Bone development and clinical application

what do all skeletal features start as?

fibrous connective tissue or hyaline cartilage

when does the formation of the skeleton happen in utero?

week 8

hypertrophic zone

older cartilage cells enlarge

calcification zone

matrix becomes calcified, cartilage cells die; matrix begins deteriorating

ossification zone

new bone is forming

postnatal growth length

1. proliferation

2. hypertrophic

3. calcification

4. ossification

Postnatal growth - width

• Completed through appositional growth

• Osteoblasts in the periosteum secrete bone matrix to the external bone surface

• Osteoclasts on the endosteal surface remove bone

what do hormones determine?

if and when bones are remodeled

what does mechanical stress determine

where bones are remodeled

role of calcium in body

homeostasis for maintaining resting membrane potentials

where is the bodys calcium stored?

in bone matrix

hormones will maintain a level of…

…9-11 mg/dL of blood

parathyroid hormone

secreted by parathyroid glands

what are the functions of the parathyroid hormone?

• stimulate osteoclasts to promote bone resorption

• promotes calcium reabsorption by kidneys

• promotes final step of calcitriol synthesis in the kidneys

• inhibits collagen synthesis via osteoblasts

wolfs law

the body adapts to the forces placed upon it

transverse fractures

oblique fractures

spiral fractures

comminuated fractures

avulsion fractures

impacted fractures

fissure fractures

greenstick fractures

4 stages for traumatic (acute) fracture healing

1. hematoma formation

2. solf callus formation

3. hard callus formation

4. bone remodeling

hematoma formation

hematoma is converted to granulation tissue by invasion of cells and blood capillaries

soft callus formation

deposition of collagen and fibrocartilage converts granulation tissue to a soft callus

hard callus formation

osteoblasts deposit a temporary bony collar around the fracture to unite the broken pieces while ossification occurs

bone remodeling

small bone fragments are removed by osteoblasts, while osteoblasts deposit spongy bone and then convert it to compact bone

osteoporosis

group of diseases in which bone reabsorption outpaces bone deposit

osteoporosis diagram

osteomalacia

group of diseases in which bones are poorly mineralized

whats the child version of osteomalacia?

rickets → bowed legs; deformities to the skull pelvis, and ribs

what does osteomalacia result in?

weak and soft bones

osteitis deformans

haphazard bone deposit and resorption; abnormally high ration of spongy bone

common areas osteitis deformans appears in

spine, pelvis, femur, skull

proliferation zone

cartilage cells undergo mitosis

calcitonin

promotes mineralization and lowers blood Ca2+ concentration in children, but usually has a little effect in adults; may prevent bone loss in pregnant and lactating women

calcitriol

promotes intestinal absorption of Ca2+ and phosphate; reduces urinary excretion of both; promotes resorption and mineralization; stimulates osteoclast activity