Session 1 - the anterior abdominal wall and hernias Flashcards
How is the abdominal cavity bound posteriorly?
bounded by the lumbar vertebrae and the muscles lying lateral to them (- psoas (and iliacus) and quadratus lumborum)
Which muscles are the most important expiratory muscles in deep, rapid or forced respiration?
the sheet muscles
What are the serratus anterior and the lattisimus dorsi?
Other posterior muscles (although they are more important in thorax anatomy)
Serratus anterior –on the lateral wall of the thorax, with anterior origin and insertion along the medial border of the scapula; acts to pull the scapula forward and around the thorax
Lattisimus dorsi – large triangular muscle of the back, with origin in the thoracolumbar fascia, and insertion into the armpit
What is the anterolateral abdominal wall composed of?
skin, fascia and four pairs of muscles; the external oblique, internal oblique, transversus abdominus and rectus abdominus
Where is the pubic symphysis?
(a secondary cartilaginous joint located) between the left and right pubic bones near the midline of the body. It is located above any external genitalia and in front of the bladder
Where is the pubic tubercle?
just next to the pubic symphysis
a prominent forward-projecting tubercle on the upper border of the medial portion of the superior ramus of the pubis
What does ASIS stand for and where is it?
anterior superior iliac spine
found at the the anterior extremity of the iliac crest of the pelvis
NOTE: it provides attachment for the inguinal ligament, and the sartorius muscle
What is the iliac crest?
the ilium is the largest bone of the pelvis
The crest of the ilium is the superior border of the wing of ilium and the superolateral margin of the greater pelvis.
What s the iliac fossa?
a large, smooth, concave surface on the internal surface of the ilium
What separates the abdominal and the pelvic cavities?
they are continuous, but the pelvic inlet (brim) separates the two
What separates the thoracic and abdominal cavities?
the diaphragm
What are the 4 lines that have to be drawn to split the abdomen into 9 regions?
What vertebral levels are the 2 horizontal lines/planes at?
- 2 mid-clavicular lines (right and left)
- subcostal plane (at L2)
- inter tubercular plane (at L5)
What are the 9 regions of the abdomen?
from right to left
- right hypochondrium/hypochondriac region
- epigastric region
- left hypochondrium/hypochondriac region
- right flank/lumbar region
- umbilical region
- left flank/lumbar region
- right groin/iliac region
- hypogastric/supra pubic region
- left groin/iliac region
What 2 lines are drawn to split the abdomen into 4 quadrants?
saggital plane
trans-umbilical plane
What are the muscles of the anterior abdominal wall?
paired vertical rectus abdominis muscles with rectus sheath
What are the muscles of the lateral abdominal wall?
3 flat sheet muscles:
- external oblique
- internal oblique
- transversus abdominis
What are the muscles of the posterior abdominal wall?
- post vertebral muscles - erector spine group
- psoas (attached to the lower limb)
- quadratus lumborum
- iliacus muscles
How do the 3 flank sheet muscles join at the front anteriorly?
NOTE: they are separate in the flanks
they continue anteriorly as aponeurotic sheaths and contribute to the rectus sheath
What is the function of the 3 flank sheet muscles?
- compress the abdomen and increase intra-abdominal pressure to aid expiration, and evacuation of urine, faeces, parturition (childbirth), heavy lifting
- supports viscera - guards the intestines
- flex and rotate the trunk
What is the external oblique attached to?
- external surface of lower 8th ribs
- it has a free posterior border
- it fans out to attach to xiphoid process, linea alba, pubic crest and the anterior half of the iliac crest
What is the direction of the muscle fibres of the external oblique muscles?
infero-medially
anterior and inferior (downwards and forwards)
What is the inguinal ligament?
a band running from the pubic tubercle to the anterior superior iliac spine
What happens to the external oblique muscles towards the midline?
- the aponeurosis fuses medially with the the rectus sheath
- the lower aponeurotic edge is rolled inwards and forms the inguinal ligament (ASIS to pubic tubercle)
Laterally, what does the internal oblique attach to?
- thoracolumbar fascia
- iliac crest
- inguinal ligament (lateral half)
Medially, what does the internal oblique attach to?
- lower 3 ribs and costal cartilages
- xiphoid process
- rectus sheath
- conjoint tendon
What is the direction of the muscle fibres of the internal oblique muscles?
supero-medially
posterior and inferior (downwards and backwards)
Laterally, what does the tranversus abdominis attach to?
- lower 6 costal cartilages
- thoracolumbar fascia
- iliac crest
- inguinal ligament
Medially, what does the tranversus abdominis attach to?
- xiphoid process
- linea alba (rectus sheath)
- symphysis pubis
- conjoint tendon
What is the direction of the muscle fibres of the tranversus abdominis?
horizontal (like a belt)
Where does the neurovascular plane lie?
between the internal oblique and transversus abdominis muscle layers
What is the rectus abdominis?
long strap of muscle of the anterior abdominal wall, enclosed in rectus sheath
2 heads
NOTE: the muscle is divided into segments by tendinous intersections (3 on each side) which are attached to the anterior wall of the rectus sheath
Where does the rectus abdominis attach superiorly?
