Stomach Flashcards
What are the anatomical features of the stomach?
Curvatures:
- Lesser
- superior
- short concave border
- attachment for lesser omentum - Greater
- inferior
- long convex border
- attachment for greater omentum
Anatomical sections:
- Cardia
- surrounds cardinal orifice between oesophagus and stomach
- cardial notch: between oesophagus and fundus - Fundus:
- dilated superior region
- sits under left dome of diaphragm at 5th intercostal space - Body
- between fundus and pylorum - Pyloric part
a. pyloric antrum (widest)
b. pyloric canal (narrow passage)
c. pylorus (thickened sphincteric region)
d. pyloric sphincter (controls movement of stomach contents through pyloric orifice to duodenum)
What are the 4 components of the pyloric part of the stomach?
- pyloric antrum (widest part adjacent to body)
- pyloric canal (narrow passageway)
- pylorus (thickened sphincteric region)
- pyloric sphincter (controls movement of stomach contents through pyloric orifice to duodenum)
What type of cells form the mucosal layer of the stomach?
Simple columnar epithelial mucous cells (foveolar cells)
- produce alkaline mucous to protect the epithelium of the stomach
What stimulates mucous secretion by the foveolar cells of the stomach?
Prostaglandins (PGE2)
What forms the muscularis layer of the stomach?
Longitudinal (deep) Circular (intermediate) Additional oblique (superficial)
What is the function of the oblique muscle layer of the stomach?
Specialised functions to assist the mechanical digestion of food including grinding, churning, mixing
What are the layers of the stomach wall?
Mucosal layer (deep) - simple columnar epithelial mucousal cells (fovealar cells)
Submucosa
Muscularis
- longitudinal
- circular
- additional oblique mm
Serosa (intraperitoneal organ)
What are some of the features of the mucosal lining of the stomach?
Rugae:
- ridges formed in the mucosal layer when the stomach contracts
Gastric pits:
- pits in the surface of the mucosa that lead to gastric glands
Gastric glands
- tubular glands that produce gastric juice for enzymatic digestion of food
Simple columnar epithelial mucousal cells produce mucous to protect mucosal lining of stomach
What are the 4 types of cells in the stomach that secrete substances?
- Mucous cells
- secrete protective alkaline mucous
- surface mucous cells (simple stratified epithelial cells in mucosal layer)
- mucous neck cells (on the neck of gastric glands) - Parietal cells
- secrete hydrochloric acid and intrinsic factor
(hydrochloric acid for acidity of gastric juice; intrinsic factor for absorption of B12) - Chief cells
- produce pepsinogen and gastric lipase
(pepsinogen converted into pepsin to digest protein; gastric lipase breaks down fats into fatty acids and glycerol) - Enteroendocrine cells
- secrete hormones and chemical mediators
(gastrin from G cells controls secretory activity of stomach; histamine increases production of acid; serotonin from D cells is an enteric neurotransmitter that affects stomach contractility)
What are the 3 hormones and chemical mediators produced by enteroendocrine cells in the stomach?
- Gastrin
- from G cells
- controls secretory activity of stomach - Histamine
- increases production of acid - Serotonin
- from D cells
- enteric neurotransmitter
- affects stomach contractility
Which hormone produced by enteroendocrine cells in the stomach affects secretory activity; and which affects contractility?
Gastrin from G cells affects secretory activity
Serotonin from D cells affects contractility
Which 2 substances are produced by the chief cells?
Pepsinogen
- converted into the enzyme pepsin by gastric acid
- pepsin digests protein
Gastric lipase
- breaks down fats into fatty acids and glycerol
Which substances break down protein and fats in the stomach?
Protein is broken down by the enzyme pepsin (from pepsinogen secreted by chief cells)
Fats are broken down into fatty acids and glycerol by gastric lipase
Which 2 substances are secreted by the parietal cells?
Hydrochloric acid - contributes to acidity of gastric juice
Intrinsic factor - required for absorption of B12 in terminal ileum
Which 2 mechanisms inhibit gastric emptying?
