CONNECTIVE TISSUE

The Major Structural Constituents of The Body

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

Categories of Tissue1. 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 undergodivision.

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

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