7.1Tissues and organs of the skeletal system

1. What is the branch of medicine and biology that deals with the skeleton and bone tissue?

   • Osteology

2. What organs and tissues constitute the skeletal system?

   • Bones, cartilage, ligaments, and other connective tissues

3. What are the functions of the skeletal system?

   • Support, protection, movement, storage of minerals, and blood cell production

4. Which primary tissue category includes bone, and how does bone differ from other tissues in that category?

   • Connective tissue; bone is hard and mineralized

5. What is the relationship of compact bone, spongy bone, and the marrow cavity in the anatomy of a long bone?

   • Compact bone forms the outer layer, spongy bone is inside, and the marrow cavity is within the spongy bone

6. What are the other anatomical features of a long bone?

   • Diaphysis, epiphyses, articular cartilage, yellow marrow cavity, endosteum, and periosteum

7. What is the structure of a typical flat bone?

   • Two layers of compact bone with spongy bone in between

   7.2 Histology of Osseous Tissue

8. What are the four cell types in bone tissue, and what are their functions, origins, and locations in the tissue?

   • Osteoblasts (build bone), Osteocytes (maintain bone), Osteoclasts (break down bone), Osteogenic cells (stem cells)

9. What are the organic and inorganic components of the bone matrix, and what are their respective contributions to bone strength?

   • Organic: Collagen fibers (flexibility); Inorganic: Hydroxyapatite (hardness)

10. What is the structure of an osteon, and how does osteonic bone relate to interstitial and circumferential lamellae?

    • Osteon: Central canal, concentric lamellae; Interstitial lamellae fill spaces between osteons; Circumferential lamellae encircle the bone

11. How do nerves and blood vessels penetrate throughout a bone?

    • Through the Haversian and Volkmann’s canals

12. How does the histology of spongy bone compare with that of compact bone, and where is spongy bone found?

    • Spongy bone: Trabeculae, lighter, found in epiphyses; Compact bone: Dense, found in diaphysis

13. What are the locations and functions of bone marrow, and how do childhood and adult distributions of the two types of marrow differ?

    • Red marrow (produces blood cells, found in children’s bones); Yellow marrow (stores fat, found in adult bones)

7.3 Bone Development

1. What are the stages of intramembranous ossification, and which bones form this way? How far has this process progressed by birth?

   • Stages: Mesenchymal cells differentiate into osteoblasts, osteoblasts secrete matrix, matrix calcifies, formation of trabeculae, development of periosteum. Bones: Flat bones of the skull, clavicle. Progress by birth: Mostly complete, with some bones still ossifying.

2. What are the stages of endochondral ossification?

   • Stages: Development of cartilage model, growth of cartilage model, development of primary ossification center, development of medullary cavity, development of secondary ossification centers, formation of articular cartilage and epiphyseal plate.

3. What are the histology, cell transformations, and tissue zones of the metaphysis? Which zones and processes account for a child’s or adolescent’s growth in height?

   • Zones: Reserve cartilage, proliferation, hypertrophy, calcification, ossification. Growth in height: Proliferation and hypertrophy zones where chondrocytes divide and enlarge.

4. How do stresses on bones remodel them throughout life? What is the difference between interstitial and appositional growth?

   • Bone remodeling: Osteoclasts resorb bone, osteoblasts form new bone in response to stress. Interstitial growth: Lengthwise growth at epiphyseal plates. Appositional growth: Thickness growth by adding new layers to the surface.

7.4 Physiology of osseous Tissue

1. What is the purpose and process of bone resorption, and which cells carry out this process?

   • Purpose: To break down bone tissue and release minerals into the blood. Process: Osteoclasts secrete acids and enzymes to dissolve bone matrix.

2. What is the purpose and process of bone formation, and which cells carry it out?

   • Purpose: To build new bone tissue. Process: Osteoblasts secrete bone matrix, which then mineralizes.

3. What are the functions of calcium in the body, and what are the consequences of hypocalcemia and hypercalcemia?

   • Functions: Muscle contraction, nerve function, blood clotting. Hypocalcemia: Muscle spasms, seizures. Hypercalcemia: Weakness, kidney stones.

4. How does the skeleton act as a calcium reservoir in regulating blood calcium levels?

   • The skeleton stores calcium and releases it into the blood as needed to maintain stable calcium levels.

5. How is calcitriol synthesized, and how does it support or raise blood calcium levels?

   • Synthesized from vitamin D in the kidneys. It increases calcium absorption in the intestines and reduces calcium loss in urine.

6. What is the source of calcitonin, and how does it correct hypercalcemia?

   • Source: Thyroid gland. It lowers blood calcium levels by inhibiting osteoclast activity and increasing calcium excretion in urine.

7. What is the source of parathyroid hormone, and how does it correct hypocalcemia?

   • Source: Parathyroid glands. It raises blood calcium levels by stimulating osteoclasts, increasing calcium absorption in the intestines, and reducing calcium loss in urine.

8. What are the two forms of phosphate ions in the blood, and what are their bodily functions?

   • Forms: HPO₄²⁻ and H₂PO₄⁻. Functions: Bone formation, energy storage and release, buffering of acids and bases.

9. What are the effects of dietary vitamins A, C, and D on bone metabolism?

   • Vitamin A: Stimulates osteoblast activity. Vitamin C: Necessary for collagen synthesis. Vitamin D: Enhances calcium absorption.

10. What are the effects of cortisol, estrogen, testosterone, growth hormone, insulin, and thyroid hormone on bone metabolism?

    • Cortisol: Inhibits bone formation. Estrogen and testosterone: Promote bone growth. Growth hormone: Stimulates bone growth. Insulin: Promotes bone formation. Thyroid hormone: Regulates bone growth and development.

7.5 Bone Disorders

1. What is the difference between a stress fracture and a pathological fracture? What are the stages in the healing of a fractured bone, and what are the approaches to the clinical treatment of fractures?

   • Stress fracture: Caused by repetitive stress. Pathological fracture: Caused by disease. Healing stages: Hematoma formation, fibrocartilaginous callus formation, bony callus formation, bone remodeling. Treatment: Immobilization, surgery, physical therapy.

2. What are the causes of osteoporosis, its risk factors, pathological effects, diagnosis, treatment, and prevention?

   • Causes: Hormonal changes, calcium deficiency. Risk factors: Age, gender, family history. Effects: Bone fragility, fractures. Diagnosis: Bone density test. Treatment: Medications, lifestyle changes. Prevention: Adequate calcium and vitamin D intake, regular exercise.