Chapter 6&7(mostly 6): The Skeleton System

Q1: What are the functions of the human skeletal system?

1. Protection: The skeleton protects vital organs such as the brain (skull)

2. Mineral Storage: The bone stores minerals such as calcium(Ca ²⁺) and phosphate (PO₄^3-), stored in our bones.

3. Blood Cell Formation: Red bone marrow is the site of blood cell formation

   1. What blood cells? - All of them 

4. Fat Storage: Yellow bone marrow stores lipids 

5. Movement: Muscles produce body movement via their attachment to bones

6. Support: The skeleton supports the weight of the body 

Q2: What are the general shapes of human bones, and what are examples of each?

1. Long Bones: Bone is longer than it is wide (shaped rectangle)- an example is the femur 

2. Short Bones: Bone is about as long as it is wide ( shaped cube/cuboid)- an example is wrist and ankle bones

3. Flat Bones: Bone is broad, flat, and thin (flat)- an example is skull, ribs, and sternum 

4. Sesamoid Bones: Small, round, flat bone found within the tendon (seed shape)- an example is the patella

5. Irregular Bones: Bones shape doesn’t fit into other classes (goofy shaped)-an example is vertebrae

Q3: Define bone markings/surface features from Table 7.1.

• Foramen: A rounded passageway through bone (Hole in bone)

• Fossa: Flatted, shallow depression 

• Tuberosity: Large, round projection 

Q4: Describe the gross and microscopic anatomy of a long bone.

• Gross Anatomy:

  • Diaphysis: End of the bone (has no fibers layer, only the cellular layer)

  • Epiphyses: The shaft (middle) of the bone 

  • Metaphysis: This is between diaphysis and epiphyses, and contains a growth plate.

  • Periosteum: Has 2 layers; Around the bone 

    • A somewhat shiny, whitish dense irregular connective tissue 

      • The outer fibrous layer (periosteum)

        • Collagen fiber (Fibrous)

        • Blood Vessels

        • Nerves

      • The inner cellular layer (Endosteum)

        • Osteogenic cells (Osteo-bone; gen- to make)

        • Stem cells of bone or cartilage

          • Osteogenic cells can be osteoblast/chondroblast 

• Microscopic Anatomy:

  • Osteons: Structural units in compact bone.

  • Haversian Canal: Central canal for blood vessels.

  • Trabeculae: Network in spongy bone.

Q5: What is the composition of human bony matrix?

• Inorganic Components: Has 65% 

  • Hydroxyapatite - Ca₁₀ (PO₄)₆(HO)₂   Mostly Bone 

• Organic Components: Has 35% 

  • Cells 

  • Collagen (⅓ weight)

  • Blood 

  • Nerves

  • Proteoglycans 

Q6: Compare the microscopic structure of compact and spongy bone.

• Compact Bone: Dense, contains osteons with Haversian canals.

• Spongy Bone: Porous, contains trabeculae filled with red or yellow marrow.

Q7: What are red bone marrow and yellow bone marrow, and how do they differ?

• Red bone marrow is responsible for producing blood cells, which is also known as hematopoiesis.

• Yellow Bone Marrow: This is a type of bone marrow that primarily stores triglycerides (fats).

Q8: What are the types of bone cells, and what are their functions?

1. Osteoblasts: Bone-building cells that secrete the bone matrix.

2. Osteocytes: Mature bone cells that maintain bone tissue.

3. Osteoclasts: Break down bone tissue for resorption and remodeling.

4. Osteoprogenitor Cells: Undergo division to form osteoblasts.

Q9: What are intramembranous and endochondral ossification?

• Intramembranous Ossification: (Intra- inside, within a membrane) 

  • Forming bone as a sheet 

    • Osteoblasts developing from mesenchymal cells 

    • Osteoblasts make a bony matrix that calcifies, and then they become osteocytes. 

    • We make spongy bone on the inside, and compact on the outside 

• Endochondral Ossification: (more common, has most bone)

  • Cartilage- bone inside 

    • First embryonic development of hyaline cartilage model- surrounding hyaline cartilage is perichondrium (osteogenic cells around) then become osteoblasts. 

    • The first blood vessel that arrives is the primary ossification center in a long bone then the secondary officiation center (Hyaline cartilage cells get surrounded)

Q10: How do bones grow as shown in Fig. 6.14?

