They originate in the mesodermal germ layer and differentiate from mesenchyme and hematopoietic tissue in the bone marrow. Fibroblasts are the most abundant and secrete many protein fibers, adipocytes specialize in fat storage, hematopoietic cells from the bone marrow give rise to all the blood cells, chondrocytes form cartilage, and osteocytes form bone.
The extracellular matrix contains fluid, proteins, polysaccharide derivatives, and, in the case of bone, mineral crystals.
Protein fibers fall into three major groups: collagen fibers that are thick, strong, flexible, and resist stretch; reticular fibers that are thin and form a supportive mesh; and elastin fibers that are thin and elastic.
The major types of connective tissue are connective tissue proper, supportive tissue, and fluid tissue. Loose connective tissue proper includes adipose tissue, areolar tissue, and reticular tissue.
These serve to hold organs and other tissues in place and, in the case of adipose tissue, isolate and store energy reserves. The matrix is the most abundant feature for loose tissue although adipose tissue does not have much extracellular matrix. Dense connective tissue proper is richer in fibers and may be regular, with fibers oriented in parallel as in ligaments and tendons, or irregular, with fibers oriented in several directions. Organ capsules collagenous type and walls of arteries elastic type contain dense irregular connective tissue.
Cartilage and bone are supportive tissue. Cartilage contains chondrocytes and is somewhat flexible. Hyaline cartilage is smooth and clear, covers joints, and is found in the growing portion of bones.
Fibrocartilage is tough because of extra collagen fibers and forms, among other things, the intervertebral discs. Elastic cartilage can stretch and recoil to its original shape because of its high content of elastic fibers. The matrix contains very few blood vessels.
Bones are made of a rigid, mineralized matrix containing calcium salts, crystals, and osteocytes lodged in lacunae. Bone tissue is highly vascularized. Cancellous bone is spongy and less solid than compact bone. Fluid tissue, for example blood and lymph, is characterized by a liquid matrix and no supporting fibers. Under the microscope, a tissue specimen shows cells located in spaces scattered in a transparent background.
Ligaments connect bones together and withstand a lot of stress. What type of connective tissue should you expect ligaments to contain? One of the main functions of connective tissue is to integrate organs and organ systems in the body. Discuss how blood fulfills this role.
Blood is a fluid connective tissue, a variety of specialized cells that circulate in a watery fluid containing salts, nutrients, and dissolved proteins in a liquid extracellular matrix. Blood contains formed elements derived from bone marrow. Erythrocytes, or red blood cells, transport the gases oxygen and carbon dioxide. Leukocytes, or white blood cells, are responsible for the defense of the organism against potentially harmful microorganisms or molecules. Some cells have the ability to cross the endothelial layer that lines vessels and enter adjacent tissues.
Nutrients, salts, and waste are dissolved in the liquid matrix and transported through the body. Why does an injury to cartilage, especially hyaline cartilage, heal much more slowly than a bone fracture? A layer of dense irregular connective tissue covers cartilage. No blood vessels supply cartilage tissue. Injuries to cartilage heal very slowly because cells and nutrients needed for repair diffuse slowly to the injury site. Skip to content The Tissue Level of Organization.
Learning Objectives By the end of this section, you will be able to: Identify and distinguish between the types of connective tissue: proper, supportive, and fluid Explain the functions of connective tissues. Functions of Connective Tissues Connective tissues perform many functions in the body, but most importantly, they support and connect other tissues; from the connective tissue sheath that surrounds muscle cells, to the tendons that attach muscles to bones, and to the skeleton that supports the positions of the body.
Embryonic Connective Tissue All connective tissues derive from the mesodermal layer of the embryo see Figure.
Classification of Connective Tissues The three broad categories of connective tissue are classified according to the characteristics of their ground substance and the types of fibers found within the matrix Figure. Connective Tissue Proper Fibroblasts are present in all connective tissue proper Figure.
Connective Tissue Proper. Fibroblasts produce this fibrous tissue. Connective tissue proper includes the fixed cells fibrocytes, adipocytes, and mesenchymal cells. Connective Tissue Fibers and Ground Substance Three main types of fibers are secreted by fibroblasts: collagen fibers, elastic fibers, and reticular fibers.
Loose Connective Tissue Loose connective tissue is found between many organs where it acts both to absorb shock and bind tissues together. Adipose Tissue. This is a loose connective tissue that consists of fat cells with little extracellular matrix.
It stores fat for energy and provides insulation. This is a loose connective tissue made up of a network of reticular fibers that provides a supportive framework for soft organs. Dense Connective Tissue. Disorders of the…. Supportive Connective Tissues Two major forms of supportive connective tissue, cartilage and bone, allow the body to maintain its posture and protect internal organs.
Cartilage The distinctive appearance of cartilage is due to polysaccharides called chondroitin sulfates, which bind with ground substance proteins to form proteoglycans. Types of Cartilage. Cartilage is a connective tissue consisting of collagenous fibers embedded in a firm matrix of chondroitin sulfates.
The example is from dog tissue. Fluid Connective Tissue Blood and lymph are fluid connective tissues. Blood: A Fluid Connective Tissue.
Blood is a fluid connective tissue containing erythrocytes and various types of leukocytes that circulate in a liquid extracellular matrix. Chapter Review Connective tissue is a heterogeneous tissue with many cell shapes and tissue architecture. The main tissue type in the heart is cardiac muscle. Note from Sarah Bellham: Please be aware that there is connective tissue in the heart. The blood in the heart, for example, is composed of connective tissue. The pericardium is also composed of connective tissue.
However, the primary tissue composing the heart is cardiac muscle. Which one of these cells is not a cell type routinely found in loose connective tissue? Fibroblast b. Microglia c. Histiocyte d. Plasma cell e. Mast cell. Fibroblasts, histiocytes, plasma cells, and mast cells are routinely seen in loose connective tissue.
Fibroblasts produce collagen. The fibroblast also produces the ground substance in connective tissue. The histiocyte is a tissue macrophage. Plasma cells are derived from B lymphocytes. Mast cells secrete histamine. Which connective tissue cell is a tissue macrophage? Myofibroblast c. Myofibroblasts contain properties of both fibroblasts and smooth muscle cells. The histiocyte is a connective tissue macrophage.
Which of the following can be classified as "specialized connective tissue"? Cartilage b. Connective tissue provides support, binds together, and protects tissues and organs of the body. Connective tissue consists of three main components: cells , protein fibers , and an amorphous ground substance. Together the fibers and ground substance make up the extracellular matrix.
Whereas the other tissue types epithelium, muscle, and nervous tissue are largely made up of cells, the extracellular matrix is the major component of most connective tissue. This chapter will focus on the basic types of connective tissue, while subsequent chapters examine the specialized connective tissues cartilage , bone , and blood. Connective tissue is classified based on the characteristics of its cellular and extracellular components. The main criteria are the type of cells, arrangement and type of fibers, and composition of the extracellular matrix.
Loose areolar connective tissue has a sparse, irregular network of collagen and elastic fibers suspended within a relatively large amount of ground substance. Dense regular connective tissue is composed of type I collagen fibers oriented in the same direction. It provides tensile strength in one direction. Dense irregular connective tissue contains type I collagen fibers woven in multiple directions. It provides tensile strength in multiple directions. Forgot Username? About MyAccess If your institution subscribes to this resource, and you don't have a MyAccess Profile, please contact your library's reference desk for information on how to gain access to this resource from off-campus.
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