Connective tissue Flashcards
What are the 2 sublayers of connective tissue in the dermis?
Papillary layer → Loose CT
- More apical
Reticular layer → dense irregular CT
What defines Loose vs Dense CT?
Loose → more cells than fibers
Dense → more fibers than cells
What defines Regular vs Irregular CT?
*Both are subclasses of dense CT bc loose CT doesn’t have enough fibers to qualify them
Regular → regular/organized patterning of the fibers (ex: tendons)
Irregular → fibers are not running in a specific order/direction
Why is CT important for the epitheliums around it?
In the case of the dermis, is supports the epidermis
Carries nerves and blood vessels that provide innervation and blood supply to the epidermis and other epithelia
CT proides support and connecting framework to other tissues of the body
Give 2 examples of supporting CT. What makes them supportive?
Cartilage
Bone
→ produce extracellular matric with firm consistency
- Allows tissue to support mechanical stress without distortion + provide support to adjacent soft tissues
Give an example of CT with special properties.
Hematopoietic-bone marrow
*It is CT because of where it derived from
Where does ALL connective tissue originate from?
From mesenchymal cells in the mesoderm of the embryonic cells
Mesenchymal cells are pluripotent stem cells
- They are in Euchromatin state → expansion, DNA transcription, cell dividing, making protein, very active
What different CT tissue cells can mesenchymal cells differentiate into?
Lipoblasts, Chondroblasts, Osteoblasts → active/euchromatin state → secrete collagen and other elements of ECM
Mast cells, Macrophages, lymphocytes, Plasma cells → immun function
Adipocytes → store fat
What is the role of fibroblasts, what can they differentiate in?
Fibroblasts → some euchromatin, some heterochromatin → still very active cells → make ECM components, collagen, glycoproteins, proteoglycans
can divide into 2 fibroblasts or differentiate into fibrocyte
What are the characteristics of fibrocytes/lipocytes/chondrocytes?
Heterochromatin → dormant state, no transcription
- Can still divide → isogenic groups
- Found/embedded in ECM
What is special about wound healing?
It is the only situation in which fibrocytes can de-differentiate into fibroblasts to become active again
How is connective tissue different from epithelial tissue?
The epithelial tissue has little to no extracellular space
CT has lots of extracellular space → cells scattered within ECM
→ Cells are not directly attached to one another (unlike epithelial cells), they are separated by ECM
Also, CT is derived from mesenchyme unlike epithelial tissue which is derived from ectoderm and endoderm
What is the connective tissue matrix composed of?
Ground substance and fibers
What is ground substance? (In general, bone and blood)
In ordinary CT → ground substance = water, stabilized by GAGs, proteoglycans, glycoproteins
*GAGs hold water as they are negatively charged
In bone → ground substance includes minerals
In blood → plasma (plasma is considered to be part of ECM)
How the ECM produced?
Produced by fibroblasts (or other related cells type → chondroblasts in cartilage, osteoblasts in bones)
What are the 2 main types of fibers in the ECM?
Principal fiber type = Collagen → most abundant protein in the body →confers tensile strength with flexibility
Elastic fibers confer resilience (only non collagen fiber)
What tissue is Collagen Type I found in?
Dermis
Tendon