Week 4 - Bone Tissue Flashcards
Label the structures of the long bone
- Diaphysis (shaft of long bone)
- Epiphyses
- Metaphyses
What is the function of the Diaphysis?
Responsible for supporting the weight of the body as columns and, at the same time, increase the power of the muscles working as a lever.
What is the function of the Epiphyses?
Aids in the growth of bone length
What is the function of the Metaphyses?
- Growth in length occurs at the growth plate (epiphyseal plate)
- Transfer loads from weight-bearing joint surfaces to the diaphysis (In adults)
Briefly explain how bones grow in length (where does this growth occur)
The growth plate (Epiphyseal plate) is located in the metaphyses (which is located between the middle and the end of the long bones)
Describe the location of the periosteum
Connective tissue sheath that wraps around the external surface of bone wherever it isn’t covered by articular cartilage
State four functions of the periosteum
- Protects bone
- Point of attachment for ligaments and tendons
- Nourishes bone tissue
- Helps in fracture repair
Explain why severe pain occurs with bone fractures and bone marrow puncture
The Periosteum is rich in sensory nerves which are very sensitive to tearing or tension
Name the two types of bone tissue
- Compact
- Spongy
Location of Compact bone
Dense, smooth solid on the outer layer of bones
Function of compact bone
- Protection and support of spongy bone, blood vessels and nerves
- Resists stresses produced by weight and movement
What is the structure of compact bone?
- Made up from Osteons that are arranged parallel to the diaphysis of long bones (this gives the long bones strength)
- Within and between the osteons is extracellular fluid that contains osteocytes to maintain the bone tissue (this enables the exchange of nutrients and oxygen and removal of waste)
- Osteons give the strength and resistance to compact bone
Location of Spongy bone
Always in the interior of bones
Function of spongy bone
- Lightweight which means it can be moved by skeletal muscle contraction
- Protects bone marrow (red and yellow)
What does bone marrow provide?
Nutrients to osteocytes
What is the structure of spongy bone?
- Less dense than compact bone as it contains bone marrow
- Fine trabeculae ‘Little Beams’
- Oxygen and nutrients pass from blood vessels that surround the trabeculae
- Trabeculae are positioned along lines of stress - resist stress
Describe three structural differences between the two types of spongy and compact bones
- SPONGY:
- Consists of trabeculae (does not contain osteons)
- Forms the interior of the epiphysis of long bones
and most of the structures of short, flat bones - Makes bones lighter and easier to move
- Houses bone marrow
- COMPACT:
- Consists of osteons with little space between them
- Forms the exterior surface of bones and covers
spongy bone- Is the strongest form of bone (protects, supports,
resists stress)
- Is the strongest form of bone (protects, supports,
Name two main types of cartilage
- Hyaline cartilage
- Fibrocartilage
Location for Hyaline cartilage
- Supports external nose (nasal cartilage)
- Covers ends of most bones at movable joints (articular cartilage)
- Connect ribs to sternum (costal cartilage)
- Also in the larynx, trachea, bronchi & bronchial tubes
Function of Hyaline cartilage
- Provides smooth surfaces for joint movement
- Provides support & flexibility for joints
Location of Fibrocartilage
- At sites subject to both pressure and stretch
- Intervertebral discs
- Pubic symphysis
- Cartilage pads in knee (Minisci)
Function of fibrocartilage
To support and join structures together
Where does the Extracellular matrix surround?
Bone cells
What does the Extracellular matrix contain?
- Water
- Collagen Fibres
- Crystallized mineral salts
Name the 4 different bone cells
- Stem cells
- Osteoblasts
- Osteocytes
- Osteoclasts
Function of stem cells
Develops into osteablast
Function of osteoblasts
Bone forming cells that produce bone matric
Function of osteocytes
Exchange nutrients and wastes in the extracellular matrix
Function of Osteoclasts
Release enzymes to breakdown bone - called bone resorption
Name the main type of fibre in the extracellular matrix
Collagen fibres
What is the function of collagen fibres?
These fibres give bone its flexibility and strength to resist being torn
Explain the difference between the epiphyseal plate and the epiphyseal line
- In adults, the epiphyseal cartilage is no longer present and elongation of bones has stopped.
- The epiphyseal growth plate becomes an “epiphyseal line” as growing cartilage is replaced by calcified bone. As a bone matures, the epiphyseal plate progresses to an epiphyseal line.
Explain what occurs during bone remodelling
Is the continual replacement of old bone tissue with new bone tissue that is more resistant to fracture.
What would happen if bone remodelling doesn’t happen?
