Week 29 / Muscle, Joints & Bones 1 Flashcards
What are the main parts of the skeletal system?
✅ Answer:
Bones (skeleton)
Joints
Cartilages
Ligaments
What are the two divisions of the skeletal system?
✅ Answer:
Axial skeleton – Bones around the body axis
Appendicular skeleton – Bones of the limbs and girdles
What are examples of bones in the axial skeleton?
✅ Answer: Skull bones, hyoid, ribs, sternum, vertebrae.
What are examples of bones in the appendicular skeleton?
✅ Answer:
Clavicle (collar bone)
Humerus (upper arm bone)
Radius & Ulna (forearm bones)
Femur (thigh bone)
What are the Functions of Bones ?
1) Support of the body
2) Protection of soft organs
3) Assistance in movement
4) Mineral homeostasis
5) Blood cell production
6) Triglyceride storage
How many bones are in the adult human skeleton?
✅ Answer: The adult skeleton has 206 bones.
What are the two basic types of bone tissue?
✅ Answer:
Compact bone tissue
Spongy bone tissue
What characterizes compact bone tissue?
✅ Answer: Compact bone tissue contains few spaces and is arranged in repeating structural units called osteons or Haversian systems.
What characterizes spongy bone tissue?
✅ Answer: Spongy bone tissue is formed of trabeculae and does not contain osteons.
What is an osteon (Haversian system)?
✅ Answer: An osteon (Haversian system) is the structural unit of compact bone.
What is the function of the central (Haversian) canal in the osteon?
✅ Answer: The central (Haversian) canal carries blood vessels, nerves, and lymphatic vessels.
What is the role of the perforating (Volkmann’s) canal?
✅ Answer: The perforating (Volkmann’s) canal runs perpendicular to the central canal and carries blood vessels and nerves.
What are long bones, and can you give examples?
✅ Answer: Long bones are typically longer than wide, with a shaft and heads at both ends, mostly containing compact bone.
Examples: Femur, humerus.
What are short bones, and can you give examples?
✅ Answer: Short bones are generally cube-shaped and mostly contain spongy bone.
Examples: Carpals, tarsals.
What are flat bones, and can you give examples?
✅ Answer: Flat bones are thin, flattened, and usually curved, with thin layers of compact bone surrounding a layer of spongy bone.
Examples: Sternum (breastbone), scapulae (shoulder blades), ribs, most skull bones.
What are irregular bones, and can you give examples?
✅ Answer: Irregular bones have irregular shapes and do not fit into other bone classification categories.
Examples: Vertebrae, hip bones.
What is the diaphysis of a long bone?
✅ Answer: The diaphysis is the shaft of the bone, composed mainly of compact bone.
What is the epiphysis of a long bone?
✅ Answer: The epiphysis refers to the ends of the bone, composed mostly of spongy bone (cancellous bone).
What is the metaphysis of a long bone?
✅ Answer: The metaphysis is the region where the diaphysis joins the epiphyses in a mature bone.
What is the function of articular cartilage in a long bone?
✅ Answer: Articular cartilage covers the external surface of the epiphyses and decreases friction at joint surfaces.
What type of cartilage makes up the articular cartilage?
✅ Answer: Hyaline cartilage.
What is the periosteum, and what is its function?
✅ Answer: The periosteum is the outer covering of the diaphysis, made of fibrous connective tissue. It protects the bone and serves as an attachment point for tendons and ligaments.
What is the endosteum, and where is it located?
✅ Answer: The endosteum is a membrane lining the medullary cavity (the hollow cavity inside long bones).
What are Sharpey’s fibers, and what is their role?
✅ Answer: Sharpey’s fibers are collagen fibers that secure the periosteum to the underlying bone.
What is the function of arteries in a long bone?
✅ Answer: Arteries supply bone cells with oxygen and nutrients to maintain bone health.
What is the medullary cavity, and where is it located?
What does the medullary cavity contain in adults?
What does the medullary cavity contain in infants?
✅ Answer: The medullary cavity is the hollow space inside the shaft (diaphysis) of a long bone.
✅ Answer: In adults, it contains yellow marrow, which is mostly fat.
