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prepared by Leslie Hendon,
University of Alabama,
Birmingham
22
HUMAN
ANATOMY
PART 1
The Digestive
System
fifth edition
MARIEB | MALLATT | WILHELM
Copyright © 2008 Pearson Education, Inc.,
publishing as Benjamin Cummings
Overview of the Digestive System

Organs are divided into two groups
 Alimentary canal
 Mouth, pharynx, and esophagus
 Stomach, small intestine, and large intestine
 Accessory digestive organs
 Teeth and tongue
 Gallbladder, salivary glands, liver, and pancreas
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
The Alimentary Canal and Accessory Digestive Organs
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Figure 22.1
Digestive Processes


Ingestion – occurs in the mouth
Propulsion – movement of food
 Peristalsis – major means of propulsion

Mechanical digestion – prepares food for
chemical digestion
 Chewing, churning of food in stomach,
segmentation
 Segmentation is rhythmic local constrictions of
intestine
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Digestive Processes

Chemical digestion – complex molecules broken
down to chemical components
 Mouth
 Stomach
 Small intestine


Absorption – transport of digested nutrients
Defecation – elimination of indigestible
substances as feces
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Digestive Processes
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 22.2
Peristalsis


Major means of
propulsion
Adjacent segments of
the alimentary canal
relax and contract
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Figure 22.3a
Segmentation


Rhythmic local
contractions of the
intestine
Mixes food with
digestive juices
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Figure 22.3b
Abdominal Regions

Four lines divide abdominal wall into 9 regions
 Midclavicular lines – vertical lines of grid
 Subcostal plane – superior horizontal line
 Connects inferior
points of costal margin
 Transtubercular plane – inferior horizontal line
 Connects tubercles of iliac crests
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Nine Regions of Anterior Abdominal Surface
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Figure 22.4a
Nine Regions of Anterior Abdominal Surface

How regions relate to abdominal viscera
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Figure 22.4b
Abdominal Quadrants

A simpler scheme defining four quadrants
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Figure 22.4c
Mesenteries

Lesser omentum attaches to lesser curvature of
stomach
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Figure 22.10b
Mesenteries


Greater omentum –
a “fatty apron” of
peritoneum
Greater omentum and
transverse colon
reflected
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Figure 22.10c
Mesenteries


Sagittal section through
the abdominopelvic
cavity
Mesenteries attach to
posterior abdominal
wall
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Figure 22.10d
Secondarily Retroperitoneal Organs


Initially formed within peritoneum
Become retroperitoneal
 Fuse to posterior abdominal wall
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Figure 22.11
Summary of Intraperitoneal and
Secondarily Retroperitoneal Organs
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Table 22.1
The Mouth and Associated Organs

The mouth – oral cavity
 Mucosal layer
 Stratified squamous epithelium
 Lamina propria

The lips and cheeks
 Formed from orbicularis oris and buccinator
muscles, respectively
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Anatomy of the Mouth
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Figure 22.12a
Anatomy of the Mouth

The labial frenulum
 Connects lips to gum

The palate
 Forms the roof of the
mouth
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Figure 22.12b
The Tongue






Interlacing fascicles of skeletal muscle
Grips food and repositions it
Helps form some consonants
Intrinsic muscles – within the tongue
Extrinsic muscles – external to the tongue
Lingual frenulum
 Secures tongue to floor of mouth
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The Superior Surface of the Tongue

Tongue papillae
 Filiform papillae – no taste buds
 Fungiform papillae
 Circumvallate papillae

Sulcus terminalis
 Marks border between mouth and pharynx

Posterior 1/3 of tongue lies in oropharynx
 Lined with lingual tonsil
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Superior Surface of the Tongue
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Figure 22.13
The Teeth

Deciduous teeth – 20 teeth
 First appear at 6 months of age

Permanent teeth – 32 teeth
 Most erupt by the end of adolescence

Dental formula – shorthand
 Way to indicate number and position of teeth
 2I, 1C, 2P, 3M
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The Teeth
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Figure 22.14
Tooth Structure

Longitudinal
section of tooth in
alveolus
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Figure 22.15
The Salivary Glands


Produce saliva
Compound tubuloalveolar glands
 Parotid glands
 Parotid duct – parallel to zygomatic arch
 Contains only serous cells
 Submandibular glands
 Lies along medial surface of mandible
 Sublingual glands
 Lies in floor of oral cavity
 Contains primarily mucous cells
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The Salivary Glands
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Figure 22.16
The Pharynx

Oropharynx and laryngopharynx
 Passages for air and food
 Lined with stratified squamous epithelium
 External muscle layer
 Consists of superior, middle, and inferior pharyngeal
constrictors
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The Esophagus

Gross anatomy – muscular tube
 Begins as a continuation of the pharynx
 Joins the stomach inferior to the diaphragm
 Cardiac sphincter – closes lumen to prevent
stomach acid from entering esophagus
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
The Esophagus

Microscopic anatomy
 Epithelium is stratified squamous epithelium
 When empty – mucosa and submucosa in
longitudinal folds
 Mucous glands – primarily compound
tubuloalveolar glands
 Muscularis externa
 Skeletal muscle first third of length
 Adventitia – most external layer
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Microscopic Structure of the Esophagus
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Figure 22.17a, b
The Stomach


Site where food is churned into chyme
Secretion of pepsin begins protein digestion
 Functions under acidic conditions

Food remains in stomach approximately 4 hours
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The Stomach
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Figure 22.18a
The Stomach
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Figure 22.18b
Microscopic Anatomy of the Stomach

Muscularis has three layers
 Circular and longitudinal layers and oblique layer


Epithelium is simple columnar epithelium
Mucosa dotted with gastric pits
 Gastric glands – deep to gastric pits
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Microscopic Anatomy of the Stomach

