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Questions and Answers
What is the primary function of the vertebrae in the skeleton?
What is the primary function of the vertebrae in the skeleton?
How many bones does the adult human skeleton typically contain?
How many bones does the adult human skeleton typically contain?
What characteristic differentiates compact bone from spongy bone?
What characteristic differentiates compact bone from spongy bone?
Which of the following statements about the rib cage is correct?
Which of the following statements about the rib cage is correct?
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What mineral is predominantly stored in bone tissue?
What mineral is predominantly stored in bone tissue?
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How do skeletal muscles interact with bones?
How do skeletal muscles interact with bones?
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What is one characteristic of spongy bone?
What is one characteristic of spongy bone?
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What is the role of fat in the internal cavity of bones?
What is the role of fat in the internal cavity of bones?
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What is the first major event in the repair of bone fractures?
What is the first major event in the repair of bone fractures?
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What occurs after the hematoma is formed during bone fracture repair?
What occurs after the hematoma is formed during bone fracture repair?
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What type of tissue replaces the fibrocartilage callus in the later stages of bone fracture healing?
What type of tissue replaces the fibrocartilage callus in the later stages of bone fracture healing?
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How does bone remodeling occur in response to a fracture?
How does bone remodeling occur in response to a fracture?
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What is the purpose of the fibrocartilage callus in fracture healing?
What is the purpose of the fibrocartilage callus in fracture healing?
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Which cellular process occurs after the formation of new capillaries during fracture repair?
Which cellular process occurs after the formation of new capillaries during fracture repair?
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What major structure of the body does the axial skeleton include?
What major structure of the body does the axial skeleton include?
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Which part is NOT included in the axial skeleton?
Which part is NOT included in the axial skeleton?
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What is the role of calcium salts in bone structure?
What is the role of calcium salts in bone structure?
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Which cells are primarily responsible for the formation of bone?
Which cells are primarily responsible for the formation of bone?
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What is ossification?
What is ossification?
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During what phase do osteoblasts cover the hyaline cartilage model with bone matrix?
During what phase do osteoblasts cover the hyaline cartilage model with bone matrix?
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What remains of the hyaline cartilage in children after ossification?
What remains of the hyaline cartilage in children after ossification?
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What is the function of collagen fibers in bone?
What is the function of collagen fibers in bone?
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What happens to the enclosed hyaline cartilage model during fetal development?
What happens to the enclosed hyaline cartilage model during fetal development?
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What structure connects the outside of the bone to its interior?
What structure connects the outside of the bone to its interior?
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At what age do children's bones begin to replace red marrow with yellow marrow?
At what age do children's bones begin to replace red marrow with yellow marrow?
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What primarily causes the hardness of bones?
What primarily causes the hardness of bones?
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What is the role of the lacunae in compact bone?
What is the role of the lacunae in compact bone?
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Which structure is considered the functional unit of compact bone?
Which structure is considered the functional unit of compact bone?
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How do canaliculi contribute to bone health?
How do canaliculi contribute to bone health?
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What type of bone primarily contains red marrow in adults?
What type of bone primarily contains red marrow in adults?
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What do trabeculae in spongy bone primarily facilitate?
What do trabeculae in spongy bone primarily facilitate?
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What is primarily found in the open spaces of spongy bone?
What is primarily found in the open spaces of spongy bone?
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What role do osteoblasts play in the growth of bone?
What role do osteoblasts play in the growth of bone?
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Which hormones are most important in controlling bone growth?
Which hormones are most important in controlling bone growth?
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What happens to epiphyseal plates at the end of adolescence?
What happens to epiphyseal plates at the end of adolescence?
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How does old cartilage in the bone structure change?
How does old cartilage in the bone structure change?
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What is the result of the combined action of osteoblasts and osteoclasts on long bones?
What is the result of the combined action of osteoblasts and osteoclasts on long bones?
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Which factor is NOT involved in bone remodeling?
Which factor is NOT involved in bone remodeling?
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What is the main function of parathyroid hormones in relation to bones?
What is the main function of parathyroid hormones in relation to bones?
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What is the role of articular cartilages?
What is the role of articular cartilages?
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Study Notes
Bone Classification and Structure
- The adult human skeleton comprises 206 bones.
- There are two types of bone tissue: compact bone and spongy bone.
- Compact bone is dense and appears smooth and homogeneous.
