GI system Flashcards
what are the functions of the digestive system?
digestion - process food
absorption - transfer of nutrients to circulation
what are the 2 groups of organs in the digestive system?
digestive tract
accessory organs eg salivary glands, gallbladder, liver, pancreas
what do the salivary glands do?
secrete a watery solution (serous) or a thicker solution (mucous) or a mix of these 2. it helps to buffer pH, protects surface id mouth and gut, has antimicrobial action and maintains tooth structure.
what does the gall bladder do?
helps store and concentrate bile which is produced in the liver and helps with fat digestion
what is the order of the GI tract
-oral cavity
-pharynx
-oesophagus
-stomach
-small intestine
-large intestine
what is the pharynx
muscular tube responsible for food and air to pass through. extends from base of the skill to oesophagus. conducts air, muscle directs food to oesophagus.
nasopharynx- base of skull to soft palate
oropharynx- soft palate to epiglottis
laryngopharynx- epiglottis to splitting into the trachea and oesophagus
what is the oesophagus?
muscular tube (20-25cm). extends from pharynx and reaches stomach. passes behind the heart and trachea. stratified squamous non keratinising.
changes from skeletal muscle at the top to smooth muscle at the bottom
what is the stomach?
muscular organ located in the upper right of the abdomen. secretes acid and enzymes that start digestion.
what are the small intestine?
3 parts, duosenum, jejunum, ileum.
duodenum - secretions from pancreas and bile enter at this point. bile helps with fat digestion and protein and other carbs.
what does the pancreas do?
its secretions help with the digestion of fat, protein digestion and starch and other carbs. it also secretes bicarbonate rich fluids to maintain an alkaline pH.
what happens to material not absorbed or digested by ilium?
moves to large intestine
how is GI tract seen histologically?
haematoxylin and eosin.
what is lamina propria?
thin layer of loose connective tissue which lies beneath the epithelium. contains inflammatory cells and provides support and nutrients to the overlying epithelium,
what is the mucularis mucosae?
composed of smooth muscle and is continuous all the way through the GI tract
what is the submucosa?
deep to the muscular mucosae. composed of dense irregular connective tissue and contains many blood vessels which collects additional fluid around the body outside the vasculature
what is the muscularis propria?
comprised of inner circular layer and outer longitudinal layer. smooth muscle and is responsible for peristalsis the movement of food.
what is the adventitia?
outer layer of fibrous connective tissue surrounding an organ. in the gut it would be at the oral cavity. it is the part of the tissue that is fixed. the serous membrane allows for reduction of friction.
what is meissners and auberbachs plexus?
nerve plexuses
what are brunners glands?
secrete biocarbonate ions to neutralise acid from the stomach
what are Peyers patches?
lymphoid follicles and form part of the immune function preventing the growth of dangerous bacteria.
what is the epithelium in colon?
simple columnar
how is the abdomen divided?
into 9 or sometime into 4 quadrants.
what are the 9 segments of stomach?
right hypercondrium- liver
epigastric - duodenum, liver, gall bladder, pancreas, stomach
left hypercondrium - spleen and stomach
right lumbar - ascending colon, kidney
umbilical n- stomach, head of pancreas, small intestine, transverse colon, lower aspects of right and left kidneys.
left lumbar - descending colon, left kidney
right iliac fossa - caecum, appendix, part of ascending colon
suprapubic - bladder, uterus, parts of small intestine
lest iliac fossa - sigmoid colon, descending colon,
where is the stomach located?
left hypercondrium and epigastric region
where does the greater momentum attach?
to the greater curvature
what does the pyloric sphincter do?
controls secretions from the stomach
what are rugae?
folds of the stomach which can be seen by naked eye and to increase surface area.
what do endocrine cells do?
produce hormone gastrin
what is found in the uppermost layer - mucosa?
endocrine cells
parietal cells (secretions of HCL)
chief cells (create pepsinogen)
mucous neck cell
what is the epithelium of the stomach onwards?
simple columnar
what is the small intestine?
primary site for digestion absorption
what do villi do?
increase surface area by 30 times. finger like projections increase SA and aid digestion and absorption. dimininsh in number towards the end of the tract.
how many layers of muscle does the small intestine have?
2
what is the function of the gall bladder (to aid digestion)?
helps store and concentrate bile which is produced by the liver and helps with fat digestion.
what does haematoxylin do?
stains the nucleus blue
what are sphincters?
circular muscles that open and close passages in the body to regulate the flow of substances such as bile, urine and faeces
what does eosin do?
stains the cytoplasm and ECM pink.
what is the epithelium like in the oesophagus?
stratified squamous and is non keratinised
where does the pharynx go to?
C6
what is the nasopharynx?
base of skull to the soft palate (top part of the pharynx)
what is the oropharynx?
soft palate to epiglottis
what is the epiglottis?
a flap of tissue that sits beneath the tongue at the back of the throat. main function is to close over the trachea while your eating to prevent food from entering airway.
where is the pylorus?
the very end of the stomach, just before it reaches the duodenum.
how many layers of muscle does the stomach have in the stomach wall?
3 which make up the muscularis propria
what is the fundus of the stomach?
dome shaped top section. dosent usually store food unless the stomach is really full. it generally stores gas byproducts of digestion.
which cells produce hydrochloric acid?
parietal cells which are stimulated by hormone gastrin
how do the villi change downwards in the intestine?
they decrease in numbers as you descend down the tract
what are the folds called in the small intestine?
plica
what is the exocrine section of the pancreas?
digestive component of the pancreas
-composes 99% of the pancreas
-has many digestive enzymes
-has biocarbonate ions
what is the endocrine section of the pancreas?
hormones
-insulin (promotes glucose absorption from blood into the liver. enables the conversion to glycogen)
-glucagon (works in opposite way to insulin, converses stored glycogen into glucose for release into blood when levels are low)
somatostatin (reduces acid secretion and slows digestive process)
what size is the liver?
