MSK Muscle Anatomy
ANATOMY Notes
Hand Bones and Anterior Forearm Muscles
Flexors and Pronators
Mainly innervated by median nerve.
Supplied by radial/ulnar arteries.
Split into 3 layers:
Superficial Layer (ULRT):
Flexor Carpi Ulnaris:
Second head originates from olecranon of ulna.
Attaches to pisiform bone.
Function: wrist flexion/adduction.
Palmaris Longus:
Attaches at flexor retinaculum.
Function: wrist flexion.
Flexor Carpi Radialis:
Attaches to base of metacarpals II and III.
Function: wrist flexion/abduction.
Pronator Teres:
Second origin from coronoid process of ulna.
Attaches to shaft of radius.
Function: wrist pronation.
Intermediate Layer:
Flexor Digitorum Superficialis:
Second origin is radius.
Splits into 4 tendons, attaching at the base of each middle phalanx.
Functions in MCP joint and PIP joint flexion + wrist flexion.
Deep Layer (poll long digit pro pro quad):
Flexor Pollicis Longus:
Originates from radius.
Attaches to base of distal phalanx of thumb.
Function: flexes the IPJ and MCPJ of thumb.
Flexor Digitorum Profundus:
Originates from ulna.
Splits into 4 tendons, attaching at the base of each distal phalanx.
Functions in MCP joint and DIP joint flexion + wrist flexion.
Pronator Quadratus:
Attaches from ulna to radius.
Function: pronation of forearm.
Posterior Forearm Muscles
Extensors:
Innervated by radial nerve.
Superficial Extensors:
Brachioradialis:
Attaches from lateral supracondylar ridge to distal radius.
Functions in elbow flexion + supination (proximal radioulnar joint).
Extensor Carpi Radialis Longus & Brevis:
Attachments from lateral supracondylar ridge & lateral epicondyle respectively.
Functions in wrist extension and abduction.
Extensor Digitorum Communis:
Attaches from lateral epicondyle to extensor hoods of each finger.
Function: digit extension at IP and MCP joints.
Extensor Digiti Minimi:
Attaches from lateral epicondyle to extensor hood of little finger.
Function: extends little finger + wrist extension.
Extensor Carpi Ulnaris:
Attachments from lateral epicondyle + posterior ulnar to base of 5th MCP.
Function: wrist extension and adduction.
Anconeus:
Attaches from lateral epicondyle to olecranon.
Functions in elbow extension + ulna abduction during pronation.
Deep Extensors:
Supinator:
Attaches from lateral epicondyle + ulna to radius.
Function: supination.
Abductor Pollicis Longus:
Attaches from interosseous membrane + posterior ulna/radius surfaces to lateral base of 1st MCP.
Function: thumb abduction.
Extensor Pollicis Brevis:
Attaches from radius + interosseous membrane to base of 1st proximal phalanx.
Function: MCP and carpometacarpal extension.
Extensor Pollicis Longus:
Attaches from ulna + interosseous membrane to distal phalanx of thumb.
Function: extends all thumb joints.
Extensor Indicis Proprius:
Attaches from ulna + interosseous membrane to extensor hood of index finger (2nd digit).
Function: extension of index finger.
Intrinsic Hand Muscles
Thenar Compartment (median nerve)
Opponens Pollicis:
Attachments: trapezium + flexor retinaculum to 1st metacarpal.
Function: thumb opposition.
Abductor Pollicis Brevis:
Attachments: scaphoid/trapezium + flexor retinaculum to proximal phalanx of thumb.
Function: thumb abduction.
Flexor Pollicis Brevis:
Attachments: trapezium + flexor retinaculum to base of 1st proximal phalanx.
Function: flexes 1st MCPJ.
Hypothenar Compartment (ulnar nerve)
Opponens Digiti Minimi:
Attachments: hamate hook to 5th metacarpal.
Function: opposition.
Abductor Digiti Minimi:
Attachments: pisiform + flexor carpi ulnaris tendon to base of 5th proximal phalanx.
Function: abduction of 5th digit.
Flexor Digiti Minimi Brevis:
Attachments: hook of hamate to base of 5th proximal phalanx.
