Connective Tissue Flashcards
Functions of connective tissue.
major structure, connectivity and support; hormonal-induced cell growth and differentiation; nutrient and metabolic wastes exchange, temperature, salinity (most abundant tissue in the body)
Components of connective tissue.
Cells
Fibers
Ground Substances (heterogeneous): GP’s, GAG’s, & PG’s
Extracellular matrix
Protein Fibers: Collagen, Reticular, Elastic
Different protein fibers are associated with different connective tissue cell types
- Hyaline cartilage is very well hydrated
Fibroblasts/fibrocytes
- Synthesis of collagen, elastin, PG’s, GP’s & extracellular cell components
- Undifferentiated cells until exposed to environment with particular growth factors, in which they will mature into fibrocytes (happens to osteoblasts too)
- Represented in all tissues except adipose tissue
What type of cells are chondrocytes/blasts in the cartilage?
fibroblasts/fibrocytes
This type of cell is found in tissue with alot of filtration.
Collagen Type III
This type of cell is found in highly vascularized tissues.
reticular fibers
Differences between fibroblasts and fibrocytes.
Fibroblasts: The nucleus is large, load of mitochondria, elongated golgi apparatus, have alot of transcription taking place with little chromatin being condensed. In blast form the DNA activity is very high, but in the cytes the nucleus is condensed.
Fibrocytes: has minimal functionality because most of the DNA is coiled, allow for little transcription and decreasing cell metabolism (space saving cells)
Derived from hematopoietic pluripotential cells in RBM.
macrophage
Are classified based upon their location; Liver: Kupffer, Bone: Osteoclasts, Skin: Langerhans Cells etc.
macrophage (monocyte)
Manage the bone calcium metabolism of the body.
osteoclasts
Mast cells
Store chemical mediators to inflammatory responses
Two types:
a. CT-skin, peritoneum
b. Intestinal mucosa & lungs
Contain basophilic metachromatic secretory granules-locally paracrine (Heparin/chondroitin sulfate - mucosal, Histamine, Proteases, ECF-A, SRS-A - leukotriene).
mast cells
- Arise from B lymphocytes
- secondary function is connective tissue
- Present in CT assoc. with wet epithelia and Lymphoid Tissue
- Synthesize Ig’s (antibodies)
plasma cells
Adipocytes
- Storage of neutral fats/heat production
- Everywhere in connective tissues except joint capsules
- One of the most abundant cells in the body
Eosinophil
- Large granules, containing bioactive substance for antiparasitic agents & histamine
- mediate inflammatory responses due to allergic reactions in a weak way
= Linked bilobed, sausage -shaped nucleus
Basophils
- Dense, dark, large granules (Large allergic reaction response)
- Bilobular but NOT polynucleated!
Lymphocytes
- respond to viral infections
- Specialty of lymphocytes: responding to inflammatory response
Type T and Type B cell types
T: acquired immunity cells that are found in the lymph – learn antigens in the thymus during childhood and adolescence
B: innate immunity; produce faster, antibodies
- Small cytoplasmic granules
- Linked Polynucleated & lobulated nucleus
- Respond to bacterial infection
- Polylobulated (over five lobules is pathological)
Neutrophil
WBC chemotaxis emigration is achieved through what?
Diapedesis
kamikazee cells!!
Once the cell goes through into the interstitial fluid it cannot go back, it will die at site of inflammation.
Neutrophil life span = 4-6 hours; body gets rid of it after this process
The neutrophils will die faster and chances to die are higher because they are the first cells sent out in any immune response.
Meshwork-forming fibrils:
collagen type IV (structural-BL); most complex because they allow multiple interactions of biochemical agents → highly reactive; associated to the basement membrane (only the basal lamina component)
Long fibrils:
collagen types I (everywhere in the body that is collagen based, most abundant), II (wherever there is type I, usually there is type II), III, V, XI
Short connecting fibrils:
collagen types IX, XII, XIV,XVI,XIX,XX,XXI (FACIT’s)
Hexagonal network-forming:
VIII, X
Transmembrane:
XIII, XVII (hemidesmosomes), XXIII, XXV
Multiplexins:
XV, XVIII (BM region)
Anchoring fibrils:
collagen type VII (attaching-BL)
Collagen amino acid components.
