Introduction to the Locomotor Apparatus PDF

Introduction to the Locomotor Apparatus W. Brady Little, DVM, MSC LO: 3-11 (Module 1) Resources listed in Canvas, same module OVERVIEW 1. 2. 3. Osteology Bones & regions - forelimb Types of bones according to shape Long bones anatomy Bony prominences Arthrology Classify joints by structure Anatomy o...

Introduction to the Locomotor Apparatus W. Brady Little, DVM, MSC LO: 3-11 (Module 1) Resources listed in Canvas, same module OVERVIEW 1. 2. 3. Osteology Bones & regions - forelimb Types of bones according to shape Long bones anatomy Bony prominences Arthrology Classify joints by structure Anatomy of synovial joints Joints classified by function Basic movements Myology Anatomy of skeletal muscles 1. Osteology “osteo-” (bone) + “-ology” (study of) = The study of bones. Primary Functions of Bones 1. 2. 3. 4. Support the weight of the body Movement in concert with joints and muscles Protection of internal organs Growth 5. 6. 7. Storage of minerals (e.g.: Ca2+ and P+) Storage of fat → marrow Blood cell formation (hematopoiesis) → marrow Forelimb Region and Bones (that support them) Scapular region -> Scapula Brachium -> Humerus Antebrachium -> Radius and Ulna Manus = Front paw, includes: Carpus -> carpal bones Metacarpus -> metacarpal bones Digits -> Phalanges & sesamoids Types of bones according to their shape: Flat bone: scapula Long bones: humerus, radius, ulna Short bones: carpal bones Sesamoids = special type of short bones within tendons Irregular bones: vertebrae Sesamoid bones Sesamoid bones are found in the tendons of origin or insertion of certain muscles or in a muscle. They can develop as a response to strain or as a normal occurrence. Functions of Sesamoid bones: ❑ Provide a smooth surface for tendons to slide over, preventing friction of the associated tendo. ❑ They act as a fulcrum providing extra leverage to the muscle, enhancing the tendon's ability to transmit muscular forces. ❑ Their can displace the axis of force by altering the direction of tension in the muscle tendon. Long bones – gross anatomy At least 3 centers of ossification Diaphysis = bone shaft → medullary cavity (contains yellow marrow) (growth plate) Epiphysis = end regions of bone Physeal growth plate: located between epiphyses and diaphysis in young animals; comprised of cartilage cells https://slideplayer.com/slide/4284187/14/images/4/Figure+5.3a+ The+structure+of+a+long+bone+%28humerus+of+arm%29..jpg Long bones - Growth plate relevance Primary site for fractures, infections, metastasis, and effects of endocrine bone disorders. Growth plate fracture NORMAL Dog, 8 months old, hindlimb Bony prominences Bones get remodeled in response to stress placed upon them (Wolf’s law = form follows function). Non-articular prominences: attachment sites for muscles; passages of vessels and nerves, etc. (e.g.: spine of the scapula, supraspinous & infraspinous fossae) Scapula, lateral view Articular prominences: make up joints (e.g.: glenoid cavity) Scapula, distal view 2. Arthrology “Arthro-” (joint) + “-ology” (study of) = the study of joints. A joint is the point of contact, or articulation, between two or more bones/cartilages. Provides support and movement to the skeleton (Not all joints are moveable!) Structural classification of joints 1. Fibrous joints – Strong connective tissue unites articular surfaces of bones – Bones can even fuse (synostosis) => Limited movement or no movement 2. Cartilaginous joints – Cartilage unites articular surfaces of bones => limited movement 3. Synovial joints – Joint cavity between articular surfaces of bones filled with synovial fluid => full movement Intervertebral disc In human spine Anatomy of a synovial joint Articular surfaces: protected by articular cartilage enclosed within a fluid-filled joint cavity Joint capsule: - produces synovial fluid - highly vascularized and innervated - provides strength and resistance - for lubrication and nutrition of the articular cartilages