Download Chapter 22 Lecture Presentation, Part 2

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prepared by Leslie Hendon,
University of Alabama,
Birmingham
22
HUMAN
ANATOMY
PART 2
The Digestive
System
fifth edition
MARIEB | MALLATT | WILHELM
Copyright © 2008 Pearson Education, Inc.,
publishing as Benjamin Cummings
Histology of the Alimentary Canal Wall

Same four layers from esophagus to anus
 The mucosa – innermost layer
 Consists of
 Epithelium
 Lamina propria
 Muscularis mucosae

The submucosa – external to the mucosa
 Contains blood and lymphatic vessels, nerve fibers
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Histology of the Alimentary Canal Wall

The muscularis externa – external to the
submucosa
 Two layers
 Circular muscularis – inner layer
 Longitudinal muscularis – outer layer
 The serosa – the outermost layer
 Is the visceral peritoneum
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Histology of the Alimentary Canal
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 22.5
Smooth Muscle




Primarily found in walls of viscera
Fibers elongated
Have one centrally-located nucleus
Grouped into sheets
 Longitudinal layer – parallel to long axis of organ
 Circular layer – deeper layer, fibers run around
circumference of organ
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Smooth Muscle
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Figure 22.6a, b
Smooth Muscle Contraction


Myofilaments
operate by
interaction with
cytoskeleton
Dense bodies –
correspond to Zdiscs of skeletal
muscle
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Figure 22.7a–c
Innervation of Smooth Muscle


Innervated by ANS
Few fibers per sheet innervated
 Sheet of smooth muscle contracts as a unit
 Exceptions
 Iris of eye
 Arrector pili muscles in skin
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Innervation of Smooth Muscle
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Figure 22.8
Nerve Plexuses

Myenteric nerve plexus
 Lies between circular and longitudinal muscularis
 Controls peristalsis and segmentation

Submucosal nerve plexus
 Lies in submucosa
 Signals glands to secrete

Innervation
 Sympathetic and parasympathetic motor fibers
 Visceral sensory fibers
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The Peritoneal Cavity and Peritoneum

Peritoneum – a serous membrane
 Visceral peritoneum – surrounds digestive organs
 Parietal peritoneum – lines the body wall

Peritoneal cavity – a slit-like potential space
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The Peritoneal Cavity and Peritoneum

Mesentery – a double
layer of peritoneum
 Holds organs in place
 Sites of fat storage
 Provides a route for
circulatory vessels and
nerves
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Figure 22.9a
The Peritoneal Cavity and Peritoneum

Retroperitoneal organs
 Behind the peritoneum

Peritoneal organs
 Digestive organs that
keep their mesentery
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Figure 22.9b
Mesenteries

Superficial view of abdominal organs
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Figure 22.10a
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
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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