The Skeletal System

Bones, Skeleton, & Joints

Unit Objectives

Identify the subdivisions of the skeleton as axial or appendicular Axial

On a skull or diagram, identify & name the bones of the skull Describe how the skull of a newborn infant differs from that of an adult, and explain the function of fontanels Name the various parts of a typical vertebra Discuss the importance of the intervertebral discs and spinal curvatures Explain how the abnormal spinal curvatures (scoliosis, lordosis, and kyphosis) differ from one another

Appendicular Identify on a skeleton or diagram the bones of the shoulder and pelvic girdles and their attached limbs Describe important differences between a male and female pelvis

List at least 3 functions of the skeletal system Name the four main kinds of bones Identify the major anatomical areas of a long bone Explain the role of bone salts and the organic matrix in making bone both hard & flexible Describe briefly the process of bone formation in the fetus and summarize the events of bone

remodeling Name & Describe the various types of fractures Name the 3 major categories of joints and compare the amount of movement allowed by each Understand the functions and differences between tendons & ligaments Identify some of the causes of bone and joint problems throughout life

Functions of Bone

Support & Give shape to the body Protects Internal Organs Helps make movements possible Stores calcium Hemopoiesis or blood cell formation

Types of Bones

Long Short Flat Irregular

Structure of Long Bones

Diaphysis or shaft Medullary cavity containing yellow marrow Epiphyses or ends of the bone; spongy bone

contains red bone marrow Articular cartilage-covers epiphyses as a

cushion Periosteum-strong membrane covering bone

except at joint surfaces Endostuem-lines the medullary cavity

Microscopic Structure of Bone and Cartilage

Bone types Spongy

Texture results from needlelike threads of bone called trabeculae surrounded by a network of open spaces

Found in epiphyses of bones Spaces contain red bone marrow

Compact Structural unit is Haversian system-composed of

concentric lamella, lacunae containing osteocytes, and canaliculi, all covered by periosteum

Haversian System

Lamella

Osteocyte in lacuna

Microscopic Structure of Bone and Cartilage con’t

Cartilage Cell type called chondrocyte Matrix is gel-like and lacks blood vessels

Bone formation & Growth

Sequence of development early-cartilage models replaced by calcified bone matirx The laying down of calcium salts in the gel-like

matrix of the forming bones is an ongoing process

Osteoblasts form new bone, osteoclasts reabsorb bone

Development of Bone from Fetus

An infant’s skeleton has many bones that are not yet completely ossified “formed in cartilage”

Fontanels: soft spots on an infant’s skull Long bone grows from small centers at both

ends called epiphyses As long as cartilage remains in epiphyseal plate

body will grow

Division of Skeleton

The skeleton is composed of the following divisions & subdivisions

Axial Skeleton Skull Spine Thorax Hyoid bone

Appendicular Skeleton Upper Extremities, including shoulder girdle Lower Extremities, including hip girdle

Differences between a Man’s & a Woman’s skeleton

Size: Male skeleton is generally larger Shape of pelvis: male pelvis is deep and

narrow, female pelvis is broad and shallow Size of pelvic inlet: female pelvis inlet is

generally wider, normally large enough for baby’s head to pass through it

Pubic angle: angle between pubic bones of female generally wider

Joint (Articulations)

Kinds of joints Synarthroses (no movement)-fibrous connective tissue

grows between articulating bones, for example, sutures of skull

Amphiarthroses (slight movement)-cartilage connects articulating bones; for example symphysis pubis

Diarthroses (free movement)-most joints belong to this class

Structures of freely movable joints-joint capsule and ligaments hold adjoining bones together but permit movement at joint

Joints con’t

Articular cartilage-covers joint ends of bones and absorbs joints

Synovial membrane-lines joint capsule and secretes lubricating fluid

Joint cavity-space between joint ends of bones

Types of freely movable joints

Ball-and-Socket Hinge Pivot Saddle Gliding Condyloid

Bone Remodeling & Repair

Remodeling: balance of bone deposit & removal, deposits occur at a greater rate when bone is injured

Controlled by Hormone used to maintain blood calcium In response to mechanical stress and gravity,

remodels so it is able to withstand the stresses

Bone Remodeling & Repair con’t

Repair Fractures are breaks in bones & are classified

by: Comminuted: bone fragments into 3 or more pieces (common with more

brittle bones) Compression: bone is crushed (common with more brittle bones) Spiral: Ragged break occurs when excessive twisting force is applied to

bone (common sports fracture) Epiphyseal: epiphysis separates from the diaphysis along the

epiphyseal plate (common where cartilage is dying) Depressed: Broken bone portion is pressed inward (common of skull) Greenstick: bone breaks incompletely (common in children whose

bones are more flexible)

http://www.itim.nsw.gov.au/images/Depressed_Skull_Fracture.jpg

Bone Remodeling & Repair con’t

Repair 4 stages Hematoma formation Fibrocartilaginous callus formation Bony callus formation Remodeling of the bony callus

Bone & Joint Problems

Bone Problems Osteomalacia: number of disorders in adults in

which the bone is inadequately mineralized Rickets: inadequate mineralization of bones in

children caused by insufficient calcium or vitamin D deficiency

Osteoporosis: group of disorders in which the rate of bone reabsorption exceeds the rate of formation

Bone & Joint Problems

Joint Problems Sprains Dislocations Bursitis: inflammation of bursa, caused by a

blow or friction Tendonitis: inflammation of the tendons, caused

by overuse Arthritis: inflammatory or degenerative diseases

that damage the joints, resulting in pain, stiffness, and swelling of joint

Spinal Curvatures

5 major divisions; cervical (7), thoracic (12), lumbar (5), fused of sacrum (5), fused of coccyx (4)

Increase resiliency & flexibility Cervical & lumbar curvatures are concave

posteriorly, and the thoracic & sacral curvatures are convex posteriorly

Intervertebral disc

Cushion like pads that act as shock absorbers and allow the spine to flex, extend, and bend laterally

Abnormal Spinal Curvatures

Scoliosis: spine is curved from side to side Lordosis: spine lumbar region is curved

inward Kyphosis: curving of the spine causes a

bowing of the back