Gastrointestinal System Flashcards
germ layer for GI
- endoderm
structural origin for GI (3)
- foregut
- midgut
- hindgut
forgut derivatives (6)
- esophagus (oesophagus)
- stomach
- proximal duodenum
- liver
- gallbladder
- pancreas
where does the foregut end?
- distal to the liver
key processes of the foregut (2)
- stomach rotation
- accessory digestive organs
what is stomach rotation and where does it rotate along? (4)
- rotation along longitudinal access
- 90 degree clockwise
- dilates to form ‘correct shape’
- lesser and greater curvatures
what are accessory digestive organs?
- ‘support’ organs for digestion
examples of accessory digestive organs (3)
- liver
- gallbladder
- pancreas
when and how do accessory digestive organs develop?
- little growth off of foregut
- Wk 3 = develops rapidly
what do liver buds develop from?
- liver diverticulum
what does the liver bud invade?
- septum transversum
- nearby tissue, gives rise to diaphragm
what comes off the liver bud ventrally? (2)
- gallbladder
- cystic duct
where do ventral and dorsal pancreatic buds come from?
- endoderm in duodenal region (ventral part close to bile duct)
how fast is the growth of liver and gallbladder
- rapid
what happens when duodenum starts to bend?
- rotation of ventral pancreas
- reposition of dorsal pancreas eventually fuse, including pancreatic ducts
what are the midgut derivatives (4)
- distal duodenum
- intestinal loops (jejunoileal loop)
- ascending colon
- proximal 2/3 transverse colon
key process of midgut
- physiological umbilical herniation
what is the vitelline duct?
- connection between yolk sac and primary intestinal loop of midgut, via connecting stalk
what is allantois
- vestigial structure
- resp waste storage in avian embryos
what does the liver do to the insertional loops? and why?
- rapid growth of liver, requires more space then in growing abdomen
- intestinal loops temporarily leave the body into umbilical region Wk6
- retract Wk10
what is an omphalocele?
- rare cogenital abnormality abnormaly wall defect
- abdominal viscera herniate out of body, but do not return correctly
- covered by thin membrane prognosis
- treatment depends on extent, types and sizes
hindgut dervatives (5)
- distal 1/3 of the transverse colon
- descending colon
- sigmoid colon
- rectum
- proximal part of anal canal
key process of hindgut
- formation of urorectal septum
what is the cloaca (cloacal membrane)
- common chamber for hindgut and urinary systems
- anterior portion -> urogenital sinus
- posterior portion -> anus
what region does the urorectal septum form from?
- allantois region
what does the urorectal septum do?
- seperates the cloaca into anterior (urogenital portion) & posterior (anorectal canal)
- separates urinary and GI systems
what is the oral cavity split into?
- oral vestibule
- oral cavity proper
what is the oral vestibule?
- slit-like space between the teeth and gingivae, lips and cheeks
what is the oral cavity proper?
- space between upper and lower dental arches
anatomical borders of the oral (4)
- roof - hard and soft palette
- floor - muscles covered by oral mucosa, salivary glands and the tongue
- walls - the teeth when the mouth is shut
- buccinator muscle when the mouth is open
what is the oesophasgus and where does it extend between?
- fibromuscular tube that extends from the pharynx to the stomach
where does the oseophagus enter the abdominal region?
- T10
- through oesophogeal hiatus
what does the oesophagus join at T11?
- cardiac orifice of the stomach
food is transported through the oesophagus via ____?
- peristasis
what type of epithelium is present in the oesophagus and why?
- stratified squamous
- can swallow and damage walls
what four parts can the stomach be divided into?
- cardiac reigon - cardiac orifice
- fund - dilated superior part, either by gas, food or fluid/ or all of body of stomach
- body of stomach - major part
- pyloric region - contains the pyloric canal and pyloric sphinctor
which borders of the stomach form the lesser and greater curvate?
- medial and lateral borders
what are the ridges produced by folds in the stomach called?
- rugae
what are rugae for?
- so the stomach can expand when full
what is the first and shortest part of the small intestine?
- duodenum
what shaped courses does the duodenum follow?
- C-shaped
what 4 parts make up the duodenum?
- superior (1st)
- descending (2nd)
- inferior (3rd)
- ascending (4th)
what marks the end of the foregut and the beginning of the midgut?
- major duodenal papilla (small rounded protuberance)
where is the major duodenal papilla found?
- descending (2nd) part of the duodenum
what type of organ is the pancreas?
- glandular organ
- endocrine and exocrine
what 5 parts is the pancreas divided into?
- tail
- body
- neck
- head
- uncinate process
where does the jejunum begin?
- duodenojejunal flexure
- after ascending (4th) part of duodenum
where is the jejunum located?
- upper left quadrant of the abdomen
where is the ileum located?
- lower right quadrant of the abdomen
where does the ileum end?
- when it joins the caecum at the ileocaecal junction
jejunum vs ileium:
- vasa recta
- arterial arcades
- walls and internal surface
- long vs short
- few vs many
- thick/rough vs thin/smooth
what are pilcae circulares?
- large mucosal folds arranged circularly around the lumen
plicae circulares in jejunum vs ilium
- numerous in jejunum
- sparse in the ileum
what is the plicae circulares covered in?
- villi and microvilli
- increase surface area of small intestine
6 named parts of the large intestine (colon)
- caecum (with appendix)
- ascending colon
- descending colon
- transverse colon
- sigmoid colon
- rectum
where is the rectum located?
- pelvis
the rectum is continuous proximally to the ____ and distally with the ____
- sigmoid colon
- anal canal
the ____ and ____ terminate in the rectum
- teniae coli
- epiploic appendices
the rectum ends ____ to the tip of the coccyx, before the sharp _____ of the anal canal
- antero-inferior
- anorectal flexure
where does the foregut start and end?
- from oesophagus to 2nd part of duodenum
what is the foregut supplied by?
- coeliac trunk
foregut/artery arises from abdominal aorta at the level of T___?
- T12
where does the midgut start and end?
- 2nd part of duodenum to the 2/3rd of the way along transverse colon
what is the midgut supplied by?
- superior mesenteric artery?
midgut artery arises from the abdominal aorta at the level of ____
- L1
where does the hindgut start and end?
- 2/3rd way along transverse colon to superior part of rectum
what supplies the hindgut?
- inferior mesenteric artery
hingut artery arises from the abdominal aorta at level ____?
- L3
