Unit 5 - Skeletal System

Support

Function of the skeletal system that provides framework for the body by supporting soft tissue and providing points of attachment for skeletal muscles

Protection

Function of the skeletal system that protects many internal organs from injury. Ex. cranium (brain) vertebrae (spinal cord) ribs (heart/lungs)

Assist in Movement

Function of the skeletal system related to contraction of muscles to pull on bones; together muscles and bones produce movement

Storage of Calcium

Function of the skeletal system that, when needed, releases minerals into the blood to maintain homeostasis

Production of Blood Cells

Function of the skeletal system relating to red bone marrow and the production of blood cells. Present in fetal/infant bones and also some adult bones (pelvis, ribs, sternum, skull, ends of arm and leg bones)

Storage of Chemical Energy

Function of the skeletal system relating to yellow bone marrow stores of fat/reserve energy

Red Bone Marrow

Produces RBCs, WBCs, and platelets

Axial Skeleton

Composed of the skull (facial/cranium), vertebral column (sacrum/coccyx), sternum, and ribs

Appendicular Skeleton

Composed of the hands, feet, wrists, ankles, arms, legs, and pectoral/pelvic girdles

Long Bones

Bones with greater length and width, with a long shaft. Ex. Femur, tibia/fibula, humerus, ulna, radius, and phalanges

Short Bones

Bones that are somewhat cube shaped; nearly equal in length and width. Ex. Carpals/tarsals

Flat Bones

Bones that are generally thin; extensive surface for muscle attachment; provides considerable protection. Ex. Cranial bones, sternum, ribs, scapulae

Irregular bones

Bones with complex shapes (don’t fit into other categories). Ex. Vertebrae of backbone; some facial bones

Sesamoid Bone

Bones that protect tendons from wear and tear. Ex. Patella

Diaphysis

Long, cylindrical, main portion of the bone

Epiphysis

Distal and proximal ends of the bone

Metaphysis

Regions in mature bone where epiphysis meets the diaphysis, in growing bone includes the epiphyseal plate

Epiphyseal Plate

Layer of cartilage that is being replaced by bone; bone grows in length

Epiphyseal Line

Line created when growth stops, cartilage is replaced by bone

Articular Cartilage

Reduces friction/absorbs shock

Spongy Bone

Contains red marrow; found in hip bones, ribs, breast bones, vertebrae, and the ends of long bones; irregular, criss-crossing of thin columns of bone (trabeculae). Spaces within the spongy bone is filled with red bone marrow

Compact Bone

Contains few spaces, external layer of all bones of the body and the bulk of the body of long bones, provides protection/support/resistance to stress

Marrow Cavity

Space within the diaphysis which contains fatty yellow marrow in adults

Periosteum

Tough sheath of dense irregular connective tissue; surrounds the bone surface. Protects. Assists in fracture repair, helps nourish bone, serves as a point of attachment for ligaments/tendons

Endosteum

Lines the surface of marrow cavity, contains bone forming cells that contribute to growth in width of the bone

Hardness

Depends on crystallized inorganic mineral salts

Flexibility

Depends on collagen fibers

Matrix

Intracellular materials. 25% water, 25% protein fibers, 50% crystallized mineral salts

Osteogenic Cells

Unspecialized stem cells which divide into cells that develop into osteoblasts. Found along the inner portion of the periosteum, the endosteum, and the canals within bone containing blood cells

Osteoblasts

Immature bone building cells, do not divide. Synthesize and secrete collagen, found on the surface of the bone, as they secrete matrix materials they become trapped in their secretions and become osteocytes

Osteocytes

Mature. Principally cells of bone tissues. No longer secrete matrix materials, maintain cellular activities of bone tissues such as exchange of nutrients and wastes with blood

Osteoclasts

Huge cells found in bone which release powerful lysosomal enzymes that function in the destruction of bone matrix (resorption)

Resorption

Part of the normal development, growth, maintenance, and repair of bone

Volkmann’s Canals

Locations where blood/lymph vessels and nerves from periosteum penetrate transversely the width of bones

Central (Haversian) Canals

Extend Vertically, lengthwise through the bone

Concentric Lamellae

Rings of hard calcified matrix surrounding central canals

Lacunae

Small spaces between lamellae that contain osteocytes

Canaliculi

Tiny channels that projects in all directions from the lacunae. Provide routes for nutrients and oxygen to reach the osteocytes and wastes to be removed

Osteon (Haversian System)

A central canal with its surrounding lamellae, lacunae, and canaliculi

Trabeculae

Irregular latticework of thin columns of bone

Bone Resorption

Ongoing replacement of old bone tissue with new. Removes worn and injured bone

Ossification

Osteoblasts building new bone tissue

Less Bone Density

Resorption > Ossification, weak, fragile, thin bones

Greater Bone Density

Resorption < Ossification, excess bony deposits (bone spurs)

Compound Fracture

Ends of bones protruding from skin

Comminuted Fracture

Bone splinters/fragments between two main fragments

Greenstick Fracture

Partial fracture; one side breaks and the other bends. Occurs only in children whose bones are not fully ossified

