Anatomy/Skeletal System

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This page is incomplete. It does not cover all important aspects of this subject. Please keep this in mind when reading the page and add relevant information if possible.

The skeletal system is a topic of the event Anatomy for the 2020 competition, along with the integumentary system and the muscular system.

For the skeletal system you will need to know:

  1. The names of the bones and their surface anatomy as shown on a diagram or X-ray
  2. Name, structure, and function of types of joints and ranges allowed by each joint
  3. Structures of bones in cross-section
  4. How to distinguish between types of vertebrae
  5. Diseases such as osteoarthritis, osteoporosis, disc herniation, and scoliosis
  6. Effects of exercise on the skeletal system
  7. How the skeletal system works together with the muscular system.
Competition Level Health Concepts
Regional/State Bones of the axial and appendicular skeleton, including the ability to label bones on a diagram and/or X-ray

Name, structure, and function of types of joints (ball and socket joints, fibrous joints, cartilagenous joints, synovial joints, etc.), including the range of motion allowed by each type

Name, structure, and function of the muscles and ligament attachments that surround joints

Structure, cellular composition, and function of bones, bone marrow, and cartilage, including the ability to identify components in cross-section

Distinguish types of spinal vertebrae (e.g., cervical, thoracic, and lumbar)

Understanding of the following diseases at the levels from the cell to the whole body, including the radiological features of each disease: osteoarthritis, osteoporosis, fractures, disc herniation, scoliosis, anterior cruciate ligament tears, medial collateral ligament damage

The effect of exercise on the skeletal system and the aforementioned diseases

National Understanding of the following additional diseases: spinal stenosis, achondroplasia, juvenile rheumatoid arthritis, spinal fractures, ankylosing spondylitis, and osteosarcoma

Treatment and/or prevention of all the aforementioned diseases and disorders, including drugs, surgery, and other alternative treatments

Bones of the skull, including the ability to label them on a diagram

Salter-Harris fracture identification system

Bone Structure

Made up of osteogenic cells, organic matrix, and minerals. A cross-section structure is where spongey bone and compact bone cross.

Bone Cells

There are 5 main types of bone cells: osteoblasts, osteocytes, osteogenic cells, osteoclasts, and bone-lining cells.

  • Osteoblasts: Bone forming cells. They synthesize and secrete unmineralized ground substance. Found in areas of high metabolism within the bone.
  • Osteocytes: Mature bone cells (made from osteoblasts) that made bone tissue around themselves. They maintain healthy bone tissue by secreting enzymes and controlling the bone mineral content. They control calcium released from bone tissue into the bloodstream.
  • Osteogenic Cells: Respond to trauma by giving rise to bone forming cells (osteoblasts) and bone destroying cells (osteoclasts).
  • Osteoclasts: Large cell that breaks down bone tissue. Important to growth, healing, and remodeling.
  • Bone-Lining Cells: Made from osteoblasts along the surface of most adult bones. Thought to regulate the movement of calcium and phosphate into and out of the bones.

Bone Types

Long bone:

  • Type that makes up most of the arms and legs (often associated with your limbs). They are classified as bones that have a greater length than width.
  • Compact bone. Has an outer layer, and is comprised of spongy bone at the ends. The ends of long bones have articular cartilage on them.

Flat bone:

  • Found in areas such as the ribs and cranium. (They are expanded into broad, flat plates.) These bones serve to protect internal organs.

Short bone:

  • Found in areas such as the carpals of your wrist and tarsals of your ankles. They are classified as bones that have a greater width than length.

Sesamoid Bones:

  • A sub-section of Short bone found within tendons. Named for their "Sesame Seed" shape. (Ex. Patella, Pisiform)

Irregular Bones:

  • Bones found that don't fit into other categories. (Ex. Hip bones, vertebrae)

Types of Joints

  • Ball and Socket: one side of the joint is a rounded, ball-shaped bone, which fits into a cup-like socket of a different bone; allows for a huge range of movement and is found in the hip and the shoulder
  • Condyloid: an ovoid head of one bone moves in an elliptical cavity of another, allowing all movements except axial rotation; this type is found at the wrist to connect the radius and carpal bones, and at the base of the index finger
  • Saddle: similar movements to a condyloid joint, a joint where two saddle-shaped ends of a bone meet, found in the thumbs
  • Hinge: only allows flexing and extending movement; found in the elbow, knee, and in the phalanges of both the fingers and toes
  • Pivot: one bone rotates around another, allows rotating movement similar to that of a lid on a jar
  • Plane Gliding: side to side only

Bones of the Skull

Occipital, temporal, zygomatic. Only necessary for nationals.

Spinal Vertebrae

There are five main segments of the vertebral column: the cervical vertebrae, the thoracic vertebrae, the lumbar vertebrae, the sacral vertebrae and the coccyx.

Cervical Vertebrae

There are 7 cervical vertebrae beginning immediately below the skull and extending to the base of the neck. The bottom cervical vertebrae, C7, sticks out near the top of the shoulder blades (scapulas). The top, or atlas vertebrae supports the head, and the second, or axial vertebrae allows the neck to pivot.

Thoracic Vertebrae

There are 12 thoracic vertebrae found in the human torso. The thoracic vertebrae are attached to the ribs which enclose the thorax. The ribcage consists of true (1-7) and false (8-10) ribs, which attach to the sternum at the front of the thorax, while the floating ribs (11-12) at the bottom of the ribcage do not attach to anything. Larger than cervical vertebrae.

