Bone tissues 6b Flashcards
Growth zone
cartilage cells undergo mitosis, pushing the epiphysis away from the diaphysis
Transformation zone
older cells enlarge, the matrix becomes calcified, cartilage cells die and the matrix begins to deteriorate
Osteogenic zone
new bone formation occurs
Growth in length
cartilage continually grows and is replaced by bone
Remodeling
bone is resorbed and added by appositional growth
Alkaline phosphatase
is essential for mineralization of bone secreted by osteoblasts
Osteoid seam
unmineralized band of bone matrix
Bone Deposition
Occurs where bone is injured or added strength is needed
Requires a diet rich in protein, vitamins C, D, and A, calcium, phosphorus, magnesium, and manganese
Bone Resorption
Accomplished by osteoclasts
Resorption involves osteoclast secretion of
Lysosomal enzymes that digest organic matrix
Acids that convert calcium salts into soluble forms
Calcium is necessary for
Transmission of nerve impulses Muscle contraction Blood coagulation Secretion by glands and nerve cells Cell division
Rising blood Ca2+ levels trigger the thyroid to
release calcitonin
Calcitonin
stimulates calcium salt deposit in bone
Falling blood Ca2+ levels signal the parathyroid
glands to
release PTH
PTH signals osteoclasts to
degrade bone matrix and release Ca2+ into the blood
Bone fractures are classified by
The position of the bone ends after fracture
The completeness of the break
The orientation of the bone to the long axis
Whether or not the bones ends penetrate the skin
Nondisplaced
bone ends retain their normal position
Displaced
bone ends are out of normal alignment
Complete
bone is broken all the way through
Incomplete
bone is not broken all the way through
Linear
the fracture is parallel to the long axis of the bone
Transverse
the fracture is perpendicular to the long axis of the bone
Compound (open)
bone ends penetrate the skin
Simple (closed)
bone ends do not penetrate the skin
Common Types of Fractures - Comminuted
bone fragments into three or more pieces; common in the elderly
Common Types of Fractures - Spiral
ragged break when bone is excessively twisted; common sports injury
Common Types of Fractures - Depressed
broken bone portion pressed inward; typical skull fracture
Common Types of Fractures - Compression
bone is crushed; common in porous bones
Common Types of Fractures - Epiphyseal
epiphysis separates from diaphysis along epiphyseal line; occurs where cartilage cells are dying
Common Types of Fractures - Greenstick
incomplete fracture where one side of the bone breaks and the other side bends; common in children
Osteomalacia
Bones are inadequately mineralized causing softened, weakened bones
Main symptom is pain when weight is put on the affected bone
Caused by insufficient calcium in the diet, or by vitamin D deficiency
Rickets
Bones of children are inadequately mineralized causing softened, weakened bones
Bowed legs and deformities of the pelvis, skull, and rib cage are common
Caused by insufficient calcium in the diet, or by vitamin D deficiency
Osteoporosis
bone reabsorption outpaces bone deposit
Occurs most often in postmenopausal women
Bones become so fragile that sneezing or stepping off a curb can cause fractures
Osteoporosis: Treatment
Calcium and vitamin D supplements
Increased weight-bearing exercise
Hormone (estrogen) replacement therapy (HRT) slows bone loss
Natural progesterone cream prompts new bone growth
Statins increase bone mineral density
Paget’s Disease
Characterized by excessive bone formation and breakdown
Pagetic bone with an excessively high ratio of woven to compact bone is formed
Pagetic bone, along with reduced mineralization, causes spotty weakening of bone
Osteoclast activity wanes, but osteoblast activity continues to work
Usually localized in the spine, pelvis, femur, and skull
Unknown cause (possibly viral)
Paget’s Disease treatment
Treatment includes the drugs Didronate and
Fosamax
OSTEOGENESIS IMPERFECTA
A defect in collagen synthesis
Genetic (from parents), or could be a spontaneous genetic mutation