Function: flexes 5th MCPJ.
Lumbricals (4 muscles)
Innervation:
Lateral 2 = median nerve.
Medial 2 = ulnar nerve.
Originates from a tendon of digitorum profundus.
Passes dorsally around each finger and inserts into extensor hood.
Functions: flexes MCPJ and extends IP joints of each digit.
Interossei (ulnar nerve)
Dorsal Interossei (4 muscles):
Originates from lateral/medial surfaces of metacarpals.
Attaches into extensor hood and proximal phalanx of each finger.
Function: abducts the digits.
Palmar Interossei (3 muscles):
Originates from medial/lateral surface of metacarpals.
Attaches into extensor hood and proximal phalanx of the same finger.
Function: adduction of digits.
Other Palm Muscles
Palmaris Brevis:
Innervated by ulnar nerve.
Originates from palmar aponeurosis + flexor retinaculum.
Attaches to dermis medial margin of hand.
Function: wrinkles hypothenar eminence skin to improve grip.
Adductor Pollicis:
Innervated by ulnar nerve.
Originates from 2nd metacarpal (1st head) and capitate + adjacent metacarpals II and III (2nd head).
Attaches to base of proximal phalanx of thumb.
Function: adductor thumb.
Wrist Tendon Compartments
Abductor Pollicis Longus, Extensor Pollicis Brevis
Extensor Carpi Radialis Brevis & Longus
Extensor Pollicis Longus
Extensor Indicis & Digitorum
Extensor Digiti Minimi
Extensor Carpi Ulnaris
Upper Arm
Anterior Compartment (BBC)
All innervated by musculocutaneous nerve.
Biceps Brachii:
Attachments:
Long Head = supraglenoid tubercle of scapula.
Short Head = coracoid process.
Insertion = radial tuberosity.
Function: supination of forearm and elbow/shoulder flexion.
Brachialis:
Attachments:
Medial and lateral surfaces of humeral shaft.
Ulnar tuberosity.
Function: elbow flexion.
Coracobrachialis:
Attachments:
Coracoid process.
Medial side of humeral shaft.
Function: shoulder flexion (+ weak adduction).
Posterior Compartment
Triceps Brachii:
Innervated by radial nerve.
Attachments:
Long Head = infraglenoid tubercle of scapula.
Lateral Head = humerus (superior to radial groove).
Medial Head = humerus (inferior of radial groove).
Insertion = olecranon.
Function: elbow extension.
Gluteal Region
Mostly supplied by superior and inferior gluteal arteries – branches of internal iliac artery.
Venous drainage follows arterial supply.
Superficial Abductors and Extenders
Gluteus Maximus:
Attachments:
Gluteal surface of ileum, sacrum and coccyx.
Iliotibial tract and gluteal tuberosity of femur.
Function: thigh extensor (+ assists lateral rotation).
Innervation: inferior gluteal nerve.
Gluteus Medius:
Attachments:
Gluteal surface of ileum.
Lateral surface of greater trochanter.
Function: hip abduction and internal rotation.
Innervation: superior gluteal nerve.
Gluteus Minimus:
Attachments:
Ileum.
Tendon inserts at anterior greater trochanter.
Function: abduction and internal rotation.
Innervation: superior gluteal nerve.
Tensor Fascia Lata:
Attachments:
ASIS.
Iliotibial tract to lateral condyle of tibia.
Function: abduction and internal rotation of hip.
Innervation: superior gluteal nerve.
Note
Damage to superior gluteal nerve can cause Trendelenburg sign.
Deep Lateral Rotators
Piriformis:
Attachments:
Anterior sacrum.
Passes through greater sciatic foramen to greater trochanter.
Function: lateral rotation + abduction.
Innervation: nerve to piriformis.
Obturator Internus:
Attachments:
Pubis and ischia at obturator foramen.
Through lesser sciatic foramen to greater trochanter.
Function: lateral rotation + abduction.
Innervation: nerve to obturator internus.
The Gemelli (Superior/Inferior):
Attachments:
Superior = ischial spine.
Inferior = ischial tuberosity.
Insertion: greater trochanter.
