2. CONNECTIVE TISSUE
it forms a continuum with the epithelial, muscular, nervous tissue or other components of the connective tissue itself to ensure functional
integration of the organism.
It derives from the mesoderm layer, in particular from the middle layer from which the pluripotent cells of the mesenchyme develop.
Mesenchymal cells (primitive, non-specialized cells that can develop into different types of cells in the body) spread throughout the body
giving rise to connective tissue and related cells
- bone
- fatty tissue
- blood
these fabrics are very different from each other, but they have in common:
- have specialized cells
- extracellular protein fibers
- fluid / ground substance that they themselves produce
most important functions:
- structural support: cartilage, tendons and ligaments
- medium (exchanges): waste products and metabolites e.g. oxygen
- participation in the processes of defense and protection of the organism: phagocytic activity of cellular debris, microorganisms,
immunocompetent cells. which produce antibodies against antigens, cells that process pharmacological substances that control the
inflammatory process
- fat storage
connective tissues are made up of:
EXTRACELLULAR MATRIX . (collagen and elastin)
secreted by the cells themselves, depending on the tissue in which we find ourselves, the matrix can present itself in various forms:
- fluid: blood and lymph, transport connective cells (erythrocytes, leukocytes...)
- solid but loose: allows the passage of blood vessels
- calcified: bone tissue that allows the formation of very resistant structures
It has the property of resisting compression and stretching forces, is produced by the cells themselves and is composed of:
FUNDAMENTAL SUBSTANCE . amorphous, hydrated matrix composed of:
- GAG glycosaminoglycans, long linear polymers of disaccharide units (heparin, dermatan sulfate)
- proteoglycans, protein axis to which glycosaminoglycans are covalently bound
- adhesive glycoproteins, large molecules that act as glue for the various components of the matrix (lamin, fibronectin)
FIBERS that can be
1. collagen. collagen is formed by the association of tropocollagen subunits. The triple peptide chains of tropocollagen align longitudinally
and associate in parallel in a regularly out-of-phase fashion to form collagen microfibrils.
these fibers are particularly resistant to traction, thanks also to its organization in bundles it is able to withstand considerable mechanical
stress as in the case of tendons
- type 1. thick fibers with parallel or intertwined pattern (bone, tendon, dentin, skin)
- type 2. thin fibers (hyaline and elastic cartilage, vitreous body)
- type 3. thin fibers that cover other tissues or that form textures of many organs (reticular tissue, loose connective tissue that covers smooth
muscle)
- type 4. fibers placed under the thin epithelia and intertwined in a reticulate (basal membranes)
- type 5. ammyotic sac, chorion, muscle and tendon sheaths
2. reticular. 0.2 - 1 micrometre diameter, form three-dimensional scaffolding in many organs (liver, spleen, lymph nodes, smooth muscle,
glands)
They are less thick than those of collagen and have a different arrangement (plexus structure - network, therefore intertwined)
3. elastic. very extensible, their length can increase up to 150%.
they are made up of micro-fibrils which, unlike collagen fibers, blend together. They contain elastin and fibrillin.
we can find them organized in flattened sheets (blood vessels) or arranged in bundles (dermis).
they are also present at the level of the lung, in the cartilage of the auricle, in the nuchal ligament
FIXED CELL COMPONENT fixed or migrated are classified according to the position of the precursor cells of the connective
tissue
MESENCHIMAL CELLS: all the cells of the connective tissue proper come from the mesenchymal tissue: an embryonic tissue with a high
proliferative capacity. They are stem cells found in different types of connective tissue. Stem function: undifferentiated cells that act as
precursors for other connective tissue cells. They are able to respond to insults and infections by dividing and giving rise to cells that
differentiate into fibroblasts, macrophages or other connective cells.
FIBROBLASTS: they derive from the mesenchymals, they are responsible for the production of the connective tissue matrix.
active fibroblasts are often found in association with bundles of collagen fibers. They are spindle-shaped cells, with little colored cytoplasm.
The nucleus is voluminous and ovoid, actin and a-actin are localized at the periphery of the cell, while myosin is distributed throughout the
cytoplasm.
