Dense regular connective tissue forms tendons (attach muscle to bone), most ligaments (attach bone to bone), and aponeuroses (sheetlike tendons that attach muscle to muscle or muscle to bone).
Mucous (mucoid) connective tissue is located in the umbilical cord of the fetus.
Liposuction is a surgical procedure that involves suctioning out small amounts of adipose tissue from various areas of the body using a stainless steel tube called a cannula, with the assistance of a powerful vacuum-pressure unit.
Tumescent liposuction is a variation of liposuction where large amounts of fluid are injected during the procedure, causing the area to become engorged with fluid, which helps separate the adipose cells and allows the cannula to move more easily through fat.
Bone tissue is classified as either compact or spongy, depending on how its extracellular matrix and cells are organized.
Hyaline cartilage provides smooth surfaces for movement at joints, flexibility, and support. It is the weakest type of cartilage and can be fractured.
Areolar connective tissue is one of the most widely distributed connective tissues; it consists of fibers (collagen, elastic, reticular) arranged randomly and several kinds of cells (fibroblasts, macrophages, plasma cells, adipocytes, mast cells, and a few white blood cells) embedded in semifluid ground substance (hyaluronic acid, chondroitin sulfate, dermatan sulfate, and keratan sulfate).
The functions of areolar connective tissue include providing strength, elasticity, and support.
The functions of adipose tissue include reducing heat loss through the skin, serving as an energy reserve, supporting and protecting organs, and in newborns, generating heat to maintain proper body temperature. Adipose tissue is also an excellent source of stem cells used in rejuvenation medicine to repair or replace damaged tissue.
Mast cells are involved in the inflammatory response, the body's reaction to injury or infection, and can also bind to, ingest, and kill bacteria.
A sprain is a stretched or torn ligament, often occurring in the ankle joint. Due to poor blood supply, healing is slow, and completely torn ligaments require surgical repair.
Dense irregular connective tissue provides tensile (pulling) strength in many directions.
The perichondrium is a covering of dense irregular connective tissue that surrounds the surface of most cartilage. It contains blood vessels and nerves and is the source of new cartilage cells.
Elastic connective tissue contains predominantly elastic fibers with fibroblasts between them. It allows stretching of various organs and can recoil to its original shape after being stretched.
Macrophages are phagocytes that develop from monocytes, a type of white blood cell. Fixed macrophages reside in a particular tissue, while wandering macrophages can move throughout the tissue and gather at sites of infection or inflammation.
Lacunae are small spaces between lamellae that contain mature bone cells called osteocytes.
Red blood cells transport oxygen to body cells and remove some carbon dioxide from them.
Mesenchyme is almost exclusively found under the skin and along developing bones of the embryo, with some present in adult connective tissue, especially along blood vessels.
Laser-assisted liposuction is a procedure where a special cannula delivers laser energy that liquefies the fat cells, and the liquid is then removed by suction.
Appositional growth is the growth at the outer surface of the tissue, where cells in the inner cellular layer of the perichondrium differentiate into chondroblasts, which then become chondrocytes and contribute to the growth in width of the cartilage.
Elastic cartilage is located in the lid on top of the larynx (epiglottis), part of the external ear (auricle), and auditory (eustachian) tubes.
Collagen fibers are very strong, resist pulling or stretching, and allow tissue flexibility. They are the most abundant protein in the body, found in bone, cartilage, tendons, and ligaments.
Macrophages develop from monocytes and destroy bacteria and cell debris by phagocytosis.
Mast cells are abundant along blood vessels. They produce histamine, which dilates small blood vessels during inflammation and kills bacteria.
Hyaline cartilage is the most abundant cartilage in the body and is found at the ends of long bones, anterior ends of ribs, nose, parts of larynx, trachea, bronchi, bronchial tubes, and in the embryonic and fetal skeleton.
Dense irregular connective tissue is made up of collagen fibers, usually irregularly arranged with a few fibroblasts.
The types of loose connective tissue are areolar connective tissue, adipose tissue, and reticular connective tissue.
Ultrasound-assisted liposuction (UAL) is a procedure where a special cannula delivers high-frequency sound waves that liquefy the fat cells, and the liquid is then removed by suction.
Dense connective tissue is a type of connective tissue proper that contains more fibers, which are thicker and more densely packed, but have considerably fewer cells than loose connective tissue.
The function of fibrocartilage is to support and join structures together. Its strength and rigidity make it the strongest type of cartilage.
Chondroitin sulfate provides support and adhesiveness in cartilage, bone, skin, and blood vessels.
