1,473
edits
Changes
Jump to navigation
Jump to search
Monogastric Stomach - Anatomy & Physiology (view source)
Revision as of 21:36, 17 December 2010
, 21:36, 17 December 2010→Histology
==Histology==
==Histology==
[[Image:Glandular Stomach Histology Dog.jpg|thumb|right|150px|Glandular Stomach Histology Dog- Copyright RVC 2008]]
[[Image:Glandular Stomach Histology Dog.jpg|thumb|right|250px|Glandular Stomach Histology Dog- Copyright RVC 2008]]
The monogastric stomach has a columnar epithelium. The folded mucosa of the stomach forms a '''longitudinal rugae'''. The folds form invaginations called '''gastric pits''' which are continuous with gastric glands.
''Layers of the stomach''
The 4 layers of the stomach wall are:
'''1.Serosa/adventitia'''
'''2.Tunica muscularis'''
'''3.Submucosa'''
'''4.Mucosa'''
There are 3 layers of '''muscularis''': the outer longitudinal, middle circular and inner oblique. The '''pyloric sphincter''' is thickened tunica muscularis from the middle circular smooth muscle layer. In the '''fundic region''', the tunica muscularis is thinner, the glands are straight and the gastric pits are shallow. There is also an abundance of parietal and cheif cells in the gland. In the '''pyloric region''', the tunica muscularis is thicker, the glands are coiled and the gastric pits are deep. The '''cardia''' is a narrow muscle strip. The lymphatic vessels are present in the submucosa.
''Cell types''
The stomach contains basophilic '''chief (zygomatic) cells''' that secrete '''pepsinogen''' in response to vagus nerve stimulation and gastrin release. Pepsinogen unfolds and cleaves itself (autocatalyses) in response to hydrochloric acid, therefore only in acidic envrionments.
[[Image:Fundic region of glandular stomach.jpg|thumb|right|250px|Fundic Region of Glandular Stomach (Parietal and Chief cells)- Copyright RVC 2008]]
The stomach also contains '''goblet cells''' that secrete mucous. This secretion protects against autodigestion.
There are also '''parietal (oxyntic) cells''' found in gastric pits that secrete hydrochloric acid. This secretion aids digestion by activating gastric enzymes, e.g. pepsinogen to pepsin. Hydrochloric acid kills microorganisms and enzymes that enter with food. Hydrochloric acid is secreted in response to vagus nerve stimulation or pepsin secretion. Parietal cells are large and pyramid shaped, with a higher abundance in the upper region of the glands.
'''Gastrin''' is released from pyloric G cells; '''Somatostatin''' is released from pyloric D cells and '''histamine''' is released from Enterochromaffin-like cells (ECL cells).
[[Image:Lamina muscularis 3 regions.jpg|thumb|right|250px|Lamina Muscualris 3 Regions - Copyright RVC 2008]]
Stomach glands are short, coiled, branched and tubular. They need to be replaced due to wear and tear and are only found in the mucosal layer.
[[Image:Lamina muscularis 3 regions.jpg|thumb|right|150px|Lamina Muscualris 3 Regions - Copyright RVC 2008]]
==Digestive Enzymes==
==Digestive Enzymes==