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Here is a Friday afternoon question: If you cut your finger, how does your body know it must heal the cut?
Think about it. Is there a little paramedic inside your system whose sole job is to wait for you to cut yourself, get bruised in a fight, fall ill with a cold or have a life-threatening blood vessel burst? There is’nt such a person or celllike structure in us. Or is there? If there is then science needs to know. Do you know?
So how does the body know that it has some urgent healing to do? How does it know that it must stem the outflow of blood? How does it know to call in the enzymes or celss that caus the blood to coagulate? How does it know to call in the skin healers or bodyshop repair crew?
Do you know?
Please leave a message if you do, becuase this little secret is killing me and my local scientist hasn’t got the foggiest idea except for some tremulous guesstimates at how the body knows it must heal us
15 comments ↓
here. happy now?
In the inflammatory phase, clotting takes place in order to obtain hemostasis, or stop blood loss, and various factors are released to attract cells that phagocytise debris, bacteria, and damaged tissue and release factors that initiate the proliferative phase of wound healing.
Clotting cascade
When tissue is first wounded, blood comes in contact with collagen, triggering blood platelets to begin secreting inflammatory factors. Platelets also express glycoproteins on their cell membranes that allow them to stick to one another and to aggregate, forming a mass.
Fibrin and fibronectin cross-link together and form a plug that traps proteins and particles and prevents further blood loss. This fibrin-fibronectin plug is also the main structural support for the wound until collagen is deposited. Migratory cells use this plug as a matrix to crawl across, and platelets adhere to it and secrete factors. The clot is eventually lysed and replaced with granulation tissue and then later with collagen.
Platelets
Platelets, the cells present in the highest numbers shortly after wounding, release a number of factors into the blood, including ECM proteins and cytokines, including growth factors. Growth factors stimulate cells to speed their rate of division. Platelets also release other proinflammatory factors like serotonin, bradykinin, prostaglandins, prostacyclins, thromboxane, and histamine, which serve a number of purposes, including to increase cell proliferation and migration to the area and to cause blood vessels to become dilated and porous.
Vasoconstriction and vasodilation
Immediately after a blood vessel is breached, ruptured cell membranes release inflammatory factors like thromboxanes and prostaglandins that cause the vessel to spasm to prevent blood loss and to collect inflammatory cells and factors in the area. This vasoconstriction lasts five to ten minutes and is followed by vasodilation, a widening of blood vessels, which peaks at about 20 minutes post-wounding. Vasodilation is the result of factors released by platelets and other cells. The main factor involved in causing vasodilation is histamine. Histamine also causes blood vessels to become porous, allowing the tissue to become edematous because proteins from the bloodstream leak into the extravascular space, which increases its osmolar load and draws water into the area. Increased porousness of blood vessels also facilitates the entry of inflammatory cells like leukocytes into the wound site from the bloodstream.
Polymorphonuclear neutrophils
Within an hour of wounding, polymorphonuclear neutrophils (PMNs) arrive at the wound site and become the predominant cells in the wound for the first three days after the injury occurs, with especially high numbers on the second day. They are attracted to the site by fibronectin, growth factors, and substances such as neuropeptides and kinnins. Neutropihils phagocytise debris and bacteria and also kill bacteria by releasing free radicals in what is called a ‘respiratory burst’. They also cleanse the wound by secreting proteases that break down damaged tissue. Neutrophils usually undergo apoptosis once they have completed their tasks and are engulfed and degraded by macrophages.
Other leukocytes to enter the area include helper T cells, which secrete cytokines to cause more T cells to divide and to increase inflammation and enhance vasodilation and vessel permeability. T cells also increase the activity of macrophages.
Macrophages
Macrophages are essential to wound healing. They replace PMNs as the predominant cells in the wound by two days after injury. Attracted to the wound site by growth factors released by platelets and other cells, monocytes from the bloodstream enter the area through blood vessel walls. Numbers of monocytes in the wound peak one to one and a half days after the injury occurs. Once they are in the wound site, monocytes mature into macrophages, the main cell type that clears the wound area of bacteria and debris.
The macrophage’s main role is to phagocytise bacteria and damaged tissue, and it also debrides damaged tissue by releasing proteases. Macrophages also secrete a number of factors such as growth factors and other cytokines, especially during the third and fourth post-wounding days. These factors attract cells involved in the proliferation stage of healing to the area. Macrophages are stimulated by the low oxygen content of their surroundings to produce factors that induce and speed angiogenesis. and they also stimulate cells that reepithelialize the wound, create granulation tissue, and lay down a new extracellular matrix. Because they secrete these factors, macrophages are vital for pushing the wound healing process into the next phase.
