Connective Tissue Flashcards
CONNECTIVE TISSUE GENERAL TYPES
EMBRYONIC
ADULT
EMBRYONIC CONNECTIVE TISSUE types
Mesenchyme
Mucous tissue
ADULT CONNECTIVE TISSUE types
Ordinary/ Connective Tissue Proper
Specialized Connective Tissue
Ordinary/ Connective Tissue Proper types
Loose Connective Tissue
Dense Connective tissue (regular/ irregular)
Specialized Connective Tissue types
Cartilage
Bone
Blood
hematopoietic tissue`
COMPONENTS OF THE CONNECTIVE TISSUE
cells
fibers
ground substance
Major constituent of connective tissue is the
extracellular matrix (ECM)
made of: Protein fibers Ground substances
EXTRACELLULAR MATRIX (ECM) protein fibers
collagen, reticular, and elastic fibers
ECM Ground substance is a highly hydrophilic, viscous complex of
anionic macromolecules
Multiadhesive glycoproteins
anionic macromolecules in ecm
(glycosaminoglycans and proteoglycans)
Multiadhesive glycoproteins in ecm
(laminin, fibronectin, and others)
FUNCTIONS if connective tissue
SUPPORT AND PACKAGING
STORAGE
TRANSPORT
DEFENSE
REPAIR
SUPPORT AND PACKAGING example
Tendons, ligaments, areolar tissue
Bone and cartilage
STORAGE tissue examples
Lipids are stored in ADIPOSE TISSUE
LOOSE CONNECTIVE TISSUE stores water and electrolytes
serves as the medium through which nutrients and metabolic wastes are exchanged between cells and their nourishing blood supply
connective tissue matrix
DEFENSE EXAMPLE OF CONNECTIVE TISSUE
▪ Related to its content of phagocytic (macrophage) and antibody producing cells (plasma cells).
CELL TYPES
WANDERING OR MOBILE CELLS
FIXED CELLS
Permanent resident population
▪ Responsible for production and maintenance of extracellular components
▪ Storage for reserve fuel (fibroblasts, fat cells, undifferentiated mesenchymal cells, reticular cells)
FIXED CELLS
Transient emigrants from the bloodstream
▪ Concerned with the short term tissue reaction in injury
WANDERING OR MOBILE CELLS
WANDERING OR MOBILE CELLS EXAMPLES
(neutrophils, monocytes, lymphocytes, mast cells, plasma cells, macrophages)
Embryonic tissue where all types of connective tissues originate
MESENCHYME
Formed by elongated undifferentiated cells that are characterized by oval nuclei with prominent nucleoli and fine chromatin
MESENCHYME
______________ develops mainly from the middle layer of the embryo, the ________
MESENCHYME; mesoderm
Develops into other types of structures, such as blood cells, endothelial cells, and muscle cells.
MESENCHYME
CELLS OF CONNECTIVE TISSUE
Fibroblast
▪ Adipocytes
▪ Macrophages and the Mononuclear Phagocyte System
▪ Mast Cells
▪ Plasma Cells
▪ Leukocytes
Originate locally from undifferentiated mesenchymal cells and spend all their life in connective tissue
FIBROBLASTS
Synthesize collagen, elastin, glycosaminoglycans, proteoglycans and multiadhesive glycoproteins
FIBROBLASTS
are the most common cells in connective tissue
FIBROBLASTS
typically show large active nuclei and eosinophilic cytoplasm tapering off in both directions along the axis of the nucleus, a morphology usually called “spindle-shaped
FIBROBLASTS
Two stages of activity of fibroblasts
Active (fibroblast)
Quiescent (fibrocyte)
are large cells with large, euchromatic nuclei and basophilic cytoplasm (fibroblasts)
ACTIVE FIBROBLASTS
are smaller with less prominent, heterochromatic nuclei
INACTIVE FIBROBLAST or fibrocytes
Also known as fat cells
ADIPOCYTES
Connective tissue cells that have become specialized for storage of neutral fats or for the production of heat.
