BIOL 330 - Chapter 5 Connective Tissue

Liberty biol 330

What are the three structural components of connective tissue

Cells, fibers, and ground substance

Which components make up the majority of connective tissue

Fibers and ground substance

What are the four main functions of connective tissue

Maintain organ form; bind/connect tissues; support diffusion of nutrients/waste; store growth/differentiation factors in ECM

What nuclear features indicate active protein synthesis in connective tissue cells

Oval nuclei with prominent nucleoli and fine chromatin

Why do connective tissue cells have fine chromatin

Because they are actively synthesizing proteins (fibers and ground substance)

What is the embryologic origin of connective tissue

Mesoderm-derived mesenchyme

Which connective tissue cells originate from mesoderm

Fibroblasts

Which connective tissue cells originate from bone marrow

Adipocytes, macrophages, mast cells, plasma cells, leukocytes

Which connective tissue cells are resident (stay in tissue)

Fibroblasts, adipocytes, mast cells

Which connective tissue cells circulate before entering tissue

Plasma cells and leukocytes

Which connective tissue cells are transient and die by apoptosis

Macrophages and leukocytes

What defines embryonic mesenchyme

Undifferentiated connective tissue with elongated cells and abundant ground substance

What nuclear characteristics do mesenchymal cells have

Large euchromatic nuclei with prominent nucleoli

What is the main ECM component of mesenchyme

Hyaluronan-rich ground substance with little to no collagen

What does Masson trichrome stain indicate in mesenchyme

Collagen stains blue, showing mesenchyme lacks collagen

What is the difference between fibroblasts and fibrocytes

Fibroblasts are active ECM-producing cells; fibrocytes are inactive, smaller, and less metabolically active

What features identify an active fibroblast

Large ovoid nucleus, prominent nucleolus, abundant rough ER and Golgi

What features identify a fibrocyte

Smaller spindle shape, darker nucleus, less rough ER, acidophilic cytoplasm

When do fibroblasts undergo mitosis

Primarily during tissue repair

What do fibroblasts produce in connective tissue

Collagen, elastic fibers, reticular fibers, GAGs, proteoglycans, and glycoproteins

What is the function of collagen fibers

Provide tensile strength

What is the function of elastic fibers

Provide stretch and flexibility

What is the function of reticular fibers

Form structural framework and compartments

What are glycosaminoglycans (GAGs) and their function

Long polysaccharides that bind water and resist compressive forces

What are proteoglycans and their role

Protein + GAG complexes that act as the main filler of the ECM

What is the role of multiadhesive glycoproteins in ECM

Link cells to ECM and stabilize tissue structure

What are examples of multiadhesive glycoproteins

Fibronectin and laminin

What do fibronectin and laminin specifically do

Anchor epithelial cells to underlying connective tissue (basal lamina)

How do fibroblasts appear under H&E stain

Spindle-shaped with eosinophilic cytoplasm blending into collagen bundles

What happens to fibroblasts during wound healing

They proliferate and produce collagen to form scar tissue

What type of tissue replaces non-dividing tissues after injury

Scar tissue (e.g., in heart and nervous tissue)

What are myofibroblasts and their function

Modified fibroblasts that produce collagen and contract wounds

What protein allows myofibroblasts to contract

Alpha-smooth muscle actin

What happens to myofibroblasts after healing

They undergo apoptosis

What happens if myofibroblasts do not undergo apoptosis

Leads to fibrosis or keloid formation

What are the three stages of integument repair

Scab formation, granulation tissue, scar tissue

What is the primary function of adipocytes

Store fat or generate heat

How do macrophages form

Monocytes leave blood and differentiate into macrophages

What are the main functions of macrophages

Phagocytosis, immune defense, antigen processing

What are alternative names for macrophages in tissues

Langerhans (skin), Kupffer (liver), microglia (brain)

What organelles are abundant in macrophages

Lysosomes, rough ER, Golgi

What is the mononuclear phagocytic system

A system of long-lived cells that process and present antigens

What are the three main functions of the mononuclear phagocytic system

Antigen uptake, processing, and presentation

Where are dendritic cells found and what do they do

Lymph nodes/thymus; present antigens

What is the function of osteoclasts

Break down bone

How are multinuclear giant cells formed

Fusion of multiple macrophages

What are mast cells and where are they found

Large granulated cells in connective tissue, especially near blood vessels

What is unique about mast cell granules

They are metachromatic (change dye color)

