Transcript Alimentary canal

Essentials of Human Anatomy & Physiology
Seventh Edition
Elaine N. Marieb
Chapter 14
The Digestive System
Anatomy
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Organs of the Digestive System
 Two main groups
 Alimentary canal (Gastrointestinal (GI) tract)–
continuous, coiled, hollow, muscular tube that
ingests, digests, absorbs, and defecates and
is open on both ends; about 30 feet long
 Accessory digestive organs – assist the
process of digestive breakdown in various
ways
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Slide 14.2a
Organs of the Digestive System (Know this!)
Figure 14.1
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Slide 14.2b
Organs of the Alimentary Canal
 Mouth
 Pharynx
 Esophagus
 Stomach
 Small intestine
 Large intestine
 Anus
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Slide 14.3
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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Figure 14.2a
Slide 14.4
Mouth (Oral Cavity) Anatomy
 Vestibule – space
between lips and
cheeks externally
and teeth and gums
internally
 Oral cavity proper –
area contained by
the teeth
 Tongue –muscular;
occupies floor of
mouth; attached to
floor of mouth by the
lingual frenulum
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Figure 14.2a
Slide 14.5
Mouth (Oral Cavity) Anatomy
Slide 14.5
 Children born with an extremely short
frenulum are referred to as “tongue-tied”
because distorted speech results when
tongue movement is restricted.
 This can be corrected surgically by cutting
the frenulum.
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Mouth (Oral Cavity) Anatomy
 Tonsils: masses
of lymphatic
tissue
 Palatine tonsils
 Lingual tonsil-at
base of tongue
 Inflamed tonsils
make swallowing
difficult and painful
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Slide 14.6
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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Figure 14.2a
Slide 14.8
Layers of Alimentary Canal Organs
Figure 14.3
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Slide 14.13
Layers of Alimentary Canal Organs
 The walls of the alimentary canal organs from
the esophagus to the large intestine are made
up of the same four basic tissue layers (tunics):
1. Mucosa
 Innermost layer
 Moist membrane
 Surface epithelium
 Small amount of connective tissue
(lamina propria)
 Small smooth muscle layer
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Slide 14.11a
Layers of Alimentary Canal Organs
2. Submucosa
 Just beneath the mucosa
 Soft connective tissue with blood vessels,
nerve endings, and lymphatics
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Slide 14.11b
Layers of Alimentary Canal Organs
3. Muscularis externa – smooth muscle
 Inner circular layer
 Outer longitudinal layer
4. Serosa
 Outermost layer – visceral peritoneum,
which is continuous with parietal
peritoneum by way of the mesentery
 Layer of serous fluid-producing cells
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Slide 14.12
Layers of Alimentary Canal Organs
Figure 14.3
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Slide 14.13
Esophagus (Gullet)
 Runs from pharynx to stomach through
the diaphragm
 About 10 inches long
 Conducts food by peristalsis
(slow rhythmic squeezing)
 Passageway for food only (respiratory
system branches off after the pharynx)
 No serous lining on the esophagus
Stomach Anatomy
 C-shaped
 Located on the left side of the
abdominal cavity
 Can hold about 1 gallon of food when
full
 Food enters at the cardioesophageal
sphincter
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Slide 14.15a
Stomach Anatomy
 Regions of the stomach
 Cardiac region – near the heart
 Fundus – expanded part lateral to cardiac
region
 Body -- midportion
 Pylorus – funnel-shaped terminal end
 Food empties into the small intestine at
the pyloric sphincter
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Slide 14.15b
Stomach Anatomy
Antrum
Figure 14.4a
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Slide 14.17
Stomach Anatomy
 Rugae – internal folds of the mucosa
 External regions
 Lesser curvature: concave medial surface
 Greater curvature: convex lateral surface
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Slide 14.16a
Specialized Mucosa of the Stomach
 Simple columnar epithelium
 Mucous neck cells – produce a sticky alkaline
mucus (glycoprotein) protects the stomach wall
from being damaged
 Gastric glands in gastric pits – secrete gastric
juice
 Chief cells – produce protein-digesting enzymes
(pepsinogens)
 Parietal cells – produce hydrochloric acid that
makes the stomach contents acidic and activates
the enzymes (located only in the fundus and the
body)
 Endocrine cells – produce gastrin
Structure of the Stomach Mucosa
Stomach mucosa
looks like moist
velvet to the
naked eye.