Gastric glands of fundus and body
 Mucous neck cells
 Secrete a special mucus
 Parietal (oxyntic) cells
 Secrete hydrochloric acid and gastric intrinsic factor
 Chief (zymogenic) cells
 Secrete pepsinogen
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The Stomach – Microscopic Anatomy
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Figure 22.19a–d
The Small Intestine – Gross Anatomy



Longest portion of the alimentary canal
Site of most enzymatic digestion and absorption
Three subdivisions
 Duodenum
 Jejunum
 Ileum
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The Duodenum


Receives digestive enzymes and bile
Main pancreatic duct and common bile duct
enter duodenum
 Sphincters control entry of bile and pancreatic
juices
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The Duodenum and Related Organs
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Figure 22.20
The Small Intestine – Microscopic Anatomy

Modifications for absorption
 Circular folds (plicae circulares)
 Transverse ridges of mucosa and submucosa
 Villi
 Finger-like projections of the mucosa
 Covered with simple columnar epithelium
 Microvilli
 Further increase surface area for absorption
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Histology of the Intestinal Wall

Absorptive cells
 Uptake digested nutrients

Goblet cells
 Secrete mucus that lubricates chyme

Enteroendocrine cells
 Secrete hormones

Intestinal crypts
 Epithelial cells secrete intestinal juice
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The Small Intestine – Structural Features
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Figure 22.21a–d
The Large Intestine



Digested residue contains few nutrients
Small amount of digestion by bacteria
Main functions
 Absorb water and electrolytes

Mass peristaltic movements force feces toward the
rectum
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Gross Anatomy of Large Intestine

Subdivided into
 Cecum, vermiform appendix, colon, rectum, anal
canal

Special features of large intestine
 Teniae coli
 Thickening of longitudinal muscularis
 Haustra
 Puckering created by teniae coli
 Epiploic appendages
 Fat-filled pouches of visceral peritoneum
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Gross Anatomy of Large Intestine

Cecum
 Blind pouch
 Beginning of large intestine

Vermiform appendix
 Contains lymphoid tissue
 Neutralizes pathogens

Colon
 Divided into distinct segments
 Ascending, transverse, descending, and sigmoid
colon
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Gross Anatomy of Large Intestine

Rectum
 Descends along the inferior half of the sacrum

Anal Canal
 The last subdivision of the large intestine
 Lined with stratified squamous epithelium
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Gross Anatomy of Large Intestine
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Figure 22.22a
Gross Anatomy of Large Intestine
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Figure 22.22b
Vessels and Nerves of the Large Intestine

First half of large intestine
 Arterial supply - superior mesenteric artery
 Innervation
 Sympathetic innervation – superior mesenteric and
celiac ganglia
 Parasympathetic innervation – vagus nerve
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Vessels and Nerves of the Large Intestine

Distal half of large intestine
 Arterial supply - inferior mesenteric artery
 Innervation
 Sympathetic innervation – inferior mesenteric and
hypogastric plexuses
 Parasympathetic innervation – pelvic splanchnic
nerves
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Defecation Reflex
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Figure 22.23
Microscopic Anatomy of Large Intestine




Villi are absent
Contains numerous goblet cells
Intestinal crypts – simple tubular glands
Lined with simple columnar epithelial tissue
 Epithelium changes at anal canal
 Becomes stratified squamous epithelium
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Mucosa of the Large Intestine
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Figure 22.24
The Liver

Largest gland in the body
 Performs over 500 functions
 Digestive function
 Bile production
 Performs many metabolic functions
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Visceral Surface of the Liver
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Figure 22.26
Microscopic Anatomy of the Liver


Hepatocyte – functional cells of the liver
Portal triad composed of
 Bile duct tributary
 Branch of hepatic portal vein
 Branch of hepatic artery

Kupffer cells – destroy bacteria
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Microscopic Anatomy of the Liver

Some functions of hepatocytes
 Rough ER manufactures blood proteins
 Smooth ER produces bile salts, detoxifies poisons
 Peroxisomes detoxify poisons (alcohol)
 Golgi apparatus packages secretory products
 Mitochondria provide energy for liver processes
 Glycosomes store sugar
 Great capacity for regeneration
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Microscopic Anatomy of Liver
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Figure 22.27a, c, d
The Gallbladder


Stores and concentrates bile
Expels bile into duodenum
 Bile emulsifies fats

Cholecystokinin – released from enteroendocrine
cells in response to fatty chyme
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The Gallbladder
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Figure 22.20
The Pancreas

Exocrine function
 Acinar cells make, store, and secrete pancreatic
enzymes
 Enzymes are activated in the duodenum

Endocrine function
 Produces insulin and glucagon
 Regulates blood sugar
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The Exocrine Pancreas: Histology
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Figure 22.29a, b
Disorders of the Digestive System

Intestinal obstruction
 Mechanical obstructions
 Adhesions, tumors, or foreign objects
 Nonmechanical obstruction
 Halt in peristalsis
 Trauma
 Intestines touched during surgery
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Disorders of the Digestive System

Inflammatory bowel disease
 Inflammation of intestinal wall
 Crohn’s disease
 Ulcerative colitis

Viral hepatitis
 Jaundice and flu-like symptoms
 Major types – A, B, C, and G
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Disorders of the Digestive System

Cystic Fibrosis and the Pancreas
 Pancreatic ducts become blocked with mucus
 Clogged ducts prevent pancreatic juices from
entering small intestine
 Leads to malabsorption of fats and other nutrients
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Embryonic Development of the Digestive System

Alimentary canal formed in week three
 Encloses tubular portion of yolk sac

Vitelline duct
 Landmark dividing into three regions
 Forgut
 Midgut
 Hindgut
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