Muscles of the Abdominal Wall

Functions of the Abdominal Wall

-Forms a firm, flexible wall which keeps the abdominal viscera in the abdominal cavity -Protects the abdominal viscera from injury -Maintains the anatomical position of abdominal viscera against gravity -Assists in forceful expiration by pushing the abdominal viscera upwards -Involved in any action (coughing, vomiting) that increases intra-abdominal pressure

Midclavicular lines

2 vertical planes run from the middle of the clavicle to the mid-inguinal point (halfway b/w anterior superior iliac spine of the pelvis & the pubic symphysis). These planes are called______________

Vertical Muscles

2; rectus abdominis, pyramidalis

Muscles of the Abdominal Wall

5 muscles divided into: 1.Vertical Muscles 2. Flat Muscles

Posterior Abdominal Wall Muscles

5 muscles in posterior abdominal wall: iliacus, psoas major, psoas minor, quadratus lumborum & diaphragm

Above the Umbilicus

A single sheet of connective tissue. Continuous with the superficial fascia in other regions of the body

Transversus Abdominus Action & NN

Action: Compresses the abdomen NN: 7-12 intercostal, iliohyogastric, ilioinguinal nerves

Quadratus Lumborum Action & NN

Action: Extension & lateral flexion of vertebral column, fixes 12th rib during inspiration, so the contraction of diaphragm is not wasted NN: Anterior rami of T12- L4 nerves

Internal Oblique Action & NN

Action: Flexes & rotates vertebral column, laterally flexes vertebral column NN: 8-12 intercostal, iliohyogastic, ilioinguinal

External Oblique Action & NN

Action: Flexes & rotates vertebral column, laterally flexes vertebral column NN: 8-12 intercostal, iliohyogastric, & ilioinguinal

Rectus Abdominis Action & NN

Action: Flexes vertebral column, compresses abdomen NN: 7-12 intercostal nerves

Psoas Major Action & NN

Action: Flexion of the thigh at the hip & lateral flexion of the vertebral column NN: Anterior rami of L1 - L3 nerves

Psoas Minor Action & NN

Action: Flexion of the vertebral column NN: Anterior rami of the L1 spinal nerve

Iliacus Action & NN

Action: Flexion of thigh at hip joint NN: Femoral nerve (L2 - L4)

Diaphragm Action & NN

Action: Inspiration NN: Phrenic, inferior phrenic, subcostal & inferior 6-7 intercostal nerves

Pyramidalis Action & NN

Action: Reinforces lower rectus sheath NN: Subcostal Nerve (T12)

Rectus Sheath parts

Anterior wall is formed by the aponeuroses of the external oblique, & 1/2 of the internal oblique. Posterior wall is formed by the aponeuroses of 1/2 the internal oblique & transversus abdominus. Midway b/w the umbilicus & the pubic symphysis, all of the aponeuroses move to the anterior wall of the rectus sheath. At this point, there is no posterior wall to the sheath; the rectus abdominus is in direct contact with the transversalis fascia. The area of transition between having a posterior wall, and no posterior wall is known as the arcuate line.

Vertical Muscles

Are 2 vertical muscles, situated near mid-line of body

Flat Muscles

Are 3 flat muscles, situated laterally

Transpyloric Plane

Horizontal line halfway b/w xiphoid process & umbilicus, passing through the pylorus of the stomach

Intertubercular Plane

Horizontal line that joins the iliac crests

Linea Alba

In the mid-line, the aponeuroses of all the flat muscles become entwined, forming the _____. This is a fibrous structure that extends from the xiphoid process of the sternum to the pubic symphysis

Internal Oblique Attachments

Origin: Anterior Iliac Crest, Lateral 1/2 of inguinal ligament, thoracolumbar fascia Insertion: costal cartialges of ribs 8-12, abdominal aponeurosis to linea alba

External Oblique Attachments

Origin: External Surfaces of ribs 5-12 Insertion: Anterior Iliac crest & abdominal aponeurosis to linea alba

Rectus Abdominis Attachments

Origin: Pubic crest & Pubic Symphysis Insertion: costal cartilages of ribs 5-7, xiphoid process of sternum

Pyramidalis Attachments

Origin: Pubic crest anterior to origin of rectus abdominis Insertion: Lower linea alba

Quadratus Lumborum Attachments

Origin: iliac crest & liolumbar ligament. Fibers travel superomedially Insertion: transverse processes of L1 - L4 & inferior border of 12th rib

Diaphragm Attachments

Origin: sternum & xiphoid process anteriorly, the L1 through the L3 lumbar vertebrae & arcuate ligaments posteriorly, & costal margin peripherally Insertion: central aponeurotic tendon

Iliacus Attachments

Origin: surface of iliac fossa & anterior inferior iliac spine. Its fibres combine w/ tendon of the psoas major Insertion: Lesser trochanter of the femur

Psoas Major Attachments

Origin: transverse processes & vertebral bodies of T12 - L5. Moves inferiorly & laterally, running deep to the inguinal ligament Insertion: Lesser Trochanter of the femur

Psoas Minor Attachments

Origin: vertebral bodies of T12 & L1 Insertion: ridge on the superior ramus of the pubic bone, known as the pectineal line

