Ordinary Connective Tissue (Anatomy)

Question 1

Describe the main cell types present in loose areolar connective tissue

Answer 1

• Fibroblasts - produce the fibres and ground substance that form the matrix.
• Macrophages - phagocytic cells that engulf and destroy bacteria, and dead or dying cells of our own body. Also activate the immune system when they detect foreign antigens.
• Leukocytes (WBCs) - neutrophils attack bacteria and lymphocytes react against bacteria, toxins and other foreign agents.
• Plasma cells - synthesise antibodies during an immune response.
• Mast cells - secrete herparin that inhibits blood clotting, and histamine that increases blood flow by dilating blood vessels.

Question 2

Describe the main fibre types present in ordinary connective tissue

Answer 2

Collagen

• Tough, flexible, and stretch-resistant.
• Type 1 = dermis, ligaments, tendons, and bone.
• Type 2 = hyaline and elastic cartilage.
• Type 3 (reticulin) = first collagen secreted in wound healing, lymphoid organs; stained for by silver salts.
• Type 4 = basal lamina
• Type 7 = forms anchoring fibrils e.g. anchors basal lamina of epidermis to underlying dermal fibres.

Reticular fibres

• Thin collagen type 3 fibres coated with glycoprotein.
• Individual fibres, do not form bundles.
• Support framework for the spleen and lymph nodes, and constitute part of the basement membranes underlying epithelia.

Elastic fibres

• Thinner than collagenous fibres.
• Branch and rejoin each other along their course.
• Made of elastin coated with the glycoprotein fibrillin.
• The coiled structure of elastin allows it to stretch and recoil.
• Abundant in the dermis, lungs, and aorta.

Question 3

Describe the ground substance materials present in ordinary connective tissue

Answer 3

Glycosaminoglycans

• Long, unbranched polysaccharide chains composed of repeating disaccharide units.
• Negatively charged and thus tend to attract sodium and potassium ions which causes the glycosaminoglycans to absorb and retain water.
• Chondroitin sulfate is abundant in blood vessels and bones and gives cartilage its relative stiffness.
• Hyaluronic acid forms a lubricant in the joints and constitutes much of the vitreous body in the eyeball.

Proteoglycans

• Glycosaminoglycans bound to a protein core.
• Form thick colloids which slow the spread of pathogenic organisms through the tissues.
• Some are embedded in cell plasma membranes, attached to the cytoskeleton on the inside and to Extracellular molecules in the matrix.
• Create a strong structural bond between cells and extracellular molecules.
• Help hold tissues together.

Adhesive glycoproteins

• Protein-carbohydrate complexes.
• Bind plasma membrane proteins to extracellular collagen and proteoglycans.
• Guide migrating cells to their destinations in a tissue.

Question 4

Describe the ultrastructure of a fibroblast

Answer 4

• Large, fusion cells with abundant and irregularly branched cytoplasm.
• Extensive RER and well developed Golgi.

Question 5

Describe the ultrastructure of a plasma cell

Answer 5

• Eccentric nucleus.

- Lots of RER in cytoplasm.

Question 6

Distinguish dense regular connective tissues, tendons and ligaments from loose areolar connective tissue

Answer 6

Dense regular

• Collagen fibres are closely packed and are parallel to each other (therefore resists stress).
• Fibres occupy more space than cells and ground substance.
• Found in tendons, ligaments and aponeuroses (flattened tendons on abdomen and back).
• Only cells it contains are fibroblasts.
• Offers resistance in one direction.

Areolar

• Loosely organised fibres.
• Abundant blood vessels.
• Abundant cells and ground substance.
• Found in almost every part of the body. Surrounds blood vessels and nerves, and nearly every epithelium rests on a layer of areolar tissue.

Question 7

Describe dense irregular connective tissue

Answer 7

• Thick bundles of collagen which run in random directions.
• Little room for cells and ground substance.
• Offers resistance and protection.
• Constitutes most of the dermis and forms a protective capsule around organs such as the kidneys and testes.

Question 8

Where are all connective tissue cells derived from

Answer 8

Mesenchymal cell from the mesoderm layer of the developing embryo.

Question 9

What molecule consists of a triple helix of three polypeptide chains

Answer 9

Tropocollagen

Question 10

What is the periodicity of the collagen fibril banding pattern

Answer 10

67nm

Question 11

What does the extracellular matrix consist of

Answer 11

Fibres and ground substance