Lumbar Vertebrae

The 5 lumbar vertebrae comprise the lower back area. They provide flexibility and stability to the trunk region. Largest vertebrae and thick in structure.

Sacral Vertebrae

The sacrum, or sacral vertebrae, forms during adulthood and is considered part of the pelvic region. It attaches the coccyx to the rest of the vertebral column.


The coccyx, or tailbone, is a vestigial structure that comprises of 3 to 5 bony segments.

Bone Marrow

A soft tissue inside the bone that produces cells.

Hematopoisesis: Blood cell formation. Mainly takes place in red marrow of bones. Red Marrow: Functions in formation of red blood cells, white blood cells, and platelets. Bone marrow in infants-- Red marrow is found in bone cavities, and is replaced by yellow marrow for fat storage with aging. Bone marrow in adults-- Red marrow is only present in spongey bone (skull, ribs, sternum, clavicles, vertebrae, pelvis).


Comprised mostly of water. Has no blood vessels or nerves. Strong and resilient. Heals poorly. Chondroblasts: cartilage forming cells

Types of Skeletal Cartilage

  • Hyaline Cartilage: Fine collagen fiber matrix. Most abundant type of cartilage. Found in articular, costal, respiratory, and nasal cartilage.
  • Elastic Cartilage: Similar to hyaline cartilage, but has more elastic fibers. Found in external ear and epiglottis.
  • Fibrocartilage: Rows of chondrocytes with thick collagen fibers. Highly compressible with great tensile strength. Found in the menisci of the knee, vertebrate discs, and pubic symphysis.


ACL: Anterior cruciate ligament (connects femur to tibia) MCL: Medial collateral ligament (connects femur to tibia)


6 types of fractures: greenstick, spiral, comminuted, transverse, compound, vertebral compression.

  • Greenstick Fracture: Bone breaks incompletely
  • Spiral Fracture: Bone has been twisted apart
  • Comminuted Fracture: Bone breaks into many fragments
  • Transverse Fracture: Occurs straight across the bone
  • Compound Fracture: Bone breaks completely through and out of the skin
  • Vertebral Compression Fracture: Bone is crushed under weight of other bones in the spine

Bone Repair Sequence

Injury--> Invasion of blood vessels and generalized cells (2-3 days)--> Fibroblasts develop (1 week)--> chondroblasts develop--> Callus forms (4 weeks)--> Remodeling with osteoclasts (8 weeks)

Skeletal System Diseases

Diseases of the Skeletal System
Disease Name Cause Symptoms Treatment Prevention Effect on the Body
Osteoarthritis Faster break down of cartilage, extra strain on joints, joint injuries Pain in joints, stiffness, limited joint movement, tenderness/swelling Maintain healthy weight, exercise, Medications- acetaminophen, NSAIDs (Non-Steroidal Anti-Inflammatory Drugs) Exercise, keep healthy weight, avoid joint injuries Break down of cartilage of joints, joints become hurtful
Osteoporosis Age, Gender, more bone being absorbed than new bone being made Back pains, stooped posture, easily broken bones, loss of height Calcium and Vitamin D, exercise, healthy diet, Medications- calcitonin, bisphosphonates Nutritious diet, exercise, don’t smoke, don’t drink a lot of alcohol Thinning of the bone
Disc Herniation Wear and tear of disc, injuries, strain on disc, age Pain, numbness, weakness, leg pain, muscle pain Limit activities, use ice or heat, aspirin, NSAIDs (Non-Steroidal Anti-Inflammatory Drugs) Healthy body weight, exercise, quit smoking, practice good posture Bulging/ breaking of discs
Scoliosis Disorders at birth, injuries, infections Curvature of the spine, one shoulder stick out more than the other Brace, pain relieving meds (aspirin, ibuprofen) Cannot be prevented Curvature of the spine
Spinal Stenosis Osteoarthritis, formation of bone spurs in spine Pain, loss of balance, loss of bladder control Physical therapy, NSAIDs (Non-Steroidal Anti-Inflammatory Drugs), rest, limited activity, back brace Exercise, use good body mechanics, healthy weight, good posture Narrowing in areas of spine- puts pressure on nerves
Rheumatoid Arthritis Genes- allow for autoimmune disorder of joints- body destroys own joints Pain and swelling in joints, fatigue, loss of appetite, weight loss Physical therapy, Medications- NSAIDs (Non-Steroidal Anti-Inflammatory Drugs), DMARDs (Disease Modifying Anti-Rheumatic Drugs) Cannot be prevented Inflammation of tissues lining joints- causes destruction of joints
Gout Too much uric acid in the blood, obesity, a lot of alcohol, other conditions, taking certain medications Pain/swelling in the joint, skin around joint red and itchy, intolerable pain, fever Rest, healthy weight, limit alcohol, Medications- NSAIDs (Non-Steroidal Anti-Inflammatory Drugs) Control risk factors A kind of arthritis, formation of hard crystals in joints
Juvenile Rheumatoid Arthritis Genetic factors, overly active immune system, infection that activates immune system Joint pain, swelling, irritability Exercise, assistive devices, Medications- NSAIDs (Non-Steroidal Anti-Inflammatory Drugs), DMARDs (Disease Modifying Anti-Rheumatic Drugs) Cannot be prevented Rheumatoid arthritis in children

Effects of Exercise on the Skeletal System

Weight-bearing physical activity causes new bone tissue to form, and this makes bones stronger. Bones and muscles both become stronger when muscles push and tug against bones during physical activity.

Sample Questions

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