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Questions and Answers
What is the function of synovial fluid?
What is the function of synovial fluid?
Which type of joint allows for rotational movement?
Which type of joint allows for rotational movement?
What role do bursae play in joint function?
What role do bursae play in joint function?
What is a meniscus specifically composed of?
What is a meniscus specifically composed of?
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What is the term for the outer lining of a bone?
What is the term for the outer lining of a bone?
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Which of the following structures surrounds and protects the joint primarily?
Which of the following structures surrounds and protects the joint primarily?
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Which part of the femur is known for forming its joint surface?
Which part of the femur is known for forming its joint surface?
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What type of bone tissue primarily makes up the interior of bones?
What type of bone tissue primarily makes up the interior of bones?
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What is contained within the medullary cavity?
What is contained within the medullary cavity?
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In bone structure, what is the significance of the metaphysis?
In bone structure, what is the significance of the metaphysis?
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What constitutes the majority of the bone mass?
What constitutes the majority of the bone mass?
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What role do collagen fibers play in bone structure?
What role do collagen fibers play in bone structure?
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Which type of marrow is found in the medullary cavity of adults?
Which type of marrow is found in the medullary cavity of adults?
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How much of the bone mass is made up of bone cells?
How much of the bone mass is made up of bone cells?
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What is the primary function of hydroxyapatite crystals in bones?
What is the primary function of hydroxyapatite crystals in bones?
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Which component lines the medullary cavity?
Which component lines the medullary cavity?
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What is the composition ratio of collagen fibers to hydroxyapatite in bone tissue?
What is the composition ratio of collagen fibers to hydroxyapatite in bone tissue?
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Which of the following structures is found at the ends of long bones?
Which of the following structures is found at the ends of long bones?
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What happens to osteoblast activity as people age?
What happens to osteoblast activity as people age?
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What results from the faster activity of osteoclasts compared to osteoblasts?
What results from the faster activity of osteoclasts compared to osteoblasts?
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Which term describes the loss of bone mass due to aging?
Which term describes the loss of bone mass due to aging?
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What is a characteristic of synovial joints?
What is a characteristic of synovial joints?
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How does aging affect the production of collagen in bone tissue?
How does aging affect the production of collagen in bone tissue?
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What type of cartilage connects cartilaginous joints?
What type of cartilage connects cartilaginous joints?
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Why do bones become porous in older women?
Why do bones become porous in older women?
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Which type of joint is primarily immovable?
Which type of joint is primarily immovable?
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What is the primary function of an osteocyte?
What is the primary function of an osteocyte?
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What type of cell is an osteoclast?
What type of cell is an osteoclast?
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What is the function of osteoprogenitor cells?
What is the function of osteoprogenitor cells?
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Which type of bone tissue is characterized as dense and solid, forming the walls of bones?
Which type of bone tissue is characterized as dense and solid, forming the walls of bones?
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What does the medullary cavity contain?
What does the medullary cavity contain?
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What distinguishes spongy bone from compact bone?
What distinguishes spongy bone from compact bone?
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What is the primary role of osteoblasts?
What is the primary role of osteoblasts?
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Which component of bone is specifically associated with the endosteum?
Which component of bone is specifically associated with the endosteum?
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What is the primary function of osteocytes in mature bone?
What is the primary function of osteocytes in mature bone?
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Which term describes the immature bone cells responsible for producing the matrix?
Which term describes the immature bone cells responsible for producing the matrix?
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Where are osteoprotegerin cells primarily located?
Where are osteoprotegerin cells primarily located?
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What is the role of osteoclasts in bone physiology?
What is the role of osteoclasts in bone physiology?
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Which of these processes is directly associated with osteoblasts?
Which of these processes is directly associated with osteoblasts?
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What is the significance of canaliculi in bone structure?
What is the significance of canaliculi in bone structure?
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What cellular lineage do osteoclasts share similarities with?
