Skeletal System 2: Structure and Function of the Musculoskeletal System
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Copyright EMAP Publishing 2020 This article is not for distribution except for journal club use Clinical Practice Keywords Musculoskeletal health/ Musculoskeletal system/Skeletal system Systems of life This article has been Skeletal system double-blind peer reviewed In this article... l The structure and function of muscles and joints l How pathology can affect the musculoskeletal system l Ways to promote good musculoskeletal health Skeletal system 2: structure and function of the musculoskeletal system Key points Author Jennie Walker is principal lecturer, Nottingham Trent University. The musculoskeletal system comprises Abstract Understanding the structure and purpose of the musculoskeletal system bones, cartilage, enables practitioners to understand common pathophysiology and consider the most ligaments, tendons appropriate steps to improve musculoskeletal health. This article, the second in a and muscles that two-part series, considers the structure and function of the musculoskeletal system, form a framework reviews the structure of muscles and joints and identifies some of the common for the body pathology occurring at these structures. The structure of a Citation Walker J (2020) Skeletal system 2: structure and function of the joint determines its musculoskeletal system. Nursing Times [online]; 116: 3, 52-56. plane and range of movement he musculoskeletal system is Joints Maintaining a made up of bones, cartilage, liga- The joints are the articulating surfaces healthy diet and ments, tendons and muscles, between two bones and may be classified physical exercise are Twhich form a framework for the according to how much movement they essential for good body. Tendons, ligaments and fibrous allow: musculoskeletal tissue bind the structures together to create l Synarthrosis – a fixed, unmovable joint; health stability, with ligaments connecting bone l Amphiarthrosis – a joint in which some to bone, and tendons connecting muscle to movement is possible; Musculoskeletal bone. There are 206 bones in the adult skel- l Diarthrosis – a freely movable joint pathophysiology eton; male and female skeletons are almost (Moini, 2020). can significantly the same, but the female skeleton has a They can also be classified according to reduce functional broader pelvis to accommodate childbirth the components that unite the bones (such as ability and quality and the male skeleton is typically taller fibrous structures, cartilaginous structures of life with greater bone density. The skeleton is and synovial structures), as shown below. divided into the: Understanding the l Axial skeleton – comprising the skull, Fibrous joints anatomy and vertebral column and the rib cage; Fibrous joints are articulating surfaces physiology of the l Appendicular skeleton – consisting of linked together with tough fibrous con- musculoskeletal the pelvic and pectoral girdles, and the nections. One example is the suture lines system allows upper and lower limbs (Cedar, 2012). in the skull, where bones that were initially practitioners to Coordinated movement is made pos- separate have become fused together (syn- consider signs and sible through the combination of pur- ostosis) to form one bone (Danning, 2019). symptoms, and poseful and synchronised movements As the suture line does not permit move- determine across the relevant muscles and bones to ment once fusion has occurred, this is con- appropriate create articulation of the joints. The con- sidered to be a synarthrotic joint. management figuration of the joint surface determines Syndesmoses are another type of the movement possible. Planes of move- fibrous joint, in which ligaments and ment include flexion, extension, abduc- interosseous membrane connect the joint tion, adduction, rotation and circumduc- to create a firm structure. One example is tion (Table 1). the inferior tibiofibular joint, in which Nursing Times [online] March 2020 / Vol 116 Issue 3 52 www.nursingtimes.net Copyright EMAP Publishing 2020 This article is not for distribution except for journal club use Clinical Practice Systems of life interosseous, tibiofibular and transverse ligaments connect the distal tibia and Table 1. Planes of movement at the joint fibula of the lower leg. Another is the Movement Description Illustration radioulnar joint, where an intraosseous Flexion Bending the joint: membrane connects the distal radius and decreases the angle ulnar bones of the forearm. This can also between the bones be classified as an amphiarthrotic joint as it permits some movement to allow for Extension Straightening the limb Elbow (continuing the extension pronation and supination of the hand and joint Flexion past the anatomical forearm. straight line may be