Function: lateral rotation + abduction.
Innervation:
Superior = nerve to obturator internus.
Inferior = nerve to quadratus femoris.
Quadratus Femoris:
Attachments:
Lateral aspect of ischial tuberosity to quadrate tuberosity (on intertrochanteric crest).
Function: lateral rotation.
Innervation: nerve to quadratus femoris.
Thigh
Anterior Compartment (femoral nerve and femoral artery)
Iliopsoas:
Attachments:
Psoas Major = lumbar vertebrae.
Iliacus = iliac fossa.
Insertion: lesser trochanter.
Function: hip flexion.
Innervation:
Psoas Major = anterior rami L1-3.
Iliacus = femoral nerve.
Quadriceps Femoris:
(knee extension + stabilising patella)
Vastus Lateralis:
Attachments from greater trochanter + lateral lip of linea aspera.
Vastus Intermedius:
Attachments from anterior and lateral surfaces of femoral shaft.
Vastus Medialis:
Attachments from intertrochanteric line + medial lip of linea aspera.
Rectus Femoris:
Two heads; one from AIIS and other from supra-acetabular groove of ilium.
Tendon attaches to patella.
Action = knee extension + hip flexion.
Sartorius:
Attachments:
ASIS.
Superior/medial surface of tibia.
Function: hip flexion, abduction and external rotation + knee flexion.
Pectineus:
Attachments:
Pectineal line of pubis bone.
Pectineal line of posterior femur (just under lesser trochanter).
Function: adduction and flexion of hip.
Medial Compartment (obturator nerve and artery)
Gracilis:
Attachments:
Inferior rami and body of pubis.
Medial tibial shaft.
Function: adduction of hip and flexion of knee.
Obturator Externus:
Attachments:
Membrane of obturator foramen and adjacent bone.
Under neck of femur, inserts posterior on greater trochanter.
Function: hip adduction and lateral rotation.
Adductor Brevis:
Attachments:
Pubis and inferior pubic rami.
Linear aspera on posterior femur.
Function: thigh adduction.
Adductor Longus:
Attachments:
Pubis bone.
Along linea aspera of femur (fan-shaped).
Function: adduction of thigh.
Adductor Magnus:
Attachments:
Adductor = inferior rami of pubis and ischium → linea aspera of femur.
Hamstring = ischial tuberosity → adductor tubercle and medial supracondylar line of femur.
Functions:
Adductor = adduction + flexion of thigh.
Hamstring = adduction and extension of thigh.
Innervation:
Adductor = obturator nerve.
Hamstring = sciatic nerve.
Posterior Compartment (Hamstrings)
Biceps Femoris:
Attachments:
Long Head = ischial tuberosity.
Short Head = linea aspera on posterior femur.
Insertion = tendon inserts at fibula head.
Function: knee flexion + hip extension + external rotation of knee and hip (when knee is flexed).
Semitendinosus:
Attachments:
Ischial tuberosity.
Medial tibial surface.
Function: knee flexion + hip extension + internal rotation of hip and knee.
Semimembranosus:
Attachments:
Ischial tuberosity.
Posterior medial tibia (+ medial tibial condyle, deep to MCL, oblique popliteal ligament, popliteal fascia and posterior horn of medial meniscus).
Function: hip extension, knee flexion + internal tibial rotation.
Lower Leg
Anterior Compartment (deep fibular nerve & anterior tibial artery)
Tibialis Anterior:
Attachments:
Lateral surface of tibia.
Medial cuneiform and base of 1st metatarsal.
Action: dorsiflexion and inversion of foot.
Extensor Digitorum Longus:
Attachments:
Lateral condyle of tibia + medial surface of fibula.
Tendon splits into four and inserts onto a toe.
Action: extension of 4 toes, dorsiflexion of foot.
Extensor Hallucis Longus:
Attachments:
Medial surface of fibula.
Base of distal phalanx of big toe.
Action: extension of big toe and dorsiflexion of foot.
Fibularis Tertius:
Attachments:
Extensor digitorum longus from medial surface of fibula.
5th metatarsal.
Action: eversion and dorsiflexion of foot.
