Connective Tissue Flashcards
Why does interstitial fluid continuously move from capillaries into CT?
Due to hydrostatic pressure
What happens when there are too few plasma proteins in blood
Osmotic pressure decreases within vessels
Fluid leaks out of vessels into CT
Interstitial fluid
Tissue fluid that brings nutrients, electrolytes, hormones and oxygen from the blood and dumps waste products into lymph
Extracellular matrix
Major component of CT
Made of protein fibers, ground substance and interstitial fluid
Connective Tissue is formed by what components?
Cells, fibers and ground substance
Where does CT originate?
Mesenchyme
What is mesenchyme?
An embryonic tissue made of mesenchymal cells
What are the functions of CT?
Binding organs
Support
Physical protection
Immune protection
Movement
Storage
Temperature Regulation
Transport
Repair/ degeneration of damaged organs
Local CT cells
Formed locally and remain in the CT
EX: Mesenchymal, fibroblasts, pericytes, mast, adipocytes
Wandering CT cells
Formed elsewhere and remain in the CT transiently
EX: macropahges, lymphocytes, plasma cells, neutrophils, eosinophils
CT structures of the body
Bone, tendon, blood, fascia, organ capsules, fat
What is the only cell that’s able to leave the blood stream and return?
Lymphocytes
What cell is formed elsewhere and remains in the CT permanently?
Macrophages
Mesenchymal cells
Undifferentiated stem cells present throughout the body
Have long cytoplasmic processes, dispersed chromatin in the nuclei
What are the other types of mesenchymal cells?
Chondroblasts (cartilage)
Osteoblasts (bone)
Hemocytoblasts (bone marrow)
Fibroblast (CT)
Fibrocyte
Mature form of fibroblast, less active synthetic activity
Inactive at the time seen
Less RER than fibroblasts
Smaller, darker, elongated nucleus
Spindle shaped
Fibroblasts
Active permanent cells
Abundant in RER and Golgi bodies
Most prevalent CT cell type
Fibroblasts function
Synthesize collagen, reticular and elastic fibers and amorphous extracellular substance (GAGs, proteoglycans, glycoproteins)
Associated with wound healing
Macrophages
Originate in the bone marrow as monocytes
Mononuclear cells
Rich in lysosomes
Function: phagocytosis, breakdown aged cells
How do monocytes turn into macrophages?
Monocytes will circulate into the blood, then migrate to the CT, where they mature into functional macrophages
Function of macrophages
They remove large particles and form a second line of defense in the body
What are on the surface of macrophages?
IgG and IgM receptors
Giant cell
Macrophages fusing together
Multinucleated and capable of phagocytosing larger foreign bodies
Epithelioid cells
Formed when macrophages may encircle the foreign body- they become active
What macrophages are distributed around the body and make up the mononuclear phagocytic system?
Monocytes (blood)
Kupffer cells (liver)
Microglia cells (nervous system)
Langerhans cells (skin)
Dendritic cells (lymph node)
Osteoclasts (bone)
Giant cells (CT)
Where are mast cells found?
In groups near blood vessels
Loose CT (dermis- lamina propria of respiratory and digestive tracts)
Granules of the mast cell
Water soluble (metachromatic)
Contain histamine, heparin, eosinophil chemotactic factor and leukotriene C
Release in inflammatory responses/ allergic reactions
Metachromatic
Cell components changing color with metachromatic dyes
Blue dyes to red or purple
Ex: mast cells and basophils
Heparin
Anticoagulant
What do the outer surfaces of mast cells contain?
Ige receptors that mediate hypersensitivity reactions (anaphylactic shock)
What does the exposure to foreign antigen lead to? (mast cell)
- The production of Ige antibodies –> which bind to receptors on the surface of mast cells –> which then become sensitized to the antigen
- Triggers mast cells to de-granualte and release histamine and leukotriene C
What does the release of histamine do?
Increases the permeability of blood vessels (edema) and contraction of smooth muscles cells, which then can lead to dyspnea
Eosinophil chemotactic factor
Attracts eosinophils at the edema site, which secrete a factor that breaks down histamine and the anaphylactic responses become less severe
What does the release of leukotriene C do?
Induces contraction of smooth muscles, but at a slower rate than histamine
Where do lymphocytes originate from?
Lymphoid stem cells of the bone marrow
What are the two types of lymphocytes?
B and T cells
B cells
Originate and differentiate in the bone marrow
Differentiate into plasma cells
Called for humoral immune responses (antibodies)
5-15% of blood lymphocytes
T cells
Originate in the bone marrow but differentiate in the thymus
Secrete cytokines
Call for cell-mediated immune repsonse
80-90% of blood circulating lymphocytes
What do cytokines do?
Attack foreign cells directly
What are the subtypes of T cells
Helper, supressor and killer
When do B and T cells increase?
They increase in number in viral infection , surgical transplantation and leukemia
Null cells
Type of lymphocyte
Lack surface receptors characteristics for T and B cells
Have cytotoxic activity against tumor cells
Where are plasma cells found?
Sites of chronic inflammation
Sites of high risk of invasion (lamina propria of the intestinal and respiratory tracts)
Plasma cells
Antibody producing cells that arise from activated B lymphocytes
Humoral immunity
Nuclear chromatin pattern, basophilic cytoplasms
Aggregates the RER
Neutrophils
Originate in bone marrow
Multi-lobed, cytoplasm rich in lysosomes
Phagocytic
Number increase in bacterial infection
Where do neutrophils go?
Circulate in the blood, the migrate to the CT and don’t re-circulate after leaving the blood (CT is the action site and graveyard)
Which cell is the first line of defense?
Neutrophils
Eosinophils
Bilobed nucleus, cytoplasm contains eosinophilic granules
Mildy phagocytic
Phagocytose antigen-antibody complexes
When do eosinophil number increase?
