Quiz 2 Flashcards
Main structures of the digestive tract vs accessory
oral cavity
esophagus, stomach, small/large intestine
accessory- pancreas, liver, gallbladder
What are the layers of the digestive tract
lumen +4 layers
mucosa, submucosa, muscular externa, and serosa
Mucosa characteristics
First layer
mucosa- produces/releases secretions for digestion. Has 3 layers: epithelium (mucosal membrane) has exocrine and endocrine cells, lamina propria, and muscularis mucosa
Submucosa characteristics
submucosa- connective tissue, contains blood vessels, nerves, and lymphoid tissue
submucosal plexus; neurons and ganglia control local secretion, absorption, and muscle movements
Muscularis Externa
3rd layer
2 layers of smooth muscles
-circular/transverse
-longitudinal
GI tract motility or peristalsis
Serosa
4th layer
flat mesothelial cells
protects the GI tract against biochemical damages
Oral cavity structures and functions
mechanical breakdown, moistening and mixing food with saliva
Mouth and pharynx
salivary glands;
-parotid
-submandibular
-sublingual
Saliva composition and functions
99.5% water
electrolytes maintaining the balance of fluid in the mouth
Mucus: lubricates food for swallowing
Enzymes: salivary amylase, hydrolyzes alpha 1-4 bonds
antibacterial and antiviral proteins: protect against infections
r-protein: binds with vit. B12 aiding in absorption in the small intestine
Saliva keeps mouth and teeth hygienic/healthy and starts digestion process
esophagus
transports food from pharynx to stomach
Swallowing:
-oral phase: voluntary
pharyngeal and esophageal phase: reflex
Peristalsis is stimulated by NS and controlled by muscularis externa
Lower Gastroesophageal sphincter
Circular muscle, relaxes when we swallow
allows bolus to pass from esophagus to stomach
Stomach
muscular contraction; mixes food with acid/enzymes
causes chemical/physical breakdown of food into chyme
4 regions:
-cardia-fundus-body/corpus-antrum and distal pyloric sphincter
Glands in stomach wall
cardiac glands, oxyntic glands, pyloric glands
What are the cells in gastric oxyntic gland
Neck (mucus) cells
Parietal (oxyntic) cells- secrete HCl and intrinsic factor
Chief( peptic or zymogenic cells- secrete pepsinogen and gastric lipase
Enteroendocrine G-cells- secrete gastrin hormone that stimulate parietal and chief cells
also secretes gremlin(hunger), satiety hormones, stiimulate bile release CCK, Appetite regulation WHEN sense luminal content
What is gastric juice
HCl- activates pepsin, denatures protein, release nutrients, kill bacteria
3 enzymes
pepsin
gastic lipase
salivary amylase
Phases of gastric secretion
Cephalic- before food reaches stomach vagal stimuli enhances gastrin release promoting HCl secretion
Gastric- food is stomach, stomach distention, identified by stretch receptors enhances gastric secretion promoting HCl secretion
Intestinal- after stomach to duodenum, reduction in chyme volume and reduction in pH release somatostatin that inhibits HCl secretion
GASTRIN (secreted by, function)
secreted into blood by enteroendocrine cells in stomach lining
stimulates gastric acid
CCK
secreted into blood by enteroendocrine cells in the small intestine (d and j)
stimulates bile release
stimulate pancreas to release digestive enzymes
SECRETIN
secreted into blood by enteroendocrine cells in the small intestine (DJ)
stimulates pancreas to release bicarbonate
neutralizes stomach acid=
MOTILIN
secreted into blood by enteroendocrine cells in the small intestine
stimulates contraction of smooth muscles in digestive tract
aids in movement of chyme/food
The stomach has ____layers of ____. the innermost layer is _____. Peristalsis is strongest in what part of the stomach?
3 layers: Diagonal(oblique), circular, and longitudinal
strongest in the antrum