, resting fibroblast is represented by smaller and more ovoid cells, smaller nucleus, poorly developed rer and golgi.
MYOFIBROBLASTS: histologically it is not possible to distinguish a fibroblast from a myofibroblast. They show bundles of actin filaments
and dense bodies typical of smooth muscle cells but differ from these in that they lack a basal lamina sheath. they are abundant in the
wound repair process.
PERICITES: derive from undifferentiated mesenchymal cells, partially surround the endothelial cells of capillaries and venules
ADIPocytes: or fat cells, their main function is to synthesize and accumulate triglycerides.
- white adipose tissue: cells with a single lipid droplet, voluminous and round cells (150 micrometers), when they unite to form lobes they
take on a polygonal shape. They have many ribosomes and vesicles of pinocytosis, testifying to the continuous activity of absorption of
triglycerides
- brown adipose tissue: multilocular cells, present in the fetus and in the newborn, in the cytoplasm there are numerous separate vacuoles,
therefore the nucleus remains in a central position. They have more mitochondria (function of producing heat) than ribosomes, there is the
rel but not the rer.
MACROPHAGES: main function is to phagocytose, removing cellular debris and protecting the organism from the invasion of foreign
material and microorganisms. cell surface not smooth but with long fingertip extensions, eccentric nucleus, has an indentation which gives it
a kidney-shaped appearance. they have highly developed golgi and rer and many lysosomes.
They derive from a mesenchymal precursor present in the medulla. monocytes, following specific signals, migrate through the endothelium
of capillaries and venules. Macrophages accumulated in certain places have acquired specific designations:
- kupfer cells (liver)
- lung macrophages or dust cells (lungs)
- Langherhans cells (skin)
- monocytes (blood)
- tissue macrophages (connective tissue)
- osteoclasts (bones)
MIGRANT CELL COMPONENT
MAST CELLS or mast cells: voluminous cells (20/30 micrometres) of an ovoid shape with a central nucleus. Characteristic for the presence
in the cytoplasm of numerous granules. The granules are surrounded by a membrane and contain heparin (anticoagulant function), sulfur
gag, histamine (vasodilator action, promotes exchange at the level of the vessels, neutral proteases, esinophilic and neutrophilic
chemotactic factor).
they intervene in the premature immune response (allergic response and immediate hypersensitivity). The plasma membrane of the mast
cell contains receptors to which the IgE produced by plasma cells binds. The binding between antigen and IgE determines the release of
mediators:
- leukotrienes
- thromboxanes and prostaglandins
- chitokines and the factor TNF a
PLASMA CELLS: derived from B lymphocytes, they are present in all connective tissue, but especially where there is inflammation or
penetration of foreign material or microorganisms. voluminous 20 micrometres, ovoid, eccentric nucleus, basophilic cytoplasm due to the
- presence of developed rer and golgi. Russell's bodies contain and accumulate immunoglobins
WBCs or white blood cells: circulate in the blood especially in inflammatory conditions, cross the wall of the capillaries to prune into the
connective tissue where they perform their function.
- neutrophils engulf and digest bacteria in places where there is acute inflammation, where the accumulation of cellular debris and
neutrophils gives rise to pus
- eosinophils such as neutrophils are attracted by chemoattractants to sites of inflammation, destroy parasites
- basophils release preformed and newly synthesized pharmacological agents which have the task of inducing, maintaining and controlling
the inflammatory process
- lymphocytes present in small numbers
FREE MACROPHAGES: when macrophages are activated during inflammation (attracted by chemotaxis), they detach from the fibers,
becoming free macrophages. The cell increases in volume and the cytoplasm appears full of granules or vacuoles of ingested material, the
membrane due to phagocytic activity presents invaginations. fundamental for phagocytic activity are microtubules and microfilaments.
have a number of common properties:
- derive from monocytes (binary blood cells present in the blood that undergo differentiation), have high phagocytic activity
- have the lgG Fc receptor
- have receptors for complement, for interleukin, for interferon.
