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Download Chapter 6: Skeletal System
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Classification of Bones Axial skeleton – bones of the skull, vertebral column, & rib cage Appendicular skeleton – bones of the upper and lower limbs, shoulder, & hip Bones contain several tissues – bone tissue, nervous tissue, cartilage, blood, epithelium around vessels Classification of Bones: By Shape Long bones – longer than they are wide (humerus, femur, radius, ulna, tibia, fibula, fingers, & toes) Short bones – cube-shaped bones of the wrist & ankle Bones that form within tendons (patella) Flat bones – thin, flattened, and a bit curved (sternum, scapula, ribs, & most skull bones) Irregular bones – bones with complicated shapes (vertebrae & hip bones) Function of Bones Support – form the framework that supports the body and cradles soft organs Protection – provide a protective case for the brain, spinal cord, and vital organs Movement – provide levers for muscles Function of Bones Mineral storage – reservoir for minerals, especially calcium & phosphorus release into blood with needed Blood cell formation – hematopoiesis occurs within the marrow cavities in bones Red marrow – make blood cells Yellow marrow – store fat Bone Markings Bulges, depressions, and holes that serve as Sites of attachment for muscles, ligaments, and tendons Joint surfaces Conduits for blood vessels and nerves Bone Markings: ProjectionsSites of Muscle & Ligament Attachment Tuberosity – rounded projection Crest – narrow, prominent ridge of bone Trochanter – large, blunt, irregular surface Line – narrow ridge of bone Bone Markings: Projections – Sites of Muscle & Ligament Attachment Tubercle – small rounded projection Epicondyle – raised area above a condyle Spine – sharp, slender projection Process – any bony promenence Bone Markings: Projections – Projections That Help to Form Joints Head – bony expansion carried on a narrow neck Facet – smooth, nearly flat articular surface Condyle – rounded articular projection Ramus – arm-like bar of bone Bone Markings: Depressions & Openings Meatus – canal-like passageway Sinus – cavity within a bone Fossa – shallow, basin-like depression Groove – furrow Fissure – narrow, slit-like opening Foramen – round or oval opening through a bone Gross Anatomy of Bones: Bone Texture Compact bone – dense outer layer Spongy bone – honeycomb of trabecular filled with yellow bone marrow Structure of Long Bone Long bones consist of a diaphysis and an epiphysis Diaphysis Tubular shaft that forms the axis of long bones Composed of compact bone that surrounds the medullary cavity Yellow bone marrow (fat) is contained in the medullary cavity Structure of Long Bone Epiphyses Expanded ends of long bones Exterior is compact bone, and the interior is spongy bone Joint surface is covered with articular (hyaline) cartilage Epiphyseal line separates the diaphysis from the epiphyses Structure of Short, Irregular, & Flat Bones Thin plates of periosteum-covered compact bone on the outside with endosteum-covered spongy bone on the inside Have no diaphysis or epiphysis Contain bone marrow between the traveculae No medullary cavity Response to Mechanical Stress Wolff’s law – a bone grows or remodels in response to the forces or demands placed upon it Observations supporting Wolff’s law include: Long bones are thickest midway along the diaphysis (where bending stress in the greatest) Curved bones are thickest where they are most likely to buckle Response to Mechanical Stress Trabeculae form along lines of stress Large, bony projections occur where heavy, active muscles attach Bone Fractures (Breaks) Bone fractures are classified by: The position of the bone ends after fracture The completeness of the break The orientation of the bone to the long axis Whether or not the bone ends penetrate the skin Types of Bone Fractures Nondisplaced – bone ends retain their normal position Displaced – bone ends are out of normal alignment Types of Bone Fractures Complete – bone is broken all the way through Incomplete – bone is not broken all the way through Linear – the fracture is parallel to the long axis of the bone Types of Bone Fractures Transverse – the fracture is perpendicular to the long axis of the bone Compound (open) – bone ends penetrate the skin Simple (closed) – Bone ends do not penetrate the skin Common Types of Fractures Comminuted – bone fragments into three or more pieces ( common in the elderly) Spiral – ragged break when bone is excessively twisted (common sports injury) Depressed – broken bone portion pressed inward (typical skull fracture) Common Types of Fractures Compression – bone is crushed (common in porous bones) Epiphyseal – epiphysis separates from diaphysis along epiphyseal line; can hinder growth (occurs where cartilage cells are dying) Greenstick – incomplete fracture where one side of the bone breaks and the other side bends (common in children) Comminuted Fracture Spiral Fracture Depressed Fracture Compression Fracture Epiphyseal Fracture Greenstick Fracture Stages in the Healing of a Bone Fracture Hematoma formation: Torn blood vessels hemorrhage A mass of clotted blood (hematoma) forms at the fracture site Site becomes