W3: Abdominal walls Flashcards
How many layers of the anterior abdominal wall are there? List them
Describe neurovascular plane of abdominal wall
All of the neurovascular structures supplying the abdominal muscles run in the plane between the internal oblique and transversus abdominis muscles, except for the iliohypogastric and ilioinguinal nerves.
Borders of anterior wall
Costal margin
ASIS
Pubic tubercle
What is anterior wall made up of?
The anterior abdominal wall is formed from skin, superficial fascia, muscles and parietal peritoneum.
What can superficial fascia of ant wall be divided into?
fatty (superficial Camper) and membranous (deeper Scarpa) types, is found deep to the skin and subcutaneous tissue of the anterior abdominal wall.
Superficial vessels lie between these two layers
What are the flat muscles of the ant wall?
3 stacked
External oblique
internal oblique
Transversus abdominis
What happens to flat muscles at anteromedial aspect of ant. wall?
each flat muscle forms an aponeurosis (a broad, flat tendon), which covers the vertical rectus abdominis muscle. The aponeuroses of all the flat muscles become entwined in the midline, forming the linea alba (a fibrous structure that extends from the xiphoid process of the sternum to the pubic symphysis).
External oblique
The external oblique is the largest and most superficial flat muscle in the abdominal wall. Its fibres run inferomedially.
Attachments: Originates from ribs 5-12, and inserts into the iliac crest and pubic tubercle, also linea alba - fibres run inferomedially
Functions: Contralateral rotation of the torso.
Innervation: Thoracoabdominal nerves (T7-T11) and subcostal nerve (T12).
Internal oblique
Passes from the anterior part of the iliac crest and thoracolumbar fascia to the linea alba, pectineal line of the pubis via the conjoint tendon (shared with transversus abdominis) and inferior borders
of ribs 10-12.
Fibres run in a superomedial direction.
Functions: Bilateral contraction compresses the abdomen, while unilateral contraction ipsilaterally rotates the torso.
Innervation: Thoracoabdominal nerves (T7-T11), subcostal nerve (T12) and branches of the lumbar plexus.
Transversus abdominis
The transversus abdominis is the deepest of the flat muscles, with transversely running fibres. Deep to this muscle is a well-formed layer of fascia, known as the transversalis fascia.
Attachments: Originates from the inguinal ligament, costal cartilages 7-12, the iliac crest and thoracolumbar fascia. Inserts into the conjoint tendon, xiphoid process, linea alba and the pubic crest.
Functions: Compression of abdominal contents.
Innervation: Thoracoabdominal nerves (T7-T11), subcostal nerve (T12) and branches of the lumbar plexus
Discuss conjoint tendon
Attaches transversus abdominis and internal olique to the pubic symphysis
Rectus abdominis
The rectus abdominis is long, paired muscle, found either side of the midline in the abdominal wall. It is split into two by the linea alba. The lateral borders of the muscles create a surface marking known as the linea semilunaris.
At several places, the muscle is intersected by fibrous strips, known as tendinous intersections. The tendinous intersections and the linea alba give rise to the ‘six pack’ seen in individuals with a well-developed rectus abdominis.
Attachments: Originates from the crest of the pubis, before inserting into the xiphoid process of the sternum and the costal cartilage of ribs 5-7.
Functions: As well as assisting the flat muscles in compressing the abdominal viscera, the rectus abdominis also stabilises the pelvis during walking, and depresses the ribs.
Innervation: Thoracoabdominal nerves (T7-T11).
Arcuate line
At 1/3 of the distance between the umbilicus and the pubic symphysis.
The rectus sheath becomes deficient after this point
Blood supply of anterior wall
The anterior abdominal wall is supplied by the superior and inferior epigastric arteries, which arise from the internal thoracic and external iliac arteries respectively. The superior and inferior epigastric arteries form an anastomosis within the rectus sheath at the umbilicus.
Internal thoracic - subclavian - down inside of ribs
Innervation of anterior abdominal wall
The skin overlying the anterior abdominal wall is innervated by the segmental intercostal nerves (T6-T12). These nerves lie between the internal oblique and transversus abdominis muscles (the neurovascular plane) and when reaching the mid-axillary line, produce perforating branches to innervate the lateral abdominal wall. Within the muscle sheath of rectus abdominis, the nerves produce perforating branches to innervate the an- teromedial wall.