ADIPOCYTES
Connective tissue cells Incapable of mitotic division
ADIPOCYTES
ADIPOCYTES Can be stained with
osmic acid
ADIPOCYTES FUNCTIONS:
Storage of neutral fats or for the production of heat
key regulators of the body’s energy metabolism
Shock absorbers
As insulators
For protecting organs in the form of soft, elastic pad
For aesthetic purposes
TWO TYPES OF ADIPOSE TISSUE
White adipose tissue
Brown adipose tissue
the more common type
▪ composed of cells that, when completely developed, contain one large central droplet of whitish- yellow fat in their cytoplasm
White adipose tissue
▪ Contains cells with multiple lipid droplets interspersed among abundant mitochondria, which give these cells the darker appearance.
▪ has a much more limited distribution
Brown adipose tissue
o originate from hematopoietic stem cells in bone marrow
o are transient cells of most connective tissues
o also originate in the bone marrow and move to the connective tissue where they reside for a few days
o usually die by apoptosis
MAST CELLS, MACROPHAGES, AND PLASMA CELLS
were discovered and initially characterized by their phagocytic ability
Macrophages
Macrophages in EM are characterized by
an irregular surface with pleats, protrusions, and indentations
Generally have a well-developed Golgi apparatus, many lysosomes, and rough ER
MACROPHAGES AND THE MONONUCLEAR PHAGOCYTE SYSTEM FUNCTIONS:
o Important agents of defense
o Act as scavengers because of their mobility and phagocytic activity, engulfing extravasated blood cells, bacteria, foreign bodies and dead cells.
o Play a fundamental role in the development of immunity
Macrophages are Referred to as ________ once the phagocytosed particle, enclosed within the invaginated cell membrane.
phagosome
o macrophages that are stimulated
o change their morphological characteristics and metabolism
ACTIVATED MACROPHAGES
o has an increase in capacity for phagocytosis and intracellular digestion
o exhibit enhanced metabolic and lysosomal enzyme activity
ACTIVATED MACROPHAGES
Kupffer cells location and main function
Liver
Same as macrophages
Microglia cells cells location and main function
Nerve Tissue of the CNS
same as macrophages
Langerhans Cell cells location and main function
Skin
Antigen processing and presentation
Dentritic cells location and main function
Lymph nodes
Antigen processing and presentation
Osteoclast cells location and main function
Bone (fusion of several macrophages)
Digestion of bone
Multinuclear giant cells location and main function
Connective tissue (fusion of several macrophages)
Segregation and digestion of foreign bodies
Placenta macrophages
Hofbauer Cells
Adipose tissue macrophages
Adipose Macrophages
Are large, oval or round connective tissue cells, 20-30 m in diameter
Cytoplasm is filled with basophilic secretory granules.
Spherical nucleus is centrally situated and may be obscured by the cytoplasmic granules
MAST CELLS
displayed by mast cells because of high content of acidic radicals in their sulfated glycosaminoglycans
METACHROMASIA
which means that they can change the color of some basic dyes (eg, toluidine blue) from blue to purple or red.
METACHROMASIA
A PARTIAL LIST OF IMPORTANT MOLECULES RELEASED FROM TE GRANULES INCLUDES
Heparin
Histamine
Serine proteases
Eosinophil and neutrophil chemotactic factors
Leukotrienes C4, D4, and E4 (SRS-A)
a sulfated glycosaminoglycan that acts locally as an anticoagulant
Heparin
promotes increased vascular permeability and smooth muscle contraction
Histamine
activate various mediators of inflammation
Serine proteases
attracts those leukocytes
Eosinophil and neutrophil chemotactic factor
triggers smooth muscle contraction
Leukotrienes C4, D4, and E4 (SRS-A)
mast cells near small blood vessels in skin and mesenteries
PERIVASCULAR MAST CELLS
mucosa lining digestive and respiratory tracts
MUCOSAL MAST CELLS
TYPES OF MAST CELLS
PERIVASCULAR MAST CELLS
MUCOSAL MAST CELLS
are large, ovoid cells that have a basophilic cytoplasm due to their richness in rough ER
Plasma cells
Nucleus of the plasma cell is generally
spherical but eccentrically placed
Plasma cells There is alternating areas of compact, peripheral regions of heterochromatin and lighter areas of euchromatin, giving the nucleus a
clock-face appearance (Cartwheel Appearance)
Average lifespan of plasma cells
10-20 days.
