Connective Tissue – General/Blood Flashcards
General characteristics of connective tissues
Few cells, large amounts of extracellular matrix, provides structural support, stores metabolites, defense/protection of the body (immunity, inflammatory, allergic reactions), repairs other tissues
Collagen characteristics
Most abundant protein in the body; flexible/tensile strength; produced by fibroblasts
Collagen type I
Can form collagen bundles; found in [dermis, tendons, ligaments, fascia, bone, most connective tissue]
Collagen type II
found in cartilage
Collagen type III
Assemble into reticular fibers
Collagen types IV
Sheet like mesh-work that is found in the basal lamina
Reticular fibers
Made of type III collagen, cross-link to form reticular tissue
Elastic fibers
Made of elastin and fibrillin, responds to stretch/distention
Elastin
hydrophobic domain, cross-linked by covalent bonds, fibers have variable lengths OR lamellar layers (like in blood vessels)
Fibrillin
Thin microfibrils that surrounds developing elastic fibers
Hyaluronic acids
Do not attach to protein cores to form proteoglycans, but will attach to existing proteoglycans to create a hydrophilic aggregate
Role of proteoglycans
Forms aggregates with hyaluronic acids to create a “gel” that resists compression without losing compressibility
Multiadhesive glycoproteins
Cross-links collagen, ECM, and cells; stabilizes/binds ECM to transmembrane integrins; BINDING SITES
2 types of multiadhesive glycoproteins
Fibronectin and Laminin
Fibronectin
Most abundant glycoprotein, contains binding sites for ECM molecules
Laminin
Present in the basal membrane, contains binding sites
Types of resident cells
Fibroblasts, Adipocytes, Macrophages, Mast Cells
Fibroblasts
Principle type of resident cell, produce components of the ECM, Types: active, inactive, myofibroblasts, mesenchymal
Active fibroblasts
Abundant cytoplasm/RER/Golgi and has euchromatic nucleoli, commonly in loose connective tissue
Inactive fibroblasts
Limited cytoplasm, heterochromatic, common in dense connective tissue
Myofibroblasts
Have the ability to contract, are commonly found in wound sites
Mesenchymal fibroblasts
present in embryonic connective tissue, give rise to many types of connective tissue
Adipocytes
Store energy as fat, produce hormones; Types: unilocular, multilocular
Unilocular adipocytes
Most common type, forms white adipose tissue, usually large lipid droplet with a flattened nucleus
Mulitlocular adipocytes
Rare in adults, multiple fat droplets and a large amount of mitochondria, generates heat, aka brown adipose tissue
Macrophages
Phagocytic cells derived from monocytes, have a kidney-shaped nucleus – functions: phagocytosis of bacteria/senescent cells/cell debris, presents antigens to immune cells, produces cytokines to active the immune system
Mast cells structure
Largest cells in connective tissue, oval w/ centrally placed nucleus, many big basophilic granules, surface contains IgE receptors
Mast Cell Functions
Mediates Inflammatory/hypersensitivity reactions: activates during first exposure to antigen, IgE activation causes degranulation of mast cells
Effects of histamines
Vasodilation, increase in vascular permeability, bronchoconstriction, increase in mucous production
Types of transient cells
Plasma cells, Leukocytes
Plasma cells
Antibody producing cells derived from B-lymphocytes, most numerous in areas of inflammation, have a “clock-face” pattern
Types of Leukocytes
aka WBCs, Lymphocytes, monocytes, neutrophils, eosinophils, basophils [Everyone’s Blood Needs More Leukocytes]
Lymphocytes
Round, dark heterochromatic
Produce antibodies/regulate immune response
Monocytes
Kidney shaped nucleus (is a macrophage when enters tissue), phagocytic cell
Neutrophils
phagocytes for bacteria
elongated, segmented, multi-lobed nucleus
Eosinophils
React to parasitic infections
Intense staining granules and bi-lobed nucleus
Basophils
Rare cells that are involved with allergic response
Bi-lobed nucleus and basophilic granules
Embryonic connective tissue
Mesenchyme and Mucous connective tissue
Mesenchyme tissue
Forms a 3D network, abundant in ground substance, but has few collagen/reticular fibers
Mucous connective tissue
Found only in umbilical cord (aka Wharton’s jelly)
large amounts of hyaluronic acid
Loose connective tissue
Highly cellular, thin/relatively sparse collagen type I fibers, abundant ground substance, large amounts of transient cells, acts as a filter tissue
Dense connective tissue
Lots of collagen type I fibers, little ground substance
Dense regular connective tissue
Densely packed collagen bundles, oriented in the same direction, have many inactive fibroblasts
Dense irregular connective tissue
Collagen bundles are in different directions, fibroblast are mostly inactive, resists stress in all direction
Specialized connective tissue
Adipose, reticular, cartilage, bone
Reticular tissue
loose connective tissue found in the stroma of organs
Has thin, branching, interconnected threads
