Connective Tissue

What dominates in the epithelium?

Cells

What dominates in connective tissue?

ECM

What dictates the dominance of cells or ECM in epithelium and connective tissue?

Structural organization and Functional requirements

What supports and physically connects tissues and cells?

Connective tissues

What contributes to the formation and organization of organs?

Connective tissues

What provides metabolic support through interstitial fluid?

Connective tissues

What is connective tissue characterized by?

Abundant extracellular matrix (ECM)

What allows nutrients to pass from connective tissue to cells?

Water within the ground substance

What allows cells to pass from connective tissue to the blood supply?

Water within the ground substance

What components lead to different structure, function, and pathologic responses in connective tissue?

Different amounts and combinations of Cells, Fibers, and Ground substance

What is the embryonic origin of mesenchyme?

Mesoderm

What does mesenchyme differentiate into?

Connective Tissue Proper, Cartilage, and Bone

What are the resident cells of connective tissue?

Fibroblasts, Adipocytes, Macrophages, and Mast cells

What are the transient cells of connective tissue?

Plasma cells and Leukocytes

Which type of fibroblast has abundant cytoplasm?

Active fibroblast

Which type of fibroblast has extensive RER?

Active fibroblast

Which type of fibroblast has a well-developed Golgi?

Active fibroblast

Which type of fibroblast has a large, euchromatic nucleus?

Active fibroblast

Which type of fibroblast has a prominent nucleolus?

Active fibroblast

Which type of fibroblast has less cytoplasm?

Quiescent fibroblast

Which type of fibroblast has less RER?

Quiescent fibroblast

Which type of fibroblast has less prominent organelles?

Quiescent fibroblast

Which type of fibroblast has a darker, heterochromatic nucleus?

Quiescent fibroblast

Which type of fibroblast has a less prominent nucleus?

Quiescent fibroblast

What induces fibroblast proliferation in tissue repair?

Growth factors

What does fibroblast proliferation lead to in tissue repair?

ECM production

What does ECM production lead to?

Tissue repair

What functional characteristic do myofibroblasts possess?

Contractile

In what process are myofibroblasts important?

Wound healing

What form of actin are myofibroblasts enriched in?

A form of actin also found in smooth muscle cells

What is the embryonic origin of adipocytes?

Mesenchymally derived

What are adipocytes specialized for?

Lipid storage

What may adipocytes contribute to?

Heat production

What cells cushion and insulate tissues?

Adipocytes

What significance do adipocytes hold?

Major metabolic significance

What is a major function of macrophages involving engulfment?

Phagocytosis

What are the major functions of macrophages?

Phagocytosis, Removal of cellular debris, Removal of extracellular material, Antigen presentation, and Tissue repair

Where are mast cells located?

In connective tissue

Where are mast cells abundant?

Near small blood vessels

What do mast cells contain?

Basophilic secretory granules

What processes are mast cells important in?

Inflammation, Innate immunity, Tissue repair, and Immediate hypersensitivity reactions

What do plasma cells derive from?

Lymphocytes

What is the primary function of plasma cells?

Antibody production

What are the histologic features of plasma cells?

Ovoid cell, Eccentric nucleus, Basophilic cytoplasm, Abundant RER, and Prominent Golgi region

What are the wandering cells of connective tissue called?

Leukocytes

What are leukocytes derived from?

Circulating blood cells

How do leukocytes enter connective tissue?

Through venules

During what process do leukocytes increase?

Inflammation

What responses do leukocytes participate in?

Immune and defensive responses

What substance released by mast cells leads to increased vascular permeability?

Histamine

What does increased vascular permeability lead to?

Edema

What are the major signs of inflammation?

Redness, Swelling, Heat, and Pain

What is the attraction of leukocytes into inflamed tissue called?

Chemotaxis

What are elongated structures formed from proteins that polymerize after secretion from fibroblasts called?

Fibers

What are the three major types of fibers in connective tissue?

Collagen fibers, Reticular fibers, and Elastic fibers

What is the major structural component of connective tissue?

Collagen fibers

What fibers are strong and resistant to tensile forces?

Collagen fibers

What is the most abundant protein in the human body?

Collagen

What is the major product of fibroblasts?

Collagen fibers

What molecules assemble to form collagen fibrils?

Procollagen molecules

What do collagen fibrils form?

Collagen fibers

What do collagen fibers form?

Collagen bundles

What processes and specific factors does collagen synthesis require?

Hydroxylation of proline and lysine, Vitamin C, $O_2$, and $Fe^{2+}$

What results from Vitamin C deficiency?

Impaired collagen maturation

What does impaired collagen maturation lead to?

Impaired connective tissue integrity

How do collagen fibers appear under H&E stain?

Acidophilic, Pink with eosin, and Thick bundles

What stain turns collagen fibers blue?

Mallory trichrome

What stain turns collagen fibers red?

Sirius red

What type of collagen composes reticular fibers?

Type III collagen

What fibers are thin, branching, and form an extensive network?

Reticular fibers

What fibers provide a supportive framework?

Reticular fibers

What are the major locations of reticular fibers?

Lymphoid tissues, Bone marrow, Liver, Endocrine glands, Around small blood vessels, and Around adipocytes, smooth muscle, and nerve fibers

What fibers are thinner than type I collagen fibers?

Elastic fibers

What mechanical property do elastic fibers allow?

Stretch and recoil

In what tissues are elastic fibers particularly important?

Tissues subject to repeated deformation

What are the major locations of elastic fibers?

Lungs, Large blood vessels, and Elastic lamellae of arteries

What protein forms the microfibril scaffold in the structure of elastic fibers?

Fibrillin

What is deposited on the microfibril scaffold to form an elastic fiber?

Elastin

What structure is formed after elastin deposition on the microfibril scaffold?

Elastic fiber

How do elastic fibers appear under H&E stain?

Poorly stained and Less acidophilic than collagen

What special stains are used for elastic fibers?

Orcein and Aldehyde fuchsin

What is the main protein in collagen fibers?

Collagen I

What is the main protein in reticular fibers?

Collagen III

What is the main protein in elastic fibers?

Elastin

What is the physical appearance of collagen fibers?

Thick bundles

What is the physical appearance of reticular fibers?

Thin network

What is the physical appearance of elastic fibers?

Thin branching fibers

What is the main function of collagen fibers?

Tensile strength

What is the main function of reticular fibers?

Support

What is the main function of elastic fibers?

Stretch & recoil

What color do collagen fibers appear in H&E?

Pink

What is the appearance of reticular fibers under H&E?

Poorly visible

What is the appearance of elastic fibers under H&E?

Poorly visible

What is the highly hydrated component of the extracellular matrix called?

Ground substance

What does ground substance contain?

Glycosaminoglycans (GAGs), Proteoglycans, Multiadhesive glycoproteins, and Water

What are the functions of ground substance?

Fills spaces between cells and fibers, Allows diffusion of small molecules, Provides lubrication, Acts as a barrier to penetration, and Influences cellular activities

What are long polymers of repeating disaccharides called?

Glycosaminoglycans