Download Digestive Anatomy

The Digestive System
“alimentary canal”
Overall Function
Digestion is the
chemical and
physical
breakdown of
food into a
form usable by
cells.
Organs of Digestive System
MAJOR ORGANS
• Mouth
• Oropharynx
• Esophagus
• Stomach
• Small intestine
• Large intestine
• Rectum
ACCESSORY ORGANS
• salivary glands
• Tongue
• Teeth
• Liver
• Gallbladder
• Pancreas
• Vermiform appendix
Digestive Tract
Also known as
alimentary canal or
gastrointestinal (GI)
tract.
It forms a tube that
separates from
digesting food from
the body’s internal
cavity.
Layers of GI tract
Mucosa
– Inner layer of the lumen
(open space)
Submucosa
– Made of connective tissue,
glands, blood vessels and
nerves
Muscularis
– Surrounds submucosa,
smooth muscle that
contains nerves that form
part of the intramural plexus
Serosa
– Outermost layer made of
connective tissue
The Mouth
• Lips
– When closed form
the oral fissure
• Cheeks
– Formed by muscle
and adipose tissue
• Hard & soft palate
– Uvula suspends from
soft palate
• Tongue
– Muscle movements
aid in mastication
The Mouth
Salivary Glands
• Pairs include
parotids,
submandibular, and
sublingual
• Secrete ~1L of saliva
per day
• Buccal glands in the
mucosa lining
produces a small
amount of saliva
The Teeth
• Three main parts
– Crown
– Neck
– Root
• Deciduous teeth(20) are baby teeth
• Permanent teeth(32) show up from 613 yrs
The Pharynx
• Deglutition is the act of swallowing a bolus,
rounded mass of food and saliva from the
mouth to the stomach.
The Esophagus
• ~10 inches longs
• Sits posterior to trachea and
heart
• It is normally flatted in resting
state
• Each end is guarded be a
sphincter
– Upper esophageal (UES)
– Lower (cardiac) esophageal
(LES)
• Esophageal hiatus is opening in
diaphragm where esophagus
passes
– When enlarged can lead to
hiatal hernia
GERD- gastro esophageal reflux
disorder, severe acid reflux and
indigestion caused by
weakened LES.
The Stomach
• Located directly below
the diaphragm
• Normally holds 1-1.5 L
• 3 parts
Esophageal
hiatis
fundus
– Fundus (upper left)
– Body (central)
– Pyloris (lower)
body
• 2 sphincter
– LES(cardiac)
– Pyloric
pyloris
The Stomach
• Gastric Mucosa, lining
of the stomach contain
many folds called
rugae and depression
called gastric pits
• Cells in the stomach
produce HCL and
intrinsic factor
• Intrinsic factor binds to
B12 molecules keeping
them from being
broken down so they
can be absorbed in the
sm. Intestines
The Stomach
• Gastric muscles,
muscularis, is made of
longitudinal, circular and
oblique layers. This gives it
strong grinding power.
The Stomach
Overall Functions
• Secrete gastric juices and
intrinsic factor
• Store partially digested food
• Churn food with digestive
juices and move it into
duodenun
• Limited absorption, alcohol,
some H2O and some fats
• Release hormones that
regulate digestive functions
• Destroy pathogenic
bacteria
The Small Intestine
• ~6m in length
• 3 parts
– Duodenum- first section,
shaped like a C
– Jejunum- 2.5m, begins with
abrupt turn
– Ileium- last 3.5m
• Small projections called villi
line the sm. Intestine.
– Each contain an arteriole,
venuole and lacteal
• Microvilli present on the villi
increase the surface area of
intestinal wall
The Small Intestine
• Secretion of digestive
enzymes and
absorption occur in
small intestine
• Small pockets at the
base of the villi, called
crypts, contain cells
that reproduce rapidly
• These cells push up
and constantly replace
older cells that are
shed
Large Intestine
• 1.5-1.8m
• 3 parts
– Cecum- first 5-8cm
– Colon
• Ascending
• Transverse
• Descending
• Sigmoid (s-shaped)
– Rectum17-20cm
• Anal canal has folds with a vein and artery
• Hemorrhoids are enlargement of those veins
– Anus is made up of two sphincters
The Large Intestines
Accessory Structures
• Vermiform appendixthought to hold beneficial
flora
• Peritoneum- serous
membrane that lines
abdominal cavity
• Mesentery- fan shaped part
of peritoneum which
attaches to small intestine
• Omentum- attached to
greater curvature of the
stomach and is laced with
fat deposits
The Liver
• Weighs ~1.5kg
• Made of two lobes
– Left lobe is smaller
– Right lobe has 4
parts
• Liver is made of
small units called
hepatic lobules
The Liver
• Blood enters the
lobules from the
hepatic portal system
to be “cleaned”
• The liver:
– Destroys old RBCS,
bacteria
– Vitamins and
nutrients are
metabolized
– Toxins are absorbed
and detoxified
– Bile formed collects
in small bile ducts
Bile Ducts
• The right and left bile
ducts emerge from
under the liver to form
the common hepatic
duct
• The common hepatic
duct joins with the
cystic duct
(gallbladder) to form
the common bile duct
• Common bile duct
empties into the
duodenum
Function of the Liver
• Detoxify substancealcohol, medicines
• Bile production
• Metabolize fats,
proteins and
carbohydrates
• Store substancesFe, vitamins A, B12, D
• Bile salt released by
liver aid in
absorption of fats
Gall Bladder
• Main function is to store
and concentrate bile
• Contain tiny folds of
rugae that contract to
secrete bile during
digestion
• Jaudice is caused by a
buildup of bile in the
blood
• Cholelithiasis is the
formation of gallstones
Pancreas
• Fish shaped textured
organ that is exocrine
and endocrine gland
• Rests below stomach on
top of duodenum
• Exocrine portion secrete
digestive enzymes that
collect in the pancreatic
duct, that joins the
common bile duct
• Endocrine islets cells
secrete insulin and
glucagon directly into
the blood