<< Chapter < Page Chapter >> Page >
Connective Tissue Examples
Connective tissue proper Supportive connective tissue Fluid connective tissue
Loose connective tissue
  • Areolar
  • Adipose
  • Reticular
Cartilage
  • Hyaline
  • Fibrocartilage
  • Elastic
Blood
Dense connective tissue
  • Regular elastic
  • Irregular elastic
Bones
  • Compact bone
  • Cancellous bone
Lymph

Connective tissue proper

Fibroblasts are present in all connective tissue proper ( [link] ). Fibroblasts and adipocytes are fixed cells, which means they remain within the connective tissue. Other cells, such as mast cells move in and out of the connective tissue in response to chemical signals.

Connective tissue proper

The left image shows a diagram of connective tissue. As a whole, the connective tissue appears somewhat disorganized, with fibers and cells mixed together heterogeneously. There are many open spaces between the embedded elements, suggesting that the connective tissue is somewhat loosely packed. The thickest fibers are collagen fibers; the thinner fibers are elastic fibers. Both the collagen fibers and the elastic fibers crisscross randomly throughout the tissue. In addition, a net of reticular fibers appear in the upper part of the diagram. Two yellow and oval shaped adipocytes are embedded below the reticular fiber net, with a small dark nucleus squeezed into one corner of the cell. A mesenchymal cell is next to one of the adipocytes. The cell is rectangular and has four projections stemming from each corner of the cell. The projections appear to attach to the nearby collagen fibers. A fibroblast is located at the center of the diagram. The fibroblast appears similar to the mesenchymal cell, except that it is larger and has more projections. Finally, a white macrophage is in the lower right of the diagram. The macrophage is a white, oval shaped disc with a prominent nucleus. The right diagram is a micrograph of connective tissue. The tissue is mostly stained pink, however, the thick collagen fibers crisscrossing the tissue are white. Five adipocytes also appear white, except for their cell membrane and nucleus, which stained dark. A mesenchymal cell occupies the space between two adipocytes. It stains a very deep purple, but its shape is unclear in the micrograph. A fibrocyte is also visible as an oval shaped cell with a deep purple nucleus.
Fibroblasts produce this fibrous tissue. Connective tissue proper includes the fixed cells fibrocytes, adipocytes, and mesenchymal cells. LM × 400. (Micrograph provided by the Regents of University of Michigan Medical School © 2012)

Cell types

The most abundant cell in connective tissue proper is the fibroblast    .Proteoglycans and proteins secreted by fibroblasts combine with extra-cellular fluids to produce a viscous ground substance that, with embedded fibrous proteins, forms the extra-cellular matrix. As you might expect, a fibrocyte    , a less active form of fibroblast, is the second most common cell type in connective tissue proper.

Connective tissue fibers and ground substance

Three main types of fibers are secreted by fibroblasts: collagen fibers, elastic fibers, and reticular fibers. Collagen fibers , while flexible, have great tensile strength, resist stretching, and give ligaments and tendons their characteristic resilience and strength. These fibers hold connective tissues together, even during the movement of the body.

Elastic fiber contains the protein elastin. The main property of elastic fibers are that after being stretched or compressed, it will return to its original shape. Elastic fibers are prominent in elastic tissues found in skin and the elastic ligaments of the vertebral column and the outer ear.

Reticular fiber is also formed from the same protein subunits as collagen fibers; however, these fibers form a branching network. They are found throughout the body, but are most abundant in the reticular tissue of soft organs, such as liver and spleen, where they anchor and provide structural support

Loose connective tissue

Loose connective tissue is found between many organs where it acts both to absorb shock and bind tissues together. It allows water, salts, and various nutrients to diffuse through to adjacent or imbedded cells and tissues.

Adipose tissue consists mostly of fat storage cells, with little extracellular matrix ( [link] ). White fat contributes mostly to lipid storage and can serve as insulation from cold temperatures and mechanical injuries. Adipose tissue can be found protecting the kidneys and cushioning the back of the eye. It is also found directly beneath the skin.

Adipose tissue

Image A shows a collection of yellow adipocytes that do not have a consistent shape or size, however, most have the general appearance of a kernel of corn with a wide end that tapers to a point. Each adipocyte has a nucleus occupying a small area on one side of the cell. Nothing else is visible within the cells. Image B shows a micrograph of adipose tissue. Here, the adipocytes are stained purple. However, only their edges and their nuclei stain, giving the adipose tissue a honeycomb appearance. The adipocytes in the micrograph are large and round, but still show a diversity of shapes and sizes. The nucleus appears as a dark staining area very close to the cell membrane.
This is a loose connective tissue that consists of fat cells with little extracellular matrix. It stores fat for energy and provides insulation. LM × 800. (Micrograph provided by the Regents of University of Michigan Medical School © 2012)

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, Histology. OpenStax CNX. Feb 27, 2015 Download for free at http://legacy.cnx.org/content/col11764/1.1
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Histology' conversation and receive update notifications?

Ask