Musculoskeletal System (Skeletal Tissue + Bone Development) Flashcards
Name the function of osteoblasts?
Bone Formation: Osteoblasts are primarily responsible for synthesizing and depositing the organic components of the bone matrix, including collagen fibres and various proteins. They also initiate the process of mineralization by depositing calcium and phosphate ions, which then crystallize to form hydroxyapatite, the mineral component of bone.
Bone Remodelling: Osteoblasts play a role in the ongoing process of bone remodelling. They work in concert with osteoclasts, which are responsible for bone resorption (breaking down bone tissue). Osteoblasts help maintain the balance between bone formation and resorption, ensuring that bones remain healthy and adapt to changing mechanical stresses.
Repair and Healing: Osteoblasts are involved in bone repair and healing processes. When a bone is fractured or damaged, osteoblasts are among the cells that migrate to the site of injury to lay down new bone tissue and assist in the healing process.
Regulation of Mineral Homeostasis: Osteoblasts also contribute to the regulation of calcium and phosphate levels in the bloodstream. They can release calcium from bone tissue into the bloodstream when needed to maintain proper mineral balance.
Name the function of osteoclasts?
Bone Resorption: Osteoclasts are primarily known for their role in bone resorption, which is the process of breaking down bone tissue. They secrete enzymes and acids that dissolve the mineral matrix of bone (hydroxyapatite) and degrade the organic components, such as collagen fibres. This process releases calcium and phosphate ions into the bloodstream.
Bone Remodelling: Osteoclasts are essential for the continuous remodelling of bone tissue. They work in coordination with osteoblasts, which are responsible for bone formation. This balanced activity ensures that bones remain dynamic, adapting to changing mechanical stresses and maintaining their integrity.
Calcium Regulation: Osteoclasts play a role in regulating calcium levels in the bloodstream. By breaking down bone tissue, they release calcium into the blood when the body requires it for various physiological processes, such as muscle contraction, nerve function, and blood clotting.
Bone Repair: Osteoclasts are involved in the early stages of bone repair and healing. After an injury or fracture, they help remove damaged or dead bone tissue to make way for the action of osteoblasts, which deposit new bone tissue.
What is the difference between trabecular and cortical bone tissue?
In summary, trabecular bone is characterized by its spongy, porous structure and is found in the inner core of bones, contributing to metabolic functions and blood cell production. Cortical bone, on the other hand, is dense and compact, forming the outer shell of bones and providing mechanical strength and protection.
What is the function of periosteum?
the periosteum is a vital structure that provides protection, nutrition, and support for bones while also participating in bone growth, repair, and regulation. It is an essential component of the skeletal system that contributes to the overall function and health of bones.
Which bones form from intramembranous ossification?
Intramembranous ossification is particularly important for forming the bones of the skull and facial skeleton, which need to be relatively lightweight yet strong to protect the brain and support facial structures. These bones develop directly from mesenchymal tissue, with osteoblasts depositing bone matrix within the membrane-like connective tissue, resulting in the formation of flat bones. Also clavicles and certain irregular bones and sesamoid bones
Which bones form from endochondral ossification?
Endochondral ossification is the primary method by which most bones in the human body develop and grow in length. It involves the replacement of the cartilaginous model with bone tissue during fetal development and throughout childhood and adolescence.
What is appositional bone growth and where does it occur?
Appositional bone growth is essential for maintaining the structural integrity of bones and adapting them to the mechanical demands placed on them during physical activity and growth. It is particularly active during periods of growth and can continue throughout life to some extent as bones undergo remodeling and repair.
Appositional bone growth occurs at the periosteal surface of bones. The periosteum is the tough, fibrous membrane that covers the outer surface of bones. Osteoblasts, which are bone-forming cells, are found in the periosteum
The epiphyseal plate consists of which type of cartilaginous tissue?
The epiphyseal plate, also known as the growth plate, consists of hyaline cartilaginous tissue. This hyaline cartilage is responsible for the longitudinal growth of bones during childhood and adolescence. The epiphyseal plate is located between the diaphysis (shaft) and epiphysis (end) of a long bone.
What are the major differences in tissue composition between bone and cartilaginous tissue?
Matrix Composition:
Bone: Bone tissue has a matrix that consists of both organic and inorganic components. The organic component includes collagen fibers, glycoproteins, and proteoglycans. The inorganic component is primarily hydroxyapatite, a crystalline structure composed of calcium and phosphate ions, which gives bone its hardness.
Cartilage: Cartilage tissue has a matrix primarily composed of a specialized type of collagen called type II collagen. It also contains proteoglycans, which are large molecules made up of proteins and carbohydrates. The matrix in cartilage is flexible and provides resistance to compression.
Vascularity:
Bone: Bone tissue is highly vascular, meaning it has a rich network of blood vessels. Blood vessels supply nutrients, oxygen, and remove waste products from bone tissue.
