A&P: Bones

Sex Hormones

estrogen & testosterone, secreted in large amounts in puberty which dramatically accelerates bone growth

Ossification (osteogenesis)

*either endochondral or intramembraneous* formation/development of bone CT; begins in embryo

Epiphyseal Plate

*in the metaphysis* a growth plate composed of hyaline cartilage, provides lengthwise bone growth; turns into epiphyseal line in adults

Phosphate

ATP utilization and plasma membrane

Central Canal

Cylindrical channel at center of osteon and parallel to it; blood vessels and nerves extend through channel

Hemopoiesis

blood cell production, occurs in red bone marrow connective tissue,and stem cells form blood cells and platelets

Appositional Growth

bone growth in diameter or thickness; occurs within periosteum

Interstitial Growth

bone growth in length

Parallel Lamellae

bone matrix, osteocytes between lamellae, canaliculi radiate from lacunae

Skeletal System

bones of skeleton, cartilage, ligaments, connective tissue

Storage of Minerals and Energy Reserves

bones store body's reserve of calcium and phosphate (released as needed); lipids stored in yellow bone marrow of adult bones

Interstitial Lamellae

components of compact bone between osteons; are incomplete and have no central canal

Bone Matrix

composed of organic and inorganic components

Compact Bone

comprised of small cylindrical structures (osteons); oriented parallel to bone diaphysis

Articular Cartilage

covers joint surface, thin layer of hyaline cartilage,reduces friction, and absorbs shock in moveable joints

Irregular Bones

do not fit any other category (Ex: vertebrae, hip bones, some facial bones)

Diaphysis

elongated, cylindrical shaft; provides leverage and weight support; compact bone with thin spicules of spongy bone extending inward

Proximal Epiphysis

end of bone closet to appendage joint

Distal Epiphysis

end of bone farthest from appendage joint

Calcium

essential for muscle contraction, blood clotting, and nerve impulse transmission

Flat Bones

flat, thin surfaces (may be curved slightly), provide surfaces for muscle attachment (Ex: roof of skull, sternum, ribs, scapula)

Long Bones

greater in length than width; elongated with cylindrical shaft (diaphysis); found in upper and lower limbs;most common bone shape (Ex: humerus, femur, tibia)

Glucocorticoids

group of steroid hormones; released from adrenal cortex; regulates blood glucose level; high amounts increases bone loss

Medullary Cavity

hollow, cylindrical space within diaphysis; contains red marrow in children & yellow marrow in adults

Epiphysis

knobby region at each end of long bone; composed of outer thin layer of compact none (inner region of spongy bone); covered by articular cartilage

Short Bones

length nearly equal to width (Ex: carpals, tarsals, sesamoid bones, patella)

Osteocytes

mature bone cells; found in lacunae; maintain bone matrix

Mechanical Stress

occurs during weight-bearing movement/exercise; required for normal bone remodeling; causes an increase in synthesis of osteoid; causes increase in bone strength

Trabeculae

open lattice of narrow rods and plates of bones; bone marrow fills spaces; resistance to stresses

Organic Components of Bone Matrix

osteoid produced by osteoblasts (contains collagen protein & semi-solid ground substance); gives bone tensile strength by resisting stretching and contributes to bone flexibility

Growth Hormone (somatotropin)

produced by anterior pituitary gland; stimulates live to produce hormone-somatomedin (both stimulate cartilage growth in epiphyseal plate)

Metaphysis

region of mature bone between diaphysis and epiphysis

Perforating Canals (Volkmann)

resemble central canal, blood vessels and nerves travel through; perpendicular to central canals; connect central canals within different osteons

Concentric Lamellae

rings of bone CT; surround central canal; collagen fibers give bone strength and resilience

Circumferential Lamellae

rings of bone;either internal or external and both run the entire circumference of the bone

Inorganic Components of Bone Matrix

salt crystals, calcium phosphate, sodium, magnesium, sulfate - all interact with calcium hydroxide to form hydroxyapatite salt crystals; harden bone matrix and rigidity

Thyroid Hormone

secreted by thyroid gland; influences basal metabolic rate of bone cells; regulates normal activity at epiphyseal plates

Classes of Bones

short bones, long bones, irregular bones, & flat bones

Function of Bones

support/protection, movement, hemopoiesis, storage of mineral/energy reserves

Canaliculi

tiny,interconnecting channels within bone CT, extend from each lacuna, travel through lamellae and connect to lacunae and central canal; house osteocyte projections that allow intercellular contact; allow exchange of nutrients, minerals, gases, and wastes between blood vessels and osteocytes

Spongy Bone

trabeculae & parallel lamellae