Test 1 (topic 1 - Tissues & ECM) Flashcards
What are the 4 types of tissues?
nervous tissue, muscle tissue, epithelial tissue, connective tissue
Nervous tissue
Contains specialized cells which rapidly transmit electrical impulses
Muscle tissue
Long cells which are specialized for contraction and relaxation
Epithelial tissue
Layer(s) of closely packed cels forming coverings on internal and external surfaces
Connective tissue
In most cases, a loose arrangement of cells embedded within a support medium
Fxns of epithelial tissue (3)
1 - covering, lining, protecting exposed surfaces
2 - absorption (in gut)
3 - secretion
Notable characteristics of epithelium (6)
1 - cells are tightly packed together with little/no space in between
2 - tissue always has a ‘free surface’
3 - tissue is usually anchored to an underlying layer of connective tissue via a ‘basement membrane’
4 - tissue has no direct blood supply
5 - cells in lower layers are usually mitotic
6 - 2 types: membranous and glandular
basement membrane =
basal lamina (produced by the epithelial cells) + reticular lamina (produced by the connective tissue cells)
basal lamina =
lamina lucida + lamina densa
fxns of connective tissue (2)
1 - provides support, structure and protection
2 - binds strxs together
notable characteristics of connective tissue
1 - composed of cells and supporting ‘extracellular matrix’
2 - cells are usually spaced far apart, not in direct contact ich each other
3 - usually, is well vascularized
extracellular matrix (ECM)
Predominantly associated with connective tissue but not exclusive to it
ECM is composed of:
Fibers and ground substance
Name the different kinds of fibers in ECM
collagen fibers; reticular fibers; elastic fibers
collagen fibers
long fibers formed of the protein collagen
3 categories of collagen fibers
fibrillar collagens; netowork-forming collagens; linking/anchoring collagens
fibrillar collagens:
long “thick” strands which are often visible with a light microscope; the most abundant is formed of type I collagen, type II and III collagens also are placed in this category (think of them like ropes)
network-forming collagens:
an interlaced network of ultra-thin strands formed exclusively of type IV collagen; a major structural component of the lamina densa component of the basal lamina (form wheel like strx)
linking/anchoring collagens:
short strands which connect fibrillar collagens to each other and to other components within the extracellular matrix; e.g., type VII collagen, which anchors the reticular lamina to the basal lamina
reticular fibers:
very thin fibers formed predominantly of type III collagen
reticular fibers also: (3 additional things)
1 - form a flexible scaffolding within organs like the liver, spleen, lymph nodes, and red bone marrow
2 - main component of the reticular lamina of the basement membrane
3 - may be found scattered throughout the ground substance of loose connective tissue; is the predominant fiber type in reticular connective tissue
elastic fibers:
thin fibers formed primarily of the protein elastin
elastic fibers are the main type of ____________
main type of elastic connective tissue and elastic cartilage, but also found in loose connective tissue as well
what is vitamin C needed for?
Proper collagen formation; deficit leads to scurvy
ground substance
transparent mixture of macromolecules; widely varying in consistency
components of ground substance:
glycosaminoglycans (GAGs)
proteoglycans
glycoproteins
glycoasiminoglycans (GAGs):
long linear polysaccharides, all highly hydrophilic, highly viscous, and poly anion ich (therefore, capable of binding a large # of cations [primarily sodium])
GAG subtypes:
hyaluronic acid
Other GAGs, smaller and rich in sulfate “sulfated glycosaminoglycans”
Hyaluronic acid:
largest and most ubiquitous glycosaminoglycan
other GAGs, smaller and rich in sulfate “sulfated glycoasaminoglycans”
Smaller and rich in sulfate[= “sulfated glycosaminogycans”], bond covalently to proteins to form proteoglycans; predominant examples are dermatan sulfate, chondroitin sulfate, keratin sulfate, and heparin sulfate
proteoglycans:
large protein molecules consisting of numerous sulfated glycosaminoglycans bonded covalently to a large, rod-like core protein; e.g., aggrecan (down in cartilage) and syndecan (protein in cell)
glycoproteins:
large globular proteins covalently bonded to branched monosaccharide chains; e.g., fibronectin and laminin
Fxns of ECM (5 fxns, first 1)
1 - ground substance holds and supports fibers and cells
a) linkages btwn cell-surface protein molecules (integrity) and the GAGS &/or glycoproteins anchor the cell in place or guide it on its migration/movement through the ground substance
b) GAGs and glycoproteins in turn bind to the fibers, anchoring them and connecting them to the cells and to each other
c) laminins bind the underside of epithelial cells to the fibers making up the Saal lamina (found within the lamina lucida)
Fxns of ECM (5 fxns, 2-3)
2 - hydrophilic nature of GAGs allows for the absorption of a significant amount of water; this in turn, allows the tissues to resist compression and tension, protecting the cells and other strxs embedded within it (shock absorber
3 - viscous gel-like nature of ground substance acts to physically impede movement of invasive agents (bacteria)
a) viscous and slippery nature of hyaluronic acid makes it an excellent lubricant in joints
Fxns of ECM (5 fxns, 4-5)
4 - ground substance passes nutrients from the blood supply to the cells and passes waste material from the cells to the blood supply, via diffusion through the water bound to the GAGs
5 - facilitates and regulates communication btwn cells found within the ECM; some proteoglycans within the ECM bind and sequester signaling proteins (fibroblast growth factor)
Interstitial/extracellular fluid (tissue fluid):
fluid within connective tissue that is not bound up by the large molecules of the ground substance
Interstitial/extracellular fluid predominantly derived from:
blood plasma, via diffusion and filtration; therefore, similar to plasma in its chemical make-up (ions), except for blood proteins
a) much lower concentration of blood proteins because most proteins are too large to cross the vessel wall
Interstitial/extracellular fluid normally exists:
in very small quantities