- 5-7 costal cartilages
- xiphoid process
Where does the rectus abdominis attach inferiorly?
- symphis pubis
- pubic crest
What forms the rectus sheath?
the aponeuroses of the 3 flank muscles
What is the structure of the rectus sheet around the rectus abdominis above the umbilicus?
- the internal oblique aponeurosis is split and encloses the rectus abdominis
(the aponeurosis of the external oblique is in front and that of the transversus is behind the rectus muscle)
What is the structure of the rectus sheet around the rectus abdominis below the umbilicus?
all 3 aponeurotic layers are anterior to the rectus muscle
What is the linea alba?
where the rectus sheath meets at the midline
The anterior wall of the sheath is complete from the _____ to the _____
from the xiphoid process and costal cartilages
to the pubic symphysis and crest
The posterior wall of the sheath is incomplete. Where does it stop?
at the arcuate line (just below the umbilicus)
What is below the arcuate line?
the rectus abdominis muscle
it is in contact with the transversalis fascia
Which muscle is the most powerful floor of the spine?
rectus abdominis (external and internal oblique play an important role in this action)
What are the posterior abdominal wall muscles?
- psoas major - a flexor of the hip and trunk
- quadratus lumborum - stabilises the 12th rib and a lateral flexor of the trunk
What are the attachments of the psoas major?
bodies and discs of all 5 lumbar vertebrae and lesser trochanter of femur)
What are the attachments of the quadratus lumborum?
lower border of the 12th rib and transverse process of the 5th lumbar vertebra and adjacent iliac crest
What is the blood supply of the rectus muscle?
1- superior epigastric artery
2- inferior epigastric artery
How is blood supplied to the flank muscles?
(segmentally supplied) 1- intercostal arteries 7-11 2- subcostal artery 3- lumbar arteries 4- deep circumflex iliac arteries
What is the venous drainage of the abdominal wall?
Depp veins bearing the same names (as the arteries) accompany the arteries
What is the nerve supply of the abdominal wall?
motor nerves from T7-T11 and L1
segmentally supplied
What is the nervous supply of the external oblique muscles?
T7-T11
What is the nervous supply of the internal oblique and transversus muscles?
T7-T12 and L1
What is the nervous supply of the rectus?
T7-T12
What are the dermatomes of the epigastrium, umbilicus and the inguinal ligament?
epigastrium - T7
umbilicus - T10
inguinal ligament - L1
What is noticeable about lymph nodes and the abdominal wall?
there are NO lymph nodes in the abdominal wall
Why do hernias commonly occur in the inguinal region?
because of the inherent weakness of the abdominal wall
What are the 2 areas of inherent weakness in the groin?
1 - inguinal canal
2 - femoral canal
What are the common types of hernias in the inguinal region?
1- inguinal hernia - indirect and direct
2 - femoral hernia
What are the common types of hernias in the inguinal region?
1 - inguinal hernia - indirect and direct
2 - femoral hernia
Where is the acquired effect that causes a direct inguinal hernia?
posterior wall of the inguinal canal
What vertebral level is the xiphoid process?
T10
What is the difference between a tubercle and a symphysis?
Tubercle - a small rounded protrusion
Symphysis - where two bones are joined
The tubercle is just next to the symphysis.
At what vertebral level is the transpyloric plane?
L1
Describe the level of the subcostal plane
lower edge of the 10th costal cartilage
level of L3
Describe the level of the supracristal plane
highest point on the iliac crest
Describe the level of the inter-tubercular plane
between the tubercles of the iliac crests
level of L5
Where is pain of the gut referred to?
foregut - epigastric region
midgut - umbilical region
handgun - pubic region
What is meant by the foregut?
- Starts at the point the oesophagus pierces the diaphragm
- Ends just after the major duodenal papilla (second part of the duodenum)
What is meant by the midgut?
- Begins just inferior to the major duodenal papilla
- Ends 2/3s of the way through the transverse colon
What is meant by the hindgut?
- Starts 2/3s of the way through the transverse colon
- Ends mid-way through the anal canal
What are the direct/immediate branches of the abdominal aorta that innervate the foregut, midgut and the hindgut?
foregut - celiac trunk
midgut - superior mesenteric artery
hindgut - inferior mesenteric artery
What are the 3 parts of the abdominal wall?
anterior
lateral
posterior
Give the layers of the anterior abdominal wall
- skin
- superficial fascia - fatty (Camper’s) and membranous (Scarpa’s)
- external oblique muscle
- internal oblique muscle
- tranversus abdominis
- transversalis fascia (NOTE: well developed)
- extraperitoneal fascia
- parietal peritoneum
Below the arcuate line, what is directly behind the rectus abdominis?
The transversalis fascia
What is the linea semilunaris?
A curvilinear tendinous intersection found on either side of the rectus abdominis muscles
What are the contents of the inguinal canal?
- The ilio-inguinal nerve (does not run in spermatic cord!)
- Spermatic cord in men
- Round ligament of the uterus in women
What is a hernial sac made up of?
parietal peritoneum
