Muscles Flashcards
How many abdominal wall muscles are there
8 muscles - 4 on each side Rectus abdominis External Oblique Internal oblique Transversus abdominis
What’s the function of the abdominal muscles as a group
Trunk Movement
Sitting up from lying, getting out of bed.
Protection of the abdominal viscera
Spinal stabilisation
Raising intra-abdominal pressure for:
○ Forced expiration
○ Micturition (urination;1) - Combined with appropriate sphincter relaxation, increased pressure on the bladder aids micturition
○ Defecation (2) - Combined with appropriate sphincter relaxation, increased pressure aids on the rectum, it assists defecation
○ Parturition (childbirth)- In the final stages of childbirth, the compressive force produced helps to expel the fetus from the uterus
○ Vomiting - Combined with appropriate sphincter relaxation, increased pressure aids on the stomach, it helps in vomiting
How is raising intra-abdominal pressure achieved
This is achieved by the ‘sheet’ muscles pulling on the rectus sheath via their aponeuroses, flattening the abdomen, compressing the abdominal viscera. If the diaphragm maintains its tone and resists upward displacement, the increase in intra-abdominal pressure is important in producing the ‘expulsive’ acts.
When the diaphragm is relaxed, the increased intra-abdominal pressure presses the abdominal viscera against its lower surface, pushing the diaphragm upwards, increasing intrathoracic pressure so that, when the glottis is opened, air is forced from the lungs in a violent, explosive cough or sneeze. The coughing action is reinforced by the abdominal muscles acting on the lower ribs, pulling them downwards. Pain resulting from surgical incision of the abdominal wall frequently causes inhibition of these muscles, making coughing very difficult.
The combined action of the abdominal muscles, together with the diaphragm, also produces a ‘muscular corset’ (valsalva manoeuvre) holding the abdominal viscera in place. This action can be increased during activities such as lifting, in which a form of pneumatic cushion is formed in front of the vulnerable lumbar spine. This action is frequently seen when people hold their breath, anchoring the diaphragm, prior to and when moving a heavy object.
What is the Thoracolumbar fascia (TLF)
Non-contractile extensive fascial sheet enclosing deep back muscles
Composed of 3 layers enclosing erector spinae & quadratus lumborum; unite laterally to give origin via conjoint tendon to internal oblique (IO) & transversus abdominis (TA)
TLF leaves a free posterior edge for external obliques
Lumbar region - thick & strong, between 12th rib and iliac crest
○ Important to fill gap between 12th rib and iliac crest, acting as a protective membrane; it is considered by some to function as a large ligament
Thoracic region – thin & transparent
○ Sandwiched between erector spinae and latissimus dorsi, and the rhomboids
Describe the posterior layer of TLF
a. Superficial to erector spinae & attached medially to spinous processes of the thoracic, lumbar and sacral vertebrae and associated supraspinous ligaments
b. It extends from the sacrum and iliac crest to the angles of the ribs, lateral to iliocostalis; latissimus dorsi partly arises from the strong membranous part of this layer in the lower part of the back
Describe the middle layer of TLF
a. Medially attached to the tips of the lumbar transverse processes and the intertransverse ligaments
b. Sandwiched between erector spinae and quadratus lumborum, joining the posterior layer at the lateral border of erector spinae
c. It extends from the lower border of the 12th rib and the lumbocostal ligament above to the iliac crest and iliolumbar ligament below
Describe the anterior layer of TLF
a. Thinnest of the three layers
b. Deep to QL, attached to anterior aspect of lumbar TPs medially; laterally, it fuses with the middle layer at the lateral border of QL
c. It extends from the iliac crest and iliolumbar ligament below to the lower border of the 12th rib
d. Superiorly, it is thickened between the 12th rib and TP of L1, forming the lateral arcuate ligament
What are the muscles of the anterolateral wall and their action and innervation
All muscles associated with rectus sheath 4 muscles Layers: • External oblique - most superficial • Internal oblique - middle layer • Transversus abdominis- most deep Vertical muscle = rectus abdominis
Rectus abdominis = Anterior primary rami of the lower six or seven thoracic nerves ( T6/T7–T12 )
EO, IO, TA = Anterior rami of the lower six thoracic and first lumbar nerves (T7–T12, L1)
Action (excluding TA) - mainly trunk/hip flexion or posterior pelvic tilt; contralateral rotation (RA/EO)/ ipsilateral rotation (IO) and ipsilateral side flexion
Give attachments for rectus abdominis
Origin: Anterior aspect of the pubic symphysis and pubic crest, via two tendons
Insertion: Passes vertically superiorly and widens to attaches to anterior surfaces of the xiphoid process and costal cartilages of the 5-7 ribs
Give position of rectus abdominis
Superficial muscles situated vertically on the left and right sides of anterior abdominal wall, enclosed within the rectus sheath; two muscles are separated by the linea alba
Intermediately anchored by transverse tendinous intersections (usually three) to give ‘6-pack’ appearance
Slightly convex lateral border presents as a groove, the linea semilunaris , on lean individuals
Give action of rectus abdominis
Trunk/hip flexion - bilateral
Trunk fixed (bilateral) - posterior pelvic tilt
Contralateral rotation (trunk on pelvis)- unilateral
Lateral flexion - ipsilaterally; reversed action: hip hitching
Compression of abdominal viscera
Give innervation of rectus abdominis
Anterior primary rami of the lower six or seven thoracic nerves ( T6/T7–T12 )
Give Palpation of rectus abdominis
On the anterior abdominal wall when the trunk is flexed against resistance.
