Digestive System Flashcards
Digestive system consists of the ____ and ____
Digestive tract & it’s associated glands
Digestive tract consists of
Oral cavity
Esophagus
Stomach
Small intestine
Large intestine
Anus
4 main layers of walls of GI tract
- Mucosa
- Submucosa
- Muscularis externa
- Serosa & adventitia
Functions of mucosal layer of GI tract
Protection
Absorption
Secretion
3 sub layers of mucosa
Epithelium
Lamina propria
Muscularis mucosae
Define lamina propria
Loose CT which supports epithelium of a mucosal surface
Lamina propria contains…
- blood & lymphatic vessels
- Glands
- lymphatic tissue (GALT/MALT)
Define Muscularis mucosae
Smooth muscle which allows for local movement of mucosa
Submucosa contains…
- Dense irregular CT
- Submucosal plexus (Meissner’s plexus)
- Supports larger blood vessels & lymphatic vessels
- some glands
- lymphatic tissue (GALT/MALT)
Submucosal plexus (Meissner’s plexus)
Autonomic nerves that innervate the Muscularis mucosae (smooth muscle)
Muscularis externa usually consists of…
2 layers of smooth muscle (sometimes 3)
Layers of muscularis externa
- inner: generally circular
- outer: generally longitudinal
- CT between 2 layers
Function of muscularis externa
Layered smooth muscle in opposite planes aids in peristalsis
CT between muscle layers of muscularis externa contains….
- blood & lymphatic vessels
- myenteric plexus (Auerbach’s plexus)
Myenteric plexus
Autonomic nerves that innervate smooth muscle of muscularis externa
Define serous
- Thin layer of CT with outer covering of mesothelium (simple squamous epithelium
- serous membrane (free surface) is continuous with mesentary)
Define adventitia
CT layer that merges with surrounding tissues
- not a free surface (no mesothelium)
Define esophagus
Muscular tube that transports swallowed material to the stomach
Features of esophageal mucosa
- epithelium= stratified squamous (nonkeratinized)
- lamina propria: esophageal cardiac glands
Esophageal cardiac glands
- located near cardiac portion of stomach
- produce neutral mucous to protect esophagus from regurgitated stomach contents
Features of esophageal Submucosa
Esophageal glands
Esophageal glands
- More numerous
- produce slightly acidic mucous to lubricate & protect mucosa
Features of esophageal muscularis externa
- contains skeletal muscle in upper 1/3 of esophagus
- middle 1/3 skeletal mixed with smooth muscle
- lower 1/3 only smooth muscle
*swallowing begins as voluntary and ends with involuntary peristalsis
Functions of esophagus
Transport
Function of stomach
Adds acid fluid to ingested food creating viscous mass (chyme)
stomach
Mucosa & Submucosa thrown into large longitudinal folds called ____
Rugae
Chyme
Mixture of food & stomach acid
stomach
Function of rugae
Allow for distension as stomach fills with food
Regions of stomach
- Cardiac stomach/region (cardia)
- Pyloric stomach/region (pylorus)
- Fundic stomach/region (fundus)
- Body (similar to fundus)
stomach
Features of mucosa
- Epithelium= simple columnar
- surface mucous cells
- gastric glands
Simple columnar epithelium of stomach invaginates into the ____
Lamina propria
stomach
Invaginations into the lamina propria form millions of ____ which lead to ____
Gastric pits lead to gastric glands
stomach
Surface mucous cells
- line lumen & gastric pits
- secrete thick viscous insoluble mucous layer rich in bicarbonate (alkaline)
- protection against chyme & stomach acid
Gastric glands of fundus
Fundic glands
Long, tubular
4 main cell types of Fundic glands
- Mucous neck cells
- Parietal cells
- Chief cells
- Enteroendocrine cells (argent affine cells)
Mucous neck cells
In upper portion
Secrete soluble mucous (slightly acidic)
Parietal cells
Stain eosinophilic
Produce HCL and intrinsic factor
Intrinsic factor
Glycoprotein required for protection & uptake of vitamin B12
Chief cells
Stain basophilic
Located in lower 1/2 of gland
Secrete pepsinogen
In an acidic environment, pepsinogen is converted to ____
Pepsin
Pepsin
Protease that begins breakdown of proteins
What begins to digest lipids?
