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.