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Layers of Alimentary Canal Organs

Four layers

Mucosa

Submucosa

Muscularis externa

Serosa
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Structural Plan of the Digestive Tube
Wall Layer
Subdivision of the
layer
Major Functions
Mucosa
•
•
•
•
Surface epithelium
Lamina propria:
(connective tissue)
Smooth muscle layer
Submucosa
•
•
•
Connective tissue
Lymph nodules
Nerve Fibers
Protection
Muscularis externa
•
•
Circular muscular layer
Longitudinal muscle layer
Regulates GI Motility
Serosa
• Visceral peritoneum
•
•
Secretion of enzymes, mucus,
hormones, etc.
Absorption of digested
foodstuffs
Protection against bacterial
invasion
Reduces friction as the
GI tract organs work
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Organs of the Alimentary Canal
Alimentary canal:
continuous coiled hollow tube
From mouth to anus
Figure 14.1
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Stomach
Muscularis externa has a
third oblique layer in the
stomach in addition to the
longitudinal layer and the
circular layer.
The stomach is able to churn,
mix, and pummel the food,
physically breaking it down
into smaller pieces.
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Digestive System Terms
a.
Appendix: a narrow, blind tube protruding from the cecum, having no known useful function, in humans being 3 to 4 inches (8 to 10 cm) long and situated in the lower right-hand
part of the abdomen.
b.
Anus: the distal end of the alimentary canal.
c.
Esophagus: the part of the alimentary canal between the pharynx and the stomach; no digestive or absorptive role
d.
Frendulum: membrane securing the tongue to the floor of the mouth
e.
Greater omentum: a two-layered serous membrane attached to the greater curvature of the stomach
f.
Hard palate :the anterior portion of the palate, separating the oral and nasal cavities, consisting of the bony framework and covering membranes.
g.
Haustra: the small pouches caused by sacculation, which give the colon its segmented appearance
h.
Ileocecal valve: physiological sphincter muscle situated at the junction of the small intestine (ileum) and the large intestine, with recent evidence indicating an anatomical
sphincter may also be present in humans) Its critical function is to limit the reflux of colonic contents into the ileum
i.
Large intestine: organ distal to the small intestine
j.
Lesser omentum: a peritoneal fold joining the lesser curvature of the stomach and the first part of the duodenum to the porta hepatis.
k.
Mesentry: refers to the peritoneum responsible for connecting the jejunum and ileum (parts of the small intestine) to the back wall of the abdomen.
l.
Microvilli: surface projections of a mucosal epithelial cell; increases absorption
m.
Oral Cavity= another name for “mouth”; the first portion of the alimentary canal that receives food and saliva; Mastication (chewing) of food; Mixing masticated food with
saliva; Initiation of swallowing by the tongue; break down food mechanically
n.
Parietal peritoneum: the portion of the largest serous membrane in the body that lines the abdominal wall
o.
Peyer’s patches: one of a group of solitary nodules or groups of lymph nodes forming a single layer in the mucous membrane of the small intestine
p.
Pharynx: is the part of the throat situated immediately posterior to (behind) the mouth and nasal cavity, and superior to the esophagus and larynx. Common passage for
food and air
q.
Plicae circulares: the numerous permanent crescentic deep folds of mucous membrane found in the small intestine especially in the lower part of the duodenum and the
jejunum; increases absorption
r.
Pyloric sphincter (valve): The pyloric sphincter, or valve, is a strong ring of smooth muscle at the end of the pyloric canal which lets food pass from the stomach to the
duodenum.
s.
Rugae: large folds in the mucous membrane of the stomach.
t.
Small Intestine: part of the gastrointestinal tract following the stomach; bile produced by the liver and stored in the gallbladder, is secreted in the small intestine to assist in
the absorption of fats; digestion is completed and nutrients and water are absorbed by the blood; pancreatic juice is secreted via the pancreatic duct into duodenum.
u.
Soft palate: the fleshy part of the palate, extending from the posterior edge of the hard palate; the uvula projects from its free inferior border
v.
Stomach: Mechanically, the stomach churns and grinds the food into smaller and smaller pieces, turning it into a substance of nutrients and gastric juices known as chyme.
w.
Tongue: rolls the food into balls or boli (singular: 'bolus') and pushes them to the back of the mouth cavity for swallowing
x.
Vestibule: the portion of the oral cavity bounded on one side by the teeth and on the other side by the lips and cheeks.
y.
Villi: one of the minute fingerlike processes which more or less thickly cover and give a velvety appearance to the surface of the mucous membrane
of the small intestine and serve in the absorption of nutriment and of which each has a central blindly ending lacteal surrounded by blood capillaries
and covered with epithelium; increases absorption
z.
Visceral peritoneum: That portion of the peritoneum covering the organs of the abdominal cavity
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Digestive Structures
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Teeth
