Digestive System Flashcards
Components of the tubular part of the alimentary tract?
esophagus, stomach, small intestines, large intestines
4 concentric layers of alimentary canal?
mucosa, submucosa, muscularis externa, serosa/adventitia
Components of mucosa?
epithelium, lamina propria (w lymphatic tissue), muscularis mucosae
Components of submucosa?
dense irregular connective tissue
Components of muscularis externa?
2-3 layers of smooth muscle, often longitudinal and circular muscle. Also has an Auerbach nerve plexus between muscle layers
Components of serosa?
squamous epithelium and connective tissue
Components of adventitia?
connective tissue
Serosa vs Adventitia?
Serosa is present in peritoneal cavity while adventitia is found on retroperitoneal organs that are joined to other tissue/organ
Function of mucosal layers?
secretion, absorption, and protection
Function of muscularis externa?
rhythmic contraction that produces peristalsis
Function of esophagus?
transport food and liquid from pharynx to stomach
Describe muscosa of esophagus.
nonkeratinized stratified squamous epithelium with thin lamina propria with cardiac glands
Describe muscular transition of esophagus.
upper third is all skeletal muscle (voluntary control), middle third is mixed, lower third is all smooth muscle (involuntary control)
What can an incompetent inferior esophageal sphincter cause?
chronic heartburn and erosion of the mucosa (GERD)
4 regions of the stomach?
cardia, fundus, body, pylorus
What is rugae?
the large longitudinal mucosal folds of the stomach; they disappear when the stomach is distended
Function of stomach?
digestion; adds acidic fluid to content and mixes into chyme
Describe mucosa of stomach.
simple columnar epithelium, lamina propria with glands & CT w lymphatic cells, typical muscularis mucosa
Describe the submucosa of the stomach.
thick and not easily divisible into layers, forms the core of rugae
Describe the muscularis externa of the stomach.
inner oblique layer, middle circular layer, outer longitudinal layer (these 3 layers are important to churn food)
What type of cells is the surface epithelium of the stomach composed of?
surface mucous cells
Function of mucous cells?
produce alkaline mucous to protect the stomach
Describe the epithelium of the GI tract.
the esophagus has stratified squamous epithelium but the remainder has simple columnar
What are the 5 types of cells in gastric glands?
mucous neck cells, chief cells, parietal cells, enteroendocrine cells, stem cells
Role of chief cells?
secret pepsinogen
Role of parietal cells?
secrete HCL and intrinsic factor which facilitates the absorption of vitamin B12 in the ileum
Role of enteroendocrine cells?
secrete a variety of gastric hormones into the lamina propria
Location of chief cells and parietal cells?
Chief cells are found in the deeper part of the gastric glands and parietal cells are more numerous in the upper part of the glands
Describe the appearance of parietal cells?
large and pyramidal in shape
Where does cell division in the stomach occur?
at the isthmus where the stem cells are located
Describe cell movement and duration of cell life in the stomach?
Most new cells move up to become surface mucous cells which live 3-5 days which other cells move down to become gland cells. Parietal cells live about 6 months while chief and enteroendocrine cells live about 3 months