Lecture 3: Tissue Level of Organization - Connective Tissue

Vocabulary flashcards covering the components, cell types, extracellular matrix, fiber types, and classification of connective tissues from Lecture 3.

Connective tissue

A widespread body tissue that binds, connects, supports, and strengthens other tissues, protects internal organs, forms compartments, acts as a major transport system (blood), and stores energy (adipose tissue).

Extracellular matrix (ECM)

The material located between cells in connective tissue consisting of protein fibers and ground substance, whose structure mirrors tissue function and is secreted by connective tissue cells.

Mesenchymal cells

Embryonic cells that give rise to all connective tissue cells.

Blast cells

Immature connective tissue cells (such as fibroblasts, chondroblasts, and osteoblasts) that retain the capacity to divide and continuously secrete extracellular matrix.

Cyte cells

Mature connective tissue cells (such as chondrocytes and osteocytes) that have reduced capacity for cell division, do not produce extracellular matrix, and function primarily to monitor and maintain the ECM.

Fibroblasts

Large, flat connective tissue cells with branching processes present in all connective tissues that migrate through the tissue and secrete all fibers (including collagen) and ground substance components.

Neutrophils

White blood cells that migrate from the blood into connective tissue specifically at sites of infection.

Eosinophils

White blood cells that migrate into connective tissues in response to allergic reactions.

Plasma cells

Antibody-secreting connective tissue cells developed from B lymphocytes, primarily located in the gastrointestinal tract, respiratory tract, lymph nodes, spleen, and red bone marrow.

Mast cells

Connective tissue cells situated alongside blood vessels that produce histamine to dilate small blood vessels during inflammation, injury, and infection.

Histamine

A chemical produced by mast cells that dilates small blood vessels during inflammation, injury, and infection.

Macrophages

Phagocytic cells developed from monocytes that engulf and digest bacteria and cellular debris in connective tissues.

Fixed macrophages

Macrophages that permanently reside within a specific tissue, such as alveolar macrophages in the lungs or splenic macrophages in the spleen.

Wandering macrophages

Motile macrophages that travel through tissues to reach sites of infection or inflammation to carry out phagocytosis.

Adipocytes

Specialized connective tissue cells that store triglycerides (fat), found deep to the skin and surrounding organs such as the heart and kidneys.

Ground substance

The component of the extracellular matrix between cells and fibers that may be fluid, semifluid, gelatinous, or calcified; it supports and binds cells, stores water, and facilitates substance exchange with blood.

Glycosaminoglycans (GAGs)

Large organic polysaccharide complexes found in ground substance (such as hyaluronic acid, chondroitin sulfate, dermatan sulfate, and keratan sulfate) that trap water to give the ground substance a jelly-like texture.

Proteoglycans

Large complexes formed when glycosaminoglycans (excluding hyaluronic acid) bind covalently to proteins in the ground substance.

Hyaluronic acid

A viscous, slippery glycosaminoglycan that lubricates joints and does not bind to proteins to form proteoglycans.

Chondroitin sulfate

A specific glycosaminoglycan found in the ground substance of cartilage.

Dermatan sulfate

A specific glycosaminoglycan component of the ground substance found in skin.

Keratan sulfate

A specific glycosaminoglycan component of the ground substance found in bone, cartilage, and the cornea of the eye.

Fibronectin

The main adhesion protein of ground substance that links various components of the ground substance together.

Collagen fibers

Very strong, flexible fibers made of collagen—the most abundant protein in the body—that resist pulling forces; highly prevalent in bone, cartilage, tendons, and ligaments.

Elastic fibers

Fibrous network structures made of elastin surrounded by the glycoprotein fibrillin that can stretch up to $150\%$ of their length without breaking and recoil to original shape; common in skin, blood vessel walls, and lung tissue.

Reticular fibers

Fine bundles of fibers coated with glycoprotein that are thinner than collagen fibers, supporting blood vessel walls and forming supportive networks around cells in areolar tissue, adipose tissue, nerve fibers, smooth muscle, spleen, and lymph nodes.

Tendons

Connective tissue cords rich in collagen fibers that attach muscle to bone, characterized by a poor blood supply.

Ligaments

Connective tissue bands rich in collagen fibers that connect bone to bone.

Loose connective tissues

A category of mature connective tissue that includes areolar connective tissue, adipose tissue, and reticular connective tissue.

Dense connective tissues

A category of mature connective tissue that includes dense regular connective tissue, dense irregular connective tissue, and elastic connective tissue.

Cartilage

A firm, flexible mature connective tissue categorized into hyaline cartilage, fibrocartilage, and elastic cartilage, distinguished by having no blood supply.

Liquid connective tissue

A class of mature connective tissue consisting of blood tissue and lymph.

Embryonic connective tissues

The primary connective tissue group of the developing embryo, consisting of mesenchyme and mucous connective tissue.