Connective Tissue & Cartilage Flashcards
What are the broad classifications of CT
- Connective tissue proper (soft tissue): components in a fluid or gelatinous ground substance
- Supportive CT (hard tissue): Components embedded in a solid ground substance
What are the classifications based on
- Relative density of components
2. Characteristics of ECM
What are the types of loose CT proper
- Areolar
- Adipose
- Reticular
- Hemopoietic
What are the types of dense CT Proper
- Irregular arranged
2. Regular arranged: Tendons, Ligamens
What are components of CT
- Fibers
- Ground substance
- Cells
What are the types of fibers
- Collagen
- Elastic
- Reticular
What are some features of collagen fibers
- Don’t stretch or contract
- Heat labile: becomes gelatinous and gluelike
- High molecular weight
- Composed of glycine, proline, and hydroxyproline
- Basic molecule (monomer): tropocollagen
- Fibers are straight/wavy
- Loosely or densely packed depending on the location and functional need
How is collagen produced?
- Intracellular
2. Extracellular
What is the precursor of collagen intracellularly
procollagen
What produces collagen
fibroblast
What are characteristics of procollagen
- helical tripeptide composted of 2 alpha-1 and one (alpha-2)
- Held together by hydrogen bonds.
Where does the synthesis of intracellular collagen fibers occur
Rough ER: Proline and lysine are hydroxylated. Ascorbic acid acts as a cofactor (coenzyme) and then moves to Golgi for glyprorotein addition
What is the synthesis of extracellular tropocollagen
- procollagen cleaved to form tropocollagen via prollagen peptidase
- cross links bet tropocollagen molecules polymerize (lysyl oxidase) to form microfibrils.
- Microfibrils form fibrils
- Fibrils form fibers (collagen) and bundles (collagen)
What are the types of collagen?
- Type 1: most common
- Type 2: cartilage
- smooth muscle, aorta, uterus, spleen, lungs
- Type 4: basal lamina
- Type 5: placental membranes
What are the features of elastic fibers
- Can stretch and return to original size.
2. Resistant to heat
What is the composition of elastic fibers
- Elastin (amorphous protein) surr by microfibrils (fibrillin)
- Elastic protein: rich in glycine and proline (valine, alanine, desmosine and isodesmosine)
What are features of reticular fibers
- Usually loc where collagen is found but not vice versa
- Abundant at boundaries bet CT and other tissues
- Forms majority of stroma in bone marrow, lymphoid tissues, liver
- Not easily diff from collagen or elastin with H&E staining
- Stains darker w/PAS than collagen
- Fibers are argyrohillic- blackens with silver stains
- Very similar to collagen
What is the composition of reticular fibers
Type III collagen fibrils (Never forms bundles!)
What is ground substance
A mixture of proteins, lipids, carbs, and water, varies in consistency from a viscous solution to a hard material
What are the components of ground substance
- Glycoproteins
2. Glycosaminoglycans (GAGS)
What are GAGs
- polysaccarides with 1+ amino sugar moieties
- long, branching polymers, form 3d networks for strength and support.
- have many hydrophilic groups
- may serve as a selective barrier to diffusion of inorganic ions and charged molecules.
- ex: hyaluronic acid, chondroitin sulfate, dermetan sulfate
What are features of ground substance
Viscosity of ground substance is related to types of GAGs present
What are the common types of GAG’s
- Hyaluronic acid: non sulfated GAG capable of binding large amounts of water. Its present in large amounts in skin and contains glucosamine
- Chondroitin sulfate: sulfated GAG, present in the hard CT (cartilage)
What are components of loose connective tissue
All three types of fibers: collagen, elastin, and reticular
What is the function of loose areolar CT
binds organs together; loosely arranged collagen predominates
What is the function of Adipose CT and which structure predominates.
