BIOMED 10/16b CT Histology Flashcards
Roles of Connective tissue
- maintains/supports structure (dermal layer) - extensive amount of communication (mechanobiology) that allows it to respond through gap junctions
- mediates exchange of metabolites, waste, etc. - into and out of it and through it
- immune response, inflammation, and tissue repair
classifications of connective tissue?
- CT proper
- Loose (areolar)
- Dense (irregular and regular) - Specialized CT
what is loose CT proper?
- most abundant CT in the body, bundles in two types of tissues
- sparse fibers
- increased cells and ground substance
- vehicle by which blood vessels, nerves and lymph get to the target tissue
- allows space for things to travel into, through, and out of
- has elastin and collagen, but not as much as the gel-like ground substance
major functions of loose CT
- allow for space for things to travel where they need to go
- space packing, occupying materials, shock absorbers
what does loose CT have the most of?
ground substance and cells
what are two types of dense connective tissue?
- irregular
2. regular
what is dense irregular connective tissue?
- dermal layer of the skin
- withstands tension from different directions
- has the presence of elastic fibers
- responsive in any direction of stress
- densely packed with collagen, not arranged in parallel bundles
- sheaths around tendons and nerves
what kind of tissue is the dermal layer of the skin?
dense irregular connective tissue
what is the main purpose of dense irregular connective tissue?
withstand tension from different directions
what kind of bundles does dense irregular tissue form and what’s its purpose?
- densely packed with collagen
- not arranged in parallel bundles
- sheaths around the tendons and nerves are for protection so they can withstand stresses from various forces
what is dense regular connective tissue?
- collagen is bundled and in parallel arrangement
- only resist tension that’s built in its direction
- has ability to relay and respond to tensile stress
- found in ligaments, muscles, and aponeurosis (sheets layered in multiple directions)
can dense regular connective tissue withstand stress in any direction?
NO!
- it can only resist tension that’s built in it’s direction
- parallel bundles
what are some examples of specialized connective tissue?
- adipose - modified loose CT
- cartilage
- bone
- hematopoetic tissue (bone marrow)
what are the components of CT proper?
- ECM (fibers are functional part of ECM)
2. Cells (resident vs visiting)
two major components of ECM
- ground substance - largely proteoglycans
2. fibrous proteins - embedded throughout the ground substance
what is the purpose of proteogolycans in ground substance of CT proper
attract water to create a hydrated gel
what does the ECM dictate?
- amount of water
- types of fibers produced
- amounts of fibers produced
how will ECM vary?
it depends on the actual type o CT
- tendon is type I collagen and basically no ground substance
- -> lined up in parallel bundles, because it reacts to tensile stress
what is the ground substance made of
- GAGs - glycosaminoglycans
2. Structural Glycoproteins
what are GAGs
- collections of long chain sugars/polysaccharides (same as proteoglycans)
- highly negatively charged (can attract water)
- gel/mousse like substance
when will you have more watery GAGs
depends on the function
-Loose connective tissue has a much higher degree of water than a tendon
what is the purpose of structural glycoproteins in ground substance?
- BINDING proteins
- bind fibers to the ground substance
- bind fibroblasts (cells) to fibers
- the way things from the external surface get relayed to the nucleus
what are some examples of structural glycoproteins?
fibronectin
fibrillin
most common fibers in CT proper components
- collagen
2. elastin
what are the most important types of collagen that we need to know?
- Collagen Type I
- Collagen Type II
- Collagen Type III
- Collagen Type VI
what is the importance of type I collagen?
- it is the most common type of collagen in the body
- used in bone, ligaments, tendon, fascia, joint capsules, etc
- arrangment is made for funcion
- produced in large quantities to resist tensile stresses (stretching)
how is type I collagen arranged?
- grouped in bundles, cross liked structure makes it exceptionally strong and resilient to tensile forces
- FETTUCCINE
- high degree of organization helps it resist tensile stresses very well
what connects fibrils to form one collagen fiber?
several fibrils are put together to form one collagen fiber, cross linked by glycoproteins (fibronectin)
fibers form in the direction they are pulled on (T/F)?
TRUE - arrangement is formed in the direction it’s pulled on
is skin arranged in parallel orientation?
