Topic 3 - The Skeletal System (V-VI [end]) Flashcards
Types of bone growth
- intramembranous (dermal) bone
- endochondral (cartilaginous) bone
Intramembranous bone is also known as
Dermal bone
Bones at the top of the skull + clavicle are
Intramembranous (dermal) bone
Bones of the skull base + all postcranial bones, including parts of the clavicle
Endochondral (cartilaginous) bone
What is the ontogenetic process in endochondral bone?
- cartilaginous model forms (composed of hyaline cartilage)
- ossification begins
What composes the cartilaginous model in the ontogenetic process i endochondral bone
Hyaline cartilage
Stages of ossification
- internally, cartilage disintegrates and excavates interior of the bone
- externally, periosteum forms
When ossification begins, what do the blood vessels do?
They invade, bringing undifferentiated mesenchymal cells
What do the mesenchymal cells differentiate into?
Osteoprogenitor cells, then osteoblasts, which start forming spongy bone
What happens externally when ossification begins?
The periosteum forms.
- osteoprogenitor cells within the cellular layer of the periosteum mature into osteoblasts
- osteoblasts start forming compact bone
Further growth takes place in 2 directions. What are they?
- interstitial growth
- appositional growth
What is interstitial growth?
Growth between the diaphysis and epiphysis
What happens during interstitial growth?
- blood vessels invade ends of bone as well, which become secondary centers of ossification (epiphyses)
- epiphyseal plate
- growth ceases when plate ossifies
The epiphyseal plate is what?
Zone of hyaline cartilage remaining between primary and secondary ossification centers, site of active growth
Appositional growth does what?
Increases in over-all size
How is new compact bone deposited in appositional growth>
By osteoblasts, just below the periosteum
In appositional growth, what do osteoclasts do?
Destroy bone tissue and enlarge the medullary cavity (if. Present) at the inner bone surface; remodel compact bone/spongy bone interface
Appositional growth ceases when?
When the plate ossifies
What are the 4 steps of the ontogenetic process in intramembranous bone?
- membranous layer forms around the blood vessels
- ossification begins
- remaining growth takes place via mechanism similar to appositional growth of endochondral bone
- process ends concurrently with endochondral growth
When ossification begins, where does it occur?
Internally and externally
During internal ossification, what happens?
Undifferentiated connective tissue cells around blood vessels differentiate into osteoprogenitor cells, then osteoblasts, which start forming spongy bone
During external ossification, what happens?
Periosteum forms; cells within the cellular layer differentiate into osteoprogenitor cells, then osteoblasts, which start forming compact bone below periosteum.
What is Wolff’s law?
bone remodels its shape according to the way force is transmitted through it
What are the clinical considerations with the skeletal system?
- chemical disorders
- trauma and injury: fracture
- infectious disease
- neoplasms
- aging
Subcategories of chemical disorders
nutritional and hormonal
What are the forms of nutritional disorders?
Vit. C and Vit. D
Why is Vit C important for the skeletal system?
- necessary for proper collagen formation
- deficiency leads to scurvy
Where is Vit. D synthesized?
within the skin or ingested as part of the diet
What are the stages of vit. D synthesization?
Which one do we really need?
- 7-dehydrocholesterol in the skin (in the presence of ultraviolet radiation [UVR] becomes
- cholecalciferol [vit. D3] goes to
- liver to become 25-hydroxycholeclciferol, which goes to
- kidneys to become 1,25-dihydroxycholecalciferol
- really need cholecalciferol (Vit. D3)
What does Vit. D do for bone growth?
Facilitates proper bone mineralization by increasing absorption of calcium within the small intestine and reabsorption of calcium in the kidneys
Deficiency of Vit. D leads to what in children?
To what in adults?
- rickets (soft bones) d/t being less heavily mineralized
- osteomalacia (fatigued, joint aches, bone aches)
What are the hormonal clinical considerations with the skeletal system?
- parathyroid hormone (PTH)
- pituitary growth hormone (GH)
What does PTH do?
Increases amount of calcium in blood by indirectly stimulating osteoclasts activity
What happens when parathyroid hormone binds to receptors ion the osteoblasts?
The osteoblasts release osteoprotegerin ligand (OPGL)
What happens when OPGL activates receptors o n the preosteoclast cells?
causes them to mature into osteoclasts
What do the osteoclasts?
Start breaking down bone tissue
Excess parathyroid hormone leads to what?
bone thinning
Excess pituitary growth hormone (GH) leads to what in children?
Leads to what in adults?
- gigantism
- acromegaly
Deficit of pituitary growth hormone (GH) leads to what in children
Dwarfism
What are the different types of fractures?
- comminuted
- compression
- greenstick
What are the stages of healing a fracture?
- fracture hematoma formed from ruptured blood vessels
- soft callus forms (mixture of spongy bone and fibrocartilage)
- hard callus forms by mineralization and remodeling of soft callus
- remodeling of hard callus to mature (compact and spongy) bone
What are the infectious disease of bone?
- osteitis
- periostitis
- osteomyelitis
- tuberculosis
What is osteitis?
Inflammation of bone tissue caused by injury or infection
What is perriostitis?
Inflammation of periosteum caused by trauma or infection
What is osteomyelitis?
Inflammation of bone interior caused by bacteria, usually initially entering the bone via wound or via bloodstream
What does tuberculosis spread to?
The spongy bone (particularly of the vertebral bodies [Pott’s disease]), resulting in bone nad joint destruction.
What are the 2 types of neoplasms (tumors) of bone?
Benign and malignant
What are the 2 types of benign neoplasms?
Osteochondroma and osteoma
What are the 2 types of malignant neoplasms?
Osteogenic sarcoma (osteosarcoma) and multiple myeloma
Which kind of neoplasms can kill you?
The malignant (osteogenic sarcoma and multiple myeloma)
What happens to the skeletal system when one ages?
- The repair/healing process is slowed
- osteoperosis
What can osteoporosis result from?
Hyperthyroidism, hyperparathyroidism, prolonged vitamin C deficiency
Who is osteoporosis most prevalent in?
Older women
Why are women more prevalent with osteoporosis?
- women have less bone mass than men
- women lose bone mass sooner and faster than men
What kind of man would it be common to see osteoporosis in?
One being treated for prostate cancer
What is bone density?
Mass / vol.
When do women start losing bone mass?
After age 35
When do men start losing bone mass?
In 60’s