 Function is to masticate (chew) food
 Humans have two sets of teeth
 Deciduous (baby or “milk”) teeth
 20 teeth are fully formed by age two
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Teeth
 Permanent teeth
 Replace deciduous teeth between the ages of
6 and 12
 A full set is 32 teeth, but some people do not
have wisdom teeth (third molars)
 If they do emerge, the wisdom teeth appear
between ages of 17 and 25
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Classification of Teeth
 Incisors—cutting
 Canines—tearing or piercing
 Premolars—grinding
 Molars—grinding
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Human Deciduous and Permanent Teeth
Figure 14.9
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Regions of a Tooth
 Crown—exposed part
 Enamel—hardest substance in the body
 Dentin—found deep to the enamel and forms
the bulk of the tooth
 Pulp cavity—contains connective tissue,
blood vessels, and nerve fibers
 Root canal—where the pulp cavity extends
into the root
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Regions of a Tooth
 Neck
 Region in contact with the gum
 Connects crown to root
 Root
 Cementum—covers outer surface and
attaches the tooth to the periodontal
membrane
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Regions of a Tooth
Figure 14.10
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The Digestive System Functions
 Ingestion—taking in food
 Digestion—breaking food down both physically
and chemically
 Absorption—movement of nutrients into the
bloodstream
 Defecation—rids the body of indigestible waste
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Organs of the Digestive System
 Two main groups
 Alimentary canal (gastrointestinal or GI
tract)—continuous coiled hollow tube
 Accessory digestive organs
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Organs of the Alimentary Canal
 Mouth
 Pharynx
 Esophagus
 Stomach
 Small intestine
 Large intestine
 Anus
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Mouth (Oral Cavity) Anatomy
 Lips (labia)—protect the anterior opening
 Cheeks—form the lateral walls
 Hard palate—forms the anterior roof
 Soft palate—forms the posterior roof
 Uvula—fleshy projection of the soft palate
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Mouth (Oral Cavity) Anatomy
 Vestibule—space between lips externally and
teeth and gums internally
 Oral cavity proper—area contained by the teeth
 Tongue—attached at hyoid bone and styloid
processes of the skull, and by the lingual
frenulum to the floor of the mouth
 Tonsils
 Palatine
 Lingual
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Mouth (Oral Cavity) Anatomy
Figure 14.2a
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Mouth (Oral Cavity) Anatomy
Figure 14.2b
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Mouth Physiology
 Mastication (chewing) of food
 Mixing masticated food with saliva
 Initiation of swallowing by the tongue
 Allows for the sense of taste
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Pharynx Anatomy
 Nasopharynx—not part of the digestive system
 Oropharynx—posterior to oral cavity
 Laryngopharynx—below the oropharynx and
connected to the esophagus
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Pharynx Anatomy
Figure 14.2a
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Pharynx Physiology
 Serves as a passageway for air and food
 Food is propelled to the esophagus by two
muscle layers
 Longitudinal inner layer
 Circular outer layer
 Food movement is by alternating contractions of
the muscle layers (peristalsis)
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Esophagus Anatomy and Physiology
 Anatomy
 About 10 inches long
 Runs from pharynx to stomach through the
diaphragm
 Physiology
 Conducts food by peristalsis (slow rhythmic
squeezing)
 Passageway for food only (respiratory system
branches off after the pharynx)
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Layers of Alimentary Canal Organs
 Mucosa
 Innermost, moist membrane consisting of
 Surface epithelium
 Small amount of connective tissue
(lamina propria)
 Small smooth muscle layer
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Layers of Alimentary Canal Organs
Figure 14.3
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Layers of Alimentary Canal Organs
 Submucosa
 Just beneath the mucosa
 Soft connective tissue with blood vessels,
nerve endings, and lymphatics
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Layers of Alimentary Canal Organs
Figure 14.3
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Layers of Alimentary Canal Organs
 Muscularis externa—smooth muscle
 Inner circular layer
 Outer longitudinal layer
 Serosa—outermost layer of the wall contains
fluid-producing cells
 Visceral peritoneum—outermost layer that is
continuous with the innermost layer
 Parietal peritoneum—innermost layer that
lines the abdominopelvic cavity
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Layers of Alimentary Canal Organs
Figure 14.3
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Alimentary Canal Nerve Plexuses
 Two important nerve plexuses serve the
alimentary canal
 Both are part of the autonomic nervous system
 Submucosal nerve plexus
 Myenteric nerve plexus
 Function is to regulate mobility and secretory
activity of the GI tract organs
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