Borders of posterior wall
What are the 5 muscles that contribute to the posterior wall? What is their innervation?
Psoas major (L1-L3 anterior rami)
Psoas minor (L1 anterior ramus)
Iliacus (femoral nerve)
Quadratus lumborum (T12-L4 anterior rami)
Diaphragm (phrenic nerve)
What vascular structures are in the posterior abdominal wall? What levels are they?
Aorta (T12-L4)
Inferior vena cava (T8 -L5) Cisterna chyli (L1-L2)
(right and posterior to Aorta).
Quadratus lumborum
Attachments: It originates from the iliac crest and iliolumbar ligament. The fibres travel superomedially, inserting onto the transverse processes of L1 – L4 and the inferior border of the 12th rib.
Actions: Extension and lateral flexion of the vertebral column. It also fixes the 12th rib during inspiration, so that the contraction of diaphragm is not wasted.
Innervation: Anterior rami of T12- L4 nerves.
Psoas major
Attachments: Originates from the transverse processes and vertebral bodies of T12 – L5. It then moves inferiorly and laterally, running deep to the inguinal ligament, and attaching to the lesser trochanter of the femur.
Actions: Flexion of the thigh at the hip and lateral flexion of the vertebral column.
Innervation: Anterior rami of L1 – L3 nerves.
Psoas minor
Attachments: Originates from the vertebral bodies of T12 and L1 and attaches to a ridge on the superior ramus of the pubic bone, known as the pectineal line.
Actions: Flexion of the vertebral column.
Innervation: Anterior rami of the L1 spinal nerve.
Iliacus
Attachments: Originates from surface of the iliac fossa and anterior inferior iliac spine. Its fibres combine with the tendon of the psoas major, inserting into the lesser trochanter of the femur.
Actions: Flexion and lateral rotation of the thigh at the hip joint.
Innervation: Femoral nerve (L2 – L4).
Discuss paravertebral gutters
The para-vertebral gutters are deep, vertical recesses passing either side of the vertebral column. Quadratus lumborum passes within the para-vertebral gutters, just lateral to psoas.
Which muscle is the lumbar plexus found in?
Psoas major
What are lumbar and sacral plexus formed by?
Anterior rami of lumbar and sacral spinal nerves
Branches of lumbar plexus
Femoral nerve – supplies iliacus and the muscles of the anterior compartment of the thigh. Also provides cutaneous innervation to the thigh and leg.
Obturator nerve – passes through the obturator foramen to supply the adductor muscles of the thigh.
Subcostal, iliohypogastric and ilioinguinal nerves – equivalent of the intercostal nerves, passing around the abdominal wall within the neurovascular plane. The ilioinguinal nerve supplies the anterior part of the scrotum or labia.
Genitofemoral nerve – emerges on the anterior surface of psoas major. Supplies a small area of skin over the femoral triangle and the cremaster muscle.
Branches of sacral plexus
superior and inferior gluteal nerves, sciatic nerve, nerve to quadratus lumborum and the posterior cutaneous nerve of the thigh.
Discuss lumbar and sacral parts of the sympathetic chain
The lumbar and sacral parts of the sympathetic chain, which supply the distal GI tract, pelvic viscera, posterior abdominopelvic wall and the lower limbs, are found in the para-vertebral region of the posterior abdominal wall.
hiccoughing Reflex
Hiccoughs are spontaneous, myotonic, repetitive contractions of the diaphragm and intercostal musculature, which may be triggered by a range of stimuli including a large oral intake, carbonated drinks, alcohol, excitement and over-breathing.
The afferent component of the reflex arc begins with sensory fibres travelling with the Vagus nerve, phrenic nerve or sympathetic nerve fibres. Ultimately, these sensory fibres converge at the upper spinal cord, medulla, reticular formation and hypothalamus.
The efferent pathway is carried by the phrenic nerve to the diaphragm, typically causing unilateral, but occasion- ally bilateral contraction. This reflex is completed by closure of the glottis, triggered by the recurrent laryngeal branch of the Vagus nerve.
Abdominal skin Reflex
This is a superficial reflex obtained by firmly stroking the skin of the abdomen around the umbilicus. The reflex arc, carried by the anterior primary rami of T7-T12, normally results in a contraction of abdominal muscles, leading to the umbilicus moving toward the site of the stimulus.
