Trunk Muscle

Trunk muscles • Trunk muscles, also known as axial muscles, are essential for maintaining posture, movement, and supporting the spine. They include muscles in the abdomen, back, chest, and sides of the body, and play a vital role in various bodily functions thoracic muscles Pectoralis major, pectoralis minor, serratus anterior, subclavius, intercostals, subcostals, transversus thoracis, diaphragm Anterolateral Rectus abdominis, external abdominal abdominal oblique, internal abdominal oblique, wall muscles transversus abdominis, pyramidalis, quadratus lumborum superficial Superficial: Latissimus dorsi, trapezius, and rhomboid major and minor, levator scapulae intermediate Intermediate: Serratus posterior superior and back muscles inferior deep back muscles Superficial: Spinotransversales group (splenius capitis, splenius cervicis) Intermediate: Erector spinae group (iliocostalis, longissimus, spinalis) Deep: Transversospinal muscles (semispinalis, multifidus, rotatores longus and brevis) Deepest: Interspinales, intertransversarii BACK MUSCLES The muscles of the back may be divided into three groups: • The superficial group (trapezius, latissimus dorsi, levator scapulae,rhomboid major, rhomboid minor). These muscles connect the shoulder girdle with the vertebral column. • The intermediate group (serratus posterior superior, serratus posterior inferior) concerned with movement of ribs during respiration. • The deep group: This is a complex of large and small muscles concerned with movement of the vertebral column, ribs, and skull. The deep muscles of the back • are well-developed, and covered by deep fascia, which plays a key role in their organisation. • The deep muscles of the back are subdivided into : • Superficial • Intermediate • Deep. Deep back muscles : The Superficial layer Muscles • Also called spinotransversales • There are two muscles in this group • Splenius Capitis • Splenius Cervicis • They are both associated with movements of the head and neck. They are located on the posterolateral aspect of the neck, covering the deeper neck muscles. Deep back muscles : The intermediate Muscles • The Erector Spinae group: are the most powerful extensors of the vertebral column. • (from medially to laterally) consist of: 1. Iliocostalis 2. Longissimus 3. Spinalis • The muscle group is bilateral on either side of the vertebral column and when both sides are working together they act as extensor of the back. When Unilaterally working they assist with lateral bending and rotation of the spine. • They all have a common tendinous origin, which arises from: • Lower thoracic and lumbar vertebrae • Sacrum. • iliac crest. • Sacroiliac and supraspinous ligaments. Iliocostalis • The iliocostalis muscle is located laterally within the erector spinae. It is associated with the ribs, and can be divided into three parts – lumborum, thoracis, and cervicis. • Attachments: Arises from the common tendinous origin, and attaches to the angle of the ribs. Iliocosta lis Longissimus • Longissimus is the longest, thickest and most central erector spinae muscle. It is divided into three parts (capitis, cervicis, thoracis) based on their superior attachments and location. Longissimus Spinalis • the spinalis muscle is the smallest of the erector group. It is divided into three parts (capitis, cervicis, thoracis)and the most prominent and well-organised portion of the spinalis muscle is spinalis thoracis. • originated from the common tendinous origin, and attaches to the spinous processes of C2, T1-T8 and the occipital bone of the skull. spinalis Deep back muscles : The deep Muscles • 1-Transversospinales muscle group is a deep group of back muscles that lies deep to the Erector Spinae. It consists of 3 major subgroups: • Semispinalis, • Multifidus • Rotatores. • The transversospinalis muscles group runs obliquely and medially from the transverse process of the vertebra below to the spinous process, filling the groove on either side of the spinous process. • • • • • • • • • Semispinalis The semispinalis is the most superficial of the deep intrinsic muscles. divided by its superior attachments into thoracic, cervicis and capitis. Attachments: Originates from the transverse processes of C4T10. The fibres ascend 4-6 vertebral segments, attaching to the spinous processes of C2-T4, and to the occipital bone of the skull. Multifidus It is located underneath the semispinalis muscle. It is most developed in the lumbar area. Actions: Stabilises the vertebral column. Rotatores The rotatores are the deepest muscles of the transversospinales group. They are most prominent in the thoracic region. Attachments: Originates from the vertebral transverse processes. The fibres ascend and attach to the lamina and spinous processes of the vertebrae above. 