Fat storage; adipocytes predominate
What is the function of reticular CT and which structure predominates
Forms stroma of lymph nodes, liver, spleen and bone marrow. Reticular fibers predominate
What are the cells of loose CT
- Fibroblast
- Mesenchymal
- Adipocytes
- Macrophages
- Mast cells
What are features of fibroblasts
- fusiform or stellate shaped
- nucleus composed of fine chromatin
- 1-2 nucleoli
- arise from other fibroblasts or mesenchymal cells
- most common cell in loose CT
What is the function of fibroblasts
Produces fibers and ground substance, very impt in repair during wound healing
What are the features of mesenchymal cells
- similar to fibroblasts, except that chromatin is more coarse
What is the function of mesenchymal cells
Undifferentiated stem cells capable of giving rise to other cells of mesenchymal origin
What are features of adipocytes
Unilocar (yellow) fat:
- form severeal small lipid droplets
- fuse into a single large droplet
- cytoplasm and nucleus displaced peripherally
- multiocular (brown) fat, the adipocytes retain multiple lipid droplets
- main component of adipose tissue
What is the function of adipocytes
store lipids
What are the features of macrophages
- irregular outline, avoid nucleus
- usually distinguished from fibroblasts by the presence of phagocytosed matter
- May fuse to form giant cells
What is the function of macrophages
- phagocytosis of cell debris, altered intercellular material, microorganisms and foreign material
- contribute to the initiation of the immunological reactions of the body by processing antigens.
What are the the features of mast cells
- granulocyte
- cytoplasm full of secretory granules (vesicles)
- usually assoc. with capillaries
- small, dark staining nucleus
What are the function of mast cells
contain heparin (anticoagulants) and histamine (dilates blood vessels)
What are hematopoetic tissue
arises from stem cell and can become myloid or lymphoid. Lymphoid diff into B or T cells. B cells prod antibody and can prod plasma cell. Myloid prod RBC, platelets, and granulocytes.
What are features of lymphocytes
smallest of cells in the CT, large dark staining nucleus, thin rim of basophilic cytoplasm.
where are lymphocytes loc
numerous in CT, supp the epithelium of the respiratory and GI tracts.
What are the function of T cells
cell mediated immunity; direct and regulate immune responses, directly attack infected or cancerous cells.
What are B cells
recognize antigen, each B cell is programmed to make one specific antibody
What are plasma cells and what is its features
B cells that produce antibody
- oval shaped, cytoplasm stains basophilic as a result of its large content of rough ER
- Eccentric nucleus with perinuclear halo
- Heterochromatin disposed around the periphery of nucleus, giving a “cartwheel” appearance
What are the function of plasma cells
- Responible for humoral immunity
2. synthesize and secrete antibodies that will travel in the blood to gain access to the CT spaces.
what are lymphoid cells
leukocytes which are white blood cells. They mature in lymphoid tissue, utilize vascular channels for transport to the CT. They’re made up of T cells, and B cells, and plasma cells.
What are myeloid cells
- Leukocytes: cells of myeloid origin; dev in hemopoietic tissue, mature and move into CT form blood vessels; function in the CT
- Ex are neutrophils, monocytes and eosinophils
What are features of monocytes
Large cells
What are function of monocytes
- precursor to macrophages
- monocytes are phagocytes that circulate in the blood
- When monocytes migrate into tissues, they develop into macrophages and function in phagocytosis
What are features of neutrophils
- Granulocyte
- contain lysosomes
- lobulated nucleus; usually 2-5 lobes
What is the function of neutrophils
- acute inflammation
2. phagocytose bacteria
What are the features of eosinophils
- granulocyte
- usually bilobed
- contain cytoplasmic granules (stain red in a blood smear using wrights stain)
what is the function of eosinophils
- allergy, parasites, phagocytosis of antigen-antibody complexes
- some granules contain profibrinolysin which prevents intravascular clotting
What are features of basophils
- granulocyte
- rare in CT; see them mostly in bone marrow
- Wrights stain on blood smears: cytoplasmic granules are blue to purple
What are function of basophils
- granules contain heparin (an anticoagulant) and histamine (a vasodilator)
- precise function unknown
What are general features of dense CT
Differs from loose CT mainly in the preponderace of fibers (collagen) over cells and ground substance
What are the two types of dense CT
- dense irregular
2. dense regular
What are features of dense irregular CT
Fiber bundles form interwoven sheets, without regular orientation, collagen fibers predominate, some elastic and reticular fibers may be present.
What is the function of dense iiregular CT
Comprises dermis of the skin, fibrous sheaths of cartilage and bone, capsules of some organs. It occurs in area where tensions are exerted in several directions.
What are features of dense regular CT
- Mostly collagen fibers, occasional elastic fibers.
