Anatomy Workbook - gastro Flashcards
Name the muscles of the abdominal wall
external oblique
internal oblique
transversus abdominis
rectus abdominis
Rectus abdominis action
flexion of trunk
Obliques actions
flexion + lateral flexion of trunk
Other than movement, when else can the abdominal muscles be used?
forced expiration
to raise intra-abdominal pressure
What is the purpose of the tendinous intersections along the rectus abdominis muscle?
dividing the long muscle into smaller sections gives the muscle more power
What is the somatic innervation to the abdominal muscles?
intercostal nerves T7-T12
Intraperitoneal structures
distal oesophagus
stomach
spleen
liver
gallbladder
D1
D4
jejunum
ileum
caecum
appendix
transverse colon
proximal 1/3 rectum
Retroperitoneal structures
D2
D3
pancreas
ascending colon
descending colon
sigmoid colon
kidneys
ureters
adrenal glands
bladder
pelvic organs
IVC
aorta
Explain why the bare area of the liver can be involved in spread of infection from the abdominal to thoracic cavity
area of liver that IVC passes close to has no peritoneal covering
IVC passes through the diaphragm into thoracic cavity, therefore no serosal barrier between abdominal and thoracic cavities at this point allowing infection spread
Why do adhesions occur?
when inflamed, serosal membranes will fuse together as part of the healing process
greater omentum would particularly migrate to area of inflammation and cause peritoneal adhesions to form
When do incisional hernias occur?
occur when AAW has been compromised by surgery and has not healed effectively
can occur when linea alba used for emergency access as it has poor blood supply and therefore healing is poor
When do umbilical hernias occur?
at umbilicus where there is a natural opening in AAW for umbilical vessels to pass to placenta as a foetus
When do femoral hernias occur?
when fatty tissue or a loop of bowel pass through the natural space below the inguinal ligament
When do inguinal hernias occur?
at superficial and deep inguinal rings where there are structural defects
Which structures compose the posterior wall of the inguinal canal?
medial = internal oblique + transversalis fascia
lateral = transversalis fascia
Which structures comprise the roof of the inguinal canal?
internal oblique
transversus abdominis
Which structure comprises the floor of the inguinal canal?
inguinal ligament
The conjoint tendon reinforces the inguinal canal at the location of the superficial inguinal ring. Why do we need reinforcement here?
superficial ring = weakness in abdo wall, increase in intra-abdo pressure will push abdo structures against abdo wall and risk of herniation in weak area
tendon reinforces ring posteriorly
What reinforces the inguinal canal at the lateral aspect at the location of the deep inguinal ring?
the other anterior abdominal wall muscles
Where do direct hernias pass relative to the inguinal canal?
does not pass through the canal, only through superior inguinal ring
Where do indirect hernias pass relative to the inguinal canal?
passes into deep inguinal ring, along the canal and out of the superior inguinal ring
Where do femoral hernias pass relative to the inguinal canal?
passes inferior to inguinal ligament and therefore the inguinal canal
Direct hernias are controlled by applying pressure at which anatomical landmark?
superficial inguinal ring
Indirect hernias are controlled by applying pressure at which anatomical landmark?
deep inguinal ring
Femoral hernias are controlled by applying pressure at which anatomical landmark?
will still herniate with pressure to either inguinal ring
Surgically, which position do direct hernias pass through AAW relative to inferior epigastric vessels?
medial
Surgically, which position do indirect hernias pass through AAW relative to inferior epigastric vessels?
lateral
Surgically, which position do femoral hernias pass through AAW relative to inferior epigastric vessels?
not related
passes beneath inguinal ligament through femoral canal with femoral vessels
What is the surface landmark for the deep inguinal ring?
midpoint of inguinal ligament (halfway between ASIS + pubic tubercle)
What is the surface landmark for the superficial inguinal ring?
lateral and superior to pubic tubercle
Where does a direct inguinal hernia pass?
directly through the anterior abdominal wall at the level of the superficial ring
Where does an indirect hernia pass?
takes an indirect route through the anterior abdominal wall by passing into the deep inguinal ring, through the canal and out of the superior inguinal ring
How does a direct inguinal hernia most often occur?
trauma - rupture of conjoint tendon formed by fibres of internal oblique and external oblique which reinforces superficial inguinal ring
What is the cause of an indirect inguinal hernia?
congenital defect
failure of processus vaginalis to close, leaving deep inguinal ring open
[indirect hernias are most common and strangulate]
Why is a strangulated hernia a medical emergency?
usually associated with direct inguinal hernias as area of AAW that is compromised is due to damage of conjoint tendon
damaged muscles contract due to inflammation which squeezes herniated tissue compromising blood flow –> bowel ischaemia
What factors can contribute to a direct inguinal hernia?
