Muscles of the anterolateral abdominal wall Flashcards
How many large muscles are on either side of the midline of the anterolateral abdominal wall?
Four � external oblique, internal oblique, transversus abdominis, rectus abdominis
Name the two small muscles in the anterolateral abdominal wall.
Cremaster and pyramidalis
What structure is formed by the decussation of aponeuroses at the midline?
Linea alba
What muscle runs vertically on either side of the linea alba?
Rectus abdominis
From where does the external oblique muscle originate?
Outer surfaces of the middle of the shaft of the lower eight ribs
In what direction do the fibres of the external oblique run?
Downwards, forwards, and medially
Where are most of the fibres of the external oblique muscle inserted?
Xiphoid process, linea alba, pubic symphysis, pubic crest, and pectineal line
Into which structure are the lower fibres of the external oblique inserted?
Anterior two-thirds of the outer lip of the iliac crest
What nerves supply the external oblique muscle?
Lower six thoracic nerves
Which muscles interdigitate with the upper and lower slips of the external oblique?
Serratus anterior (upper four), latissimus dorsi (lower four)
What forms the inguinal ligament?
The free inferior border of the external oblique aponeurosis folded on itself
What does the aponeurosis of the external oblique form between the linea semilunaris and the linea alba?
Anterior wall of the rectus sheath
What is the superficial inguinal ring?
A triangular aperture in the external oblique aponeurosis above the pubic crest
Where does the internal oblique muscle originate?
Lateral two-thirds of the inguinal ligament, anterior two-thirds of the intermediate iliac crest, and thoracolumbar fascia
In what direction do the fibres of the internal oblique run?
Upwards, forwards, and medially
Where are the uppermost fibres of the internal oblique inserted?
Lower three or four ribs and their cartilages
What nerves supply the internal oblique muscle?
Lower six thoracic nerves and first lumbar nerve
How does the internal oblique aponeurosis contribute to the rectus sheath in the upper three-fourths of the wall?
Splits into an anterior and posterior lamina
What is the arcuate line?
Free lower margin of the posterior lamina of the internal oblique aponeurosis
What does the internal oblique form along with the transversus abdominis?
Conjoint tendon
What muscle is formed by fibres of the internal oblique?
Cremaster muscle
From where does the transversus abdominis originate?
Lateral one-third of inguinal ligament, anterior two-thirds of inner lip of iliac crest, thoracolumbar fascia, inner surfaces of lower six costal cartilages
In what direction do the fibres of the transversus abdominis run?
Horizontally forwards
Where is the transversus abdominis inserted?
Xiphoid process, linea alba, pubic crest, and pectineal line
What nerves supply the transversus abdominis muscle?
Lower six thoracic nerves and first lumbar nerve
Where does the aponeurosis of the transversus abdominis pass in relation to the rectus abdominis above the arcuate line?
Behind the rectus abdominis
Where does the aponeurosis of the transversus abdominis pass in relation to the rectus abdominis below the arcuate line?
In front of the rectus abdominis
What lies between the internal oblique and transversus abdominis muscles?
Neurovascular plane
From where does the rectus abdominis muscle originate?
Lateral and medial parts of the pubic crest and anterior pubic ligament
Where is the rectus abdominis inserted?
5th, 6th, and 7th costal cartilages and xiphoid process
What nerves supply the rectus abdominis?
Lower six or seven thoracic nerves
What are tendinous intersections in the rectus abdominis?
Three transverse fibrous bands dividing the muscle
Which muscle is most responsible for flexion of the trunk?
Rectus abdominis
Which muscles produce lateral flexion of the trunk?
Oblique muscles
Which muscles produce rotation of the trunk?
External oblique + opposite internal oblique
Which muscle depresses and compresses the lower part of the thorax for forceful expiration?
External oblique
What function do the abdominal muscles have in expulsive acts like vomiting or coughing?
Compress abdominal viscera
What forms the anterior wall of the rectus sheath below the arcuate line?
Aponeurosis of the internal oblique and transversus abdominis
What forms the conjoint tendon?
Lowest fibres of the internal oblique and transversus abdominis
What is the function of the conjoint tendon?
Strengthens the abdominal wall at the superficial inguinal ring
Where does the inguinal ligament extend between?
Anterior superior iliac spine to the pubic tubercle
What forms the lacunar ligament?
Medial end of the inguinal ligament
What does the cremasteric reflex test for?
Integrity of the L1 spinal segment
Which nerve is responsible for the cremasteric reflex?
Genital branch of the genitofemoral nerve
What lies between the aponeurosis of the external oblique and the inguinal ligament?
Inguinal canal
What makes the abdominal wall strong despite being thin?
Interdigitation of the aponeurotic laminae at the linea alba
What role do the abdominal muscles play in respiration?
Assist in forceful expiration
