Basic science Flashcards
Histology, anatomy, embriology
what are the three major salivary glands?
sublingual
submandibular
parotid
where do the liver and pancreas develop?
as an outgrowth of the gut tube
which epithelium is the parenchyma of the liver and the pancreas composed of?
glandular epithelial cells
list some functions of the liver (9)
oxidise triglycerides to produce energy
synthesize plasma lipoproteins
synthesize cholesterol
convert carbohydrates and proteins to fatty acids.
regulate blood glucose
synthesize plasma proteins
detoxification of metabolic waste products
storage of glycogen, vitamins and iron
synthesis and secretion of bile
where does venous blood in the liver drain into and where does that drain to?
hepatic veins which drain to the IVC
what is the liver covered by and describe this?
collagenous connective tissue capsule (which is covered by mesothelial cells = simple squamous epithelium)
describe the structure of the liver.
made of lobules
each lobule is hexagonal, has a branch of the hepatic vein (central vein) at the centre and portal triads at the corners (each triad contains bile duct, portal vein and hepatic artery)
CT connects the lobules
what is a portal tract (in the liver) composed of?
hepatic portal vein
hepatic artery
bile ductule
(tracts also typically include lymphatic vessels)
what is the bile ductule (of the portal tract) lined by?
simple cuboidal cells = cholangiocytes
what are the main cells of the liver?
hepatocytes
what are the blood channels in the liver between the sheets of hepatocytes called?
sinusoids
what direction does blood travel in in the liver?
from the portal triads at the corners of the lobule, towards a hepatic vein at the middle of a lobule
what is the space of Disse and what is projected into that space?
the space between the lining epithelial cells of the sinusoids and the hepatocytes.
Microvilli of the hepatocytes project into that space
how is the epithelium of the sinusoids organised and why?
it is fenstrated so the liquid component of the blood has free access to the hepatocytes but the blood cells do not
what type of collagen is found in the space of Disse?
type I
where is type III collagen found in the liver?
in the parenchyma
What are hepatic stellate cells and where are they found?
modified fibrobasts
found scattered in space of Disse
what do hepatic stellate cells do?
make CT and store Vit A within fat droplets in their cytoplasm.
in cirrhosis they transform into myofibroblasts and produce scar tissue
what are Kupffer cells and where are they found?
resident macrophages found scattered within the sinusoids of the liver.
what do Kupffer cells do?
remove particulate matter from the blood and help remove worn out RBCs
what is bile?
an alkaline soultion containing water, ions, phospholipids, bilirubin and bile salts.
what is bilirubin in bile?
a pigment made from the breakdown of haemoglobin in the spleen (responsible for the brown colour of faeces)
why are bile salts necessary?
emulsification of fats in the digestive tract
which cells line the biliary tree?
cholangiocytes
How does bile flow through the lobules in the liver (remember all hepatocytes produce bile)
via bile canaliculi towards the bile ducts in the portal tracts
what are bile canaliculi (in the liver)?
small channels formed by tight junctions between cell membranes of adjacent hepatocytes
what is the gall bladder and what does it do?
a muscular sac which removes bile from the liver and stores and modifies it
what is the gall bladder lined with?
simple columnar epithelium with brush border backed by a lamina propria of loose CT rich in blood and lymphatic vessels. A coat of smooth muscle and an outer collagenous layer of adventitia
how does the gall bladder remove bile from the liver?
actively pumping Na and Cl ions from the bile into the spaces between adjacent epithelial cells (water follows and is carried away in lymphatic vessels in the lamina propria)
where does the gall bladder deliver bile to?
the duodenum
what stimulates the release of bile from the gall bladder into the duodenum?
nervous control, mainly vagal due to the release of cholecystokinin by endocrine cells of duodenum, secreted when fatty food enters it
what is cholecystitis?
inflammation of the gall bladder
how is the pancreas a dual functioning organ?
it is both endo and exocrine gland (mostly exo)
what does the exocrine pancreas do?
produces digestive juices containing proteases, lipases, nucleases and amylase.
what is the pancreatic duct for?
transferring exocrine pancreas juices into the duodenum
what does the endocrine pancreas consist of?
