Digestive I Flashcards
GI tract organs
- oral cavity
- phraynx
- esophagus
- stomach
- small intestine
- large intestine
accessory digestive organs
- teeth
- tongue
- salivary glands
- liver
- gall bladder
- pancreas
digestive system functions
- ingestion
- digestion
- propulsion
- secretion
- absorption
- elimination of waste
peristalsis
ripple like wave of muscular contraction that forces material to move further along GI tract
propulsion of food along GI tract
- peristalsis
- segmentation
segmentation
- curing and mixing of material helping to disperse the material and mix it and combine with digestive organ secretion
oral cavity
- cheeks, lips, palate
- tongue
- salivary glands
- teeth
cheeks
- cheeks form lateral wall of oral cavity and are comprised mainly of buccinator muscles
- cheeks end anteriorly as the lips
lips
- gingival cover alveolar processes of teeth
- internal surface of upper and lower lips are attached to the gingival by a thing, midline mucosa fold called labial frenulum
palate
- forms rood of oral cavity
- anterior two thirds is called hard palate comprised of the palatine bones
- posteriori one third is soft palate comprised of muscle
- extending from soft posteriorly is uvula, which elevates during swallowing and closes off posterior entrance to nasopharynx
tongue
- manipulates and mixes ingested materials during chewing and helps compress the material into bolus
- inferior surface attaches to floor of oral cavity by ad thin, midline mucous membrane called lingual frenulum
bolus
- a bolus needs to be moistened and is a globular mass of injected materials that can be more easily swallowed
salivary glands
- produce and secrete saliva into oral cavity
functions of saliva
- moistens ingested materials to become slick bolus
- moisten, cleanses, and lubricates structures of oral cavity
- chemical digestion of ingested materials ( has some digestive enzymes)
- antibacterial action
- dissolved materials so that taste receptors can be stimulated
pairs of salivary glands
1) parotid glands
2) submandibular glands
3) sublingual glands
- serous cells secrete saliva that is 97-99% water, enzymes, ions
- mucous cells secrete mucin
parotid glands
- large salivary gland
- near ear
- more serous cells
submandibular glands
- under mandible
- produce 70% of saliva
- more serous cells
sublingual glands
- under tongue
- produce 3-5% of saliva
- more mucous cells
teeth
- collectively dentition
- exposed crown, constricted neck, and 1 or more roots that fit into a dental alveoli
- dentin forms primary mass of tooth, harder than bone
- each root is covered with cementum
- external surface of dentin is covered with layer of enamel that forms the crown of tooth
- centre of tooth is pulp cavity that contains connective tissue called pulp
- root canal opens into the connective tissue through an opening called the apical foramen
- blood vessels and nerves pass through this opening and are housed in the pulp
deciduous teeth
- erupt between 6-30 months
- 20 in number
- milk teeth
permanet teeth
- replace deciduous teeth
- 32 in number
how teeth are replaced
- osteoclasts above tooth destroys bone
- osteoblasts below tooth forms new bone and pushes tooth up
types permanent teeth
- incisors
- canines
- premolars
- molars
incisors
- most anteriorly place
- shaped like chisels
- single root
canines
- posterolateral to incisors
- pointed tips for puncturing and tearing
premolars
- posterolateral to canines
- have flat crowns with prominent ridges called cusps for crushing and grinding
molars
- thickest and most posterior
- adapted for crushing and grinding
pharynx
- respiratory and digestive
- 3 skeletal muscle pairs of pharyngeal constrictors (superior, middle, inferior) form the wall of the pharynx and participate in swallowing
- CN X (vagus) innervates most pharyngeal muscles
- branches of external carotid arteries supply the pharynx
- internal jugular veins drain the pharynx
pharyngeal constrictors
- superior: skeletal muscle
- middle: mixed skeletal and smooth muscle
- inferior: smooth muscle
deglutition oral/buccal stage
- upper esophageal sphincter is closed
- food is chewed and mixed with saliva in preparation for swallowing
- tongue presses against hard palate, forcing bolus into oropharynx
deglutition pharyngeal stage
- tongue blocks mouth
- soft palate and uvula rise, blocking nasopharynx
- larynx rises so epiglottis covers trachea
- upper esophageal sphincter relaxes, bolus travels down into esophagus
deglutition esophageal stage
- pharyngeal constrictor muscles contract and move bolus inferiorly down esophagus
- upper esophageal sphincter closes behind bolus
wall of abdominal GI tract
- 4 concentric layers (tunics) from deep to superficial: - mucosa - submucosa - musularis - adventitia or serosa
mucosa
- superficial epithelium
- underlying areolar connective tissues called lamina propria
- thin layer of smooth muscle called muscular mucosae
submucosa
- lymphatic ducts
- mucin-secreting glands
blood vessels - nerve
- where all digestive glands are anchored
- nerves and their associated ganglia are the submucosa nerve plexus
muscularis
2 layers of smooth muscle
1) inner circular: constricts lumen and forms sphincters (peristalsis)
2) outer longitudinal: shorten tube (segmentation)
- exception for esophagus that has a mix of moth and stomach that has 3 layers
- nerve fibers and associated ganglia between two layers of muscles is called the myenteric nerve plexus
adventitia or serosa
- outermost layer
- loose areolar connective tissue with collagen and elastic fibres
esophagus
- tubular passageway that conducts ingested materials from pharynx to stomach
- posterior to trachea
- passes through opening in diaphragm called esophageal hiatus as it connects to stomach
- approx 25 cm long
- about 1.5 cm is in abdomen prior to entering stomach
stomach
- upper left quadrant of abdomen
- continue mechanical and chemical digestion of bolus
- bolus eventually processes into paste like soup called chyme (processed quickly)
- has 3 layers of muscle to aid in mechanical processing of ingested materials
regions of stomach
- cardia
- fundus
- body
- pylori
- inferior border is greater curvature
- superior border in inferior curvature
- internal surface is in folds called gastric folds or rugae
wall of stomach
- lined by simple columnar epithelium although little absorption occurs in stomach
- stomach lining is indented by numerous depressions called gastric pits
gastric secretions
- along and at base of gastric pits are openings of gastric glands that secrete products into stomach
gastric glands
- surface coucous cells: secrete mucin
- mucous neck cells: secretes acidic mucin
- parietal cells: secreted hydrochloric acid and intrinsic factor
- chief cells: secreted pepsinogen (not activated until it comes up into stomach and is activated by hydrochloric acid), converted to pepsin when active (its a zymogen(inactive precursor) for pepsin)
- enteroendocrine cells: digestive cells, secretes gastrin hormone
ulcer
- parietal cells are secreting way too much hydrochloric acid of mucous cells and not sending enough mucous
- essentially, stomach starts to digest itself
stomach sphincters
- cardiac sphincter: lower esophageal, regulates entrance of bolus from esophagus to stomach
- pyloric sphincter; regulates release of chyme form stomach into small intestine
food usually stays in stomach for 4-6 hours
