Connective Tissue. Distinguish the connective tissues from all epithelial tissues on the basis of location, cell density and the presence of discrete fibers.
Distinguish between loose irregular areolar , dense irregular, or dense regular connective tissues on the basis of fiber packing and orientation. Identify, at the light and electron microscopic levels, collagen, reticular, and elastic fibers. Identify and list the cell types found in the various kinds of general connective tissues, and describe their origins and functions.
The common fiber types include collagen, elastic, and reticular. Slide 43 Thick Skin, Sole of the Foot. They tend to have a wavy appearance and may be sectioned obliquely, transversely or longitudinally. Nuclei of fibroblasts fibrocytes are numerous among the collagen fibers. Slide 92 Thick Skin, Monkey Finger. Again note the wavy collagen fibers of the dermis in this slide of thick skin. Slide 47 Submaxillary Gland, Verhoeff's Hematoxylin.
Elastic fibers stain black with Verhoeff's Hematoxylin and are seen as branching black lines. In this slide, the elastic fibers are clearly visible around ducts and vessels collagen fibers are green. Both elastic and collagen fibers and various connective tissue cells are visible in this preparation.
Verhoeff's Hematoxylin stains elastic fibers black and Van Gieson stains collagen acidophilic. In your slide the acidophilic collagen fibers may not be obvious. Mast cells are easily identified due to the metachromasia of granules with toluidine blue.
Collagen protein fibers are thick. Elastic protein fibers are thin. Reticular protein fibers are thin but form a web-like arrangement.
If there is abundant space between protein fibers, the tissue is likely one of the loose connective tissues. If there is little space between protein fibers, the tissue is likely one of the dense connective tissues. Adipose is mainly large adipocyte cells containing a large droplet of lipids and nucleus and cytoplasm crammed into one corner of the cell.
There are more adipocytes than extracellular material in adipose. The protein fibers in regular dense connective tissue proper will largely parallel each other, but they are often undulate in a wave-like arrangement while being parallel.
Source: Stomach wall. Follow the checklist in Lab exercise 5. Areolar Tissue. This is a loose connective tissue widely spread throughout the body.
It contains all three types of fibers collagen, elastin, and reticular with much ground substance and fibroblasts. Reticular tissue is a mesh-like, supportive framework for soft organs such as lymphatic tissue, the spleen, and the liver Figure 4. Reticular cells produce the reticular fibers that form the network onto which other cells attach. Dense connective tissue contains more collagen fibers than does loose connective tissue.
As a consequence, it displays greater resistance to stretching. There are three major categories of dense connective tissue: regular, irregular, and elastic. Dense regular connective tissue fibers are parallel to each other, enhancing tensile strength and resistance to stretching in the direction of the fiber orientations.
Ligaments and tendons are made of dense regular connective tissue. In dense irregular connective tissue, the direction of fibers is random. This arrangement gives the tissue greater strength in all directions and less strength in one particular direction. In some tissues, fibers crisscross and form a mesh. 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.
Elastic fibers are long, thin fibers that form branching network in the extracellular matrix. They help the connective tissue to stretch and recoil.
Reticular fibers are short, fine collagenous fibers that can branch extensively to form a delicate network. Learning Objectives Describe the main characteristics and functions of connective tissue. 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.
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