Chapter 4 - Connective Tissue

Articular cartilage in joints and cartilage of epiphyseal plates.

The primary functions of adipose tissue are to reduce heat loss through the skin, serve as an energy reserve, and support and protect organs.

Reticular fibers are plentiful in reticular connective tissue, which forms the stroma of many soft organs such as the spleen and lymph nodes, and they also help form the basement membrane.

Elastic connective tissue allows stretching of various organs, is strong, and can recoil to its original shape after being stretched.

Hyaluronic acid binds cells together, lubricates joints, and helps maintain the shape of the eyeballs.

Adipocytes are fat cells that store fats. They are found below the skin and around organs such as the heart and kidneys.

Bone tissue is classified as either compact or spongy, depending on how its extracellular matrix and cells are organized.

The central canal contains blood vessels and nerves.

Fibrocartilage has chondrocytes among clearly visible thick bundles of collagen fibers within the extracellular matrix and lacks perichondrium.

Elastic cartilage has chondrocytes in a threadlike network of elastic fibers within the extracellular matrix and has a perichondrium.

The functions of areolar connective tissue are strength, elasticity, and support.

Collagen fibers are very strong, resist pulling or stretching, are not stiff, and allow tissue flexibility. They are found in bone, cartilage, tendons, and ligaments.

Chondroitin sulfate is largely responsible for cartilage’s resilience.

Glycosaminoglycans (GAGs) are large organic molecules that are complex combinations of polysaccharides and proteins. They trap water, making the ground substance more jellylike.

Macrophages develop from monocytes and destroy bacteria and cell debris by phagocytosis.

Bones are composed of bone or osseous tissue, the periosteum, red and yellow bone marrow, and the endosteum.

Lacunae are small spaces between lamellae that contain mature bone cells called osteocytes.

White blood cells are involved in phagocytosis, immunity, and allergic reactions.

Support.

Areolar connective tissue 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).

A sprain is a stretched or torn ligament, often occurring in the ankle joint.

Connective tissue proper, supporting connective tissue, and liquid connective tissue.

Epithelial tissue can be arranged in single layers (simple epithelium) or multiple layers (stratified epithelium). The cell shapes include squamous (flat), cuboidal (cube-shaped), and columnar (tall and cylindrical).

Endothelium lines the interior surface of blood vessels and lymphatic vessels, while mesothelium forms the epithelial layer of serous membranes, such as the peritoneum, pleura, and pericardium.

Reticular connective tissue is a fine interlacing network of reticular fibers (a thin form of collagen fiber) and reticular cells.

Collagen fibers are strong, flexible bundles of the protein collagen, which is the most abundant protein in the body.

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.

Mesenchyme has irregularly shaped mesenchymal cells embedded in semifluid ground substance that contains delicate reticular fibers.

As a bluish-white, shiny substance.

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).

Adipose tissue is located wherever areolar connective tissue is found: in 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.

The perichondrium is a covering of dense irregular connective tissue that surrounds the surface of most cartilage and contains blood vessels and nerves.

Cartilage repair proceeds slowly because cartilage is avascular, meaning it lacks a blood supply.

Endocrine glands secrete hormones directly into the bloodstream, while exocrine glands release their secretions into ducts that lead to body surfaces or cavities. Examples of exocrine glands include merocrine (e.g., salivary glands), apocrine (e.g., mammary glands), and holocrine (e.g., sebaceous glands) glands.

Reticular connective tissue is located in the stroma (supporting framework) of the liver, spleen, lymph nodes, red bone marrow, reticular lamina of basement membrane, and around blood vessels and muscles.

Lamellae are concentric rings of extracellular matrix that consist of mineral salts and collagen fibers, giving bone its hardness, compressive strength, and tensile strength.

The formed elements suspended in blood plasma are red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes).

In the umbilical cord of the fetus.

Areolar connective tissue, adipose tissue, and reticular connective tissue.

Dense regular connective tissue provides strong attachment between various structures and withstands pulling (tension) along the long axis of fibers.

In newborns, brown adipose tissue generates heat to maintain proper body temperature.

Postsurgical complications of liposuction may include fat entering blood vessels and obstructing blood flow, infection, loss of feeling in the area, fluid depletion, injury to internal structures, and severe postoperative pain.

Simple squamous epithelium consists of a single layer of flat cells, which allows for efficient diffusion and filtration. It is found in areas where rapid exchange of substances is necessary, such as the alveoli of the lungs and the lining of blood vessels.

The skeletal system is made up of cartilage, joints, and bones.

Macrophages are phagocytes that develop from monocytes. They can be fixed in a particular tissue or wander throughout the tissue to gather at sites of infection or inflammation to carry on phagocytosis.

Plasma cells develop from B lymphocytes and secrete antibodies that attack and neutralize foreign substances.

Fibrocartilage is located in the pubic symphysis, intervertebral discs, menisci of the knee, and portions of tendons that insert into cartilage.

Elastic cartilage provides strength and elasticity and maintains the shape of certain structures.

Dense irregular connective tissue is made up of collagen fibers, usually irregularly arranged with a few fibroblasts.

Embryonic connective tissue and mature connective tissue.

In ultrasound-assisted liposuction (UAL), a special cannula delivers high-frequency sound waves that liquefy the fat cells, and the liquid is then removed by suction.

During interstitial growth, cartilage increases rapidly in size due to the division of existing chondrocytes and the continuous deposition of increasing amounts of extracellular matrix by the chondrocytes.

The two basic elements of connective tissue are the extracellular matrix and cells. The extracellular matrix consists of protein fibers and ground substance.

