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Connective Tissue

Connective Tissue

Connective tissue -- it sounds obvious, you would think it just simply connects your tissue, right? But in fact connective tissue does so much more. Connective tissue supports, connects, and even separates your tissues and organs. It also makes up all sorts of body parts including but not limited to your bones, joints, cartilage, tendons (muscle to bone), and ligaments (bone to bone).

Connective tissue can be measured by two different ages -- chronological age and physical age. Chronological age is the obvious age, as you get older your connective tissue will start to deteriorate leaving your body at a greater risk for injury. Physical age on the other hand does not measure chronological age, instead it measures the wear and tear of your connective tissue.

Let’s look at a professional relief baseball pitcher for example. Each game, the relief pitcher needs to keep their arm warmed up throwing hundreds of pitches in the back until they are called on to then throw again in the game. This is a constant rotation on the shoulder, elbow, and wrist. Not to mention the bottom half of the player’s body from their hips to their ankles. This motion requires the full body movements every pitch adding wear and tear. This constant use of the athlete’s body physically ages the athlete’s connective tissue leaving them at a greater risk for injury.

Connective tissue is made of two major protein compounds with the majority from collagen and partly from elastin. To have a better understanding of the two, let’s dig a little deeper.


Collagen is a structural protein that is the most plentiful protein in your body. There are at least 16 different forms of collagen but the are four main types are: I, II, III, and IV. Collagen type I accounts for 90% of your body’s collagen and provides structure for your skin, bones, tendons, cartilage, teeth, and of course connective tissue.

As you age, collagen is produced less in your body -- this is more obviously seen in your skin as it will become less firm over the years. Collagen can also be damaged from sugar, refined carbs, too much sunshine, as well as smoking. These all reduce the production of collagen and interfere with the ability to be repaired.

Collagen’s main benefit is strength. It is manufactured by specialized cells called fibroblasts. Fibroblasts incorporates three main amino acids into highly distinctive strands that form the basic unit of the collagen molecule -- these amino acids include proline, lysine, and glycine. Where there are 18 amino acids present in collagen (including eight of the nine essential amino acids), 50% is represented by proline, lysine, and glycine.


Proline is a non-essential amino acid, meaning you do not require this amino acid in your diet for survival as your body naturally produces it. Proline is vital for proper functioning of your joints and tendons. It is partly responsible for creating collagen, therefore a lack of it can be very dangerous to soft tissues and joints. Without a sufficient amount of proline, you will be at a greater risk of injury and will have a much slower healing process than you would with a sufficient amount of the amino acid.

Proline can be naturally found in beef, chicken, pork, cabbage, soy, chives, asparagus, peanuts, mustard seeds, wheat, beans, cucumber, chickpeas, and buckwheat.


Lysine is an essential amino acid, meaning your body cannot produce it, you must obtain it from food sources. As another make up of collagen, lysine helps support and give structure to skin and bones.

Lysine can improve wound healing as it becomes active at the site of the wound and helps to speed up the repair process. This happens has lysine acts as a binding agent which can increase the number of cells at a wound.

Lysine can be naturally found in a variety of foods including: beef, chicken, turkey, pork, cheese, soybeans, fish, pumpkin seeds, eggs, and white beans.


Like proline, glycine is another non-essential amino acid and is recognized to be the smallest amino acid, yet it provides a wide variety of benefits to your body. Glycine is another important component of collagen as well as the construction of healthy DNA and RNA strands. Glycine also facilitates the replenishment of adenosine triphosphate (ATP) to promote muscle growth and energy during exercise.

Glycine can be naturally found in animal meat, dairy products, gelatin, and legumes.


Although elastin is not as abundant in connective tissue as collagen is, it is still very important. Elastin essentially has the property of being elastic -- it is what allows you to be flexible.

Where collagen is similar to the shape and elasticity of a shoelace, elastin is shaped very curly and is very elastic. When you expand your elastin it stretches causing tension, the more you stretch the more tension and then when not stretching it snaps back into its original form.

It is elastin that is responsible for your skin, artery walls, lungs, and intestines to expand and contract. Elastin forms a three-dimensional structure around collagen providing softness and elasticity to your body.

To have a better picture of elastin let’s look at an elastic band around a newspaper. When you first get the newspaper it is rolled up tight held with an elastic band protecting the inside pages. If you were to stretch the elastic band, the first few times it would snap right back into place but over time if you were continuously stretching the band it will lose its ability to snap back as tightly. This would cause the newspaper to not be rolled as tightly and therefore the inside pages won’t be as protected as they were from the start.

Connective Tissue Types

Now that you have a better understanding of what connective tissue is made of, let’s look at the different types of connective tissues in your body.

Loose Connective Tissue

Loose connective tissue is the most common connective tissue in vertebrates (animals with a backbone/spine). This is the tissue in your body that holds your organs in place. It gets its name from the construction of the fibers as it looks to be weaved together with lots of spaces in between.

Dense Connective Tissue

Dense connective tissue can be found in your tendons and ligaments. This connective tissue helps attach muscles to bones and also to link your bones together at the joints. It also forms a protective layer around many organs including the liver and kidneys. This tissue gets its name as it is comprised of densely packed collagen known as collagenous fibers. It is much thicker and stronger than the previously mentioned loose connective tissue.

Specialized Connective Tissue

Specialized connective tissue actually comprises several different tissues into this one category, including: adipose tissue, cartilage, bone tissue, blood and lymph.

Adipose tissue (fat) is a specialized connective tissue that is loose and lines organs and body cavities to protect your organs and insulate your body against heat loss.

Cartilage is similar to the dense connective tissue in tendons and ligaments but is more of a rubbery gelatinous structure. Cartilage is flexible and supports many structures in your body including your nose, ears, and trachea.

Bone tissue is comprised mainly of collagen and calcium phosphate, which gives your bones firmness.

Believe it or not, both blood and lymph (lymphatic fluid) are actually considered connective tissues as well! Blood serves to connect organ systems together. The same is seen with lymph as this fluid connective tissue transports white blood cells throughout your whole body protecting you from pathogens (infectious microorganism such as bacteria or a virus).

Keeping Connective Tissue Connected

As you now know, connective tissue is primarily made of two protein compounds -- collagen and elastin. Collagen being the most plentiful is mainly comprised of three amino acids -- proline, lysine, and glycine. A lack of any of these amino acids or proteins can cause a lack of structure within your body and this will put you at a greater risk for injury. It is recommended for everyone to maintain a healthy balanced diet to ensure your body is receiving the proper amino acids.

There are some scenarios where the natural production of proline and glycine and naturally found lysine within food will not be enough -- referring back to the example of the professional baseball pitcher, in order to prolong their career, they need to maintain healthy connective tissue through these amino acids in supplement form. It is always recommended to consume the highest quality NSF Certified for Sport protein supplement that you can find.

To learn more about the building blocks of protein and where to find them check out Amino Acids, Branded-Chain Amino Acids, and Non-Essential Amino Acids.