- have the ability to present the antigen
•
it forms a continuum with the epithelial, muscular, nervous tissue or other components of the connective tissue itself to ensure functional
integration of the organism.
It derives from the mesoderm layer, in particular from the middle layer from which the pluripotent cells of the mesenchyme develop.
Mesenchymal cells (primitive, non-specialized cells that can develop into different types of cells in the body) spread throughout the body
giving rise to connective tissue and related cells
- bone
- fatty tissue
- blood
these fabrics are very different from each other, but they have in common:
- have specialized cells
- extracellular protein fibers
- fluid / ground substance that they themselves produce
most important functions:
- structural support: cartilage, tendons and ligaments
- medium (exchanges): waste products and metabolites e.g. oxygen
- participation in the processes of defense and protection of the organism: phagocytic activity of cellular debris, microorganisms,
immunocompetent cells. which produce antibodies against antigens, cells that process pharmacological substances that control the
inflammatory process
- fat storage
connective tissues are made up of:
EXTRACELLULAR MATRIX . (collagen and elastin)
secreted by the cells themselves, depending on the tissue in which we find ourselves, the matrix can present itself in various forms:
- fluid: blood and lymph, transport connective cells (erythrocytes, leukocytes...)
- solid but loose: allows the passage of blood vessels
- calcified: bone tissue that allows the formation of very resistant structures
It has the property of resisting compression and stretching forces, is produced by the cells themselves and is composed of:
FUNDAMENTAL SUBSTANCE . amorphous, hydrated matrix composed of:
- GAG glycosaminoglycans, long linear polymers of disaccharide units (heparin, dermatan sulfate)
- proteoglycans, protein axis to which glycosaminoglycans are covalently bound
- adhesive glycoproteins, large molecules that act as glue for the various components of the matrix (lamin, fibronectin)
FIBERS that can be
1. collagen. collagen is formed by the association of tropocollagen subunits. The triple peptide chains of tropocollagen align longitudinally
and associate in parallel in a regularly out-of-phase fashion to form collagen microfibrils.
these fibers are particularly resistant to traction, thanks also to its organization in bundles it is able to withstand considerable mechanical
stress as in the case of tendons
- type 1. thick fibers with parallel or intertwined pattern (bone, tendon, dentin, skin)
- type 2. thin fibers (hyaline and elastic cartilage, vitreous body)
- type 3. thin fibers that cover other tissues or that form textures of many organs (reticular tissue, loose connective tissue that covers smooth
muscle)
- type 4. fibers placed under the thin epithelia and intertwined in a reticulate (basal membranes)
- type 5. ammyotic sac, chorion, muscle and tendon sheaths
2. reticular. 0.2 - 1 micrometre diameter, form three-dimensional scaffolding in many organs (liver, spleen, lymph nodes, smooth muscle,
glands)
They are less thick than those of collagen and have a different arrangement (plexus structure - network, therefore intertwined)
3. elastic. very extensible, their length can increase up to 150%.
they are made up of micro-fibrils which, unlike collagen fibers, blend together. They contain elastin and fibrillin.
we can find them organized in flattened sheets (blood vessels) or arranged in bundles (dermis).
they are also present at the level of the lung, in the cartilage of the auricle, in the nuchal ligament
FIXED CELL COMPONENT fixed or migrated are classified according to the position of the precursor cells of the connective
tissue
MESENCHIMAL CELLS: all the cells of the connective tissue proper come from the mesenchymal tissue: an embryonic tissue with a high
proliferative capacity. They are stem cells found in different types of connective tissue. Stem function: undifferentiated cells that act as
precursors for other connective tissue cells. They are able to respond to insults and infections by dividing and giving rise to cells that
differentiate into fibroblasts, macrophages or other connective cells.
FIBROBLASTS: they derive from the mesenchymals, they are responsible for the production of the connective tissue matrix.
active fibroblasts are often found in association with bundles of collagen fibers. They are spindle-shaped cells, with little colored cytoplasm.
The nucleus is voluminous and ovoid, actin and a-actin are localized at the periphery of the cell, while myosin is distributed throughout the
cytoplasm.
