Chapter 6: The Skeletal System: Bone Tissue

stress fracture

series of microscopic fissures in bone

diaphysis

shaft of bone

periosteal arteries

supply the periosteum and compact bone

Functions of bone and skeleton system

support, protection, assistance in movement, mineral homeostasis, blood cell protection, triglyceride storage

osteons

structural unit of compact bone

greenstick fracture

(only in kids) a partial fracture in which one side of the bone is broken and the other side bends

steps in the repairing of bone

1. formation of fracture hematoma 2. fibrocartilaginous callus formation 3. bony callus formation 4. bone remodeling

effects of aging

1. loss of bone mass 2.brittleness

steps of intramembranous ossification

1: development of ossification center 2:calcification 3:formation of traveculae 4:development of the periosteum

steps of endochondral ossification

1:development of cartilage model 2:growth of cartilage model 3:development of primary ossification center 4:development of medullary cavity 5:development of secondary ossification center 6:formation of articular cartilage and epiphyseal plate

compact bone

80% of bone, resists the stresses produced by weight and movement

PTH

acts on the kidneys to decrease the loss of Ca in the urine

How do bones maintain mineral homeostasis

acts to serve as a reservoir of critical minerals (calcium and phosphorus)

Bone tissue

alters its strength in response to changes in mechanical stress

lacunae

between lamellae, contain osteocytes

metaphysis

between shaft and ends of bone

hematoma

blood clot

bone

body's major calcium resevoir

osteoblasts

bone building cells, synthesize extracellular matrix of bone tissue

spongy bone

bone that lacks osteons, helps bones resist stresses without breaking, sight of hemopoiesis

rickets

bones become too flexible (decreased vitamin D, phosphorus, and calcium)

open (compound) fracture

broken ends of the bone protrude through the skin

minerals

calcium, phosphorus, magnesium, fluoride, manganese required for bone growth and remodeling

epiphyseal veins

carry blood away from long bones

estrogen and testosterone

cause sudden "growth spurt" during teenage years, promtes changes in females, such as widening of the pelvis, shut down growth at epiphyseal plates

Decrease in sex hormones

causes a decrease in bone mass, bone resorption by osteoclasts outpaces bone deposition by osteoblasts

medullary cavity

cavity with yellow bone marrow

levels of calcium

controlled by rates of calcium resorption from bone in to blood and of calcium deposition from blood to bone

periosteum

covering of bone where there is no articular cartilage

closed (simple) fracture

doesn't break the skin

endochondral ossification

embryonic formation: replacement of cartilage by bone

epiphysis

ends of bone

articular cartilage

ends of epiphysis, perforating fibers attach the cartilage to bones

osteoporosis

excessive loss of calcium weakens the bones

when does bone form?

formation of bone in an embryo, growth of bones until adulthood, remodeling of bone, repair of fractures

pott's fracture

fracture of the fibula, with injury of the tibial articulation

Colles' fracture

fracture of the radius in which the distal fragment is displaced

collagen fibers

gives bones its tensile strength

bone growth during childhood

growth in thickness, remodeling of bone (ongoing replacement of old bone tissue by new bone tissue)

weight bearing activities

help build and retain bone mass

Vitamin D

increases absorption of calcium

Insulin

increases synthesis of bone proteins

PTH

increases the number and activity of osteoclasts (break down bone)

calcification

initiated by osteoblasts, crystallization of mineral salts

trabeculae

lattice of thin columns in spongy bone, support and protect bone marrow,

endosteum

lines internal cavity

osteocytes

mature bone cells, exchange nutrients and wastes with the blood

calcium phosphate

most abundant mineral salt

Vitamin K and B12

needed for synthesis of bone proteins

Vitamin C

needed for synthesis of collagen

impacted fracture

one end of the fractured bone is forcefully driven into another

intramembranous ossification

one way bone forms in embryo, "soft spots" that help fetal skull pass through birth canal that become ossified later

parathyroid hormones, calcitriol calcitonin

other hormones that affect remodeling

osteogenic cells

percursor to bone forming cells; undergo cell division; the resulting cells develop into osteoblasts

ossification

process by which bone forms

Thyroid hormones

promote bone growth stimulating osteoblasts

canaliculi

radiate in all directions from lacunae, filled with extracellular fluid, provide routes for nutrients and oxygen

Three types of blood cells

red blood cells, white blood cells, platelets

PTH

regulates Ca exchange between blood and bone tissue

osteoclasts

release enzymes that digest the mineral components of bone matrix, regulate blood calcium level, break bone down

concentric lamellae

rings of calcified matrix around central canals

Calcitonin (CT)

secreted by thyroid gland, inhibits activity of osteoclasts

epiphyseal line

signifies growth has stopped

Red bone marrow

site of hemopoiesis (formation of blood cells)

osteomalacia

softening of bone because of a lack in vitamin D

IGF's

stimulate osteoblasts, promotes cell division at the epiphyseal plate, and enhance protein sythesis

Vitamin A

stimulates activity of osteoblasts

PTH

stimulates the formation of calcitriol, a hormone that promotes absorption of calcium from food in the gastrointestinal tract

triglyceride

stored in adipose tissue, serves as potential chemical energy reserve

Extracellular matrix

surrounds widely separated cells, 25% water, 25% collagen fibers, 50% crystallized mineral salts

comminuted fracture

the bone is splintered, crushed, or broken into pieces

spurs

too much new tissue is formed and bones become abnormally thick and heavy