Introduction to connective tissues Flashcards
Two components of connective tissue
Cells and intracellular materials
Cells found in connective tissue
Fibroblasts
Chondrocytes
Osteocytes
Osteoblasts
Intercellular materials three categories
Fibres, matrix proteoglycans and glycoproteins
Fibres in connective tissue
Collagen and elastic
Matrix proteoglycans in CT
aggrecan, versican, biglycan, decorin, hyaluronan
Glycoproteins in CT
Fibrinectin, osteonectin, laminin
What is a proteoglycan
Proteins and carbohydrates joined together. Differs from a glycoprotein as there is more carbohydrate in proteoglycans in relation to its protein content, in glycoproteins there is more protein in relation to carbohydrate.
Why are tendons white?
Because the have a reduced blood supply. Few capillaries. The CT of tendons don’t turn over frequently.
Describe the structure of tendons and ligaments
Closely pack parallel bundles of collagen fibres, with intervening rows of often elongated fibroblasts, sparse capillary network. Contains some elastic fibres which may be more prominent in ligaments.
What is a fibroblast
A CT cell that produces collagen and other fibres
What is an essential feature of collagen molecules (found in tendons and ligaments)
Ability to withstand tension i.e. there is minimal elongation.
What happens if tension is removed from a tendon?
Very quickly the collagen fibres become less aligned, cells become rounded and there is an increase in proteoglycan content. When there is tension the fibroblast don’t divide. When tension is removed the cells begin to divide
Why do tendons become ‘puffy’ when there is a loss of tension?
Because there is an increase in proteoglycan content which binds water.
What is a tenocytes
An elongated fibroblast type cell
What happens to a tenacity when it is no longer under tension
Becomes a chondrocyte (cartilage forming cell also make collagen but more proteoglycan)
Three types of cartilage
Hyaline
Fibrocartilage
Elastic cartilage
Where is hyaline cartilage mainly found and what is its other name
Mainly in joints and called articular cartilage (because joints articulate)
What is the proteoglycan content of articular cartilage
High-10% of dry weight
Why is cartilage so good under pressure
Due to the aggrecan (a proteoglycan) molecules. These have a protein core with glycosaminoglycan side chains. The GAG side chain is negatively charged so proteoglycans repel each other resisting compressional force. H20 molecules also surround GAGs helping to withstand compressional force
How are the proteoglycan molecules held in position (so they don’t squish out to the sides of joints)
With carbohydrate chains called hyaluronan. There are also collagen fibres which run parallel to the proteoglycans attaching with their positively charged amino acids to the negatively charged GAGS
What is proteoglycan content in articular cartilage directly related to
Effectiveness of the joint to withstanding load. More PG better support.
What happens if you take the pressure of the joint (in relation to PG content)
Nothing as long as you keep the joint moving
Define anisotropic
Stretches more in one direction than other directions
Define langers lines
The lines of maximum tension in the skin
Layers of the skin
Epidermis- stratum corneum, stratum lucidum, sratum granulosm, stratum spinosum, stratum germinativum.
Basal lamina
Dermis- papillary layer, reticular layer.
Subcutaneous layer or hypodermis
Investing fascia
What layer of the skin do scars form
Reticular layer
What is the make up of the reticular layer
Basket weave of collagen
How do scars form
When there is a tensional force pulling a wound apart collagen bands form in the reticular layer. This occurs when the wound is not in parallel with the langers lines (line of maximum tension)
