46

The exact mechanism is unclear. Here are some possible causes: rapid collapsing of cavities inside the joint [1]; rapid ligament stretching [1]; breaking of intra-articular adhesions [1]; escaping gases from synovial fluid [2]; movements of joints, tendons and ligaments [2]; mechanic interaction between rough surfaces [2], mostly in pathological situations ...


15

Is joint-cracking harmful? No. Donald Unger was told by his mother that he'd get arthritis if he cracked his knuckles so he cracked his left knuckles every day for 60 years but never his right knuckles. He had no arthritis or any other problems in either hand and got a publication (D. L. Unger, "Does knuckle cracking lead to arthritis of the fingers?", ...


15

The wikipedia article links to two papers. The first article has data for 120 pain-free and 51 affected patients with data on the number of coccygeal segments in each. We can back-calculate a reasonable approximation of segment distributions from their percentages: 1 Segment: 7% 2 Segments: 51% 3 Segments: 38% 4 segments: 4% So 2 or 3 segments makes up ...


12

Yes, bones too bleed if they get damaged (break or bruise). This is because bones are highly vascularised organs and breaking of bones will indeed rupture the blood vessels causing bleeding. Main artery which supplies blood to bone is nutrient artery , others are epiphyseal, metaphyseal and periosteal arteries. Skeletal system receives about 15.6% of cardiac ...


9

Fracture healing occurrs in several steps: haemorrhage: blood and surrounding cells fill the space created by the fracture. fibrous callus: chondrocytes colonize the fracture space, with neovascularization. bony callus: osteocytes colonize the fracture space and rearrange in woven bone remodelling: in long bones, woven bone is remodelled into lamellar bone ...


8

Citing your source would help to answer. In order to test an elastic modulus, you need to apply some non-zero strain. If the strain is infinitesimal, then compression and stretch modulus will be equal. But if it is finite, then there can be a difference due to the structure of the material. In bone, I believe porosity will provide most of the dissymetry ...


8

The author is likely referring to the mechanosensory behavior of bone (reviewed in Huang and Ogawa, 2010; lots of Google Scholar citations). Bone loading produces very tiny mechanical deflections (strain) which are translated into biochemical signals that promote bone growth through the action of osteoblasts. Burger and Klein-Nuland (1999) review possible ...


8

A paper was just published that explains this phenomenon in PLOS One, found here. It looks like the sound is caused by the formation of a gas cavity in synovial fluid of the joints. They do mention that contrary to what is stated in the most upvoted answer here, the sound does not come from the collapse of the bubble, but rather its formation. And in ...


8

My guess is that it's a relatively young cow humerus. The strongly grooved trochleas are more characteristic of a humerus than a femur, which usually just has two condyles. The deep pit is where the olecranon process (your bony elbow) goes. The proximal end is missing, which indicates that the growth plate was not fused, suggesting juvenile. And I guess cow ...


8

I think it is part of a Australian trigger fish skull. check the pictures below, unfortunately someone sawed off most of the spine on the skull photo, but you can see the base of it, it is probably not the exact same species, but it is certainly part of a triggerfish skull. There are a half dozen species in Australia. Cool find.


7

The developmental growth of bone tissue is hormonally controlled. It is, as far as I know, not under direct neuronal control. Before reaching adolescence, the long bones (mainly in the arms and legs) grow in the epiphyseal plate, the area of the bone where cartilage is formed and ossified on the diaphyseal side, thereby lengthening the bone. The longitudinal ...


7

Here is a head and a neck: Anatomy is fairly straightforward. regarding individual long bones, "heads" are curved ends of bones distal to a narrowing called a neck of a bone. Take the radius: See how the radial head (curved) is just distal to a narrowing (neck)? The ulnar head, though, is at the opposite end, because the proximal end isn't rounded, but ...


6

lets answer in order. Is the coccyx a single bone or multiple bones? answer yes, A bone is not a concrete definition and can be used to describe the number of elements or the number of contributing elements. Bone is more a definition of material than object. My favorite example is the fused mammalian jaw which can be one or two bones (two fused ...


5

Yes, Osteichthyes do have cartilage. For example, Ancient origin of lubricated joints in bony vertebrates shows images of cartilaginous tissue in the joints of several bony fish. More generally, cartilage is required for normal bone development, and Osteichthyes are no exception (e.g. Distinct patterns of notochord mineralization in zebrafish coincide with ...


5

Bone never stops changing. Your bones are constantly being broken down and reformed on a microscopic level. Your bones are done growing at a certain point but they continue to be reshaped. Remember bone exists to supply calcium (and to a lesser extent phosphorus), to your muscles, Your body needs to break down the surface of the bones for this calcium.* So ...


