Pre-Lab Reading Introduction Connective tissue is a term used to describe the tissue of mesodermal origin that that forms a matrix beneath the epithelial layer and is a connecting or supporting framework for most of the organs of the body. This lab will focus on the so-called connective tissue proper and cartilage; the next lab will focus on bone.
The intrinsic cascade which has less in vivo significance in normal physiological circumstances than the extrinsic cascade is initiated when contact is made between blood and exposed negatively charged surfaces.
The extrinsic pathway is initiated upon vascular injury which leads to exposure of tissue factor, TF also identified as factor IIIa subendothelial cell-surface glycoprotein that binds phospholipid. The green dotted arrow represents a point of cross-over between the extrinsic and intrinsic pathways.
The two pathways converge at the activation of factor X to Xa. Active factor Xa hydrolyzes and activates prothrombin to thrombin. Factor XIIIa also termed transglutaminase cross-links fibrin polymers solidifying the clot. The kinins are released from both high molecular weight kininogen HMWK and low molecular weight kininogen LMWK as a result of activation of either tissue kallikrein or plasma kallikrein.
The kallekreins themselves exist in inactive pre-forms. The kinins are involved in many physiological and pathological processes including regulation of blood pressure and flow via modulation of the renin-angiotensin pathwayblood coagulation, cellular proliferation and growth, angiogenesis, apoptosisand inflammation.
Kinin action on endothelial cells leads to vasodilation, increased vascular permeability, release of tissue plasminogen activator tPAproduction of nitric oxide NOand the mobilization of arachidonic acid, primarily resulting in prostacyclin PGI2 production by endothelial cells.
Although the activities of the kallikrein-kinin system are involved in numerous processes, this section will deal only with their function in blood coagulation. With respect to hemostasis the most important kinin is bradykinin which is released from HMWK.
The two forms of prekallikrein, plasma and tissue, are derived from distinct genes on different chromosomes. The plasma kallikrein gene symbol KLKB1 is on chromosome 4q34—q35 and the tissue kallikrein gene symbol KLK1 located on chromosome 19q When plasma prekallikrein is activated to kallikrein it cleaves HMWK in a two-step process that ultimately releases bradykinin.
Bradykinin is a 9-amino acid vasoactive peptide that induces vasodilation and increases vascular permeability. Activated tissue kallikrein cleaves lysyl-bradykinin also called kallidin from LMWK. Lysyl-bradykinin is bradykinin with a lysine residue at the N-terminus making it a amino acid vasoactive peptide.
Its activities are essentially identical to those of bradykinin. Exons 1 to 9 encode the heavy chain of both kininogens. Exon 10 encodes bradykinin as well as the light chain of HMWK. Exon 11 encodes the light chain of LMWK. The heavy and light chain nomenclature refers to the disulfide-bonded structure of each kininogen after their activation, which results from kallikrein cleavage.
The protein circulates in the plasma as single-chain polypeptide with a molecular weight of 88— kDa dependent upon the level of glycosylation.
The heavy chain is 64 kDa and contains domains 1, 2, and 3 whereas the light chain is 45—56 kDa and comprises domains 5 and 6.
The heavy and light chains are linked together through domain 4 which also contains the bradykinin sequence. Domain 1 contains a low affinity calcium-binding site.
Domain 3 also has platelet and endothelial cell-binding activity. Domain 5 has sequences for heparin binding, cell-binding sites, and antiangiogenic properties. The binding of HMWK to negatively charged surfaces occurs through a histidine region of the light chain which is in domain 5.
Domain 6 contains the prekallikrein and factor XI-binding sites. By being able to bind to charged surfaces via domain 5 and simultaneously bind factor XI and prekallikrein via domain 6, HMWK can serve as the cofactor in contact activation of plasma.
Factor XII, prekallikrein, and HMWK saturably and reversibly bind to endothelial cells, platelets, and granulocytes in a zinc-dependent reaction. When plasma makes contact with a negatively charged surface factor XII binds and is autoactivated to factor XIIa the "a" signifies the activated factor.Oct 27, · The most familiar type of epithelial tissue is made up of a special type of epithelial cell and is called the epidermis, or the skin.
The epidermis protects other body tissues from damage from a hostile or dangerous environment and provides a protective barrier against many parasites and . The function of the Epithelial tissue can be:: a, for cover the body surfaces, forms the inner lining of body cavity, and also lines the hollow organs.
b. for regeneration c ells.
c, for physical protection from abrasion, dehydration and destruction from chemical and biological substances. Epithelial Tissue Function Epithelial tissue covers the outside of the body and lines organs, vessels (blood and lymph), and cavities.
Epithelial cells form the thin layer of cells known as the endothelium, which is contiguous with the inner tissue lining of organs such as the brain, lungs, skin, and heart. Plant Cells, Tissues, and Tissue Systems.
Plants, like animals, have a division of labor between their different cells, tissues, and tissue systems. Epithelium Study Guide. Epithelial tissue comprises one of the four basic tissue srmvision.com others are connective tissue (support cells, immune cells, blood cells), muscle tissue (contractile cells), and nervous srmvision.com represent various combinations of these four basic tissue types, which thus comprise the entire body.
The image shown in cross section plan simple epithelium stained with hematoxylin-eosin. This epithelium is characterized by being formed by a row of flat cells.
You can clearly distinguish the nuclei of each cell, as well as the boundaries between them. Just below the cells are clearly differentiated basal membrane, which is a support structure of the .