Gastrointestinal Tract & Motility Flashcards
describe the oropharyngeal stage of the swallow
- at start of swallow, tongue presses bolus against hard palate
- tongue propels bolus to pharynx
- elevation of uvula prevents food from entering nasal
- position of tongue prevents food from reeterning mouth
- epiglottis folds over closed glottis
- contraction of pharyngeal muscles pushes bolus through opened pharyngeosophageal sphincter into esophagus
describe the oesophageal stage
- pharyngeosophageal sphicter closes, oropharyngeal structures return to resting postition
- peristalsis propels bolus down length of oesophagus
- satroesophageal sphincter relaxes as peristalsis pushes bolus into stomach
what are the layers of the digestive tract
- serosa
- muscularis externa (outer longitundinal muscle and inner circular muscle)
- submucosa
- mucosa (mucous membrane, lamina propia, muscukaris mucosa)
what is the intrinsic nervous system of the GI tract
the enteric nervous system
where is the myenteric plexus
between the outer longitudinal and inner circular smooth muscle layers
where is the submucosal plexus
between the circular muscle layer and the mucosa.
what are the three sections of the stomach
fundus
body
antrum
what secretory cells are in the oxynitic mucosa
mucous cells
chief cells
parietal cells
ECL cells
what do muscous cells secret
alkaline mucous
what do chief cells secret
pepsinogen (protien breakdown)
what do parietal cells secret
hydrochloric acid
intrinstic factor
what is the cardia
where. the oesophagus enters the stomach
what endocrine cells are in the pyloric gland
G cells
D cells
what do ECL cells secret
histamine (stimulates parietal cells)
what do G cells secret
gastrin
what do D cells secret
somatostatin (inhibits G cells, ECL and parietal cells)
where are the two gastric glands
oxyntic mucosa - body of stomach
pyloric gland - antrum of stomach
how is the mucosal barrier created
- the luminal membranes of the gastric mucosal cells are impearmeable to H+ so that HCI (hydrochloric ions) cannot penetrate into cells
- the cells are joined by tight junctions that prevent HCI from penetratig between them
- the mucus coating over the gastric muscosa offers further protection
what are the three parts of the small intestine
duodenum
jejunum
ileum
what enzymes are bound in the villus membrane
Enteropeptidase
Disaccharidases
Aminopeptidases
what is the function of the enxyme bound enzymes in the membrane of the villi
carbohydrate and protein digestion
where is appendix
cecum
what is the function of the sigmoid colon
to store fecal wastes until they are ready to leave the body
what organ is a mixed gland
pancreas
what cells in the pancreas are exocrine
duct cells (secret bicarbonate) and acinar cells
what cells in the pancreas are endocrine
islets of lngerhans - secret insulin and glucagon
what is the function of hepatic portal vein
carries nutrients from small intestine into liver
where are interstitial cells of cajal
in inner circular muscle layer of the muiscularis externa
what is the function of interstitial cells of cajal
produces wave like contractions to digestive systems
how often does the entire stomach lining replace itself
every 3 days
what is the border of the parotid gland
zygomatic arch, mandible, masseter muscle
what does the parotid gland secrete
- amylase
- saliva
what type of gland is the parotid
serous
where does the parotid duct drain
into cheek opposite maxillary 2nd molar (parotid papilla)
where oe sthe submanidibular duct emerge
from deep part to open on sublingual papilla
where does sublingual duct drain
*Drains into oral cavity via several minor ducts
what type of gland is the sublingual
mixed serous and mucous gland
what type of gland is the submandibular
seromucous gland
what are the teniae coli
These are three longitudinal bands of muscle that run along the colon.
They help in contracting the colon and forming haustra
what are the haustra
These are pouches or sacs in the colon.
They form due to the contraction of teniae coli and help in the slow movement of waste through the large intestine.
what initiates contractions in the large intestine
BER (Basic Electrical Rhythm)
what are the steps of the defaecation reflex
- Feces move into and distend the rectum, stimulating strech receptors there. The receptors transmit signals along afferent fibers to spinal cord neurons
- The spinal reflex is initiated in which parasympathetic motor fibers stimulate contraction of the rectum and sigmoid colon, and relaxation of the internal and sphincter
- if it is convenient to defecate, voluntary motor neurons are inhibited, allowing the external anal sphincter to relax so feces may pass
what permits defaecation
Voluntarily raising intra-abdominal pressure and relaxing external sphincter