The ground substance is the component of connective tissue between the cells and fibers. It can be fluid, semifluid, gelatinous, or calcified and supports cells, binds them together, stores water, and provides a medium for exchange of substances between the blood and cells.

Dermatan sulfate is found in the skin, tendons, blood vessels, and heart valves, providing support and adhesiveness.

In lacunae surrounded by perichondrium.

Hyaline cartilage.

Elastic fibers provide strength and stability, can be stretched up to 150% of their relaxed length without breaking, and return to their original shape after being stretched.

The three types of cartilage are hyaline cartilage, fibrocartilage, and elastic cartilage.

The two basic patterns of cartilage growth are interstitial growth and appositional growth.

Connective tissue binds together, supports, and strengthens other body tissues; protects and insulates internal organs; compartmentalizes structures; serves as a major transport system (blood); stores energy reserves (adipose tissue); and is the main source of immune responses.

Reticular connective tissue 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.

Canaliculi are networks of minute canals containing the processes of osteocytes, providing routes for nutrients to reach osteocytes and for wastes to leave them.

Platelets participate in blood clotting.

Forms almost all other types of connective tissue.

Mucous (mucoid) connective tissue has widely scattered fibroblasts embedded in viscous, jellylike ground substance that contains fine collagen fibers.

Areolar connective tissue is found in and around nearly every body structure: in the subcutaneous layer deep to the skin, papillary region of the dermis of the skin, lamina propria of mucous membranes, and around blood vessels, nerves, and body organs.

Collagen fibers, elastic fibers, and reticular fibers.

The cells of mature cartilage are called chondrocytes.

Common characteristics of epithelial tissues include closely packed cells with minimal extracellular material, a free surface exposed to the body exterior or internal cavity, a basement membrane anchoring the tissue, avascularity (lack of blood vessels), and high regenerative capacity.

During appositional growth, cells in the inner cellular layer of the perichondrium differentiate into chondroblasts, which surround themselves with extracellular matrix and become chondrocytes, causing the cartilage to grow in width.

Fibroblasts are large, flat cells with branching processes found in all general connective tissues. They are responsible for secreting fibers and ground substance of the extracellular matrix.

The four parts of an osteon are lamellae, lacunae, canaliculi, and a central canal.

The main adhesion protein in connective tissues is fibronectin, which binds to both collagen fibers and ground substance, linking them together and attaching cells to the ground substance.

Elastic cartilage is located in the lid on top of the larynx (epiglottis), part of the external ear (auricle), and auditory (eustachian) tubes.

They 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.

Adipose tissue is an excellent source of stem cells, which are used in rejuvenation medicine to repair or replace damaged tissue.

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.

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 strength of cartilage is due to its collagen fibers, and its resilience (ability to assume its original shape after deformation) is due to chondroitin sulfate.

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.

Chondroitin sulfate provides support and adhesiveness in cartilage, bone, skin, and blood vessels.

Provides smooth surfaces for movement at joints, flexibility, and support.

Dense irregular connective tissue provides tensile (pulling) strength in many directions.

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 and a powerful vacuum-pressure unit.

Cryolipolysis, also known as CoolSculpting, is a procedure that destroys 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.

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.

Eosinophils are white blood cells that migrate to sites of parasitic infection and allergic responses.

Elastic fibers are stretchable but strong fibers made of proteins, elastin, and fibrillin. They are found in skin, blood vessels, and lung tissue.

Red blood cells transport oxygen to body cells and remove some carbon dioxide from them.

Almost exclusively under skin and along developing bones of embryo; some in adult connective tissue, especially along blood vessels.

Fibrocartilage supports and joins structures together. Its strength and rigidity make it the strongest type of cartilage.

At ends of long bones, anterior ends of ribs, nose, parts of larynx, trachea, bronchi, bronchial tubes, embryonic and fetal skeleton.

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.

Cartilage secretes an antiangiogenesis factor, which prevents blood vessel growth.

Laser-assisted liposuction involves a special cannula that delivers laser energy to liquefy fat cells, which are then removed by suction.

Fibroblasts are large flat cells that move through connective tissue and secrete fibers and ground substance.

Bones store calcium and phosphorus, house red bone marrow (which produces blood cells), and contain yellow bone marrow (a storage site for triglycerides).

Mast cells are abundant along blood vessels. They produce histamine, which dilates small blood vessels during inflammation and kills bacteria.

The extracellular matrix of blood tissue is called blood plasma.

Mesenchyme and mucous connective tissue.

A resilient gel.

Dense regular connective tissue is mainly composed of collagen fibers regularly arranged in bundles with fibroblasts in rows between them.

White adipose tissue stores triglycerides and is the most common type in adults. Brown adipose tissue has a rich blood supply and numerous pigmented mitochondria that participate in aerobic cellular respiration, and it is more common in fetuses and infants.

Embryonic connective tissue is present in an embryo or fetus, while mature connective tissue is present at birth and persists throughout life.

Elastic connective tissue is located in lung tissue, walls of elastic arteries, trachea, bronchial tubes, true vocal cords, suspensory ligaments of the penis, and some ligaments between vertebrae.

The three types of dense connective tissue are dense regular connective tissue, dense irregular connective tissue, and elastic connective tissue.

Neutrophils are white blood cells that migrate to sites of infection and destroy microbes by phagocytosis.

The basic unit of compact bone is an osteon or haversian system.

Keratan sulfate is found in bone, cartilage, and the cornea of the eye, providing support and adhesiveness.