In an athletic subject, possible to palpate the three transverse tendinous intersections, linea alba and semilunaris at the sides of each muscle
Give position of external oblique
Superficial muscle situated on left and right sides of the anterolateral abdominal wall, the fibres run inferomedially from the ribs towards the midline
most superficial of the three sheets of muscle forming the anterolateral abdominal wall; lateral to rectus abdominis
Give attachments of external oblique
Origin: Fleshy slips to the outer borders of the lower eight ribs (5-12) and their costal cartilages; interdigitating with serratus anterior above and latissimus dorsi below
Insertion:
Outer lip of the anterior 2/3 of the iliac crest, forming a large aponeurosis fusing with that of the opposite side at the linea alba; lower free border of the aponeurosis stretches between the pubic tubercle and ASIS forming the inguinal ligament.
Give action of external oblique
Trunk/hip flexion - bilateral; work w/ rectus abdominis & IO
Trunk (shoulder) fixed (bilateral) - posterior pelvic tilt
Contralateral rotation (trunk on pelvis)- unilateral; often w/ some trunk flexion
Lateral flexion - ipsilaterally; reversed action: hip hitching
Give innervation of external Oblique
Anterior rami of the lower six thoracic and first lumbar nerves (T7–T12, L1)
Give palpation of external oblique
Flat hand placed over the lower lateral aspect of the ribs may allow the contraction of external oblique to be felt on resisted flexion.
Give position of internal oblique
Muscles situated on left and right of anterolateral abdominal wall, deep to external oblique internal oblique and superficial to transversus abdominis
Fibres run supero-medially; continuous with angle fibres of EO on the contralateral side
Give attachments of internal oblique
Origin: Lateral ⅔ of inguinal ligament, anterior ⅔ of iliac crest, thoracolumbar fascia
Insertion:
Posterior fibres: pass almost vertically to inferior borders of lower 4 ribs (8-12) and costal cartilages
Anterior and inferior fibres: pass superomedially forming an aponeurosis fusing with that of the opposite side at the Linea alba; fibres arising from the inguinal ligament passes inferomedially, blending with the lower part of TA to form the conjoint tendon - attaching to the pubic crest and pecten pubis
Give action of internal oblique
Trunk/hip flexion - bilateral; work w/ rectus abdominis, EO
Trunk fixed (bilateral) - posterior pelvic tilt
Ipsilateral rotation (trunk on pelvis)- unilateral
Lateral flexion - ipsilaterally; reversed action: hip hitching
Give innervation of internal oblique
Anterior rami of the lower six thoracic and first lumbar nerves (T7–T12, L1)
Give palpation of internal oblique
Flat hand is placed over the lower abdomen just above the anterior half of the iliac crest and felt on resisted flexion
Give position of transversus abdominis
Deep to rectus abdominis, EO and IO
Fibres pass horizontally from TLF to midline anteriorly via rectus sheath
Give attachments of transversus abdominis
Origin: Lateral 1/3 inguinal ligament, anterior 2/3 inner lip of the iliac crest inferiorly; TLF posteriorly; inner surface of the costal cartilages of the lower 5-6 ribs superiorly (6/7-12), where it interdigitates with the attachment of the diaphragm
Insertion: Fibres pass horizontally around the abdominal wall, forming a aponeurosis fusing to its fellow at the linea alba; fibres arising from inguinal ligament arch downwards to join those from IO forming the conjoint tendon - attaching to the pubic crest and pecten pubis
Give action of transversus abdominis
Raises intra-abdominal pressure for all expulsive acts
Compression and support of abdominal viscera
Stabilising muscle of lumbar spine - prevents lumbar instability
