Untitled Quiz

Connective Tissue Overview

• Connective tissue binds, supports, and strengthens other tissues.
• It protects and insulates internal organs.
• It compartmentalizes structures like skeletal muscle.
• It's the body's major transport system.
• It stores energy reserves.
• It's the primary site of immune responses.

General Features of Connective Tissue

• Composed of cells and matrix.
• Matrix is the material between widely spaced cells, consisting of protein fibers and ground substance.
• Ground substance is the material between the cells and fibers, secreted by the cells, and determines tissue qualities.
• Connective tissue doesn't occur on free surfaces.
• It has a nerve supply (except in cartilage and tendons).
• It's highly vascular (except in cartilage and tendons).

Connective Tissue Cells

• Fibroblasts: large, flat cells with branching processes that migrate throughout connective tissue and secrete ground substance and fibers.
• Macrophages: develop from white blood cells; surround and engulf material via phagocytosis.
• Mast cells: alongside blood vessels that supply connective tissue; produce histamine (a chemical that dilates blood vessels).
• Adipocytes ("fat cells"): store triglycerides.

Connective Tissue Matrix - Ground Substance

• Ground substance is a component of connective tissue that is between cells and fibers.
• It supports cells, binds them together, and provides a medium for substance exchange.
• Hyaluronic acid is an example of ground substance.

Connective Tissue Matrix - Fibers

• Collagen fibers strengthen and support connective tissue.
• They're strong, resist pulling forces, and are flexible.
• Collagen is the most abundant protein in the body.
• Elastic fibers are smaller in diameter than collagen fibers, branching to form networks.
• They're made of the protein elastin.
• Reticular fibers provide support to the walls of blood vessels.
• They are made of collagen with a glycoprotein covering.

Connective Tissue Types

• There are six types of connective tissue.
• Each type differs in their fiber, ground substance, and cell composition.
• Each type has very specific structure and function.

Loose Connective Tissue

• Fibers are loosely intertwined among many cells.
• 3 types:
  • Areolar: one of the most widely distributed connective tissues; contains fibroblasts, macrophages, plasma cells, mast cells, adipocytes, various fiber types, and forms the subcutaneous layer.
  • Adipose: cells (adipocytes) specialized to store triglycerides.
  • Reticular: made of interlacing reticular fibers and reticular cells that connect to form a network; used to bind smooth muscle cells and filter worn-out blood cells and bacteria.

Dense Connective Tissue

• Contains more, thicker, and denser fibers but fewer cells than loose connective tissue.
• 3 types:
  • Dense Regular: bundles of collagen fibers arranged regularly, parallel, giving strong structure, withstands pulling at ends, but unravels when pulled from the side
  • Dense Irregular: collagen fibers packed closely together in an irregular, random pattern, found where pulling forces are exerted in various directions.
  • Elastic: contains branching elastic fibers and fibroblasts; yellowish in color; strong; can regain shape after stretching; found in lungs and arteries.

Cartilage

• Dense network of collagen and elastic fibers embedded in chondroitin sulfate (a rubbery component).
• Can withstand more stress than dense or loose connective tissue.
• Collagen fibers make the tissue strong, while chondroitin sulfate makes it resilient.
• Cartilage cells (chondrocytes) are located in lacunae (holes in the matrix).
• Perichondrium: dense irregular connective tissue surrounding cartilage (but cartilage is avascular and lacks nerve supply).
• 3 types: hyaline, fibrocartilage, elastic.

Bone Tissue (Osseous Tissue)

• 2 types: compact and spongy.
• Compact:
  • Osteon: basic unit of compact bone.
  • Lamellae: concentric circles of matrix.
  • Lacunae: spaces in the matrix that house cells (osteocytes).
• Spongy:
  • Trabeculae: columns of bone with spaces filled with red bone marrow.

Blood Tissue

• Connective tissue with a fluid matrix (plasma).
• Contains red blood cells (erythrocytes) to transport oxygen, white blood cells (leukocytes) with various immune functions, and platelets to participate in blood clotting.