#knuckles – @biomedicalephemera on Tumblr

Fig 1. Anterior Aspect of the Fingers - Veins, tendons, nerves, and aponeuroses Fig 2. Posterior Aspect of the Fingers - Exterior surface, skeletal articulation, vessels and nerves, and fibrous membranes of the extensor tendons Fig 3. Perpendicular and Longitudinal Section of the Last Phalanx - Showing the composition of the nail and distal end of the thumb Fig 4. Exterior Side View of the Finger - Bent at different articulations to show the angle of articulation

The palm of the hand is glabrous (hairless), and has nearly 1600-3000 sweat glands per square inch in most people. For comparison, the armpits have about 600-1500 sweat glands per square inch, on average.

An Atlas of Surgical Apparatus. Henry Thomas Chapman, 1832.

Source: archive.org

#anatomy #fingers #hands #science #medical illustration #medicine #bones #veins #1830s #1832 #henry thomas chapman #dissection #tendons #knuckles #TIL #sweaty palms

biomedicalephemera

Tendons and bursa of index finger

The tendons of the hand wrap very close to the bones of the fingers, and the loss of subcutaneous fat is the primary reason that the fingers of the elderly, moribund, and chronically ill appear so bony, yet don’t seem to lose much of their strength.

My grandma once ripped out a 3″ x 0.5″ splinter lodged more than two inches in the sole of my foot after my mom, dad, and forest fire-fighter uncle failed to anything other than make it scoot to the side. Her hands were absolutely skeletal. Don’t underestimate those bone-hands.

Atlas of Applied (Topographical) Human Anatomy. J. Howell Evans, 1906.

#tendons #hand #medical #science #illustration #skeletal #skeleton #bursa #knuckles #joints #bursitis #1900s #1906 #Evans #subcutaneous fat #fat #bamf #family #anatomy #blah blah blah

biomedicalephemera

katarafirelady asked:

Hello! I have a question that I hope you will be able to help me with! (if not thats ok!) People are always on my case about cracking my knuckles. They say that it will damage my hands, give me arthritis etc. but It calms my nerves and my hands get itchy and uncomfortable if I don't do it, so i generally just do. In my research, I have never found any studies that show definitive proof that knuckle cracking is bad. Do you know of any adverse effects of this habbit? Thanks for any help!

Well, aside from being slapped in the face for annoying people with the noise, no, there are no studies that show long-term side-effects from knuckle cracking.

There have been several long-term, well-designed cohort studies performed on this, and none of them show a statistically significant increase or decrease in any negative physiological processes or diseases. Joints crack naturally, and cracking them on your own does not make a difference in their structure.

This myth probably arose due to the high incidence of osteoarthritis (“normal” arthritis - that which is not from rheumatism or infection) among the elderly, many of whom either had/have a habit of knuckle cracking at some point in their life. It’s a common habit that many people have at some point or another, even if it’s not a lifelong thing.

A humorous paper that took this question to the extreme was the winner of a 2009 Ig Nobel prize: Donald Unger was chided by his mother, mother-in-law, and teachers for cracking his knuckles, so for 50 years he only cracked the knuckles on one hand and not the other, and found that he developed no arthritis on either side, and his flexibility was roughly the same on both sides.

Of course, a single-patient experiment is necessarily unblinded and biased, but it does follow the same line as the results of prior experiments.

————————

I will say you don’t want to crack Knuckles, though. That mofo is crazy as is.

#arthritis #knuckles #i am not a doctor #knuckle cracking #medical #osteoarthritis #ig nobel #links #spookykangaroo

biomedicalephemera

openlibrary.org

Bone attitude during flexion of the fingers

The knuckles are much more prominent when the hand is clenched, or the fingers are flexed - this is because when the phalanges are pulled toward the palm, the metacarpus (note: term for all metacarpal bones taken as one unit) is largely stationary. The carpals slide down, and the heads of the metacarpals are made to be the prominent protuberances.

On a side note, the source of the sound made while cracking your knuckles still hasn't been definitively proven. However, the "cavitation" theory, that small cavities of partial vacuum form and rapidly collapse within the synovial fluid, is the most well-supported and widely-theorized.

Oh, and you won't get arthritis by cracking your knuckles, unless you have some preexisting condition that I've never heard of (granted, I've never heard of most conditions that affect bones...). There have been several large, long-term cohort studies that show no correlation between arthritis and knuckle cracking. Well-designed studies aside, there's also Dr. Donald Unger (winner of the 2009 Ig Nobel Prize in Medicine), who, after being told by his mother that he'd get arthritis if he kept the habit up, cracked the knuckles on one hand every single day, multiple times a day, for over 60 years. He never cracked the knuckles on his other hand. Neither of them developed arthritis or any other condition. Now THAT'S a dedication to science!

Applied Anatomy; the construction of the human body. Gwilym G. Davis, 1915.

Source: openlibrary.org

#hands #bones #anatomy #medical #physiology #flex #knuckles #Erwin F. Faber #ig nobel #donald unger #gwilym davis #1910s #1915