described as Extension Cartilaginous joints hyperextension) These joints are connected by tough carti- lage between the bone and can be classified Abduction Movement away from the as primary (synchondroses) or secondary midline (symphyses). Adduction Movement towards the midline Synchondroses Abduction Synchondroses are cartilaginous joints formed of hyaline cartilage, and are mainly found in the growing skeleton as the ossifi- cation centres of growing bone that will Adduction ossify over time (synostosis), such as the epiphyseal growth plate. Cartilaginous joints are usually immo- Rotation Movement around a longitudinal axis bile but, in a rare condition in children and adolescents, the attachment of the epiph- ysis loosens, allowing the femoral head to slip down the femoral neck. This is known Rotation as a slipped upper femoral epiphysis and often presents with the child developing an unexpected limp (Robson and Synder- Circumduction Movement in a circular combe Court, 2019). motion In the mature skeleton, an example of a synchondrosis is the first sternocostal joint (between the first rib and the manu- brium); all other sternocostal joints are synovial. Circumductioncumduction Symphyses Pronation For example. turning the These are permanent cartilaginous joints, palm of the hand Supination Pronation in which the bones are connected through downwards fibrocartilage; interestingly, these are all at the body’s midline (Robson and Synder- Supination For example, turning the combe Court, 2019). The intervertebral palm of the hand upwards discs between the vertebral bodies of the spine are an example of bones connected by fibrocartilage. These fibrous joints allow Opposition Movement of the thumb relatively limited movement individually across the palm to touch but extensive movement can be achieved the tips of the fingers on Opposition collectively across the whole spine. the same hand Another example of a symphysis is the symphysis pubis in the pelvis, which helps maintain pelvic stability. In pregnancy, the symphysis pubis is softened by hormones Inversion Turning the sole of the to allow for expansion during delivery. foot inwards This, together with the unfused bones of the baby’s skull, allows passage of the Eversion Turning the sole of the baby’s head through the birth canal. foot outwards As symphyses allow slight movement between the articulating surfaces, they are Eversion Inversion FRANCESCA CORRA FRANCESCA considered to be amphiarthroses. Nursing Times [online] March 2020 / Vol 116 Issue 3 53 www.nursingtimes.net Copyright EMAP Publishing 2020 This article is not for distribution except for journal club use Clinical Practice Systems of life Table 2. Types of synovial joint Joint type Description Example Illustration Planar Two flat or slightly curved articulating l Intercarpal joints surfaces that slide against each other, l Intertarsal joints allowing a side-to-side and back-and-forth l Vertebral facets Plane Joint movement Carpals Hinge Typically has convex part of one bone that l Elbow sits inside the concave part of another and l Ankle allows a uni-axial movement, such as flexion l Knee Humerus and extension Hinge joint Radius Ulna Pivot One bone pivots around another to create a l Atlantoaxial joint between rotational movement around a single axis C1 (atlas) and C2 (axis) of the spine Humerus l Radioulnar joint between the radius and the ulnar, Ulna Pivot joint allowing them to pronate Radius and supinate the hand Condyloid An ovoid convex part sits in the ellipsoidal l Radiocarpal joint of the cavity of the other bone, which permits wrist Radius Ulna flexion/extension, abduction/adduction and l Metacarpophalangeal circumduction joints in the hand Lunate Scaphoid Saddle Allows articulation through reciprocal l Carpometacarpal joint of reception as the bones have concave-convex the thumb surfaces that interlock. Permits flexion/ extension, abduction/adduction and circumduction Trapezium First metacarpal Ball and The spheroid structure (ball) sits in the l Glenohumeral socket socket of another bone. This allows multiaxial l Acetabulofemoral (hip) movement and has the greatest range of Acetabulum movement. The depth of the socket and the of hip bone fibrocartilaginous labrum are the limiting Head of factors for motion femur Synovial joints muscles around the joint maintains move- attached to the periosteum, allowing Synovial joints are designed to allow free ment, while stability is maintained movement, maintaining tensile strength movement of the joint and are classified as through the use of soft tissue structures, and helping to prevent dislocation. Inside diarthroses. Characterised by a gap such as ligaments, labra, fat pads and the capsule are sensory nerve fibres, which between the articulating bones, they are menisci (Danning, 2019). detect pain and identify