12 Flashcards
(24 cards)
pharynx
a chamber shared by the digestive and respiratory systems
- extends behind nasal and oral cavities to larynx/esophagus
- divided into three parts
nasopharynx
superior portion of the pharynx
- contains pharyngeal tonsils and openings to the eustachian tubes
- connected to nasal cavity
oropharynx
middle portion of the pharynx
-connected to oral cavity
laryngopharynx
inferior portion of the pharynx
- extends from hyoid bone to larynx
- where food and air separate
piriform sinus
recess on each side of the laryngeal oriffice
-act as side branches of the vocal tract
deglutition (swallowing)
starts voluntarily then proceeds automatically
- 3 phases: buccal, pharyngeal, esophageal phase
buccal phase
voluntary phase
- begins with compresson of bolus against hard palate
- then retraction of tongue forces bolus to orooharynx and assists in elevation of soft palate (sealing off nasopharynx)
pharyngeal phase
involuntary phase
- begins as bolus comes into contact with palatoglossal and palatopharyngeal arches, and pharyneal wall
- elevation of larynx and folding of epiglottis move bolus past closed glottis
- uvula and soft palate block passage of bolus back into nasopharynx
esophageal phase
involuntary phase
- begins with contraction of pharyngeal muscles which force bolus through opening of esophagus
- once in the esophagus, bolus moved to stomach via peristalsis
general histology of digestive tract wall (4 layers)
MUCOSA
- surface epithelium
- lamina propria (loose CT)
- muscularis mucosa (SM)
SUBMUCOSA
- dense irregular CT, contains bvs, lymphatics, glands
- submucosal/Meissners’ plexus supplies muscularis mucosa and glands
MUSCULARIS EXTERNA
- circular and longitudinal layers of SM
- myenteric/Auerbach’s plexus between layers
- peristalsis and segmentation
SEROSA -serous membrane that covers many structures or NO SEROSA = adventitia - dense fibrous CT
esophagus
hollow muscular tube - 25 cm long, 2 cm wide
- begins posterior to cricoid cartillage
- esophageal hiatus = where it enters abdominal cavity at T10
- no digestive action here
histology of esophageal wall
- mucosa - non-keritanized stratified squamous, lp, muscularis mucosae (irrgular SM)
- submucosa - mucus secreting esophageal glands
- *mucosa and submucosa form large folds that give esophagus room to expand**
- muscularis externa - upper 1/3 = skeletal, middle 1/3 = skeletal and smooth, lower 1/3 = smooth
- adventitia
esophageal sphincters
upper (pharynx - esophagus)
lower (esophagus - stomach)
-prevent regurgitation
stomach function
- mechanical processing of food - turns bolus to chyme
- storage of ingested food
- digestion of food - HCl and pepsin
- hormone production
- intrinsic factor production (important for smi)
stomach - anatomy
- j shpaed
- lesser curvature connected to lesser omentum (medial)
- greater curvature connected to greater omentum (lateral)
- extends between T7 and L3 (expands tho)
lesser omentum
- reminant of ventral messentary
- between stomach and liver
- stability and bv/etc. route
greater omentum
- develops from dorsal messentary
- huge pouch (“hangs like an apron”)
- extends between body wall and small intestine
- pad, protects, provides insulation, stores energy (made of fat cells)
regions of the stomach
-cardiac
-fundus
-body
-pylorus- connects to duodenum (pyloric sphincter)
two parts - antrum and canal (^)
histology of the stomach
- mucosa (folded - “rugae”) - simple columnar with microvili, goblet cells (produce mucus), gastric pits (neck cells replace surface cells), gastric galnds, lp, muscularis mucosae
- submucosa
- muscularis externa - 3 SM layers - outer longitudinal, middle circular (thickens to form pyloric sphincter), inner oblique
- serosa
cells of the fundic glands
parietal cells - secrete HCl (protein breakdown) and intrinsic factor (vitamin b12 absorbtion)
- large round cells woth central nucleus
- most abundant near top
cheif cells - secrete pepsinogen (converted to active form - pepsin by HCl)
- cuboidal cells with basal nucleus
- more abundant near base
gastric glands (2 types)
fundic glands (in fundus and body) pyloric glands (in pylorus)
cells of pyloric glands
mucus secreting (dominant) - goblet cells further break down bolus
enteroendocrine cells (scattered) - produce GI hormones
- D cells produce/secrete somatostatin (GH inhibiting hormone)
- G cells produce/secrete gastrin (stimulates parietal cells to make HCl)
arterial supply of stomach
from branches of the celiac artery:
- left gastric
- splenic
- common hepatic
venous drainage of stomach
corresponding veins run parrallel to left gastirc, splenic and common hepatic arteries
- drain into hepatic portal vein