Parasitic infestations and allergic reactions
What is the role of eosinophils?
To cleave histamine and moderate the allergic reaction
Pericytes
Undifferentiated stem cells located adjacently to the basal lamina of capillaries
Branched with flattened nuclei
Collagen
Made of protein tropocollagen and polypeptide chains
Tough, flexible, resists stretching
Most abundant fiber in the body
Form wavy bundles and stain eosinophilic with H&E
Extracellular
Type I collagen fiber
Most abundant and strongest
Consists of bundles of fibers
Eosinophilic
Present in skin, tendons bone and dentin
Type II collagen fiber
Loose aggregates of fibrils
Present in hyaline cartilage and vitreous body
Type III collagen fiber
Thin reticular (argyrophilic) fibers
Present in skin, blood vessels and lymphoid tissue
Type IV collagen fibers
Invisible
Amorphous
Detected by special stains
Present in the basement membrane
Assembly of Fibrillar Collagens
After secretion, they assemble into collagen fibrils
Then the collagen fibrils aggregate into collagen fibers
Reticular Fibers
Thin type III collagen fibers coated with glycoprotein
They form a sponge-like framework around parenchymal organs (spleen, kidney, uterus, liver lymph nodes)
Stained with PAS and black with silver stain
What is another name for reticular fibers?
Argyrophilic fibers
Elastic Fibers
Branch, made of elastin protein
Stretch and recoiling abilities
Stained with Van Gieson or Weigert’s elastic
Found in arteries, trachea, vocal cords, ligamentum nuchae, auricular cartilage, skin
Yellow fibers
Fresh elastic fibers that are yellowish
Ground Substance
Featureless substance occupying in life empty spaces appearing in tissue sections
Composed of GAG, proteoglycans and glycoproteins
Glycoaminoglycan (GAG)
Composed of large polysaccharide molecules
Negatively charged
Attract sodium and potassium
Absorb and retain water
What is GAGs important role?
Regulating water and electrolyte balance
Examples of GAGs
Chondroitin sulfate abundant in blood vessels, cartilage and bone
Heparin
Hyaluronic acid
Proteoglycans
Consists of a core protein where GAGs extend
It’s attached to hyaluronic acid, forming a large molecule, then slows the spread of organisms through the tissue to help hold cells together
Glycoproteins
Protein-carbohydrate complex that bind plasma membrane to collagen and protoglycans outside the cell
What is the function of glycoproteins
They bind all the components of a tissue together and make pathways that guide embryonic cells to migrate their destination in a tissue
How does loose irregular CT compare to dense CT
Fewer fibers, more cells, more vascular, more abundant and less resistance to stress than dense CT
Dense Irregular CT
Primarily of fibroblasts, thick and densely packed collagen fibers
Collagen fibers exhibit random orientation and provide strong tissue support
In areas where resistance to forces from different direction is needed
Dermis
Dense Regular CT
Densely packed with regular parallel orientation
Predominant cell: fibroblast
In tendons and ligaments that are attached to bones
How does dense regular CT compare to dense irregular CT
Fewer cells, fewer vessels, more densely arranged fibers than dense irregular CT
EX: tendons
Mucous CT
Loose CT composed of fibroblasts with several long cytoplasmic processes
Intercellular space is filled with jelly-like amorphous ground substance rich in hyaluronic acid and fibers
Type 1 collagen
EX: umbilical cord
Mesenchymal CT
Gel-like amorphous matrix containing mesenchymal cells and a few reticular fibers
Present in the umbilical cord and embryos
Elastic CT
Branching elastic fibers with few collagen fibers
Present in lungs, external ear, glottis, ligamentum nuchae and large blood vessels
Reticular CT
Branched reticular fibers
Present in the bone marrow, lymphoid organs, surrounding liver sinusoids and smooth muscle cells
Adipocytes
CT cells that store fat and produce a variety of hormones
Differenciate from mesenchymal cells and accumulate fat in their cytoplasm
White adipose tissue
Unilocular adipose cells
All of the adipose tissue found in adults throughout the body
Stained with H&E
Function: store fat
Brown adipose tissue
Multi-ocular adipose cells
Oxidizes fatty acids 20 times faster than white fat
Found in hibernating animals, infants
Function: Produce heat
What are the 2 forces that act on the capillary wall?
Hydrostatic Pressure
Colloid Osmotic Pressure
Hydrostatic Pressure
Generated by pumping action of the heart
Forces fluid out of the capillary wall
Colloid Osmotic Pressure
Results mianly from blood plasma proteins
Draws water back into the capillaries
When does water move out at the arterial end of the capillary?
Because HP is greater than COP (blood pressure is higher)
When does fluid move back at the venous end of the capillary
When COP is higher than HP because the luminal diameter of the capillary and the concentration of proteins increases
What leads to edema?
Increased blood pressure –> increased fluid
What results in the accumulation of fluid in the tissue?
The blockage of lymph vessels due to pressure or parasites and decreased tone in the values of lymph vessels
Extracellular matrix
Major component of CT
Made of protein fibers, ground substance and interstitial fluid
Myo-fibroblast
Modified fibroblasts
Bundles of actin filaments
Abundant in areas of wound healing
Leukocytes
Migrates from blood vessels to the CT, to sites of injury or inflammation
Types: Lymphocytes, neutrophils, basophils
Basophils
Lobed nucleus
Less than 1% in blood
Metachromatic granules that contain heparin and histamine
Has IgE receptors
Fibroblast Structure
Spindle-shaped, elongated, many cell processes
Oval, pale staining regular nuclei, prominent nucleoli.
Where may epithelioid cell granuloma occur?
at sites of intense inflammation
