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Questions and Answers
What are the four components of the skeletal system?
What are the four components of the skeletal system?
Which of the following is NOT a function of bones?
Which of the following is NOT a function of bones?
How many bones are typically in an adult human body?
How many bones are typically in an adult human body?
206
What substance is primarily stored in the marrow cavities of bones?
What substance is primarily stored in the marrow cavities of bones?
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What type of bone is primarily found in the epiphyses of long bones?
What type of bone is primarily found in the epiphyses of long bones?
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The _____ is a delicate connective tissue covering the inner bony surface of the shaft.
The _____ is a delicate connective tissue covering the inner bony surface of the shaft.
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The epiphyseal line is a remnant of the epiphyseal plate seen in a young, growing bone.
The epiphyseal line is a remnant of the epiphyseal plate seen in a young, growing bone.
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Which category do the bones of the wrist and ankle belong to?
Which category do the bones of the wrist and ankle belong to?
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What are the two main types of bone tissue?
What are the two main types of bone tissue?
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The _____ canals run lengthwise through the bony matrix, carrying blood vessels and nerves.
The _____ canals run lengthwise through the bony matrix, carrying blood vessels and nerves.
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What process involves the replacement of hyaline cartilage with bone?
What process involves the replacement of hyaline cartilage with bone?
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Study Notes
The Skeletal System
- The skeletal system consists of bones, cartilage, tendons and ligaments.
- It performs several functions:
- Support: Supports the body's weight - the bones in the legs support the trunk when standing, and the rib cage supports the thoracic wall.
- Protection: Protects vital organs, such as the spinal cord (surrounded by vertebrae), and the heart and lungs (protected by the rib cage).
- Movement: Muscles attached to bones via tendons use bones as levers to move the body.
- Mineral Storage: Bones store minerals, such as calcium and phosphorus.
- Blood Cell Formation: Blood cells are produced within the marrow cavities of certain bones, a process called hematopoiesis.
Bone Classification
- Human skeletons have 206 bones in adulthood.
- Bone tissue is classified into two types:
- Compact Bone: Dense and smooth, mainly composed of matrix and cells.
- Spongy Bone: Appears porous and contains numerous small spaces filled with marrow.
Bone Classification by Shape
- Bones are categorized by their shape:
- Long Bones: Longer than wide, possess a shaft (diaphysis) with enlarged ends (epiphyses), mainly compact bone with spongy bone at the ends. Examples: Bones of the limbs (except patella, wrist, and ankle bones).
- Flat Bones: Thin, flattened, and curved, mainly composed of spongy bone with an outer layer of compact bone. Examples: Most skull bones, ribs, and sternum.
- Short Bones: Roughly cube-shaped, mainly composed of spongy bone with an outer layer of compact bone. Examples: Wrist and ankle bones, sesamoid bones like the patella.
- Irregular Bones: Bones that don't fit into the above categories, often complex shapes. Examples: Vertebrae, pelvic girdle, and facial bones.
Structure of Bone
- A long bone consists of a diaphysis (shaft) composed of compact bone, and epiphyses (ends).
- Periosteum: A fibrous connective tissue membrane that covers the diaphysis, secured to the bone by Sharpey's fibers.
- Epiphyseal Plate: A cartilaginous growth plate present in young, growing bones. It is replaced by bone at the end of puberty, leaving behind the epiphyseal line.
- Endosteum: A delicate connective tissue that lines the inner bony surface of the shaft.
- Medullary Cavity: Cavity within the shaft that stores red marrow (responsible for blood cell production) in children and yellow marrow (stores fat) in adults.
Microscopic Anatomy
- Spongy Bone: Composed of small needle-like pieces called trabeculae.
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Compact Bone: Contains osteocytes (mature bone cells) located within the bone matrix in tiny cavities called lacunae.
- Lacunae are arranged in concentric circles called lamellae around central canals (Haversian canals).
- Central canals run lengthwise through the bone, carrying blood vessels & nerves.
- Canaliculi: Tiny canals radiating outwards from central canals connecting to all lacunae.
- Perforating Canals (Volkmann's Canals): Connect the central canals to the outside of the bone.
- Bone Matrix: Composed of calcium salts (hardness) and organic parts (collagen fibers - for flexibility and tensile strength).
Bone Formation, Growth and Remodeling
- The skeleton is formed from cartilage and bone.
- In embryos, the skeleton is primarily cartilaginous.
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Ossification: Process of bone formation.
- Hyaline cartilage model is covered by osteoblasts (bone-building cells).
- The enclosed cartilage model is then replaced by bone.
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Description
Test your knowledge on the human skeletal system, including its functions and bone classification. This quiz covers important aspects such as support, protection, and blood cell formation. Explore the differences between compact and spongy bone tissue.
