Connective Tissues Flashcards
What is connective tissue?
A type of tissue that fills the gap between other tissues or organs and helps to hold them together and provide support
What are the characteristics of connective tissue?
- It ranges from avascular (meaning less blood vessels) to highly vascular (more blood vessels)
- There is an extensive extracellular matrix that separates the cell
- It is found throughout the body
Is muscle considered a connective tissue?
No!!
True or False: Tendons, the perimysium, the epimysium, the endomysium are considered as some kind of connective tissues.
True! (Definitions of these terms are in the muscle structure section)
What are the functions of connective tissue?
Physical and functional properties vary, but
1) They support, surround, and interconnect other tissues
2) They establish structural framework
3) They form sheaths around the body organs and protect delicate organs
4) They store energy reserves
5) They transport fluids within the body
What are the components of connective tissues?
Think of noodle soup!
1) Cells (carrots)
2) Protein fibers (noodles)
3) Ground Substance (broth)
4) Extracellular matrix (everything outside of the carrots (cells) - includes protein fibers and ground substance)
What kind of cells are within the component of cells(carrots) in connective tissue?
1) Fibroblasts - main type
2) Macrophages - main type
3) Mesenchymal cells
4) Adipocytes
5) Other cells - mast cells and lymphocytes
What do fibroblasts do in the connective tissue?
- They make and secrete proteins for extracellular fibers
- They secrete hyaluronic acid (HA)
- They are the most abundant fixed cells (don’t change much & always there) in connective tissue proper
What are macrophages in connective tissue?
They are immune cells that are “fixed” and “wandering” - meaning they find something to attack the infection
What is the ground substance component in connective tissue?
Ground Substance = fluid-like or gel-like substance that fills space between cells and fibers
What are the characteristics of ground substance and what does it contain?
1) It contains proteoglycans (“GAGs” - big proteins) and macromolecules, a linear core protein with many glycosaminoglycans attached.
2) It is negatively charged
3) It is hydrophilic
True or False: Chondroitin sulfate and hyaluronic acid (HA) are also GAGs
True!
Name the different types of connective tissue fibers!
1) Collagen
2) Elastic Fibers
3) Reticular
What is collagen?
- Collagen is the strongest and most abundant type of connective tissue fiber.
- Also provides high tensile strength
- It is the most abundant protein in the body (20-30% of protein)
What is Elastic Fibers?
- Elastic fibers are networks of long, thin, elastin fibers that allow for stretch and recoil
What is Reticular connective tissue fibers?
- Reticular are short, fine, and highly branched collagenous fibers that form networks
Collagen is the main protein in….
Tendons, bone, and cartilage
Is it true that collagen is strong and flexible and not inelastic?
No! Collagen is strong and flexible, but is inelastic.
Where else is collagen present in?
Also present in connective tissue sheaths in muscle
True or False: There are different amino acid sequences for different types of collagen, and that affects strength and functionality.
True!
Describe the FIRST step of the formation of collagen fibers.
1) We begin at the alpha chains, and proceed with hydroxylation of lysine and proline by lysyl hydroxylase and prolyl hydroxylase to form pre-procollagen.
Describe the SECOND step of the formation of collagen fibers.
2) Once pre-procollagen is formed, there is a helix formation that mixes together to form procollagen.
Describe the THIRD step of the formation of collagen fibers.
3) Once procollagen is formed, it is then exported from the fibroblast cell into the extracellular matrix. IT IS STILL PROCOLLAGEN DURING THIS STEP. It just moving to a different location.
Describe the FOURTH step of the formation of collagen fibers.
4) Once the procollagen has been exported, the ends of the procollagen are removed and then becomes tropocollagen.
Describe the FIFTH step of the formation of collagen fibers.
5) Once tropocollagen is formed, the tropocollagen molecules align longitudinally, and then lysyl oxidase contributes to cross-link formation and forms the collagen fibril.
Describe the SIXTH step of the formation of collagen fibers.
6) Once the collagen fibril is formed, the maturation of cross-links increases the stability and it becomes insoluble. (In previous steps, everything is soluble). Finally, the collagen fiber (contains multiple collagen fibrils) is formed!
What is elastin?
It is a major protein that contributes to fiber.
What are the characteristics of elastin?
1) Can be reversibly stretched (to nearly 2x length).
2) There is high content of non-polar amino acids - hydrophobic!
3) Cross-links indicate elastin fiber maturation.
What are some examples of elastin?
Blood vessels, ligaments, and skin
What are the characteristics of reticular fibers?
1) It contains type III collagen
2) It has a branching, interwoven network
3) They are small, fine, and delicate (fragile)
4) They create an internal framework in glands and lymph nodes, and in connective tissue surrounding soft organs.
What are the three types of connective tissue and what do they include?
1) Proper Connective Tissue ( includes loose and dense connective tissue)
2) Supportive Connective Tissue (includes bone and cartilage)
3) Fluid (includes blood)
What is loose connective tissue?
It’s like “packing material” - it fills in the space between organs and provides cushioning.
What is the composition of loose connective tissue?
1) High proportion of ground substance
2) They have relatively few collagen and elastin fibers
3) They are fairly resilient and can distort and stretch without damage
4) They have a wide variety of cell types
What are the functions of loose connective tissue?
1) Separates skin from deeper structures
2) Surrounds and supports blood vessels and nerves
3) Binds organs together
4) Provides a route for diffusion of materials - ex: vaccines being put into your body
What is dense connective tissue?
1) It is the structure that provides more strength but less connective flexibility
2) There are more numerous fibers and fewer cells
What are the two types of dense connective tissue?
Dense regular and dense irregular!
What is dense regular connective tissue? Give me examples of where dense regular connective tissue could be.
1) It is a mixture of collagen, elastin, and reticular fibers.
2) The fibers align in ONE direction.
3) EX: Tendons, ligaments, aponeuroses, and elastic tissue
What is dense irregular connective tissue? Give me examples of where dense irregular connective tissue could be.
1) It is dense, interwoven, randomly arranged fibers.
2) They have a high amount of collagen
3) EX: Dermis of skin, bone sheaths, nerve and muscle sheaths, and capsules around visceral organs.
What are the functions of dense regular connective tissue?
1) Binds bones together and attaches muscle to bone
What are the functions of dense irregular connective tissue?
Toughness! It protects organs from injury
