Bone: A bone is a rigid organ that constitutes part of the vertebrate skeleton. Bones support and protect the various organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, and enable mobility.Cartilage: firm, whitish, flexible connective tissue found in various forms in the larynx and respiratory tract, in structures such as the external ear, and in the articulating surfaces of joints.Blood: the red liquid that circulates in the arteries and veins of humans and other vertebrate animals, carrying oxygen to and carbon dioxide from the tissues of the body.11. Cartilage: chondrocytes. Bones: osteocytes in lacunae12.Cartilage types:Hyaline: most common, found in the ribs, nose, larynx, trachea. Is a precursor of bone.This type of cartilage has a glassy appearance. It looks slightly basophilic overall in H&E sections. Hyaline cartilage has widely dispersed fine collagen fibres (type II), which strengthen it. The collagen fibres are hard to see in sections. It has a perichondrium, and it is the weakest of the three types of cartilage.Fibrocartilage: is found in intervertebral discs, joint capsules, ligaments. This is the strongest kind of cartilage, because it has alternating layers of hyaline cartilage matrix and thick layers of dense collagen fibres oriented in the direction of functional stresses.This type of cartilage does not have a perichondrium as it is usually a transitional layer between hyaline cartilage and tendon or ligament.Elastic: is found in the external ear, epiglottis and larynx. In elastic cartilage, the chondrocytes are found in a threadlike network of elastic fibers within the matrix.Elastic cartilage provides strength, and elasticity, and maintains the shape of certain structure such as the external ear. It has a perichondrium.13.Erythrocytes: a red blood cell that (in humans) is typically a biconcave disc without a nucleus. Erythrocytes contain the pigment hemoglobin, which imparts the red color to blood, and transport oxygen and carbon dioxide to and from the tissues.Leukocytes: a colorless cell that circulates in the blood and body fluids and is involved in counteracting foreign substances and disease; a white (blood) cell. There are several types, all amoeboid cells with a nucleus, including lymphocytes, granulocytes, monocytes, and macrophages.Platelets: a small colorless disk-shaped cell fragment without a nucleus, found in large numbers in blood and involved in clotting.Fibroblast: a cell in connective tissue that produces collagen and other fibers.Mast cells:a cell filled with basophil granules, found in numbers in connective tissue and releasing histamine and other substances during inflammatory and allergic reactions.14.Organ:a part of an organism that is typically self-contained and has a specific vital function, such as the heart or liver in humans.15.The relative coloration of the skin depends of the amount of melanin produced by melanocytes in the stratum basale and taken up bykeratinocytes.16.Skeletal Muscle: attach to and move bones by contracting and relaxing in response to voluntary messages from the nervous system. Skeletal muscle tissue is composed of long cells called muscle fibers that have a striated appearance. Muscle fibers are organized into bundles supplied by blood vessels and innervated by motor neurons.Cardiac Muscle: the heart wall is composed of three layers. The middle layer, the myocardium, is responsible for the heart’s pumping action. Cardiac muscle, found only in the myocardium, contracts in response to signals from the cardiac conduction system to make the heart beat. Cardiac muscle is made from cells called cardiocytes. Like skeletal muscle cells cardiocytes have a striated appearance, but their overall structure is shorter and thicker. Cardiocytes are branched, allowing them to connect with several other cardiocytes, forming a network that facilitates coordinated contraction.Smooth Muscle: is found in the walls of hollow organs throughout the body. Smooth muscle contractions are involuntary movements triggered by impulses that travel through the autonomic nervous system to the smooth muscle tissue. The arrangement of cells within smooth muscle tissue allows for contraction and relaxation with great elasticity. The smooth muscle in the walls of organs like the urinary bladder and the uterus allow those organs to expand and relax as needed. The smooth muscle of the alimentary canal (the digestive tract) facilitates the peristaltic waves that move swallowed food and nutrients. In the eye smooth muscle changes the shape of the lens to bring objects into focus. Artery walls include smooth muscle that relaxes and contracts to move blood through the body.17.The nail bed extends from the lunula to the hyponychium. A set of ridges on the underside of the nail plate extend to the lunula, with the small vessels transporting blood and other fluids being orientated on the same axis.The epidermis of the nail bed is mainly thick, and becomes thicker at the nail folds. The dermis is sparse and contains very little fat. Sweat ducts can also be found at the end of the nail bed.18.Sweat glands, also known as sudoriferous or sudoriparous glands, from Latin sudor, meaning ‘sweat’are small tubular structures of the skin that produce sweat. Sweat glands are a type of exocrine gland, which are glands that produce and secrete substances onto an epithelial surface by way of a duct.19.Thermoregulation: during strenuous physical activities, such as skiing or running, the dermal blood vessels dilate and sweat secretion increases. These mechanisms prevent the body from overheating. In contrast, the dermal blood vessels constrict to minimize heat loss in response to low temperatures.

20. Dermis, epidermis and hypodermis. Depending the size of the heat applicated in the skin we classified burnings into three increasing levels:First-degree: superficial, partial-thickness.Second-degree: deep, partial-thickness.Third-degree: full-thickness.21. Cellular secretion (or exocytosis): is a long-lasting process by which a cell directs secretory vesicles out of the cell membrane.22. The integumentary system: consists of the skin, hair, nails, glands, and nerves. Its main function is to act as a barrier to protect the body from the outside world. It also functions to retain body fluids, protect against disease, eliminate waste products, and regulate body temperature.