NO - needs to be able to withstand all different directions of stress
Type II collagen fibers are created for what parts of the body?
- hyaline cartilage
2. elastic cartilage
what is the structure and function of type II collagen?
- not arranged in parallel bundles
- don’t have a regular appearance
- more ground substance
- more cellular
what does collagen type II look like?
feathery!
what is the significance behind the structure of type II collagen fibers?
- since the structure isn’t super organized, it is more deformable
- allows to change shape depending on compressive stress pushed on it
- allows for recoil
what are type III collagen fibers
- reticular fibers
- mesh-like structure
- back bone for bone marrow, lymph tissue, BVs, immature wound beds
what is the arrangement of type III collagen fibers?
branching in a mesh-like structure where they support the tissues that need them
what is the significance of type IV fibers
- simple cuboidal epithelial tissue basement membrane
- Purposes:
1. support
2. filtering (safety feature)
Elastic fiber composition
- elastin
2. fibrulin (binding protein)
where are elastic fibers found and what is their function?
- found in loose connective tissue with collagen fibers
- structure:
- very thin and ropelike
- not bundled
- sit slightly in parallel - function: allow tissue to be stretched and to regain original strength
what tissues are elastic fibers found in?
lungs
BVs
skin
ligaments
relaxed vs stretched elastic fibers
relaxed: very wavy and close together like loose cooked spaghetti
stressed: pulled apart in parallel almost
function of fibrillin
keeps components of elastic fibers together
components of elastic fibers
- elastin
2. fibrillin
different cells of CT proper?
- resident
2. visiting
what are the resident cells of CT proper?
live in tissue full time
what are the different types of resident cells in CT proper?
- fibroblasts - if active, produce everything: ground substance, fibers, etc
- mesenchymal cells - stem cells aka pericyte - immature or precursor fibroblast
where are mesenchymal resident cells usually found?
they are stem cells that are precursors for fibroblasts and they are normally found where growth, exercuse, and anything that needs building are
what are visiting cells of CT proper?
pop in and out and across CT layers, all come from bone marrow; produced else where and travel in the tissue
three buckets of visiting cells of CT proper?
- macrophages
- mast cells
- plasma cells
what are macrophages?
phagocytic visiting CT proper cells that help clean up dead or necrotic tissue
- present antigens to lymph tissue
- produce inflammatory mediators (cytokines)
what are mast cells?
- visiting ct proper cells that are found within CT or can travel into and out of CT
- inflammatory mediators
- secrete vasoactive substances that allow capillaries to become really leaky
- mediate edema
what are the plasma cells of visiting CT proper?
- they are essentially lymphocytes that become activated
- they produce antibodies (immunoglobulin)
- they are B-lymphocytes
what determines that properties of each type of CT?
- the amount of water within the CT
- the types of fibers
- the amounts of each of those fibers
- composition goes hand in hand with the type of CT
Loose connective tissue properties
- most abundant
- connects two different bundles of the same type of tissue
- layer that has BVs travel through it to provide nutrients to different cell types
- sparse fibers (reticular, elastic, collagen)
different kinds of fibers in loose CT?
reticular
elastic
collagen
functions of loose CT proper?
- space for things to travel where the need to go to - out of, into, through
- space packing/occupying material - shock absorbers
Pathology of CT fibers
- disorders of elastic fibers (fibrillin)
2. disorders of collagen
disorders to elastic fibers
- can be damaged by UV light
- loss of elastin in respiratory system causes emphysema
how does emphysema happen?
Alveolar walls are filled with elastic fibers abundantly and every time you exhale alveoli recoil, BUT with emphysema, the air becomes trapped and there is no elastic recoil (dead space, blebs = non functional alveoli)
what is ehlers danlos syndrome?
- 10 clinical variations
- autosomal dominant, recessive, x-linked
- collagen defect
- lacks tensile strength
- defect in synthesis and assembly of collagen
- Sx: joint hypermobility, large joint dislocation, and skin hyperelasticity
what is the beighton scale?
10 point
point for every hypermobile aspect that you have
what is osteogenesis imperfecta?
- collagen Type I disorder
- 1/20,000 incidences
- autosomal dominant and spontaneous mutation
- wide range of clinical manifestations
- increase fracture incidence