Spiral Fracture

A bone breaks in half by a twisting force or impact

Transverse Fracture

Breaks straight across the bone

Oblique Fracture

Bone is broken at an angle

Displaced Fracture

Bone breaks, moves out of alignment

Nondisplaced Fracture

Bone breaks, does not move out of alignment

Closed Fracture

Skin is not broken when bone breaks

Stress Fracture

A very thin crack, also called a hairline fracture

Fracture Hematoma

First step of bone repair, blood vessels at the site of the fracture form a clot. Capillaries grow into area and WBCs and osteoclasts remove dead or damaged tissue (several weeks)

Procallus Forms (Soft Callus)

Second step of bone repair, actively growing connective tissue/collagen fibers secreted. Becomes a mass of repair tissue that bridges the broken ends of the bone (~3 weeks)

Bony Callus Forms

Third step of bone repair, osteoblasts develop and produce spongy bone trabeculae. Eventually the tissue at the fracture is completely converted into spongy bone (3-4 months)

Bone Remodeling

Fourth step of bone repair, compact bone replaces spongy bone at the periphery. Osteoclasts gradually resorb dead fragment of original broken bone

Fibrous/Immovable/Synarthrosis

Joint with bones held together by fibrous connective tissue rich in collagen; no synovial cavity. Ex. sutures between plates of the cranium, teeth within sockets of skull

Cartilaginous/Semi-Movable/Amphiarthrosis

Joints that lack synovial cavity, little movement. Ex. Pubic symphysis, intervertebral discs, ribs to sternum

Synovial/Freely Movable/Diarthrosis

Joints that have space called the synovial cavity between articulating bones

Ligaments

Tough bands of connective tissue that attach bone to bone

Tendons

Tough bands of connective tissue that connects muscle to bone

Synovial Fluid

Secreted by cells in the synovial membrane. Reduces friction/lubricates

Bursa

Saclike structures found near joints and other points of friction (where a tendon crosses a bone)

Meniscus (articular discs)

Pads of fibrocartilage (cartilage that contains numerous thick bundles of collagen fibers) that lie between the articular surfaces of bone

Articular Capsule

A fibrous tissue envelope surrounding a synovial joint

Hinge Joint

Angular, open-closing motion. Ex. Knee, elbow

Pivot Joint

“Peg in a hole”; allows rotation around a central axis. Ex. atlantoaxial joint

Planar Joints

2 opposed flat surfaces that glide over each other; side to side and back and forth gliding. Ex. articular facets of the vertebrae; intercarpal and intertarsal joints

Ball and Socket Joint

Ball-like surface of one bone fits into the cup-like depression of another bone; wide range of motion. Ex. hip or shoulder joint

Strain

Damage to muscle/tendon

Sprain

Twisting/wrenching of a joint that stretches or tears its ligaments but does not dislocate the bone. May damage blood vessels, muscles, tendons, and nerves. Considerable swelling

Dislocation

Displacement of a bone from a joint with tearing of ligaments, tendons, and articular capsule. Intense pain, joint instability, reduced muscle strength, difficulty moving joint/stiffness

Hyperextension

The movement of a joint beyond it’s normal, healthy range of motion

Subluxation

Partial dislocation

Avulsion

Detaching fragment of bone

Male Pelvis

Pelvis that is more vertical/less flared spread, larger and rounder obturator foramen, less than 90 degrees/acute angle across pubic symphysis, smaller inner diameter of pelvic inlet

Female Pelvis

Pelvis that has a more flared spread, smaller/triangular obturator foramen, greater than 90 degrees/obtuse angle across pubic symphysis, larger pelvic inlet; room for head of baby

Male Skull

Skull that is larger; heavier appearance, pronounced muscle attachment points, ovale/smaller eye orbits, heavy/pronounced brow ridge, U-shaped/broad chin, angular jawline shape (profile)

Female Skull

Small, light appearance, rounded/larger eye orbit shape, smooth/flat brow ridge, V-shaped/narrow chin, rounded jawline shape

Factors of Bone Metabolism

Adequate Minerals (calcium and phosphorus), Vitamins A, C, and D, Hormonal Levels (females = estrogen, males = testosterone), weight bearing exercise

Young Children

Stage of life where building strong bones is important, bone mass peaks in third decade of life, bones continually grow both in length and diameter, cartilage in Ossification center is slowly converted to bone

Puberty

Stage of life where Estrogen and Androgens begin being secreted in larger quantities, cause growth spurt, widening of pelvis in females, cartilage in ossification centers at ends of long bone has been completely converted to bone, epiphyseal line replaces epiphyseal plate

Old Age

Stage of life with decreased collagen production (bones more brittle, less flexible), reduction of weight bearing exercises, less active, reduced production of specific hormones

Osteoporosis

Condition of porous bones; bone resorption outpaces remodeling/deposition. Bone mass depleted, cannot withstand mechanical stresses of daily life. Easily fracture (hip, wrist, vertebrae), shrinkage of vertebrae/height loss; hunched back. Middle age/elderly, 80% women - estrogen drop from menopause

Testosterone

Wanes only slightly in men as they age (less dramatic drop than in estrogen production as a result of menopause)

Treatments for Osteoporosis

Calcium supplements, weight- bearing exercises, drugs that mimic the beneficial effects of estrogen (promote bone growth)

Remodeling

The process by which old bone is continually destroyed and replaced by new bone