Lateral Compartment (superficial fibular (peroneal) nerve)
Fibularis Longus: (larger and more superficial)
Attachments:
Superior and lateral fibula.
Passes posterior to lateral malleolus → under the foot → medial cuneiform and base of 1st metatarsal.
Action: eversion + plantarflexion (+ supports lateral and transverse arches).
Fibularis Brevis:
Attachments:
Inferolateral fibula.
Descends with fibularis longus.
Attaches to tubercle on 5th metatarsal.
Action: eversion of foot.
Posterior Compartment (tibial nerve + mostly supplied by posterior tibial artery)
Superficial Muscles:
Gastrocnemius:
Proximal attachments:
Lateral Head = lateral femoral condyle.
Medial Head = medial femoral condyle.
Action: plantarflexion + knee flexion.
Soleus:
Proximal attachment: soleal line of tibia and proximal fibula.
Action: plantarflexion.
Plantaris:
Proximal attachment: lateral supracondylar line of femur.
Action: plantarflexion + knee flexion.
Deep Muscles:
Popliteus:
Attachments: lateral condyle of femur + lateral meniscus to proximal tibia.
Action: lateral rotation of femur relative to tibia → allows knee flexion.
Flexor Digitorum Longus:
Attachments: posterior surface of tibia to plantar surfaces of 4 digits.
Action: flexion of four toes.
Flexor Hallucis Longus:
Attachments: posterior surface of fibula to plantar surface of big toe phalanx.
Action: big toe flexion.
Tibialis Posterior:
Attachments:
Posterior surface of interosseous membrane of tibia and fibula.
Enters foot posterior to medial malleolus, attaches to plantar surfaces of medial tarsal bones.
Action: inversion + plantarflexion of foot (+ medial arch support).
Intrinsic Foot
Dorsal (deep fibular nerve)
Extensor Digitorum Brevis:
Attachments:
Calcaneus & inferior extensor retinaculum.
Long extensor tendons of toes 2-4.
Function: toe 2-4 extension.
Extensor Hallucis Brevis:
Attachments:
Calcaneus & inferior extensor retinaculum.
Base of proximal phalanx of great toe.
Function: hallux extension.
Plantar (tibial nerve branches)
1st Layer
Abductor Hallucis:
Attachments:
Medial tubercle of calcaneus, flexor retinaculum & plantar aponeurosis.
Medial base of proximal phalanx of hallux.
Action: abduction and flexion of great toe.
Innervation: medial plantar nerve.
Flexor Digitorum Brevis:
Attachments:
Medial tubercle of calcaneus + plantar aponeurosis.
2nd-5th middle phalanges.
Action: flexion of toes 2-4 at PIPs.
Innervation: medial plantar nerve.
Abductor Digiti Minimi:
Attachments:
Medial and lateral tubercles of calcaneus + plantar aponeurosis.
Lateral base of 5th proximal phalanx.
Action: abduction and flexion of little toe.
Innervation: lateral plantar nerve.
2nd Layer
Quadratus Plantae:
Attachments:
Medial and lateral plantar surfaces of calcaneus.
Tendons of flexor digitorum longus.
Action: assists in flexion of lateral 4 toes.
Innervation: lateral plantar nerve.
Lumbricals:
Four muscles, medial to respective tendon of flexor digitorum longus.
Attachments:
Flexor digitorum longus.
Extensor hoods of lateral 4 digits.
Action: flexion at MTPJ and extension at IPJs.
Innervation: medial lumbrical (medial plantar nerve), lateral 3 lumbricals (lateral plantar nerve).
3rd Layer
Flexor Hallucis Brevis:
Attachments:
Lateral head = plantar surface of calcaneus and lateral cuneiforms.
Medial head = tendon of posterior tibialis.
Insertion: base of proximal phalanx of hallux.
Action: flexion of great toe at MTPJ.
Innervation: medial plantar nerve.
Adductor Hallucis:
Attachments:
Oblique head = bases of 2nd-4th metatarsals.
Transverse head = plantar ligaments of MTPJs.
Insertion: lateral base of proximal phalanx of great toe.
Action: adduction of great toe (+ transverse arch support).
