Chapter 7 - Bone Tissue

Major steps involved in the process of endochondral ossification

1 Early hyaline cartilage 2 Formation of primary ossification center, bony collar, and periosteum 3 Vascular invasion, formation of primary marrow cavity, & appearance of 2nd ossification center 4 Bone at birth, with enlarged primary marrow cavity and appearance of secondary marrow cavity in one epiphysis (both epiphyses in long bone) 5 Bone of child, with epiphyseal plate at distal end 6 Adult bone with a single marrow cavity and closed epiphyseal plate

Which hormones (several discussed) affect bone growth and health

1 Growth hormone—cartilage cell division, growth in epiphyseal plate 2 Thyroid hormones—enhances and controls GH, stimulates osteoblasts 3 Sex hormones (estrogen and testosterone)—stimulates osteoblasts, bone growth; also feminize or masculinize the skeleton 4 Calcitriol (vitamin D)—increases blood calcium levels; adequate calcium levels are necessary for bone deposition 5 Parathyroid hormone—increases blood calcium 6 Calcitonin—decreases blood calcium 7 Insulin—stimulates bone formation

How nutrients (several specific ones) affect bone growth and health

1 Vitamin A—bone cells and osteoid production 2 Vitamin C—Keeps bones from becoming weak and brittle 3 Vitamin D (calcitriol)—calcium absorption 4 Minerals 5 Protein

Functions and general locations of the cartilages of the skeleton

-Functions: Flexibility, shock absorption, friction reduction -General Locations: Hyaline—airways, articular, costal Elastic—external ear, epiglottis Fibrocartilage—intervertebral discs, knee joint, pubic symphysis

Composition of bone

1.) Non-living Matrix a) Inorganic component of mineral salts—about two thirds b) Organic component of proteins like collagen, proteoglycans, glycoproteins—about one third (produced by cells) 2.) Cells

Explain how the rates of bone deposition and resorption influence bone homeostasis

A balance between factors affecting bone deposition and factors affecting bone resorption are important for homeostasis. During bone resorption, bone cells break down bone tissue and release calcium and other minerals into body To build up bone tissue and maintain homeostasis, bone cells deposit minerals obtained from the bloodstream

Achondroplasia

A genetic disease in which chondrocytes in the epiphyseal plates fail to grow normally

How exercise and lifestyle affect bone growth and health

Bone design is determined by the physical stresses placed upon it -Bone tissue adapts to gravity, physical stresses -Effects bone markings, mass, density -Increased activity increases these factors -Lack of exercise and physical stresses promotes bone wasting, loss of mass and density

Osteoblasts

Bone forming cells, on bone surfaces

How aging affects bone growth and health

Bones decreases in density, mass, and strength because as you age osteoblast activity declines

Growth hormone

Cartilage cell division, growth in epiphyseal plate

Osteoclasts

Cause osteolysis, bone resorption using acids and enzymes

Longitudinal growth of long bones: Describe the role of the epiphyseal plate (disk) and how hormones affect its activities

Chondrocytes (within cartilage) divide and grow causing bone lengthening Within the plate region are several "zones" within which: 1 Chondrocytes divide and enlarge 2 Calcification of the matrix occurs 3 Chondrocytes die, osteoblasts deposit spongy bone 4 Bone remodeling (reshaping) occurs by osteoblasts and osteoclasts Estrogen and testosterone cause closure of the epiphyseal growth plates in late adolescence. The cartilage becomes entirely replaced with bone, and statural growth ceases.

Four main stages involved in the repair of a bone fracture

Hematoma formation Soft callus formation Hard callus formation Bone remodeling

Thyroid hormones

Controls GH, stimulates osteoblasts

Calcitonin

Decreases blood calcium

Osteocytes

Develop from osteoblasts; maintain bone matrix

Osteogenic

Divide and produce osteoblasts

Functions and main locations of red marrow

Functions: Erythrocyte production Main Locations: Spongy bone marrow

Parathyroid hormone

Increases blood calcium

Calcitriol (vitamin D)

Increases blood calcium levels needed for bone deposition

Osteomalacia

Lack of minerals or vitamin D, soft bones (rickets in children)

Scurvy

Lack of vitamin C resulting in painful joints and muscles

Bone classification on the basis of shape

Long - Ulna, Radius Short - Talus, Capitate Flat - Scapula, Sternum Irregular - Vertebra, Sphenoid

Marfan syndrome

Long slender bones, abnormal connective tissue, excessive cartilage in epiphyses

Explain osteopenia and the process of bone aging

Osteopenia—lower than normal bone mineral density (BMD) -gradual loss of bone density, mass, and strength -often associated with aging after age 30 (osteoblast -activity declines, resorption outpaces deposition)

Osteoporosis: Define and describe, compare males vs. females, factors that aggravate and delay or reverse the condition

Severe loss of bone; become lighter, weaker, more porous, and more prone to fracture -Women have less bone mass (BMD) than men (about 30% less) -The loss of bone mass speeds up in women after menopause (bone loss becomes much faster than in men of same ages) -Loss of estrogen after menopause is related to an increase in osteoclast activity -About one-third of postmenopausal women will experience a bone fracture due to osteoporosis (commonly vertebrae, neck of femur, and distal radius) -Immobility can cause osteoporosis regardless of age -Estrogen replacement therapy not as common anymore due to risk of breast cancer, stroke, and heart disease -Biophosphonates—inhibit osteoclasts (slows bone resorption) -Synthetic estrogenic-like drugs -Synthetic PTH—can stimulate new bone deposition -Calcitonin—slows rate of bone resorption -Sufficient vitamin D, calcium, exercise

Sex Hormones

Stimulate osteoblasts & bone growth; feminize or masculinize skeleton

Insulin

Stimulates blood formation

Functions of the skeletal system

Support Protection Movement Electrolyte balance Acid-base balance Blood formation Energy storage