Anatomy Flashcards
what causes jaundice?
increase in blood levels of bilirubin caused by an obstruction of the biliary tree
what is bilirubin?
a by-product of the breakdown of red blood cells
where does the breakdown of red blood cells occurs?
the spleen
what is bilirubin used for?
to form bile in the liver
what is the biliary tree?
a set of tubes connecting the liver to the 2nd part of the duodenum that bile travels through
what ducts make up the biliary tree?
- right and left hepatic duct
- to common hepatic duct
- plus cystic duct
- to bile duct
anatomically where is the bile duct?
descending posteriorly to the 1st superior part of the duodenum
travels in a groove to the posterior aspect of the pancreas
it then joins with the ampulla of vater
both then drain into the second part of the duodenum
what is endoscopic retrograde cholangiopancreatography (ERCP)?
investigation used to study the biliary tree and pancreas
what can cause an obstruction of the biliary? tree?
gallstones, carcinoma at head of the pancreas
anatomically, where is the pancreas?
retroperitoneal organ that lies transversely across the posterior abdomen, the duodenum surrounds the head
what are the exocrine functions of the pancreas?
acinar cells (pancreatic digestive enzymes into main pancreatic duct
what are the endocrine functions of the pancreas?
islets of langerhans (insulin and glucagon into bloodstream)
where do the sympathetic nerves of the pancreas come from?
abdominopelvic splanchnic nerves
where do the parasympathetic nerves of the pancreas come from?
vagus nerves
how do nerves reach the pancreas?
pass through the diaphragm, then follow arteries from the celiac and superior mesenteric plexus to reach the pancreas
what is the role of parasympathetic nerves in the pancreas?
secretomotor
how is pancreatic secretion controlled?
parasympathetic nerves but MAINLY by hormones formed in the duodenum and intestinal mucosa as a response to acid contents from the stomach
what arteries supply the pancreas?
- pancreatic branches from the splenic artery
- gastroduodenal artery (superior pancreaticoduodenal)
- superior mesenteric artery (inferior pancreaticoduodenal)
what commonly causes pancreatic pain?
pancreatitis
what causes pancreatitis?
blockage of the ampulla by a gallstone so bile os diverted into the pancreas
where is pancreatic pain located?
epigastric region and/or umbilical region
can radiate to back
what does the small intestine consist of?
- duodenum
- jejunum
- ileum
true or false: the 1st and 2nd part of the duodenum are foregut organs?
true
name the 4 parts of the duodenum
superior
descending
horizontal
ascending
where and what is the pylorc sphincter?
sphincter at beginning of duodenum that controls the flow of chyme from stomach to duodenum
what does the duodenum do?
secretes a number of peptide hormones into the blood ie gastrin and CCK
where does duodenal pain present?
epigastric region
what arteries supply the duodenum?
gastroduodenal artery and superior mesenteric artery
where does the jejunum begin?
duodenaljejunal flexure at around L2 vertebral level
where does the ileum end?
ileocaecal junction
does the mucosa differ in the jejunum and the ileum?
yes
what is the mucosa of the jejunum like?
highly folded (plicae circularis)
what is the arterial blood supply of jejunum and ileum?
superior mesenteric artery via jejunal and ileal arteries
venous drainage of jejunum and ileum
jejunal and ileal veins to superior mesenteric vein to hepatic portal vein
what is bile’s role in the absorption of fats?
helps from GI tract lumen into the intestinal cells
what happens to fats in intestinal cells?
absorbed into specialised lymphatic vessels of the small intestine called lacteals
where do fats go from lacteals?
travel via lymphatic system and drain at left venous angle to venous system
where do you find lymph vessels?
normally alongside arteries
what lymph node drains the foregut organs?
celiac
what lymph node drains the midgut organs?
superior mesenteric
what lymph node drains the hindgut organs?
inferior mesenteric
what lymph node drains the kidneys, posterior abdo wall, pelvis and lower limbs?
lumbar
where do superficial lymph vessels drain?
into deep lymph vessels
where are the venous angles?
junction between subclavian and internal jugular veins
how many paracolic gutters are there?
