Connective Tissue Flashcards
What is the extra cellular matrix (ECM) composed of?
structural fibers
fibrous proteins
Ground substance
What is the epimysium?
prominent and thick outer covering of muscles
- type of deep fascia
What are 5 examples of connective tissue?
- epimysium
- ligaments
- tendons
- capsules
- cartilage
- bone
- superficial fascia
- deep fascia
What are 3 functions of connective tissue?
- mechanical strength/ support for specialized tissues in organs
- Conduct and control exhange of nutrients, metabolites and signaling ligands
- different cell types in an organ
- cell types and blood vessels - Control behavior and function of cells in contact with ECM
- polarization and shape of epithelia
- guidance/ regulation of cell migration thru matrix
- proliferation, metabolism, differentiation
- defense against infection
- tissue formation, organization, modification
- inflammation, repair due to injury
What are the two types of cells in the ECM?
Core resident cells of CT family
Immigrant blood derived cells (mostly WBCs)
What are the 7 types of core cells of the ECM and what are their functions?
- Mesenchymal
- precursors of all connective tissue
- embryogenesis & adult stem cells - Fibroblasts
- most common in CT - Myofibroblasts
- from fibroblasts
- contractile function - Adipocytes
- store fat as energy - Osteoblasts & osteocytes
- make bone - Chondrocytes
- make cartilage - SOME smooth muscle
- walls of blood vessels
- can synthesize and secrete ECM components
- wound healing
What are 5 types of immigrant blood derived cells and what are their functions?
- Lymphocytes
- acquired immunity - Macrophage
- engulfing/ phagocytosing cells
- secrete and respond to many extra cellular signals - Neutrophils and eosinophils
- defense against microorganisms - Mast cells
- secretory
- promote swelling, allergic reactions - Osteoclasts
- phagocytic: bone reabsorption and remodeling
Name 3 functions of macrophages
- angiogenesis
- immune cell migration/ function
- fibroblast activation
- blood vessel permeability
- remodel damaged tissues
- remodel developing tissue/ organs
How do fibroblasts respond to tissue injury?
proliferate
severe injury: scar tissue = hypertrophy of fibroblast dependent connective tissue
How do fibroblasts contribute to the ECM?
several types
- responsible for enormous variation in ECM structure/ function
- IDd by immunohistological methods
Where do mesenchymal stem cells originate? What type of cells do they produce?
Bone marrow
NOT hematopoietic -> primary precursors of CT cells
Describe the structure and function of collagen. Why is it so diverse?
most abundant 3 intertwined polypeptide chains =>rigid triple helix (alpha chain) - 25 different alpha chains - 17 multimeric collagen types
How does fibrillar collagen assemble?
align head to tail in large bundles => fibrils
- stack bundles -> thickness
- strength
- resistance to tensile forces
- Banding pattern
MOST ABUNDANT (especially type I)
What type of collagen links fibrils together, and links collagen fibers to other tissues?
Fibril associated collagen
What does network-forming collagen do?
form thin fibers -> assemble as interlaced fibers -> form porous sheets
- found in basal laminae
- form filtration barriers
- Type IV
What are some important properties of ligaments and tendons?
- collagen arranged in parallel organized sheets
- resist strong shear forces
What are some of the intracellular modifications of collagen?
- synthesized on ER -> translocated to ER lumen
- glycosylated and hydroxylated
- assembled into triple helix
What are some of the extracellular modifications of collagen?
- form bundles & end to end polymers
- enzymes catalyze covalent cross links to increase tensile strength of bundles
N and C terminus cleaved by specific proteases
N -> N-telo peptides
- clinically important: levels (urine & blood) diagnose connective tissue/ bone disease
Describe elastic fibers: where are they found? What are they made of? etc.
Found in CT that must distend/ be resilient
Made of elastin and fibrilin
- elastin: usually random coil conformation, secreted by fibroblasts
- form extracelluar sheets that are highly crosslinked => extensive network
elastin network + fibrilin (organizer)
=> blend within other ECM elements
- stretch and recoil like rubber band
What is the ground substance of the ECM made of?
proteoglycans
secreted proteins and glycoproteins
inorganic and small organic solutes (ions, carbohydrates, lipid vesicles, non-protein signaling ligands)
water
What are proteoglycans?
Protein core + large acidic polysaccharides (GAGs)
- highly negatively charged => hydrophilic
- rigid exteded structure => readily form gels
- can bind and activate or inactivate other proteins
- function as selective sieves (pores of various sizes)
Hydration facilitates:
- diffusion
- high swelling (turgor)- resist compression - knee
What is the sequence of events following a wound/ injury in the context of connective tissue?
- Inflamation & blood clotting
- New tissue formation
- Tissue remodeling
What happens during the inflammation and blood clotting response?
- blood platelets released from CT- temp. seal on wound
- water permeability increased -> swelling
- increased permeability to monocytes -> immune
- WBC attracted/ migrate to site
- Histamine- permeability of endothelia
- cytokines-> stimulate WBC production
What happens during the new tissue formation phase?
- firbroblasts divide -> secrete ECM components
- epithelial stem cells divide
- signals for angiogenesis, repair
What happens during the tissue remodeling phase?
Cell composition, CT and epithelia altered depending on severity of wound
- remodeling may be imperfect => disorganized epithelia/ CT
