Transcript The Digestive System - Fullfrontalanatomy.com

PowerPoint® Lecture Slides
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
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
The Alimentary Canal and Accessory Digestive Organs
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Figure 22.1
Segmentation


Rhythmic local
contractions of the
intestine
Mixes food with
digestive juices
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Figure 22.3b
Peristalsis


Major means of
propulsion
Adjacent segments of
the alimentary canal
relax and contract
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Figure 22.3a
Digestive Processes
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Figure 22.2
Secondarily Retroperitoneal Organs


Initially formed within peritoneum
Become retroperitoneal
 Fuse to posterior abdominal wall
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Figure 22.11
Mesenteries




Sagittal section through the
abdominopelvic cavity
Mesenteries attach to
posterior abdominal wall
The mesenteries are made of
visceral and parietal
peritoneum
Some abdominal organs are
“retro”peritoneal which
means behind the
peritoneum such as the
kidneys, ureters and adrenal
glands, as well as the rectum
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Figure 22.10d
Mesenteries


Greater omentum –
a “fatty apron” of
peritoneum
Greater omentum and
transverse colon
reflected
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Figure 22.10c
Mesenteries

Lesser omentum attaches to lesser curvature of
stomach
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Figure 22.10b
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
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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
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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
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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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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
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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