Islets of Langerhans (small scattered islands of tissue)
what do the Islets of Langerhans in the pancreas do?
produce a number of hormones (like insulin and glucagon)
how are enzymes produced by the exocrine pancreas activated?
by arriving at the duodenum where an enteropeptidase converts the inactive trypsinogen into the active form of trypsin, beginning a cascade of activating further enzymes
what is the pancreas covered by?
thin CT capsule that is continuous with CT septa that divides the glands into lobules
why do the acinar glands in the pancreas differ from in other glands?
the duct system goes straight into the core of the acinus whereas in salivary glands the duct joins its edge.
what is the hepatopancreatic ampulla?
an opening into the duodenum on a papillae composed of the pancreatic and common bile duct
what is the large intestine made up of?
colon (caecum, appendix, ascending transverse and descending colon, sigmoid colon)
Rectum, anal canal and anus
what is the small intestine made up of?
duodenum, jejunum, ileum
what are the three embryological catagorizations of the abdominal organs?
foregut
midgut
hindgut
where does the foregut begin and end and what accessory organs are within this?
oesophagus to mid-duodenum
liver, gallbladder, spleen and 1/2 of pancreas
where does the midgut begin and end and what accessory organs does it contain?
mid-duodenum to proximal 2/3rds of transverse colon
other half of pancreas
where does the hindgut begin and end?
distal 1/3rd of transverse colon to proximal 1/2 of the anal canal
what are all organs in each part of the fore, mid and hindgut supplied by (generally speaking)
arterial blood
venous drainage
lymphatic drainage
nerve supply
all via common route
what are the 9 clinical regions of the abdomen?
right/left hypochrondrium epigastric right/left lumbar/flank umbilical right/left inguinal/iliac fossa pubic/suprapubic/hypogastric
what lines divide the abdomen into its 9 clinical segments?
midclavicular
subcostal
trans-tubercular
how can the abdomen be split into quadrants (what lines)?
median and trans-umbilical planes
what organs are located in the RUQ? (generally)
liver, right kidney, right adrenal gland, transverse colon, part of small intestine
what organs are in the LUQ? (generally)
stomach, part of liver, other part of transverse colon, part of small intestine, left kidney and adrenal gland
what organs are in the RLQ? (generally)
appendix, ascending colon, small intestine
what organs are in the LLQ? (generally)
small intestine, descending colon, sigmoidal colon
which muscles are present in the abdominal muscle wall?
anteriorly = rectus abdominis
laterally = external and internal oblique, transversus abdominus
what is the peritoneal cavity, where is it and what does it do?
thin, transparent, semi-permeable serous membrane between the visceral and parietal layers.
lines walls of abdominopelvic cavity and organs.
secretes a small amount of lubricating fluid
what causes peritonitis and what is it?
severe and painful inflammation of the peritoneum.
due to blood, pus or faeces in peritoneal cavity
how can organs be classed in relation to the peritoneum and give an example?
intraperitoneal (liver)
retroperitoneal (kidney)
with a mesentery (intestines)
describe the motility of organs depending on their relationship to the peritineum.
intra = minimally mobile retro = minimally mobile mesentery = very mobile
what is a mesentery?
a double layer of visceral peritoneum surrounding an organ attaching it either to other organs of the body wall
what is the 4 layered flap that covers the abdomen anteriorly known as?
the greater and lesser omentum
what is the omental foramen?
where the greater and lesser omenta meet
where does the portal triad lie in relation to the omentum?
at the free edge of the lesser omentum
what are the pouches creates by the peritoneum called in males and females?
males = one pouch = rectovesical
females = two pouches: vesico-uterine pouch and recto-uterine pouch/pouch of Douglas
where is excess fluid in the abdominal cavity of a woman most likely to collect and why?
Pouch of Douglas/recto-uterine pouch as it is the most inferior part
what is ascites?
pathological collection of fluid in the peritoneal cavity
what is the procedure to treat ascites called?
paracentesis/abdominocentesis
where is the needle inserted in paracentesis and why?
lateral to the rectus sheath so to avoid the inferior epigastric artery
where does the inferior epigastric artery lie and where does it arise from?
anterior abdominal wall deep to the rectus abdominis
arises from external iliac, medial to the deep inguinal ring
how would visceral pain be localised and what character would it have?
not localised, dull, achy, nauseating
what are the four main questions you ask about abdominal pain?
location
character
timing
pain referral pattern
how would somatic pain be localised and what character would it have?
easily localised, sharp, stabbing
what could colicky pain suggest?
GI tract obstruction, as peristalsis comes in waves hence why not pain all the time
what types of nerves are present in the organs?
visceral afferents (sensory nerves)
ANS
ENS
what types of nerves are present in the body wall?
somatic sensory
somatic motor
sympathetic fibres
describe how sympathetic nerves get from the CNS to the abdominal organs and where they synapse.
