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68 Cards in this Set
- Front
- Back
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What is the stomach and what does it do?
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It is an expanded region of digestive tube.
Functions: 1) Accepts food bolus from esophagus 2)Act as a food reservois 3) Mechanical and chemical digestion that produces chyme 4)Moves gastric contents into small intestine |
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What is the anatomy of the stomach?
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It has four anatomically distinct regions:
-Cardia -Fundus -Body(Corpus) -Pylorus Has transient mucosal and submucosal folds known as rugae. They allow expansion when you eat alot. |
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What is the stomach lined with?
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There is a sharp boundary between the esophagus and the stomach
Lined with simple columnar epithelium. Has surface lining cells that are all the same. has a glandular sheet and produces alkaline mucus. Has no globet cells and is highly protective. There is little absorption. (Water, alcohol and some drugs are exceptions) |
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What does this image show?
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Lining epithelium
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What are gastric pits?
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They are the epithelial depressions found in the luminal surface of stomach
Open into funnel-shaped invaginations. The base of funnel receives secretions from Mucosal glands. |
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What are gastric glands?
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They are simple, branched, tubular glands.
THey extend from the base of gastric pit into lamina propria. They are named according to location. |
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What are fundic glands?
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•Also called Zymogenic Glands
•Most numerous •Straight and extend to level of muscularis mucosae •3-7 glands open into base of the gastric pit •Produce virtually all of the acid and enzymes and much of the mucus in gastric juice –Produce 2-3 liters per day |
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What are four types of glandular cell types?
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•Regenerative (Stem) Cells
–Thin, columnar cells interspersed with mucous neck cells –Divide to replace all gland cells and surface cells •Mucous Neck Cells –Difficult to identify in H&E sections –Secrete Acid mucus –Smaller and more irregular than surface mucous cells –Found in apical region of the gland •Parietal (Oxyntic) Cells –Triangular or pyramidal, with broad base –Highly eosinophilic •Large numbers of mitochondria –Large amounts of intracellular membrane –Secrete HCl and Gastric Intrinsic Factor –Respond to Gastrin •Chief (Principal, Zymogenic) Cells –Deepest part of glands –Typical protein-secreting cells •Basal nucleus, lots, of RER, apical secretory granules –Respond to presence of Secretin by releasing Pepsinogen, inactive precursor to Pepsin –Pepsin is potent proteolytic enzyme –Cells also secrete Rennin and Gastric Lipase •Enteroendocrine Cells –DNES cells –Difficult to identify in H&E sections –Secrete hormones –At least 13 different types Not all in stomach –Secrete basally rather than apically PERMZ!! |
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What does this image show?
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Gastric Glands
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What does this image show?
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Parietal Cells
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What does this image show?
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Parietal Cells
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What kind of glands are these?
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Gastric glands
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What type of cells are these?
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Chief Cells
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What is shown in this image?
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Enteroendocrine Cell
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What is shown in this image?
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Gastrin-Secreting Cells
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What are the properties of the lamina propria?
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•Typical for the alimentary canal
•Large numbers of lymphocytes, plasma cells, and occasional lymphoid nodules present •Large numbers of transient connective tissue cells from the blood -Made of loose irregular connective tissue |
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What does this image show?
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Lamina Propria
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What are the properties of the muscularis mucosae?
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•Usually two layers
–Inner circular –Outer longitudinal •Orientation of layers not always obvious •Occasional third, incomplete circular layer may be present |
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What does this image show?
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Muscularis mucosae
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What are the properties of the submucosa in the stomach?
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•Typical for the alimentary canal
•No submucosal glands in the stomach •Meissner’s plexus is present Plexus is a ganglian cells that innervate muscularis mucosa occasionally |
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What does this image show?
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Submucosa
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What are the properties of the muscularis externa in the stomach?
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•Atypical
•3 layers of smooth muscle –Inner Oblique •Incomplete –Middle Circular •Most prominent •Continuous with inner layer of esophagus and becomes the pyloric sphincter –Outer Longitudinal •incomplete •Not always easy to distinguish the layers |
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What does this image show?
