Human Anatomy - Muscles of the Body PDF

Human Anatomy Muscles of the Body- The Trunk Muscles (Back, Chest, Abdomen) Course: BL3420 Date: 2/12/24 Instructor: Benjamin T. Enslow, M.D. Email: [email protected] Phone: (830) 391-4298 Office: Moody 214 Text: Chapter 11; Select Muscle Tables Slides Adapted From: PowerPoint® Lecture Presentati...

Human Anatomy Muscles of the Body- The Trunk Muscles (Back, Chest, Abdomen) Course: BL3420 Date: 2/12/24 Instructor: Benjamin T. Enslow, M.D. Email: [email protected] Phone: (830) 391-4298 Office: Moody 214 Text: Chapter 11; Select Muscle Tables Slides Adapted From: PowerPoint® Lecture Presentations prepared by Leslie Hendon University of Alabama, Birmingham Molly Selba University of Florida Copyright © 2020 Pearson Education, Inc. All Rights Reserved Learning Objectives: List the major muscles of the back List the major muscles of the anterior chest wall List the major muscles of the anterior abdominal wall List the major muscles of the posterior abdominal wall Muscles of the Back The muscles of the back can be divided into three groups: o Superficial – associated with movements of the shoulder. o Intermediate – associated with movements of the thoracic cage. o Deep – associated with movements of the vertebral column. The deep muscles develop embryologically in the back and are thus described as intrinsic muscles. The superficial and intermediate muscles do NOT develop in the back and are classified as extrinsic muscles. Superficial Back Muscles The superficial back muscles originate from the vertebral column and insert on to the bones of the shoulder– the clavicle, scapula and humerus. All these muscles are therefore associated with movements of the upper limb. Superficial Back Muscles Trapezius muscle Most superficial muscle of the posterior thorax; very broad origin and insertion Origins: External occipital protuberance of occipital bone Ligamentum nuchae Spinous processes of C7 and T1-12 Occipital bone (External occipital protuberance) Ligamentum nuchae Spines of C7 and Thoracic vertebrae Superficial Back Muscles Trapezius muscle Most superficial muscle of the posterior thorax; very broad origin and insertion Insertions Scapular spine Acromion Lateral third of clavicle Actions Stabilizes, elevates, retracts, and rotates scapula Lateral third of clavicle (Anterior view) Acromion Scapular spine Superficial Back Muscles Trapezius Superior part Middle part Inferior part C7 T1 T2 Deltoid muscle T3 T7 Posterior median furrow Erector spinae Iliac crest, superior point Supracristal line at L4 Spinous processes Acromion Spine of scapula Medial border of scapula Teres major Inferior angle of scapula Triangle of auscultation Latissimus dorsi (superior border) L3 L5 Trapezius (lateral border) Superficial Back Muscles Superficial Back Muscles Latissimus dorsi Broad, flat muscle of lower back (lumbar region) Origins: Has a broad origin – arising from the spinous processes of T6T12, thoracolumbar fascia, iliac crest, and the inferior three ribs. Insertion Floor of the intertubercular sulcus of the humerus Action Prime mover of humeral extension Adducts and medially rotates arm Brings arm down in power stroke, as in striking a blow Superficial Back Muscles Superficial Back Muscles Levator scapulae Strap-like muscle located at back and side of the neck, deep to trapezius Origins: Transverse processes of C1-C4 Insertion Medial border of scapula superior to spine Action Elevates and adducts the scapula; With fixed scapula, laterally flexes neck to the same side Superficial Back Muscles Superficial Back Muscles Rhomboids Beneath trapezius and inferior to levator scapulae Two muscles: Rhomboid Major (inferior) Origin- Spinous processes of T2-T5 Insertion- Medial border of scapula Rhomboid Minor (superior) Origin- Spinous processes of C7-T1 Insertion- Medial border of scapula Actions Pulls scapula medially (retraction) Stabilizes scapula Rotates the glenoid cavity downward Superficial Back Muscles Intermediate Back Muscles Associated with movements of the thoracic cage (elevating and depressing the ribs). The intermediate group contains two muscles – the serratus posterior superior and serratus posterior inferior. These muscles run from the vertebral column to the ribcage. They are thought to have a slight respiratory function. Serratus posterior superior Serratus posterior inferior Intermediate Back Muscles The serratus posterior superior elevates the ribs, whereas.. the serratus posterior inferior pulls the ribs outward and downward, counteracting the inward pull of the diaphragm. Serratus posterior superior Serratus posterior inferior Deep Back Muscles The deep muscles develop embryologically in the back, and are thus described as intrinsic muscles. The deep muscles of the back are welldeveloped, and collectively extend from the sacrum to the base of the skull. They are associated with the movements of the vertebral column, and the control of posture. Anatomically, the deep back muscles can be divided into three layers; superficial, intermediate and deep. Superficial Spinotransversales Splenius capitis Splenius cervicis Intermediate Erector spinae Iliocostalis Longissimus Spinalis Deep Transversospinales Semispinalis Multifidus Rotatores (Superficial) Deep Back Muscles- Spinotransversales Splenius Capitis Origin: Ligamentum nuchae Spinous processes of C7-T3/4 Insertion: Mastoid process Occipital bone Splenius Cervicis Origin: Spinous processes of T3-T6 Insertion: Transverse processes C2-C4 Action: The two spinotransversales muscles work together to extend or hyperextend the head. Splenius Capitis Splenius Cervicis Deep Back Muscles- Spinotransversales (Intermediate) Deep Back Muscles- Errector Spinae The iliocostalis muscle is located laterally within the erector spinae The