anatomy of GI tract 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
- Parietal peritoneum - lines abdominal and pelvic cavities
- Visceral peritoneum - covers external surfaces of most abdominal organs, including intestinal tract
- Mesentery - double layer of peritoneal membrane from the body wall to the organ - gives passage to blood vessels, nerves and lymphatics
- 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
- mucosa
- has gland ducts
- submucosa
- connective tissue
- glands
- nerves called meissners plexus
- muscularis
- smooth muscle
- myenteric plexus
- inside = circular
- outside = longitudinal
- adventitia
- FCT
3 layers of mucosa
- epithelium - mucus secreting
- lamina propria (loose FCT)
- lymph nodes
- nerve fibres
- blood vessels
- 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
- sublingual - under tongue, mainly mucous, 3-5% of total saliva
- parotid - anterior and inferior to ear, serous fluid, 25-30% of total saliva
- 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