Anatomy Ch. 6
Rickets
-A disorder caused by a lack of vitamin D, calcium, or phosphate. -Causes inadequate calcification of bone matrix. -Leads to softening and weakening of bones.
Osteogenisis Imperfecta
-A genetic disorder in which people are born with defective connective tissue or the inability to make it. -Deficiency in Type-1 collagen -Used to form bone
Spongy Bone
-Does not contain osteons -Consists of trabeculae (little beams) surrounding many red marrow filled spaces. -Forms most of the structure of short, flat, and irregular bones. -Forms the epiphysis of long bones. -Light weight. -Supports and protects the red bone marrow
Ossification (osteogenesis)
-During initial bone development as an embryo and fetus. -Growth during childhood and adolescence. -Remodeling of bone during adulthood -Repair of fractures throughout life.
Nutrient arteries
-Enter through nutrient foramina (foramen = opening). -Supplies compact bone of diaphysis.
Intramembranous ossification (intra = within)
-Forms the flat bones of the skull. -Begins as mesenchymal cells that develop within a membrane. -Many ossification centers grow simultaneously. -Does not go through a cartilage stage
Compact Bone
-Looks like a solid layer of bone. -Contains few spaces -Makes up the diaphysis (shaft) of long bones and the external layer of all bones. -Resists stresses produced by weight and movement. -Contains osteons
Endochondral ossification (chondral = cartilage
-Method used in the formation of most bones, especially long bones. -Bone formation begins with a cartilage model that gets replaced by bone. -Ossification begins in the diaphysis at the primary ossification center. -Secondary ossification centers take place in the epiphyses. -A layer of hyaline cartilage remains between the two ossification centers as the epiphyseal (growth) plate.
Periosteal arteries
-Supply the periosteum. -Accompanied by nerves
Intramembranous ossification (intra = within) Endochondral ossification (chondral = cartilage
2 types of ossification take place:
Mechanical Stress
Bone constantly remodels and redistributes its matrix along lines of
Diaphysis
Bone shaft
Rickets
Bones may also become too soft is called
Osteoporosis
Excessive loss of calcium weakens the bones is called
18-21
Growth plate closes
Thick and heavy (acromegaly)
If too much new tissue is formed, the bones become
Osteoporosis
Older individuals (especially post-menopausal women) experience a decrease in bone mass when resorption outpaces deposition
Metaphyseal and Epiphyseal arteries
Supply the red marrow and bone tissue of the epiphyses.
Collagen Fibers and Hydroxyapatite
The matrix consists of
Parathyroid hormone (PTH)
When blood calcium levels are low, osteoclasts are stimulated to resorb bone. Under control of
Calcitonin (Thyroid gland)
When blood calcium levels are too high, osteoblasts are stimulated to deposit bone. Under control of
Fracture
a break in a bone
Deposition
addition of minerals and collagen fibers to bone by osteoblasts.
Bone formation
begins during 6th week of embryonic development.
Osteoclast
bone crusher
Osteoprogenitor cells
bone stem cells able to differentiate into the other types of cells
Osteoblasts
bone-building cells that secrete matrix
2 Epiphyses
both ends of the bone at the joints
Periosteum
connective tissue surrounding the diaphysis
Medullary Cavity
hollow space within diaphysis
Reparative phase
includes formation of a fibrocartilaginous callus first and a bony callus second.
Reactive phase
is an early inflammatory phase
Compact Bone
is good at providing protection and support.
Spongy Bone
is lightweight and provides tissue support
Bone remodeling phase
is the last step as a bony callus is remodeled
Ossification (osteogenesis)
is the process of bone formation.
Osteocytes
mature bone cells
Calcification
mineral salts are deposited in a framework of collagen fibers.
Calcification
only occurs in the presence of collagen fibers
2 Metaphyses
region between diaphysis and epiphysis
Osteoclasts
remodel bones and cause them to release calcium
Resorption
removal of minerals and collagen fibers from bone by osteoclasts.
Endosteum
thin membrane lining the medulary cavity
Bone (osseous)
tissue consists of widely separated cells surrounded by a hardened extracellular matrix
adulthood
when are production and remodeling rates the same
birth through adolescence
when is more bone is produced than lost during remodeling.