2. Orderly, parallel arrangement
What is the function of dense regular CT
- Comprises tendons, ligaments, aponeuroses
2. Occurs in structures subject to tension in one direction
CT also plays a major role in ____fluid and _____
interstitial; inflammation
What is interstitial fluid
Fluid that exits the blood vascular system through the capillaries
What is the function of interstitial fluid
Delivers nutrients to cells; carries waste material from the cells
What is the formation of hydrostatic pressure like (Think fluid as driving force)
- The hydrostatic pressure within the capillaries causes fluid to “leak” out of the capillaries into the interstitial space.
- Small molecular weight substances are carried along
- Large molecular weight material is unable to leave the vessels due to close approximation of endothelial cels.
What is the formation of osmotic pressure like (think particles as driving force)
- Fluid reenters venules
- Hydrostatic pressure is reduced in the venules (relative to arterioles)
- Osmotic pressure in venules is higher than in arterioles as a result of fluid loss from the capillaries.
Does all fluid return to the blood vascular system?.
No; numberous “blind end” lymphatic capillaries are present in the interstitium. Tissue fluid becomes known as lymph after it enters the lymphatic system.
What is edema
excess tissue fluid present in the CT spaces 2/2 imbalance of fluid of fluid dynamics
What are two ways edema can happen
- Increased formation of tissue fluid
2. Decreased resorption of tissue fluid.
Describe increased formation of tissue fluid
- Increased hydrostatic pressure in the capillaries
- Inc permeability of capillary endothelium results in a leaking of blood colloids into tissue spaces
Ex: venous obstruction, venous thrombosis, cardiac failure
Describe decreased resorption of tissue fluid
- Lowered blood colloids which lowers osmotic pressure
- Consequent lowering of the resorption gradient
- Lymphatic obstruction
Ex: kidney diseases, lymphatic obstruction 2/2 tumors
What are two ways inflammation can be classified as
- Acute inflammation: initial response, short duration
- Chronic inflammation: follows acute inflammation if the casual agent is not remove; long duration, can last for months to years
What is the Lewis Triple Response
- Flush dull red line: Due to a dilation of capillaries and venules. Histamine release (mast cells) loc in close association with the capillaries.
- Flare: Due to the dilation of arterioles. This is due initially to an axonal reflex but is perpetuated by histamine (mast cells) and prostaglandins (endothelial cells)
Wheal: swelling due to localized edema; a result of fluid and large molecular weight substances leaking out of the capillaries and venules.
What are the cardinal signs of inflammation
- Heat (calor)
- Redness (rubor)
- Pain (dolor)
- Swelling (tumor)
- Loss of function (functio laesa) - later stages
What is the purpose of inflammation
- Dilute toxins
2. Allow leukocytes and antibodies to access extravascular spaces.
what is the process of inflammation in summary
- Changes in the caliber of the vessels
- Changes in vascular permeability
- Changes in vascular flow
- Stasis
What is the first stage of inflammation
- Transient vasoconstriction: initial response of arterioles, varies with degree of injury (sec to mins); likely neurogenic
What is the second stage of inflammation
Vasodilation: First involves capillary beds and venules; later arterioles. Vasodilation of arterioles results in the further opening of microvascular beds in the area. The increased blood flow is responsible for the redness and the heat seen in inflammation. Increased volume in the capillaries and venules results in inc local hydrostatic pressure which causes a transudation of protein poor fluid into the extravascular space.
What is the 3rd stage of inflammation
increased permeability: capillaries and venules; due to chemical mediators; causes an outpouring of protein -rich fluid into the extravascular spaces; results in loss of fluid in vessels–>inc conc of red blood cells–>concomitant slowing of blood flow 2/2 inc viscosity.
What is the 4 th stage of inflammation
Stasis (slowing of blood flow); increased margination of WBC and thus inc diapedesis (movement of WBC out of the blood vessels)
WHat do chemical mediators originate from in inflammation
plasma, cells, damaged tissue
What are classes of inflammation
- Vasoactive amines (histamine and serotonin)
2. Vasoactive polypeptides formed by specific enzyme action; breakdown products of proteins and tissues
What are other agents that influence inflammation
- toxins from bacteria
- prostaglandins from endothelial cells
- lysosomal enzymes (from neutrophils)
- products of DNA and RNA breakdown
- Antigen-antibody complexes.