Because inflammation plays roles in fighting infection and inducing the proliferation phase, it is a necessary part of healing. However, inflammation can lead to tissue damage if it lasts too long. Thus the reduction of inflammation is frequently a goal in therapeutic settings. Inflammation lasts as long as there is debris in the wound. Thus the presence of dirt or other objects can extend the inflammatory phase for too long, leading to a chronic wound.
As inflammation dies down, fewer inflammatory factors are secreted, existing ones are broken down, and numbers of neutrophils and macrophages are reduced at the wound site. These changes indicate that the inflammatory phase is ending and the proliferative phase is underway.
sheesh!!! haven’t they taught you anything inschool???
xo,
M
Ummmm yeah ok but - how do they know what to do and when?
I was going to comment with, “I could give you a thesis on this.” But I see you already have one! ROFL
How you been Rob, you have kept very quiet recently? Hope you are well.
Cheers man
Hey Phlippy,
I am very well. Just went dark for a while to complete a couple of projects.
One of them will be published later today I hope. If not, then tomorrow for sure.
I am now on a serious mission. It relates to all Africa but I am obviously biased to the South and so will relate it to the South accordingly. I am hoping that the message will ring a few bells.
I know that it will earn me some enemies but that is what going out on a limb is all about. I may end up in arguments with certain people but it all helps to bring the truth to light.
Conversations are very importamt to our continued progress. If we do not have them and allow stagnation to occur, Africa’s peoples will begin to wither away.
So, get ready, want daar gaan n beitjie kak in die land wees!!
I enjoyed your comment. Cutting, cutting, cutting or what???!! Hey Misty - someone’s got your number……!!
And I still do not know how the body knows when it has been injured.
Imagine the skin as being an electric fence. Should there be a break in the circuit, this is signalled back at HQ (the brain) and little guys are sent out to see what is wrong and close the break asap, so unhealthy buggers don’t get in, and the sweet precious innocent blood gets out.
Voila!
No not ‘Voila’!
How do the good buggers KNOW they must loop quickly to a broken bit?
Also how do they know how and when to stop?
Cause guys at HQ call them on their walkie talkies & tell them to rush their cute asses over to that particular area.
They have been trained in boot camp to know when to stop. You can’t just let old clueless fool repair a broken electric fence after all. But know that it is also like the olden days, where professions stayed within families for generations. So all these electric fence-fixers’ fathers did the same job, whose fathers did the same job and all the way back to the adam-and-eve of electric fence fixers. In the body, cells or whatever stick to their inherited roles.
Scientist Champs in the House
Your summation is flawed.
If some okies in HQ have walkie-talkies to contact the Repair crew to proceed to a certain area of the park to fix a section of fence, who contacted HQ in the 1st place to alert them to a broken fence?
And in the interest of survival, why didn’t the invisible unknown oke have a walkie talkie to contact the Repair Crew in the 1st instance to avoid delays?
No no, there is no oke there at the split. It is all “electronic”, if you will. So the computers at HQ detect when there is a break in the system, and the guys monitoring these computers see the flashing lights and alerts and then contact repair crew who are on the ground ready and waiting to go.
So do tell us how an oke at HQ with a walkie Talkie installs computerised detection kit to set off an alarm of a breach of te skin?
How did the installation guy know what to do? Mmmm……
God, Allah, and a coupla evolving apes sat around a board room table & drew up an operational plan. Every time a sperm hits an egg, the eg hands over this Ops Plan & says, read up boy, it ain’t easy to build one of these things!
But millions and billions of dicks have been built and that is another issue I have. Was the prototype a biggus dikkus or a Web 2.0 geek? But more of this later.
I still am nowhere close to understanding how the body knows how and when it must heal itself?
Are you telling me that some imaginary diety and his mate got together on a Saturday afternoon first to watch Match of the Day and then plan an Ops plan over a curry vindaloo, to be couriered by a sperm into the ovarian tubes of some poor unwitting woman so that another imaginary oke with a walkie talkie can react to an alarm network set up by an invisible host and get other Rescue okes to scuttle off to an area of our body where something like a needle or a shard of glass has penetrated through the first defensive system we humans have?
Yes!! Exxxactly! Except for the ovarian tube part - the sperm is not meant to be that over-achiever & rather just remain within the more general womb area.
And also, it wasn’t chicken vindaloo, but rather a tasty paella, as it was prawn season!
No what I mean blokes - you just can’t ever satisfy a woman! Now I get the nagging about my navigation! Hey lady I can park where I like. Its free. The parking is Pay and Display but if I find a space in the general area of where I am meant to be then why not take the 1st space that I see?
Also the cooking is getting slagged off. If I want the diety to have a vindaloo then that is what they get. If the diety was female then paella might be on the menu! But it ain’t!
Can I now please say that nobody knows how the body knows it must heal a cut finger?
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