8-Digestive system-II- Alimentary canal Flashcards
Pharynx function
Provide communication between nasal & oral cavities with the larynx and trachea
Pharynx regions
- Nasopharynx
- Orophayrnx
- Laryngopharynx
Pharynx lining
Mostly Stratified squamous non-keratinized epithelium
-respiratory areas lined with pseudostratified respiratory epithelium
General layers of the alimentary canal
Pharynx Esophagus Stomach Small intestine Large intestine
Main layer of the alimentary canal
- Mucosa
- Submucosa (dense irreguar CT)
- Muscularis Externa(all regions except upper 2/3rds of of esophagus
- Serosa(Mesothelium + CT) or Adventita (CT)
Parts of mucosa(general)
Lining epithelium
Lamina propria
Muscularis mucosae
Esophagus mucosa
- Lining epithelium- Stratified squamous non-keratinized epithelium
- Lamina propria- Loose CT w/ lymphatic nodules, MALT, esophageal cardiac glands
- Muscularis mucosae- Smooth muscle- organized
MALT
Mucosa associated lymphoid tissue
Esophageal cardiac glands
- Lamina propria of distal esophagus
- secrete mucus and protects esophagus from acid
Esophagus Submucosa
- Dense Irregular CT with elastic fibers
- Esophageal gands proper
- Location of Meissner’s plexus
Esophageal gland proper
- Located thorough out the length of esophageal submucosa
- produces mucus that lubricates the wall and offers protection
Meissner’s plexus
Parasympathetic innervation to muscularis mucosae
Esophageal muscularis externa
-Inner circular/outer longitudinal
-Skeletal muscle replaced with smooth muscle
Upper 1/3- skeletal
middle 1/3- mixed
Lower 1/3- smooth
-Auerbach’s plexus
Auerbach’s plexus
- Between inner circular/outer longitudinal
- innervates muscularis externa
Esophageal adventitia and serosa
- Adventia in thorastic cavity bind to trachea, aorta and other thoratic structures
- Serosa-covers part within the abdomen
Gastro-esophageal junction
- Abrupt changes in epithelium from Stratified squamous non-keratinized epithelium to simple columnar epithelium
- Gastroesophageal sphincter- physiological sphincter- inner circular layer increases in tone
Parts of the stomach and which are histoogically the same
Cardia Fundus Body Pylorus -Fundus and body are histologically the same
Major function of the stomach
Physical and chemical digestion into chyme
Rugae
Transient folds in the stomach
Stomach-Mucosa-lining epithelium
Simple columnar epithelium covers: luminal surface, gastric pits and glands
Stomach glands
- 3-7 glands per pit
- Extend from gastric pit into the lamina propria to level of muscularis mucosae
- isthmus, neck and base
Cell types of lining epithelium
1) Surface mucous cells
2) Mucous neck cells
3) Stem cells
4) enteroendocrine cells
5) Parietal cells
6) Chief cells
Surface mucous cells(location structure and function)
-Luminal surface of stomach and gastric pits
-Simple columnar cells, apical mucigen granules, basal nucleus
Function: release mucin, forms viscous alkaline mucus with water high in bicarbonate protects the luminal surface from acid.
Types of stomach galnds
Gastric glands
Cardiac glands
Pyloric glands
Gastric glands(location and cell types)
-Body and fundus Mucous neck cells Stem cells Enteroendocrine cells Parietal cells Chief cells
Cardiac glands(location and cell types)
-Cardia Mucous neck cells Stem cells Enteroendocrine cells -Some parietal cells
Pyloric glands(location and cell types)
-Pyloris
Mucous neck cells
Stem cells
Enteroendocrine cells
Mucous neck cells (location structure and function)
Location: Ismuth and neck of cardiac and gastric glands. Adjacent to parietal cells
- Structure: Columnar, can appear less regular. Apical Mucigen granules and basal nucleus
- Function: contribute to mucous, less alkaline than surface mucous cells. Protect parietal cells
Stem cells(location structure and function) Stomach
Location: Isthmus and neck of the cardiac and gastric glands
Structure: columnar cells
Function: Stem cells for all epithelial cell types in the stomach
Entroendocrine cells (location structure and function) Stomach
Location: Base of cardiac and gastric glands
Structure: Basally secretes granules
Function: Basal secretion of various hormones into lamina propria(blood vessels)
Parietal cells (location structure and function)
Location: scattered throughout the gastric glands
Structure: Large triangular with intracellular canaliculi and microvilli. Cytoplasm is eosinophillic due to abundant mitochondria.
Function: Produce H+ and Cl- separately.
Chief cells (location structure and function)
Location: Base of gastric glands
Structure: apical zymogen granules with pepinogen. Basal cytoplasm basophillic from rER
Function: Secrete pepsinogen, which is converted to pepsin, and gastric lipase
Stomach-Mucosa- Lamina propria
Surrounds gastric glands and pits
Loose CT with few lymphatic nodules and MALT
Stomach-Mucosa-Muscularis Mucosae
Smooth muscle
facilitates outflow of gastric glands
Stomach-Submucosa
- Dense irregular CT
- Neurovascular structure including Meissner’s plexus
- No glands
Stomach-Musularis extrerna
- 3 layers inner oblique, middle circular, outer longitudinal layers
- Auerbach’s nerve plexus between muscle layers
- Mixes chyme and moves content to duodenum
does the stomach have serosa or adventitia?
