Connective tissue 1 Flashcards
connective tissue is composed of ?
- fibroblasts
- extracellular matrix
- ground substance
describe mesenchyme cells
consists of a population of undifferentiated cells, generally elongated but with many shapes, having large euchromatic nuclei and prominent nucleoli that indicate high levels of synthetic activity.
________ -______ are surrounded by an ECM that they produced and that consists largely of a simple ground substance rich in hyaluronan (hyaluronic acid), but with very little collagen
mesenchymal cells
connective tissue cell types include:
- fibroblasts
- macrophages
- mast cells
- plasma cells
- adipocytes
- leukocytes
what are fibroblasts?
typically have large active nuclei and eosinophilic cytoplasm that tapers off in both directions along the axis of the nucleus, a morphology often referred to as “spindle-shaped
what is the difference between inactive and active fibroblasts?
Active fibroblasts have large, euchromatic nuclei and basophilic cytoplasm, while inactive fibroblasts (or fibrocytes) are smaller with more heterochromatic nuclei
what is myofibroblasts contractile?
Fibroblasts involved in wound healing call myofibroblasts
Contractile. Pull edges of wound together by contraction like smooth muscle. After role completed, under apoptosis.
what are mast cells?
- components of loose connective tissues, often located near small blood vessels
- They are typically oval shaped, with cytoplasm filled with strongly basophilic granules
mast cell secretion is triggered by ____ ______ to certain antigens and allergens
re exposure
plasma cells are large ovoid cells with _________ cytoplasm
basophilic
plasma cells are often more abundant in ________ tissues
infected
Plasma cells leave their sites of origin in lymphoid tissues, move to connective -tissue, and produce antibodies that mediate immunity ( T or F)
TRUE
what are the 3 fibre types?
- collagen fibres
- Reticular fibres
- Elastic fibres
describe type I collagen
the most abundant collagen, assemble to form extremely strong fibrils, which are then bundled together further by other collagens into much larger structures called collagen fibers.
describe collagen I synthesis
Hydroxylation and glycosylation of procollagen α chains and their assembly into triple helices occur in the RER, and further assembly into fibrils occurs in the ECM after secretion of procollagen
describe collagen I assembly
- Rodlike triple-helix collagen molecules, each 300 nm long, self-assemble in a highly organized, lengthwise arrangement of overlapping regions.
- The regular, overlapping arrangement of subunits continues as large collagen fibrils are assembled.
- This structure causes fibrils to have characteristic cross striations with alternating dark and light bands when observed in the EM.
- Fibrils assemble further and are linked together in larger collagen fibers visible by light microscopy.
- Type I fibers often form into still larger aggregates bundled and linked together by other collagens.
what is the function of reticular fibres?
These fibers serve as a supportive stroma in most lymphoid and hematopoietic organs and many endocrine glands. The fibers consist of type III collagen that is heavily glycosylated
Can HE stain be used on elastic fibres?
NO
the major componant of elastic fibres is ?
elastin polypeptides
Most of the cross-links between elastin subunits consist of covalent, cyclic structure called ___________ each of which involves four converted lysines in two elastin molecules
desmosine
what are the 3 classes of ECM ground substance?
- glycosaminoglycans (GAG)
- Proteoglycans
- Multiadhesive glycoproteins
describe glycoproteins
usually globular proteins with branched oligosaccharide side-chains. Their polypeptide content is generally greater than their polysaccharide content.
describe proteoglycans
contain a core of protein with one or many side chains of sulfated GAGs as well as branched oligosaccharides, generally having more carbohydrate than do glycoproteins
_______ is concentrated in the basil lamina of the stratified epithelium and in the external laminae surrounding cross-sectioned nerves and muscle fibers
laminin
A fine network of _______ is localized more diffusely throughout the ECM
fibronectin
how does fluid move in connective tissue?
Water normally passes through capillary walls into the ECM of surrounding connective tissues primarily at the arterial end of a capillary, because the hydrostatic pressure is greater than the colloid osmotic pressure
hydrostatic pressure decreases toward the venous end of the capillary ( T or F)
TRUE
The fall in hydrostatic pressure parallels a decrease in osmotic pressure of the capillary blood because the plasma protein concentration increases as water is pushed out across the capillary wall. (FALSE)
FALSE (increase)
what are the types of connective tissue?
- loose
- dense (regular or irregular)
- reticular
- Cartilage
- Bone
________ _______ of type III collagen are produced and enveloped by the reticular cells, forming an elaborate network through which interstitial fluid or lymph and wandering cells from blood pass continuously
reticular fibres
what is the function of connective tissue?
support and connect
Connective tissue is composed primarily of extracellular material rather than cells (T or F)
TRUE
ECM is composed of _______ and ______
ground substance and fibres