Reticular fibers are made of collagen and glycoproteins. They provide support in blood vessel walls and form branching networks around various cells such as fat, smooth muscle, and nerve cells.
Ground substance is the material between cells and fibers. It is made of water and organic molecules such as hyaluronic acid and chondroitin sulfate. It supports cells and fibers, binds them together, and provides a medium for exchanging substances between blood and cells.
Dense regular connective tissue forms shiny white extracellular matrix; mainly collagen fibers regularly arranged in bundles with fibroblasts in rows between them. Collagen fibers are not living, so damaged tendons and ligaments heal slowly.
Dense irregular connective tissue often occurs in sheets, such as fasciae (tissue beneath skin and around muscles and other organs), reticular (deeper) region of dermis of skin, fibrous pericardium of heart, periosteum of bone, perichondrium of cartilage, joint capsules, membrane capsules around various organs (kidneys, liver, testes, lymph nodes); also in heart valves.
Chondrocytes are the cells of mature cartilage that occur singly or in groups within spaces called lacunae in the extracellular matrix.
Adipose tissue has cells derived from fibroblasts (called adipocytes) that are specialized for storage of triglycerides (fats) as a large, centrally located droplet. The cell fills up with a single, large triglyceride droplet, and the cytoplasm and nucleus are pushed to the periphery of the cell.
Cartilage consists of a dense network of collagen fibers and elastic fibers firmly embedded in chondroitin sulfate, a gel-like component of the ground substance. It can endure more stress than loose and dense connective tissues due to its collagen fibers and chondroitin sulfate.
Elastic fibers are smaller in diameter than collagen fibers, can be stretched up to 150% of their relaxed length without breaking, and return to their original shape after being stretched. They are found in skin, blood vessel walls, and lung tissue.
Lamellae are concentric rings of extracellular matrix that consist of mineral salts (mostly calcium and phosphates), which give bone its hardness and compressive strength, and collagen fibers, which give bone its tensile strength.
The formed elements in blood are red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes).
Mucous (mucoid) connective tissue has widely scattered fibroblasts embedded in a viscous, jellylike ground substance that contains fine collagen fibers.
Connective tissue consists of two basic elements: extracellular matrix and cells.
White adipose tissue is the most common type in adults and is specialized for storing triglycerides. Brown adipose tissue (BAT) is darker due to a very rich blood supply and numerous pigmented mitochondria that participate in aerobic cellular respiration. BAT is widespread in the fetus and infant, while adults have only small amounts.
Embryonic connective tissue is present in an embryo or fetus, while mature connective tissue is present at birth and persists throughout life. Mature connective tissue includes connective tissue proper, supporting connective tissue, and liquid connective tissue.
Adipocytes are fat cells that store fats. They are found below the skin and around organs such as the heart and kidneys.
Elastic fibers are stretchable but strong fibers made of proteins, elastin, and fibrillin. They are found in skin, blood vessels, and lung tissue.
The extracellular matrix is the material located between the widely spaced cells of connective tissue. It consists of protein fibers and ground substance.
Chondroitin sulfate and glucosamine are used as nutritional supplements to promote and maintain the structure and function of joint cartilage, provide pain relief from osteoarthritis, and reduce joint inflammation.
Hyaluronic acid is a viscous, slippery substance that binds cells together, lubricates joints, and helps maintain the shape of the eyeballs.
Eosinophils are white blood cells that migrate to sites of parasitic infection and allergic responses.
Mesenchyme forms almost all other types of connective tissue.
The three types of cartilage are hyaline cartilage, fibrocartilage, and elastic cartilage.
Fibrocartilage has chondrocytes among clearly visible thick bundles of collagen fibers within the extracellular matrix and lacks perichondrium.
Adipocytes, or fat cells, are connective tissue cells that store triglycerides (fats). They are found deep to the skin and around organs such as the heart and kidneys.
Connective tissue is classified into embryonic connective tissue (mesenchyme and mucous connective tissue) and mature connective tissue. Mature connective tissue includes connective tissue proper (loose and dense connective tissue), supporting connective tissue (cartilage and bone), and liquid connective tissue (blood and lymph).
The basic unit of compact bone is an osteon or haversian system.
Blood plasma is a pale yellow fluid that consists mostly of water with a wide variety of dissolved substances—nutrients, wastes, enzymes, plasma proteins, hormones, respiratory gases, and ions.
An antiangiogenesis factor is a substance that prevents blood vessel growth. Cartilage secretes this factor, which is why it does not have a blood supply.
Fibroblasts are large, flat cells with branching processes. They are present in all general connective tissues and are usually the most numerous.