Gastric lipase
Enteroendocrine cells secretions
Various peptide hormones:
- serotonin, increases gut motility
- gastrin promotes acid production
Cardia & pylorus contain
tubular glands -> long pits -> gastric glands (cardiac & pyloric glands)
Cardiac & pyloric glands composed mostly of ____
Mucous-secreting cells (no chief or parietal cells)
stomach
Layers of muscularis externa
- outer longitudinal
- middle circular
- inner oblique
stomach
Function of muscularis externa
Rhythmic contractions of muscle mix food & chyme with mucous, HCL and digestive enzymes
Pyloric sphincter
Thickening of middle muscle layer at end of pylorus
Controls release of chyme into duodenum
Muscularis externa of the stomach is innervate by ____
Auerbach’s/Myenteric plexus
Function of small intestine
Site where digestion is completed & nutrients are absorbed
3 anatomical segments of small intestine
Duodenum
Jejunum
Ileum
small intestine
Mucosa & Submucosa are thrown into ____
Permanent circular folds (plicae circulares)
Function of plicae circulares
Increase surface area
small intestine
Villi are located in the ____ layer
Mucosa
small intestine
Villi
Finger-like projections of mucosa, covered by epithelium with a core of lamina propria
Function of villi
Increase surface area of mucosa for absorption
small intestine
Epithelium of mucosa
Simple columnar:
- enterocytes (absorptive cells) contain thousands of microvilli
- goblet cells (mucous production) interspersed among enterocytes
small intestine
In the Lamina propria of the mucosa, villi contain a central ____
Lacteal
Lacteal
Highly permeable lymphatic vessel, closed at one end
Important for absorption of lipids
small intestine
In the Lamina propria of the mucosa, between villi, short tubular glands open into ____
Crypts of Lieberkuhn (intestinal glands)
Crypts of Lieberkuhn (intestinal glands) are lined with ____
- Mainly Enterocytes & goblet cells
- paneth cells (in basal portions of crypts)
- Enteroendocrine cells
Paneth cells
In basal portion of crypts
Secrete antimicrobial substances
small intestine
In the Lamina propria of the mucosa, Enteroendocrine cells produce…
Various peptide hormones
- cholecystokinin: promotes pancreatic enzyme secretion, gall bladder contraction, inhibits gastric acid secretion, and secretin, promotes pancreatic water & bicarbonate secretion, inhibits gastric acid secretion & stomach emptying
Submucosa of duodenum contains ____
Brunner’s glands (duodenal glands)
Brunner’s glands produce….
Alkaline mucus (neutralize chyme, optimal pH for pancreatic enzymes)
Ducts of Brunner’s glands open into ____
Crypts of Lieberkuhn (mucosa)
How is the jejunum differentiated?
Lack of submucosal glands
Lack of Peyer’s patches
In the ileum, the mucosa (lamina propria + submucosa) contains ____
Peyer’s patches
Peyer’s patches
Permanent lymphatic nodules
How do Peyer’s patches differ from GALT/MALT?
GALT/MALT is transient
Peyer’s patches are permanent
Principle functions of large intestine
- Absorption of electrolytes and water
- elimination of undigested food/waste
3 parts of large intestine
Cecum
Colon
Rectum
Cecum
Short piece, forms blind pouch from which the appendix projects
Colon
Subdivided into ascending, transverse, descending, sigmoid
Rectum
Dilated distal portion, stores feces prior to evacuation
Mucosal surface of large intestine
Smooth surface - no plicae circulares or villi
Epithelium of mucosal layer of large intestine
Simple columnar: many goblet cells interspersed with enterocytes which have microvilli
Lamina propria of mucosal layer of large intestine
Contains crypts of Lieberkuhn
Muscularis externa of colon is condensed into 3 separate longitudinal bands of muscle called ____
Teniae coli
Teniae coli
Contract lengthwise, aid in peristalsis
Epithelium of anal canal
Simple columnar of rectum shifts abruptly to stratified squamous of skin at the anus
Near the anus, the circular layer of muscularis externa forms the ____
Internal anal sphincter
Internal anal sphincter has further control exerted by ____
Skeletal muscle of external anal sphincter