✅ Answer: In infants, it contains red marrow, which is responsible for blood cell formation (hematopoiesis).
What are bone markings?
✅ Answer: Bone markings are surface features of bones that serve as attachment sites for muscles, tendons, and ligaments or act as passages for nerves and blood vessels.
What are projections and processes in bone markings?
✅ Answer: Projections and processes are bone features that grow out from the bone surface.
What are osteoblasts, and what is their function?
✅ Answer: Osteoblasts are bone-forming cells that help build new bone tissue.
What are depressions or cavities in bone markings?
✅ Answer: Depressions or cavities are indentations in the bone surface.
What are osteocytes, and what is their role?
✅ Answer: Osteocytes are mature bone cells that maintain bone structure and mineral content.
What are osteoclasts, and what is their function?
✅ Answer: Osteoclasts are bone-destroying cells that break down bone matrix for remodeling and calcium release.
What is bone remodeling, and which cells are involved?
✅ Answer: Bone remodeling is the continuous process of bone renewal involving both osteoblasts (building bone) and osteoclasts (breaking down bone).
What enzyme do osteoblasts secrete, and what is its role?
✅ Answer: Osteoblasts secrete alkaline phosphatase, which promotes the deposition of calcium phosphate salts to calcify the bone.
What are osteoblasts, and what do they produce?
✅ Answer: Osteoblasts are active bone-forming cells that produce collagenase and bone matrix.
What happens to osteoblasts after bone matrix formation?
✅ Answer: Once the bone matrix is formed and calcified, osteoblasts become embedded in the bone and transform into osteocytes (mature bone cells).
How do osteoclasts remove bone matrix?
✅ Answer: Osteoclasts use phagocytosis to dissolve bone salts and break down the bone structure.
What are osteoclasts, and what is their function?
✅ Answer: Osteoclasts are multinucleated cells responsible for bone resorption, breaking down bone matrix and releasing calcium and phosphate ions into circulation.
What is bone formation called?
✅ Answer: Bone formation is called ossification.
What are the key stages of bone development?
✅ Answer:
Initial bone development (embryo & fetus)
Bone growth into adulthood
Bone remodeling (replacement of old bone)
Bone repair (fracture healing)
What is the mesenchyme model, and when does ossification begin?
✅ Answer: Mesenchyme is early connective tissue that forms the initial skeleton, which begins ossification at 6 weeks of embryonic life.
What are the two types of ossification, and how do they differ?
✅ Answer:
Intramembranous ossification: Bone forms directly within sheets of mesenchyme (e.g., skull bones, mandible, clavicle).
Endochondral ossification: Bone develops from hyaline cartilage (e.g., most bones in the body).
What are the four main steps of intramembranous ossification?
✅ Answer:
Development of the ossification center
Mesenchyme cells become osteogenic cells, then osteoblasts
Osteoblasts secrete organic bone matrix
Calcification
Osteoblasts become osteocytes in lacunae
Osteocytes extend cytoplasmic processes to connect with each other
Deposition of calcium & mineral salts begins
Formation of trabeculae
Blood vessels grow into the developing bone
Spongy bone and red bone marrow form
Development of the periosteum
The outer mesenchyme layer becomes periosteum, covering the bone
What is intramembranous ossification?
✅ Answer: Intramembranous ossification is bone formation within sheets of mesenchyme without a cartilage model.
What is endochondral ossification?
✅ Answer: Endochondral ossification is bone formation from a cartilage model, where mesenchyme first forms hyaline cartilage, which is later replaced by bone.
What is the primary skeletal material in embryos?
✅ Answer: Hyaline cartilage
What are the six main steps of endochondral ossification?
