Connective Tissue Proper
Connective tissue proper
Two subcategories of connective tissue proper:
Loose connective tissue
Dense connective tissue
Three basic components of connective tissue proper :
Cells
- Usually scattered throughout the tissue.
Extracellular matrix
- Suspends cells, comprises:
- Protein fibers, which provide strength and support for the tissue
- Ground substance, which is the non-living protein and carbohydrate molecules suspended in water
Loose connective tissue.
- Most widespread and most diverse type of connective tissue.
- Gel-like ground substance
- Spindle-shaped fibroblast cells, which synthesize the ground substance and protein fibers
- Mast cells
- Large macrophages
- Some white blood cells, all of which are granular
- Fibers: thick collagenous, thin elastic, branching reticular
- Areolar tissue is very loosely organized, so that cells and fibers are scattered and spaces are visible under the microscope; in fact, "areolar" means "small space"
- Present in various locations in the body where it supports organs and vasculature and participates in the inflammatory response.
Be aware that many texts use the terms "areolar" and "loose connective tissue" interchangeably.
Adipose:
- Under the microscope, adipocytes look like bubbles; clusters of round circles bumping up against each other, with nuclei pushed to the edges.
- In life, each cell holds a single fat droplet; the fat is not present in the slide preparation, but we can still see the space it occupied.
- Relatively little extracellular matrix.
- Adipose tissue cushions the organs, insulates the body, and stores energy.
- Comprises an abundance of reticular fibers that form complicated branching and interweaving patterns.
- Reticular fibers are attached to reticular cells; these are specialized fibroblasts that synthesize and hold the fibers.
- Lymphocytes; other types of white blood cells are also typically present.
- Reticular tissue forms a mesh-like network of support, aka, stroma, for blood cells within the lymph nodes, spleen, liver, and bone marrow.
Dense connective tissue proper:
- Characterized by abundant fibers, with relatively little extracellular matrix.
- Comprises bundles of tightly packed collagen fibers that run in parallel waves.
- Fibroblasts lie between the collagen fibers.
- The wavy organization of collagen fibers allow for a limited amount of stretch in a single direction.
- Present in tendons, which hold muscle to bone; ligaments, which hold bone to bone; and, fascia, which wraps and binds structures throughout the body.
- Comprises irregularly arranged collagen fibers and fibroblasts
- Can withstand tension from many directions, and is found in the fibrous capsules of joints, in the dermis of the skin, and in the submucosa of the digestive tract.
- Comprises closely packed elastic fibers that run in parallel; in preparatory slides, its ground substance often appears dark pink.
- Abundance of elastic fibers facilitates recoil after stretching.
- It is found in some ligaments of the vertebral column, and in the walls of large arteries and bronchial tubes.
Clinical correlation:
Marfan Syndrome is an inherited disease of the connective tissues; it's multi-organ system deficits underlies the widespread importance of connective tissues. Patients with Marfan's syndrome have numerous ailments from ocular lens dislocation to structural abnormalities of the heart valves and blood vessels, and joint abnormalities, and even disproportionately long bones.