Abdominal Muscles

This article or area is currently under construction and may only be partially complete. It will be changed to describe anterior and posterior abdominal walls. Please come back soon to see the finished work! (17/05/2020)

Original Editor - Anne Millar

Top Contributors - Anne Millar, Khloud Shreif, Lucinda hampton, Laura Ritchie, Kim Jackson, Admin, Joao Costa, Scott Buxton, Vidhu Sindwani and Evan Thomas

Introduction

The abdomen region is supported by the anterior and posterior abdominal wall that supports the viscera and maintains the posture where there's no bony support.

Anterior abdominal wall formed of 4 layer skin, fascia, muscles, and peritoneum. Muscles of the anterior abdominal wall consists of two vertical muscles located on the midline and bisected by linea alba; Rectus abdominis and pyramidalis and three flat muscles on the anterolateral side arranged from superficial to deep; external abdominal oblique, internal abdominal oblique, transversus abdominis.

Posterior abdominal wall consists of lumbar vertebrae, pelvic girdle, muscles and their associated fascia (quadratus lumborum, iliacus, psoas major and minor).
Acting together forming a firm wall that supports the muscles of the spine and help to maintain an erect posture, Support internal visceral organs where there is no bone, protect the abdominal viscera from injury and help to keep them in their anatomical position. In addition, the contraction of these muscles helps in forceful expiration and to increases the intra-abdominal pressure such as in sneezing, coughing, micturating, defecating, lifting, and childbirth.Hve a role in preventing hyperextension.

Anterior Abdominal Wall

Anterior wall fascia

Above the umbilicus it is a single connective tissue sheet as a continuous with superficial fascia. Below the umbilicus divided into two layers, camper’s fascia the superficial fatty layer, and Scarpa's fascia the membranous deep layer. Nerves and superficial vessels run Between the two layers.

Muscles of the anterior abdominal wall:

External obliques muscle, the most superficial anterolateral abdominal muscle its fibers run inferomedially, unilateral action results in ipsilateral side flexion and contralateral rotation of the trunk bilateral action to flex the vertebral column by drawing the pubis towards the xiphoid process.

Internal obliques directed superiomedially perpendicular to the external obliques it acts unilaterally for ipsilateral trunk rotation and side flexion and bilaterally to compress the abdominal viscera, pushing them up into the diaphragm, resulting in a forced expiration.

Transversus abdominis is the deepest of the abdominal muscles, it is an important core muscle and its primary function is to stabilise the lumbar spine and pelvis before movement of the lower and /or upper limbs occur.

Rectus abdominis is a long strap muscle that extends the entire length of the anterior abdominal wall lies close to the midline, it is an important postural and core muscle. With a fixed pelvis, contraction results in flexion of the lumbar spine. When the ribcage is fixed contraction results in a posterior pelvic tilt. It also plays an important role in forced expiration and in increasing intra-abdominal pressure.

Pyramidalis with rectus abdominis it forms the anterior abdominal wall when they contract bilateral tense the linea alba.

Rectus sheet:

The three anterolateral flat muscles (obliques and transversus abdominis) form an aponeurosis on both sides that is a broad flat tendon called rectus sheat, enclose the rectus abdominis, and consists of two layers anterior and posterior layer.

Transversus Abdominis

Anterior layer consisting of the aponeurosis of the external obliques and half of internal obliques, the posterior layer formed by the behalf of internal obliques and transversus abdominis. join in midline forming linea alba (in which the abdominal the abdominal muscles insert) extend from xyphoid process of sternum to symphysis pubis.
At a point midway between the umbilicus and symphysis pubis the posterior wall of the rectus sheet disappears and all aponeurosis sheet presented anterior forming anterior wall.

Clinical relevance

Transverse abdomimis as a deep abdominal muscle and one of main important core muscle that contributes to supporting lumbopelvic stability and deficit in its function affect our back causing low back pain (LBP). We need to include it in our rehabilitation program

Deficit in the abdominal wall muscles congenital from birth or acquired postoperatively as a result of a poor wound healing, wound infection, or acquired weakness after pregnancy and labor for example. can manifest in the form of hernia congenital or acquired.

Congenital hernia happens during infant development as a result of embryological malformations or weakness in neonatal abdominal wall, it may be fatal in some cases and need urgent and surgical intervention as; gastroschisis, or resolve without need to surgical intervention as in umbilical hernia.

Acquired hernia happens in the area of weakness and varies in its severity:

Umbilical hernia that is more serious and has a higher rate of morbidity in adult more than infants and may need surgical intervention. Inguinal hernia protrudes at the inferior border of anterolateral muscles. Epigastric hernia, above the umbilicus through the midline of linea alba. Spigelian hernias, and incisional hernia as a result of postoperative incision.

Rectus diastasis happens due to prolong transverse stress on linea alba during pregnancy, or post-menopausal women.

physical therapy intervention

Abdominal exercises need to be gradually progressed from how to activate muscles and maintain contraction to integrate them with functional movement, but there's special considerations, precaution, and exercise modification that we will take these exercises for a patient with a hernia.

• Abdominal draw in exercise, easy to apply, target mainly transversus abdominis as well as the diaphragm it's an important respiratory exercise. Exercise can be progressed by adding external resistance, upper limb or lower limb movement while holding abdomen drawing in

• Curl up exercise, target rectus abdominis, transverse abdominis, and obliques in addition to hip flexors, chest, and neck, start exercise with slow movement, few repetitions and make sure the back is in contact with the floor.

• Bridging, modified bridging with hip abduction or unstable surface show to increase core stability, trunk control. The activation of internal abdominis, rectus abdominis along with erector spine is greater in modified bridging when compared to standard bridging.

• Blank and pilates exercises activate and strengthen core muscles and abdominal muscles

Resources

Axial muscles of the abdominal wall and, thorax

TeachMeAnatomy: the anterolateral abdominal wall

Curl up exercise prescription Healthline

For more exercises description

Core stability- physiopedia page

Lumbar motor control training- physiopedia page