Bone Structure and Histology Quiz

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Questions and Answers

What is the primary function of osteons in compact bone?

To increase the length of the bone

To serve as the structural unit for nutrient and oxygen diffusion (correct)

To act as a reservoir for calcium storage

To provide a cushioning effect for joints

Which component is responsible for the strength of bone tissue?

Periosteum surrounding the bone

Osteocytes within lacunae

Collagen fibers in the matrix (correct)

Concentric canals for blood vessels

Which of the following correctly describes circumferential lamellae?

Thin layers located between osteons

Concentric layers surrounding the entire diaphysis (correct)

Lines that mark the growth plate of the bone

Layers of matrix that are found around blood vessels

Which chemical formula represents the inorganic matrix of bone?

Ca10(PO4)6(OH)2 Signup and view all the answers

What role does the endosteum play in bone tissue?

It lines the central canals of osteons Signup and view all the answers

What is the primary organic component of bone that contributes to its strength and flexibility?

Collagen Signup and view all the answers

Which statement accurately describes the structure of spongy bone?

Spongy bone is composed of trabeculae that disperse stress. Signup and view all the answers

What percentage of the organic components of bone consists of protein and sugar compounds?

10% sugar compounds and 90% protein Signup and view all the answers

Which of the following best describes the function of canaliculi in bone structure?

They allow for nutrient diffusion to maintain cell viability. Signup and view all the answers

How much of the weight of bone is attributed to the inorganic mineral content?

55% Signup and view all the answers

What type of cells are osteoblasts classified as?

Immature bone cells Signup and view all the answers

Which component do osteocytes secrete that helps in the remodeling of bone?

Acid phosphatase Signup and view all the answers

What are the key roles of osteocytes within the bone structure?

Sensing mechanical stress and regulating bone density Signup and view all the answers

Which layer of the periosteum contains fibroblasts and collagen fibers?

Fibrous outer layer Signup and view all the answers

What is the primary function of osteoblasts during the bone repair process?

To secrete the osteoid matrix Signup and view all the answers

What structural feature of compact bone receives rich blood supply?

Haversian system Signup and view all the answers

What is one of the significant functions of the periosteum?

Providing isolation of bone from surrounding tissues Signup and view all the answers

What do osteocytes regulate in response to mechanical stress?

Bone density and remodeling process Signup and view all the answers

Which process involves the action of both osteoblasts and osteoclasts in bone maintenance?

Bone turnover Signup and view all the answers

Which type of cells can differentiate into osteocytes once they become mature?

Osteoblasts Signup and view all the answers

Study Notes

Compact Bone

Structural unit = Osteon
Concentric lamellae = layers of matrix surrounding central canals
Concentric canals = contain blood vessels and nerves
Interstitial lamellae = layers between osteons
Circumferential lamellae = layers around the entire diaphysis
Collagen fibers in matrix provide strength
Endosteum lines each central canal

Bone Histology

Matrix composition:
- Inorganic matrix = 55% hydroxyapatite (Ca10(PO4)6(OH)2)
- Organic matrix (osteoid) = 30% collagen and 10% sugar compounds
- Water = 15%
Spongy bone does not have osteons, it has trabeculae
Osteocytes are mature bone cells that:
- Live in lacunae
- Are mechanosensors
- Secrete osteoid (collagen/sugar protein) for bone building
- Secrete acid phosphatase for bone dissolving
Osteoblasts are immature bone cells that build bone by secreting osteoid
Osteoclasts break down bone by dissolving minerals and organic matrix

Periosteum

Outer layer = dense irregular connective tissue with Sharpey's fibers
Inner layer = contains fibroblasts and osteoprogenitor cells
Functions:
- Isolation of bone from surrounding tissue
- Route for circulation and nervous supply
- Bone growth and repair
- Interwoven with tendons and ligaments

Endosteum

Incomplete cellular layer lining medullary cavity
Contains osteoprogenitor cells, osteoblasts, and osteoclasts
Not as much osteocytes because they are mature and in lacunae
Functions: bone growth, repair, and remodeling

Bone Development

Occurs throughout life
Embryonic Development:
- Endochondral ossification: bone forms within cartilage
- Intramembranous ossification: bone forms within membranes
Childhood:
- Interstitial growth: lengthening of bones
- Appositional growth: widening of bones
Adult: bone remodeling (every 5-7 years)

Factors Involved in Bone Formation

Vitamin K and B12 are required for synthesis of proteins in bone (especially collagen)

Regulation of Bone Remodeling

Calcium ion levels in blood must be maintained between 9-11 mg/100 ml blood
Two organs monitor calcium levels:
- Parathyroid glands:
  - Release parathyroid hormone in response to low calcium
  - Effects:
    - Stimulates osteoclast activity (break down bone)
    - Increases calcium absorption in intestines
    - Decreases calcium excretion in kidneys
- Thyroid glands:
  - Release calcitonin in response to high calcium
  - Effects:
    - Inhibits osteoclast activity
    - Increases calcium excretion in kidneys

Bone Remodeling and Mechanical Stress

Wolff's Law: bones adapt to forces placed on them
Process:
- Stress generates electrical currents in bone
- Osteocytes are mechanosensors and secrete chemicals that alter osteoblast and osteoclast activity (making bone denser and thicker)
Net effect:
- Bones used are stressed become stronger
- Trabeculae shape adjusts to stress
- Unstressed bones become weaker
- Stress attracts osteoblasts, leading to bone thickening

Repair of Fractures

Treatments:
- Reduction (realignment of bone pieces)
- Immobilization (to prevent movement)
- Open (compound) fracture: broken bone breaks through the skin

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Description

Test your knowledge on the structure and histology of bone. This quiz covers compact and spongy bone composition, the roles of various bone cells, and the detailed engineering of the bone matrix. Perfect for biology students studying the skeletal system.