Histology of the Esophagus & Stomach Flashcards
4 Layers of GI Tract: Lumen –> Superficial
(1) Mucosa
(2) Submucosa
(3) Muscularis Externa
(4) Serosa/Adventitia
Serosa: Intraperitoneal or Retroperiotneal?
Intraperitoneal
Adventitia: Intraperitoneal or Retroperiotneal?
Retroperitoneal
3 Components of the Mucosal Layer:
(1) Lining Epithelium (varies segment to segment)
(2) Underlying Lamina Propria
(3) Muscularis Mucosae
Mucosal Layer: Lamina Propria
- Vascularized, loose connective tissue
- Contains lymphatic nodules and WBCs
Mucosal Layer: Muscularis Mucosae
- Thin layer of smooth muscle that controls mobility and infoldings of mucosa
Submucosal Layer
- Consists of a dense irregular connective tissue with neurovasculature and lymphatics
- Nerve plexus associated with this layer
- Glands may also be present (esophagus and duodenum)
Muscularis Externa
- Two layers of smooth muscle
- Neurovasculature plexuses located between layers
Muscularis Externa: Circular Layer
- Inner layer
- Function is to constrict the lumen
Muscularis Externa: Longitudinal Layer
- Outer layer
- Function is to shorten the tube
Serosa/Adventitia
- GI tract is suspended by a mesentery/peritoneal fold
- Organs may have adventitia and/or serosa
The Adventitial is covered by ___ and forms ____ layer
- Mesothelium
- Serosa
Areas without mesothelium covering have an:
Adventitia
What are the 4 Basic Mucosal Types?
- Protective
- Secretory
- Absorptive
- Absorptive + Protective
Mucosa Types: Protective
- Nonkeratinized stratified squamous epithelium
- Located in oral cavity, pharynx and anal canal
Mucosa Types: Absorptive
- Simple columnar epithelium
- Mucosa arranged as villi with crypts; glands may or may not be present
- Located in SI
Mucosa Types: Secretory
- Simple columnar epithelium
- Mucosa is packed with glands
- Located in Stomach
Mucosa Types: Absorptive + Protective
- Simple columnar epithelium
- Mucosa arranged into closely packed glands with extensive goblet cells
- Located in LI
Two Plexuses of Sensory and Motor Neurons (Intrinsic/Enteric Innervation), linked by interneurons:
(1) Submucosal Plexus (of Meissner)
(2) Myenteric Plexus (of Auerbach)
Intrinsic/Enteric Innervation
Responsive to local stimuli and input from ANS
Intrinsic/Enteric Innervation Regulates and Controls:
(1) Peristaltic contractions of muscularis externa and movements of muscularis mucosae
(2) Secretory activities of mucosal and submucosal glands
Location of Myenteric Plexus:
Between the Circular Muscle and Longitudinal Muscle
Location of Submucosal Plexus:
Between the Submucosa and Circular Muscle
Preganglionic axons of the Parasympathetics ____ motility.
Increase
Postganglionic axons of the Sympathetics _____ motlity
Decrease
Esophagus
- Fibromuscular tube that conveys food from oropharynx to stomach
- Contains both Serosa and Adventitia
- Contains both mucosal and submucosal glands that produce a thin layer of mucus to lubricate the epithelium
Part of Esophagus that has Adventitia:
Thoracic Esophagus
Part of Esophagus that has Serosa:
Inferior to Diaphragm
Glands of the Esophagus: Cardiac Esophageal Glands
Reside in the Lamina Propria of the terminal esophagus
Glands of the Esophagus: Submucosal Glands
Consist of small lobules with mucous and serous cell types
Esophagus: Mucosal Layer
- Non-keratinized stratified squamous overlying a lamina propria
- Numerous folds distend with food passage
Esophagus: Submucosal Layer
- Network of collagen and elastic fibers
- Contains many small blood vessels
- Submucosal venous plexuses drain into both the systemic and portal venous system
Increased pressure in the Esophageal Submucosal Venous Plexuses can lead to:
Esophageal Varices (dilation of submucosal venous sinuses)
Esophagus: Muscularis Layer
Consists of inner circular layer and outer longitudinal layer; layers have segment-dependent variations
Muscularis Layer: Upper 1/3 Esophagus
Skeletal Muscle (Striated)