The amount and structure of each component correlates with the function of the tissue, from the rigid ground substance in bones supporting the body to the inclusion of specialized cells; for example, a phagocytic cell that engulfs pathogens and also rids tissue of cellular debris.
The most common cell found within connective tissue is the fibroblast. Polysaccharides 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. Three main types of fibers are secreted by fibroblasts: collagen fibers, elastic fibers, and reticular fibers.
Collagen fiber is made from fibrous protein subunits linked together to form a long and straight fiber. 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 along with lesser amounts of other proteins and glycoproteins. The main property of elastin is 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. Reticular fiber is also formed from the same protein subunits as collagen fibers; however, these fibers remain narrow and are arrayed in 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 to the parenchyma the functional cells, blood vessels, and nerves of the organ. All of these fiber types are embedded in ground substance. Secreted by fibroblasts, ground substance is made of water, polysaccharides, specifically hyaluronic acid, and proteins.
These combine to form a proteoglycan with a protein core and polysaccharide branches. The proteoglycan attracts and traps available moisture forming the clear, viscous, colorless matrix you now know as ground substance. 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.
Protection is another major function of connective tissue, in the form of fibrous capsules and bones that protect delicate organs and, of course, the skeletal system. Specialized cells in connective tissue defend the body from microorganisms that enter the body. Transport of fluid, nutrients, waste, and chemical messengers is ensured by specialized fluid connective tissues, such as blood and lymph.
Adipose cells store surplus energy in the form of fat and contribute to the thermal insulation of the body. 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 called a dipocytes that store lipids as droplets that fill most of the cytoplasm figure 4.
A large number of capillaries allow rapid storage and mobilization of lipid molecules. Fat contributes mostly to lipid storage, can serve as insulation from cold temperatures and mechanical injuries, and can be found protecting internal organs such as the kidneys and eye.
Areolar tissue shows little specialization. It is an atypical connective tissue since it does not bind, connect, or network with any body cells. It is made up of blood cells and is surrounded by a nonliving fluid called plasma. Privacy Policy. Skip to main content. Organization at the Tissue Level. Search for:. Connective Tissue.
Learning Objectives Describe the main characteristics and functions of connective tissue. Key Takeaways Key Points Connective tissue is the most abundant and widely distributed of the primary tissues. Connective tissue has three main components: cells, fibers, and ground substance. Connective tissue is classified into two subtypes: soft and specialized connective tissue. Major functions of connective tissue include: 1 binding and supporting, 2 protecting, 3 insulating, 4 storing reserve fuel, and 5 transporting substances within the body.
Connective tissues can have various levels of vascularity. Cartilage is avascular, while dense connective tissue is poorly vascularized. Others, such as bone, are richly supplied with blood vessels. Key Terms extracellular matrix : Cells of the connective tissue are suspended in a non-cellular matrix that provides structural and biochemical support to the surrounding cells.
Types of Connective Tissue Connective tissues encompass a diverse array of tissue types that are involved in binding and supporting body structure and tissues. Learning Objectives Describe the diverse types of connective tissue. Key Takeaways Key Points The lymphatic system is a part of the circulatory system, comprising a network of conduits called lymphatic vessels that carry a clear fluid called lymph unidirectionally towards the heart.
Blood is considered a specialized form of connective tissue. In vertebrates, it is composed of blood cells suspended in a liquid called blood plasma. The primary tissue of bone, osseous tissue, is a relatively hard and lightweight composite material, formed mostly of calcium phosphate in the chemical arrangement termed calcium hydroxylapatite. In dense regular connective tissue, the fibers are arranged in parallel bundles whereas those in dense irregular connective tissue are not.
The circulatory system is key to the transport of vital biomolecules and nutrients throughout the body. Learn about the different components and functions of the human circulatory system dealt with in detail in this tutorial.
The lymphatic system is also elucidated elaborately here Read More. It is impact resistant. Look at this image and make sure you can recognise loose and dense connective tissue. This is an example of dense regular connective tissue. Can you identify the cells fibroblasts and collagen fibres? Notice how the fibres are all aligned. In this type of tissue, the collagen fibres are densely packed, and arranged in parallel.
This type of tissue is found in ligaments which link bone to bone at joints and tendons connections between bones or cartilage and muscle. These are powerfully resistant to axially loaded tension forces, but allow some stretch.
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