Abdomen anatomy Flashcards
Four layers of anterolateral abdominal wall
Skin
Superficial fascia (connective tissue)
Muscles and associated fascia
Parietal peritoneum
Abdominal wall flat muscles
External oblique
Internal oblique
Transverse abdominis
External oblique
Largest most superficial flat muscle runs inferomedially
Attachment: originates rib 5-12. Inserts into iliac crest and pubic tubercle
Function: Contralateral rotation of the torso
Innervation: Thoracoabdominal nerves (T7-T11) and subcostal nerve (T12)
Internal oblique
Lies behind external oblique. Runs superomedially (perpendicular to ext. oblique)
Attachment: Originates from the inguinal ligament, iliac crest and lumbodorsal fascia, and inserts into ribs 10-12.
Function: Bilateral contraction compresses the abdomen, while unilateral contraction ipsilaterally rotates the torso.
Innervation: Thoracoabdominal nerves (T6-T11), subcostal nerve (T12) and branches of the lumbar plexus.
Transverse abdominis
Deepest flat muscle. Fibres run transversly
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 (T6-T11), subcostal nerve (T12) and branches of the lumbar plexus.
Abdominal wall vertical muscles
Rectus abdominis
Pyramidalis
Rectus abdominis
Long paired muscles split at midline by linea alba and horizontally by tendinous intersections giving the 6 pack appearance.
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).
Pyramidalis
This is a small triangular muscle, found superficially to the rectus abdominis
Attachments: Originates from the pubic crest and pubic symphysis before inserting into the linea alba.
Functions: It acts to tense the linea alba.
Innervation: Subcostal nerve (T12).
Horizontal and vertical planes making up the nine regions of abdomen surface anatomy
Transpyloric plane
Intertubercular plane
Mid clavicular lines
What lies on the transpyloric plane
Origin of SMA, portal vein Spleen Neck of pancreas Pylorus of stomach Fundus of gallbladder Hilum of kidneys L1, just before end of spinal cord duodenojejunal flexure
5 major posterior abdominal muscles
Psoas major Psoas minor Iliacus Quadratus Lumborum Diaphragm
Quadratus lumborum
Located laterally in the posterior abdominal wall
Attachments: It originates from the iliac crest and iliolumbar ligament, travels 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
Near the midline of the abdominal wall lateral to the lumbar vertebrae
Attachment: 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
Only in 60% of the population. Anterior to psoas major
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
Fan shaped muscle. It combines with the psoas major to form the iliopsoas – the major flexor of the thigh.
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 of the thigh at the hip joint.
Innervation: Femoral nerve (L2 – L4)
