| A | B |
|---|
| periosteum | tough layer of connective tissue |
| haversian canal | One of many structural units of vertebrate bone, consisting of concentric layers of mineralized bone matrix surrounding lacunae, which contain osteocytes, and a central canal, which contains blood vessels and nerves |
| bone marrow | soft tissue within bones |
| cartilage | A type of flexible connective tissue with an abundance of collagenous fibers embedded in chondrin |
| ossification | bone during the process of bone formation |
| joint | a place where one bone attaches to another |
| ligament | A type of fibrous connective tissue that joins bones together at joints |
| myosin | A type of protein filament that interacts with actin filaments to cause cell contraction |
| actin | A globular protein that links into chains, two of which twist helically about each other, forming microfilaments in muscle and other contractile elements in cells |
| neuromuscular junction | The junction between an axon terminal of a motor neuron and a muscle fiber innervated by that motor neuron; the axon terminal of a motor neuron is typically branched, forming neuromuscular junctions with a number of different muscle fibers |
| acetylcholine | One of the most common neurotransmitters; functions by binding to receptors and altering the permeability of the postsynaptic membrane to specific ions, either depolarizing or hyperpolarizing the membrane |
| tendon | A type of fibrous connective tissue that attaches muscle to bone |
| epidermis | The outer covering of animals |
| keratin | One of a group of tough, fibrous proteins formed by certain epidermal tissues and especially abundant in skin, claws, hair, feathers, and hooves |
| melanin | a dark brown pigment |
| dermis | The inner layer of the skin, beneath the epidermis |
| hair follicle | part of the skin that grows hair by cramping old cells tightly |