Cartilage: Cartilage is avascular, meaning it lacks blood vessels. It relies on diffusion from nearby connective tissues for its nutrient supply and waste removal.
Cell Types:
Bone: Bone tissue contains several cell types, including osteoblasts (bone-forming cells), osteocytes (mature bone cells), and osteoclasts (bone-resorbing cells).
Cartilage: Cartilage tissue primarily contains chondrocytes, which are the only cell type found within mature cartilage. Chondrocytes are responsible for maintaining the cartilage matrix.
Mineralization:
Bone: Bone tissue undergoes mineralization, which is the deposition of calcium and phosphate ions to harden the matrix and give bone its strength.
Cartilage: Cartilage tissue remains unmineralized, maintaining its flexibility and resilience. It does not undergo the same mineralization process as bone.
If the activity of osteoblasts exceeds the activity of osteoclasts, how is the mass of the bone affected?
An imbalance in either direction—excessive bone resorption (osteoclast activity) or excessive bone formation (osteoblast activity)—can lead to bone-related disorders, such as osteoporosis or excessive bone growth disorders. Proper nutrition, weight-bearing exercise, and hormonal regulation are factors that help maintain this balance in bone remodelling and turnover.
What event must occur before bone tissue can form inside the cartilage model of endochondral ossification?
Before bone tissue can form inside the cartilage model of endochondral ossification, a crucial event must occur: the cartilage model must first calcify. This calcification of cartilage is a necessary step in the process of transforming cartilage into bone.
Why do the chondrocytes start dying in the zone of retrogression of the epiphyseal plate?
Calcification of the Matrix: In the zone of hypertrophy, chondrocytes mature and enlarge, and they actively produce cartilage matrix. However, this matrix eventually becomes calcified, meaning that calcium and phosphate ions are deposited within it. As the matrix calcifies, it becomes rigid and less suitable for maintaining living cells.
Nutrient Diffusion: Unlike other tissues, cartilage is avascular, meaning it lacks blood vessels. Chondrocytes in the deeper layers of the cartilage model rely on nutrient and oxygen diffusion from nearby blood vessels. As the matrix calcifies, it hinders the diffusion of nutrients to these cells, leading to a decrease in their metabolic activity.
Osteoblast Invasion: In the zone of hypertrophy and degeneration, blood vessels and osteoblasts (bone-forming cells) invade the area from the surrounding tissues. Osteoblasts are responsible for replacing the cartilage with bone tissue. The presence of these cells and the initiation of bone formation necessitate the removal of the calcified cartilage matrix.
Space for Bone Deposition: To make space for the deposition of bone tissue by osteoblasts, the cartilage matrix must be broken down and removed. Chondrocyte apoptosis in this zone allows for the creation of space within the matrix for osteoblast activity and the eventual formation of bone tissue.
Transition to Bone: Chondrocyte apoptosis in the zone of hypertrophy is a natural part of the process of transitioning from cartilage to bone. The death of chondrocytes is followed by the resorption of the calcified cartilage matrix and the deposition of bone matrix by osteoblasts, resulting in the formation of trabecular bone.
Why do osteoclasts resorb the newly formed bone in the zone of resorption of the epiphyseal plate?
In summary, osteoclasts play a crucial role in the balanced development and growth of bones by resorbing newly formed bone tissue in the zone of resorption of the epiphyseal plate. This process helps maintain the width and functionality of the growth plate, ensures proper adaptation to mechanical forces, and contributes to the formation of mature bone tissue.
What causes the epiphyseal plate to close? How does this happen in terms of tissue structure?
The closure of the epiphyseal plate occurs when the proliferation and hypertrophy of chondrocytes diminish, leading to the cessation of longitudinal bone growth and the complete replacement of cartilage with bone in the epiphyseal plate region.
Consider whether bone or cartilaginous tissue heals quicker and why
Bone heals quicker than cartilaginous tissue as bone is highly vascular and takes 6-8 weeks to heal. Cartilaginous tissue is avascular and relies on diffusion of nutrients from surrounding tissues. Takes approx 12 weeks
Why does bone tissue not use interstitial growth as a mechanism of growth and expansion?
Interstitial growth only at epiphyseal plates. Calcification in bones causes chondrocytes to die, so cartilage cannot form in the bone, leading to no interstitial growth in bones
What is the reason for height difference between sexes?
Males produce testosterone which promotes longitudinal bone growth and puberty can continue until 25. Females produce oestrogen and progesterone which fuses epiphyseal plates and undergo puberty much earlier, stopping longitudinal growth much sooner
Why is perichondrium absent in fibrocartilage but present in most other cartilage constructs?
Growth happens from outside in. No perichondrium means less blastocysts therefore can not develop. This helps fibrocartilage retain structure. Perichondrium source of nutrition + growth
