ANATOMY UNIT 4 (BONES)

Skeletal System

composed of bones and associated ligaments, tendons

Skeletal System Functions

1) support: bones of legs, pelvis, vertebrae support weight of body; mandible supports teeth

2) protection: bones of skull protect the brain; ribs and sternum protect the lungs and the heart; vertebrae protects spinal cord

3) Movement: skeletal muscles use bones as levers to move body

4) Reservoir for minerals and adipose (calcium and phosphorus)

5) Hematopoiesis: blood cell formation; made in red marrow of certain bones

Axial Skeleton

forms long axis of the body; includes bones of skull, vertebral column, and ribcage; involved in protection, support, and carrying other body parts

Appendicular Skeleton

bones of upper and lower limbs and the girdles that attach them to the axial skeleton; involved in locomotion and manipulation of environment

Long Bones

longer than they are wide; all bones of the limbs except for the patella and bones of wrist and ankle; consists of shaft plus 2 expanded ends

Short Bones

roughly cube shaped; bones of the wrist and the ankle

Flat Bones

thin, flattened, and usually a bit curved; scapulae, sternum, ribs, skull

Irregular Bones

have shapes that don’t fit the other types; vertebrae, hip bones, 2 skull bones

Sesamoid Bone

form within tendons; patella

Spine sections

cervical→ thoracic→ lumbar → sacrum → coccyx

Types of Ribs

true ribs → false ribs → floating ribs

Compact Bone

desne, solid outer layer

Spongy Bone

inner layer of honeycomb, needle-like projections

Diaphysis

shaft; thick ring of compact bone surrounding a central medullary cavity

Epiphysis

thin layer of compact bone covering an interior of mostly spongy bone; joint surface of each epiphysis is covered with ARTICULAR CARTILAGE which cushions the bone ends and reduces friction

Periosteum

fibrous connective tissue covering outside of diaphysis; richly supplied with nerve fibers, lymphatic vessels and blood vessels; enter bone via nutrient foramen; connected to the bone matrix via strong strands of collagen

Endosteum

internal bone surfaces are covered with delicate connective tissue membrane called endosteum; barely visible; lines canals

Structure of Short, Irregular, and Flat Bones

thin plates of periosteum-covered compact Bone on the outside and endosteum-covered spongy bone within; no diaphysis nor epiphysis; contain bone marrow within spongy bone (no marrow cavity)

Bone Marrow

soft tissue occupying medullary cavity of long bone and spaces amid trabeculae of spongy bone; red and yellow

Red Marrow

forms blood cells; hematopoietic; in every bone for children; limited to axial skeleton, pectoral girdle, pelvic girdle, and proximal heads of humereus and femur for adults

Yellow Marrow

fat; fills long bones of adults

Bone Formation

embryonic skeleton Is primarily hyaline cartilage; in adults cartilage remains in nose, ribs, joints and others are replaced by bone

Ossification

bone tissue formation; leads to formation of bony skeleton and bone growth and bone remodeling and bone repair

Bone Development Stages

1) cartilage is covered with bone matrix by Osteoblasts (bone forming cells)

2) cartilage is digested, opening a medullary cavity with Osteoclasts (bone digesting cells on the endosteum that widen the medullary cavity)

Epiphyseal Plates

allow for lengthening of long bone during childhood; new cartilage is continuously formed on external sides; older cartilage becomes ossified on internal sides

Epiphyseal Line

signifies bone is done growing

Osteocytes

mature bone cells that no longer secrete matrix; Osteoblasts that have become trapped in matrix; responsible for maintaining the tissue

Remodeling

bones are remodeled in response to changes in blood calcium levels and pull of gravity on muscles on bones

Fracture Repair

1) extensive bleeding occurs and hematoma develops; bone cells die and site swells

2) granulation tissue is formed as hematoma is infiltrated; fibrocartilage callus splints the broken bone

3) Osteoblasts convert fibrocartilaginous callus to bony callus

4) bony callus is remodeled by Osteoclasts and osteoblasts

Open (Compound) Fracture

bone breaks the skin

Closed (simple) Fracture

bone stays in skin

Transverses

straight across, usually result of blow perpendicular to bone

Oblique

curved or at angle to the bone

Communited

bone fragments in 3+ pieces; common in elderly

Greenstick

bone breaks incompletely; one side bent and one side broken; common in children

Spiral

around the bone; caused by excessive twisting forces

Avulsion

bone is broken near tendon/ligament

Impacted

one bone fragments is driven into another

Fibrous Joints

bones tightly connected by fibrous tissue; immovable; ex. sutures of the skull

Cartilaginous Joints

held together by layer/disc of cartilage; slightly movable; ex. ribs to sternum, vertebral disc

Synovial Joints

articular cartilage w/ joint capsule filled w/ synovial fluid to lubricate and cushion joint; freely movable; hinge (least movable) and ball&socket (most movable); also gliding, pivot, condyloid, and saddle

Osteomalacia

literally soft bones; includes many disorders in which bone is produced but inadequately mineralized; caused by insufficient dietary calcium and vitamin D

Rickets

children’s form of osteomalacia; more detrimental due to fact that their bones are still growing; signs include bowed legs, deformities of pelvis, ribs, and skull

Osteoporosis

disease in which bone resorption occurs at a faster rate than bone deposition; bone mass drops and bones become increasingly porous; compression fractures of the vertebrae and fractures of femur; often seen in postmenopausal women b/c they experience rapid decline in estrogen

Gigantism

childhood hypersecretion of growth hormone by the pituitary gland that causes excessive growth

Acromegaly

adulthood hypersecretion of GH causes overgrowth of bony areas still responsive to GH as bones of face, feet, and hands

Pituitary Dwarfism

GH deficiency in children resulting in extremely short long bones and maximums stature of 4 ft

Osteoarthritis

degenerative joint disease where cartilage that covers end of joints deteriorates, causing pain and loss of movement as bone begins to rub against bone; most prevalent form of arthritis

Rheumatoid Arthritis

autoimmune disease where joint lining becomes inflamed as part of immune system activity; one of the most serious and disabling types affecting mostly women; not just for old people

Gout

affects mostly men; result of defect in body chemistry; affects small joints especially the phalanges

Scoliosis

vertebrae curved to the side

Kyphosis

upper vertebrae curved too much outwards towards the back (

Lordosis

lower vertebrae curved inwards too much towards the belly )

Calcitriol synthesis

depends on availability of Vitamin D; necessary to absorb calcium and phosphate in intestine