anatomy of GI tract Flashcards Preview

HUBS192 GI > anatomy of GI tract > Flashcards

Flashcards in anatomy of GI tract Deck (58)
Loading flashcards...

structures of GI tract

oesophagus, stomach, small intestine (duodenum, jejunum, ileum), large intestine (cecum, ascending, transverse, descending, sigmoid), rectum, anal canal


primary functions of GI system

motility, secretion, digestion and absorption


accessory organs

salivary glands, pancreas, liver, gallbladder, appendix


what is peritoneum

Serous membrane made of simple squamous epithelium with underlying thin layer of connective tissue


types of peritoneum

  1. Parietal peritoneum - lines abdominal and pelvic cavities

  2. Visceral peritoneum - covers external surfaces of most abdominal organs, including intestinal tract

  3. Mesentery - double layer of peritoneal membrane from the body wall to the organ - gives passage to blood vessels, nerves and lymphatics 

  4. Omentum - double layer of peritoneal membrane from organ to organ 


function of peritoneum

  • Form covering (partial or complete) for abdominal organs
  • Smooth lining - frictional surface
  • Hold organs in position
  • Omentum and mesentery serve as fat store
  • Fats of peritoneum prevents infections of abdominal organs


3 main subdivisions of abdominal GI blood supply

  • Celiac trunk supplies foregut with blood
  • Superior mesenteric supplies midgut with blood
  • Interior mesenteric supplies hindgut with blood


divisions of celiac trunk

common hepatic, left gastric and splenic arteries


divisions of superior mesenteric artery 

intestinal arteries, ileocolic artery, colic artery


divisions of inferior mesenteric artery

left colic artery, sigmoid arteries, superior rectal artery


why is there large blood supply to small intestine

maintain concentration gradient for absorption of nutrients from GI tract


4 layers of gut tube

  1. mucosa
    • has gland ducts
  2. submucosa
    • connective tissue
    • glands
    • nerves called meissners plexus
  3. muscularis
    • smooth muscle
    • myenteric plexus
    • inside = circular
    • outside = longitudinal
  4. adventitia
    • FCT


3 layers of mucosa

  1. epithelium - mucus secreting
  2. lamina propria (loose FCT)
    • lymph nodes
    • nerve fibres
    • blood vessels
  3. muscularis mucosa (thin layer of smooth muscle)


control of digestion

  • enteric NS (primary control - independent, short, local reflexes)
  • CNS (modulates activity of ENS - long neural reflexes)
  • hormones
  • receptors


types of epithelium in GI tract

  • Simple squamous in peritoneum

  • Simple cuboidal lining ducts

  • Simple columnar lining stomach to rectum - this is modified to carry out specific functions

  • Stratified squamous lining oesophagus and anal canal (hardwearing protects against abrasion)

  • Glandular epithelium secrete mucus in small intestine


how are epithelial cells in GI tract joined

joined by tight junctions, zonula adherens and spot desmosomes to form a continuous and relatively impermeable membrane


function of mouth in GI tract

mechanical digestion via mastication (chewing) 


3 pairs of salivary glands, where they are and what they secrete

  1. sublingual - under tongue, mainly mucous, 3-5% of total saliva
  2. parotid - anterior and inferior to ear, serous fluid, 25-30% of total saliva
  3. submandibular - floor of mouth, both mucous and serous fluid, 60-70% of totoal saliva 


how are salivary glands controlled

parasympathetic NS


function of saliva

  • moisten ingested material 
  • moistens, cleanses and lubricates structures of oral cavity
  • begins chemical digestion of carbohydrates with amylase
  • antibacterial action with lysozyme
  • dissolves food to stimulate taste receptors


structure of oesophagus

  • appears collapsed when there is no food going down
  • mucosal epithelium - protective stratified squamous
  • muscularis externa - move food bolus, transitions between skeletal and smooth


structure of oropharynx

  • posterior to oral cavity
  • contains palatine and lingual tonsils
  • stratified, squamous epithelium for protection


regions of stomach

  • fundus is round bit at top
  • cardia is where oesophagus joins
  • body is main region
  • pylorus is where it leads into duodenum
  • greater omentum attached to greater curvature
  • lesser omentum attached to lesser curvature


greater omentum structure and function

  • large apron-like fold of visceral peritoneum that hangs down from the stomach over the small intestines and doubles back up to the transverse colon
  • functions are fat deposition, immune contribution, infection isolation


structural features of stomach

  • pyloric sphincter separates stomach and duodenum - controlled release
  • lower oesophageal sphincter separates stomach from oesophagus - prevents gastric juices flowing up
  • 3 layers of smooth muscle: oblique (inside), circular and longitudinal - mechanical digestion
  • rugae are folds in inside of stomach - allow expansion


mucosal layer of stomach

  • infolding of epithelium forms pits and glands
  • glands contain mucous neck cells, chief cells, parietal cells and endocrine cells


functions of stomach

  1. storage of food - rugae
  2. mechanical digestion - 3 layers of muscularis externa
  3. chemical digestion - breakdown of proteins
  4. some absorption (fat soluble substances e.g. alcohol)


function of liver

accessory organ that produces bile salts, which emulsify lipids, aiding their digestion and absorption


chief cell function and structure

  • secretes enzymes – pepsinogen converted to pepsin
  • Has many rough ER
  • Tight junctions between them to prevent acid moving between them
  • granules near apical surface


parietal cell function and structure

  • Pumps H+
  • Lots of mitochondria
  • Large SA
  • Folded with microvilli