Innervation: deep branch of lateral plantar nerve.
Flexor Digiti Minimi Brevis:
Attachments:
Base of 5th metatarsal.
Base of proximal phalanx of 5th digit.
Action: flexion of little toe at MTPJ.
Innervation: superficial branch of lateral plantar nerve.
4th Layer
Plantar Interossei (3 – between metatarsals):
Attachments:
Medial side of metatarsals 3-5.
Medial side of phalanges of digits 3-5.
Action: adduction of lateral 3 digits and flexion at MTPJs.
Innervation: lateral plantar nerve.
Dorsal Interossei (4 – between metatarsals):
Attachments:
Lateral aspect of metatarsals.
1st muscle inserts to medial proximal phalanx of 2nd digit.
2nd-4th insert to lateral sides of proximal phalanxes of digits 2-4.
Action: abduction of lateral 4 digits + flexion of MTPJs.
Innervation: lateral plantar nerve.
Shoulder
Extrinsic Muscles
Superficial
Trapezius:
Attachments:
Skull, nuchal ligament and C7-T12 spinous processes.
Clavicle, acromion and scapula spine.
Action:
Upper fibres: elevate scapula and rotates during abduction of arm.
Middle fibres: retract scapula.
Lower fibres: pull scapula inferiorly.
Innervation: accessory nerve (+ proprioceptor fibres from C3-4).
Latissimus Dorsi:
Attachments:
Spinous processes T7-12, iliac crest, thoracolumbar fascia and inferior 3 ribs.
Intertubercular sulcus of humerus.
Action: extends, adducts and medial rotates upper limb.
Innervation: thoracodorsal nerve.
Deep
Levator Scapulae:
Attachments:
Transverse processes of C1-4.
Medial border of scapula.
Action: elevates scapula.
Innervation: dorsal scapular nerve.
Rhomboids Major:
Attachments:
Spinous processes T2-5.
Medial border of scapula between scapula spine and inferior angle.
Action: retracts and rotates scapula.
Innervation: dorsal scapular nerve.
Rhomboids Minor:
Attachments:
Spinous processes C7-T1.
Medial border of scapula at level of spine of scapula.
Action: retracts and rotates scapula.
Innervation: dorsal scapular nerve.
Intrinsic Muscles
Deltoid:
Attachments:
Lateral 1/3 of clavicle, acromion and spine of scapula.
Deltoid tuberosity on lateral humerus.
Action:
Anterior fibres: flexion and medial rotation.
Posterior fibres: extension and lateral rotation.
Middle fibres: abductor (takes over from supraspinatus which abducts the first 15 degrees).
Innervation: axillary nerve.
Teres Major:
Attachments:
Posterior surface of inferior angle of scapula.
Medial lip of intertubercular groove of humerus.
Action: adducts and extends at shoulder + medial rotation of arm.
Innervation: lower subscapular nerve.
Rotator Cuff Muscles
Supraspinatus:
Attachments:
Supraspinous fossa.
Greater tubercle of humerus.
Action: abduction (first 15 degrees, then assists deltoid for 15-90 degrees).
Innervation: suprascapular nerve.
Infraspinatus:
Attachments:
Infraspinous fossa.
Greater tubercle of humerus.
Action: external rotation.
Innervation: suprascapular nerve.
Teres Minor:
Attachments:
Posterior surface of scapula, adjacent to lateral border.
Greater tubercle of humerus.
Action: external rotation.
Innervation: axillary nerve.
Subscapularis:
Attachments:
Subscapular fossa (costal surface of scapula).
Lesser tubercle of humerus.
Action: internal rotation.
Innervation: upper and lower subscapular nerve.
Pectoral Muscles
Pectoralis Major:
Most superficial.
Attachments:
Clavicular Head = anterior surface of medial clavicle.
Sternocostal Head = anterior surface of sternum, superior six costal cartilages, and aponeurosis of the external oblique muscle.
Distal attachment: intertubercular sulcus of the humerus.
Function: adducts and internally rotates upper limb + anteroinferiorly draws the scapula + clavicular head also acts to individually flex the upper limb.
Innervation: lateral and medial pectoral nerves.