-the largest gland in the body
-heaviest of our internal organs (1.5kg)
how many lobes does the liver have?
looks like it only has 2 but actually has 4.
-left
-right
-caudate
-quadrate
what does the liver do?
produces bile which is then stored in the gall bladder and aids digestion in the small intestine
-detoxification
-synthesises proteins
-drug metabolism
what is the duct called that leaves the gall bladder for the bile secretions to come out?
cystic duct
what is the hepatic artery?
supplies about 25% of the oxygenated blood to the liver
what is the hepatic portal vein?
comes from the gut, spleen and related organs (75% deoxygenated blood) - brings nutrients
what is the common hepatic
comes from the left and right hepatic ducts which carry bile to the gall bladder. intrahepatic ducts unite to form the left and right extra hepatic ducts which links to the common hepatic duct.
what are the main functions the large intestines?
-absorption of water and electrolytes form chyme to form solid faeces
-vitamin K absorption
-storage of faecal matter
-transport (motility)
what happens to carbs and proteins that are not digested in the small intestine?
-fermented by colonic microflora to short chain fatty acids and gases
what is the colon?
the distal part of the GI tract and extends from the caecam at the right iliac fossa to the anal canal.
what is the caecum?
-acts as a resivoir for chyme
what is the ileocaecal valve?
between the caecum and ilium, prevents reflux of large bowel contents into the ileum during peristalsis
what are the 4 parts of the colon?
-ascending
-transverse
-descending
-sigmoid
(all around 150cm long)
what is the ascending colon
a retroperitoneal structure which ascends superiorly from caecum
what is the transverse colon?
extends from the right colic flexure to the spleen. least fixed part of the colon.
what is the descending colon?
moves inferiorly towards the pelvis. located anteriorly to the left kidney
what is the sigmoid colon?
when it starts to turn medially, roughly 40cm long, located in left lower quadrant of abdomen.
what is the hepatic flexure?
when it meets the right lobe of the liver it Turns 90 degrees.
what are Teania coli?
3 longitudinal bands of smooth muscle on the outside of the ascending, transverse and descending colons
what is the haustra?
circumferential contraction of the inner muscular layer of the colon
what is appendice epiploicae?
pouches of peritoneum filled with fat mainly on the transverse and sigmoid colon.
what is the foregut?
supplies the oesophagus, stomach, liver, spleen and first half of duodenum
what does the midgut supply?
supplies the left half of the duodenum, jejunum, ileum, caecum, appendix, ascending colon to the first 2/3 of the transverse colon
what does the hindgut supply?
last 1/3 of the transverse colon, descending colon sigmoid colon and rectum
what is the femoral vein?
drains the lower limb (external iliac comes from this)
what is the internal iliac vein?
drains the pelvis
what do renal veins do?
drains the kidneys
what does the hepatic vein do?
main vein draining in the liver
Which layer of GI tract histology are meissners plexus found?
Submucosa
What are meissners plexus?
Neural network, transmits sensory afferent stimuli to CNS
the superior mesenteric artery supplies the?
proximal 2/3 of the transverse colon
what does bile help with?
digestion of fat
what do pancreatic secretions aid?
fat, protein, starch and carb digestion,
maintain alkaline pH
which part of the large intestine acts as a resivour for chyme?
caecum
what major branch of the abdominal aorta supplies arterial blood to the stomach?
coeliac trunk
what are the 3 muscle layers of the stomach wall?
outer longitudinal
inner circular
innermost oblique of smooth muscle
what is produced by chief cells?
pepsinogen
what is produced by mucous neck cells?
mucous which protects the surfaces from HCl
what is produced by parietal cells?
HCl
what Is the function of HCl?
denatures protein and activates pepsinogen
what does activated pepsinogen do?
breaks specific peptide bonds
what sphincter controls the secretions from the pancreas and bile duct?
sphincter of oddi
what do the exocrine secretions from the pancreas do?
break down peptides
where do the pancreatic secretions empty?
second part of duodenum via the sphincter of oddi with bile
where are platelets produced?
liver
where is the spleen located?
left hyochondrium
what is the arterial supply to the spleen?
splenic artery
what is the function of the spleen?
identifying, removing and destroying old red blood cells
stores red blood cells and platelets
what is the arterial supply to the small intestine?
superior mesenteric artery
how can we differentiate the large and small intestine?
large intestine has
-omental appendices (fatty tags)
-haustra (sacculations of the bowel wall)
-taeni coli (longitudinal bands of muscle)
what is the role of the caecum?
fluid absorption and commencement of fermentation of fibre and liquids, gas production and synthesis of some new vitamins
what is the blood supply to first 2/3rds of transverse colon?
superior mesenteric artery
what does the inferior mesenteric artery supply?
last 1/3rd of the small intestine
what are the histological layers of the small intestine?
mucosa
submucosa
muscular externa
adventicia
what is lacteal?
a vessel that absorbs fat in the small intestine
what two cell types comprise the colonic glands?
absorptive cells and mucous secreting goblet cells
where do the exocrine secretions of the pancreas pass to perform their function?
second part of duodenum
what is the name of the endocrine portion of the pancreas?
islets of langerhans
what are the liver cells called?
hepatocytes
what is the arterial supply to the gall bladder?
cystic artery
(comes from the right branch of the proper hepatic artery)
what main vessel does the specific arterial supply of the gall bladder arise from?
coeliac trunk
what are gall stones?
crystallised masses that can contain abundant cholesterol, pigment or a combination of both
