Connective Tissues Overview

Connective Tissues

• Connective tissues are found throughout the body, supporting and cushioning organs.
• They're positioned beneath all epithelial layers and act as 'packing material' between organs.
• Special connective tissues include cartilage, bone, and blood.
• Cartilage offers flexibility and resistance to compression, providing structural support.
• Bone offers structural and mechanical support.
• Blood is a specialized microenvironment, a fluid tissue.

Ordinary Connective Tissues

• Loose connective tissue is prevalent beneath epithelial layers, acting as a reservoir for cells.
• Dense irregular connective tissue is robust, withstanding tearing and distributing mechanical forces.
• Dense regular connective tissue, forms tendons and ligaments, providing biomechanical function.
• Adipose tissue, or fat tissue, stores energy and insulates.

Stroma and Metastasis

• Stroma refers to the connective tissue component of organs.
• Metastasis involves the spread of cancer cells from a primary site to a new location, within the connective tissue.

Special Connective Tissues

• Cartilage exhibits flexibility and resists compression, offering structural and mechanical support.
• Bone's role is in structural and mechanical support, and a specific specialized microenvironment.
• Blood and its components comprise a specialized microenvironment for stem cells.

General Features

• Connective tissues are widespread throughout the body.
• They lie beneath epithelial layers.
• They function as 'packing materials' between organs, known as fascia.
• Tissues incorporate tendons, aponeuroses, ligaments, joint capsules, and organ capsules.
• They form sheaths around muscles and nerves, as well as internal membranes like the pleura and peritoneum.

CT Functions

• Connective tissues provide structural support, cushioning, force transmission (e.g., tendons, ligaments), and energy storage (adipose tissue).
• They're reservoirs for immune cells (loose connective tissue).
• Connective tissues generate specific microenvironments (stroma)
• They are essential for wound repair and healing.
• They play a role in development (embryonic mesenchyme).

CT Composition

• Connective tissues contain water, ground substance (glycosaminoglycans, proteoglycans, and glycoproteins), extracellular fibers, and cells typically capable of movement.

Extracellular Fibres

• Connective tissues comprise different fiber types, including collagen, elastic, and reticular fibers.
• Collagen fibers are stiff and provide structural support.
• Elastic fibers are flexible and elastic.
• Reticular fibers form a delicate meshwork, providing a scaffold for cells.

Extracellular Fibres and Aging

• Elastic fibers are less able to regenerate as we age.
• Collagen fibers' type and structure change with age as well.

Keloids and Adhesions

• Keloids involve exaggerated scar tissue deposition.
• Adhesions refer to the post-operative formation of scar tissue that unites or fuses anatomical structures.

Fibroblast

• Fibroblasts are the primary cell type in connective tissue.
• They are mobile and secrete connective tissue components.
• They play a crucial role in wound healing.

Adipocytes

• Adipocytes are typically clustered as a tissue mass in specific locations.
• They consist of a single, large fat droplet, highly attenuated cytoplasm, and a displaced nucleus.
• Adipose tissue is sexually dimorphic (differing between sexes) and plays a role as an active endocrine organ.
• Adipose tissue demonstrates poor vascularization.

Macrophage

• Macrophages originate from circulating monocytes.
• They are essential scavenger cells, and play a critical role in connective tissue turnover.
• They participate significantly in wound healing and inflammation.

Mast Cells

• Mast cells are present in relatively low numbers in connective tissue.
• They are involved in inflammation.
• They release histamine and bradykinin to promote inflammation in response to stimulus.
• Are crucial in allergic responses

Lymphocytes

• Lymphocytes (B and T cells) are connective tissue components, including those found in lymphoid organs and beneath epithelia.
• B lymphocytes produce antibodies, while T lymphocytes carry out various important and diverse immunological functions.
• Lymphocytes constantly migrate in and out of connective tissues, frequently increasing in number at sites of infection.

Granulocytes

• The granulocyte subgroup includes neutrophils, basophils, and eosinophils.
• Neutrophils are the most prevalent granulocyte type.
• Basophils and mast cells are associated with allergic responses and inflammation.
• Eosinophils typically manifest in parasitic infections, allergies, and wound healing situations.