can
extend from the front of the mouth (hard
palate) to the throat (soft palate). The cleft
may also include the lip.
The causes of cleft lip/palate are not well understood. Studies
suggest that a number of genes, as well as environmental factors,
such as drugs (including several different antiseizure drugs),
infections, maternal illnesses, maternal smoking and alcohol use
and, possibly, deficiency of the B vitamin folic acid may be
involved.
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Salivary Glands
Cleft Lip
Parotid – largest – watery (serous) type of saliva (enzymes/ NO mucus)
Cleft Palate
Submandibular – mixed (compound) glands - enzymes and mucus
Sublingual – smallest – only mucus
Teeth
Types of Teeth
Organs of mastication
32
20 “baby”
” teeth
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Pharynx
Only the
terminal
portion of the
pharynx
serves the
Digestive
System.
Esophagus
Trachea
Esophagus
The esophagus
begins as an
extension of the
pharynx in the back
of the oral cavity. It
then courses down
the neck next to the
trachea, through
the thoracic cavity,
and penetrates the
diaphragm to
connect with the
stomach in the
abdominal cavity.
The esophagus runs through the diaphragm to the stomach.
Esophagus
The surface of the
esophagus must be
resistant to trauma, and
is, therefore, lined with
stratified squamous
epithelium.
Esophageal hiatus
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Hiatal Hernia
Esophagus - Sphincters
Upper Esophageal Sphincter
The UES helps prevent air from entering during respiration.
When a hiatal hernia is present, part of the stomach moves up
through an enlarged hiatus in the diaphragm. The presence of a
hiatal hernia increases the risk for gastroesophageal reflux.
Esophagus - Sphincters
Lower Esophageal
Sphincter (LES) or
Cardiac Sphincter
Stomach
Great example of
structure-function!
The crisscrossing
pattern of muscle
fibers makes the
stomach a great mixer!
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Structure-Function continued …
Stomach
Gastric pits
depressions in the epithelial
lining of the stomach. At the
bottom of each pit is one or
more gastric glands:
•
•
•
Reservoir for stored food
Churns food
Secretes gastric juice:
Water, mucus, pepsin, HCl, and intrinsic factor
Parietal cells produce
•
stomach acid and intrinsic
factor.
•
HCl protects body from pathogenic bacteria which has been
swallowed
Intrinsic factor – binds to vitamin B12 molecules to protect
them from digestive juices until they reach the small intestine
Chief cells produce the
enzymes of gastric juice.
Endocrine cells secrete
the appetite-boosting hormone
ghrelin and the hormone
gastrin, which helps regulate
digestive function.
What is a Peptic Ulcer?
• sore on the lining of the stomach or duodenum
•
•
Produces hormones
Limited amount of absorption – certain drugs, some H2O,
alcohol, and some short-chain fatty acid's in butter or milk fat
Small Intestine
Helicobacter pylori (H. pylori) is the bacteria which
is believed to cause the majority of peptic ulcers.
Some ulcers are caused by long-term use of NSAID’s,
like aspirin and ibuprofen.
In a few cases, cancerous tumors
in the stomach or pancreas can
cause ulcers.
Peptic ulcers are not caused by
stress or eating spicy food, but
these can make ulcers worse.
The bulk of chemical digestion and
nutrient absorption occurs in the jejunum!
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Small Intestine
Great
example
of
structure
/function
!
Goblet Cells on villi and
in crypts secrete mucus.
Cells at the base of crypts
secrete bactericidal enzymes.
Brushborder
Arteriole & Venule
Large Intestine
Wall of the Large Intestine
The main function
of the large
intestine is
reabsorption of
water.
Produces the
lubricating mucus
that coats the feces
as they are formed.
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Colonoscopy
A test that allows your doctor to look at the inner lining of your
large intestine.
A barium enema (colon X-ray) is an X-ray exam that can detect
changes or abnormalities in the colon. An enema is the
injection of a liquid into your rectum through a small tube.
A 4-foot thin, flexible tube
called a colonoscope
is used to look at the
colon. The colonoscope
has a camera and a light
at its tip.
A colonoscopy can
help find ulcers,
colon polyps, tumors, and
areas of inflammation or
bleeding.
A well-lubricated enema tube is inserted gently into the rectum, and then
barium contrast material flows slowly into the colon. At certain times, Xray pictures called spot films will be taken of different areas of the colon.
Hemorrhoids are enlargements of the veins in the anal canal.
Rectum
Smooth muscle
Rubber Band Ligation for Hemorrhoids - 3D Medical Animation
Striated muscle
https://www.youtube.com/watch?v=z2hqoeS0oXA
Video Hemorrhoids rubber band ligation 1
https://www.youtube.com/watch?v=vT_AsC6qfuw
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Appendix
Peritoneum
A thin membrane that lines the
abdominal and pelvic cavities, and
covers most abdominal viscera.
The functions of the appendix are uncertain. Some scientists
believe it serves as a “breeding ground” for intestinal bacteria.
The non-pathogenic intestinal flora is thought to help prevent
disease and aid in digestion or absorption of essential nutrients.
Liver
• Removes toxic substances,
including alcohol, from
the blood.
Liver
Largest gland in the body!
• Secretes bile.
• Produces certain blood
proteins and serves as a site of
hematopoiesis in fetal development.
• Involved in the metabolism of carbohydrates, fats, and
proteins.
• Stores iron, and vitamins A, B12 and D.
The intestines are suspended from
the dorsal aspect of the peritoneal
cavity by a layer of peritoneum
called the mesentery. The
mesentery connects the small
intestine to the posterior
abdominal wall. It allows free
movement of each coil of the
intestine and helps prevent
strangulation of the long tube.
The liver’s functional units are
its lobules. Blood enters the
lobules through branches of
the portal vein and hepatic
artery, then flows through
small channels called
sinusoids that are lined with
primary liver cells (i.e., the
hepatocytes).
The hepatocytes remove toxic
substances from the blood,
which then exits the lobule
through the central vein (i.e.,
the hepatic venule).
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Liver
Bile is produced in the liver by the hepatocytes and secreted into thin channels
called bile canaliculi. The canaliculi are drained by bile ducts which then drain
into right and left hepatic ducts and eventually into one hepatic duct that
carries bile away from the liver. The hepatic duct merges with the cystic duct
from the gall bladder to form the common bile duct, which opens into the
duodenum.
Gallstones are crystallized bile
formed in the gallbladder due to an
excessive level of cholesterol in the bile.
These stones can travel and block the
flow of bile resulting in pain in the right
upper abdomen.
Gall Bladder
The gallbladder stores bile + concentrates it 5-10X. During digestion,
it contracts and ejects the concentrated bile into the duodenum
whenever fatty foods are eaten .
Jaundice – yellowish discoloration of the skin resulting from the
obstruction of bile flow into the duodenum. Because bile is not
allowed out in the feces, it is absorbed into the blood + bile pigments
are deposited in the tissues.
Pancreas
Endocrine gland:
Islets of Langerhans
produce hormones
It is also possible for a small stone to
lodge in the opening of the common bile
duct into the duodenum. This is a more
serious condition where the stone can
also block the flow of the pancreatic juice
from the pancreatic duct that joins the
common bile duct. This may result in
pancreatitis (inflammation of the
pancreas).
Gallbladder problems are very common
and if they cause pain, medical attention
is usually needed.
Alpha cells:
Glucagon - raises the
level of glucose in the
blood
Exocrine gland: Acini cells
produce digestive enzymes
Beta cells:
Insulin - stimulates
cells to use glucose
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