1.3 Flashcards
(25 cards)
- What percentage of adult height is determined by fetal growth and which factors influence it?
Fetal growth contributes approximately 30% of adult height, and it is influenced by the uterine environment, maternal nutrition, and hormonal factors.
- What factors determine infantile growth, and what percentage of adult height does it represent?
Infantile growth accounts for about 15% of adult height and is mainly determined by nutrition, good health and happiness, and thyroid hormones.
- During childhood, what primarily drives growth, and what percentage of adult height is achieved in this phase?
Childhood growth, which contributes roughly 40% of adult height, is primarily driven by growth hormone.
- What key factors influence pubertal growth, and what is its contribution to adult height?
Pubertal growth adds around 15% of adult height and is influenced by thyroid hormones, testosterone, estrogen, genes, growth hormone, and overall health.
- How does the uterine environment affect overall growth during the fetal stage?
The uterine environment affects fetal growth by providing essential nutrients and hormones, which set the stage for approximately 30% of the eventual adult height.
- What is mechanobiology?
Mechanobiology is the study of how biological systems respond to physical forces, integrating the effects of mechanical strain from the organism level down to the subcellular level.
- How do cells sense mechanical forces in the context of mechanobiology?
Cells sense mechanical forces through specialized mechanosensors, responses to fluid flow, compression of the extracellular matrix, and excitation signals at subcellular scales.
- What is Wolff’s Law and why is it significant in the context of bone development?
Wolff’s Law, or the law of transformation of bone, states that bone structure adapts to the loads it is placed under; this principle underpins how mechanical stress influences bone remodeling and architecture.
- How do long bones grow through the growth plate in post-natal development?
Long bones grow via endochondral ossification at the growth plate, which involves sequential steps of chondrocyte proliferation, hypertrophy, calcification of the cartilage matrix, degradation and vascular invasion, followed by new bone formation by osteoblasts.
- What role do chondrocytes play in the growth plate during longitudinal bone growth?
Chondrocytes in the growth plate proliferate and subsequently enlarge (hypertrophy), then calcify and undergo apoptosis, providing the template that is later replaced by bone tissue.
- What sequence of events characterizes endochondral ossification in long bone development?
The process includes chondrocyte proliferation, hypertrophy, calcification of the cartilage, matrix degradation with vascular invasion, and new bone formation on the calcified cartilage remnants.
- How do joints change as a child grows into adulthood?
At birth, joints are largely cartilaginous. With growth, the epiphyses ossify and the articular cartilage thickens, developing distinct zonal organizations that maintain the joint as a smooth, durable structure.
- What factors contribute to the thickening of articular joint cartilage during growth?
Hormones such as IGF-1 and BMP, along with mechanical loading, promote chondrocyte hypertrophy and increased extracellular matrix (ECM) deposition, leading to a thicker and more organized articular cartilage.
- What are the distinct zones found in mature articular cartilage?
Mature articular cartilage is organized into a superficial zone (parallel fibers), a transitional zone (random fiber orientation), and a deep zone (with perpendicular fibers), separated from the calcified cartilage by a tidemark.
- What are the three main muscle types and their primary functions?
The three main muscle types are skeletal muscle (controls voluntary movements and is attached to the skeleton), cardiac muscle (involuntary and forms the heart), and smooth muscle (involuntary and found within organs and blood vessels).
- How does post-natal skeletal muscle growth predominantly occur?
Post-natal skeletal muscle growth mainly occurs through hypertrophy, where existing muscle fibers increase in volume rather than by an increase in the number of fibers.
- What role do satellite cells play in post-natal skeletal muscle development?
Satellite cells are muscle stem cells that, when activated, proliferate and fuse with existing muscle fibers to provide additional nuclei, which is essential for muscle fiber hypertrophy and repair.
- Why is the addition of new nuclei important during skeletal muscle hypertrophy?
The addition of new nuclei from satellite cells helps maintain a healthy nuclear-to-cytoplasmic ratio, which is critical for efficient protein synthesis and proper muscle function as fibers enlarge.
- How do bones respond to increased mechanical load?
Bones respond by remodeling; osteoblasts are stimulated to form new bone, while the balance between collagen (providing elasticity) and hydroxyapatite minerals (providing rigidity) is maintained to resist compressive forces.
- In what way does articular cartilage respond to mechanical loading?
Moderate mechanical loading stimulates chondrocytes to produce more extracellular matrix components like collagen and proteoglycans, which maintain cartilage structure, whereas excessive load can lead to degeneration and osteoarthritis.
- What is the musculoskeletal response of skeletal muscle when subjected to increased load?
Skeletal muscle experiences hypertrophy, characterized by an increase in fiber diameter and recruitment of additional nuclei from satellite cells; conversely, disuse leads to atrophy.
- How does mechanical loading overall contribute to maintaining musculoskeletal integrity?
Mechanical loading triggers adaptive responses in bone, joint cartilage, and muscle tissue, promoting structural remodeling and strength that align with functional demands.
- What are the main determinants of childhood growth rates mentioned in the lecture?
Childhood growth rates depend on a combination of nutritional status, hormonal factors (like growth hormone, thyroid hormones, and sex hormones), genetic predispositions, and overall health and wellbeing.
- How does mechanobiology connect the concepts of biology and physics in musculoskeletal development?
Mechanobiology explores how physical forces—from macroscopic loads to nanoscale interactions—affect biological tissues by altering cell behavior, tissue structure, and molecular signaling pathways.
