General connective tissue L4 Flashcards
What are the functions of connective tissue? HINT THERE ARE 5
Structural framework, transports fluids and dissolved materials, stores lipids, protects organs and defends the body from pathogens
General connective tissue can be split up into what 3 categories?
Cells, fibres and ground susbtance
What is ground substance?
Ground substance fills the spaces between cells and fibers. It is a gel like extracellular matrix that adds strength and stiffness. It also delays the spread of infection
What does ground substance contain?
Water and salts
Glycosaminoglycans (GAGs)
Proteoglycan molecules
What are GAGs - Glycosaminoglycans?
Polysaccharides, made up of sugars
What do Proteoglycan molecules do?
They bind to water giving a gelatinous property to the matrix. They also form aggregates to make up ground substance.
What does ground substance seem to be in preparations?
In preparations, ground substance seems to be structureless and stains metachromatically with toluidine blue
What are the commonest GAGs?
Hyaluronate, chondroitin-4-sulphate, chondroitin-6-sulphate, dermatan sulphate, heparin sulphate and keratan sulphate
What is the predominant GAG?
Hyaluronate - hyaluronic acid and it is important because the viscosity of ground substance depends on the content of it
What is the ground substance elaborated by?
By the endoplasmic reticulum of connective tissue cells, especially of fibroblasts
Connective tissue components:
Cells and fibres in a matrix
Cells in connective tissue?
Mesenchymal cells, fibroblasts, adipocytes (fat cells), immune cells
What are the immune cells in connective tissue?
Macrophages/monocyte, mast cells, B cells/plasma cells and lymphocytes
What fibres are in connective tissue?
Collagen and elastin
Is there one ancestor of connective tissue cells?
Yes there is one ancestor - mesenchymal stem cells
What are the 7 cells of connective tissue?
Mesenchymal stem cells (MSCs)
Fibroblasts
Adipocytes (fat cells)
Macrophages (Histiocytes)
Mast cells
B cells/ Plasma cells
T cells
What is the basic function of mesenchymal stem cells (MSCs)?
Differentiate into other cells
What is the basic function of fibroblasts?
Make extracellular matrix, wound healing
What is the basic function of adipocytes (fat cells)?
Stores and metabolises fat
What is the basic function of macrophages (Histiocytes)?
Phagocytic, innate immune cell
What is the basic function of mast cells?
Histamine reactions, innate immune cells
What is the basic function of B cells/Plasma cells?
Make antibodies, adaptive immune cell
What is the basic function of T cells?
Major immune cell, adaptive immune cell
Are MSCs multipotent?
Yes
Can MSCs differentiate into all other cells found in connective tissue?
Yes
Where are MSCs obtained from?
Bone Marrow
Can MSCs act as a potential use for cell replacement therapy?
Yes
What is the most abundant cell in connective tissue?
Fibroblasts
Can fibroblasts differentiate into different cells?
Yes
What do Fibroblasts make?
Extracellular matrix, i.e. secrete components: GAGs, collagen, elastin, ground substance
What immune response do fibroblasts play a role in?
They have a role in wound healing i.e. they secret collagenous matrix (scar tissue)
Where do adipocytes develop from?
Fibroblasts
Can mature adipocytes divide?
NO
What do fat cells do? hint 5
They support and protect organs
They store and metabolise fat (lipid)
They insulate (slow heat loss)
What do white adipose cells do?
They store energy.
Role: insulation, shock absorption
What do brown adipose cells do?
They heat the body
Role: Stores energy in fat
What are the 3 places where the birth of a macrophage happens?
Bone marrow, Blood, Tissue
5 steps within cells to birth of a macrophage:
stem cell -> monoblast->monocyte->macrophage->activated macrophage
Are macrophages phagocytic?
Yes
Do macrophages scavenge foreign materials?
Yes bacteria, debris, etc
What else can macrophages be called?
Monocytes and histiocytes
What immune system are macrophages apart of?
The innate immune system
Where are fixed macrophages found at?
Strategic points
What do macrophages have for degradation?
They have lysosomes for degradation
What are 6 places where fixed macrophages are found?
- Dust/Alveolar type (lungs)
- Histiocytes (connective tissue)
- Kupffer cells (liver)
- Microglial cells (nervous)
- Osteoclasts (bone)
- Sinusoidal lining cells (spleen)
What do macrophages do in order to respond to pathogens?
They present pathogen antigens at their cell surface
to T cells (elicit an adaptive immune response)
What 3 disorders are associated with macrophages:
Granuloma, Macrophage Activation Syndrome, and
Multicentric reticulohistiocytosis
What are leprosy and TB resistant to?
They are resistant to lysosomal degradation
What was the plague pathogen resistant to?
Phagocytosis
Where does HIV virus replication occur?
In macrophages
What do macrophages do in infected throat cells?
They destroy influenza
Do macrophages play a role in atherosclerotic deposits?
Yes
Do macrophages play a role in atherosclerotic deposits?
Yes
What do macrophages release with tumour cell proliferation?
They release growth factors