CNS to spinal cord
leave between T5-L2
enter symp chains
leave chains with abdominopelvic splanchnic nerves
SYNAPSE at prevertebral ganglia and travel to organ on surface of arterial branches leaving the abdominal aorta.
Join periarterial plexuses and go with arteries to smooth muscle and glands of the organs
where are the prevertebral ganglia located?
anterior to the vertibrae on the anterior of the aorta
how does sympathetic activity reach the adrenal gland?
sympathetic nerve fibres leave spinal cord at T10-L1.
enter abdominopelvic splanchnic nerves
travel to prevertebral ganglia and carried with periarterial plexuses to the adrenal gland where SYNAPSE directly onto its cells
describe how parasympathetic nerves (from vagus) get from the CNS to the abdominal organs.
CNX (vagus nerve):
presynaptic fibres enter the abdominal cavity on the surfact of the oesophagus (vagal trunks)
then travel into the periarterial plexuses around the abdominal aorta
carried to the organ walls where SYNAPSE in ganglia.
what are the two ways the parasympathetic NS can affect the abdominal organs?
through vagus nerve
(cranial)
or through pelvic splanchnic nerves (S2,3,4)
What is another name for the para NS?
craniosacral - as outflow from both
describe how the peliv splanchnic nerves supply parasympathetic innervation to abdominal organs.
presynaptic parasympathetic nerve fibres come from spinal nerves S2,3,4
to smooth muscle/glands of the descending colon to anal canal
which part of the GI tract have para control by the pelvic splanchnic nerves?
descending colon to anal canal
in which clinical regions is abdominal pain felt from: the foregut, midgut and hindgut?
epigastric pain = foregut
umbilical region = midgut
pubic region = hindgut
how do visceral afferent nerves (sensory) get from the abdominal organs from the CNS?
pain fibres tend to run alongsided sympathetic fibres back to the spinal cord
where does the visceral afferents from the different parts of the gut feed into the spinal cord?
foregut structures = T6-T9
midgut structure = T8-T12
hindgut structures = T10-L2
what is referred pain?
pain being felt at the dermatome at the level the visceral afferents from the organ enters the spinal cord
what is contained in the thoracoabdominal nerves?
somatic motor, somatic sensory, sympathetic nerve fibres
where do the thoracoabdominal nerves supply and how?
the body wall of the abdomen (7th-11th intercostal nerves). they travel down and diagonally down in the plane between the internal oblique and trasversus abdominis
which part of the spinal cord does the subcostal nerve come from?
T12 anterior ramus
where does the iliohypogastric nerve come from?
half of the L1 ramus in the spinal cord
where does the ilioinguinal nerve come from?
half of L1 anterior ramus
why would appendicitis present initially as a dull ache in the umbilical area, and then as a sharper pain in the iliac fossa?
because the appendix is an organ so would convey visceral pain. Is a midgut organ so would feel in the umbilical region.
Will become sharper as the inflammation irritates and presses on the body wall creating somatic pain. It is located in the iliac fossa as this is where the appendix is.
which accessory organs are derived from the gut tube endoderm? (9)
Pharyngeal pouch derivatives Lungs Liver parenchyma and hepatic duct epithelium, gallbladder, cystic duct and common bile duct. Pancreas urogenital sinus and derivatives
pf which part of the gut are no accessory organs produced?
midgut
describe what happens to the endoderm during days 20-26.
it begins as an endodermal sheet/disc on the top with a yolk sac pouch underneath it.
the edges of the disc begin to fold down either side on day 24.
the yolk sac thins out to form a duct from the ‘gut tube’ that is now in a vague foetal position
where does the blood supply to the abdominal organs arise?
from the abdominal aorta
which artery supplies the foregut organs?
coeliac trunk
which artery supplies the midgut organs?
superior mesenteric artery
which artery supplies the hindgut organs?
inferior mesenteric artery
what is the vitelline duct and how is it formed?
A narrow space between the yolk sac and the midgut.
Formed by the opening between the midgut and the yolk sac being open and as folding continues it narrows forming the vitelline duct.
what is Meckel’s diverticulum and what does it cause?
a persistence of the vitelline duct forming an outpouching of the ileum.
it may become inflammed and harbour abnormal tissue, resembling appendicitis
what are the rule of 2’s for Meckel’s diverticulum?
2% of population 2 inches in length found 2 feet from ileocecal valve children under 2 yrs affects males 2x as much as females
what can meckel’s diverticulum result in?
a vitelline fistula meaning there is a direct connection between the ileum of the small intestine and the umbilicus
describe the formation of the oesophagus.
the foregut tube gives rise to the respiratory diverticulum at the end of week 3.