• Bone Growth in Length: Long bones grow in length at the epiphyseal plate, which has five zones of cells:

1. Zone of Proliferation: Chondrocytes divide.

2. Zone of Hypertrophy and Maturation: Chondrocytes enlarge and mature.

3. Zone of Calcification: Chondrocytes die, and their matrix calcifies.

4. Zone of Ossification: Calcified cartilage is replaced with bone.

Q11: What are common stresses placed on human bones? “Engineering stuff”

• Force:  IS the mass times(x) acceleration 

• Load: Is an applied force 

• Pressure: Is a force over an area 

  • Bone margin: kg/cm²

• Stress: Is the force created within an object that pushes back against the load 

• Strain: The deformation of an object due to stress

• Strength: Is the ability to resist breakage and permanent deformation

• Toughness: Is the ability to resist the spreading of cracks (the ability to continue to self-repair)

• Elasticity: Is the ability to return to an original shape after the load is removed 

  • Compression: molecules moving directly at one another  

  • Tension: (A “pulling” force) molecules move directly away from one another 

  • Shear: Molecules moving past each other in opposite directions 

Q12: How do stress and nutrition affect bones?

• Stress and Bone Remodeling

• Compression & Tension: Weight-bearing activities stimulate osteoblasts, increasing bone mass.

• Pressure: Continuous pressure activates osteoclasts, leading to bone resorption (e.g., braces realigning teeth).

Nutrition and Bone Health

• Calcium & Vitamin D: Essential for bone formation and calcium absorption.

• Vitamin K & Vitamin C: Support bone mineralization and collagen synthesis.

• Protein: Needed for collagen but excessive intake may lead to bone loss.

Q13: Compare and contrast bone remodeling and bone repair.

• Bone Remodeling: Can be broken down and make up the bone we already have

• Bone Repair: This can involve several steps to restore the bone's structure and strength after a fracture.

Q14: What are the steps in fracture repair?

1. Bone is injured, we make hematoma (bone bleeds)

2. At the site of the fracture, we form soft callus (Hyaline cartilage callus)

3. Formation of bone callus

4. Bone is remodeled (after loads of bones)

Q15: How do calcitonin and PTH regulate calcium levels?

• Calcitonin: When blood calcium is High 

• PTH (Parathyroid hormone): When blood calcium is low  

Q16: What are the types of fractures?

• Simple: Bone does not break the skin

• Compound: Bone pierces the skin 

• Comminuted:  Bone shatters into fragments 

Q17: Which bones belong to the axial and appendicular skeletons?

• Axial: Skull, vertebral column, rib cage.

• Appendicular: Limbs, pelvic, and pastoral girdles.

Q18: What are the normal and abnormal curvatures of the vertebral column?

• Normal Curvatures: Cervical, thoracic, lumbar, sacral 

• Abnormal Curvatures:

  • Scoliosis: Lateral curvature

  • Kyphosis: Exaggerated thoracic curvature 

  • Lordosis: Exaggerated lumbar curvature 

Q19: How does the male pelvis differ from the female pelvis?

• Male Pelvis: Narrower, heavier, heart-shaped inlet 

• Female Pelvis: A wider, lighter, oval-shaped inlet for childbirth.

Definitions

• Marfan's Syndrome: Genetic disorder affecting connective tissue, leading to long limbs and cardiovascular issues.

• Scurvy: Vitamin C deficiency causing weak connective tissue.

• Cleft Lip/Palate: Congenital deformity where the lip or palate fails to fuse.

• Osteomalacia/Rickets: Softening of bones due to Vitamin D deficiency.

• Osteomyelitis: Bone infection.

• Herniated Disc: Rupture of intervertebral disc, pressing on nerves.

• Laminectomy: Surgical removal of part of a vertebra to relieve pressure.

• Spina Bifida: Congenital defect where the vertebral arch fails to close.

Osteoporosis

Osteoporosis is characterized by decreased bone mass and deterioration of bone tissue, leading to fragile bones and an increased risk of fractures. It occurs when bone resorption by osteoclasts outpaces bone formation by osteoblasts, resulting in reduced bone density.

Role of Estrogen in Osteoporosis

Estrogen plays a crucial role in maintaining bone density by:

• Inhibiting Osteoclast Activity: Estrogen suppresses osteoclasts, reducing bone resorption.

• Promoting Osteoblast Function: It enhances osteoblast activity, supporting bone formation.

• Regulating Calcium Absorption: Estrogen helps maintain calcium balance, which is essential for bone strength.