The Esophagus, Stomach and Small Intestine

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• The Esophagus, Stomach and Small Intestine

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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
Figure 22.17a, b
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• 1)Which layer of the digestive tract is
  responsible for the peristaltic waves that propel
  materials from one portion to another?
• A)submucosa B) serosa
• C)muscularis externa D) mucosa

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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
Figure 22.18a
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• Medial to both midclavicular lines and superior
  to the subcostal plane lies the A)pyloric
  sphincter. B) cecum.
• C)appendix. D) jejunum.

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• Another name for serosa is
• A)adventitia. B) visceral peritoneum.
• C)serous gland. D) mucosa.

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The Stomach
Figure 22.18b
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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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• 2)Which of the following choices correctly pairs
  a type of cell in the stomach with its secretion?
  
• A)chief cell pepsinogen
• B)parietal cell pepsinogen
• C)enteroendocrine hydrochloric acid
• D)parietal cell mucus

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The Stomach Microscopic Anatomy
Figure 22.19ad
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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
Controls flow of pancreatic and bile fluids into
the duodenum
Figure 22.20
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• What is the function of the hepatopancreatic
  sphincter?
• A) It controls the entry of bile and pancreatic
  juices into the alimentary canal.
• B) It inhibits defecation in the upper alimentary
  canal while the anal sphincters do the same in
  the lower regions.
• C) As it contracts, it squeezes pancreatic
  secretions into the duodenum.
• D) It prevents the movement of bile into the
  gallbladder.

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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
Figure 22.21ad