- Calcium ions and salts are deposited in compact bone, contributing to its hardness.
- Spongy bone has a spiky, open structure resembling a sponge.
- Even though it appears porous, spongy bone is not soft.
- The holes in spongy bone are called Haversian canals and contain blood vessels, allowing them to pass through.
- Children's bones contain red marrow until the age of 6 or 7 when it is gradually replaced with yellow marrow.
- In adult bones, red marrow is confined to cavities in the spongy bone of the axial skeleton, hip bones, and the ends of long bones
- Bone is lightweight and resists tension and other forces.
- Organic components (collagen fibers) provide flexibility and tensile strength to bone.
- Calcium salts deposited in the bone matrix make it hard and resist compression.
Microscopic Anatomy of Bone
- Under a microscope, spongy bone is composed of small needlelike pieces of bone called trabeculae. These trabeculae enclose spaces which contain marrow, blood vessels, and nerves.
- In compact bone, mature bone cells (osteocytes) are located in tiny cavities within the bone matrix called lacunae.
- Lacunae are arranged in concentric circles called lamellae, surrounding central canals (also known as Haversian canals).
- An osteon or Haversian System is a complex consisting of a central canal, lamellae, and lacunae. It is the structural and functional unit of compact bone.
- Central canals run lengthwise through the bone matrix, carrying blood vessels and nerves to all parts of the bone.
- Tiny canals called canaliculi radiate outward from the central canals to all lacunae, forming a transportation system connecting bone cells for nutrient supply and waste removal.
- Perforating canals (Volkmann's canals) run perpendicular to the central canals, completing the communication pathway from the bone's exterior to its interior.
Bone Formation, Growth, and Remodeling
- Ossification is the process of bone formation.
- It occurs on hyaline cartilage models or fibrous membranes.
- Long bone growth has two main phases.
- During embryonic development, the skeleton is primarily made of hyaline cartilage.
- In young children, most cartilage is replaced by bone, remaining in isolated areas, including the bridge of the nose, parts of the ribs, and joints.
Phases of Long Bone Growth
- Osteoblasts (bone-forming cells) cover the hyaline cartilage model with bone matrix.
- Hyaline cartilage is completely covered by bone matrix, forming a bone "collar."
- During fetal development, cartilage is replaced by bone, leaving two regions in long bones: articular cartilages and epiphyseal plates.
- Articular cartilages cover bone ends.
- Epiphyseal plates are responsible for the elongation of long bones.
Bone Growth and Remodeling
- New cartilage forms continuously on the external face of articular cartilages and epiphyseal plates.
- Old cartilage is then broken down and replaced with bone matrix.
- Osteoblasts in the periosteum add bone matrix to the outside of the diaphysis, causing the bone to widen.
- Osteoclasts in the endosteum remove bone from the inner surface of the diaphysis, enlarging the medullary cavity.
- These processes happen at a similar rate, leading to an increase in long bone circumference.
- Bone growth is controlled by hormones like growth hormone and sex hormones.
- Bone growth ends during adolescence when epiphyseal plates are fully converted to bone.
- Parathyroid hormone ensures sufficient calcium in the blood.
- Bone is a dynamic tissue constantly undergoing remodeling.
- Bone remodeling is a response to changes in calcium ion levels in the blood and the migration of osteoblasts and osteoclasts.
Fracture Repair
- Repair of bone fractures involves four major events: hematoma formation, fibrocartilage callus formation, bony callus formation, and bone remodeling.
- When a bone breaks, blood vessels are ruptured, leading to a blood-filled swelling (hematoma).
- The hematoma deprives bone cells of nutrients, causing their death.
- A fibrocartilage callus forms consisting of cartilage matrix and bone matrix, acting as a splint.
- New capillaries and phagocytes replace dead tissue.
- The fibrocartilage callus is gradually replaced by a bony callus made of spongy bone.
- Bone remodeling occurs in response to mechanical stresses, forming a strong, permanent patch at the fracture site.
The Axial Skeleton
- The axial skeleton is divided into three parts: the skull, the vertebral column, and the thoracic cage.
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Description
This quiz covers the classification and structure of bones in the human skeleton. Learn about the two types of bone tissue, compact and spongy bone, as well as the functions of different bone components. Explore the anatomy and properties that contribute to the strength and flexibility of bones.
