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