migration of leukocytes from the blood vessels to the connective tissue
DIAPEDESIS-
classic signs involve redness and swelling with heat and pain (rubor et tumor cum calore et dolore).
Inflammation-
substances of various origin that induce some of the events characteristic of inflammation
o Chemotactic factors
chemical mediators of inflammation
Leukocytes do not return to the blood after arriving in connective tissue except for the
lymphocytes
is responsible for the migration of large quantities of specific cell types to regions of inflammation
CHEMOTAXIS-
happens under the influence of chemotactic factors
CHEMOTAXIS-
most abundant connective fibers
COLLAGEN
COLLAGEN Various types are present in the
skin, bone, cartilage, smooth muscle, and basal lamina.
TYPES OF COLLAGEN
- COLLAGEN THAT FORM FIBRILS
- FIBRIL-ASSOCIATED COLLAGENS
- COLLAGEN THAT FORMS ANCHORING FIBRILS
- COLLAGEN THAT FORMS NETWORK
Type I collagen is the most abundant and has a widespread distribution such as
tendons, organ capsules, and dermis.
COLLAGEN THAT FORM FIBRILS TYPE I REPRESENTATIVE TISSUES AND MAIN FUNCTION
skin, tendon, bone, dentin
resistance to tension
COLLAGEN THAT FORM FIBRILS TYPE II
REPRESENTATIVE TISSUES AND MAIN FUNCTION
cartilage, vitreous body
resistance to pressure
COLLAGEN THAT FORM FIBRILS TYPE III
REPRESENTATIVE TISSUES AND MAIN FUNCTION
skin, muscle, blood vessels, frequently together with type I
structural maintenance in expansible organ
COLLAGEN THAT FORM FIBRILS TYPE V
REPRESENTATIVE TISSUES AND MAIN FUNCTION
fetal tissues, skin, bone, placenta, most interstitial tissue
participates in type I collagen function
COLLAGEN THAT FORM FIBRILS TYPE XI
REPRESENTATIVE TISSUES AND MAIN FUNCTION
cartilage
participate in type II collagen functionn
short structures that bind the surfaces of collagen fibrils to one another and to other components of the ECM.
FIBRIL-ASSOCIATED COLLAGENS
FIBRIL-ASSOCIATED COLLAGENS Molecules are also known as FACIT collagens or
fibril-associated collagens with interrupted triple helices
they do not form fibril however they are associated to our collagen fibrils
FIBRIL-ASSOCIATED COLLAGENS
FIBRIL ASSOCIATED COLLAGEN TYPE IX
REPRESENTATIVE TISSUES AND MAIN FUNCTION
cartilage, vitreous body
bound glycosaminoglycans, associated with type II collagen
FIBRIL ASSOCIATED COLLAGEN TYPE XII
REPRESENTATIVE TISSUES AND MAIN FUNCTION
Embryonic tendon and skin
interacts with type I collagen
FIBRIL ASSOCIATED COLLAGEN TYPE XIV
REPRESENTATIVE TISSUES AND MAIN FUNCTION
Fetal skin and tendon
-
present in the anchoring fibrils that bind the basal lamina to reticular fibers in the underlying connective tissue
COLLAGEN THAT FORMS ANCHORING FIBRILS
COLLAGEN THAT FORMS ANCHORING FIBRILS TYPE VII REPRESENTATIVE TISSUES AND MAIN FUNCTION
epithelia
acnhors skin epidermal basal lamina to underlying stroma
molecules assemble in a meshwork that constitutes a major structural component of the basal lamina
COLLAGEN THAT FORMS NETWORK
refers to the production of the collagen
COLLAGEN SYNTHESIS-
collagens are produced by the
fibroblast
found in cartilage which also produce collagen
chondroblast-
cells found in the dental pulp
odontoblast
polypeptides initially formed on ribosomes of the rough ER
PROCOLLAGEN CHAINS
each procollagen molecule is composed of two
a1 and one a2 peptide chains, each with a molecular mass of approximately 100 kDa
present in all basement membranes, assembles as a lattice-like network in the basal lamina.