2 - left and right
where are the parcolic gutters?
between lateral edge of ascending and descending colon, and abdominal wall
where does the caecum and appendix lie?
both lie in the right iliac fossa
where is the appendiceal orifice?
on posteromedial wall of caceum
- corresponds to McBurney’s point on the anterior abdominal wall
- 1/3 of the way between the right ASIS to umbilicus
where does the sigmoid colon lie?
in left iliac fossa
characteristics of sigmoid colon?
has a long mesentery (sigmoid mesocolon) to give it movement
what risks are there with the mobility of sigmoid colon?
- at risk of twisting around itself (sigmoid volvulus)
- results in bowel obstruction
anatomically where is the abdominal aorta?
- midline, retroperitoneal
- lies anterior to vertebral bodies and to left of IVC
what are the midline branches of the abdominal aorta?
3 midline branches
- celiac trunk (foregut organs)
- superior mesenteric artery (hindgut organs)
- inferior mesenteric trunk (hindgut organs)
what do the lateral branches of the abdominal aorta supply?
- kidneys/adrenal glands
- gonads
- posterolateral
at what level does the abdominal aorta bifuricate?
L4
what does the abdominal aorta bifuricate to??
external and internal left and right iliac arteries
what side does the superior mesenteric artery supply?
right
what are the branches of the superior mesenteric artery?
- (inferior pancreaticoduodenal)
- middle colic
- right colic
- ileum (ileocolic)
- (appendicular)
what side does the inferior mesenteric artery supply?
left
what are branches of the inferior mesenteric artery?
- left colic
- sigmoid colic
superior rectal
what does the inferior mesenteric supply??
hindgut organs
where is an arterial anastomoses in the abdominal aorta?
between the branches of the SMA and the IMA
what is the arterial anastonmose beween SMA and IMA called?
marginal artery of Drummond
what is a benefit of an arterial anastomose?
could prevent intestinal ischaemia by providing an alternative route by which blood can travel
what could cause haematemesis?
- peptic ulcer in wall of stomach or duodenum
- erodes through the mucosa
- stomach or duodenum fills with blood
- bleeding from oesophageal varices
- abdominal dilatd veins
- thin walled, therefore have potential to rupture
- formatio often due to pathology affecting the portal venous system
name the 2 venous systems
- hepatic venous system
- systemic venous system
what is the hepatic portal vein in the venous system for?
drains blood from the foregut, midgut and hindgut structures to the liver fr the first pass metabolism
what is the inferior vena cava for in the venous system?
drains cleaned blood from the hepatic veins into right atrium
what is the role of the splenic vein in the venous system?
drains blood from foregut structures to hepatic portal vein
what is the role of the superior mesenteric vein?
drains blood from midgut structures to hepatic portal vein
what is the role of the inferior mesenteric vein?
drains blood from hindgut structures to splenic vein
characteristics of anastamoses between the systemic and portal venous systems?
- blood can flow both ways
- no valves
what is portal hypertension?
clinical term given to increased blood pressure within portal veins
why does portal hypertension occur?
liver pathology eg cirrhosis
what happens in portal hypertension?
blood will be diverted through the collateral veins back to the systemic venous system
what are the complications of portal hypertension?
the collateral veins have a much larger volume of blood through them than they are used to so they dilate, becoming varicose
what does the control of the excretion of faeces require?
- a holding area (the rectum) to store faeces until appropriate
- normal visceral afferent nerve fibres to sense “fullness” of the rectum
- functioning muscle sphincters to contract and rela
- normal cerebral function
what can faecal continence be affected by?
neurological pathology, medications, neural age
where is the rectum located?
within the pelvic cavity
at what level does the sigmoid colon become rectum?
anterior to S3
the rectosigmoid junction
where does the rectum become the anal canal?
anterior to the tip of the occyx just prior to passing through the levator ani muscle
where are the anal canal and anus loacted?
in the perineum
where is the rectal ampulla located?
immediately superior to the levator ani muscle
what muscles make up the levator ani? (lateral to medial)
- iliococcygeus
- pubococcygeus
- puborectalis
what do the levator ani muscle do?
- provides continual support for the pelvic organs
muscle must relax to allow defecation and urination to occur
what nerves supply the levator ani and at what level?