What are the cellular events of acute inflammation
- Emigration of neutrophils-predominate for the first 6-24 hours
- During this period there is some emigration of monocytes (which transform to macrophages)
- Presence of monocytes inc for the first 24-48 hours
- Phagocytosis and release of enzymes by neutrophils and macrophages
- Phagocytosis and rel of enzymes by neutrophils and macrophages
- cell death of leukocytes and if involved, bacteria
- If pyogenic bacteria involved, there is formation of pus
- If inflammation is due to allergic reaction, then large numbers of eosinophils will be present.
What are the highlights of chronic inflammation
- Reductions in numbers of neutrophils
2. Appearance of lymphocytes and plasma cells.
____play an important role in chronic inflammation
Macrophages
There is proliferation of vascular ____ which forms new capillaries and there is proliferation of ____ and ____ production and subesequent fibrosis
endothelium; fibroblasts and collagen
Chondroblasts=
chondroctyes=
chondro= cartilage blast= immature cell cytes= mature cell
What are components of cartilage?
- Chondroblasts and chondrocytes
- Fibers: collagen/elastic
- Ground substance: chondroitin sulfate and keratan sulfate
- Matrix: fibers + ground substance
What are the characteristics of hyaline cartilage
- comprises the skeleton of the embryo
2. progressively replaced by bone beg in the fetus and ending in the young adult.
What are features of hyaline cartilage
- Preponderance of intercellular material (matrix):
- 40% of matrix = type 11 collagen
- Matrix appears homogenous: fibrous and amorphous portions have the same index of refraction thus fibers can not be seen with the light microscope.
What are the types of cartilage
- Type 1: most common
- Type 2: cartilage
- Type 3:
- Type 4: basement membrane
What are features of hyaline cartilage
- amorphous ground substance: chondroitin sulfate and keratan sulfate
- younger cells are within small somewhat flattened lacunae; older cells in large round lacunae
- cells nests are present in areas where cells retain the capability of mitosis
- perichondrium is present
where is hyaline cartilage located
- ends of long bones, nose, larynx, trachea, bronchus, between ribs.
what are features of elastic cartilage
- pliable type of cartilage
- differs in appearance from hyaline cartilage:
- fibers are a noticeable component of the matrix
- predominantly elastic fibers
- perichondrium is present
Where is elastic cartilage located
external ear, epiglottis
what are features of fibrocartilage
- very fibrous; predominantly collagen fibers. (Both type 1 anf type II)
- Differs from hyaline and elastic cartilage:
- fewer lacunae per unit area
- develops from dense CT instead of mesenchymal tissue
- No perichondrium
Where is fibrocartilage located
tendon insertions, pubic symphysis, and intervertebral discs.
Hyaline and elastic cartilage dev from ______
mesenchyme
Mesenchymal cells differentiate into _____
chondroblasts
When chondroblasts become entrapped in lacunae they are then termed ____
chondrocytes
small aggregates of chondrocytes are called:
isogenous groups
what is perichondrium derived from
mesenchymal cells surrounding the developing cartilage
What are components of the perichondrium
- Outer layer: fibroblasts, mesenchymal cells
- Inner layer: Chondrogenic layer; chondroblasts undergo mitosis to produce more chondroblasts
- some will secrete matrix and entrap themselves in lacunae to become chondrocytes
What does fibrocartilage dev from
dense CT; no perichondrium
What are the two types of growth of cartilage
- Appositional growth: Only when you have perichondrium
2. Interstitial growth
What are features of appositional growth (hyaline and elastic)
- growth only occurs on the surface
- allows growth in WIDTH only
- new layers of cartilage are laid down around the perimeter of the existing cartilage
- dependent upon the mitotic activity of the chondrogenic layer of the perichondrium
- remove the perichondrium, and appositional growth will cease
What are features of interstitial growth (fibrocartilage, hyaline, and elastic)
- new cartilage is added within existing cartilage
- inc length during enchondral bone formation
- cell nests are formed as a result of mitotic activity within lacunae
- newly formed cells within the lacunae secrete matrix, form own ind lacunae.
- continued secretion of matrix results in the lacunae moving apart from each other
Cartilage is ____therefore it gets its nutrients by ______ of tissue fluid through the matrix. The tissue fluid originates from blood vessels located outside the _____. Invasion of cartilage by blood vessels is associated with calcification and ____ of the cartilage.
avascular; diffusion; perichondrium; death
