ANTERIOR ABDOMINAL WALLPart 1

ANTERIOR ABDOMINAL WALL


RECTUS SHEATH UNDER THE FOLLOWING HEADINGS:FORMATIONS AT DIFFERENT LEVELS,CONTENTS, APPLIED ANATOMY(LE
Rectus sheath is an aponeurotic sheath covering the rectus abdominis muscle
It has 2 walls- anterior and posterior.
Anterior wall- completely covers the muscle from end to end.
It is firmly adherent to tendinous intersections of the rectus muscle
Posterior wall – is incomplete, being deficient above the costal margin and below the                             arcuate line
  It is free from the rectus muscle





Formation
Above the costal margin:
Anterior wall- external oblique aponeurosis
Posterior wall- deficient, rectus muscle rests on 5th,6th, 7th costal cartilages.
Between the costal margin and arcuate line
Anterior wall- external oblique aponeurosis
                                           Anterior lamina of internal oblique aponeurosis


Posterior wall- posterior lamina of internal oblique aponeurosis
Aponeurosis of transverses muscle


Below the arcuate line
Anterior wall – aponeurosis of all the 3 flat muscles of abdomen
Posterior wall – deficient. The rectus muscle rests on fascia transversalis.

      
Content:
          Muscle,
Rectusabdominis,
 Pyramidalis




Arteries
Superior epigastric artery – terminal branch of internal thoracic artery
Inferior  epigastric artery- a branch of external iliac artery


Veins
Superior epigastric vena comitantes join the internal thoracic vein
Inferior epigastric vena comitantes join the external iliac vein


Nerves
     Terminal branches of lower six thoracic nerves


Functions
Checks bowing of rectus muscles during its contraction and thus increases the efficiency of the muscle
Maintains the strength of anterior abdominal wall.


New concept of rectus sheath formation
The aponeurosis of all the flat muscles of abdomen are bilaminar thus giving 6 laminae in all. Three layers form the anterior wall and three layers form the posterior wall of the rectus sheath.


Clinical anatomy
Divarication of recti
Separation of two rectus muscles occurs in elderly multiparous women with weak     abdominal muscles. Hernia sac containing loops of intestine protrude forward     between the widely separated recti.


Hematoma of rectus sheath-
Superior and inferior epigastric arteries are unduly stretched during a severe     bout of coughing or in later months of pregnancy, which ruptures when subjected to trauma. Thus an hematoma is formed within the rectus sheath.


Epigastric hernia-
The lineaalba is formed by the interlacing of aponeurotic fibres of the three          abdominal muscles. It is wider above the umbilicus and narrow below it . The part     becomes weak in elderly multiparous women. Raised intra abdominal  causes a small     amount of extraperitoneal fat along with a small containing greater omentum to protrude through the upper part of linea alba epigastric hernia.




UMBILICUS(SE)


Umbilicus is the normal scar in the anterior abdominal wall formed by the remnants of root of umbilical cord.
Position
In healthy adults it lies  in the anterior median plane at the level of disc between L3 and L4 vertebra. 
It is lower in infants and in persons with pendulous abdomen.


Anatomical significance
The level of umbilicus serves as watershed line for venous and lymphatic drainage.
 The venous blood and lymph flow upwards above the umbilicus and downwards below the umbilicus.
It indicates the level of T10 dermatome.
It is one of the important sites of portocaval anastomosis.


Embryological significance
It is the meeting point of four folds of embryonic plate.
In embryonic life , a defect exists in linea alba at this site called umbilical ring which provides passage to
Midgut loop which herniates into the umbilical cord during 10th – 12th weeks of intrauterine life.
Two endodermal loops- allantois and vitellointestinal duct
Umbilical vessels
















Clinical aspects
Congenital anomalies
Fecal fistula
Urinary fistula
Exomphalos
     Congenital umbilical hernia











 ANTERIOR ABDOMINAL WALL – BLOOD SUPPLY(SE)















Anterior abdominal wall is supplied by
Cutaneous arteries
Deep arteries


Cutaneous arteries
Cutaneous branches of superior and inferior epigastric arteries
Cutaneous branches of posterior intercostals arteries
Superficial branches of femoral artery- superficial external pudendal, superficial epigastric and  superficial circumflex iliac arteries


Cutaneous veins-





They accompany the arteries and drain as follows
Below the umbilicus- into the great saphenous vein – into inferior venacava
Above the umbilicus- into axillary vein – superior venacava.
Deep arteries
Superior epigastric  and musculophrenic arteries
inferior epigastricand deep circumflex iliac arteries
small branches of intercostals, subcostal and lumbar arteries.