“nerve to levator ani” ( a branch of the sacral plexus) and pudenal (S2, 3 and 4)
what is the function of the puborectalis muscle?
contraction of this muscle decreases the anorectal angle, acting like a sphincter.
skeletal muscle so under control, voluntary contraction will help to maintain continence
how many anal sphincters are there and what are they called?
2
- internal and external
what type of muscle is the internal anal sphincter?
smooth muscle
what type of muscle is the external anal sphincter?
skeletal
what area of anal canal is the internal anal sphincter found?
superior two thirds of anal canal
how is contraction of internal anal sphincter stimulated?
sympathetic nerves
how is contraction of internal anal sphincter inhibited?
parasympathetic nerves
is internal anal sphincter always contracted?
yes
where is the external anal sphincter found in the anal canal?
inferior two thirds of the anal canal (superior part of the sphincter is continuous with the puborectalis muscle)is
how is contraction of external anal sphincter stimulated?
by the pudendal nerve
is the external anal sphincter under voluntary contraction?
yes
what causes voluntary contraction of external anal sphincter?
along with puborectalis in response to rectal ampulla distension and internal sphincter relaxation
what level are the sympathetic fibres that contract the internal anal sphincter from?
T12-L2
where do the sympathetic fibres supplying the rectum and anal canal travek?
from T12-L2 to inferior mesenteric ganglia then to periarterial plexus around branches of IMA
where do the visceral afferents go to and what do they sense?
S2-S4 with parasympathetics
sense stretch, ischaemia etc
where do the parasympathetic fibres supplying rectum and anal canal run from?
from S2-S4 via pelvic splanchnic nerves, synapse in walls of rectum
what do the parasympathetic nerves do in the rectum/anal canal?
- inhibit internal anal sphincter
- stimulate peristalsis
what do the sympathetic nerves do in the rectum/anal canal?
- contraction of anal sphincter
- inhibit persitalsis
what does somatic motor innervation do?
from pudendal nerve (s2-S4) and nerve to levator ani (S3-S4) contract external anal sphincter and puborectalis
what levels is the pudendal nerve found?
S2, S3 and S4
where does the pudendal nerve exit the pelvis?
via the greater sciatic foramen
what does the pudendal nerve supply?
external anal sphincter
where doe the pudendal nerve enter the perineum?
via lesser sciatic foramen
what is the pectinate line?
marks the junction between the part of the embryo which formed the GI tract (endoderm) and the part tha formed the skin (ectoderm)
what supply is superior to pectinate line?
visceral
what supply is inferior to line?
parietal
what is the nerve supply above the pectinate line?
autonomic
what is the arterial supply above the pectinate line?
from inferior mesenteric artery
what is the venous drainage above the pectinate line?
to portal venous system (IMV)
what is the lymphatic drainage above the pectinate line?
inferior mesenteric nodes (internal iliac nodes)
what is the nerve supply below the pectinate line?
somatic and pudendal
what is the arterial supply below the pectinate line?
from internal iliac artery
what is the venous drainage below the pectinate line?
to systemic venous system (internal iliac)
what is the lymphatic drainage below the pectinate line?
superficial inguinal nodes
name the main groups of lymph nodes draining the pelvic organs
- internal iliac (draining inferior pelvic)
- external iliac (draining lower limb and more superior pelvic structures)
- common iliac (draining from external and internal iliac nodes)
- lumbar nodes (from common iliac)
what artery supplies the hindgut organs?
inferior mesenteric artery
where does the hindgut end?
at the proximal half of the anal canal (the pectinate line)
what does the internal iliac artery supply?
remainder of GI tract after pectinate line
what does the inferior mesenteric vein do?
drains the hindgut organs above the pecrinat line via the portal venous system
what does the internal iliac vein do?
drains below the pectinate line via the systemic venous system
how do rectal varices form?
in relation to portal hypertension, dilation of collateral veins between portal and systemic venous systems
how are haemorrhoids formed?
as prolapses of the rectal venous plexus
not related to portal hypertension
its raised pressure ie chronic constipation, pregnancy
what are ischioanal fossa?
lie on each side of anal canal and are filled with fat and loose connective tissue
- communicate with each other posteriorly
what is an infection within the ischioanal fossa called?
ischioanal abscess