4

It may be because, when we move our shoulders towards our the body, also know as abduction (Fig 1.) gives the central part of the body an elevation. when we rotate our arms more upwards (Adduction), the elevation will be lost. So in other words, when we are making snow angels, Start Normal position (hands near thighs) = Back and shoulders on ground ...


4

The word density in the medical term bone density is used to quantify only the mineral content of the bone (bone mineral). It's not intended to describe the total mass density of the bone like we are used to from physics. This is all on wikipedia: http://en.wikipedia.org/wiki/Bone_density Thus, when one say that a Grizzly bear have 10 times the bone ...


3

If you look at Fig. 2 in the paper, the bottom jaw has the split maxillary bone. Do you see how it says "MX" with two lines, instead of "MX" with 1 line on the top skull from Fig. 2? Each of those lines go to part of the split maxilla, with the joint being where it is pinched off (between teeth 5 and 6 on the drawing). There is also a CT image of the skull ...


3

Interesting question that I'd not considered before. Bone density is commonly measured by assessing the bone mineral density (BMD) using dual-energy x-ray absorptiometry (DMA), literally the g/cm2 of minerals in the bone. Having had a search I can only find values for a small number of bones commonly measured when testing for osteoporosis (characterised ...


3

Boiling point of hydroxyapatite is around 1500°C so you will need this temperature to make bone literally evaporate. Prolonged exposure to lower temperature (like reference in other answer 220°C) will break collagen and make bones weak and extremely fragile.


3

Since the argument with my girlfriend was finished days after this was posted(sadly we were waiting for this but it took so long, we posted this question to have an answer right away) I'll just post here what I conclude about the "big-boned theory" based on searching through internet. Let me site this link; that says, "However, the initial findings of ...


3

By shin splints you probably mean the pain on the inner front side of the lower 2/3 parts of the shins? This is called medial tibial stress syndrome (MTSS). Causes, mechanism, prevention and treatment of shin splints are still poorly understood. From what I managed to find, custom-made cushion insoles are the only proven prevention that can help in some ...


3

During Endochondral ossification chondrocytes in the plate are rapidly dividing, newer daughter cells stack facing the epiphysis while the older cells are pushed towards the diaphysis. As the older chondrocytes degenerate, osteoblasts ossify the remains to form new bone. In puberty increasing levels of estrogen, in both females and males, leads to ...


3

Osteocytes attach to each other by cytoplasmic extensions through gap junctions [1]. The connections between these cells are formed since they were osteoblasts and osteoid-osteocytes (type II preosteocyte) [1]. Osteoblasts have a greater volume than osteocytes and the lack of extracellular matrix favors their adhesion. As they begin to synthesize ...


3

The structure of skin (epidermis) can change with damage, when the skin is broken the body repairs this partly by recruiting cells called fibroblasts. These fibroblasts lay down collagen fibres to repair the skin. These fibres a normal component of skin are not as neatly arranged as the original fibres and may also higher in number leading to 'denser' skin. ...


3

The process is called endochondral ossification. It is important to point out that not all bone is derived from cartilage. For example, when a bone is fractured and is healing, the new bone does not always come from cartilage, rather intramembranous ossification occurs. There are therefore multiple mechanisms at a microscopic level by which bone may form. ...


3

It would be great to have a scale bar in the photo, so that the size would be easier to determine. However, by the shape of the teeth, I will propose that it is the back half of the jaw of a pig. Here is an image from the National Maritime Museum: This one is from Vanuatu and has a rather elaborate mesial portion of the jaw, but the teeth look very similar. ...


3

As Mowgli pointed out, a bone marrow transplant involves destroying the patient's own immune system with radiation and, essentially, replacing it with a new one from the bone marrow donor. If you did a double kidney/bone marrow transplant from Alice into Bob, then Bob's new immune system (which is the same as Alice's) would recognize the new kidney from ...


3

Acromegaly (pituitary gigantism) is a disease that causes enlargement of the bones of the face. There is interest in computerizing facial measurements to catch subtle enlargements and prompt testing for the disease. https://www.researchgate.net/publication/261409008_Three-...


2

You can easily search this on the web. Osteoblasts are the immature cells of bone which are responsible for the production and mineralization of bone matrix. Osteocytes are the mature cells of bone found in open spaces in bone called lacunae. The functions of osteocytes includes maintenance of bone and calcium homeostasis. Osteoclasts are responsible ...


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