swollen, painful, and inflamed Stages in the Healing of a Bone Fracture Fibrocartilaginous callus forms Granulation tissue (soft callus) forms a few days after the fracture Capillaries grow into the tissue and phagocytic cells begin cleaning debris Stages in the Healing of a Bone Fracture The fibrocartilaginous callus forms when: Osteoblasts and fibroblasts migrate to the fracture and begin reconstructing the bone Fibroblasts secrete collagen fibers that connect broken bone ends Osteoblasts begin forming spongy bone Osteoblasts furthest from capillaries secrete an externally bulging cartilaginous matrix that later calcifies Stages in the Healing of a Bone Fracture Bony callus formation: New bone trabeculae appear in the fibrocartilaginous callus Fibrocartilaginous callus coverts into a bony (hard) callus Bone callus begins 3-4 weeks after injury & continues until firm union is formed 2-3 months later Stages in the Healing of a Bone Fracture Bone remodeling: Excess material on the bone shaft exterior and in the medullary canal is removed Compact bone is laid down to reconstruct shaft walls Stages in the Healing of a Bone Fracture Joints Weakest parts of the skeleton Articulation – site where two or more bones meet Functions of joints Give the skeleton mobility Hold the skeleton together Joints A joint is a junction between bones Joints have differences in degree of motion Immovable Slightly movable Freely movable More commonly classified by their structure or the material that binds the joints together: Fibrous joints Cartilaginous joints Synovial joints Fibrous Joints Lie between bones that closely contact one another There is no joint cavity Thin layer of dense connective tissue joins the bones at such joints Most are immovable some can move slightly There are 3 types: Sutures – occur between the bones of the skull Syndesmoses – connection between the distal end of the tibia & fibula and radius & ulna Gomphoses – peg-in-socket fibrous joint between a tooth and its alveolar socket Cartilaginous Joints Articulating bones are united by cartilage Lack a joint cavity Two types: Synchondroses Bar or plate of hyaline cartilage unties the bones Immovable Ex) joint between first rib and the sternum Symphyses Hyaline cartilage covers the articulating surface of the bone Joint is designed for strength and flexibility Ex) intervertebral joints & pubic symphysis of the pelvis Synovial Joints Those joints in which the articulating bones are separated by a fluid-containing joint cavity All are freely movable diarthroses Ex) all limb joints & most joints of the body Synovial joints all have the following: Articular cartilage Joint (synovial) cavity Articular capsule Synovial fluid Reinforcing ligaments Types of Synovial Joints Ball-and-socket joints Consists of a bone w/ a ball-shaped head than articulates with a cup-shaped cavity of another bone Allows the widest range of motion that any other joint Ex) shoulder & hip Types of Synovial Joints Condyloid joints Oval-shaped condyle of one bone fits into an elliptical cavity of another bone This joint allows for flexion, extension, adduction, abduction, & circumduction movements Ex) Joints between the metacarpals and phalanges Types of Synovial Joints Gliding joints Articulating surfaces are nearly flat or slightly curved Allow sliding and twisting movements Ex) Joints in the wrist, ankle, and between the articular processes of adjacent vertebrae Types of Synovial Joints Hinge joints Convex surface of one bone fits into the concave surface of another Resembles the hinge of a door Ex) Elbow, knee, joints of the phalanges Types of Synovial Joints Pivot joints Cylindrical surface of one bone rotates within a ring formed of bone and ligament Movement is limited to the rotation around a central axis Ex) joint between the proximal ends of the radius and the ulna Types of Synovial Joints Saddle joints Forms between bones whose articulating surfaces have both concave and convex regions Surface of one bone fits the complementary surface of the other Permits a variety of movements Ex) joint between the trapezium and the metacarpal of the thumb Types of Joint Movements Flexion – bending parts at a joint so that the angle decreases at the joint Extension – straightening parts at a joint so that the angle of the joint increases Dorsiflexion – bending the foot at the ankle toward the shin Plantar flexion – bending the foot at the ankle toward the sole Hyperextension – excess extension of the parts at a joint beyond the anatomical position Types of Joint Movements Abduction – moving a part away from the midline Adduction – moving a part toward the midline Rotation – moving a part around an axis Circumduction – moving a part so that its end follows a circular path Types of Joint Movement Pronation – turning the hand so that the palm is downward or turning the foot so that the medial margin is lowered Supination – turning the hand so that the palm is upward or turning the foot so that the medial margin is raised Eversion – turning the foot so that the sole is outward Inversion – turning the foot so that the sole is inward Retraction – moving a part backward Protraction – moving a part forward Elevation – raising a part Depression – lowering a part
