In other tissues, stretching in several directions is achieved by alternating layers where fibers run in the same orientation in each layer, and it is the layers themselves that are stacked at an angle. The dermis of the skin is an example of dense irregular connective tissue rich in collagen fibers. Dense irregular elastic tissues give arterial walls the strength and the ability to regain original shape after stretching Figure 4.
The distinctive appearance of cartilage is due to the presence of polysaccharides called chondroitin sulfates, which bind with ground substance proteins to form proteoglycans. A layer of dense irregular connective tissue, the perichondrium, encapsulates the cartilage. Cartilaginous tissue is avascular, thus all nutrients need to diffuse through the matrix to reach the chondrocytes.
This is a factor contributing to the very slow healing of cartilaginous tissues. The three main types of cartilage tissue are hyaline cartilage, fibrocartilage, and elastic cartilage Figure 4. Hyaline cartilage , the most common type of cartilage in the body, consists of short and dispersed collagen fibers and contains large amounts of proteoglycans.
Under the microscope, tissue samples appear clear. The surface of hyaline cartilage is smooth. Both strong and flexible, it is found in the rib cage and nose and covers bones where they meet to form moveable joints. It makes up a template of the embryonic skeleton before bone formation.
A plate of hyaline cartilage at the ends of bone allows continued growth until adulthood. Fibrocartilage is tough because it has thick bundles of collagen fibers dispersed through its matrix. The knee and jaw joints and the the intervertebral discs are examples of fibrocartilage. Elastic cartilage contains elastic fibers as well as collagen and proteoglycans. This tissue gives rigid support as well as elasticity.
Tug gently at your ear lobes, and notice that the lobes return to their initial shape. The external ear contains elastic cartilage.
Bone is the hardest connective tissue. It provides protection to internal organs and supports the body. Both components of the matrix, organic and inorganic, contribute to the unusual properties of bone.
Without collagen, bones would be brittle and shatter easily. Without mineral crystals, bones would flex and provide little support. Osteocytes , bone cells, are located within lacunae. The histology of transverse tissue from long bone shows a typical arrangement of osteocytes in concentric circles around a central canal Figure 4.
Bone is a highly vascularized tissue. Unlike cartilage, bone tissue can recover from injuries in a relatively short time. Cancellous bone looks like a sponge under the microscope and contains empty spaces between trabeculae, or arches of bone proper.
It is lighter than compact bone and found in the interior of some bones and at the end of long bones. Compact bone is solid and has greater structural strength. Blood is a fluid connective tissues. Blood has two components: cells and fluid matrix Figure 4. Erythrocytes, red blood cells, transport oxygen and some carbon dioxide. Leukocytes, white blood cells, are responsible for defending against potentially harmful microorganisms or molecules.
This degranulation process is protective when foreign organisms invade the body, but is also the cause of many allergic reactions. White fat cells are specialized for the storage of triglyceride, and occur singly or in small groups scattered throughout the loose connective tissue. They are especially common along smaller blood vessels.
When fat cells have accumulated in such abundance that they crowd out or replace cellular and fibrous elements, the accumulation is termed adipose tissue.
These cells can grow up to microns and usually contain once centrally located vacuole of lipid - the cytoplasm forms a circular ring around this vacuole, and the nucleus is compressed and displaced to the side.
The function of white fat is to serve as an energy source and thermal insulator. Brown fat cells are highly specialized for temperature regulation. These cells are abundant in newborns and hibernating mammals, but are rare in adults.
They have numerous, smaller lipid droplets and a large number of mitochondria, whose cytochromes impart the brown color of the tissue. The electron transport chain of these mitochondria is disrupted by an uncoupling protein, which causes the dissipation of the mitochondrial hydrogen ion gradient without ATP production. This generates heat. Cartilage is a specialized form of connective tissue produced by differentiated fibroblast-like cells called chondrocytes.
It is characterized by a prominent extracellular matrix consisting of various proportions of connective tissue fibers embedded in a gel-like matrix. Chondrocytes are located within lacunae in the matrix that they have built around themselves. Individual lacunae may contain multiple cells deriving from a common progenitor.
Lacunae are separated from one another as a result of the secretory activity of the chondrocytes. A highly fibrous, organized, dense connective tissue capsule known as the perichondrium surrounds cartilage. The fibroblast-like cells of this layer have chondrogenic potentiality, and are responsible for the enlargement of cartilage plates by appositional growth. Appositional growth involves cell division, differentiation, and secretion of new extracellular matrix, thereby contributing mass and new cells at the cartilage surface.
It is in contrast to interstitial growth, in which new matrix is deposited within mature cartilage. Three kinds of cartilage are classified according to the abundance of certain fibers and the characteristics of their matrix:. Pre-Lab Quiz Review the four primary types of collagen and where they are typically found. Type 2 - Cartilage. Type 3 - Reticular Fibers. Type 4 - Basement Membrane. Answer: White adipose tissue is composed of large cells with prominent central vacuoles.
It is white because the lipid is washed away during fixation and the vacuoles appear white under the microscope. Brown adipose tissue has smaller cells with many lipid droplets and mitochondria. It is brown because of the large number of cytochromes present. Answer: Hyaline cartilage — type II collagen — nose, tracheal rings, end of ribs. Fibrocartilage - type I collagen - tendons, intervertebral discs. Elastic cartilage - type II collagen - ear and epiglottis. Compact bone is solid and has greater structural strength.
Blood and lymph are fluid connective tissues. Cells circulate in a liquid extracellular matrix. The formed elements circulating in blood are all derived from hematopoietic stem cells located in bone marrow Figure. Erythrocytes, red blood cells, transport oxygen and some carbon dioxide. Leukocytes, white blood cells, are responsible for defending against potentially harmful microorganisms or molecules. Platelets are cell fragments involved in blood clotting.
Some white blood cells have the ability to cross the endothelial layer that lines blood vessels and enter adjacent tissues. Nutrients, salts, and wastes are dissolved in the liquid matrix and transported through the body. Lymph contains a liquid matrix and white blood cells.
Lymphatic capillaries are extremely permeable, allowing larger molecules and excess fluid from interstitial spaces to enter the lymphatic vessels.
Lymph drains into blood vessels, delivering molecules to the blood that could not otherwise directly enter the bloodstream. In this way, specialized lymphatic capillaries transport absorbed fats away from the intestine and deliver these molecules to the blood.
View the University of Michigan Webscope to explore the tissue sample in greater detail. Visit this link to test your connective tissue knowledge with this question quiz.
Can you name the 10 tissue types shown in the histology slides? Connective tissue is a heterogeneous tissue with many cell shapes and tissue architecture. Structurally, all connective tissues contain cells that are embedded in an extracellular matrix stabilized by proteins.
The chemical nature and physical layout of the extracellular matrix and proteins vary enormously among tissues, reflecting the variety of functions that connective tissue fulfills in the body. Connective tissues separate and cushion organs, protecting them from shifting or traumatic injury.
Connect tissues provide support and assist movement, store and transport energy molecules, protect against infections, and contribute to temperature homeostasis. Many different cells contribute to the formation of connective tissues. 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.
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