ToB: Bone and Cartilage Flashcards
Name 6 functions of bone
locomotion, strength, protection, enables forceful muscle contractions, bone density adapts to mechanical demands, mineral storage, hematopoiesis in bone marrow
Name 3 differences between compact and spongy bone, and the role of these differences
Compact:
1: Has periosteum: Layer of dense vascular CT that envelops bones
2. Haversian and Volkmann’s canals: carries blood vessels, lymphatics and nerves
3. Spongy bone is lighter: provides space for yellow and red bone marrow (has stem cells that form blood and immune cells)
Where are osteocytes found in compact bone and what do they originate from?
Metabolically active and embedded in the lacuna, mature osteoblasts
What is the surface area of spongy bone lined with?
Osteoblasts (smaller) and larger osteoclasts
Name the unit of bone and what it’s typically comprised of
Lamellae, matrix and Haversian canals (in compact)
What makes the organic component of bone?
Type I collagen: the osteoid; calcifies and mineralizes bone (needs an inorganic component to embed within collagen fibres)
Provides flexibility and stress resistance
What makes the inorganic component of bone?
Calcium hydroxyapatite crystals: stores Ca2+ and phosphate which embeds in the organic component that gives bone hardness and compression ability
Name the 4 stages of bone repair after fracture
- Hematoma
- Soft fibrocartilage callus: clot removed by macrophages and replaced by procallus tissue, collagen and fibroblasts
- Hard bony callus: fibrocartilage turns into woven bone *invaded by blood vessels and osteolasts
- Bone remodelling; aided by cutting cones
Which bones are developed by Endochondral ossification and is its overall process?
All bones below the skull EXCEPT the clavicle:
Begins in utero from a hyaline cartilage template, bone collar develops and primary ossification centre (angiogenesis and osteoprogenitor invasion), at birth the secondary ossification centre develops on the other side of the epiphyseal growth plate.
The plate continually fuses and pushes for bone elongation until the end of puberty
If the epiphyseal growth plate fuses at puberty, how are bones capable of appositional growth?
The periosteum keeps a reservoir of osteoblasts
What are 2 core differences between endochondral ossification and intramembranous?
Intramembranous forms flat bones (like in skull) and instead of using a hyaline cartilage template, osteoblasts differentiate from local mesenchymal tissue
What happens to bone growth if there are insufficient/excessive sex hormones?
Insufficient: bone growth continues longer than normal and person is taller (no sex hormones to close the growth plate)
Excessive: growth plate fuses early
What are the effects of insufficient/excessive growth hormone on bones?
What is the name of the growth hormone and where is it synthesized?
Somatotrophin: synthesized in the anterior pituitary
Insufficient: pituitary dwarfism
Excessive: gigantism
Name two bone diseases caused by a calcium deficiency/significant lack of Vitamin D and their common symptoms
Adult version: Osteomalacia: bone pain, back-ache, muscle weakness, increased risk of fracture
Child version: Rickets: long bones soft/malformed, bow legs, bossing, enlargement of costochondral rib junction
What kind of mutation occurs in osteogenesis imperfecta? What are the two types?
Autosomal dominant mutation of type I collagen: COL1A1 or COL1A2
Type 1: frequent fractures after walking, bones thin and curved, shorter, blue sclera, progressive hearing loss
Type 2: lethal perinatal disease
Name a bone disease with a genetic basis other than OI
Achondroplasia: Short limbed dwarfism
Autosomal dominant mutation of the fibroblast growth factor so FGFR3 promotes early growth plate closure, leading to fewer chondrocytes to generate the matrix
Osteoporosis:
Name 3 common sites
How it can be diagnosed and treated (and why)
And the two types and their cellular activity
Common sites: wrist, hip and spine
Detected with DEXA scan that measures bone mineral density, treated with bisphosphonates that bind to the calcium hydroxyapatite crystals protecting them from osteoclasts
Type 1: post-menopausal women: less estrogen and increased osteoclast activity
Type 2: Elderly, reduced osteoblast activity
Name 4 modifiable and non-modifiable risk factors for Osteoporosis
Modifiable: smoking, alcohol, exercise, Ca2+ intake
Non modifiable: age, gender, previous fractures, other diseases like rheumatoid
Name 3 general features of cartilage
Not innervated, non-vascularized and slow turnover
What do chondroblasts do and how do they become chondrocytes?
Chondroblasts secrete ECM and divide into the perichondrium. They form small groups of cells called isogenous groups that become separated and continue to produce matrix.
When a chondroblast is fully embedded in the matrix it becomes a chondrocyte - they are the only cells found in healthy cartilage
What is the perichondrium?
CT that envelops cartilage where it’s not a joint
Where is hyaline cartilage commonly found and what is it composed of?
Trachea, end of long bones, articulate cartilage found at joints, larynx, connects ribs to sternum
Composed of ECM: type II collagen, water and GAGS (proteoglycans attached to hyaluronic acid (keeps it hydrated)
Name 3 features of hyaline cartilage
and why they appear that way if needed
Glassy: fibrils in Type II collagen don’t form fibres
Provides smooth surface for articulation
A large ratio of GAGs to collagen facilitate diffusion of substances between chondrocytes and blood vessels
What types of cartilage don’t have a perichondrium?
Articulate cartilage (hyaline) and fibrocartilage
Name where fibrocartilage is commonly found, what it’s composed of and 3 features
Menisci of knee, pubic symphysis and IV discs
Type I collagen, regular CT and hyaline cartilage
Tough, inflexible and shock absorbing
Name 2 common sites for elastic cartilage, what it’s composed of and its main role
*Bonus! what doesn’t elastic cartilage do with age?
Epiglottis and external ear
Type II collagen, elastic network
Flexible and allows for recoil
Elastic cartilage doesn’t calcify with ageing
What’s the main pathology of osteoarthritis?
Name 2 risk factors
Wear and tear of articulate cartilage combined with a lack of stem cells means cartilage doesn’t heal after damage; joint and soft tissue around joint are affected
Age and weight gain
What is the cause of meniscal damage (think simple)
Wear and tear of meniscal fibrocartilage
Name the disease caused by excess GH secreted from the pituitary stimulating appositional growth?
Acromegaly
