Skeletal and Muscular System PDF

Lecture 1  Directional Terms  Healthcare professionals use standardized terms to describe body directions. ◦ Superior and inferior ◦ Anterior (ventral) and posterior (dorsal) ◦ Medial and lateral ◦ Proximal and distal  All descriptions assume that the body is in an...

Lecture 1  Directional Terms  Healthcare professionals use standardized terms to describe body directions. ◦ Superior and inferior ◦ Anterior (ventral) and posterior (dorsal) ◦ Medial and lateral ◦ Proximal and distal  All descriptions assume that the body is in anatomic position. Planes of Division  Anatomists can divide the body along three planes, each of which is a cut through the body in a different direction ◦ Frontal plane ◦ Sagittal plane ◦ Transverse plane  The skeletal system is made up of bones, joints, and supporting connective tissue. What are bone functions ? Bone Functions  Act as a framework for body  Protect delicate structures ◦ Examples: Brain, spinal cord, lungs, heart  Work as levers to produce movement  Store calcium and phosphorus  Produce blood cells https://www.visiblebody.com/learn/skeleton/types-of-bones  Joints Joints hold the skeleton together and support movement. There are two ways to categorize joints. The first is by joint function, also referred to as range of motion. The second way to categorize joints is by the material that holds the bones of the joints together; that is an organization of joints by structure. Joints in the human skeleton can be grouped by function (range of motion) and by structure (material). Joint - Range of Motion and Material Skull Sutures - Immovable fibrous joints Knee - Full movement synovial capsule hinge joint Vertebrae - Some movement cartilaginous joint Joints Can Be Grouped By Their Function into Three Ranges of Motion Joints Can Be Grouped By Their Structure into Fibrous, Cartilaginous, and Synovial Joints Fibrous Joints. Between the articulations of fibrous joints is thick connective tissue, which is why most (but not all) fibrous joints are immovable (synarthroses). There are three types of fibrous joints: Cartilaginous Joints. Joints that unite bones with cartilage are called cartilaginous joints. There are two types of cartilaginous joints: Synovial joints are characterized by the presence of an articular capsule between the joined bones. Bone surfaces at synovial joints are protected by a coating of articular cartilage separated by articular (joint) cavity. Synovial joints are often supported and reinforced by surrounding ligaments, which limit movement to prevent injury. Synovial joints may posses additional protective structures: meniscus, fat, bursae Two joined bones – simple joint More than two – complex joint Type of Type of Movement Examples Joint Gliding Flat bone surfaces slide Joints in vertebral joint over one another with column little change in joint angle Hinge joint Allows movement in Elbow joint; joints one direction, changing between phalanges the angle of the bones of fingers and toes at the joint, as in flexion and extension Pivot joint Allows rotation around Joint between the the length of the bone first and second cervical vertebrae; joint at proximal Type of Type of Movement ends of radius and Examples Joint ulna Condyloid Allows movement in Joint between the joint two directions; flexion metacarpal and extension, abduction and adduction Saddle joint Like a condyloid joint Joint between the but with deeper wrist and the articulating surfaces metacarpal bone of and movement in three the thumb directions; rotation, flexion and extension, abduction and adduction Ball-and- Allows the greatest Shoulder joint and socket joint range of motion; hip joint permits movement in three directions around a central point, as in circumduction Movements at Synovial Joints  Flexion - Extension  Abduction - Adduction  Rotation : internal - external  Circumduction Movements Characteristic of Forearm and Ankle Supination - Pronation Inversion - Eversion Dorsiflexion - Plantar flexion Two main groups of bones: Axial skeleton —80 bones of the head and trunk Appendicular skeleton —126 bones of the extremities Bone  Loss of calcium salts and collagen  Bone weakening  Reduction in collagen Joints  Thinning of cartilage  Decreased flexibility The Muscular System Skeletal Muscle Has Three Primary Functions:  Skeletal movement  Posture maintenance  Heat generation Muscle Structure  Fascicles ◦ Bundles of muscle cells (fibers) that make up a whole muscle  Connective tissue ◦ Hold fascicles and whole muscle together ◦ Three layers  Endomysium  Perimysium  Epimysium  Tendons Muscle Cells in Action  Motor unit: A single neuron and all the muscle fibers it stimulates ◦ Small motor units used for fine movements ◦ Large motor units used for broad movements Muscle Cells in Action  Neuromuscular junction (NMJ): The point at which a nerve fiber contacts a muscle fiber ◦ A type of synapse ◦ NMJ anatomy  Motor neuron  Neurotransmitter (acetylcholine; ACh)  Motor end plate (on muscle fiber) ▪ Contains acetylcholine receptors Muscles Work Together ◦ Prime movers - The prime mover, also called agonist, is the muscle that provides the primary force driving the action. ◦ Antagonists - An antagonist muscle is in opposition to a prime mover in that it provides some resistance and/or reverses a given movement. ◦ Prime movers and antagonists are often paired up on opposite sides of a joint, with their prime mover/antagonist roles reversing as the movement changes direction. ◦ Synergists – support prime mover Characteristics for Naming Muscles Characteristic Example Location Temporalis; near the skull’s temple Size Gluteus maximus; the largest Shape Serratus anterior; serrated edge Direction External oblique; runs obliquely Number of heads Biceps brachii; two heads Action Flexor digitorum; flexes toes  Beginning at about age 40  Gradual loss of muscle cells  Loss of power  Tendency to flex hips and knees  Decrease in height