Block 3 Flashcards
What is the difference(s) between a desmosome and a hemidesmosome?
Desmosomes connect epithelia on the lateral membrane. Hemidesmosomes connect epithelia to the ECM.
Why is a zonula occludens referred to as a “tight junction”?
Only water and a small amount of solutes can pass though
Describe the components of ground substance and how they contribute to ECM function.
Gylcosaminoglycans is a porous, hydrated, gel serves as a cushion to absorb and disperse compressive loads. Includes hyaluronic acid and proteoglycans.
Fibers of the extracellular matrix provide tensile strength and elasticity. Includes collagen and elastin.
Adhesive glycoproteins link the cell to the
extracellular matrix by binding to integrins located in the cell membrane. Includes laminin and fibronectin.
Basement membrane is a sheet-like network of ECM proteins which acts as an interface between the epithelia and the underlying or surrounding connective tissue.
How do fibroblasts contribute to the structure and function of connective tissue?
Fibroblasts are responsible for the synthesis of almost all of the extracellular matrix of connective tissue.
Describe the composition, function, and location of each connective tissue type.
Mesenchymal connective tissue is present only in the embryo.
Loose (areolar) connective tissue is composed of a loose arrangement of fibers and dispersed cells (primarily fibroblasts, macrophages, mast cells and some white blood cells) imbedded in a gel-like ground substance. It is widely found under the epithelia of the body, packaging organs and surrounding capillaries. Loose connective tissue functions to wrap and cushion organs and hold tissues together. The macrophages of the loose connective tissue phagocytose bacteria.
Irregular dense connective tissue is composed primarily of irregularly arranged collagen fibers and contains few cells. It is able to withstand tension exerted in multiple directions, and provides structural strength. It is located in the reticular layer of the dermis of the skin, submucosa of the digestive tract, and fibrous capsules of visceral organs and joints.
Regular dense connective tissue is composed primarily of coarse collagen bundles densely packed and oriented into parallel cylinders or sheets that resist tensile forces. It can withstand great tensile strength when pulling force is applied in one direction. Located in tendons, most ligaments, and aponeurosis, they function to attach muscles to bones or muscle, and bones to bones.
Reticular Connective Tissue consists of a network of reticular fibers (composed from collagen type III) in loose ground substance. It functions to support the parenchyma of organs.