If this didn’t occur then the bone would become very brittle and more prone to fracture
Define the term bone deposit
Addition of collagen fibres and minerals to bone
What cell is involved with bone deposit?
Osteoblasts
Define the term bone resorption
Removal of collagen fibres and minerals
What cell is involved with bone resorption?
Osteoclasts
State three factors that affect bone remodelling
- Genetic Factors
- Mechanical and gravitational forces on the skeleton
§ Exercise
§ Bed rest
§ Sedentary lifestyles - Blood calcium levels
What is bone remodelling?
Part of the fracture repair process as it removes the injured bone tissue and produces new bone tissue that is more resistant to fracture
Name the two hormones that control bone remodelling
- Parathyroid
- Calcitonin
What is the action of Parathyroid? How does it impact on blood calcium levels?
- Released from the parathyroid glands raises the blood calcium levels by stimulating the osteoclasts to break down bone.
- This releases calcium into the blood
What is the action of Calcitonin? How does it impact on blood calcium levels?
- Released from the thyroid gland when blood calcium levels are too high to inhibit the activity of osteoclasts, preventing bone resorption.
It lowers the blood calcium level
What are the 4 stages of bone healing IN ORDER
- Fracture haematoma forms
- Soft procallus forms
- Bony callus
- Bone remodelling
Explain what happens during Fracture Haematoma formation, and how long after injury it happens?
- A haematoma forms around the site of the fracture during the 6-8 hours after injury
- Bone deprived of nutrients dies and tissue at the site becomes swollen, painful and inflamed
Explain what happens during Soft Procallus formation, and how long this process takes?
- Bone reconstruction begins with formation of a soft procallus (fibrocartilaginous callus) which bridges the broken bone ends and splints the bone.
- Macrophages remove dead bone fragments and then reduce the haematoma
- This process takes about 2-4 weeks
What are soft procallus (fibrocartilaginous callus) consist of?
- Collagen fibres
- Cartilage
Explain what happens during Bony Callus formation and how long this process takes
- Osteoblasts convert fibrocartilage into a spongy bone callus
- This process takes 1-4 months
Explain what happens during Bone remodelling
- Spongy bone is replaced by compact bone
- Removal of excess material from the exterior of the bone and within the bone cavity
- Fracture line disappears, evidence of the break remains
State five factors that could delay bone healing
- Tissue fragments between the bone ends that haven’t been removed by phagocytes
- Deficient blood supply
- Poor alignment of the bone ends
- Continued mobility of bone ends
- Illness, malnutrition, drugs, aging
Explain what happens to bone mass over the lifespan
- From birth to adolescence bone deposit exceeds bone resorption.
- In females, bone loss begins after age 30. It accelerates greatly after age 45 which is related to reducing oestrogen levels during and following menopause
- In males, bone loss begins at age 60 as testosterone levels decline after age 55
Why is the loss of bone density not effect males as much as females?
Since males have a heavier skeleton than females
When does bone deposit exceed bone resorption?
From birth to adolescence, bone deposit exceeds bone resorption
When does bone resorption exceed bone deposit?
As we age, bone resorption will exceed bone deposit
State the main influence of bone resorption in females
Related to reduced oestrogen levels during and following menopause
State five factors that determine bone mass
- Genetic Factors
- Oestrogen levels
- Exercise
- Calcium intake and absorption
- Environmental factors
Define osteoporosis
Disease in which bone resorption exceeds bone deposit. There is significant loss of bone mass (bone density) and impaired structural integrity of bone
State who is most affected by Osteoporosis and explain why
Post-menopausal women because the production of oestrogen (also known as estrogen) levels (which protect women from the disease) is decreased.
What are Four age related changes of the skeletal system?
- Bone becomes more brittle and prone to fracture
- Articular cartilages diminish and thins
- Height is reduced
- Rigidity of the thoracic cage as costal cartilage ossifies
Describe what happens during “Bone becomes more brittle and prone to fracture”?
- Due to reduction in bone mass and density - this results from demineralisation of bone (loss of calcium and other minerals from the extracellular matrix)
- Reduction in collagen due to decreased synthesis of collagen
Describe what happens during “Articular cartilages diminish and thins”?
Bones move against one another and lead to rough bony growths (leads to osteoarthritis causing pain and decreased mobility)
Describe how “Height is reduced”
- Due to compression of the intervertebral discs (through fluid loss)
- Due to osteoporosis of the vertebrae
Describe what happens during “Rigidity of the thoracic cage as costal cartilage ossifies”
Produces shallow breathing resulting in less efficient gas exchange