What cellular lineage do osteoclasts share similarities with?
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Which component of bone cells is primarily responsible for repair after fractures?
Which component of bone cells is primarily responsible for repair after fractures?
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Study Notes
The Skeletal System
- The skeletal system is composed of skeletal bones, cartilage, ligaments, and connective tissue, which stabilizes the skeleton.
- Bones are dynamic organs, made of several tissue types.
Functions of the Skeletal System
- Support: Provides a framework for other organs.
- Protection: Ribs protect the heart and lungs, the skull protects the brain, the vertebrae protect the spinal cord, and the pelvic bones protect the reproductive organs.
- Assistance in Movement: Muscles pull on bones to cause movement.
- Mineral Storage and Release: Bones store calcium ions (98% of the body's calcium), and phosphate ions.
- Blood Cell Production: Bone marrow produces red blood cells, white blood cells, and platelets.
- Triglyceride Storage: Yellow marrow stores (fat) cells.
Anatomy of a Bone
- Diaphysis: The shaft of a long bone.
- Epiphyses: The ends of a long bone.
- Metaphysis: The growth zone between the diaphysis and epiphyses.
- Articular surface cartilage: Covers the surfaces of bones where they meet to form joints.
- Periosteum: The outer lining of bone.
- Medullary cavity: The hollow cavity within the diaphysis.
- Endosteum: The inner lining of bone.
Anatomy of a Bone - Epiphysis
- Contains spongy bone
- Red marrow, which contains blood progenitor cells
Anatomy of a Bone - Diaphysis
- The medullary cavity consists of yellow marrow.
- Yellow marrow consists of fat cells.
Anatomy of a Bone - Metaphysis
- Narrow growth zone between the epiphysis and diaphysis.
Anatomy of a Bone - Histological Organization of Mature Bone
- The matrix of bone: Calcium phosphate converts to hydroxyapatite crystals, make up 2/3 of the bone mass.
- Hydroxyapatite crystals resist compression.
- Collagen fibers: Make up 1/3 of the bone matrix, contribute to tensile strength, and make the bone tissue strong.
- Bone cells (osteocytes): contribute only 2% to the bone mass.
Anatomy of a Bone - Cells of Mature Bone - Osteocytes
- Mature bone cells that maintain the protein and mineral content of the matrix.
- Located in depressions called lacunae.
- Matrix layer associated with osteocytes is called lamellae.
- Small channels extending from osteocytes to bone capillaries (canaliculi).
Anatomy of a Bone - Cells of Mature Bone - Osteoblasts
- Immature bone cells
- On the inner and outer surfaces of bones.
- Produce osteoid (which is a part of the matrix of bone)
- Involved in making new bone in a process called osteogenesis.
Anatomy of a Bone - Cells of Mature Bone - Osteoprogenitor cells
- Bone stem cells
- Found on the inner layer of the periosteum and inner lining of endosteum.
- Differentiate into new osteoblasts
- Heavily involved in bone repair.
Anatomy of a Bone - Cells of Mature Bone - Osteoclasts
- Multinucleated cells
- Secrete acids, dissolving bone, releasing stored calcium and phosphate into the blood.
- This process is called osteolysis.
- Derived from bone marrow.
Anatomy of a Bone - Two Types of Osseous Tissue
- Compact bone: Dense and solid, forms bone walls.
- Spongy bone: (aka trabecular or cancellous bone) open network of plates. Surrounds the medullary cavity. Spongy bone contains bone marrow.
Anatomy of a Bone - Compact Bone (Consists of Osteons)
- Osteons: Basic functional unit of bone.
- Consists of central canals, canaliculi, osteocytes, lacunae, and lamellae (layers).
Anatomy of a Bone - Functional Differences Between Compact and Spongy Bone
- Compact bone: Conducts stress from one end of a long bone to the other. Its tremendous strength is from end to end. Less effective when stress is applied to the side.