2-Interspinales – extends between adjacent spinous processes. Acts to stabilize the vertebral column. 3-Intertranversarii – extends between adjacent transverse processes. Acts to stabilize the vertebral column. 4- Levatores costarum – Originates from the transverse processes of C7-T11, and attaches to the rib immediately below. Acts to elevate the ribs. Intertranversarii Interspinales Levatores costarum Back Muscle Nerve Supply • All the muscles constituting the superficial and intermediate groups of muscles of the back, except one, are innervated by anterior rami of spinal nerves. The exceptional muscle is the trapezius, which is supplied by the spinal accessory nerve (cranial nerve XI). • All the deep group muscles of the back are innervated by posterior rami of spinal nerves. DEEP FASCIA (THORACOLUMBAR FASCIA) • The lumbar part of the deep fascia is situated in the interval between the iliac crest and the 12th rib . • It forms a strong aponeurosis superficially with deeper running septa that enclose the main parts of the erector spinae muscles. -The thoracolumbar fascia splits into three lamellae which covers the deep muscles of the back Muscles of the Anterior Abdominal Wall • four pairs of sheetlike muscles – external abdominal oblique – internal abdominal oblique – transverse abdominal – rectus abdominis • strengthen abdominal wall Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Posterior Muscles: External abdominal oblique Anterior Internal abdominal oblique Peritoneum Transverse abdominal Rectus abdominis Subcutaneous fat Rectus sheath Linea alba Aponeurosis of Transverse abdominal Internal abdominal oblique External abdominal oblique Skin • The muscles of the anterolateral abdominal wall can be divided into two main groups: • Flat muscles – three flat muscles, situated laterally on either side of the abdomen. • Vertical muscles – two vertical muscles, situated near the mid-line of the body. • In the anteromedial aspect of the abdominal wall, each flat muscle forms an aponeurosis (a broad, flat tendon), which covers the vertical rectus abdominis muscle. The aponeuroses of all the flat muscles become mixed in the midline, forming the linea alba (a fibrous structure that extends from the xiphoid process of the sternum to the pubic symphysis). • • • • • • • • External Oblique The external oblique is the largest and most superficial flat muscle in the abdominal wall. Its fibres run inferomedially (down ward and forward). Attachments: Originates from ribs 5-12 and inserts onto the iliac crest and pubic tubercle. supports abdominal viscera stabilizes vertebral column during heavy lifting maintains posture aids in forced expiration rotation at waist • Internal Oblique • The internal oblique lies deep to the external oblique. It is smaller and thinner in structure, with its fibres running superomedially (perpendicu lar to the fibres of the external oblique). • Attachments: Originates from the inguinal ligament, iliac crest. It inserts onto ribs 10-12. • Actions: Bilateral contraction compresses the abdomen, while unilateral contraction ipsilaterally rotates the torso. • Transversus Abdominis • The transversus abdominis is the deepest of the flat muscles, with transversely running fibres. Deep to this muscle is a well-formed layer of fascia, known as the transversalis fascia. • Attachments: Originates from the inguinal ligament, costal cartilages 7-12, the iliac crest and thoracolumbar fascia. It inserts onto the conjoint tendon, xiphoid process, linea alba and the pubic crest. Rectus Abdominis • • • • • • • • long, paired muscle, found either side of the midline in the abdominal wall. It is split into two by the linea alba. The lateral borders of the muscles create a surface marking known as the linea semilunaris. At several places, the muscle is intersected by fibrous strips, known as tendinous intersections. The tendinous intersections and the linea alba give rise to the ‘six pack’ seen in individuals with a well-developed rectus abdominis. Attachments: Originates from the crest of the pubis bone. It inserts onto the xiphoid process of the sternum and the costal cartilage of ribs 5-7. Actions: As well as assisting the flat muscles in compressing the abdominal viscera, the rectus abdominis also stabilises the pelvis during walking, and depresses the ribs. Rectus Sheath The rectus sheath is formed by the aponeuroses of the three flat muscles and encloses the rectus abdominis and has an anterior and posterior wall for most of its length: Anterior wall – formed by the aponeuroses of the external oblique, and of half of the internal oblique. Posterior wall – formed by the aponeuroses of half the internal oblique and of the transversus abdominis.