During weeks 4-7 oesophagus lengths rapidly due to descent of heart and lungs.
what is a short oesophagus and what can it result in?
failure of oesophagus to grow in proportion with the neck and thorax.
resulting in formation of a congenital hiatal hernia (part of the stomach is in the oesophagus, this will take up space and can affect respiration)
describe the formation of the stomach.
it begins as a fusiform dilation
dorsal wall undergoes rapid growth to form the greater curvature.
ventral wall growth is slower causing the lesser curvature
describe the rotations of the stomach during formation.
clockwise 90 degree turn around longitudinal axis (LARP)
anteroposterior axis rotation brings the pyloris upwards and the fundus downwards.
what is the omental bursa?
the peritoneal space posterior to the stomach that goes on to be the lesser peritoneal sac
how is the omental bursa formed?
by rapid growth of dorsal mesentery and stomach rotation around the longitudinal axis
what connects the greater and lesser omentum sacs?
epoploic foramen of Winslow
how is the greater omentum formed?
the doral mesentery continues to develop from the stomach as a double layered sac over the small intestine and transverse colon. These layers fuse to extend from the greater curvature of the stomach
what is the duodenum a structure of?
the foregut AND midgut
describe how the duodenum is formed.
the stomach rotates causing the duodenum to move from the midline to the right-side of the abdominal cavity. Where the dorsal mesentery fuses with peritoneum covering the posterior abdominal wall causing the duodenum (parts 2+3) and the pancreas to be retroperitoneal
describe how the midgut is developed (up until it has herniated).
week 5: mid gut rapidly expands forming the primary intestinal loop.
the cranial limb and caudal limb then rotate around the axis of the vitelline duct by 90 degrees clockwise.
Week 6: rapid growth of liver causes herniation of the midgut and the cranial limb continues to lengthen - resulting in intesinal loops moving through umbilical cord to lie outside the embryo.. rotation of 180 degrees occurs here (also clockwise)
describe what happens to the midgut during week 10.
intestines retract back into abdomen with 180 degree clockwise turn.
The jejunum and cecal buds then form (in that order). Cecal bud then descends from right lobe of liver to right iliac fossa (forming ascending colon)
describe how fixation of the intestines occurs.
dorsal mesentery of the gut connects to the posterior abdominal wall (connected around the axis of the superior mesenteric artery). The ascending and descending colon mesentery fuse with peritoneum to place them in retroperitoneal space.
what is omphalocele?
failure of the intestinal loop to return into the abdomen. Presenting as a shiny sac at the base of the umbilical cord (high mortality)
what is gastroschisis?
protrusion of abdominal content through wall lateral to the umbilical cord, due to abnormal closure of the coonnecting stalk
describe the development of the hindgut.
the cloaca (terminal end of the hingut) is an endodermal-lined pouch which is in contact with surface ectoderm of the proctodeum to form the cloacal membrane. The urorectal septum partitions the cloaca into upper rectum/anal canal and urogenital sinus. Urorectal septum fuses with the cloacal membrane at the future sit of the perineal body
how is the liver and biliary system formed?
by a ventral outgrowth of the foregut at the end of week 3 into the ventral mesentery resulting in the hepatic diverticulum/liver bud.
what are the cranial and caudal parts of the hepatic diverticulum developed into?
cranial = liver caudal = bile duct
how are the gallbladder and cystic duct formed?
by an outgrowth from the bile duct
what do vitelline veins do?
carry poorly oxygenated, nutrient rich blood to the developing embryo
describe how the pancreas is formed.
by a ventral pancreatic bud forming off the bile duct from the gallbladder AND a dorsal bud forming off the gut tube (inferior to the stomach).
During rotation of the duodenum the ventral bud is moved to the LHS (round the back of the gut tube) and joins the bottom of the dorsal bud.
NOTE: the bile duct moves with this
what could happen as an abnormality of pancreas development?
it can encircle the duodenum on both sides due to there being a bilobed ventral pancreatic bud.
This can lead to constriction of the duodenum
when is the spleen developed?
in week 5
where is the spleen derived from?
mesoderm NOT gut tube (this is endoderm)
when does the spleen develop into a lymphatic organ?
during weeks 15-18
which organs are involved in jaundice?
Liver, spleen, gallbladder, pancreas and small intestines
what is jaundice?
