| A | B |
|---|
| Hydrostatic skeleton | Consists of fluid held under pressure in a closed body compartment |
| Axial skeleton | Consists of the skull, the vertebral column, and a rib cage – each of which encloses a valuable organ or organs |
| Appendicular skeleton | Made up of bones of the appendages and the bones that anchor the appendages to the axial skeleton |
| Yellow bone marrow | Found within the central cavity of the bone, it is mostly stored fat brought into the bone by the blood |
| Red bone marrow | Found within the central cavity of the bone, it is a specialized tissue that produces our blood cells |
| Hinge joint | Permit movement in a single plane (i.e., elbow or knee) |
| Pivot joint | Enables rotation, as in our wrist rotating relative to the elbow. |
| Tendons | Connect muscle to bone |
| Ligaments | Connect bone to bone |
| Muscle fiber | A single one of these is actually a single long, cylindrical cell that has many nuclei. Many of these make up a “muscle” |
| Myofibril | Discrete bundles of proteins that include contractile proteins actin and myosin. Many such bundles (~1000) in a single muscle fiber. |
| Actin | Makes up thin filaments |
| Myosin | Makes up thick filaments |
| Motor unit | A motor neuron and all the muscle fibers it controls |
| Slow fibers | Do not fatigue readily, require aerobic respiration for ATP production, lots of myoglobin, many mitochondria |
| Fast fibers | Fatigue rapidly, required anaerobic respiration for ATP production, low myoglobin content, few mitochondria |
