Connective Tissue and Collagen.

Some simple notes (to maintain my sanity). There's much more information out there if you are willing to go down the rabbit hole of research and I would love to hear if anyone has thoughts to add.

Connective tissue is a bodywide web of fibrous tissue, consisting of mostly collagen fibres, in varying amounts and arrangements. (Collagen is the most abundant protein in the human body.)

There are many types of connective tissue, and the classification depends on the composition of the tissue - the structure, amount organisation of the fibres and location of the tissue. The differentiation and delineation between different types of connective tissues isn't always clear and one type often merges into another form as part of the body-web of connective tissue. I include the extracellular matrix (see below) in my thoughts.

The broad classification categories for connective tissue are:

• Dense or loose. i.e. solid or soft. Depending on the amount and type of collagen.
• Regular or irregular i.e. the arrangement of the fibres is 'regular' - in parallel or more 'irregular' random looking.

Specialised connective tissue includes tendons, ligaments, aponeuroses, cartilage, fascia, bone, teeth, meninges, pleura, peritoneum, pericardium etc.

The linea alba, nuchal and supraspinous ligaments - our midline linear guides for alignment - are connective tissue.

Loose and dense irregular connective tissue is mostly found in the layers of the dermis (skin) apidose (fatty) tissue - surrounding and enveloping the rest of the body.

Connective tissue runs through and surrounds our muscles, suspends our internal organs and wraps around individual cells forming a vast web-like network on smaller and smaller scales throughout the whole of our body.

For example, connective tissue runs through and around every muscle:

• Every single muscle fibre (muscle cell also known as a myocyte) is surrounded by connective tissue called the endomysium.
• Muscle fibres are grouped into bundles surrounded by more connective tissue called the perimysium.
• Then the whole muscle is surrounded by even more connective tissue called the epimysium.

i.e. There is a lot of connective tissue that runs through and around every muscle.

And bone:

• Bones are surrounded by a membrane of dense irregular connective tissue called periosteum.
• Bone matrix is a collagen scaffold for the deposition of bone minerals.

Soft tissues:

• reticulin is the supporting meshwork in soft tissues such as the liver and bone marrow. Formed from the cross-linking of collagen III fibrils (fibrils see below) named 'reticular fibres' .

Collagen fibres (a group of protein molecules) are the fundamental component of our connective tissue.   There are many types of collagen in various guises.   Collagen is also one of the major proteins in our extracellular matrix. (fibrosis significance? tbc....)

For example, each and every muscle fibre (myocyte) is surrounded by connective tissue called endomysium, bundles of muscles fibres are contained within more connective tissue known as perimysium, and each muscle whole is surrounded by more connective tissue called epimysium.

Scar tissue, post-surgical adhesions, fibrosis - "the formation of excess fibrous connective tissue in an organ or tissue in a reparative or reactive process".   All are formed when connective tissue reacts. fibrosis "the formation of excess fibrous connective tissue in an organ or tissue in a reparative or reactive process".  

Connective tissue - it's everywhere!

collagen extra-cellular matrix

Examples of connective tissue - this is a tough, thin sheet known as an aponeurosis.

Connective tissue runs through the body grossly organised in myo-fascial meridians. Well illustrated by the "anatomy trains" series of publications (go-oogle images to see these layers of the body illustrated - fascinating stuff if you've not thought about how you are put together before.)

Connective tissue structures are complicated - and very prone to pain. For instance the pelvic region. The image below shows the pelvic floor muscles and surrounding connective tissues. Much of the connective tissue attaches to the sacrum and lumbar spine (not shown). Pain in this region is common, both in the muscles and form connective tissues.

Connective tissue structures of the pelvic region. (Some complicated anatomy prone to pain and strain).

Connective tissue can be thought of as a body-wide web of collagen fibres.

Collagen - some notes.

Collagen is the most abundant protein in the body. 25-35% (figures vary between sources) of the body's protein is collagen.

Collagen is a major structural protein ... protecting and supporting the softer tissues and connecting them with the skeleton. Twenty-eight different types of collagen have been identified in vertebrates. Source

Collagen is the major insoluble fibrous protein in the extracellular matrix and in connective tissue. 80-90% percent of the collagen in the body consists of types I, II, and III. Source. (Out of date on the number of collagen types but a good grounding in collagen.)

Collagen consists of:

• collagen fibres which are 'ropes' made from covalently bonded strings of
• collagen fibrils which are bundles of
• collagen molecules which are triple-helices of
• polypeptides (α chains) which strings of a repeating sequence of 3
• amino acids 'twisted' around each other.

The 3 amino acids (the building blocks of proteins) determine the type of collagen. Most collagen in the human body is type I where the amino acids are 'glycine-proline-hydroxyproline' that form a tight triple-helix that form 'straight' fibrils that bond well to create strong collagen fibres.

Extra-Cellular Matrix (ECM).

Links to : concepts of ECM , khan video - complexity and research regarding ECM. Collagen is the most abundant fibrous protein within the interstitial ECM ... Elastin and Fibronectin source - stiffening etc.....

Connective Tissue Response To Injury And Movement Lecture Notes

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