✅ Answer:
1️⃣ Development of cartilage model
Mesenchyme cells → chondroblasts
Chondroblasts secrete cartilage matrix forming the “bone model”
2️⃣ Growth of cartilage model
Chondroblasts → chondrocytes
Chondrocytes enlarge, cartilage matrix calcifies
Chondrocytes die, leaving lacunae
3️⃣ Development of primary ossification center
Nutrient artery enters cartilage
Perichondrium → periosteum, osteoblasts form spongy bone
4️⃣ Development of medullary cavity
Osteoclasts break down spongy bone to form marrow cavity
Compact bone collar forms around the diaphysis
5️⃣ Development of secondary ossification centers
Nutrient arteries enter epiphyses, osteoblasts form spongy bone
Occurs around birth
6️⃣ Formation of articular cartilage & epiphyseal plate
Hyaline cartilage at bone ends becomes articular cartilage
Epiphyseal plate remains until bone growth stops
What happens to the cartilage in the human skeleton during development?
✅ Answer: Much of the cartilage is replaced by bone through ossification
Where does cartilage remain in the adult skeleton?
✅ Answer:
Bridge of the nose
Parts of the ribs
Joints
What role do epiphyseal plates play in bone growth?
✅ Answer: Epiphyseal plates allow for the growth of long bones during childhood by forming new cartilage, which is then ossified and replaced by bone.
What happens to the cartilage in the epiphyseal plates?
✅ Answer:
New cartilage is continuously formed at the epiphyseal plates.
Older cartilage becomes ossified and is replaced by bone.
What hormones are involved in bone resorption and what is their effect?
✅ Answer:
Parathyroid hormone (PTH): Increases osteoclast activity, leading to bone resorption and increases blood Ca²⁺ levels.
How do bones change during growth?
✅ Answer:
Bones lengthen until growth stops (when epiphyseal plates close).
Bones remodel, changing shape and growing in width.
What hormones are involved in bone deposition and what is their effect?
✅ Answer:
Calcitonin: Decreases osteoclast activity, promoting bone deposition and lowering blood Ca²⁺ levels.
How are blood calcium levels controlled in bone homeostasis?
✅ Answer: Through negative feedback loops, regulated by PTH (increases Ca²⁺) and calcitonin (decreases Ca²⁺).
What happens to bone tissue strength under mechanical stress?
✅ Answer:
Under stress, bone becomes stronger through increased deposition of mineral salts and collagen fibers by osteoblasts.
Without stress, bone resorption outpaces formation, weakening the bone.
Question 5:
What are the main mechanical stresses on bones?
✅ Answer:
Pull of skeletal muscles
Pull of gravity
What minerals are necessary for bone development and growth?
✅ Answer: Calcium (Ca), Phosphorus (P), and Magnesium (Mg)
Which vitamins are important for bone development and growth?
✅ Answer: Vitamins A, C, and D
Which hormones are involved in bone growth before puberty?
✅ Answer:
hGH (human Growth Hormone)
Insulin-like Growth Factors (IGFs)
Which hormones are required for bone development and growth after puberty?
✅ Answer:
Thyroid hormone
Insulin
Sex hormones (e.g., estrogen, testosterone) for the adolescent growth spurt
What role does weight-bearing activity play in bone development?
✅ Answer: Weight-bearing activity helps promote bone strength by stimulating bone remodeling and mineralization.
What is the effect of a Vitamin A deficiency on bone development?
✅ Answer: It retards bone development.
What happens when there is a Vitamin C deficiency?
✅ Answer: It results in fragile bones due to impaired collagen formation.
What is the impact of insufficient Growth Hormone on bone growth?
✅ Answer: It causes dwarfism, characterized by stunted bone growth.
What are the effects of a Vitamin D deficiency on bones?
✅ Answer: It leads to rickets in children and osteomalacia in adults, both of which cause softening and weakening of bones.
What are the effects of excessive Growth Hormone on bone development?
✅ Answer: It leads to gigantism in children (excessive growth) and acromegaly in adults (abnormal growth of bones and tissues).
What happens if there is insufficient thyroid hormone during bone growth?
✅ Answer: It delays bone growth and can impair skeletal development.
How do sex hormones influence bone growth?
✅ Answer: They promote bone formation and stimulate the ossification of epiphyseal plates, contributing to the end of bone growth during puberty.
What role does physical stress play in bone development?
✅ Answer: Physical stress stimulates bone growth and strengthens bone tissue
How do glucocorticoids affect bone health?
✅ Answer: They activate osteoclasts, promoting bone resorption and weakening bones.