- Neural (enterogastric reflex)
- duodenal receptors respond to distension and low pH
- causes reflex inhibition of ENS and CNX
- reduces secretions and motility to slow down gastric emptying - Duodenal hormones
- released in response to fatty acidic chyme
- cholecystokinin (CCK), gastric inhibitory peptide and secretin
What is the process of gastric emptying?
- Peristaltic contraction originates in fundus and sweeps down towards pylorus
- Strong pyloric contraction propels some of the chyme through pyloric sphincter into dudodenum
- When peristaltic contraction reaches pyloric sphincter, the sphincter closes and any chyme that was being propelled forwards in peristaltic wave is tossed back into the antrum
- mixing of chyme is accomplished as chyme is propelled forward and tossed back into the antrum with each peristaltic contraction
What are the effects of PNS and SNS activity on the stomach?
PNS:
CNX Vagus nerve stimulates stomach activity
SNS:
Greater splanchnic nerves (from T6-9) via celiac plexus inhibits stomach activity
What are the effects of PNS and SNS activity on the stomach?
PNS:
CNX Vagus nerve stimulates stomach activity
SNS:
Greater splanchnic nerves (from T6-9) via celiac plexus
Which events inhibit the activity of the stomach?
- SNS input
- greater splanchnic nerves (T6-9) via celiac plexus - Enterogastric reflex
- duodenal receptors sense distention and/or low pH and cause reflex inhibition of ENS and CNX - Duodenal hormones
- CCK, gastric inhibitory peptide and secretin released in response to fatty, acidic chyme in duodenum
Which events stimulate the activity of the stomach?
- PNS input
- via CNX (dorsal motor nucleus of vagus in medulla) - Vagovagal reflexes
- stretch receptors activated by distension in the stomach - Chemoreceptors in stomach
- food chemicals and rising pH cause G celsl to release gastrin into bloodstream
Which 4 arteries supply the stomach?
Right and left gastric (anastamose at lesser curvature)
Right and left gastro-omental (anastamose at greater curvature)
Which 4 arteries supply the stomach?
Right and left gastric (anastamose at lesser curvature)
Right and left gastro-omental (anastamose at greater curvature)
What is the source of the 4 arteries that supply the stomach?
Celiac Trunk
- common hepatic
- right gastric
Celiac Trunk
- common hepatic
- gastroduodenal
- right gastro-omental
Celiac Trunk
- left gastric
Celiac Trunk
- splenic
- left gastro-omental
What is the only artery of the stomach that arises directly from the celiac trunk?
The left gastric artery
What are the 2 arteries of the stomach that arise from the common hepatic artery (from the celiac trunk)
Right gastric (from common hepatic, from celiac trunk)
Right gastro-omental (from gastroduodenal, from common hepatic, from celiac trunk)
What is the artery of the stomach that arises from the splenic artery?
Left gastro-omental (from splenic, from celiac trunk)
What is the level of the celiac trunk, and its branches?
Celiac trunk arises from abdominal aorta at level T12
Gives off 3 branches:
- common hepatic (gives off right gastric and gastroduodenal)
- left gastric
- splenic (gives off left gastro-omental)
What are the 5 veins that drain the stomach?
Right and left gastric vein (drain directly into hepatic portal)
Right gastro-omental (into superior mesenteric, into hepatic portal)
Left gastro-omental and short gastric (into splenic vein, into hepatic portal)
Where do the veins that drain the stomach drain into?
The hepatic portal vein
- right and left gastric drain directly into hepatic portal
- right gastro-omental drains into superior mesenteric, into hepatic portal
- left gastro-omental and short gastric drain into splenic, into hepatic portal
Which two veins unite to form the hepatic portal vein?
Superior Mesenteric and Splenic
Which artery supplying the stomach arises from the gastroduodenal artery?
Right gastro-omental
Which artery supplying the stomach arises from the splenic artery?
Left gastro-omental
Which 2 veins draining the stomach drain directly into the hepatic portal vein?
Right and left gastric veins
