Human Bone Anatomy | Osteology

human bone anatomy

What are Bones?

Bones are not inanimate rock like structures in the human body; bones are organs that produce red and white blood cells, store minerals, enable mobility, and provide structural support for the body. They are lightweight, strong, and hard, and function within the body in many different processes, including autoimmune function. , There are two types of mineralized osseous tissue, or bone tissue, cortical and cancellous, and gives the bones rigidity and a coral-like three-dimensional internal structure. Other types of tissue found in bones include marrow, endosteum, periosteum, nerves, blood vessels and cartilage.

Primary Nutrients

Most literature proposes Calcium and Vitamin D as the primary nutrients for healthy bones.

Calcium is important in bone creation and repair. Your muscles, organs, and nerves also need calcium to function properly; nerves use sodium to pump electricity through nerves in the form of action potentials. Calcium helps to keep these actions potentials from excessively firing by working in concert with GABA receptors, most notably in high intensity auditory transduction. ( Leafy greens, fish, and some fruits are great sources of calcium.

Vitamin D is a group of secosteroids responsible for intestinal absorption of primary nutrients such as calcium, iron, and zinc. Vitamin D is synthesized in the skin is the primary way that the body produces the nutrient; though it acts as a hormone because the nutrient travels to become active in the liver and kidneys. Vitamin D has a significant role in calcium homeostasis (balancing) and production in the kidneys and liver. It also affects neuromuscular and immune function.

Protein, magnesium, Vitamin K, and phosphorus are also suggested as beneficial nutrients for bone health.

Bone Structure

Bone tissue, bone marrow, blood vessels, epithelium, and nerves make up the different types of bone cells. Tissue includes Osteoblasts and osteocytes, which are involved in the creation and mineralization of bone; osteoclasts reabsorb bone tissue. The mineralized matrix of bone tissue has an organic component of mainly collagen called ossein and an inorganic component of bone mineral made up of various salts. Bone tissue refers bone_layer_imagespecifically to the bone mineral matrix that forms the rigid sections of the organ. There are two types of bones: cortical and cancellous. Cortical bone tissue create hard exteriors for protection while cancellous bone is more spongy and allows for the metabolic processes on the interior of the organ; the two are biologically identical, but the expression of their microstructures are specialized.

Bone marrow is flexible tissue and reproduces red and white blood cells as well as lymphocytes that support the immune system. Cores of marrow in the heads of long bones create about 500 billion red blood cells per day in hematopoiesis. 4% of human physiology is bone marrow; so about 5 pounds if you weight ~125. The body creates two types of marrow: red, the only type in the body at birth; and yellow, which increases in proportion during the aging process. Transplants can cure extreme diseases and is one of the primary reasons why stem cells can be so beneficial. The body stores marrow in the femur, hips, vertebrae, and ribs.

Osteo Facts

At birth, there over 270 bones in the body, which during the aging process turn into 206 by fusing together (joining). The biggest is the femur
(thigh) and the smallest is the stapes in the inner ear.  The hard cortical tissue (outer layer) comprises 80% of mass and networks of trabecular marrow comprise the rest. Bones are mineral reserves for the body and marrow stores fat. They are metabolically very active and work in tandem with the digestive system, immune system, and endocrine system in balancing nutrients, defending against disease, and releasing hormones, respectively. 22 bones fuse together after birth to form the skull. 26 aligned, specialized bones called vertebrae make up the spine, protect the spinal cord, and form the primary support structure for the body.


Aging and Osteoporosis

The problems arising from bones occur in osteoporosis, fractures, arthritis, tumors, and infections can affect the organic tissue. Fractures are breaks in tissue, from repetitive force or trauma. Aging causes osteoporosis; the body stops producing the necessary amount of building material for the body and literally means “holey bone” (porosis meaning hole). Tumors and malignancy’s can occur in various forms in bone tissue as well. This makes it much easier for the bones to fracture.


Cancer can also occur in tissues structures and is a common site for it to metastisise to. Several primary cancers occur within the bones and some even within the marrow, such as Leukemia and multiple myeloma. The tissue distorted by cancer is normally more prone to fracture and weakness, which becomes particularly painful when it occurs in the spine.



The Human Body is an Ecosystem (Part 4/5 : Gastro-Intestinal Micro-Organisms)


Part 4: Micro Organisms of the Gut

Please see the other parts of the article; once they are completed the links will be active:

Part 1: anatomy of the human microbiome
Part 2: micro-organisms on the skin
Part 3: micro-organisms in the mouth
Part 5: implications for modern medicine

The increased knowledge of gut bacteria is a an excellent example of a paradigm shift in the health community. The scientific community has obtained an incredible amount of knowledge from this new field of microbiology. The gut flora is sometimes considered an organ because of its importance, this community of micro-organisms is evidenced to protect its host (that’s us) from pathogens and allow us to extract nutrients from our diet.

