Connective Tissue Flashcards
Where is connective tissue located? What major functions do it serve? From what germ layer does it originate?
Forms matrix beneath the epithelial layer; (1) Acts as connecting/supporting framework for most of the organs of the body (2) Mediate exchange of nutrients and waste between circulation & other tissues; Mesoderm
What are two major ways that connective tissue differs from epithelia?
(1) Sparsely populated by cells (unlike keratinocytes in each layer of epithelium) (2) Extensive extracellular matrix of protein fibers, glycoproteins, & proteoglycans
What are the two principal components of connective tissue?
(1) Extracellular matrix (2) Support cells
What are the 3 distinguishing types of extracellular fibers in connective tissue?
(1) Collagenous fibers (2) Elastic fibers (3) Reticular fibers
Ground substance - What is it? How is it characterized? What is the significance of its characteristics?
Aqueous gel of glycoproteins and proteoglycans that occupies space between cellular and fibrillar elements of connective tissue; Gel-like viscous consistency & polyanionic; Determine permeability of connective tissue layer to solutes and proteins
Collagenous Fibers - Where are they present? What makes up collagenous fibers? What are the two types of collagenous connective tissue? What is the main difference between these types? Which type is most abundant?
All connective tissue; Collagen Type I, II, or III; (1) Loose (areolar) connective tissue (2) Dense connective tissue; Main difference = ratio of collagen fibers to ground substance; (1) Loose = occurs in small, elongated bundles separated by regions of ground substance (2) Dense = little ground substance; Loose
Collagenous Fibers - What is the difference between regular and irregular dense connective tissue? Give examples of each.
Regular = closely packed bundles of fibers located in one direction (e.g., tendons), Irregular = bundles oriented in multiple directions (e.g., dermis);
Reticular Fibers - What makes up reticular fibers? How do reticular fibers differ from collagenous fibers? Where are reticular fibers found?
Collagen Type III; Thin reticular network (not thick/coarse collagenous fibers); Supporting frameworks for Liver, lymphoid organs, capillary endothelia, and muscle fibers
Elastic Fibers - What makes up elastic fibers? How and where do they often organize? Where else are they found? What effect does stretching have on them?
Elastin (co-polymerizes with protein fibrillin); Lamellar sheets in walls of arteries; Dense, regular, elastic tissue in ligaments; Makes them take on an organized structure, since they are normally disorganized
Cells of the Connective Tissue Proper - Name and describe cells in connective tissue, including cell function at minimum.
(1) Fibroblasts - most common native cell, synthesizes collagen and ground substance of extracellular matrix (2) Chondrocytes - form extracellular matrix of cartilage (3) Osteocytes - form extracellular matrix of bone (4) Macrophages - connective tissue version of monocyte (i.e., phagocytic cells) (5) Mast cells - granulated immune cells, release histamine and enzyme in response to antigen recognition, protective but may also lead to allergies (6) White fat cells - storage of triglyceride, energy source, thermal insulator (7) Brown fat cells - temperature regulation, generate heat (Note: white & brown fat cells detailed in later flashcard)
Cells of the Connective Tissue Proper - What are myofibroblasts?
Fibroblasts with contractile function (rather than normal function of synthesizing collagen and ground substance of extracellular matrix)
Cells of the Connective Tissue Proper - What is another name for the reticuloendothelial system? In general, what does this system contain? Give specific examples.
Mononuclear phagocyte system; Tissue-specific, mobile, phagocytic cells that descend from monocytes (e.g., Kupffer cells of liver, alveolar macrophages of lung, microglia of CNS, and reticular cells of spleen)
Cells of the Connective Tissue Proper - How can one tell macrophages & fibroblasts apart?
Indistinguishable, except when marcophages internalize large amounts of visible tracer substances (e.g., dyes/carbon particles)
Cells of the Connective Tissue Proper - Describe white versus brown fat cells. What is each specialized for? Where is each found? What is the structure/organization of each? What is the main function of each?
WHITE - specialized for storage of triglyceride, occur singly or in small groups throughout loose connective tissue, common along smaller blood vessels, functions to serve as an energy source and thermal insulator; BROWN - highly specialized for temperature regulation, abundant in newborns and hibernating mammals but rare in adults, numeours, smaller lipid droplets & large number of mitochondria
Cells of the Connective Tissue Proper - What is adipose tissue? What is its typical cells’ sizes? What is typically a distinguishing characteristic of these cells?
Accumulation that results when fat cells crowd out or replace cellular/fibrous elements; Grow up to 100 microns; Centrally located vaculole of lipid (cytoplasm forms ring around it and nucleus compressed/displaced to side)