NOTE: a joint may have multiple synovial compartments/ sacs within a single joint capsule Accessory structures of synovial joints Ligaments (lig.) = bands of tough fibrous connective tissue Extracapsular (e.g.: collateral ligaments of elbow joint) Intracapsular (e.g.: cruciate ligaments of knee joint) Meniscus (pl. menisci) = fibrocartilages located within a synovial cavity; allow articular surfaces to fit together. Femur Humerus Caudal cruciate ligament Medial meniscus Radius Ulna Lateral view of elbow joint Tibia Fibula view of knee joint Basic synovial joint movements Gliding / Sliding of two surfaces on each other Angular motions: – Flexion: decreasing angle between limb segments vs – Extension: increasing angle between limb segments Basic synovial joint movements Angular motion (continued): – Abduction (1): moving away from median plane vs – Adduction (2): moving towards median plane 1 2 Basic synovial joint movements Angular motion (continued): – Circumduction: movement circumscribing a cone shape – Medial/Lateral Rotation: “rolling pin movement on the axis of limb – Pronation vs. supination of forearm (antebrachium) Consistent pronation Left radius ulna, dog in domestic animals) Synovial joint classifications By number of articulating bones: Simple (between 2 bones): glenohumeral (shoulder) joint, etc. Compound (more than 2 bones): humeroradioulnar (elbow) joint, carpal joint, etc. By how well the bones fit together: Congruent (articular surfaces fit well together): humeroradioulnar (elbow) joint Incongruent (articular surfaces do not fit well together): knee joint, seen in 2nd semester By shape & permitted motions around the joint – several types: Hinge – least versatile, flexion and extension only (elbow joint) Spheroidal (ball & socket) – most versatile, all range of movements (shoulder joint, hip joint) Others: condylar, ellipsoidal, etc. Myology “myo” – Greek term for “muscle” myo + ology = study of muscle(s) Locomotor System (Apparatus) = bones + joints (PASSIVE components) + muscles (ACTIVE component) Importance: lameness can be caused by muscle/tendon damage, not just bone or joint pathology 18 Skeletal muscles attach to bones via tendons. PROXIMAL Tendon of origin (proximal attachment) – Usually fixed point Muscle head or belly – the part that contracts Tendon of insertion (distal attachment) – Usually point moved by muscle contraction Canine forearm Lateral view DISTAL Aponeurosis: – A flat, sheet-like tendon; allows muscle to have a broader attachment Accessory Structures of Muscles Synovial bursa (“bursa” = pouch) Synovial fluid-filled “balloon” protecting a tendon from a bony surface. Tendon Retinaculum – Fibrous band holding down tendon(s) to a bone Bone Synovial tendon sheath: Synovial fluid-filled “sleeve” completely surrounding a tendon (like a sock) easing its gliding between a retinaculum and bone Ligament vs Tendon vs Retinaculum – Ligaments attach bone to bone (usually part of a joint) – Sometimes tendon to bone – Tendons attach muscle to bone (or to another tissue surface) – Retinacula (pl.) are bands holding down tendon(s) of muscles close to the surface of a bone. Retinaculum singular 26 Fasciae / fascial planes Fasciae (pl.) are fibrous leaves enveloping and isolating muscle groups and individual muscles Superficial fascia = loose connective tissue attaching skin to underlying mm. Deep fascia = leaf of dense connective tissue from which some muscles may originate or insert; separates muscle groups/layers into fascial planes Superficial fascia Cranial (head) Deep fascia (thoracolumbar fascia) Dorsum (back) of dog Caudal (tail) Use muscle names to your advantage! Shape: trapezius m. = Size: latissimus dorsi m. = “the widest m. of the back” Relative position: superficial, middle, and deep gluteal mm. Origin and insertion: sternocephalicus m. =“sternum to head” muscle Function: extensor carpi radialis m. = “radial extensor of the carpus m.” Structure: triceps brachii m. = “three headed m. of the arm” 24