Connective Tissue • Connective Tissue – Connect body parts. • It is found everywhere in the body. • It is the most abundant and widely distributed of the tissue types.
Common Characteristics of Connective Tissue • Variation of blood supply • Most connective tissues are well vascularized, but there are exceptions. • Tendons and ligaments have poor blood supply and cartilages are avascular. Therefore, these structures heal very slowly. • Extracellular matrix • Connective tissues are made up of many different types of cells plus varying amounts of a nonliving substance found outside the cells, called the extracellular matrix.
Extracellular Matrix • The extracellular matrix has two main elements: • A structureless ground substance • Fibers
Ground Substance of the Extracellular Matrix • Composed of: • Mostly water • Some adhesion proteins • Serve as glue that allows the cells to attach themselves to the matrix fibers embedded in the matrix. • Large, charged polysaccharide molecules. • Trap water as they intertwine. • As the abundance of these polysaccharide molecules increases, they cause the matrix to vary from fluid to gel-like to firm to rock-hard.
Fibers of the Extracellular Matrix • Various types and amounts of fibers are deposited in the matrix depending on the connective tissue type and include: • Collagen fibers (white) • Elastic fibers (yellow) • Reticular fibers (fine collagen)
Connective Tissue Variation • All connective tissue consists of living cells surrounded by a matrix. Their major differences reflect fiber type and the number of fibers in the matrix. • At one extreme, fat tissue is composed mostly of cells, and the matrix is soft. • At the opposite extreme, bone and cartilage have very few cells and large amounts of hard matrix, which makes them extremely strong.
Connective Tissue Functions • Protecting • Supporting • Binding together other body tissues • Serve as a water reservoir (less known function) • Ground substance has the ability to absorb large amounts of water.
Types of Connective Tissue • Bone • Cartilage (3 kinds) • Dense Connective Tissue • Loose Connective Tissue (3 types) • Blood
Bone • Bone – Composed of bone cells sitting in cavities called lacunae and surrounded by layers of a very hard matrix that contains calcium salts in addition to large numbers of collagen fibers. • Also called osseous tissue. • Because of its rocklike hardness, bone has an exceptional ability to protect and support other body organs.
Cartilage • Less hard and more flexible than bone. • It is found only in a few places in the body.
Three Types of Cartilage: • Hyaline Cartilage – Has abundant collagen fibers hidden by a rubbery matrix with a glassy, blue-white appearance. • Found in the larynx, attaches the ribs to the breastbone, and covers the ends of bones at the joints. • The skeleton of a fetus is made of hyaline cartilage, but by the time the baby is born most of that cartilage has been replaced by bone. • Most abundant and widespread in the body.
Three Types of Cartilage • Fibrocartilage – Highly compressible • Forms the cushionlike disks between the vertebrae of the spinal column. • Elastic Cartilage – Very elastic • Found where structure with elasticity is desired such as the external ear.
Dense Connective Tissue • Has collagen fibers as its main matrix element. • Rows of fibroblasts that manufacture the fibers. • Also called dense fibrous tissue. • Forms strong, ropelike structures. • Examples: • Tendons: Attach skeletal muscles to bones. • Ligaments: Connect bones to bones. • Also makes up the lower layers of the skin (dermis) where it is arranged in sheets.
Loose Connective Tissue • Softer and have more cells and fewer fibers than any other connective tissue type except blood. • Three types: • Areolar Tissue • Adipose Tissue • Reticular Connective Tissue
Areolar Tissue • Areolar Tissue – Soft, pliable “cobwebby” tissue that cushions and protects the body organs it wraps. • Most widely distributed connective tissue variety in the body. • Functions as a universal packing tissue and connective tissue “glue” because it helps to hold the internal organs together and in their proper position.
Areolar Tissue • Because of its fluid nature, areolar connective tissue provides a reservoir of water and salts for the surrounding tissues. • Body cells obtain their nutrients from areolar CT and release their wastes into this “tissue fluid.” • When a body region is inflamed, the areolar tissue in the area soaks up the excess fluid, and the area swells, a condition known as edema. • Many phagocytes wander through this area scavenging for bacteria, dead cells, and other debris, which they destroy.
Adipose Tissue • Adipose Tissue – Commonly called fat; • A droplet of stored oil occupies most of the fat cell’s volume and compresses the nucleus, displacing it to one side.
Adipose Tissue • Functions: • Adipose tissue forms the subcutaneous tissue beneath the skin, where it insulates the body and protects it from extremes of both heat and cold. • Protects some organs individually. Fat cushions the kidneys and eyeball sockets. • Fat deposits in the body (hips and breasts), where fat is stored and available for fuel if needed.
Reticular Connective Tissue • Reticular Connective Tissue • Type of loose irregular connective tissue. • Has a network of reticular fibers; which are synthesized by fibroblasts called reticular cells. • Forms a supporting framework to support the lymphocytes in lymphoid organs (lymph nodes, red bone marrow, and spleen).
Blood • Blood– Vascular tissue • Consists of blood cells, surrounded by a nonliving, fluid matrix called blood plasma. • The fibers of blood are soluble protein molecules that become visible only during blood clotting. • Blood is quite atypical as connective tissues go. • Blood is the transport vehicle for the cardiovascular system. • Carries nutrients, wastes, respiratory gases, and many other substances throughout the body.