- Spongy bone: Arranged in parallel struts, called trabeculae. Forms branching plates; these plates form an open network. Creates the lightweight nature of bones.
Cartilage
- Not as strong as bone, but more flexible.
- Matrix contains collagen and elastic fibers.
- Chondrocytes: cartilage cells, lie within lacunae.
- Has no nerves or blood vessels, relying on nearby tissue for nutrient and waste exchange; this makes it slow to heal.
- Hyaline cartilage: found at the ends of long bones, nose, ribs, larynx, and trachea.
- Fibrocartilage: found in intervertebral disks and the knee.
- Elastic cartilage: found in ear flaps and epiglottis.
Fibrous Connective Tissue
- Made of rows of fibroblasts separated by bundles of collagenous fibers.
- Makes up ligaments and tendons.
- Ligaments connect bone to bone, tendons connect muscle to bone.
Bone Development and Growth
- Osteogenesis: Bone formation.
- Calcification: The deposition of calcium ions into bone tissue.
- Endochondral ossification: Chondrocytes are replaced with bone cells, occurs in long bones.
- Intramembranous ossification: Bone forms directly from mesenchymal cells. Occurs in flat bones like skull bones.
Bone Development and Growth - Epiphyseal Plate
- Cartilage area in the metaphysis.
- During bone growth this cartilage converts to bone near the diaphysis.
- The width of this zone gets narrower as we age and eventually the area is devoid of cartilage, turning into the epiphyseal line.
Bone Development and Growth Factors
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Hormones:
- Parathyroid hormone (PTH): Stimulates osteoclasts, increases calcium levels, maintains calcium homeostasis, and increases calcium absorption. Reduces calcium loss from the kidneys.
- Calcitonin: inhibits osteoclasts, Decreases calcium levels, maintains calcium homeostasis, and increases the rate of calcium loss in the urine and removes calcium from the blood to be used by the bone.
- Growth hormone (somatotropin): Stimulates bone growth, maintains normal activity of the epiphyseal cartilage, dwarfism (too little GH), gigantism, and acromegaly (excess GH).
- Estrogen and Testosterone: Stimulate osteoblast activity. Faster bone growth in young people than epiphyseal cartilage expansion, until bone growth ceases.
- Vitamin D: Formed in the skin by sunlight, converted to a hormone needed for calcium absorption from the digestive system. Rickets are caused with low levels of vitamin D, resulting in bone deformities.
Bone Maintenance, Remodeling, and Repair
- Remodeling of Bone: Inactivity causes degeneration. After several weeks, inactivity causes bones to lose about 1/3 of their mass. Stress/weight stimulates osteoblasts.
- Aging and the Skeletal System: When young, osteoblast activity balances with osteoclast activity. Older people have declining osteoblast activity. Osteoclast activity remains high, causing porous bones. This can lead to osteoporosis.
Articulations (joints)
- Where bones meet.
- Classified as fibrous, cartilaginous, or synovial.
- Fibrous: Immovable (sutures between cranial bones).
- Cartilaginous: Slightly movable (costal cartilages, intervertebral disks).
- Synovial: Freely movable.
Articulations (Synovial joints)
- Ligaments: Support and strengthen joints.
- Joint capsule: Formed by ligaments, surrounds the joint.
- Synovial membrane: Lines the joint capsule, secretes synovial fluid (for lubrication).
- Bursae: Fluid-filled sacs that lessen friction.
- Menisci: C-shaped fibrocartilage, give stability and absorb shock.
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Types of Synovial Joints:
- Ball-and-socket joints: Allow movement in all planes, rotational movements (e.g., hips and shoulders).
- Hinge joints: Movement in a single direction (e.g., elbows and knees).
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Description
Test your knowledge on the skeletal system, including its structure, functions, and anatomy. This quiz covers everything from the roles of bones to the process of blood cell production. Challenge yourself to see how well you understand this essential body system!