Sequence: Glycine, proline, hydroxiproline, hydroxylysine (Gly-X-Y)
regardless of the type of collagen the 4 template AAs are seen, the order is what is varied!
Collagen Type I Biosynthesis
- Formation of preprocollagen assembled on polysomes.
- Hydroxilation of the proline & lysine component of preproprocollagen by respective enzymes.
- Attachment of carbohydrate group to hydroxylysine.
- Registration peptides extra length sequence to each alpha chains.
- Transportation of soluble procollagen to golgi and subsequently to the extracellular environment.
- Removal of registration peptides from procollagen becoming insoluble tropocollagen.
- Collagen fibrils aggregate to form fibers.
- Reinforcement of fibrillar collagen among each tropocollagen molecule.
- Fibers aggregate to form bundles
Forms collagen.
tropocollagen
Reticular fibers
Collagen type III-thinner fibers than collagen type I
strong, short, and able to keep framework/shape of an organ
Highly glycosylated, thus not seen with standard H & E , but with silver stains and PAS.
Form networks as supportive lattices to allow free movement to motile cells (i.e. lymphocytes).
Locations of reticular fibers throughout the body.
Muscles (make connection of epimysium, perimysium, and endomysium)
Spleen
RBM
Liver (when pt has cirrhosis, based on structural standpoint of connective tissue; these fibers take over liver and can no longer filter blood, and toxins stay in body. Bile into blood–>jaundice)
Lymph nodes (keep structure of lymph node- when swollen, node is hard. Swelling is enlargement of spaces inside the lymph node and expansion of the parenchyma of the reticular fibers)
Osteogenesis imperfecta (type I abnormality)
brittle bone disease
Kniest dysplasia (type II abnormality)
- Abnormalities of certain joints (sutures and syndesmosis)
- Have a really pronounced forehead, eyes too close together – because sutures are fusing before they are supposed to
- Kids have short stature
Ehler’s Danlos - type IV (type III abnormality)
Kids exhibit blood in urine; urination is painful/burning; also have proteinuria, hematuria, and glycosuria; fast heartbeat; anemia (because peeing out RBCs); chronic fatigue (really random symptoms so often misdiagnosed)
Problem with nephron– missing type 4 collagen in basement membrane
Alport’s syndrome (type IV abnormality)
- Similar to Ehler’s Danlos
- Alports is type 4 ONLY
Stickler’s syndrome-II ( type XI abnormality)
Problems hearing until they go deaf, also blind because retinas detach
Ossicles have collagen, so if ossicles can’t vibrate, signal transduction never gets sent to brain.
Elastic fibers
Physical Properties: Abundant in CT, Extremely elastic in response to tension adapted to local tissue needs.
Location: CT, blood vessels , ligaments (e.g. flavum; SLP; vocal).
Molecular Composition: Similar to Collagen - Proline and Lysine-like, two additional amino acids: Desmosine and Isodesmosine
Proteoglycans (PG’s): A core protein with attached GAG’s: Five major classes differing on their sugars:
Hyaluronic acid - not attached to core protein; does NOT form PG’s but PG aggregate. Chondroiting sulfate Dermatan sulfate Ketaran sulfate Heparan sulfate
Ground substance
Amorphous (can be any shape)– has lots of water as general solvent; necessary for all the proteoglycan components
Filling Colorless complex of Proteoglycans, GAG’s and Glycoproteins among cells and fibers in CT.