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Muscularis Externa
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What does this image show?
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Myenteric Plexus- Auerbach's plexus
Exists between the longitudinal and circular layers of muscluaris externa |
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What is the small intestine and what does it do?
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•Longest tubular part
–7 m in adult males (>21 ft) •Functions –Receive Chyme –Secrete enzymes and mucus –Continue digestion –Initiate absorption of nutrients •Anatomically divided into 3 segments –Duodenum, Jejunum, and Ileum |
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What are the properties of the duodenum?
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•Duodenum
–Shortest segment (25 cm) –Receives chyme and neutralizes it –Receives pancreatic enzymes and bile –Significant absorption of lipid |
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What are the properties of the jejunum?
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•Jejunum
–40% of intestinal length beyond the duodenum (8 ft) –Primary site of absorption of digestion products (amino acids, lipids, and sugars) |
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What are the properties of the ileum?
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•Ileum
–60% of intestinal length beyond the duodenum (12 ft) –Primary site of absorption of vitamin B12 and bile salts |
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What is the general structure of the small intestine?
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•4 basic layers present throughout
•Lining epithelium –Simple columnar epithelium with Goblet Cells –Enterocytes (Intestinal Absorptive Cells) •Tall, polarized cells •Basal nucleus •Prominent striated border of microvilli •Glycocalyx |
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What does this image show?
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Intestinal epithelium
Notice brush border |
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What are goblet cells?
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•Goblet Cells
–Single-celled, mucus-secreting glands •Secrete Acidic mucus –Found throughout small and large intestines –Cell density increases distally |
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What are enteroendocrine cells?
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•Enteroendocrine Cells
–Same structure as in stomach –Rare in this epithelium |
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What does this image show?
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Intestinal Goblet Cells stained with PAS
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What are the surface modifications in the intestine?
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•Mucosa and submucosa are modified at various levels to increase surface area available for absorption
–Plicae Circulares –Villi –Microvilli |
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What are plicae circulares?
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•Permanent spiral folds of mucosa and submucosa
•Most prominent in Jejunum •Become progressively smaller and less frequent as you move toward colon •Increase surface area by a factor of 2–3 |
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What does this image show?
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Plicae Circulares
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What are villi?
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•Permanent projections of mucosa
•Generally decrease in size as you move more distally •Core of lamina propria contains –Diffuse lymphoid tissue –Extensions of smooth muscle –Fenestrated capillary loops –Lacteal •Increase surface area by a factor of 10 |
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What does this image show?
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Villi with a SEM
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What does this image show?
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Villi
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What are microvilli?
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•Cellular extensions on apical surface
–1 m 0.1 m •Contain core of actin filaments •Increase surface area by factor of 20 |
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What does this image show?
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Microvilli
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How do surface modifications increase the surface area?
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•Plicae Circulares: 2–3
•Villi: 10 •Microvilli: 20 •Total increase in surface area is 2.5 10 20 500 |
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What are the intestinal mucosal glands?
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•Crypts of Lieberkühn
•Simple tubular glands •Extend from the base of the villi to the muscularis mucosae •Goblet Cells •Paneth Cells –Restricted to the base of the glands –Typical protein-secreting cells –Apical eosinophilic secretory granules –Secrete Lysozyme and are capable of bacterial phagocytosis •Enteroendocrine Cells •Stem Cells –Principal cell in the crypt –Basal half of gland –Thin, columnar cell –Actively mitotic –Replace entire epithelium every 5–6 days |
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What does this image show?
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Villi and Crypts
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What does this image show?
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Paneth Cells
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What does the lamina propria look like in the intestines?
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•Contains significant amount of diffuse lymphoid tissue
•In ileum, nodules form aggregates called Peyer’s Patches |
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What are the properties of the muscularis mucosae in the intestines?
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•Typical two layers
–Inner circular –Outer longitudinal •See occasional cells extending into the villus –Contraction helps to move material in Lacteals into larger lymphatic vessels |
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What does this image show?
