Lecture 2: Anterior abdominal wall including the inguinal canal Flashcards
Layers of ant abdominal wall
Skin
Sup. Fascia
Muscles and associated deep fascia
Extraperitoneal fascia
Parietal peritoneum
Sup. Fascia of ant. Abdominal wall consists of
connective tissue.
Contents of the superficial fascia of the abdominal wall varies depending on its
Location
Contents of the superficial fascia of the abdominal wall varies depending on its location:
Either above or below the umbilicus
Above the umbilicus the superficial fascia
=Single sheath of connective tissue and is continuous with sup. Fascia of other regions of the body
Below the umbilicus the superficial fascia
Sup. Fascia consists of 2 layers:
Superficial layer: Campers fascia (fatty layer)
Deep layer: Scarpa’s fascia (membranous layer)
In the midline just superior to the penis, we have
scarpas contribution to the formation of the fundiform lig of the penis
Muscles of the ant. Abdominal wall:
5 muscles divided into 2 groups:
Vertical and flat
VERTICAL MUSCLES: (2)
- rectus abdominis
- pyramidalis
- Situated near midline
Rectus abdominis
Rectus abdominis:
- Long, paired muscle
- Either side of the midline
- Divided into two by the linea alba
- Lateral border create a surface marking called the linea semilunaris (Semilunar line)
- Muscle intersected by fibrous strips known as tendinous intersections
- Tendinous intersections & linea alba give rise to the ‘six pack’
Rectus abdominis functions:
- – Bliateral contraction = flexion, compression
- – Unilateral contraction = lateral flexion
- – Assisting flat muscles in compressing the abdominal viscera
- – Stabilises pelvis during walking
- – Depresses ribs
Pyramidalis
Pyramidalis innervation
subcostal nerve (T12)
Pyramidalis characteristics
- Variable
- Small triangle shaped muscle
- Superficial to rectus abdominis
- Base on pubis bone
- Apex of triangle attached to linea alba
Pyramidalis function
Tenses linea alba
Flat muscles: (3)
– External oblique, internal oblique & transversus abdominis
– Situated laterally
– Stacked upon one another
Functions of flat muscles
- Flex, laterally flex & rotate trunk
- Fibres run in differing directions & cross each other
- Strengthening abdominal wall
- Decreasing the risk of herniation
- In anterior medial aspect of abdominal wall, each flat muscle forms an aponeurosis (broad flat tendon) which covers the vertical rectus abdominis muscle
- Aponeurosis of all the flat muscles becomes intertwined at the midline, which forms the linea alba
Linea alba extends from xhiphoid process to the pubic symphasis
INTERNAL OBLIQUEs VISIBLE-FIBRES ARE ___________ TO those of External oblique
PERPENDICULAR
External oblique:
- Largest and most superficial of all flat muscles on abdominal wall
- Integrates with serratus anterior
external oblique proximal attachment
Lower 8 ribs
external oblique distal attachment
Ant. Iliac crest, pubic tubercle, linea alba
external oblique innervation
ant. Rami of T7-T12
external oblique action
Unilateral: Contralateral rotation of trunk, lat. Flexion of trunk
Bilateral: flexion of trunk, compress and support viscera
external oblique fiber direction
Inferomedially (hands in pockets)
ASIS
= Ant superior iliac spine
- The lower free border of External Oblique which extends from the pubic tubercle
= ASIS –> forms inguinal ligament
Sup. Inguinal ring
= opening in aponeurosis of the EO for the spermatic cord/round ligament.
Internal oblique
Internal oblique characteristics
- Lies deep to the EO and is much smaller and thinner in structure
- Fibres runs superomedially (perp. To EO)
Internal oblique proximal attachment
Thoracolumbar fascia, ant iliac crest, inguinal lig.
Internal oblique distal attachment
Ribs 10-12, linea alba, pubis (via conjoint tendon)
Internal oblique innervation
ant. Rami of T6-L1 spinal nerves
Internal oblique action
Unilateral: ipsilateral rotation of trunk, lateral flexion of trunk
Bilateral: flexion of trunk, compress and support viscera
Conjoint tendon
The IO and transversus abdominus insert on pubic crest and pectineal line as a common tendon
Transversus abdominis
Transversus abdominis characteristics
- Deepest
- Fibers run transversely.
- Deep to this muscle we have the transversalis fascia
Transversus abdominis prox attachment
Thoracolumbar fascia, iliac crest, inguinal lig, lower 6 costal cartilages
Transversus abdominis distal attachment
linea alba, pubis (via conjoint tendon) and xhiphoid process
Transversus abdominis innervation
ant. Rami of T6-L1 spinal nerves
Transversus abdominis action
compress and support viscera
All abdominal muscles contribute to:
- Stabilization of the back (posture)
- Compression of abdominal viscera:
>Raises intraabdominal pressure
Defecation, childbirth, micturition, flatulence, vomiting.
>Raises intrathoracic pressure
Laughing, coughing, shouting.
Rectus sheath:
Formed by aponeuroses of the three flat muscles
- Encloses the rectus abdominus and pyramidalis muscles
- Consists of anterior and posterior wall for most of its length:
Ant. wall of rectus sheath
is formed by the aponeuroses of external oblique & 1⁄2 of internal oblique
Post. wall of rectus sheath
wall formed by aponeuroses of 1⁄2 internal oblique & transversus abdominus
± Midway between umbilicus & pubic symphysis all aponeuroses move to anterior wall of rectus sheath
- At this point no posterior wall to sheath
- Result: rectus abdominis in direct contact with transversalis fascia
- Transition zone between having a posterior wall, and no posterior wall is known as the arcuate line
arcuate line
