1. PREPARED BY HUGH POTTER, Ph.D BIOLOGY DEPARTMENT UNION COUNTY COLLEGE The Connective Tissues

2. The connective tissues bind, protect and support the body. All connective tissues have three characteristics in common: 1. Cells such as fibrocytes, chondrocytes and osteocytes. 2. Three principal types of fiber found in connective tissues. A. Collagen - abundant in tendons and bones. B. Elastic fiber - found in the walls of arteries and in flexible cartilage like the epiglottis. C. Reticular fiber is the support material of soft organs like the spleen and liver. 3. Ground substance, a complex mixture of organic and inorganic materials, fills the spaces between the cells and fibers. Connective Tissue - Introduction

3. Mesenchyme Mesenchyme is the first connective tissue to appear in the embryo. All other connective tissues arise from mesenchyme by a process known as differentiation. The image to the right shows a very early fetal stage. The asterisk labels a region filled with mesenchyme. *

4. Mesenchyme cells appear to have fine projections and are separated from one another by a ground substance that contains delicate protein fibers. Many adult connective tissues such as bone and cartilage contain remnants of mesenchyme which permit repair and growth of the adult tissues.

5. Liquid Connective Tissue – The Blood LOOSE CONNECTIVE TISSUES 1. ADIPOSE 2. AREOLAR DENSE CONNECTIVE TISSUES 1. DENSE FIBROUS TISSUE - TENDON 2. SUPPORT CONNECTIVE TISSUES A. CARTILAGE B. BONE Connective Tissues -Types

6. Blood Blood is considered to be a fluid connective tissue. It consists of formed elements or cells and a liquid ground substance called plasma. The cells are primarily erythrocytes (RBC’s) and leukocytes (WBC’s). Fibers are only found in the blood during the process of clotting.

7. ADIPOSE TISSUE Adipose tissue is a loose connective tissue. It is located throughout the body. It is especially common in the subcutaneous region beneath the dermis where it provides insulation against heat loss. Fatty tissue also stores nutrients and vitamins

8. The adipocytes, the cells of adipose tissue account for most of the volume of fatty tissue. Adipose cells are very active metabolically. When we fast, the cells deflate like spent balloons as the oil stored in the center of the cell is broken down for energy. The adipocytes remain intact and can refill with lipid with an increase in nutrient uptake. Sub dermal Adipose Tissue

9. AREOLAR CONNECTIVE TISSUE Areolar connective tissue is the most abundant connective tissue is the body. It is commonly found in the papillary region of the dermis of skin and in the lamina propria of mucous membranes.

10. Areolar conntective tissue contains a very fluid ground substance. It also has a high concentration of elastic fibers which allow this tissue to return to its original shape following pressue or pinching. Areolar tissue contains almost all of the cell types found in any connective tissue. Mesenchymal cells, fibroblasts, macrophage, adipocytes, melanocytes and leukocytes are found in areolar tissue.

11. TENDON Tendon is a dense fibrous tissue in which the fibers are oriented in parallel. The fibers are predominantly collagen and organized as primary tendon bundles grouped together as fascicles. Blood vessels and nerves do not enter the fascicle. Tendons are designed to withstand great tension

12. Perichondrium Cartilage Cartilage is set apart from its surrounding tissues by a dense covering layer called the perichondrium. The perichondrium is divided into two layers, the fibrous portion and the inner cellular layer. New cartilage cells called chondrocytes arise from the cellular layer. These young cells produce the gel-like ground substance of cartilage which is rich in a polysaccharide derivative called chondroitin sulfate.

13. Chondrocytes occupy small chambers in the matrix of cartilage called lacunae. Cartilage is avascular. This lack of blood vessels is due to the production of a compound by the chondrocytes called anti-angiogenic factor (AAF). This substance inhibits the growth of blood vessels into cartilage. AAF is being tested as an anti-cancer drug. lacunae

14. HYALINE CARTILAGE Hyaline Cartilage contains fiber in its outer layer, the perichondrium. Chondroblasts arise from the perichondrium. As the cartilage ages, the cells appear in clusters of 2, 4 or 8. The matrix consists primarily of chondroitin sulfate. Hyaline cartilage can be found at the articular ends of long bones, as well as the trachea, bronchi and larynx.

15. FIBROCARTILAGE The matrix of fibrocartilage shows a preponderance of coarse collagenous fibers arranged in bundles. Cartilage cells are arranged between collagenous bundles often in rows. This cartilage lacks a perichondrium. It is found in the intervertebral disks, pubic symphysis and the lining of tendon grooves. Fibrocartilage is always found merging with neighboring hyaline cartilage or fibrous tissue.

16. ELASTIC CARTILAGE Elastic cartilage is very similar to hyaline cartilage except that it contains abundant elastic fiber in the matrix. Unstained, it has a yellow color due to the elastic fiber. It is located in the auricle or external ear and the eustacian tube. In the larynx, elastic cartilage forms the epiglottis, the corniculate, cuneiform and the arytenoid cartilages.

17. COMPACT BONE Compact bone is a dense connective tissue. The Haversian systems can be seen in this view. Osteocytes are arranged in concentric rings around the central Haversian canal. Fine, thread-like canaliculi can be seen. Compact bone is found around the shafts or diaphyses of long bones

18. COMPACT BONE-Haversian canals Compact bone consists of bone matrix laid down in concentric layers called lamellae. The lamellae surround a central Haversian canal(Hc) which contains blood vessels, nerves and lymphatics. Very delicate thread-like lines can be seen connecting the black osteocytes (oc)with the Haversian canal. Haversian Canals oc

19. Hc In this view of a Haversian system, the fine thread-like canaliculi can be seen connecting the osteocytes (oc) with the Haversian canal (Hc) oc