Pectoralis Minor:
Attachments:
3rd-5th ribs.
Coracoid process of scapula.
Function: stabilizes the scapula by drawing it anteroinferiorly against thoracic wall.
Innervation: medial pectoral nerve.
Serratus Anterior:
Attachments:
Lateral aspects of ribs 1-8.
Costal surface of medial scapula border.
Function: rotates scapula allowing the arm to be raised over 90 degrees + protracts scapula.
Innervation: long thoracic nerve.
Subclavius:
Attachments:
Junction of 1st rib and its costal cartilage.
Inferior surface of middle 3rd of clavicle.
Function: anchors and depresses clavicle.
Innervation: nerve to subclavius.
Back Muscles
Superficial
Trapezius
Latissimus Dorsi
Levator Scapulae
Rhomboids
Intermediate
Serratus Posterior Superior:
Attachments:
Lower part of ligamentum nuchae + cervical and thoracic spines (C7-T3).
Pass in inferolateral direction, inserting to ribs 2-5.
Function: elevates ribs 2-5.
Innervation: intercostal nerves.
Serratus Posterior Inferior:
Attachments:
Thoracic and lumbar spines (T11-L3).
Pass in superolateral direction, inserting to ribs 9-12.
Function: depresses ribs 9-12.
Innervation: intercostal nerves.
Intrinsic Muscles
Superficial (spinotransversales)
Splenius Capitis:
Attachments:
Lower aspect of ligamentum nuchae + spinous processes of C7-T3/4.
Mastoid process and occipital bone of skull.
Action: ipsilateral rotation of head.
Innervation: posterior rami of C3/4.
Splenius Cervicis:
Attachments:
Spinous processes of T3-6.
Transverse processes of C1-3/4.
Action: ipsilateral rotation of head.
Innervation: posterior rami of lower c-spine nerves.
Intermediate (erector spinae)
Iliocostalis:
Attachments:
Common tendinous origin.
Costal angle of ribs + cervical transverse processes.
Action: contracts unilaterally to laterally flex vertebral column, bilaterally to extend the vertebral column and head.
Innervation: posterior rami of spinal nerves.
Longissimus:
Attachments:
Common tendinous origin.
Lower ribs + transverse processes of C2-T12 + mastoid process.
Action: contracts unilaterally to laterally flex vertebral column, bilaterally to extend the vertebral column and head.
Innervation: posterior rami of spinal nerves.
Spinalis:
Attachments:
Common tendinous origin.
Spinous processes of C2, T1-8 + occipital bone.
Action: unilaterally to laterally flex vertebral column + bilaterally to extend the vertebral column and head.
Innervation: posterior rami of spinal nerves.
Deep (transversospinales)
Semispinalis:
Attachments:
Transverse processes C4-T10.
Ascend 2-4 vertebral segments to attach to spinous processes of C2-T4 + occipital bone.
Action: extends + contralateral rotation of head/vertebral column.
Innervation: posterior rami of spinal nerves.
Multifidus:
Attachments:
Sacrum, posterior iliac spine, common tendonous origin of erector spinae, mammillary process of lumbar vertebrae, transverse processes of T1-3 + articular processes of C4-7.
Ascends 2-4 vertebral segments to attach to vertebral spinous processes.
Action: stabilises column.
Innervation: posterior rami of spinal nerves.
Rotatores:
Attachments:
Transverse processes.
Lamina and spinous processes of vertebrae above.
Action: extension and rotation of column + stabilisation and proprioception.
Innervation: posterior rami of spinal nerves.
Minor Deep Intrinsic Muscles:
Interspinales:
Spans between adjacent spinous processes, acts to stabilise vertebral column.
Intertransversarii:
Spans between adjacent spinous processes, acts to stabilise vertebral column.
Levatores Costarum:
From transverse processes of C7-T11 to the rib immediately below – elevates ribs.
Thorax
Intercostal Muscles
External
Attachments:
Lower border of each rib.
Superior border of the rib below.
Actions:
Stabilises position of ribs during normal respiration + elevates ribs and increases thoracic volume during forced inspiration.
Innervation: intercostal nerves (T1-11).
