Anatomy/Skeletal System

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.

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: Flat bone: Short bone: Sesamoid Bones: Irregular Bones:
 * 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.
 * Found in areas such as the ribs and cranium. (They are expanded into broad, flat plates.) These bones serve to protect internal organs.
 * 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.
 * A sub-section of Short bone found within tendons. Named for their "Sesame Seed" shape. (Ex. Patella, Pisiform)
 * 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

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.

Coccyx
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).

Cartilage
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.

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

Fractures
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)

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.

Resources

 * Skeletal System
 * Skeletal tutorials
 * Great tutorial on the human skeleton
 * List of Bones in the Skeletal System
 * PowerPoint created by Sci Oly people on Skeletal, Muscular, Integumentary Systems