Figure 14.4b, c
Stomach Anatomy
 Layers of peritoneum attached to the
stomach
 Lesser omentum – attaches the liver to the
lesser curvature
 Greater omentum – attaches the greater
curvature to the posterior body wall
 Contains fat to insulate, cushion, and
protect abdominal organs
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Slide 14.16b
Small Intestine
 The body’s major digestive organ
 Longest section of the alimentary tube,
with an average length of 6-13 feet
 Site of nutrient absorption into the blood
 Muscular tube extending form the
pyloric sphincter to the ileocecal valve
 Suspended from the posterior
abdominal wall by the mesentery
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Slide 14.21
Subdivisions of the Small Intestine
 Duodenum
 Attached to the stomach
 Curves around the head of the pancreas
(retroperitoneal)
 Pyloric sphincter controls food movement
into the duodenum
 Jejunum
 Attaches anteriorly to the duodenum
 Ileum
 Extends from jejunum to large intestine
Folds of the Small Intestine
 Called circular folds or plicae circulares
 Deep folds of the mucosa and
submucosa
 Do not disappear when filled with food
 The submucosa has Peyer’s patches
(collections of lymphatic tissue that
prevent bacteria from entering the
bloodstream)
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Slide 14.27
Villi of the Small Intestine
 Fingerlike
structures formed
by the mucosa
 Give the small
intestine more
surface area for
absorption
Figure 14.7a
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Slide 14.24
Microvilli of the Small Intestine
 Small projections of the
plasma membrane of the
mucosa cells
 Also known as the brush
border
 Found on absorptive cells
Figure 14.7c
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Slide 14.25
Structures Involved in Absorption of
Nutrients
 Absorptive cells
 Blood capillaries
 Lacteals (specialized
lymphatic capillaries)
Figure 14.7b
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Slide 14.26
Large Intestine
 Larger in diameter, but shorter in length
than the small intestine
 About 5 feet
 Extends from ileocecal valve to anus
 Frames the internal abdomen
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Slide 14.28
Large Intestine
Figure 14.8
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Slide 14.28
Structures of the Large Intestine
 Cecum – saclike first part of the large
intestine
 Appendix
Accumulation of lymphatic tissue that
sometimes becomes inflamed
(appendicitis)
Hangs from the cecum
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Slide 14.30a
Structures of the Large Intestine
 Colon
 Ascending colon: travels up the right side of
the abdominal cavity and makes a turn at the
right colic flexure
 Transverse colon: leads transversely to left
colic flexure
 Descending colon: descends down left side
 Sigmoid colon: S-shaped; in pelvis
 Rectum
 Anal Canal – external body opening; has an
external voluntary sphincter and an internal
involuntary sphincter; ends in anus
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Slide 14.30b
Coverings of the Digestive System
 Peritoneum (AKA - Mesentery)
 Two serous tissue layers with fluid between
the layers
 Parietal peritoneum – in contact with the
abdominal wall
 Visceral peritoneum – in contact with the
digestive organs
peritoneum
Mesenteries
Accessory Digestive Organs Notes
 Salivary glands
 Teeth
 Pancreas
 Liver
 Gallbladder
Slide 14.32
Salivary Glands
 Saliva-producing glands
 Three pairs
 Parotid glands – located anterior to ears
 Mumps (viral disease that spreads
through saliva) is an inflammation of the
parotid glands (child looks like a
“hampster with food in its cheeks”)
 Submandibular glands
 Sublingual glands
Slide 14.33
Slide 14.33
Salivary Glands
Mumps
Teeth
 The role is to masticate (chew) food,
tearing and grinding the food into
smaller fragments
 Humans have two sets of teeth
 Deciduous (baby or milk) teeth
 Begin to erupt around six months
 20 teeth are fully formed by age two
 Lower central incisors appear first
Slide 14.35a
Teeth
 Permanent teeth
 Replace deciduous teeth between the ages of
6 and 12
 As permanent teeth enlarge and develop, the
roots of deciduous teeth are reabsorbed
 By the end of adolescence, all the permanent
teeth but the third molars (“wisdom teeth”)
have erupted (making a total of 28 teeth)
 Third molars erupt between the ages of 17
and 25
 A full set is 32 teeth, but some people do not
have third molars
Slide 14.35b
Impacted Teeth
Slide 14.35b
 Occurs when teeth remain embedded in
jawbone
 Exert pressure, cause pain, and must be
removed surgically
 Third molars are the most commonly impacted
teeth
Classification of Teeth
 Incisors: chisel-shaped,
adapted for cutting
 Canines (cuspids):
fanglike, “eyeteeth,” for
tearing or piercing
 Premolars (bicuspids):
broad crowns with rounded
cusps for grinding
 Molars: broad crowns with
rounded cusps for grinding
Classification of Teeth
Figure 14.9
Slide 14.36b
Regions of a Tooth
 Crown – exposed part
(above gingiva)
 Outer enamel
 Dentin-forms bulk of
tooth
 Pulp cavity-has
blood vessels and
nerve fibers;
supplies nutrients to
the tooth and
provides for tooth
sensations
Figure 14.10
Slide 14.37a
Regions of a Tooth
 Neck
 Region in contact
with the gum
 Connects crown to
root
Figure 14.10
Slide 14.37a
Regions of a Tooth
 Root
 Embedded in
jawbone
 Covered with
cementum
 Periodontal
membrane
(ligament) attaches
tooth to the jaw bone
 Root canal carrying
blood vessels and
nerves
Figure 14.10
Slide 14.37b
Slide 14.38
Pancreas (all – flesh)
 Soft, pink, triangular gland; retroperitoneal
 Produces a wide spectrum of digestive
enzymes that break down all categories of food
 Enzymes are secreted into the duodenum
 Alkaline fluid introduced with enzymes
neutralizes acidic chyme
 Endocrine products of pancreas
 Insulin (Beta Cells)
 Glucagon (Alpha Cells)
Slide 14.38
Liver
 Largest gland in the body
 Located on the right side of the body
under the diaphragm
 Consists of four lobes suspended from
the diaphragm and abdominal wall by
the falciform ligament
 Connected to the gallbladder via the
common hepatic duct
 Produces bile, which emulsifies fats
Slide 14.39
Gall Bladder
 Small, thin-walled green sac found in hollow fossa of
liver
 Stores bile from the liver by way of the cystic duct
 Bile is introduced into the duodenum in the presence
of fatty food
 Gallstones (when cholesterol in bile crystallizes
because it is stored too long) can cause blockages.
This backs up the liver, causing bile pigments to
enter the bloodstream. Tissues become jaundiced.
 Hepatitis or cirrhosis (inflammation of liver) can also
cause jaundice
Slide 14.41
Slide 14.38