Serosa- covers the stomach
Pyloric sphincter(location, structure, function)
Located at the junction of pyloric stomach and the duodenum
Formed by thickening of middle circular layer of muscularis externa
Main regions of the small intestine
Duodenum, Jejunum, and ileum
Small intestine major functions
Complete digestion
Absorb nutrients
Absorptive feature(list)
Plicae circulares
Villi
Microvilli
Plicae circulares
Series of permanent circular folds mucosa and submucosa
Villi
evaginations of the muscosa -lined with SSE with a core of lamina propria
Microvilli
Located at the apical spect of enteroctyes/absorptive cells (mucosa)
Small intestine-Mucosa-Lining epithelium
Simple columnar epithelium covers villi and intestinal glands/crypts of Leiberkuhn
Small intestine-Mucosa-lining epithelium (cell types)
- Enterocytes(absorptive cells)
- Goblet cells
- Enteroendocrine cells
- Paneth cells
- M-cells
- Stem cells
Enterocytes (location, structure, and function)
SI
Location: line luminal surface of villi migrate from the crypt
Structure: Columnar cell with microvilli, covered in glycocalyx, called striated border.
Function:
-Absorptive role: transports nutrients from lument into blood
-Secretory role: glycoprotein enzymes are secreted into the glycocalyx(digestive) also secrete water to maintain chyme consistency
Goblet cells (location, structure, and function) SI
Location:line the luminal surface of villi and crypts. Scattered among enterocytes. Increase in number from duodenum to distal large intestine
Structure:Goblet shape. apical mucigen granules
Function: Mucin release apically
Enteroendocrine cells (location, structure, and function) SI
Location: scattered along villi and crypts
Structure: basal secretory granules
Function: Release various hormones
Paneth cells (location, structure, and function) SI
Location: Base of intestinal crypts
Structure: Apical eosinophilic granules that contain lysozyme
Function: lysozyme digest the cell wall of microrganisms
M-cells(location, structure, and function)
SI
Location; mainly overlie large lymphatic nodules
Structure:
-Apical: lack of microvilli but have microfolds
-Basal: large intracellular pockets immune cells migrate through the discontinuous basement membrane
Function: endocytose and transport antigens to underlying immune cells
Stem cell (location, function) SI
base of intestinal crypts
Replace all lining epithelial cell types
Small intestine-mucosa-lamina propria
-Loose CT at the core of intestinal villus and surrounds intestinal crypts/glands. Fenestrated capillaries, lympatic vessel(lacteal), Smooth muscle fibers, MALT, and lymphatic nodules
Small intestine-mucosa-Muscularis mucosae
Movement of villi
Small intestine-submucosa
-Dense irregular connective tissue includes Meissner’s plexus, blood, and lymph vessels in all three regions
Small intestine-submucosa-Duodenum
Large mucous gland(Brunner glands)
-Protects epithelium and provides optimal pH for pancratic enzymes
Small intestine-submucosa- jejunum
no unique histologic features
Small intestine-submucosa-Ileum
Large lymphoid nodules called peyer patches extend from submucosa into the lamina propria
Small intestine-Muscularis externa
Inner circular and outer longitudinal Auerbach’s plexus which is important for peristalsis
Small intestine-Serosa and adventitia
Serosa covers majority of the small intestine
adventitia located where duodenum contacts the posterior abdominal wall
Parts of the large intestine
- Ileocecal valve(leads to cecum)
- Appendix
- Colon
- Rectum
- Anal canal
Large intestine major functions
- Absorption of water and Na+
- Indigestible material(feces) is formed and expelled.
Ileocecal valve
Thickening of the inner circular layer of musicalris between the ileum and cecum
Appendix
- Extends from the cecum
- typical 4 layer wall
- high density of lymphatic nodules and little to no absorptive function
Large instestine-mucosa- lining epithelium
- Simple columnar epithelium. NO vili
- Has numerous tubular lands/crypts that extend into the lamina propria
Large instestine-mucosa- lining epithelium(cell types)
1) absorptive cells
2) Goblet cells
3) Enteroendocrine cells
4) Stem cells
5) M-cells
Absorptive cells(colonocytes/enterocytes)(location, structure, function) LI
Location: luminal surface and glands/crypts
Structure:columnar, short microvilli
Function: absorb water and Na+
Goblet cells (location, structure, function) LI
Location luminal surface and glands/crypts
Structure: goblet shaped
Function: mucus lubricates and protects epithelium
Enteroendocrine cells (location, function) LI
Location: crypts/glands(1° base)
Function: basal secretion of hormones
Stem cells(location, function) LI
Location: crypts/glands (1° base)
Function: replace epithelial cell types
M-cells:(location, structure, function)
LI
Location: Overlie lymphatic nodules
Structure: Apical microfolds, basal intracellular pockets
Function: transport antigens to underlying immune cells
Large instestine-mucosa- Lamina propria
Loose Ct with abundant immune cells more than small intestine
numerous capillaries in which water and sodium are absorbed
no lymphatic vessels as they organize around muscularis mucosae
Large instestine-mucosa- muscularis mucosae
enhance expulsion of mucus from glands
Large instestine- submucosa
Dense irregular CT, Meissner’s plexus, blood and lymph vessels
Lymphoid tissue extending from lamina propria
Large instestine-Muscularis externa
- Inner circular and teniae coli
- Auerbach’s plexus in between the muscular layers
Teniae coli
3 evenly spread longitudinal muscle bands
Large instestine-serosa and adventitia
Serosa covers the intraperitoneal portions of the large intestine
Adventitia located where teh large intestine is in contact withe the posterior abdominal wall
Large intestine- Rectum
Dilated, distal portion f large intestine
-similar to colon but:
Crypts/glands are deeper with more goblet cells
-no teniae coli has outer longitudinal layers
-Adventitia only
Anal canal
Upper 1/3: Simple columnar epithelium
Middle 1/3: Stratified columnar epithelium
Lower 1/3: Stratified squamous non-keratinized epithelium becomes keratinized at the anus
Internal anal sphincter from inner curular layer of muscularis externa
External anal sphincter is skeletal msuonlcle
Adventitia only