Yellowing of the skin and whites of the eyes caused by build up of bilirubin.
what is bilirubin?
a normal by-product of the break down of red blood cells (spleen) which is used to form bile (liver)
Where does the breakdown of red blood cells mainly occur?
in the spleen
what does the gallbladder do?
stores and concentrates bile
where is bile produced?
in the liver
why is bile needed?
to help absorption of fats from the small intestine
what and where does the pancreas excrete? And why?
digestive enzymes which are released into the 2nd part of the duodenum. These are necessary for the digestion of food
where is the portal triad located?
a the free edge of the lesser omentum
what does the portal triad consist of and what does each part do?
hepatic artery (supplies with blood) hepatic portal vein (drainage of GI tract to liver) common bile duct (part of the biliary tree, linking the liver to the duodenum)
what does the hepatic portal vein do?
drains nutrient rich blood from the GI tract into the liver for cleaning before it is returned to systemic circulation
what is the celiac trunk?
a retroperitoneal artery that is the first of three midline branches off the abdominal aorta.
where does the celiac trunk supply?
the midgut
where does the celiac trunk arise?
T12 vertebral level
what does the cephalic trunk split into?
splenic, hepatic and left gastric arteries
what does the hepatic artery branch to give rise to?
gastroduodenal and superior pancreatico-duodenal
what is the function of the spleen?
to break down red blood cells to produce bilirubin, plays an immunological role as well, has a blood reserve (is like a big lymph node)
where is the spleen located?
intraperitineal and in the left hypochondrium (posterior to the stomach)
which ribs protect the spleen?
ribs 9-11
what is unique about the splenic artery?
it has a tortuous course (winding and twisting)
where does the splenic artery run?
from the cephalic trunk along the superior border of the pancreas
which arteries supply the stomach and where are they found?
Right and left gastric arteries run along the lesser curvature and anastomose together.
Right and left gastro-omental arteries which run along the greater curvature and anastomose together
what is special about the liver?
it has a dual blood supply
what are the edges of the large intestine called?
left = splenic flexture right = hepatic flexure
what does the liver do?
converts bilirubin to bile
which ribs protect the liver?
7-11
how can the liver be divided up?
4 anatomical segments
OR 8 functional segments
what are the names of the 4 anatomical segments of the liver?
right lobe
left lobe
caudate lobe
quadrate lobe
what does the falciform ligament do?
attach the liver to the anterior abdominal wall
what is special about the 8 functional segments of the liver?
they each have their own blood supply (via hepatic artery and hepatic portal vein), venous drainage and bile drainage
which anatomical segment of the liver has its own drainage into the IVC?
caudate lobe
where do the 3 main hepatic veins drain into?
IVC
The IVC and hepatic veins lack valves. True of false?
True
what effect can a rise in central venous pressure have on the liver and why?
hepatomegaly due to it being engorged in blood due to there being no valves in the hepatic veins and IVC
what does each liver lobule have?
a central vein and an interlobular portal triad at each corner
how is bile formed by hepatocytes?
nutrient rich blood flow in through a branch of the hepatic portal vein and passes down a sinusoid, where bilirubin leaks out into the hepatocytes which convert it into bile which then drains into the biliary duct
what are the two recesses around the liver called (they are within the greater sac)?
hepatorenal recess/Morison’s pouch
sub-phrenic recess
what can peritonitis result in?
a collection of pus in the hepatorenal and sub-phrenic recesses leading to abscess formation
what does the hepatic portal vein do?
drain blood from the foregut, midgut and hindgut to the liver for first pass metabolism
which vein drains the foregut to the hepatic portal vein?
the splenic vein
which vein drains the hindgut to the splenic vein?
inferior mesenteric vein
which vein drains the midgut to the hepatic portal vein?
the superior mesenteric vein
which ligaments attach the liver to the diaphragm?
coronary ligaments
what is the ligamentum teres/round ligament?
a remnant of the embryological umbilical vein
where is the gallbladder located?
on the posterior aspect of the liver anterior to the duodenum
what are the parts of the gallbladder?
body and neck which narrows to form the cystic duct
where does bile flow out of the gallbladder?
via the cystic duct
what is the blood supply to the gallbladder?
the cystic artery (a branch off the right hepatic artery in 75% of people)
which part of the gut is the gallbladder part of?
the foregut
which visceral afferents from the gallbladder enter the spinal cord?
T6 and 9
what would inflammation of the gallbladder or cystic duct due to a gallstone lead to (pain)?
early pain in the epigastric region.
can also present in the hypochondrium with or without referral to the right shoulder (due to irritation of the diaphragm)