Your colon contains over 100 trillion micro-organisms most of which are bacteria. It also has the most complex and intricate interactions of the human micro-biome. The flora in the stomach and upper intestine are not as diverse or populous. This “gut” ecosystem is complex with over 400 species (identified genomes) but not quite as numerous as the 1,000 different genomes of skin micro-organisms. This is probably because of the skin’s increased interaction with the environment.

Bacteria populations within the gastrointestinal tract differ greatly depending on the host: geographical location, diet, genetics, even the behaviors of different species are vastly different based on the history of the host. Not surprisingly, diet is probably the largest factor in the populations of bacteria in the gut.

These bacteria have lots of different functions: synthesizing vitamin B and K, nutrient extraction, metabolizing bile acids, sterols, and xenobiotics, defense against pathogens, cell growth stimulation, and response to disease. They are often referred to as the forgotten organ because of the immense role they play in digestion and little attention they have received until more recently.

Gut flora evolve during the course of an individual’s life. These microbiota are non-existent until birth, and mature at the age of 3. Micro-biota are normally associated with nutrient intake, and concentration of communities are indicative of the type of diet of the host. This ecosystem, or microbiome in the gut is essentially your metabolism and what allows your body to breakdown and re-intake nutrients from your food sources. They believe this may be a reason why breastfeeding is important for infants; the nutrients help to form the initial microbiome of the child.

Without these bacterial cells, our bodies wouldn’t be able to breakdown certain nutrients. They also help the gut to maintain efficiency, especially in the colon. The colon has a lower pH level than the rest of the body, preventing harmful bacteria from proliferating and possibly even enhancing the excretion of carcinogens (cancer causing agents).

Gut bacteria have a primary role in nutrient absorption, especially electrolytes, and help the body to control its fat levels. They also help to fight allergens including over-action of the immune system. Some bacteria can even stop inflammation during the digestive process. Some genus’ of bacteria aid cancer growth, while some fight it. There is increasing evidence to suggest that obesity might be caused by bacteria populations and that the two could be intricately related.

The populations of micro-organisms in your gut is not to be under-estimated, we will be learning more about the implications of gut ecology on diet, health, and especially in obesity regulation over the next few decades. This is one of humanity’s primary links to the environment and is essential for optimal immune function. As we learn more about allergies, we will also be learning more about the ecological properties of our own bodies.

The last article in the series should be out soon, stay tuned for the implications this research has on the future of modern medicine. Questions or corrections are always welcome!




The Human Body is an Ecosystem (Part 2 of 5: Skin Micro-Organisms)

By Photo Credit: Janice Carr Content Providers(s): CDC/ Segrid McAllister [Public domain], via Wikimedia Commons

Part 2: Micro-organisms on the Skin

Please see the other parts of the article; once they are completed the links will be active:

Part 1: anatomy of the human microbiome
Part 3: micro-organisms in the mouth
Part 4: micro-organisms in the gut
Part 5: implications for modern medicine

On your epidermis (skin), there is an estimated 1 trillion micro-organisms known as skin flora, or skin microbiota. The word microbiome actually refers to their genomes, and there are about one thousand different species. Most live on the top-most layers of the skin and on the top of your hair follicles.

Skin flora are usually commensal (non-harmful) or mutualistic (beneficial). A primary benefit from these micro organisms is protecting against transient pathogens (traveling from another host) by competing for nutrients, secreting chemicals, or stimulating the skin’s immune system. Resident microbes (native to your skin) can cause skin diseases and enter the bloodstream creating illness and disease, particularly in people with weakened immune systems.

There are three different categorizations for the ecology of skin flora: sebaceous (oily or fatty), moist, and dry. sebaceous areas tend to have the greatest richness of bacterial species. The spaces between fingers and toes and inside of the belly button are the most diverse, and the nostrils and back tend to be the most similar between people. Interestingly, one study has shown that the area behind your heel has the greatest fungal diversity of the body. It also seems that as you go up the body from the ground (feet to head) there is a decrease in diversity of fungus, which intuitively makes sense because the ground has a huge amount of bacterial diversity that your body probably wants to protect against. Your feet have lots of fungus and the oily places on your body have lots of bacteria. Interestingly, most of the species of bacteria studied occasionally have pathogenic capabilities. It seems that there is a balance on the body, that when disrupted, can lead to many of the micro-organisms to become pathogenic. Let’s look into that a little bit more.

Flora can be beneficial, pathogenic, or commensal (non-harmful). Often, they can be all three, depending on the strength of the hosts immune system. I recommend reading this study on the balance of flora on the skin and how they interact, because it is extremely complex and very interesting. Essentially, the work in balance to keep each other from becoming too numerous and killing one type of bacteria can lead to growth of fungus.

