Connective tissue in the context of Periostitis

In a multicellular organism, an organ is a collection of tissues joined in a structural unit to serve a common function. In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to act together in a function. Tissues of different types combine to form an organ which has a specific function. The intestinal wall for example is formed by epithelial tissue and smooth muscle tissue. Two or more organs working together in the execution of a specific body function form an organ system, also called a biological system or body system.

An organ's tissues are broadly classified into parenchyma, the functional tissue, and stroma, the structural tissue with supportive, connective, or ancillary functions. For example, the gland tissue that produces hormones is the parenchyma, while the stroma includes the nerves that innervate the parenchyma, the blood vessels that oxygenate and nourish it and remove metabolic wastes, and the connective tissues that provide structure, placement, and anchoring. The primary tissues that form an organ generally have common embryologic origins, often arising from the same germ layer. Organs are present in most multicellular organisms. In single-celled organisms such as eukaryotes, the functional analogue of an organ is an organelle. In plants, there are three main organs.The number of organs in any organism depends on the definition used. There are approximately 79 organs in the human body; the exact number remains debated.

A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the organs of the body, produce red and white blood cells, store minerals, help regulate acid-base homeostasis, provide structure and support for the body, and enable mobility and hearing. Bones come in a variety of shapes and sizes and have complex internal and external structures.

Bone tissue (also known as osseous tissue or bone in the uncountable) is a form of hard tissue, specialised connective tissue that is mineralized and has an intercellular honeycomb-like matrix, which helps to give the bone rigidity. Bone tissue is made up of different types of bone cells: osteoblasts and osteocytes (bone formation and mineralisation); osteoclasts (bone resorption); modified or flattened osteoblasts (lining cells that form a protective layer on the bone surface). The mineralised matrix of bone tissue has an organic component of mainly ossein, a form of collagen, and an inorganic component of bone mineral, made up of various salts. Bone tissue comprises cortical bone and cancellous bone, although bones may also contain other kinds of tissue including bone marrow, endosteum, periosteum, nerves, blood vessels, and cartilage.

In biology, tissue is an assembly of similar cells and their extracellular matrix from the same embryonic origin that together carry out a specific function. Tissues occupy a biological organizational level between cells and a complete organ. Accordingly, organs are formed by the functional grouping together of multiple tissues.

The English word "tissue" derives from the French word "tissu", the past participle of the verb tisser, "to weave".

The tongue is a muscular organ in the mouth of a typical tetrapod. It manipulates food for chewing and swallowing as part of the digestive process, and is the primary organ of taste. The tongue's upper surface (dorsum) is covered by taste buds housed in numerous lingual papillae. It is sensitive and kept moist by saliva and is richly supplied with nerves and blood vessels. The tongue also serves as a natural means of cleaning the teeth. A major function of the tongue is to enable speech in humans and vocalization in other animals.

The human tongue is divided into two parts, an oral part at the front and a pharyngeal part at the back. The left and right sides are also separated along most of its length by a vertical section of fibrous tissue (the lingual septum) that results in a groove, the median sulcus, on the tongue's surface.

A ligament is a type of fibrous connective tissue in the body that connects bones to other bones. It also connects flight feathers to bones, in dinosaurs and birds. All 30,000 species of amniotes (land animals with internal bones) have ligaments.

It is also known as articular ligament, articular larua, fibrous ligament, or true ligament.

Granulation tissue is new connective tissue and microscopic blood vessels that form on the surfaces of a wound during the healing process. Granulation tissue typically grows from the base of a wound and is able to fill wounds of almost any size. Examples of granulation tissue can be seen in pyogenic granulomas and pulp polyps. Its histological appearance is characterized by proliferation of fibroblasts and thin-walled, delicate capillaries (angiogenesis), and infiltrated inflammatory cells in a loose extracellular matrix.

A skeleton is the structural frame that supports the body of most animals. There are several types of skeletons, including the exoskeleton, which is a rigid outer shell that holds up an organism's shape; the endoskeleton, a rigid internal frame to which the organs and soft tissues attach; and the hydroskeleton, a flexible internal structure supported by the hydrostatic pressure of body fluids.

Vertebrates are animals with an endoskeleton centered around an axial vertebral column, and their skeletons are typically composed of bones and cartilages. Invertebrates are other animals that lack a vertebral column, and their skeletons vary, including hard-shelled exoskeleton (arthropods and most molluscs), plated internal shells (e.g. cuttlebones in some cephalopods) or rods (e.g. ossicles in echinoderms), hydrostatically supported body cavities (most), and spicules (sponges). Cartilage is a rigid connective tissue that is found in the skeletal systems of vertebrates and invertebrates.

