Lesson 5 Skeletal System Flashcards
What is a greenstick fracture?
Incomplete fractures of the ulnar and radial diaphyses
Commonly seen in children due to softer bones.
What process forms the bones of the base of the skull and most remaining bones of the skeletal system?
Endochondral ossification
Begins with cartilage formation at the end of the fourth week of development.
At what age does some ossification begin during endochondral ossification?
About week eight
Some ossification does not begin until 18-20 years of age.
What occurs when the maxillae do not form normally during fetal development?
Cleft lip
A cleft palate occurs when the palatine processes of the maxillae do not fuse.
What is the occurrence rate of cleft lip or palate?
Approximately once in every 1000 births
More common in males.
What condition occurs when the epiphyseal plate ossifies?
Closure of the epiphyseal plate
This occurs between approximately 12 and 25 years of age.
What type of cartilage persists throughout life and does not ossify?
Articular cartilage
Only appositional growth occurs on its surface.
What type of bone growth occurs on the surface of cartilage?
Appositional growth
Interstitial growth cannot occur because the matrix is solid.
What is the primary difference between woven bone and lamellar bone?
Woven bone has randomly oriented collagen fibers
Lamellar bone has fibers oriented in one direction in each layer.
What are the four classes of medications for osteoporosis?
- Bisphosphonates
- Estrogen-like medications
- Antibodies
- Calcitonin-replacement medications
Each class targets different mechanisms of bone density loss.
What dietary recommendation is given for preventing osteoporosis?
Consume at least 1000 mg of calcium per day
1200 mg/day for people over age 50.
What lifestyle factor significantly increases the risk of osteoporosis?
Inadequate calcium intake
Regular weight-bearing exercises can help prevent bone loss.
What is the most common cause of osteoporosis in women?
Decreased reproductive hormone production
Especially after menopause.
What is the effect of proton pump inhibitors (PPIs) on bone health?
Increased risk of fractures
Particularly after long-term use and when other risk factors are present.
What happens to bone density after 8 weeks of immobilization?
Significant amounts of bone are lost
This emphasizes the importance of movement and weight-bearing activities.
What is the function of osteoblasts?
Bone formation
They are responsible for appositional growth.
What is the difference between compact bone and spongy bone?
Compact bone is dense and forms the outer layer, while spongy bone has interconnecting rods or plates
Spongy bone is oriented along lines of stress.
What is the age of Henry, the man with low bone density?
65 years old
What type of fracture did Henry sustain?
Fractured the proximal part of his arm bone (surgical neck of the humerus)
What lifestyle factors contributed to Henry’s low bone density?
Junk food addiction, few vegetables, no dairy, lack of exercise, nocturnal lifestyle
What is the normal range of blood Ca2+ for Henry?
Normal
How do Henry’s eating habits affect his bone density?
Low calcium and vitamin D intake from poor diet
Would Henry’s PTH levels be lower than normal, normal, or higher than normal?
Normal
What effect has Henry’s nocturnal lifestyle had on his bone density?
Reduced exposure to sunlight, leading to lower vitamin D synthesis
How has lack of exercise affected Henry’s bone density?
Decreased bone density due to lack of mechanical stress on bones
What is the role of calcitriol in calcium homeostasis?
Increases blood calcium by stimulating intestinal absorption of calcium
What is calcitonin’s effect on blood calcium levels?
Lowers blood calcium by inhibiting osteoclast activity
What hormone is secreted by the parathyroid gland to regulate calcium levels?
Parathyroid hormone (PTH)
How does PTH affect osteoclast activity?
Activates osteoclasts and increases their number
What is the function of osteoprotegerin in bone remodeling?
Decreases RANKL activity, inhibiting osteoclast formation
What are the three main hormones that control blood calcium levels?
- Parathyroid hormone (PTH) * Calcitriol * Calcitonin
What are the types of bone fractures based on mechanism?
- Traumatic * Disease * Pathologic
What is the effect of growth hormone on bone growth?
Stimulates interstitial cartilage growth and appositional bone growth
What vitamin is crucial for calcium absorption and bone health?
Vitamin D
What condition results from vitamin D deficiency in children?
Rickets
What is osteomalacia?
Softening of bones due to vitamin D deficiency in adults
What is the significance of collagen in bone structure?
Provides tensile strength and resilience to bones
What is osteogenesis imperfecta commonly known as?
Brittle bone disorder
What is the primary cause of osteogenesis imperfecta?
Mutations that yield reduced or defective type I collagen
What is the most common form of osteogenesis imperfecta?
Type I
How does osteomyelitis affect bone health?
- Increases osteoclast development * Stimulates inflammation * Disrupts signaling between osteoblasts and osteoclasts
What is the common treatment for osteomyelitis?
4- to 8-week course of antibiotics
What is the role of toll-like receptors (TLRs) in bone cells?
Recognize bacterial cell markers and initiate immune responses
What is the primary structural component of bone matrix?
- Organic: collagen and proteoglycans * Inorganic: hydroxyapatite
What is the main reason why bones cannot undergo interstitial growth?
Bones lack the cartilage structure that allows for interstitial growth
What is Osteogenesis Imperfecta (OI)?
A connective tissue disease caused by mutations that yield reduced or defective type I collagen.
What is the major collagen type affected in Osteogenesis Imperfecta?
Type I collagen.
What characterizes type I Osteogenesis Imperfecta?
Too little formation of normal type I collagen.
What percentage of normal type I collagen do patients with type I OI produce?
Approximately half.
List some characteristics of type I Osteogenesis Imperfecta.
- Bones predisposed to fracture
- Tendency to develop spinal curvature
- Loose joints
- Brittle teeth
- Hearing loss
- Blue tint to the whites of the eyes.
How does the stature of patients with type I OI compare to those with more severe forms?
Patients have normal or near-normal stature.
What is the range of fractures a person with mild type I OI might experience over a lifetime?
From a few to more than 100.
Why is proper diagnosis important for children with OI?
Because broken bones can be associated with child abuse.
What happens when mutated collagen genes in OI are transcribed?
The resulting mRNA codes for a defective protein.
What is the most severe form of Osteogenesis Imperfecta?
Type II OI.
What is the typical outcome for infants with type II OI?
Usually lethal within the first week of life due to breathing failure.
What characterizes type III Osteogenesis Imperfecta?
Bones that fracture very easily, even before and during birth.
What happens to fractures occurring before birth in type III OI?
They often heal in poor alignment, leaving limbs short and bent.
How many types of Osteogenesis Imperfecta have been described?
At least 12 types.
Is there a cure for Osteogenesis Imperfecta?
No, treatments are primarily directed at reducing the risk for fractures.
What are osteocytes?
Mature bone cells that are stellate and surrounded by matrix.
What are lacunae in bone tissue?
Spaces occupied by osteocyte cell bodies.
What are canaliculi?
Canals occupied by osteocyte cell processes.
What happens to nutrients in the lacunae and canaliculi?
They diffuse through a tiny amount of liquid surrounding cells.
What is the role of osteoblasts?
Formation of bone through ossification or osteogenesis.
How do osteoblasts communicate with each other?
Through gap junctions.
What is osteomalacia?
Softening of adult bones due to calcium depletion, often caused by vitamin D deficiency.
What typically causes growth retardation in bones?
Nutritional deficiencies in minerals (Ca2+) or vitamin D.
True or False: Osteogenesis Imperfecta can be cured.
False.
