Skeletal System Study Guide (Human Bio)

What are the functions of the skeletal system?

Support the body when standing, provide movement, protect the organs, produce blood cells, and store minerals/fat.

Describe the structure of long bone, including the tissues it contains.

Diaphysis (Shaft): Contains a central medullary cavity with yellow marrow.

Epiphysis: Ends of the bone; contains spongy bone filled with red marrow.

Metaphysis: Region between diaphysis and epiphysis; contains the growth plate (epiphyseal plate).

Periosteum: Outer fibrous covering with blood vessels and nerves; involved in growth and repair.

Endosteum: Lines the medullary cavity; contains bone-forming cells.

Compact bone: Dense outer layer; provides strength.

Spongy bone: Porous inner bone; reduces weight and holds marrow.

List three types of cartilage found in the body.

Hyaline cartilage: Provides smooth surfaces for joint movement; found in nose, trachea, and at ends of long bones.

Elastic cartilage: Maintains shape and flexibility; found in the ear and epiglottis.

Fibrocartilage: Resists compression and absorbs shock; found in intervertebral discs and pubic symphysis.

Identify the bones of the skull, hyoid, vertebral column and rib cage.

Skull

• Cranial: Frontal, parietal, temporal, occipital, sphenoid, ethmoid.

• Facial: Nasal, zygomatic, maxilla, mandible, lacrimal, vomer, palatine, inferior nasal concha.

Hyoid bone: A U-shaped bone in the neck that supports the tongue; not attached to other bones.

Vertebral column: 33 vertebrae total — cervical (7), thoracic (12), lumbar (5), sacrum (5 fused), coccyx (4 fused).

Rib cage

• 12 pairs of ribs.

  • True ribs (1–7): attach directly to sternum.

  • False ribs (8–10): attach via cartilage.

  • Floating ribs (11–12): no anterior attachment.

Sternum: Manubrium, body, xiphoid process.

Identify regions of the vertebral column.

Cervical (7): Neck region.

Thoracic (12): Upper/mid back; articulates with ribs.

Lumbar (5): Lower back; large, weight-bearing.

Sacrum (5 fused): Connects spine to pelvis.

Coccyx (4 fused): Tailbone.

Explain the function of sinuses and intervertebral discs.

Sinuses: Air-filled cavities in skull bones; lighten skull weight, moisten and warm air, enhance voice resonance.

Intervertebral discs: Pads of fibrocartilage between vertebrae; absorb shock and allow spinal flexibility.

Identify the bones of the pelvic and pectoral girdles.

• Pectoral girdle (shoulder girdle):

  • Clavicle (collarbone)

  • Scapula (shoulder blade)

• Pelvic girdle:

  • Hip bones (coxal bones): each made of ilium, ischium, and pubis

  • Sacrum and coccyx form the bony pelvis.

Identify the bones of the upper and lower limbs.

• Upper limb:

  • Arm: Humerus

  • Forearm: Radius (lateral), ulna (medial)

  • Hand: Carpals (wrist), metacarpals (palm), phalanges (fingers)

• Lower limb:

  • Thigh: Femur

  • Leg: Tibia (medial), fibula (lateral)

  • Kneecap: Patella

  • Foot: Tarsals (ankle), metatarsals, phalanges.

Compare and contrast the three types of joints in terms of structure and motion.

• Fibrous joints:

  • Structure: Bones joined by dense connective tissue

  • Motion: Immovable (e.g., sutures in skull)

• Cartilaginous joints:

  • Structure: Bones connected by cartilage

  • Motion: Slightly movable (e.g., intervertebral discs)

• Synovial joints:

  • Structure: Bones separated by a joint cavity filled with synovial fluid

  • Motion: Freely movable (e.g., shoulder, knee)

Describe the structure and operation of a synovial joint. 

Components:

• Articular cartilage: Covers bone ends; reduces friction

• Joint (synovial) cavity: Space with synovial fluid

• Synovial membrane: Produces fluid for lubrication

• Fibrous capsule: Encloses joint; provides stability

• Ligaments: Reinforce joint and connect bones

• Bursae: Fluid-filled sacs reducing friction

Operation:

• Allows a wide range of movements: flexion, extension, rotation, abduction, etc.

Explain the steps in ossification and of repair of bone.

• Ossification (bone formation):

  • Intramembranous ossification: Forms flat bones (e.g., skull); mesenchymal cells → bone.

  • Endochondral ossification: Forms most bones; cartilage → bone.

    1. Cartilage model develops

    2. Bone collar forms around shaft

    3. Primary ossification center develops in diaphysis

    4. Secondary ossification centers form in epiphyses

    5. Growth continues at epiphyseal plates until adulthood

• Bone repair (after fracture):

  1. Hematoma formation: Blood clot forms at break

  2. Fibrocartilaginous callus: Soft callus forms

  3. Bony callus: Hard callus of spongy bone replaces soft callus

  4. Bone remodeling: Bone reshaped into original structure.