Elastic cartilage has chondrocytes in a threadlike network of elastic fibers within the extracellular matrix and has a perichondrium present.
Reticular fibers are much thinner than collagen fibers and form branching networks. They provide support and strength and are plentiful in reticular connective tissue, forming the stroma of soft organs like the spleen and lymph nodes.
Fibroblasts are large flat cells that move through connective tissue and secrete fibers and ground substance.
Collagen fibers are strong, flexible bundles of the protein collagen, the most abundant protein in the body.
Proteoglycans form a core protein with glycosaminoglycans (GAGs) projecting from the protein like the bristles of a brush.
Dense regular connective tissue provides strong attachment between various structures and withstands pulling (tension) along the long axis of fibers.
The function of mucous (mucoid) connective tissue is to provide support.
Areolar connective tissue is located in and around nearly every body structure, including the subcutaneous layer deep to the skin, the papillary (superficial) region of the dermis of the skin, the lamina propria of mucous membranes, and around blood vessels, nerves, and body organs.
Adipose tissue is located wherever areolar connective tissue is found, including the subcutaneous layer deep to the skin, around the heart and kidneys, yellow bone marrow, padding around joints, and behind the eyeball in the eye socket.
Reticular connective tissue is a fine interlacing network of reticular fibers (a thin form of collagen fiber) and reticular cells. It forms the stroma of organs, binds smooth muscle tissue cells, and filters and removes worn-out blood cells in the spleen and microbes in lymph nodes.
The function of elastic cartilage is to provide strength and elasticity and to maintain the shape of certain structures.
Glycosaminoglycans (GAGs) are large organic molecules that are complex combinations of polysaccharides and proteins. They include hyaluronic acid, chondroitin sulfate, dermatan sulfate, and keratan sulfate.
Canaliculi are networks of minute canals containing the processes of osteocytes, providing routes for nutrients to reach osteocytes and for wastes to leave them.
White blood cells are involved in phagocytosis, immunity, and allergic reactions.
Fibronectin is the main adhesion protein of connective tissues. It binds to both collagen fibers and ground substance, linking them together, and also attaches cells to the ground substance.
Hyaline cartilage contains a resilient gel as ground substance and appears in the body as a bluish-white, shiny substance. It can stain pink or purple when prepared for microscopic examination, and fine collagen fibers are not visible with ordinary staining techniques. Prominent chondrocytes are found in lacunae surrounded by perichondrium, except in articular cartilage in joints and cartilage of epiphyseal plates.
Mesenchyme is a type of embryonic connective tissue with irregularly shaped mesenchymal cells embedded in a semifluid ground substance that contains delicate reticular fibers.
Connective tissue proper is a type of mature connective tissue that is flexible and has a viscous ground substance with abundant fibers.
Chondroitin sulfate in the extracellular matrix is largely responsible for cartilage’s resilience, making it a strong, firm material that resists tension, compression, and shear.
Interstitial growth is the growth from within the tissue, where cartilage increases rapidly in size due to the division of existing chondrocytes and the continuous deposition of extracellular matrix.
Plasma cells are found in many places in the body, especially in connective tissue of the gastrointestinal and respiratory tracts.
The ground substance is the component of connective tissue between the cells and fibers. It may be fluid, semifluid, gelatinous, or calcified, and it supports cells, binds them together, stores water, and provides a medium for exchange of substances between the blood and cells.
Bones store calcium and phosphorus; house red bone marrow, which produces blood cells; and contain yellow bone marrow, a storage site for triglycerides.
A central canal or haversian canal contains blood vessels and nerves.
Cryolipolysis, also known as CoolSculpting, refers to the destruction of fat cells by the external application of controlled cooling, which kills the fat cells while sparing damage to nerve cells, blood vessels, and other structures.
Fibrocartilage is located in the pubic symphysis (where hip bones join anteriorly), intervertebral discs, menisci (cartilage pads) of the knee, and portions of tendons that insert into cartilage.
Leukocytes, or white blood cells, are not found in significant numbers in normal connective tissue but migrate from blood into connective tissue in response to certain conditions. For example, neutrophils gather at sites of infection, and eosinophils migrate to sites of parasitic invasions and allergic responses.
Neutrophils are white blood cells that migrate to sites of infection and destroy microbes by phagocytosis.
Plasma cells develop from B lymphocytes. They secrete antibodies that attack and neutralize foreign substances.
Spongy bone consists of columns of bone called trabeculae, which contain lamellae, osteocytes, lacunae, and canaliculi. Spaces between trabeculae are filled with red bone marrow.
Platelets participate in blood clotting.
