Surgical anatomy of the abdomen Flashcards
Concerning the abdominal wall, where do the linea semiluminares lie?
Vertically at the lateral edges of the rectus abdominus muscles
Where does the linea alba lie?
In the vertical midline of the abdomen
Which structure stretches obliquely between the anterior superior iliac spine (ASIS) and pubic tubercle
inguinal ligament
What is the name of the connective tissue that lies horizontally within the rectus abdominus muscles, which can give you a ‘six-pack’?
Tendinous intersections
What type of operation commonly uses a grid-iron incision?
Appendicectomy
“gird-iron” (muscle splitting) is used to remove an appendix
What type of operation is used for a cholecystectomy (remove a gallbladder)?
Kocher incision in right subcostal region
What type of incision is used for a caesarean section?
Pfannenstiel incison - horizontally above the symphis pubis
What is a laparotomy?
When the abdomen is opened through a large vertical midline (through the linea alba) incision, which gives access to the abdominal contents
What type of incision does laparoscopic surgery use?
A series of small incisions (a few cm each) through which instruments are passed
What type of incision is normally used for cholecystectomies and appendicectomies these days?
Laparoscopic surgery is almost always used for cholecystectomies and some appendicectomies- therefore small series of incisions are made
List the anterolateral abdominal muscles in layers from superficial to deep
External oblique
Internal oblique
Transversus abdominis
Which direction do the external oblique muscle fibres run?
Inferior and medial direction
Which direction do the internal oblique muscle fibres run?
Superior and medial direction
Which direction do the transversus abdominis fibres run?
Transverse direction
What are aponeuorses?
Flattened tendons
What is the location of the linea alba?
Vertical in the midline from the xiphoid process to the pubic symphysis
What is the linea alba a surgical site for?
A midline laparotomy incision
Where is the arcuate line (Douglas’ line) found?
Horizontal between the umbilicus and the pubic symphysis. A third of the way down from the umbilicus
What is the arcuate line?
A transition point for the structure of the rectus sheath. Below the arcuate line there is no posterior layer of the sheath and it is in direct contact with the transversalis fascia
Above the arcuate line the aponeusosis of the internal oblique muscles divides and envelopes the rectus muscles
At the costal margins what is anterior and posterior to the rectus abdominis muscles?
Anterior - external oblique (not aponeruoses) form sheath
Posterior - costal cartilage
Where do the aponeuroses of the flat muscles interlace?
Linea alba
What is the effect of the abdominal muscles contracting during activities such as coughing, defecation, lifting, parturition and urination?
Increases intra-abdominal pressure
Why is the rectus abdominus muscle divided down its length into 4 shorter muscle regions?
More mechanically efficient than having one long muscle down the whole length of the abdomen
What is a down-side of human abdominal muscle evolving first as quadrupeds before becoming bipeds?
The anterior abdominal wall is stong to prevent guts falling out when quadripeds but comparatively the inferior abdominal wall is weak and rectal prolapse can occur - especially in the elderly
List the three areas where abdominal muscle can attach from the most exterior to the most interior
Ribs
Pelvis
Transverse processes (vertebrae)
What attachments do the external oblique muscles have?
Travel in an inferior medial direction from their attachments at the ribs to their attachment at the lateral border of the rectus sheath
What attachments do the internal oblique muscles have?
Travel in a superior medial direction from the pelvis to the lateral border of the rectus sheath
What attachments do the transversus abdominis muscles have?
Travel in a transverse direction from the transverse processes of the vertebrae to the lateral border of the rectus sheath
What is the name of the connective tissue layer found underneath the transversus abdominis muscles?
Transversalis fascia
What is underneath the transversalis fascia?
Peritoneum
What is the first structure apparent when the peritoneum of the abdominal cavity is removed?
Greater omentum
What is one of the functions of the greater omentum?