EXTERNAL OBLIQUE MUSCLE(SE)
External oblique muscle is one of the three flat muscles of the abdomen,
Origin
Arises from eight fleshy slips from the outer surface ( middle of shaft) of lower eight ribs.













Insertion
The fibres run downward , forward and medially
Most of the posterior fibres pass vertically downwards to be inserted on the     anterior 2/3 of outer lip of iliac crest. Posterior border of muscle is free
The remaining fibres end in a aponeurosis which is inserted into linea alba extending from xiphoid process to pubic symphysis.


The upper border of aponeurosis is free and is overlapped by pectoralis major     muscle.
The lower border of aponeursis is free, thickened and rolled inwards to form the inguinal ligament
Just above the pubic crest the aponeurosis presents a triangular aperture called     superficial inguinal ring.
Nerve supply
Lower six thoracic nerves


Actions
Supports and protects the abdominal viscera
Compresses the abdominal viscera as in expulsive acts like micturition, defecation, vomiting
Forceful expiratory acts like coughing , sneezing .
Movements of the trunk- lateral flexion and rotation.


RECTUS ABDOMINIS(SE)
Rectus abdominis is a long , flat strap muscle extending vertically upwards along the     linea alba from pubic symphysis below to the costal margin above.
Origin
The muscle arises by two twotendinous heads
Lateral head from lateral part of pubic crest.
Medial head from anterior pubic ligament









Insertion
By four fleshy slips  along a horizontal line passing laterally from xiphoid process to     5th,6th and 7th costal cartilages


The muscle presents three tendinous intersections
Opposite to umbilicus
Opposite to free end of xiphoid process
Midway between the above two


The muscle is enclosed in aaponeurotic sheath derived from the three flat muscles of the abdomen.
Each tendinous intersection is attached to the anterior wall of rectus sheath and they     divide the long muscle column into shorter segments to provide more strength.


Nerve supply
Lower six thoracic nerves




Action
1. Flexion of the trunk at the lumbar region
2. It tenses the linea alba


















CONJOINT TENDON(SE)
Spermatic cord

Conjoint tendon ( falxinguinalis) is formed by the fusion of lower aponeurotic fibres of internal oblique and transverses abdominis muscles which arches over the spermatic cord and is attached to the pubic crest and medial part of pectin pubis.


It forms the medial half of the posterior wall of inguinal canal and strengthens the anterior abdominal wall opposite the superficial inguinal ring.
Medially it blends with the anterior wall of rectus sheath.
Laterally it may extend upto the interfoveolarligament( thickening in fascia transversalis along the medial border of deep inguinal ring) .


The weakening of Conjoint tendon due to old age or injury to iliohypogastric or ilioinguinal nerves predisposes the occurrence of direct inguinal hernia.


RECTUS SHEATH- FORMATIONS , CONTENTS AND APPLIED ANATOMY(SE)
Rectus sheath is an aponeurotic sheath covering the rectus abdominis muscle
It has 2 walls- anterior and posterior.
Anterior wall- completely covers the muscle from end to end.
It is firmly adherent to tendinous intersections of the rectus muscle


           Posterior wall – is incomplete, being deficient above the costal margin and below the arcuate                 line
It is free from the rectus muscle
Formation
Above the costal margin:
Anterior wall- external oblique aponeurosis
Posterior wall- deficient, rectus muscle rests on 5th,6th, 7th costal cartilages.


Between the costal margin and arcuate line
Anterior wall- external oblique aponeurosis
                                            Anterior lamina of internal oblique aponeurosis
Posterior wall- posterior lamina of internal oblique aponeurosis
           Aponeurosis of transverses muscle


Below the arcuate line
Anterior wall – aponeurosis of all the 3 flat muscles of abdomen
Posterior wall – deficient.the rectus muscle rests on fascia transversalis.







Contents
Muscles
Rectus abdominis
Pyramidalis
Arteries
 Superior epigastric artery – terminal branch of internal thoracic artery
  Inferior  epigastric artery- a branch of external iliac artery


Veins
Superior epigastric vena comitantes join the internal thoracic vein
Inferior epigastric vena comitantes join the external iliac vein


Nerves
    Terminal branches of lower six thoracic nerves


Functions
Checks bowing of rectus muscles during its contraction and thus increases the efficiency of the muscle
Maintains the strength of anterior abdominal wall.


New concept of rectus sheath formation
     The aponeurosis of all the flat muscles of abdomen are bilaminar thus giving 6 laminae in     all.three layers form the anterior wall and three layers form the posterior wall of the rectus  sheath