Transversus Abdominus Attachments

Origin:Anterior Iliac Crest, Lateral 1/2 of Inguinal Ligament, thoracolumbar fascia, cartilages of ribs 6-12 Insertion: Xiphoid process, pubic symphysis, abdominal aponeurosis to linea alba

Appendicitis

Right sided psoas sign is indication of _______. As the iliopsoas contracts, it comes into contact w/ the inflamed appendix, producing pain

2 horizontal planes

Transpyloric, intertubercular planes

Pyramidalis

a small triangle shaped muscle, found superficially to rectus abdominus. Located inferiorly, w/ its base on the pubis bone, & the apex of the triangle attached to the linea alba. It acts to tense the linea alba

9 abdominal regions

abdomen is large area & split into 9 regions - useful clinically for describing the location of pain, location of viscera & describing surgical procedures. 9 regions are formed by 2 horizontal planes, & 2 vertical planes

Thoracolumbar Fascia

consists of 3 layers; posterior, middle & anterior. Muscles are enclosed b/w these layers: -Quadratus lumborum - b/w anterior & middle layers -Deep back muscles - b/w middle & posterior layers

Superficial Fascia

consists of fatty connective tissue. Composition of this layer depends on its location: -above the umbilicus -below the umbilicus

Psoas Fascia

covers psoas major muscle. Attached to the lumbar vertebrae medially, continuous with the thoracolumbar fascia laterally & continuous w/ the iliac fascia inferiorly

Transversus Abdominus

deepest of the flat muscles, with transversely running fibres. Contributes aponeurotic fibres to the linea alba. Deep to this muscle is a well formed layer of fascia, called the transversalis fascia.

Below the Umbilicus

divided into 2 layers; the fatty superficial layer (Camper's fascia) & the membranous deep layer (Scarpa's fascia). Superficial vessels & nerves run b/w these 2 layers of fascia

Abdominal Wall

encloses the abdominal cavity, which holds the bulk of the gastrointestinal viscera

3 Flat Muscles

external oblique, internal oblique & transversus abdominis. Located laterally in abdominal wall, stacked upon one another. These muscles act to flex, laterally flex & rotate the trunk. Their fibres run in differing directions & cross each other - strengthening the abdominal wall & decreasing the risk of herniation.

Iliacus

fan-shaped muscle situated inferiorly on the posterior abdominal wall. Combines w/ psoas major to form the iliopsoas - the major flexor of the thigh

Camper's fascia

fatty superficial layer of superficial fascia below umbilicus

Linea Alba

fibrous line that splits the rectus abdominus into 2. It is visible as a vertical groove extending inferiorly from the xiphoid process

Rectus Sheath

formed by the aponeuroses of the 3 flat muscles, & encloses the rectus abdominus & pyramidalis muscles. Has an anterior & posterior wall for most of its length

External Oblique

largest & most superficial flat muscle in the abdominal wall. Its fibres run inferomedially. As the fibres approach the mid-line, they form an aponeurosis (a broad flat tendon)

Fascia of the Posterior Abdominal Wall

layer of fascia lies b/w parietal peritoneum & muscles of the posterior abdominal wall. This fascia is continuous with the transversalis fascia of the anterolateral abdominal wall

Layers of the Abdominal Wall

layers of abdominal wall consist of (external to internal): Skin Superficial fascia (or subcutaneous tissue) Muscles & associated fascia Parietal peritoneum

Diaphragm

located at inferior-most aspect of ribcage, filling the inferior thoracic aperture. Acts as floor of thoracic cavity & roof of abdominal cavity

Psoas Major

located near the midline of the posterior abdominal wall, immediately lateral to the lumbar vertebrae

Rectus Abdominis

long, paired muscle, found either side of the midline in abdominal wall. Split into 2 by the linea alba. Lateral border of the 2 muscles create a surface marking called the linea semilunaris. At several places, the muscle is intersected by fibrous strips, known as tendinous intersections. The tendinous intersections & the linea alba give rise to the 'six pack' seen in individuals with low body fat. As well as assisting the flat muscles in compressing the abdominal viscera, the rectus abdominus also stabilises the pelvis during walking, & depresses the ribs

Psoas sign

medical sign that indicates irritation to iliopsoas group of muscles. Sign elicited by flexion of the thigh at hip. Test is positive if patient reports lower abdominal pain

Scarpa's Fascia

membranous deep layer of superficial fascia below the umbilicus

Umbilicus

midway between xiphoid process & pubis symphysis

Internal Oblique

muscle lies deep to the external oblique. Smaller & thinner in structure, with its fibres running superiormedially (perpendicular to the fibres of the external oblique). Near the midline it forms aponeurotic fibres which contribute to the linea alba

Quadratus Lumborum

muscle located laterally in the posterior abdominal wall. Is a thick muscular sheet quadrilateral in shape. Positioned superficially to the psoas major

Psoas Minor

only present in 60% of the population. Located anterior to the psoas major

Linea Semilunaris

rectus abdominus gives rise to some abdominal markings. Lateral border of this muscle is indicated by _______, a curved line running from the 9th rib to the pubic tubercle