GASTROINTESTINAL SYSTEM ANATOMY I Flashcards
what are the roles of the GI system?
- motility
- secretion
- digestion mechanically and chemically
- absorption
what are the key structures in the GI system?
- long tube with outgrowths
- sphincters to seperate sections of the tube
- different environment within different organs
- lined by epithelium
what are the major organs of the digestive tract?
- oral cavity (mouth)
- pharynx
- esophagus
- stomach
- small intestin
- large intestine
what are the accessory organs of the digestive system?
- teeth
- tongue
- salivary glands
- liver
- gallbladder
- pancreas
where can you find stratified squamous type of epithelia in the GI system? what does that do?
- mouth, esophagus
- anus
- to protect from abrasion
_____1______, ______2_______, _______3______ are made of simple columnar, this serves the purpose of ______4______ and _______5______
1: stomach
2: small intestine
3: large intestine
4: secretion
5: absorption
the epithelium is also being invaginated to form glands, what are the 2 types?
- unicellular - goblet cells
- multicellular
describe the unicellular glands, where can you find them?
- columnar, goblet shaped with apical mucous granules and basal nucleus
- can be found in small intestine
describe the 2 structures of multicellular gland and where to find them?
- simple: gland with single duct, e.g. stomach and small intestine
- compound: gland with 2 or more ducts, e.g. salivary glands
what are the 4 layers of the gut tube (from inside contact with lumen to out)?
- mucosa
- submucosa
- muscularis (externa/proper)
- adventitia
what is the mucosa consist of?
- epithelium
- basement membrane
- lamina propria (FCT)
- muscularis mucosae
(- sometimes glands)
what is the submucosa consist of?
- FCT
- glands
- blood vessels
what is secretion regulated by?
submucosal nerve plexus (part of ENS)
what type of muscle made up the muscularis?
smooth muscle
what are the 2 main layers of muscularis?
- inner circular
- outer longitudinal
which specialised structure located between the 2 main layers of muscularis and what does it do?
- myenteric plexus (part of ENS)
- regulates motility
what could be the function of having 2 layers of smooth muscle with different orientations?
to serve the motility patterns - different orientation cause different movements of the gut tube
why might there be glands in both the mucosa and submucosa in some regions?
more SA if more secretion needed or more protection provided
what type of process happen in mouth?
- beginning of digestion: mechanical and chemical (starch)
- lubrication by saliva
what epithelium lines the mouth?
stratified squamous
what is the pathway of food through mouth?
fauces –> oropharynx –> laryngopharynx –> esophagus
what are the 4 accessory structures in mouth?
- hard and soft palate
- uvula
- tongue
- duct for submandibular beneath the tongue
what stimulates salivary glands?
parasympathetic nervous system
what are the 3 major pairs of salivary glands and where are they located?
- parotid: besides ear
- sublingual: tongue
- submandibular: edge of mandible
what do the 3 major pairs of salivary glands secrete?
- parotid: serous fluid with amylase
- sublingual: mucus
- submandibular: mixed
______________ is the cells in clusters which can secrete serous fluid, amylase and mucus
acinar/acinus
which cell secrete bicarbonate for buffering?
duct cells
what is the length of esophagus?
approximately 25cm
where is the esophagus situated?
- posterior to trachea
- from pharynx to stomach
which structure ensures food enters esophagus, not trachea?
epiglottis
describe the change in muscle type of the muscularis externa of the esophagus?
- first 1/3: skeletal msucle
- middle 1/3: mixture
- last 1/3: smooth muscle
what is bolus?
a ball-like structure mixed between food and saliva
what specialised structure we can find lines the wall of esophagus and what does it do?
highly folded submucosa and mucosa –> capacity to expand for passage for bolus
what is the epithelial type of esophagus?
stratified squamous
esophagus needs _____________ for lubrication and protection
mucus
how and where does mucus secrete in esophagus?
- in glands with ducts to surface in submucosa, and mucosa close to the stomach
what is peritoneum?
a serous membrane which lines the abdominopelvic cavity
what is retroperitoneal, what are the retroperitoneal organs?