, resting fibroblast is represented by smaller and more ovoid cells, smaller nucleus, poorly developed rer and golgi.
MYOFIBROBLASTS: histologically it is not possible to distinguish a fibroblast from a myofibroblast. They show bundles of actin filaments
and dense bodies typical of smooth muscle cells but differ from these in that they lack a basal lamina sheath. they are abundant in the
wound repair process.
PERICITES: derive from undifferentiated mesenchymal cells, partially surround the endothelial cells of capillaries and venules
ADIPocytes: or fat cells, their main function is to synthesize and accumulate triglycerides.
- white adipose tissue: cells with a single lipid droplet, voluminous and round cells (150 micrometers), when they unite to form lobes they
take on a polygonal shape. They have many ribosomes and vesicles of pinocytosis, testifying to the continuous activity of absorption of
triglycerides
- brown adipose tissue: multilocular cells, present in the fetus and in the newborn, in the cytoplasm there are numerous separate vacuoles,
therefore the nucleus remains in a central position. They have more mitochondria (function of producing heat) than ribosomes, there is the
rel but not the rer.
MACROPHAGES: main function is to phagocytose, removing cellular debris and protecting the organism from the invasion of foreign
material and microorganisms. cell surface not smooth but with long fingertip extensions, eccentric nucleus, has an indentation which gives it
a kidney-shaped appearance. they have highly developed golgi and rer and many lysosomes.
They derive from a mesenchymal precursor present in the medulla. monocytes, following specific signals, migrate through the endothelium
of capillaries and venules. Macrophages accumulated in certain places have acquired specific designations:
- kupfer cells (liver)
- lung macrophages or dust cells (lungs)
- Langherhans cells (skin)
- monocytes (blood)
- tissue macrophages (connective tissue)
- osteoclasts (bones)
MIGRANT CELL COMPONENT
MAST CELLS or mast cells: voluminous cells (20/30 micrometres) of an ovoid shape with a central nucleus. Characteristic for the presence
in the cytoplasm of numerous granules. The granules are surrounded by a membrane and contain heparin (anticoagulant function), sulfur
gag, histamine (vasodilator action, promotes exchange at the level of the vessels, neutral proteases, esinophilic and neutrophilic
chemotactic factor).
they intervene in the premature immune response (allergic response and immediate hypersensitivity). The plasma membrane of the mast
cell contains receptors to which the IgE produced by plasma cells binds. The binding between antigen and IgE determines the release of
mediators:
- leukotrienes
- thromboxanes and prostaglandins
- chitokines and the factor TNF a
PLASMA CELLS: derived from B lymphocytes, they are present in all connective tissue, but especially where there is inflammation or
penetration of foreign material or microorganisms. voluminous 20 micrometres, ovoid, eccentric nucleus, basophilic cytoplasm due to the
- presence of developed rer and golgi. Russell's bodies contain and accumulate immunoglobins
WBCs or white blood cells: circulate in the blood especially in inflammatory conditions, cross the wall of the capillaries to prune into the
connective tissue where they perform their function.
- neutrophils engulf and digest bacteria in places where there is acute inflammation, where the accumulation of cellular debris and
neutrophils gives rise to pus
- eosinophils such as neutrophils are attracted by chemoattractants to sites of inflammation, destroy parasites
- basophils release preformed and newly synthesized pharmacological agents which have the task of inducing, maintaining and controlling
the inflammatory process
- lymphocytes present in small numbers
FREE MACROPHAGES: when macrophages are activated during inflammation (attracted by chemotaxis), they detach from the fibers,
becoming free macrophages. The cell increases in volume and the cytoplasm appears full of granules or vacuoles of ingested material, the
membrane due to phagocytic activity presents invaginations. fundamental for phagocytic activity are microtubules and microfilaments.
have a number of common properties:
- derive from monocytes (binary blood cells present in the blood that undergo differentiation), have high phagocytic activity
- have the lgG Fc receptor
- have receptors for complement, for interleukin, for interferon.
- have the ability to present the antigen
•
