connective tissue overview

Introduction to Connective Tissue

• Connective tissues consist of cells and an extracellular matrix (ECM).

• The ECM fills spaces between cells, differing from other tissue types by being more substantial.

Functions of Connective Tissue

Connecting Tissues

• Connective tissues literally connect one tissue to another.

• Skin Example: The dermis connects the epidermis (stratified squamous epithelium) to underlying tissues.

• Thigh Example: Tendons connect skeletal muscle to pelvic bone, facilitating movement.

Support and Structure

• The skeleton, primarily made of bone connective tissue, provides physical support and an internal framework for the body.

Encasing Internal Organs

• Connective tissues, like capsules, enclose many internal organs (e.g., spleen).

  • Capsules provide outer walls and internal partitions.

  • E.g., the pituitary gland has a connective tissue capsule that separates different parts of the organ.

Protection of Organs

• Bone protects internal organs such as the brain, spinal cord, heart, and lungs.

• Bone Structure: Contains nuclei cells; stores red (blood cell production) and yellow (fat storage) bone marrow.

Adipose Tissue Functions

• Adipose tissue (fat) offers cushioning, energy storage, and insulation.

  • Cushioning: Protects organs from trauma.

  • Energy Storage: Stores excess energy for survival during famines.

  • Insulation: Helps maintain body temperature by trapping heat.

Transport of Substances

• Blood, a subtype of connective tissue, transports gases, nutrients, and waste products.

  • Composed of red blood cells (oxygen/CO2 transport), white blood cells (immune function), and a fluid matrix (plasma) that carries proteins and ions.

Cell Types in Connective Tissue

Basic Cell Types

• Blasts: Immature cells responsible for creating extracellular matrix.

• Cytes: Mature cells that maintain the health of the matrix (upkeep).

• Clasts: Cells that break down extracellular matrix, important for remodeling and repair.

  • Remodeling: Involves destroying old matrix parts to replace them with new ones.

  • Repair: Cleans debris after tissue damage (e.g., bone fractures).

Examples of Cell Names

• Osteoblast: Immature bone cell (creates bone matrix).

• Osteocyte: Mature bone cell (maintains bone matrix).

• Osteoclast: Cell that breaks down bone tissue (resorption).

Composition of Extracellular Matrix (ECM)

Major Ingredients

1. Protein Fibers

   • Collagen Fibers: Thick and strong, provide tensile strength.

   • Reticular Fibers: Thinner fibers forming networks within organs.

   • Elastic Fibers: Stretchy fibers allowing tissues to recoil (e.g., in the ear).

2. Ground Substance

   • Comprises water, minerals, and dissolved substances. Acts as a filler between cells and fibers.

   • Varies in consistency in different connective tissues (e.g., fluid in blood vs. mineral-rich in bone).

Specific Molecules in Ground Substance

• Hyaluronic Acid: Lubricates tissues and reduces friction (important in joints).

• Proteoglycans: Trap water, act as biological springs, and absorb physical stress.

  • Found in high-stress areas like the knee joints for shock absorption.

Conclusion

• Understanding connective tissue structure helps predict its functionality in various body parts.

• Recognizing the roles of different cells and matrix constituents underpins the physiological significance of connective tissues.