Anatomy 534 Muscles of the Trunk - PDF

om Anatomy 534 Muscles of the Trunk 2 Exay.am 12 89 Overview of the Torso Muscles: thorax...

om Anatomy 534 Muscles of the Trunk 2 Exay.am 12 89 Overview of the Torso Muscles: thorax Abdomen w o limbs Muscles of the toerso can be divided into 3 groups: 1) Muscles of the trunk walls: somatic muscles following a segmental pattern 2) Muscular diaphragms: thoracic, pelvic, and urogenital diaphragms, larynx and pharyngeal constrictors and suprapleural membranes 3) Muscles of the head and neck: some are from embryonic somites but most are derived from embryonic branchial (gill) arches and have a complex organization. Muscles of the Trunk Wall The muscles of the anterior and posterior walls of the trunk consist of bilaterally paired longitudinal muscle groups. Intrinsic Muscles of the Back (posterior wall): The posterior paired longitudinal groups of muscles are the intrinsic back muscles. They attach to the lever arms of the vertebrae. Dependent upon whether we hang by our hands , or stand on our feet, these muscles either extend the thorax or extend the pelvis. Remember that the intrinsic muscles of the back attach to the lever arms - and only the lever arms - of the vertebrae. These are the deep muscles of the back - often referred to collectively as the erector spinae muscle mass. They are responsible for maintenance of posture and movements of the head ands vertebral column. These muscles are names according to their relationship with the surface of the body and are classified into three groups: superficial, intermediate, and deep. The superficial and intermediate muscle groups are considered to be extrinsic - that is muscles of the back that deal primarily with: - limb movement (the superficial group) - respiration (the intermediate group) I. Superficial Extrinsics: We have already covered the superficial - or extrinsic - muscles of the back that connected the upper limb to the trunk. These were in two layers - layer one comprising the trapezius and latissimus dorsi; the layer two comprising the levator scapulae, rhomboid minor and rhomboid major. II. Intermediate Extrinsics: This layer of muscle lies under cover of the rhomboids superiorly and the latissimus dorsi inferiorly. Anatomy 534 Muscles of the Trunk 90 It consists of two flat inspiratory muscles that are also segmentally innervated by the dorsal rami of the intercostal nerves: the serratus posterior superior - thin sheets of fibers directed infero- laterally to the outer surfaces of R2-5 beyond the angles. It is a feeble elevator of the ribs; and serratus posterior inferior arising inferiorly from the spines of T11-L2 with the fibers directed superolaterally to the surfaces of R8-12 beyond their angles. It is a depressor or fixor of the lower ribs. splenis Bandage III. Deep (Intrinsic) Muscles of the Back: superficial A. Superficial Layer of Intrinsics Semisappings The splenius muscles exhibit a bandage-like appearance that extends over the sides and back of the neck. The splenius can be divided into cranial and all cervical portions. Both portions share a common origin into half of the ligamentum nuchae as well as the spinous processes of T1-6. d i) Splenius capitis inserts into the mastoid process and lateral 1/3 of the superior nuchal line on the occipital bone. ii) Splenius cervicis inserts into the posterior tubercles of the transverse processes of C1-4 deep to the levator scapulae. Acting alone the splenius mm. will laterally flex and rotate the head to the same side. Acting together they extend the head and neck. B. Intermediate Layer of Intrinsics mass The erector spinae is the chief extensor of the spine and its composite parts are all innervated segmentally. It forms a massive bulge on either side of the vertebral column and lies in a fascial compartment deep to the thoracolumbar fascia. They have a common inferior origin to the sacrum, iliac crest and sacroiliac ligament. Anatomy 534 Muscles of the Trunk 91 From this common origin 3 vertical columns arise: i) the spinalis muscle (medial column) extends from spinous process to spinous process. ii) the longissimus extends to the IHI m not transverse processes and ribs. iii) the iliocostalis (medial column) I extends to the angles of the ribs. it Each column has 3 parts dependent on location, but they are not well defined functionally. ii These muscles extend the head and vertebral column and can unilaterally flex it. insight ill martial Anatomy 534 Muscles of the Trunk 92 C. Deep Layer of Intrinsics P Removal of the erector spinae reveals several short muscles referred to as the transversospinal group. These muscles extend obliquely from transverse process below to spines or laminae above, missing several vertebrae between origin and insertion. i) the semispinalis has 3 parts: deep component - semispinalis capitis - semispinalis cervicis - semispinalis thoracis The semispinalis is the more superficial of the two transversospinals and misses 4 to 6 vertebrae between origin and insertion. spirit ii) the multifidus is several bundles of muscles that cover the laminae of the vertebrae. This muscle layer is superficial to the rotatores and misses one or two vertebrae I between origin and insertion. The next two members of the deep intrinsic ifeng.ir muscles of the back are short muscles that extend between adjacent vertebrae. iii) the rotatores are rotators and are between spinous and transverse0 the deepest muscles in the groove T Md processes. They span spinous to transverse process along the whole column but are best vis- y ualized in the thoracic region. iv) the intertransverse(ii) are lateral 1ffffddfddintm.int flexors linking adjacent trans- verse processes while the interspinales are extensors uniting the spinous processes of adjacent vertebrae. These last two groups are best developed in the lumbar and cervical regions.  Anatomy 534 Muscles of the Trunk Cross Section Through the Muscles of the Back IN EXAM Z Section taken through the midthoracic region. TP trans s spiciness Isesseersaining B ee aol.im iifzaeaofee's i Suboccipital Triangle Area The suboccipital triangle is a triangular area around the articulation between the occipital bone of the skull and the superior end of the vertebral column (C1 - the atlas and C2 - the axis). This region is deep to the semispinalis capitis. The suboccipital triangle is important clinically because of its main constituent - the vertebral artery. This is the region where the vertebral artery passes medially in a horizontal plane after ascending through the transverse foramina of the cervical vertebrae, and before it accesses the cranial cavity through the foramen magnum - also in the occipital bone. When the vertebral artery diameter narrows due to atherosclerosis, prolonged turning of the head - or looking upward (hyper-extension) - may cause dizziness due to impaired blood flow in this region. Anatomy 534 Muscles of the Trunk 94 Boundaries of the suboccipital triangle: superficial Deep - roof: semispinalis capitis m. - floor: atlanto-occipital membrane IYH - lateral: superior oblique m. LI - medial: rectus capitis major - inferior: inferior oblique m. There are 4 small muscles in this region: 1) rectus capitis (posterior) major: extends from C2 to the skull 1yiEis 2) rectus capitis (posterior) minor: extends s from C1 to the skull These are both postural muscles but can also rotate the head to the same side unilaterally as well as extend it when acting bilaterally. 3) Superior oblique: extends from C1 to the skull 4) Inferior oblique: extends from C2 to C1 (pulls on the atlas) THIN ieet eeaoe i a figf.si affffize.is Anatomy 534 Muscles of the Trunk 95 Contents of the suboccipital triangle: The vertebral artery entering the foramen magnum and lying horizontally in a groove on the superior surface of the posterior arch of the atlas (C1); and the suboccipital nerve - the dorsal ramus of C1. int MMMMM indeed after ventral Ramus ff.hrdadiri oooh ftp in EI as If 00th To spinous process of C2 transverse foramen of Cz