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Lecture 6

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University of Toronto Scarborough
Biological Sciences
Connie Soros

1 Lecture 6 The Muscular System Axial & Appendicular Musculature The Skeletal System: Articulations The body cannot move without joints Movements are linked to the range of joint action Joints (arthroses) are connections between bones that may or may not permit movement Two bones may be in direct contact with each other or separated by: Cartilage Fluid Fibrous tissue Joints are classified based on: Function Range of motion Structure Makeup of the joint Classification of Joints Joints can be classified based on their range of motion (function) Synarthrosis (immovable joint) Sutures (joints found only in the skull) Bones are interlocked together Gomphosis (joint between teeth and jaw bones) Periodontal ligaments of the teeth Synchondrosis (joint within epiphysis of bone) Binds the diaphysis to the epiphysis Synostosis (joint between two fused bones) Fusion of the three coxal bones Amphiarthroses (slightly movable joints) Syndesmosis (ligaments that connect two bones but limit their motion) Between the radius and ulna, between the tibia and fibula Symphysis (bones are separated by a wedge or pad of cartilage) Between the pubic bones of the two coxal bones Diarthroses (freely movable joints) Also called synovial joints Typically found at the ends of long bones Examples of diarthroses joints: shoulder joint, elbow joint, hip joint, knee joint Synovial joints : All synovial joints have six basic characteristics: A joint capsule The presence of articular cartilages A joint cavity with synovial fluid – lubricates the surfaces of the articular cartilages and reduces friction, nourishes the chondrocytes by entering and exiting the articular cartilage due to forces acting on the joint and acts as a shock absorber A synovial membrane Accessory structures (cartilage, ligaments, tendons, bursae sacs) Sensory nerves and blood vessels © 2012 Pearson Education, Inc. 2 Structural Classification of Synovial Joints Plane joints (gliding joints) Eg. Carpal/carpal – Tarsal/tarsal – Vertebrae/vertebrae – Clavicle/sternum Hinge joints Flexion and extension o Eg. Elbow and knee Pivot joints Rotational movements Eg. Atlas/axis Condylar joints (ellipsoidal joints) Oval articular surface on one bone articulates with a depression on another bone Eg. Radius/capitulum – Radius/carpals – Phalanges/metacarpals – Phalanges/metatarsals Saddle joints Biaxial joints that allow some circumduction Eg. Pollex/metacarpal Ball and socket joints Triaxial joints Eg. Shoulder joint – Hip joint Introduction The skeletal muscle of the body can be subdivided into: Axial musculature Muscles that position the head and vertebral column Muscles that move the rib cage Appendicular musculature Muscles that stabilize or move the appendicular skeleton The Axial Musculature The axial muscles can be placed into four groups based on location or function Muscles of the head and neck Muscles of the vertebral column Oblique and rectus muscles Muscles of the pelvic floor Muscles of the Head and Neck Can be subdivided into several different groups Muscles of facial expression (mouth, eye, nose, scalp, neck) Extraocular muscles (muscles that control eye movement) Muscles of mastication (chewing) Masseter – elevates mandible and closes jaws, assists in protracting and retracting mandible and moving mandible from side to side Temporalis – elevates mandible and closes jaws, assists in retracting and moving mandible from side to side Medial Pterygoid – elevates the mandible and closes the jawa, or moves the mandible side to side • Lateral Pterygoid – opens jaws, protrudes mandible, or moves mandible side to side Muscles of the tongue Muscles of the pharynx (pharyngeal constrictors, laryngeal elevators, © 2012 Pearson Education, Inc. 3 palatal muscles) Muscles of the anterior neck Digastric – depresses mandible, opening mouth, and/or elevates larynx Sternocleidomastoid –together they flex the neck, alone one side bends neck toward shoulder and turns face to the opposite side Sternohyoid – depresses hyoid bone and larynx Sternothyroid – depresses hyoid bone and larynx Thyrohyoid – elevates larynx depresses hyoid bone Stylohyloid – elevates larynx Muscles of the Vertebral Column Back muscles form three distinct layers Superficial layer (extrinsic back muscles): move the neck Trapezius – extends neck (will come back to more actions for this muscle) Latissimus dorsi – extension, adduction and medial rotation at shoulder, “swimmer’s muscle” Levator scapulae – elevates scapula Rhomboid muscles – adduct ad perform downward rotation of scapula Intermediate layer (extrinsic back muscles): move the vertebral column Serratus posterior – Superior – elevates ribs, enlarges thoracic cavity; Inferior – pulls ribs inferiorly, also pulls outward opposing the diaphragm Deep layer (intrinsic back muscles): interconnect the vertebrae Can be further subdivided into: Sup
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