- posterior to peritoneum
- pancreas and duodenum (initial segment of intestine)
what is mesentery?
double layer of visceral peritoneum that connects organ to body wall
what is omenta?
double layer of visceral peritoneum that connects an organ to another organ
what shape is the stomach and where is it located?
- J-shaped
- base of esophagus
where does the esophagus pass through?
diaphragm (esophageal hiatus)
what prevents reflux of the stomach?
lower esophageal sphincter (LES)
what are the 4 main parts of the stomach?
- cardia
- fundus
- body
- pylorus (pyloric antrum)
what are the 2 types of omentum?
- lesser omentum which connects stomach to liver
- greater omentum which connects stomach to transvers colon and rich in immune cell
- omentum has lots of adipose
what helps the 4 layers of gut tube carry out there special function?
- modification
- e.g. modification in muscularis for motility
what are the 3 layers of muscularis of stomach?
- oblique (inner)
- circular (middle)
- longitudinal (outer)
where is the muscularis thickest and why?
- distally (bottom) of the stomach, where food is stored and most of the proccess happens
what are the stomach wrinkles normally known as and what are their function?
- rugae
- allows expansion of stomach for storage
what does rugae originally from?
core of submucosa
what is the epithelia type of the stomach?
simple columnar epithelium
what are the special structures that is modified on the mucosa of the stomach?
gastric glands
why does stomach need gastric glands?
because the stomach needs:
- acid and enzymes for digestion
- mucous for protection
- hormones for regulation
what are the 3 cell types of gastric glands?
- parietal cells
- G cells
- chief cells
what do G cells secrete?
hormone - gastrin
what do chief cell secret and what specialised structure allows that?
- enzymes
- structure abundant of rER with apical zymogen granules (contain pepsinogen) and basal nucleus
what do parietal cell secret and what specialised structure allows that?
- acid (pump H+)
- abundant of mitochondria, central nucleus and folded structure to increase the surface area
what are the 2 parts of gastric gland?
- gastric pits: proximal (sits on top) where you can fine mucous epithelial cells
- gastric glands: sits deep under gastric pits, contain the 3 cells types
where can you find endocrine cells of stomach?
mucosa
what are the 2 secretion for endocrine control of the stomach?
gastrin and ghrelin
what are the neural controls of the stomach?
- enteric nervous system (ENS): controlling what is happening in GI system (e.g. motility)
- CNS modulates ENS function
what is chyme, what is its property?
chyme is the mixture of food and stomach secretion that is being delivered to small intestine for further digestion, chyme is acidic
what are the 4 main parts of the pyloric?
- pyloric antrum
- pyloric canal
- pyloric orifice
- pyloric sphincter
because chyme is acidic, what do we need to protect the stomach and where does it come from?
- mucous: from glands in submucosa of the duodenum
- neutralise acid: bicarbonate from pancreas
how is the pancreas situated?
- head in C-shaped duodenum
- tail to spleen
- posterior to stomach
- duct into duodenal lumen
TRUE/FALSE: the pancreas only has endocrine function
FALSE
- the pancreas has both endocrine and exocrine function
briefly describe the endocrine and exocrine function of pancreas?
- endocrine: alpha cells secrete glucagon, beta cells secrete insuline
- exocrine: acinar cells secrete digestive enzyme, duct cells secret bicarbonate
which cell type of the pancreas secrete enzyme?
acinar
which cell type of the pancreas secrete bicarbonate?
duct cells
what is the structure of the pancreatic acinar cells?
- apical zymogen granules
- basal nucleus
- abundant rER
where else have we seen a similar structure of cell like the acinar?
chief cells in stomach
where is the bile duct meet pancreatic duct?
hepatopancreatic ampulla
which part of the combined duct projects into the duodenal lumen?
duodenal papilla
what controls the release of secretion of ducts?
hepatopancreatic sphincter
what are the key structures of the stomach?
- LES prevents reflux into esophagus
- 4 regions: cardia, fundus, body and pyloris
- pyloric sphincter controls entry into SI
what structures of the stomach are needed for storage and digestion?
- rugae
- 3 layers of muscularis
- gastric gland
what parts of the pancreas are important for secretion
- acinar cells secrete enzymes
- duct cells secret bicarbonate
- secretions enter hepatopancreatic ampulla then into duodenal lumen of SI