What substances are stored in mast cell granules

Heparin, histamine, proteases, chemotactic factors, leukotrienes

What does histamine do in inflammation

Causes vasodilation and increases vascular permeability

What are the three main functions of mast cells

Inflammation, innate immunity, tissue repair

Where are mast cells most abundant

Respiratory mucosa and perivascular skin

What receptor is found on mast cells

High-affinity IgE receptor

What triggers mast cell degranulation

Cross-linking of IgE by antigen

What are the local effects of histamine release

Redness, warmth, swelling, itching

What is the flare and wheal reaction

Skin response caused by histamine release

What is edema and what causes it

Fluid accumulation due to increased permeability or pressure imbalance

What is the difference between transudate and exudate

Transudate = pressure imbalance; exudate = inflammation with protein leakage

What is mastocytosis

Excessive production of mast cells

What is immediate hypersensitivity

A rapid allergic reaction occurring within seconds to 30 minutes

What is anaphylaxis

A severe systemic allergic reaction after sensitization

What do plasma cells do

Produce antibodies

What is the appearance of a plasma cell nucleus

Clock-face chromatin pattern

How long do plasma cells live

10–20 days

Where is IgA found and what does it do

Mucosal surfaces; prevents pathogen colonization

What is the role of IgG

Provides most immunity and crosses placenta

What is the role of IgM

First antibody in early immune response

What is the role of IgE

Triggers allergic reactions and fights parasites

What are the two categories of leukocytes

Granulocytes and agranulocytes

What are the three granulocytes and their roles

Neutrophils (bacteria), eosinophils (parasites/allergies), basophils (histamine)

What are agranulocytes

Lymphocytes (T/B cells) and monocytes

What are the four steps of phagocytic mobilization

Leukocytosis, margination, diapedesis, chemotaxis

What percentage of body weight is collagen

~30%

What are the major collagen types and locations

Type I (bone/tendon), II (cartilage), III (stretch tissues), IV (basement membrane)

What is procollagen

Triple helix precursor of collagen

What amino acid is required every third position in collagen

Glycine

What gives collagen stability

Hydroxyproline and hydroxylysine

What is the banding pattern of collagen fibrils

67 nm periodicity

What happens to collagen during wound healing

Type III is replaced by Type I

What enzyme requires zinc in wound healing

Collagenase

What growth factors are important in healing

TGF-alpha, TGF-beta, PDGF, FGF, VEGF

What are causes of delayed wound healing

Infection, vitamin deficiencies, ischemia, malnutrition

What is dehiscence

Reopening of a wound

What is the difference between hypertrophic scar and keloid

Hypertrophic stays within wound; keloid extends beyond

What are reticular fibers made of

Type III collagen

Where are reticular fibers commonly found

Lymph nodes, spleen, bone marrow

What do elastic fibers allow

Stretch and recoil

What enzyme forms elastin cross-links

Lysyl oxidase

What causes Marfan syndrome

Mutation in fibrillin affecting elastic fibers

What are the components of ground substance

GAGs, proteoglycans, glycoproteins

What is the function of ground substance

Fills space, lubricates, and protects

What is the role of hyaluronidase

Breaks down GAGs and allows tissue spread (e.g., bacteria)

What are proteoglycans important for

Binding growth factors and regulating ECM

What drives fluid movement in connective tissue

Hydrostatic and osmotic pressure gradients

What are major causes of edema

Protein imbalance, venous obstruction, lymph blockage, inflammation

What are the three major types of connective tissue

Proper, supporting (bone/cartilage), fluid (blood/lymph)

What is loose connective tissue

Gel-like matrix with all fiber types; wraps and cushions organs

What is dense regular connective tissue

Parallel collagen fibers; found in tendons and ligaments

What is dense irregular connective tissue

Irregular collagen; found in dermis

What is adipose tissue function

Energy storage, insulation, protection