It can move around and wall off infection. Why it is sometimes called the ‘abdominal constable’
In which surgical procedure is the Arcuate line used to the advantage of the surgeons?
During caesarian section a Pfannestiel incision is made just inside the bikini line. Therefore the incision only needs to go through the anterior rectus sheath and part of the rectus abdominus, there is no posterior sheath to go through
Why is divarication of recti, not a hernia?
This is a common condition - especially in woman who have had lots of babies - as the linea alba becomes weak and stretchy, therefore wider than it should be
What can cause rectus sheath haematoma?
Prolonged use of warfarin - therefore can be seen in elderly. Very painful as rectus sheath is a tightly enclosed compartment
What simple test can be used to determine if abdominal pain is being caused by rectus sheath haematoma?
Lifting legs or head (e.g. sit up of leg lift) which uses rectus abdominis muscles. If this exacerbates pain, it makes this diagnosis more likely
Why can bruising be seen a few days after a rectus sheath haematoma?
Blood seeping out of the lateral edges of the rectus sheath
Why is it not possible to sew muscle-muscle?
Sewing muscle-muscle together is like sewing butter, as you try and tighten it up the knots slip through the muscle
What structure in the abdomen provides a strong structure when sewn together?
Aponeurosis-aponeurosis
What inscisions make use of aponeurosis-aponeurosis sutures?
Vertical incisions down the linea alba
Horizontal incisons along the tendinous intersections
Where is the incision made for an open appendisectomy?
Two-thirds of the way from the umbilicus to the anterior superior iliac spine (McBurney’s point)
A gridiron incision is made at McBurney’s point in order to do an appendisectomy. What is a gridiron incision?
Each layer of muscle you cut to seperate fibres rather than cut them e.g. first separate the external oblique, then the internal oblique then the transversus abdominis etc..
What two structures does the vitelline duct join in the embryo?
Midgut to yolk sac
What structure does the sac-like allantois join to?
The cloaca (primitive bladder) - it help dispose of liquid waste and perform gas exchange in the early embryo
What is the role of the yolk sac in the early embryo
Early source of nutrition and haematopoesis
What is another name for the allantois?
urachus
A patent urachus can present at birth or later in life in men. Why can it suddenly present in elderly men?
Elderly men can develop benign prostatic hypertrophy which increases the intrabladder pressure (bladder outflow obstruction) and the urachus opens up and urine appears in the umbilicus
How can you distinguish in a newborn the difference between a patent urachus and a patent vitellinointestinal duct?
Canulate and inject dye then perform an X-ray, see if dye highlight bowel or bladder
What causes an exampholos?
When the midgut fails to return to the abdomen once it has physiologically herniated into the proximal umbilicus. The herniated viscera are therefore covered in peritoneum
What causes gastroschisis?
A defect in embryological folding which causes incomplete closing of the anterior abdominal wall such that there is a weakness to the right of the umbilicus through which viscera NOT covered in peritoneum herniate through
Where is the liver located in relation to surface markings?
The superior right side of the liver goes up almost to the right nipple
Where is the spleen located in relation to surface markings?
Right behind the ribcage on the left
Where does the aorta (retroperitoneal structure) divide into the left and right common iliac arteries, in relation to surface markings?
umbilicus
The kidneys (retroperitoneal structure) are in the loin. Where is the loin located?
Right at the back of the ribcage at the junction of the 12th rib with T12 of the vertebral column
What is meant by ‘referred pain’?
pain perceived at a site distant form the site causing the pain
What is somatic referred pain?
Pain caused by noxious stimulus to the proximal part of a somatic nerve that is perceived in the distal dermatome of the nerve
What dermatome comes round to the level of the umbilicus?
T10
What dermatome comes round to the suprapubic area?
T12 e.g. infection of the (proximal) nerve at T12 on the back can cause right iliac fossa pain (distal nerve)
In chidren right why can right lobe pneumonia cause right iliac fossa pain?