longissimus muscle is situated between the iliocostalis and spinalis. It is the largest of the three columns. The spinalis muscle is located medially within the erector spinae. It is the smallest of the three muscle columns. Lateral to Medial: “I Love Spines” Iliocostalis Longissimus Spinalis Action: Extend and laterally flex the vertebral column; Fascicles of the longissimus also extend and rotate the head Longissimus inserts superiorly onto the mastoid process (Deep) Deep Back Muscles- Transversospinales The deep intrinsic muscles are located underneath the erector spinae, and are known collectively as the transversospinales (Semispinalis) (Multifidus) (Rotatores) Action: As a group, stabilize the spine Suboccipital Muscles (Just an FYI- Don’t need to know) Suboccipital triangle Semispinalis (of transversospinalis) Muscles of the Anterior Chest Wall The pectoral region is located on the anterior chest wall. It contains four muscles that exert a force on the upper limb: Pectoralis major Pectoralis minor Serratus anterior (Subclavius) Muscles of the Anterior Chest Wall The pectoralis major is the most superficial muscle in the pectoral region. It is large and fan shaped, and is composed of a sternal head and a clavicular head: Origins: Clavicular head – originates from the anterior surface of the medial clavicle. Sternocostal head – originates from the anterior surface of the sternum, the superior six costal cartilages and the aponeurosis of the external oblique muscle. Insertion: The distal attachment of both heads is onto the intertubercular sulcus of the humerus. Action: Prime mover of arm flexion; adducts, medially rotates arm Muscles of the Anterior Chest Wall The pectoralis minor lies underneath its larger counterpart muscle, pectoralis major. Originates: 3rd-5th ribs Insertion: Coracoid process of the scapula Action: With ribs fixed, draw scapula forward and inferiorly The serratus anterior is fan-shaped muscle deep to scapula; deep and inferior to pectoral muscles on lateral rib cage. Originates: Ribs 1-8 Insertion: Vertebral border of anterior surface of scapula Action: Primer mover to protect and hold scapula against chest wall Muscles of the Anterior Abdominal Wall 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. Muscles of the Anterior Abdominal Wall Three flat muscles: located stacked upon one another. laterally, Fascicles run in differing directions and cross each other – strengthening the wall and decreasing the risk of abdominal contents herniating through the wall. Each flat muscle forms an aponeurosis (a broad, flat tendon), medially, which covers the vertical rectus abdominis muscle. The aponeuroses of all the flat muscles become entwined in the midline, forming the linea alba. Muscles of the Anterior Abdominal Wall The external oblique is the largest and most superficial flat muscle in the abdominal wall. Its fascicles run inferomedially. The internal oblique lies deep to the external oblique. It is smaller and thinner in structure, with its fascicles running superomedially (perpendicular to the fascicles of the external oblique). The transversus abdominis is the deepest of the flat muscles, with transversely running fascicles. Deep to this muscle is a well-formed layer of fascia, known as the transversalis fascia. Muscles of the Anterior Abdominal Wall There are two vertical muscles located in the midline of the anterolateral abdominal wall – the rectus abdominis and pyramidalis. The rectus abdominis is long, paired muscle, found either side of the midline in the abdominal wall. It is split into two by the linea alba. 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. Muscles of the Anterior Abdominal Wall External oblique Rectus abdominis Internal oblique Transversus abdominis Muscles of the Anterior Abdominal Wall The external oblique, internal oblique, and transversus abdominis muscles end in flat, tendon-like sheets called aponeuroses. The aponeuroses of these muscles join together at the linea alba. Superiorly, the rectus abdominus muscles are surrounded by these aponeuroses, which collectively are called the rectus sheath. Anterior ½ Aponeurosis of IO Linea alba Aponeurosis of EO RA EO IO TA ½ Aponeurosis of IO Posterior Aponeurosis of TA RA Anteriorly, the rectus sheath is made up of: The aponeurosis of the external oblique ½ the aponeurosis of the internal oblique Posteriorly, the rectus sheath is made up of: The aponeurosis of the transversus abdominus ½ the aponeurosis of the internal oblique Muscles of the Anterior Abdominal Wall Approximately midway between the umbilicus (belly button) and the pubic symphysis, all the aponeuroses move to the anterior wall of the rectus sheath. Anterior Linea alba Aponeurosis of IO Aponeurosis of EO RA EO RA IO TA Aponeurosis of TA Posterior At this point, there is no posterior wall to the sheath; the rectus abdominis is in direct contact with a thin layer of connective tissue called the transversalis fascia. The demarcation point where the posterior layer of the rectus sheath ends is the arcuate line. Rectus Sheath Above Arcuate Line Rectus Sheath Below Arcuate Line Muscles of the Posterior Abdominal Wall The quadratus lumborum muscle is located laterally in the posterior abdominal wall. It is a thick muscular sheet which is quadrilateral in shape. The muscle is positioned superficially to the psoas major. The psoas major is located near the midline of the posterior abdominal wall, immediately lateral to the lumbar vertebrae. The psoas minor muscle is only present in 60% of the population. It is located anterior to the psoas major. The iliacus muscle is a fan-shaped muscle that is situated inferiorly on the posterior abdominal wall. It combines with the psoas major to form the iliopsoas – the major flexor of the thigh.