Collagen type IV,
COLLAGEN THAT FORMS ANCHORING FIBRILS TYPE IV
REPRESENTATIVE TISSUES AND MAIN FUNCTION
all basement membranes
support of delicate structures, filtration
order of collagen turnover rate from slowest to fastest
normal connective tissue
some organs, such as tendons and ligaments
periodontal ligament surrounding teeth
members of an enzyme class, matrix metalloproteinases or MMPs
COLLAGENASES
COLLAGENASES are members of an enzyme class
matrix metalloproteinases or MMPs
- specific enzymes initiating degradation of collagen
- Clip collagen molecules rendering them susceptible to further degradation by nonspecific proteases
COLLAGENASES
consist mainly of collagen type III, which forms extensive networks of extremely thin (diameters 0.5-2 m) and heavily glycosylated fibers in certain organs
RETICULAR FIBERS
RETICULAR FIBERS can be easily stained black by
impregnation with silver salts
RETICULAR fibers are particularly abundant in the framework of hematopoietic organs like
spleen, lymph nodes, red bone marrow
RETICULAR FIBERS constitute a network around the parenchymal cells of various organs like
liver, endocrine glands
Very flexible and have recoiling properties
o Are thinner than the average collagen
o Form sparse networks interspersed with collagen bundles in many organs subject to much bending or stretching, such as the wall of large arteries
ELASTIC FIBERS
Elastic fibers or________add the resiliency to connective tissue
lamellae (sheets)
ELASTIC FIBERS are usually demonstrated using ___________ which stains elastin a ___________
aldehyde fuscin
dark magenta.
are secreted by fibroblasts in connective tissue and by smooth muscle cells in the walls of blood vessels
elastin
Elastin molecules are_______ in shape with a molecular mass of
globular
70 kDa
are produced when covalent cross-links are formed among four lysine residues in different elastin molecules
DESMOSINE AND ISODESMOSINE
effectively cross-link the subunits of elastin and help account for the rubberlike qualities of this protein
DESMOSINE AND ISODESMOSINE
is resistant to digestion by most proteases
Elastin
easily hydrolyzed by pancreatic elastase
Elastin
a family of proteins related to the scaffolding necessary for the deposition of elastin
- forms a core of 10-nm microfibrils in the first stage of elastic fibers development
FIBRILLIN
results from mutations in the fibrillin gene
- a disease characterized by a lack of resistance in the tissues rich in elastic fibers
MARFAN SYNDROME
highly hydrated, transparent, complex mixture of macromolecules
EXTRACELLULAR MATRIX: GROUND SUBSTANCES
EXTRACELLULAR MATRIX: GROUND SUBSTANCES
o principally in three classes:
o glycosaminoglycans (or GAGs)
o proteoglycans
o multiadhesive glycoproteins
TEM: connective tissue extracellular matrix reveals ground substance as either ________________ that fills spaces between the collagen and elastic fibers and surrounds fibroblast cells and processes
empty or containing fine granular material
linear polysaccharides formed by repeating disaccharide units usually composed
GLYCOSAMINOGLYCANS
GLYCOSAMINOGLYCANS originally called
mucopolysaccharides
2 examples of GLYCOSAMINOGLYCANS (GAGs)
o Uronic acid - Glucuronic or iduronic acid
o Hexosamine - Glucosamine or galactosamine
The four main GAGs found in proteoglycans are:
o Dermatan sulfate
o Chondroitin sulfates
o Keratan sulfate
o Heparan sulfate
are composed of a core protein to which are covalently attached various numbers and combinations of the sulfated GAGs
PROTEOGLYCANS
PROTEOGLYCANS function
anchoring cells to the matrix
cell-surface proteoglycans
- are present on many types of cells, particularly epithelial cells
SYNDECAN-
one of the most important ECM proteoglycans
- the dominant proteoglycan in cartilage
AGGRECAN
Several disorders have been described in which a deficiency in lysosomal enzymes causes glycosaminoglycan degradation to be blocked, with the consequent accumulation of these compounds in tissues. What are these diseases?