The pneumonia irritates T12 proximal somatic nerves which refer the pain to their distal location in the right iliac fossa
What is visceral referred pain?
In the thorax and abdomen, visceral afferent pain fibres follow sympathetic fibres back to the same spinal cord segments that gave rise to preganaglionic sympathetic fibre (somatic sensory nerves).
Therefore the CNS perceive visceral pain as coming from the somatic portion of the body supplied by the relevant spinal chord segments
Why does an early appendicitus cause pain in the umbilical region?
Visceral pain stimulus from the inflamed appendix travels up the visceral afferent nerve fibres and joins the somatic nerve at the level of T10. Therefore the brain perceives this signal as originating from the somatic afferent sensory nerve from the umbilical region and registers it as umbilical pain
What causes visceral pain?
Ischaemia Abnormally strong muscle contraction Inflammation Stretch (Touch, burning, cutting, crushing, does NOT cause visceral pain)
Where does foregut visceral pain refer to?
Epigastric region
Where does midgut visceral pain refer to?
Periumbilical region
Where does hindgut visceral pain refer to?
Suprapubic region
How does cardiac pain feel?
Crushing, tight, heavy
Where are the classic sites that cardiac pain is referred to?
Central chest
Epigastric region
Neck
Jaws
To the left arm (and less commonly the right arm)
Sometimes pain is only felt in the left ear (not common)
What is the character of oesophageal pain?
Burning especially if caused by oesophageal reflux
Where is oesophageal pain felt?
Retrosternally up to either side of the sternal notch
Where are gastric and duodenal pain felt?
Foregut therefore epigastric
Where is gallbaldder pain felt?
Epigastrium
At the site of the gallbladder
Just below right scapula - typical
Where is hepatic pain felt?
Over the liver
Where is splenic pain felt?
Over the spleen
Where can retroperitoneal (pancrease, aorta) structures cause pain?
Central back
Pancreas (and e.g. a ruptured aortic aneurism) - umbilical area going through to back (mid-lumbar region)
Where is the pain from an acute appendicitus felt in its early and late stages?
Early - perumbilical (visceral pain)
Late - right ilica fossa (somatic pain)
Where is small bowel colic felt?
Midgut - umbilicus pain
It comes in waves, just as one wave finishes the next begins (every 30sec)
Where is large bowel colic felt
hindgut - suprapubic pain
It comes in waves every 2-3-4 minutes (less frequent than small bowel colic)
Where is renal or ureter pain felt?
Loin - right at the back just below the ribcage
Can be referred into the scrotum and can be felt only in the scrotum
What is a characteristic behaviour of patients with renal colic?
Rolling around on the floor - one of the worst pains you can feel
Where is uterine pain felt?
Suprabubically and right back to the lower lubo-sacral level
Where is bladder pain felt?
Suprapubically and DOESN’t go to the back
Where is the pain of diaphragmatic irritation referred to?
Classically over left shoulder because that is where the diaphragm embryonically originated from and takes its nerves supply from before it descended.
It doesn’t cause pain on the right hand side of the shoulder because the right hand side of the diaphragm is protected by the liver
What can be the causes of an irritated diaphragm?
Ruptured spleen
Ectopic pregnancy
Perforated ulcer
If the patients then lie down
What is the cause of the diffuse nature of visceral abdominal pain?
Visceral pain is can be linked to the embryological foregut, midgut and hindgut structures.
Due to the viscera not having dedicated pain fibres and instead using sympathetic afferents,
the pain felt from a viscera is usually felt in the midline and in either the epigastrium
(foregut), around the umbilicus (midgut) or suprapubic region (hindgut).
What is the cause of the localised abdominal pain?
Once the parietal peritoneum is stimulated (which is derived from the somatic mesoderm)
somatic neurones relate pain to dorsal route ganglions in the spinal cord. Pain is then
localised to the dermatome nearest to the pathological process, which is much more specific
than visceral pain.
