THE DIGESTIVE SYSTEM
also known as GI Tract
Accessory Digestive Organs includes
teeth, tongue, gallbladder,
salivary glands, liver and pancreas.
what are the 6 major digestive process
3. mechanical digestion
4. chemical digestion
taking food into the digestive tract (eating)
movement of food through the alimentary canal. This includes swallowing and peristalsis. (swallowing)
physically prepares food for chemical digestion. This includes chewing,
mixing of food with enzymes, churning food in the stomach and segmentation (rhythmic, local
constrictions of the intestines). (chewing)
Segmentation mixes food with digestive juices and it increase
the rate of absorption.
occurs as enzymes break down food materials into their primary
components. Much of this occurs in the lumen of the alimentary canal.
the passage of digested end products with vitamins, mineral and water, from the
lumen of the GI Tract into the blood or lymph.
the process through which indigestible wastes are removed from the body in the
form of feces.
covers the external surfaces of the digestive organs and the parietal peritoneum lines the body wall
is a serous membrane the covers the abdominopelvic cavity
Most of the digestive organs reside in the
double layer peritoneum that extends to the digestive organs from the body wall.
Mesentery functions by
providing routes for blood vessels, lymphatics and nerves to
reach the digestive viscera, holding organs in place and storing fat.
are covered by and held on place by mesentery
lose their mesentery and lie posterior to the peritoneum
Submucosal nerve plexus-
control smooth muscle in the mucosa
Myenteric nerve plexus-
GI tact motility
Hepatic portal circulation
–Drains nutrient-rich blood from digestive organs
–Delivers it to the liver for processing
Mucosa: three sub layers
Layers of the alimentary canal
Mucosa- associated lymphoid tissue
response outside the “gut brain”
what reflex involves
External stimuli (sight, smell, taste, thought, of food)
local (intrinsic) nerve plexus “only gut brain”
what reflex involve Internal (GI tract) stimuli
Three key concepts regulate GI activity
Mechanical and chemical stimuli
also known as the Visceral Peritoneum, this is the outermost,
around a digestive organ.
two major Nerve Plexuses found in the walls of the alimentary canal
the submucosal nerve plexus
the myenteric nerve plexus
The Submucosal Nerve Plexus
located in the submucosa, this nerve plexus generally
regulates the activity of glands and smooth muscle in the mucosa.
The Myenteric Nerve Plexus
lies in the smooth muscle of the muscularis externa.
a. Enteric neurons here regulate GI tract motility.
Associated organs include
Mouth consist of
Superior labial frenulum
Soft palate- close of the nasopharynx during swallowing
Oral vestibule – the lining of the tongue
The opening of the mouth
The Labial Frenulum
a fold of tissue that joins the internal aspect of each lip to
The Hard Palate
anterior portion, is supported by the palatine bones and the
palatine processes of the maxillae. This structure forms a thick structure
against which the tongue forces food against during chewing. The mucosa
on either side of the midline of the hard palate is corrugated which helps to
The Soft Palate
composed of mostly skeletal muscle.
a) The Uvula-projects downward from the free edge of the soft palate
Closes off nasopharynx during swallowing
Uvula projects downward from its free edge
what is composed of bundles of skeletal muscle fibers
what produce and secrete saliva into the oral cavity.
the salivary glands
Extrinsic Salivary Glands
lie outside of the oral cavity and empty their
secretions into it.
Intrinsic Salivary Glands
are scattered throughout the oral cavity mucosa
what salivary gland Scattered throughout oral cavity; augment slightly
minor salivary glands
what salivary glands
Produce most saliva; lie outside oral cavity
major salivary glands
The Major Extrinsic Salivary Glands include:
the parotid gland
the submandibular gland
the sublingual gland
The Parotid Gland
large, is anterior to the ear between the skin and
masseter muscle. Saliva is carried from this gland to the mouth via the
Parotid Duct which opens in the mouth near the second molar
Humans have two sets of teeth:
primary teeth ( baby or milk teeth)
Primary Teeth (Baby or Milk Teeth)
20 of these total. These loosen and
fall out between the ages of 6 and 12.
there are typically 32 teeth in the permanent set.
storage and chemical break down of proteins
Involves 22 muscles and occurs through two phases
. Buccal Phase
voluntary, occurs in the mouth. In this phase, the tongue contracts
push the bolus into the oropharynx. Deglutition becomes involuntary at this point.
controlled by the swallowing center in the medulla and
pons. When food enters the pharynx, breathing is temporarily stopped as: the tongue blocks
the mouth, the epiglottis covers the respiratory passages and the soft palate closes off the
When the stomach is empty, it collapses throwing its mucosa into
organ where chemical breakdown of proteins begins and food is
converted into a
material known as
Stores and concentrates bile by absorbing water and ions
what is CCK
primary pigment in bile. This is a waste product of the heme portion
what is actually a breakdown product of erythrocytes
small intestine consist of
what are the Unique features of the large intestine
the ascending colon
travels up the right side of the abdominal cavity to the level
of the right kidney where it makes a right-angle turn known as the right colic or
Anterior to the spleen, the transverse colon bends at the left
colic (splenic) flexure
descending colon enters the pelvis, where it becomes
Internal anal sphincter
smooth muscle: expansion
External anal sphincter
skeletal muscle: contraction
Vitamin K and B vitamins from bacterial metabolism are absorbed in what?
In large intestine
Most water absorbed in
small intestine ( absorption of water)
Most ions are transported actively along length of
small intestine ( absorption of electrolytes
Fat-soluble vitamins (A, D, E, and K)
Water-soluble vitamins (C and B)
Vitamin B12 binds with intrinsic factor
all of this are absorbed where?
small intestine ( vitamin absorption)
what break down to monosaccharide (starts with almysis) : enzyme starch and disaccharides
what start with the pepsin ( pitide)
what start with the lipase: ( liver) breakdown bio in the liver
what contain DNA and RNA ( start in the pancreas)