Odor, interestingly, is not caused by sweat. It is caused by bacteria consuming it and creating byproducts that we consider smelly and unattractive.

Lets get back to the idea that the bacteria on your skin are actually mutualistic and beneficial when in balance. The skin creates antimicrobial peptides that control the growth of skin microbes. One example is cathelicidins which in addition to directly controlling bacterial populations, secretes Cytokine, which induces inflammation, skin regrowth, and blood vessel regrowth. Atopical dermatitis is linked to suppression of cathelicidin production; a major factor contributing to its production is Vitamin D3 (which actually isn’t a vitamin because the body produces it instead of needing to ingest it).

Your skin is slightly acidic when healthy. It has a PH of 4-4.5 due to lactic acid in sweat and produced by skin bacteria. Antimicrobial substances secreted by the skin are enhanced in acidic conditions and in alkaline conditions are more easily shed. The shedding of skin is one way that your body manages the buildup of flora on its surface. The immune system can produce cell mediated immunity against microbes, but some fungi have evolved to limit the immune response against them.

Micro-organisms also play a role in non-infectious skin diseases, like acne, atopic dermatitisrosacea, and psoriasis. Damaged skin can cause bacteria to become pathogenic. P acnes is a particular bacteria that causes acne, which can be healthy in some people and pathogenic in others. Probiotics are being used to balance the imbalance of skin bacteria that can cause acne.

Atpoical dermatitis is linked with low bacterial diversity; low gut microbial diversity in babies have been associated with increased risk in dermatitis. Other diseases will likely have probiotic cures in the future, used again to balance the populations of bacteria on the skin. These bacteria can also build immunities; the use of bacterial and fungicidal soaps will inevitably lead to bacterial and fungal populations which are resistant to the chemicals employed.

Skin flora also do not readily pass between people. This doesn’t mean you shouldn’t wash your hands after the bathroom (fecal bacteria are different from skin bacteria and make up close to 50% of your feces). The most effective (60 to 80% reduction) antimicrobial washing is with ethanol, isopropanol, and n-propanol. Viruses are most affected by high (95%) concentrations of ethanol, while bacteria are more affected by n-propanol. Unmedicated soaps are largely ineffective at controlling bacterial populations.

Over washing your skin can lead to damage through loss of water creating dryness. There are lipids in the skin that can be removed by detergents and alcohols and wearing gloves can exacerbate the problems of already irritated skin. Damaged skin can lead to normally mutualistic or commensal bacteria to become pathogenic.

Skin flora is less diverse than gut flora. Both are less diverse than soil flora. Next time, we’ll talk about oral bacteria and how your mouth has an ecosystem all its own. Stayed tuned for part 3: Oral microbiology.

I hope you’ve enjoyed this article. Please feel free to ask any questions in the comments, or to add anything you’ve found in your own research. Always happy to start a conversation.

<3 from Vietnam, Elliot


The Human Body is an Ecosystem (Part 1 of 5)


Part 1: Anatomy of the Human MicroBiome

Please see the other sections of the article; once they are completed the links will be active:

Part 2: micro-organisms on the skin
Part 3: micro-organisms in the mouth
Part 4: micro-organisms in the gut
Part 5: implications for modern medicine

Your ability to think of yourself as one whole being is an incredible phenomenon; especially considering that the human body is made up of 37.2 trillion human cells that can act somewhat independently, which is really a gross estimate at this point. What is really interesting is that the majority of the cells in your body are actually bacteria cells, mostly that reside in the human gut. Modern estimates say the proportion is about 10 to 1 (baceria to human cells). That means there are possibly over 300 trillion bacteria cells in your body. In fact, there is evidence to suggest 90% of our cells are microbes or micro-organisms. (small animals,fungi, bacteria, archaea, algae, and protozoa). Outside of the body, on the skin, there are also a fair amount of micro-animals that are excluded from the human microbiota, or the aggregate of the micro-organism genomes on the skin, in the gastrointestinal tract, in the saliva, oral mucosa, and conjunctiva.

Your body might have a proportion of 10 to 1 micro-organisms to human cells, according to one study, which makes it important to consider your body as an environment. Basically, you have an entire ecosystem in your digestive track and this aspect of your body is what merges you with your environment. The digestive tract, from the mouth to the rectum and anus, is essentially a part of the outside world which is why there is so much bacteria and other micro-organisms living there. This is also the reason behind recent skepticism of the effectiveness of antibiotics for certain illnesses and why there is so much emphasis on probiotic in modern nutrition science.

With our new understanding of the micro-organisms that co-exist within humans, we have also begun to study and catalogue the different genomes, however, scientists have found a nearly infinite variation in how the micro-organisms interact and function. The same bacteria cells might function completely differently within the body of another, making the biome extremely difficult to study. The Human Microbiome Project (HMP) is the organization fueling the majority of this research and they are attempting to catalogue the different bacteria and their functions in the body in a similar way to how the Human Genome Project catalogued the human genome.