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Lacteal
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What are the properties of the submucosa in the intestine?
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•Typical for the alimentary canal
•Contains glands Only in the duodenum –Brunner’s Glands –Alkaline mucus: pH = 8.19.3 •Increases pH of lumenal contents •Protects lining epithelium of duodenum –Ducts extend through muscularis mucosae into base of crypts or base of villi |
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What does this image show?
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Brunners Glands stained with PAS
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What are the properties of the muscularis externa?
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•Typical two layers
–Inner circular –Outer longitudinal •Inner layer forms Ileocecal Sphincter •Auerbach’s plexus |
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What part of the intestines is covered in adventitia vs serosa?
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•Serosa covers entire jejunum and ileum and the intraperitoneal part of duodenum
•Adventitia covers the retroperitoneal part of duodenum |
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What does this image show?
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The Large Intestine
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What are general characteristics of the large intestine?
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•Typical four layers
•About 5 feet long •Cecum and various parts of Colon have same histology |
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What are the functions of the large intestine?
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•Secretion
–Mucus and ions (principally HCO3–) •Absorption –Water, electrolytes, some drugs, and gas •Putrefaction –Enzymatic degradation of protein by microorganisms •Elimination –Feces •Continues absorption of electrolytes and fluids begun in small intestine •After removal of water, dead bacteria and undigested material become compacted. •Copious mucus protects the lining and lubricates the feces to ease elimination. |
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What is the appendix?
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•Current function unclear
•Short narrow diverticulum from blind end of Cecum –Vermiform •Stellate lumen with numerous lymphoid nodules in lining –Nodules may extend into submucosa |
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What does this image show?
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Appendix
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What are the components of the appendix?
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•Mucosa
–Simple columnar epithelium –No villi and no plicae circulares –Crypts of Lieberkühn are shallow –Typical lamina propria –Typical muscularis mucosae •Submucosa: No glands •Muscularis externa: Typical •Serosa surrounds entire appendix |
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What are the properties in the cecum and colon?
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•Mucosa:
–Simple columnar epithelium with lots of goblet cells –No villi and no plicae circulares –Numerous crypts of Lieberkühn present –Lamina propria •No Paneth cells –Prominent muscularis mucosae •Submucosa: Typical, no glands –Fibroelastic •Muscularis externa: Not typical –Outer longitudinal gathered into 3 bands •Teniae Coli |
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What does this image show?
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Colon
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What does this image show?
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Crypts of Lieberkuhn; Colon
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What does this image show?
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Teniae Coli of the colon
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What part of the colon is covered in adventitia vs serosa?
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•Both adventitia and serosa present
–Adventitia: Ascending and descending colon –Serosa: Cecum and remainder of colon |
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What is the rectum and what does it do?
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•Short, dilated, terminal portion of the large intestines
•Function: Store fecal matter until eliminated •Histologically similar to colon –Crypts of Lieberkühn are longer, less numerous, and contain more goblet cells |
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What does this image show?
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Anal Canal
Notice 1) Epithelia lining changed stratified squamous keratinized (thin skin) 2) within mucosa + submucosa large veins that become expanded |
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What is the anal canal? What are the components of the anal canal?
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•Restricted terminal continuation of the rectum
•Mucosa contains longitudinal folds –Anal Columns (of Morgagni) –Folds join to form Anal Valves •Mucosa –Epithelium changes from simple columnar to simple cuboidal to stratified squamous nonkeratinized –Epithelium becomes thin skin at Anus •Lamina propria: Fibroelastic tissue –Sebaceous glands, circumanal glands, hair follicles, and large veins –Hemorrhoids •Muscularis mucosae: Typical •Submucosa: Large veins & Hemorrhoids •Muscularis externa: Thickened circular layer becomes Internal Anal Sphincter |
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What does this image show?
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Rectoanal junction
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What surrounds the anus? What is the external anal sphincter?
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•Entire anus surrounded by adventitia
•External Anal Sphincter is skeletal muscle investing anus –Continual tonus –Provides a degree of voluntary control |
