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Skeletal System Overview

1. What are the functions of the skeletal system, and how are they accomplished?

  • Support – Provides framework (e.g., vertebral column, rib cage).

  • Protection – Shields organs (e.g., skull protects brain, ribs protect heart/lungs).

  • Movement – Works with muscles (bones act as levers).

  • Mineral Storage – Stores calcium/phosphate, releases when needed.

  • Blood Cell Production (Hematopoiesis) – Red marrow produces blood cells.

  • Fat Storage – Yellow marrow stores fat as an energy reserve.

  • Hormone Production – Produces osteocalcin (regulates bone formation & metabolism).

2. What are the two divisions of the skeletal system, and what bones make up each?

  • Axial Skeleton (80 bones) – Skull, vertebral column, thoracic cage, hyoid.

  • Appendicular Skeleton (126 bones) – Pectoral girdle, upper limbs, pelvic girdle, lower limbs.

3. What are the two types of bone marrow, their makeup, functions, and locations?

  • Red Marrow – Produces blood cells; found in flat bones & ends of long bones.

  • Yellow Marrow – Stores fat; found in medullary cavity of long bones.

4. What are the cellular components of bone tissue, their functions, and how do they change with age?

  • Osteoblasts – Build bone.

  • Osteocytes – Maintain bone.

  • Osteoclasts – Break down bone for remodeling & calcium release.

  • Bone Matrix: Organic (collagen – flexibility) & Inorganic (calcium phosphate – hardness).

  • Changes Over Life Stages:

    • Pre-adolescence – Osteoblasts dominate.

    • Adulthood – Balance of osteoblasts & osteoclasts.

    • Old Age – Osteoclasts dominate, leading to bone loss.

5. How do compact and spongy bone differ in structure and function? Where are interstitial and circumferential lamellae located?

  • Compact Bone – Dense, strong; contains osteons with central canals for blood supply.

    • Interstitial lamellae (between osteons), circumferential lamellae (outer bone surface).

  • Spongy Bone – Porous, lighter; contains trabeculae, supports marrow & resists stress.

6. What are the layers of the periosteum and endosteum, and what are their functions?

  • Periosteum – Outer fibrous layer (protection) & inner cellular layer (osteoblasts).

  • Endosteum – Lines medullary cavity; contains osteogenic cells for growth/remodeling.

7. What are the two types of bone development, and how do they differ?

  • Endochondral Ossification – Cartilage replaced by bone (long bones).

  • Intramembranous Ossification – Bone forms from connective tissue (skull, clavicle).

8. What is appositional bone growth, and how do we know when it has ended?

  • Process – Increases thickness by adding layers to periosteum.

  • Ends When – Epiphyseal plates close, seen as epiphyseal line in adults.

9. What is bone remodeling, and what is its purpose?

  • Continuous replacement – Balances osteoblast & osteoclast activity.

  • Responds to stress – Strengthens bone based on mechanical load.

10. What are the major blood vessels that service bones, and where are they located?

  • Nutrient arteries – Enter via nutrient foramen; supply bone marrow.

  • Periosteal arteries – Supply outer bone layers.

  • Metaphyseal & Epiphyseal arteries – Supply growth regions.

11. What are the different bone shape classifications and examples of each?

  • Long Bones – Humerus, femur.

  • Short Bones – Carpals, tarsals.

  • Flat Bones – Skull, ribs, sternum.

  • Irregular Bones – Vertebrae, pelvis.

  • Sesamoid Bones – Patella.

12. Where are the paranasal sinuses located, and what are their functions?

  • Frontal – Above eyes; lightens skull.

  • Maxillary – Below eyes; largest, drains nasal cavity.

  • Ethmoid – Between eyes; supports nasal structure.

  • Sphenoid – Behind ethmoid; helps with resonance.

13. Where are the nasal conchae located, and what are their functions?

  • Superior & Middle (Ethmoid bone) – Filters & warms air.

  • Inferior (separate bone) – Enhances airflow efficiency.

14. What bones make up the zygomatic arch, hard palate, nasal septum, and orbital complex?

  • Zygomatic Arch – Zygomatic & temporal bones.

  • Hard Palate – Maxilla & palatine bones.

  • Nasal Septum – Vomer & perpendicular plate of ethmoid.

  • Orbital Complex – Frontal, sphenoid, zygomatic, maxilla, palatine, ethmoid, lacrimal.

15. What are the regions of the vertebral column, and how many vertebrae are in each?

  • Cervical (7)

  • Thoracic (12)

  • Lumbar (5)

  • Sacrum (5, fused)

  • Coccyx (4, fused)

16. What are the spinal curves of the vertebral column?

  • Primary (born with) – Thoracic, Sacral.

  • Secondary (develop later) – Cervical (lifting head), Lumbar (walking).

17. What is the thoracic cage composed of, and how do ribs connect to the sternum?

  • Sternum – Manubrium, body, xiphoid process.

  • Ribs (12 pairs):

    • True (1-7) – Attach directly to sternum.

    • False (8-10) – Attach indirectly.

    • Floating (11-12) – No attachment.

18. What bones make up the pectoral and pelvic girdles?

  • Pectoral Girdle – Clavicle & scapula.

  • Pelvic Girdle – Ilium, ischium, pubis.

19. What bones make up the pelvis, and how is it adapted for pregnancy? How does the male pelvis differ from the female pelvis?

  • Bones – Ilium, ischium, pubis.

  • Female Adaptations – Wider inlet, shallower, larger pubic angle.

  • Male Differences – Narrower, deeper pelvis.

20. What are the greater and lesser pelvis, and what are their boundaries?

  • Greater (False Pelvis) – Above pelvic brim; supports intestines.

  • Lesser (True Pelvis) – Below pelvic brim; encloses pelvic organs.

21. What are the pelvic inlet and outlet, and what are their boundaries?

  • Pelvic Inlet – Superior opening; baby enters birth canal.

  • Pelvic Outlet – Inferior opening; baby exits during birth.