The functions of bone are protection, framework, and making blood cells. Blood cells are broken down at the liver and spleen.

Exocrine glands secrete their materials to external environment through a duct. Examples include sweat, mammary, and salivary glands. Endocrine glands secrete their materials to the internal environment. Examples include adrenal, thyroid, or pituitary glands.

All are true except C. Even in a resting state, muscles are partially contracted. This is called tonus.

Smooth muscle is a type of muscle tissue. Blood, bone, and cartilage are connective tissues.

All are true except D. During muscle fiber contraction, the myosin cross-bridge alternately contacts and detaches from actin.

Epithelial tissue covers the outside of the body and lining of the organs and functions in protection, absorption, and secretion. Cuboidal, columnar, and squamous are major types of epithelial tissue. Connective tissue functions in transport, support, connection, and protection, and cartilage, bone, and blood are the major types. Muscle tissue functions for movement of the body and skeletal, cardiac, and smooth are the major types of muscle tissue. Nerve tissue functions for transmission of information, and the spinal cord and brain are major types of nerve tissue.

Rod cells are sensitive to black and white in less intense light, and cone cells are sensitive to different colors in strong intense light.

The sliding-filament model indicates that the length of I band and H zone are decreased during muscle contraction but A band is not changed.

The iris controls pupil size to regulate the amount of light and the retina is tissue for detecting light waves. The pupil is the hole for light and sclera is the outer layer of the eye. An optic disk called the blind spot is a portion of the retina that has no sensitivity to light. Cornea, the front part of sclera, passes initial light.

This is a picture of cuboidal tissues. Cuboidal epithelial cells have a cube shape and function in secretion at the glands.

Fibrous connective tissue has two types, tendons and ligaments. Tendons connect bones to muscles and ligaments connect bones to bones.

The axial skeleton is composed of skull, ribs, sternum, and vertebra. The pelvic girdle is part of the appendicular skeleton.

During eye response in the dark, rhodopsin is inactivated and Na⁺ channels open, and then glutamine is secreted to bipolar cells by depolarized rod and cone cells.

Branched cells and intercalated disks, which interconnect between cells, are found at cardiac muscle tissues.

Epiphyseal plates are the main regions of bone growth. The Haversian canal covers blood vessels, and osteoclasts break down bone. The marrow cavity and shaft are components of long bones.

Cartilage and blood are connective tissues. Cartilage has chondrocytes, which make collagen and chondroitin sulfate to protect from physical impact, and covers skeletal joints, ears, nose, and trachea. Blood usually functions in clotting, immunity, and carrying oxygen. Cuboidal and squamous are epithelial tissues. Skeletal muscles are one type of muscle tissue.

Skeletal muscles are the only voluntary muscles, and cardiac and smooth muscles have involuntary functions. The skeletal muscle is striated and has multiple nuclei with an array of actin and myosin filaments. The cardiac muscle is striated with intercalated discs. The smooth muscle is not striated and can be found in arteries, the urinary bladder, and the digestive tract.

Muscle fiber is composed of myofibrils, and myofibrils are made up of sarcomere units. Thin filaments are called actin and thick filaments are called myosin.

The middle ear functions in amplifying primary sound and has three components of small bone, which are the malleus, incus, and stapes. Semicircular canals are located in inner ear.