The human musculoskeletal system (also known as the human locomotor system, and previously the activity system) is an organ system that gives humans the ability to move using their muscular and skeletal systems. The musculoskeletal system provides form, support, stability, and movement to the body.

The human musculoskeletal system is made up of the bones of the skeleton, muscles, cartilage, tendons, ligaments, joints, and other connective tissue that supports and binds tissues and organs together. The musculoskeletal system's primary functions include supporting the body, allowing motion, and protecting vital organs. The skeletal portion of the system serves as the main storage system for calcium and phosphorus and contains critical components of the hematopoietic system.

Wound healing refers to a living organism's replacement of destroyed or damaged tissue by newly produced tissue.

In undamaged skin, the epidermis (surface, epithelial layer) and dermis (deeper, connective layer) form a protective barrier against the external environment. When the barrier is broken, a regulated sequence of biochemical events is set into motion to repair the damage. This process is divided into predictable phases: blood clotting (hemostasis), inflammation, tissue growth (cell proliferation), and tissue remodeling (maturation and cell differentiation). Blood clotting may be considered to be part of the inflammation stage instead of a separate stage.

Adipose tissue (also known as body fat or simply fat) is a loose connective tissue composed mostly of adipocytes. It also contains the stromal vascular fraction (SVF) of cells including preadipocytes, fibroblasts, vascular endothelial cells and a variety of immune cells such as adipose tissue macrophages. Its main role is to store energy in the form of lipids, although it also cushions and insulates the body.

Previously treated as being hormonally inert, in recent years adipose tissue has been recognized as a major endocrine organ, as it produces hormones such as leptin, estrogen, resistin, and cytokines (especially TNFα). In obesity, adipose tissue is implicated in the chronic release of pro-inflammatory markers known as adipokines, which are responsible for the development of metabolic syndrome—a constellation of diseases including type 2 diabetes, cardiovascular disease and atherosclerosis.

In biology, matrix (pl.: matrices) is the material (or tissue) in between cells within an eukaryotic organism.

The structure of connective tissues is an extracellular matrix. Fingernails and toenails grow from matrices. It is found in various connective tissues. It serves as a jelly-like structure instead of cytoplasm in connective tissue.

Cartilage is a resilient and smooth type of connective tissue. Semi-transparent and non-porous, it is usually covered by a tough and fibrous membrane called perichondrium. In tetrapods, it covers and protects the ends of long bones at the joints as articular cartilage, and is a structural component of many body parts including the rib cage, the neck and the bronchial tubes, and the intervertebral discs. In other taxa, such as chondrichthyans and cyclostomes, it constitutes a much greater proportion of the skeleton. It is not as hard and rigid as bone, but it is much stiffer and much less flexible than muscle or tendon. The matrix of cartilage is made up of glycosaminoglycans, proteoglycans, collagen fibers and, sometimes, elastin. It usually grows quicker than bone.

Because of its rigidity, cartilage often serves the purpose of holding tubes open in the body. Examples include the rings of the trachea, such as the cricoid cartilage and carina.

Skeletal muscle (commonly referred to as muscle) is one of the three types of vertebrate muscle tissue, the others being cardiac muscle and smooth muscle. They are part of the voluntary muscular system and typically are attached by tendons to bones of a skeleton. The skeletal muscle cells are much longer than in the other types of muscle tissue, and are also known as muscle fibers. The tissue of a skeletal muscle is striated – having a striped appearance due to the arrangement of the sarcomeres.

A skeletal muscle contains multiple fascicles – bundles of muscle fibers. Each individual fiber and each muscle is surrounded by a type of connective tissue layer of fascia. Muscle fibers are formed from the fusion of developmental myoblasts in a process known as myogenesis resulting in long multinucleated cells. In these cells, the nuclei, termed myonuclei, are located along the inside of the cell membrane. Muscle fibers also have multiple mitochondria to meet energy needs.

A nerve fascicle is a bundle of nerve fibers belonging to a nerve in the peripheral nervous system. A nerve fascicle is also called a fasciculus, as is a nerve tract in the central nervous system.

A nerve fascicle is enclosed by perineurium, a layer of fascial connective tissue. Each enclosed nerve fiber in the fascicle is enclosed by a connective tissue layer of endoneurium. Bundles of nerve fascicles are called fasciculi and are constituents of a nerve trunk. A main nerve trunk may contain a great many fascicles enclosing many thousands of axons.