Hurler, Hunter, sanfilippo, and Morquio syndromes.
- Bacteria that produce ___________, an enzyme that hydrolyzes hyaluronic acid and other glycosaminoglycans
- have greater invasive power because they reduce the viscosity of the connective tissue ground substance
hyaluronidase
o have a frequently branched carbohydrates moiety attached, but in contrast to proteoglycans the protein moiety usually predominates
o several such glycoproteins have important roles in the adhesion of cells to their substrate
o stabilizes or holds the position of each cells in the extracellular matrix
MULTIADHESIVE GLYCOPROTEINS
is an important example synthesized by fibroblasts and some epithelial cells
- with a molecular mass of 22-240 kDa
- has binding sites for collagens, certain GAGs, and integrins of cell membranes
FIBRONECTIN-
trimeric, a larger, cross-shaped glycoprotein
- participates in the adhesion of epithelial cells to the basal lamina
- has binding sites for type IV collagen, GAGs, and integrins
- all basal laminae are rich in
laminin
Two general classes of connective tissue
LOOSE CONNECTIVE TISSUE
DENSE IRREGULAR CONNECTIVE TISSUE
contains faint ground substance with fine fibers of collagen and is adjacent to epithelium.
LOOSE CONNECTIVE TISSUE
tissue underlies the thinner layer of
loose connective tissue and is invariably much richer in larger bundles of collagen
DENSE IRREGULAR CONNECTIVE
o supports many structures which are normally under some pressure and low friction
o Usually supports epithelial tissue, forms a layer around small blood and lymphatic vessels, and fills the spaces between muscle and nerve fibers
LOOSE CONNECTIVE TISSUE
LOOSE CONNECTIVE TISSUE Also found in:
- papillary layer of the dermis
- hypodermis
- linings of the peritoneal and pleural cavitie
- in glands
- in mucous membranes (wet membranes that line the hollow organs) supporting the epithelial cells.
LOOSE CONNECTIVE TISSUE Also called as
AREOLAR TISSUE
are the most numerous cells IN LOOSE CONNECTIVE TISSUE
Fibroblasts and macrophages
offers resistance and protection
o has the same components found in loose connective tissue, but there are fewer cells and a clear predominance of collagen fibers over ground substance
DENSE CONNECTIVE TISSUE
DENSE IRREGULAR CONNECTIVER TISSUE
o known as dense irregular connective tissue when the collagen fibers are
arranged in bundles without a definite orientation
collagen fibers form a 3-dimensional network in dense irregular tissue, providing resistance to stress from all directions
o often found closely associated with loose connective tissue
DENSE IRREGULAR CONNECTIVER TISSUE
DENSE REGULAR CONNECTIVE TISSUE
o collagen bundles are arranged according to a
definite pattern
collagen fibers aligned with the linear orientation of fibroblasts in response to prolonged stresses exerted in the same direction offering great resistance to traction forces
DENSE REGULAR CONNECTIVE TISSUE
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 fibers of type III collagen
MUCOUS TISSUE
o found mainly in the umbilical cord and fetal tissues
o principal component of the umbilical cord, referred to as
Wharton’s jelly
similar form of connective tissue is also found in the pulp cavity of young teeth
MUCOUS TISSUE
MUCOUS TISSUE has an abundance of ground substance composed chiefly of__________, making it a jellylike tissue containing very few collagen fibers with scattered fibroblasts
hyaluronic acid