Proteoglycans
- Structural components of the matrix (i.e. anchoring cells)
- Binding of protein growth factors (TGF-β)
- keep water inside CT
- allows us to stain tissues
Glycoproteins
Main goal: keep connective tissues hydrated
- Much smaller than PG’s
- Less carbohydrate and its chains are shorter and branched
- Mediate cell adhesion and migration
- Cell-extracellular environment integration
- Depending on shape all GP’s act differently
Examples:
Fibronectin: Cells-extracellular matrix
Laminin: BL in epith. cells
Two types of immature CT.
Embryonic CT two types:
Mesenchyme - everywhere, Give rise to mature tissues, Amount of mesenchyme decreases drastically in adolescence, none after the age of 30 and have all mature types
Mucous - Mostly represented in umbilical cord and attachment to placenta
Loose CT
areolar, adipose, reticular
Dense CT
regular, irregular, elastic
Cartilage
hyaline, fibrous, elastic
Special CT
bone, blood, lymph
Areolar CT
all fibers except reticular - Peritoneum, subcutaneous skin, around nerves
Regular dense CT location
Most tendons & ligaments
Irregular dense CT location
Fascia & periosteum, pericardium, heart valves
- loosely arranged
Elastic dense CT location
Lungs, arteries, vocal cords, suspensory lig. of penis, etc.
Adipose connective tissue
Adipose stem cells are different - come directly from mesenchymal cells
- Differentiates into fibroblasts and lipoblasts which can then divide into multilocular adipocyte or unilocular adipocyte
- Adults keep brown fat (multilocular)
- Once it decides to differentiate into fat tissue, can no longer be fibroblast
- Fat cell cannot divide; but it can grow
Cartilage tissues
- Subdivided into hyaline and elastic and fibrous
- Regardless of which one, cartilage has a high amount of brown substance
- A LOT of water= hyaline (thanks to proteoglycans)
- Rich content of GAG’s & PG’s
- Specialized to cope with mechanical stress without distortion
- Support soft tissues and promotes development and growth of long bones
Cartilage tissues - hyaline
Concentration of proteoglycans increases around cell = give ground substance new name
In between chondroblasts and chondrocytes = interchondral territory
In between lacunae area= territorial
Location - Epiphysis of long bones, nose, ribs, trachea, bronchi, etc.
Endochondral ossification.
Chondrocytes undergo different cellular stages of division until they become numerous in zone of proliferation.
Organic components are recycled and reused by ground substance to feed bone cells so they can manufacture bone material.
Cartilage tissues - fibrous
Location - Pubic symphysis, intervertebral discs (in annulus fibrosis), knee menisci, etc.
A lot of collagen fibers, but NO elastic
Cartilage tissues - elastic
Location - Auricle, epiglottis, etc.
Osteoblasts
Associated with bone formation; secretes organic components with mineral salts: found on bone surface: no mitotic ability
Osteocytes
Develop from osteoblasts entrapped by matrix: mature bone cells; maintain daily cellular activities of bone tissue; no mitotic ability
Osteoclasts
Develop from circulating monocytes; found on bone surface; involved in bone reabsorption
Bone tissue
Location - Compact: periphery of long bones. Spongy: Irregular & flat bones, in bone marrow area/center of bone
What easily distinguishes compact bone?
osteons
Largely responsible for bone homeostasis.
osteoclasts
Bone matrix
Inorganic Compounds: Bone Minerals (50%) Hydroxyapatites: Ca+2 , P+, OH- Bicarbonate, Mg, Citrate, K & Na Organic Compounds: Osteoid Made of cells, fibers that are alive Fibers: Collagen I & Tropocollagen Periodic lacunar regions Ground Substance: Bone components embedding Proteins (glycoproteins,sialoproteins,etc.) lipids, carbohydrates (GAG’s) & Proteoglycans.
Periosteum
Fibrous layer: DRCT
Sharpey’s fibers- anchoring periosteal collagen fibers
Osteogenic layer: DRCT
Osteogenic cells: bone growth & repair
Endosteum
Reticular CT
