Chapter 6: Bone Tissue Flashcards
Bone
an organ made up of several different tissues
Functions of Bone
- provide support
- protect the internal organs
- assist body movement
- mineral homeostasis (stores & releases calcium + phosphorus)
- participates in blood cell production (hemopoiesis)
- stores triglycerides in adipose cells of yellow marrow
Long Bone
consists of diaphysis, 2 epiphyses, 2 metaphyses, articular cartilage, periosteum, medullary cavity, endosteum
diaphysis
bone shaft
epiphyses
both ends of the bone at the joints
periosteum
connective tissue surrounding the diaphysis
medullary cavity
hollow space within diaphysis
endosteum
thin membrane lining medullary cavity
what are the 4 types of cells found in bones?
osteoprogenitor cells, osteoblasts, osteocytes, osteoclasts
osteoprogenitor
bone stem cells able to differentiate into other types of cells
osteoblasts
bone building cells that secrete matrix
osteocytes
mature bone cells
osteoclasts
remodel bones and cause bones to release calcium
histology of bone
osetoprogenitor cells develop into an osteoblast –> osteoblast form bone extracellular matrix –> osteocytes maintain bone tissue –>osteoclasts functions in resorption, the breakdown of bone extracellular matrix
compact bone
good at providing protection and support
spongy bone
lightweight, and provides tissue support
periosteal arteries
accompanied by nerves; enter the diaphysis through the Volkmann’s canals. They are accompanied by periosteal veins
nutrient artery
enters the center of the diaphysis through a nutrient foramen
nutrient veins
exit through nutrient foramen
what do the metaphases and epiphyses have in common?
they have their own arteries and veins
ossification (osteogenesis)
process of bone formation
what 4 situations do bones form in?
during embryological and fetal development, when bones grow before adulthood, when bones remodel, and when fractures heal
intramembranous ossification
occurs in flat bones when a connective tissue membrane is replaced by the bone
endochondral ossification
replaces cartilage with bones in the developing embryo and fetus; occurs in the epiphyseal plates of long bones as they grow in length
how do bones thicken?
cooperative action of osteoblasts and osteoclasts
as osteoblasts deposit bone on the outer surface, osteoclasts widen the medullary cavity from within
fracture
break in the bone; healing process involves 3 different phases
reactive phase
early inflammation phase
reparative phase
formation of a fibrocartilaginous callus first, and then a bony callus
bone remodeling phase
last step as bony callus is remodeled
open (compound) fracture
broken ends of the bone protrude through the skin.
closed (simple) fracture
bone does not break the skin
comminuted fracture
bone is splintered, crushed, or broken into pieces at site of the impact, and smaller bone fragments lie between the two main fragments
greenstick fracture
partial fracture in which one side of the bone is broken and the other side bends, similar to the way a green twig breaks on one side while the other stays whole but bends; typically occur in children whose bones are not fully ossified
impacted fracture
one end of the fractured bone is forcefully driven into the interior of the other
pott fracture
fracture of the distal end of the lateral leg bone (fibula), with serious injury of the distal tibial articulation
colles fracture
fracture of the distal end of the lateral forearm bone (radius), in which the distal fragment is displaced posterioly
bone’s role in calcium homeostasis
- bone stores 99% of the body’s calcium
- the parathyroid gland secrets the parathyroid hormone (PTH) when calcium levels drop too much & PTH stimulates the production of calcitriol in the kidneys to increase calcium absorption in the intestines
aging
- more bone is produced than lost during remodeling
- post menopausal women experience a decrease in bone mass when resorption outpaces deposition
calcium + phosphorus
make bone extracellular matrix hard
magnesium
helps bone form extracellular matrix
fluroide
helps strengthen extracellular matrix
manganese
activates enzymes involved in synthesis of bone extracellular matrix
vitamin a
- needed for activity of osteoblasts during remodeling of bone
- deficiency stunts bone growth
- toxic in high doses
vitamin c
- needed for synthesis of collagen
- deficiency causes low collagen production which slows bone growth and delays repair of broken bones
vitamin d
- active from calcitriol / produced by kidneys; helps build bone by increasing absorption of calcium from GI tract to blood
- deficiency causes faulty calcification and slows down bone growth
- may reduce risk of osteoporosis but is toxic in high doses
vitamin k and b12
- needed for synthesis of bone proteins
- deficiency leads to abnormal protein production in bone extracellular matrix and decreased bone density
growth hormone
secreted by anterior lobe of piutary gland; promotes general growth of all body tissues including bone, mainly by stimulating process of insulin like growth factors
insulin like growth factors
secreted by the liver, bones and other tissues on stimulation by growth hormones; promotes normal bone growth by stimulating osteoblasts and by increasing the synthesis of proteins needed to build new bone
thyroid hormone (T3 and T4)
secreted by thyroid gland; promotes normal bone growth by stimulating osetoblasts
sex hormones - estrogens and testosterone
secreted by ovaries in women and by testes in men; stimulate osteoblasts and sudden growth spurt that occurs in teenage years; shuts down the growth at epiphyseal plate around age 18-21 causing lengthwise growth of bones to stop
disorders include
osteoporosis, rickets, osteomalacia
