CONNECTIVE TISSUE The Major Structural Constituents of The Body

Tissue: A Definition A group of connected, interdependent cells that cooperate to perform a specific function

Categories of Tissue 1. Epithelial Tissue 2. Connective Tissue 3. Muscle Tissue 4. Nervous Tissue

Function of CT Responsible for providing and maintaining form in the body. Provide a matrix that connects and binds cells and organs and ultimately supports body.

Components of CT Cells Extracellular matrix –Fibers Collagenous, reticular, elastic –Ground substance Hydrophilic macromolecules (glycoproteins, glycosaminoglycans, proteogycans) bind to receptors on cells and add strength and rigidity to matrix

CT Cells Fibroblasts Synthesis of all fibers, ground substance. Mast cells* –Contain granules with histamine, heparin, leukotrienes. Macrophages* –Phagocytosis Plasma cells* –Derived from lymphocytes, produce antibodies. * Originate from hematopoietic stem cells in bone marrow, circulate in blood, move to CT where they remain and perform their functions

Fibroblasts Synthesize collagen, elastin and macromolecules of ground substance. Rarely rarely undergo division.

Fibroblasts (inactive)

Collagenous Fibers Collagenous –Most common protein in the body (30% of dry weight) –Stain pink –Make up mesenteries, tendons, cartilage, ligaments, lamina propria, every organ.

Collagenous Fibers (Dense Irregular CT)

Reticular CT (Adrenal Cortex)

Reticular Fibers Reticular –Are not stained by H&E, stain black with silver –Very delicate; hold cells together in organs. –Provide framework for spleen, lymph nodes, red bone marrow, liver, endocrine glands. –Makes flexible network in arteries, intestinal muscle layer, uterus

Reticular Fibers

Elastic Fibers Stretchable, highly resistant to pulling forces. Found in arteries, cartilage, mesenteries

Extracellular Matrix Fibers –Collagenous (collagen) –Reticular (collagen) –Elastic (elastin) Amorphous ground substance –Gel-like matrix in which fibers, cells are embedded and through which fluid diffuses. Tissue fluid

Reticular CT

Collagen, Elastic Fibers (Areolar CT)

ADULT CT CT proper –Loose –Reticular –Adipose –Dense irregular –Dense regular Collagenous Elastic Specialized CT –Cartilage –Bone –Blood

Loose (Areolar) Conn Tissue Structure Many cells Jello-like matrix Collagen + elastic fibers

Binding Tissue Function: Binds organ parts together Sample Locations: Skin, kidney, lungs

Loose CT

Elastic, Reticular Fibers

Dense Irregular CT

Section of rat skin. The subepithelial connective tissue (dermis) is loose connective tissue. In this area, the cells, most of which are fibroblasts, are abundant. The deepest part of the dermis consists of dense irregular connective tissue, which contains many randomly oriented thick collagen fibers, scarce ground substance, and few cells. H&E stain. Medium magnification. (Courtesy of TMT Zorn.)

Elastic Connective Tissue

Dense Regular C T Structure Few cells Dense matrix Aligned collagen fibers

DENSE CT