esophagus and stomach

phases of food moving down espohagus

1. voluntary phase

2. pharyngeal phase

3. esophageal phase

voluntary phase

• voluntary control

• upper musculature of RT is skeletal

• tongue pushes a bolus of food backwards. moves into oropharynx

pharyngeal phase (involuntary)

• swallowing draws the larynx up and propulsion of food

• oral and nasal cavities are blocked

• can’t breathe during this phase

esophageal phase (involuntary)

• involuntary actions; peristalsis

• primary peristaltic contraction forces food down length of esophagus (pressure high behind food)

• lower esophageal sphincter will then open

sphincters in the esophagus

• superior esophageal sphincter: ring of circular skeletal muscle at the upper end of esophagus

• inferior esophageal sphincter: ring of circular smooth muscle at the lower end of esophagus that includes part of diaphragm; physiological sphincter

physiological sphincter

contraction of diaphragm closes opeining

histology of esophagus

mucosa

• non-keratinized stratified squamous epithelium

• esophageal cardiac glands in lamina propria (near pharynx and stomach- produce mucus)

• single layer of muscularis mucosae

submucosa

• dense irregular CT and loose CT

• esophageal glands producing mucus

• submucosal plexus of ENS

muscularis

• inner circular and outer longitudinal muscle

• stories of thirds; proximal 1/3 is skeletal, middle 1/3 skeletal/smooth, distal 1/3 smooth

• myenteric plexus

adventitia

• outer dense CT for anchoring

stomach

J shaped muscular organ divided into 4 regions

1. cardiac- GE junction

2. Fundic- storage of food

3. body- major part of stomach

4. pyloric- distal end, above duodenum

Curvatures of stomach

1. greater curvature- greater omentum (Stores fat) suspended here

2. lesser curvature- lesser omentum (Passageway for arteries, veins, lymphatics etc.) suspended here

sphincters of stomach

1. cardiac sphincter (infoerior esophageal sphincter)

2. pyloric sphincter

mucosa

• simple columnar epithelium

• gastric pits → open into gastric glands

  • glands have specialized secretory cells (parietal, chief, enteroendocrine)

  • stem cells

• rugae

rugae

mucosa and submucosa wrinkle and fold to produce these

muscularis external

• THREE layers or muscle

• internal oblique (most well defined in cardiac region)

• middle circular

• outer longitudinal

cell types in stomach

• Mucous and mucus neck cells

• Parietal cells

• Chief cells

• Enteroendocrine cells

• Stem cells

surface mucous and mucus neck cells

• surface release basic mucus

• neck cells release acidic mucus

  • protects mucosa from HCl and enzymes

parietal cells

release HCl and intrinsic factor

• HCl activates pepsin and lingual lipase; helps liquify food

• intrinsic factor enables small intestine to absorb vitamin B12 (RBC formation)

chief cells

release pepsinogen (precursor of pepsin) and gastric lipase

• pepsinogen converted to pepsin which digests protein

• gastric lipase digests fat

how does stomach protect itself

• mucus production

• tight junctions

• stem cells replace differentiated cells

• buffering

histology of stomach

mucosa

• simple columnar epithelium (surface mucous cells) with openings (gastric pits) with mucous neck cells

• pits open into glands: multiple cell types (parietal, chief, enteroendocrine, stem)

• highly vascularized lamina propria

• two layered mucularis mucosae

submucosa

• dense irregular CT and loose CT

• submucosal plexus of ENS

muscularis

• inner oblique (most defined in cardiac region)

• middle circular

• outer longitudinal

• myenteric plexus of ENS

serosa

• simple epithelium

• loose CT