the esophagus, stomach and small intestine. the esophagus gross anatomy – muscular tube begins as...
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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 22.19a–d
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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
Figure 22.20Controls flow of pancreatic and bile fluids into the duodenum
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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 22.21a–d