Internal
Attachments:
Lateral edge of costal groove.
Superior surface of rib below.
Action: stabilises position of ribs during normal respiration + depresses ribs and decreases thoracic volume during forced expiration.
Innervation: intercostal nerves (T1-11).
Innermost
Attachments:
Medial edge of costal groove.
Superior surface of rib below.
Action: stabilises rib position during normal respiration + depresses ribs and decreases thoracic volume during forced expiration.
Innervation: intercostal nerves (T1-11).
Transverse Thoracis
Attachments:
Posterior surface of inferior sternum and costal cartilage of lower ribs.
Internal surface of costal cartilages 2-6.
Actions: weak depressors of ribs during expiration.
Innervation: intercostal nerves (T2-6).
Subcostales
Attachments:
Inferior surface of lower ribs.
Superior border of 2nd or 3rd rib below.
Actions: stabilises the position of ribs during normal respiration + depresses ribs and decreases thoracic volume during forced expiration.
Innervation: intercostal nerves.
Abdomen
Superficial Fascia
Connective tissue:
Above umbilicus = single sheet of CT continuous with superficial fascia in other body regions.
Below umbilicus = 2 layers – fatty superficial (Camper’s) and membranous deep layer (Scarpa’s).
Superficial vessels and nerves run between the two layers of fascia.
Anterolateral Abdominal Wall
Flat Muscles (laterally):
External Oblique:
Attachments: Ribs 5-12 to iliac crest + pubic tubercle.
Function: contralateral rotation of torso.
Innervation: thoracoabdominal nerves (T7-11) + subcostal nerve (T12).
Internal Oblique:
Attachments: Inguinal ligament + iliac crest + lumbodorsal fascia to ribs 10-12.
Function: bilaterally compress abdomen; unilaterally ipsilaterally rotates torso.
Innervation: thoracoabdominal nerves (T7-11), subcostal nerve (T12) + lumbar plexus branches.
Transversus Abdominis:
Attachments: Inguinal ligaments, costal cartilages 7-12, iliac crest + thoracolumbar fascia to conjoint tendon, xiphoid process, linea alba and pubic crest.
Function: compress abdomen.
Innervation: thoracoabdominal nerves (T7-11), subcostal nerve (T12) + lumbar plexus branches.
Vertical Muscles
Rectus Abdominis:
Attachments: Crest of pubis bone to xiphoid process of sternum + costal cartilage of ribs 5-7.
Function: compresses abdominal viscera + stabilises pelvis during walking + depresses the ribs.
Innervation: thoracoabdominal nerves (T7-11).
Pyramidalis:
Attachments: Pubic crest and symphysis to linea alba.
Function: tenses linea alba.
Innervation: subcostal nerve (T12).
Rectus Sheath
Aponeurosis of 3 flat muscles and encloses the rectus abdominis and pyramidalis.
Anterior wall: aponeurosis of external oblique and half of internal oblique.
Posterior wall: aponeurosis of half internal oblique and transversus abdominis.
Midway between umbilicus and pubic symphysis, all aponeuroses move anteriorly: at this point, there is no posterior wall; rectus abdominis is in direct contact with transversalis fascia.
Demarcation point where posterior layer ends is the arcuate line.
Posterior Abdominal Wall
Quadratus Lumborum:
Attachments:
Iliac crest + iliolumbar ligament to transverse processes of L1-4 + inferior border of 12th rib.
Function: extension + lateral flexion of vertebral column + fixes 12th rib during respiration.
Innervation: anterior rami of T12-L4.
Psoas Major:
Attachments:
Transverse processes + vertebral bodies of T12-L5.
Attaches to lesser trochanter of femur.
Function: flexion of thigh at hip + lateral flexion of vertebral column.
Innervation: anterior rami of L1-3.
Psoas Minor:
Attachments: Vertebral bodies T12-L1 to pectineal line on superior ramus of pubic bone.
Function: flexion of vertebral column.
Innervation: anterior rami of L1.
Iliacus:
Attachments:
Surface of iliac fossa + AIIS.
Combines with tendon of psoas major to insert into lesser trochanter of the femur.