What this means is that there are not baseline calculations for micro-biome health because it varies so greatly from person to person. Also, different sites on the body have their own distinctive communities; skin and vaginal sites have a smaller amount of diversity than the mouth and gut. Different bacteria like to inhabit different places in the mouth from person to person and can also have different, specialized functions. Over 500 types of bacteria live in the gut alone, mostly in the large intestine or colon. These bacteria are incredibly useful because they break down food and allow for the absorption of nutrients into the human body, however, in times of lowered immunity they can also act as opportunistic pathogens (meaning they can cause disease). E. Coli is one of the bacteria that exist in the gut, and certain mutated strains of this can also cause disease (as you probably heard in the news). But this is a healthy bacteria that when balanced against a strong immune system provides enormous benefit to the digestion and absorption of nutrients.

Here are the elements that create the chemical balance of your body and their associated proportional mass:

  • Oxygen = 65%
  • Carbon = 18%
  • Hydrogen = 10%
  • Nitrogen = 3%
  • Calcium = 1.4%
  • Phosphorus = 1.1%
  • Potassium = .25% (can be radioactive)
  • Sulfur = .25%
  • Sodium = .15%
  • Chlorine = .15%
  • Magnesium = .05%
  • Iron = .006%
  • Fluorine = .0037% (toxic in large amounts)
  • Zinc = .0032%
  • Silicon = .002%
  • Rubidium = .00046%
  • Strontium = .00046%
  • Bromine = .00029%
  • Lead = .00017% (toxic in high amounts)
  • Copper = .0001%
  • Aluminum = .00000087%
  • Cadmium = .00000072% (toxic in high amounts)
  • Cerium = .00000057%
  • Barium = .00000031% (toxic in high amounts)
  • Tin = .00000024%
  • Iodine = .00000016%
  • Titanium = .00000013%
  • Boron = .00000069%
  • Selenium = .00000019% (toxic in high amounts)
  • Nickel = .00000014%
  • Chromium = .000000024%
  • Manganese = .00000017%
  • Arsenic = .00000026% (toxic in high amounts)
  • Lithium = .000000031% (toxic in high amounts)
  • Mercury = .00000019% (toxic in high amounts)
  • Caesium = .000000021%
  • Molybdenum = .00000013%
  • Cobalt = .000000021%
  • Antimony = .00000011% (toxic in high amounts)
  • Silver = .00000001%
  • Niobium = .0000016%
  • Zirconium = .000006%
  • Lanthanum = .00000137%
  • Tellurium = .00000012%
  • Gold = .000000140%
  • Vanadium = .00000026%
  • Uranium = .0000000013% (toxic in high amounts)
  • Beryllium = .00000000005% (toxic in high amounts)
  • Radium = .0000000000000000001% (toxic in high amounts)

You’ll notice a few very interesting things about some of these elements. The first is that many substances can be toxic in high dosages, and obviously you can be malnourished if you have less of these elements. The second is that there are radioactive elements in your body; yes you are radioactive, just like the Earth. The radioactive elements are particularly interesting: Potassium40 has over 4,000 events per second in the human body; Carbon14 has over 3,000; Rubidium has over 100; and Lead210, Tritium, Uranium238, Radium228, and Radium226 all have under 20 events per second. To me, this emphasizes the need for balance in the human body; not too much and not too little.

It is astonishing to think that there is a hole, a series of tubes really, inside of you that is really a part of the outside environment. But this makes perfect sense to a Taoist, who would say that a human ‘is the same’ as the environment they are in. Two sides of Yin and Yang that are always playing together to continue life. Most research suggests that our gut flora (or the collective bacteria in an ecosystem) is symbiotic and has a direct relationship with the functioning of the body.

The functions of the flora are the following (though it has been found that some people can function without gut bacteria):  fermenting unused energy substrates, training the immune system, preventing growth of harmful species, regulating the development of the gut, producing vitamins, and producing hormones. Extensive modification and imbalances of the gut microbiota and its micro-biome or gene collection are associated with obesity. However, in certain conditions, some species are thought to be capable of causing disease by causing infections or increasing risk for cancer (paraphrased from Wikipedia).

So obesity might be better understood as an imbalance in gut bacteria that leads to slower digestion and less nutrient absorption. It also makes sense that there is a cascade type of effect, where the body has “momentum” to digest with large amounts of built up gut bacteria. So a ‘fast metabolism’ might be summarized as healthy gut flora. Interesting stuff right? In my opinion this is some of the most exciting science being researched today.

This is part of the reason why a balanced diet is key to being healthy. There is a lot more information coming, I’m especially excited to get into the gut flora and their implications for mental and cognitive health. The next article will be about the skin, and all of the micro-organisms that live on you. Stay tuned, hoping to have it out tomorrow.