Striated muscle contains sarcomeres, visible bands in microscopic images. There are two types: cardiac muscle (heart) and skeletal muscle (skeleton). Skeletal muscle is wrapped in epimysium, organized into fascicles by perimysium. Cardiac muscle cells are unicellular, connected by intercalated disks
Three main types: skeletal, smooth, and cardiac muscle cells. Muscle cells develop from embryonic precursor cells called myoblasts. Skeletal muscle forms by fusion of myoblasts, creating multinucleated fibers. Cardiac muscle cells have single central nucleus and intercalated discs. Smooth muscle cells control involuntary movements without striations
Synovial joints unite bones with fibrous capsule surrounding synovial cavity. Joint capsule consists of outer fibrous and inner synovial membrane layers. Joint cavity filled with synovial fluid for lubrication and shock absorption. Articular cartilage covers bone ends for smooth movement
Myofibrils are rod-like organelles in muscle cells, measuring 1-2 micrometres in diameter. They are created during embryonic development through myogenesis. Myofibrils are composed of proteins including actin, myosin, and titin
Spiders are air-breathing arthropods with eight limbs and venomous chelicerae. There are 52,309 spider species in 134 families worldwide. They have two tagmata: cephalothorax and abdomen connected by pedicel. Spiders lack antennae and have most centralized nervous systems among arachnids
Snakes lack limbs and use muscles and scales for movement. Forked tongue collects particles and detects chemical signals. Heat-sensing organs help detect warm-blooded prey. Spectacles cover eyes and nostrils help breathe. Dorsal, ventral and subcaudal scales provide protection