sudden strain due to lifting
straining when attempting to defecate due to constipation
What is the name of the area of the colon that the anastomosis of the SMA and IMA occurs?
watershed area
If a resection of the distal end of the transverse colon had to be performed, what might the surgeon take into consideration?
crossover point of SMA and IMA varies between individuals
distal end of transverse colon could be supplied by midcolic or left colic artery
may need larger margins so no bowel left was left colic –> ischaemia
How can the architecture of the arterial supply of the colon influence metastatic cancer spread?
lymphatics of gut tube follow arteries to return to para-aortic nodes
therefore lymphatic vessels extensively linked
Pelvic diaphragm functions
physical barrier between pelvis and perineum, stops pelvic and abdominal contents prolapsing during periods of increased intra-abdominal pressure (eg. sneezing, coughing, childbirth)
aids urinary and faecal continence
How does the pelvic diaphragm aid continence?
levator ani muscles run in inferior, medial and posterior direction and come together to form midline raphe
contract = fibres move superior + anterior muscle forms sling around structures + pulls them when contracts
forms kink –> harder for urine, faeces or gas to pass through
What can happen if anococcygeal body is damaged?
faecal incontinence
Why can infection spread from one side of the ischioanal fossae to the other?
they connect anteriorly between urogenital and pelvic diaphragms and posteriorly behind external anal sphincters
What is the main risk associated with surgery to remove a fistula between rectum and anal skin?
faecal incontinence
inferior rectal nerve (branch of pudendal nerve) passess through ischioanal fossae from below the sacrotuberous ligament and anal sphincters
Difference between pudendal nerve damage and cauda equina syndrome
compromise of pudendal nerve = loss of sensation of perineum and motor control to external anal sphincters
cauda equina syndrome = affect pudendal nerve and nerve roots L3-S5 –> saddle anaesthesia, lower back pain, leg paraesthesia, loss of urinary and faecal incontinence
Why can you get mild incontinence following childbirth?
pelvic diaphragm has become stretched and weakened through vaginal childbirth
Why can abdominal pain cause referred pain to the shoulder?
irritation to peritoneum covering diaphragm will trigger phrenic nerve (nerve roots C3-C5)
shoulder dermatome = C5
brain confuses signals + presents pain in shoulder
What feature could partially contain the contents of the stomach following a perforation making peritonitis less likely to occur?
lesser sac
Why do the splenic vein, IMV and SMV not drain directly into the IVC?
venous blood of gut tube contains chemicals and nutrients absorbed during digestion that need to be processed by liver
2 main functions of the spleen
filtration of blood - removal + cleavage of spent RBCs
white blood cell storage (immune response)
Why does the lymphatic drainage of the gut follow the arteries rather than the veins?
these veins return blood to the liver, not heart, therefore lymphatics follow arteries to aorta and drain to para-aortic lymph nodes and drains into cisterna chyli
What is the function of the hepatic veins?
drain deoxygenated, filtered blood from the liver
Why is bile green?
contains brightly coloured bile salts (eg. bilirubin and biliverdin)
What are the 2 main functions of bile?
neutralise stomach acid
emulsify fats in duodenum
Why is some bile stored in the gallbladder?
allows bile to become more concentrated and ensures there is a supply ready when food passes from stomach to duodenum
How does cholecystectomy affect a patient’s lifestyle?
without a store of concentrated bile, a large amount of acidic chyme entering duodenum can’t be neutralised effectively, potentially resulting in peptic ulcers.
equally, they may not be able to digest large amounts of fat, so undigested fat will travel to intestines, therefore patient may need to eat smaller, less fatty meals
Why do people not feel a space-occupying lesion in the pancreas?
innervation of abdominal viscera is via autonomic nervous system which has poor sensory innervation
How can pancreatic cancer cause jaundice?
splenic vein brings unconjugated bilirubin from breakdown of RBCs to liver to be conjugated
conjugated bilirubin is excreted in bile into 2nd part of duodenum via common bile duct
pancreatic tumour in head of pancreas has blocked common bile duct, obstructing excretion of bile from liver, therefore increasing conjugated bilirubin in blood
Where are the 3 main sites of porto-systemic anastomoses in the abdominal cavity
distal oesophagus
umbilicus
proximal rectum
If portosystemic anastomoses are used as a way to return blood to the IVC, small veins can be put under more stress than they can cope with, what pathologies would be seen under these conditions?
oesophageal/rectal varices + bleeding
caput medusae
What is the venous drainage of the liver?
hepatic veins
