How many animal cells can fit on the head of a pin?

Answer 1

Well, let's see. How large is the head of a pin? Maybe 2 millimeters in diameter? That means its area in square millimeters is Pi, since its radius squared = 1. So, 3.1428 square millimeters. Which equals 3,142,800 square micrometers.

A red blood cell is about 7 micrometers in diameter, so its surface area on one side is about 38.5 square micrometers. However, rounded objects cannot be packed to fill all available space, so let's think of one red cell as a square, 7x7 micrometers = 49 square micrometers.

So, if you divide the area of the pinhead in square micrometers by the rectangular size of a red blood cell in square micrometers, you get a bit more than 64,000 red blood cells on the head of a pin. Some other types of human cells are somewhat larger than red cells of course, so a correspondingly smaller number would fit into the same space.

Answer 2

It depends on the size of the cells - they're not all the same size. A hen's egg, for instance, is a single cell, and it's obviously much too large to fit on the head of any pin I've ever seen!

Answer 3

I used to work on a lab doing blood test. the diameter of the objective Len of a microscope is like 2mm and I remember when I look at the white or red cells I used to see like 200 per field more or less, maybe 400 but no thousands.

Answer 4

all of them

Answer 5

depending on the cells i'd say like 50-100, pauls method is certainly valid but I think that two millimeters would be huge for a pin.

Answer 6

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WHAT CAUSES THE RASH There is an oil, called urushiol, that causes an allergic reaction after the first sensitizing exposure. The oil is in the leaves, vines, and roots. IMMUNITY Some people appear to be immune, others become immune. HOWEVER, you can gain or lose immunity, so to assume you can't get it if you never have before is foolish. People change as they age. YOU CAN GET IT FROM... Although pets can also become contaminated by running through patches of poison-ivy, animals do not react to the poison. A sensitive person can be poisoned merely by petting a contaminated animal. The oil is also said to be vaporized by heat such as would be present in a bonfire or a smudge. The vapor thus formed may be carried by the smoke and if a susceptible person walks through the smoke or inhales it, very serious reactions may result. The oil may also be vaporized, or sprayed out like an atomizer, from fresh plants as they are being cut and contaminate a nearby person or the person's clothing even though there is no direct contact with the poison-ivy plant. WHY AREN'T ANIMALS AFFECTED? SIMPLE VERSION Urushiol ultimately interacts to trigger the allergy with the human T-cell. The same reason a dog can not not get HIV, or the Bubonic Plague, but a human can. COMPLICATED VERSION Some people are so sensitive to urushiol that it only takes a molecular trace (two micrograms or less than one millionth of an ounce) on the skin to initiate an allergic reaction (Epstein et al, 1974). Even the amount on a pinhead is sufficient to cause rashes in 500 sensitive people. If 2 micrograms of urushiol is sufficient to initiate a reaction in one hypersensitive person, then 1000 micrograms of urushiol (2 X 500) could initiate reactions in 500 hypersensitive people. Using 60 micrograms for a size comparison with an average grain of table salt, 1000 micrograms of urushiol would be roughly equivalent to 1000/60 or 17 grains of salt. An average cuboidal grain of table salt (NaCl) is about 0.3 mm on a side with an area of 0.09 mm2. The average pin head is 1.5 to 2.0 mm in diameter. A pin head with a diameter of 1.5 mm (0.75 mm radius) has an area of 1.767 mm2. Dividing the area of an average pin head (1.767 mm2) by the area of a single grain of salt (0.09 mm2) gives a value of 19.63 grains of salt. Therefore, 17 grains of table salt would fit on the head of an ordinary straight pin. [Of course, even more grains would fit on the head of a pin if they were moistened and clumped together.] Approximately 80-90 percent of adult Americans will get a rash if they are exposed to 50 micrograms of purified urushiol (Epstein et al, 1974). This is indeed a minute amount when you consider that one grain of table salt weighs about 60 micrograms. An urushiol residue on the skin is difficult to wash off and may be spread by scratching. Contrary to popular belief, it is not spread through blister fluids. It is a relatively stable compound and can retain its potency for years in the absence of oxidation. Herbarium specimens 100 years old have been known to cause dermatitis. It is readily transferred from contaminated clothing, objects and fur of animals. Urushiol readily penetrates the epidermal layer of the skin where it binds to proteins of deeper skin cell membranes. Before the protein bond can occur the catechol is oxidized to a more reactive quinone in which the two OH groups are replaced by double-bonded oxygens. The reactive quinone bonds to white blood cell membranes deep in the skin. In the conjugated state (bound to cell membranes) urushiol is virtually impossible to wash off. By itself the urushiol molecule (also called a hapten) probably would not initiate a full-blown immune response, but when attached to the cell membrane it becomes a "warning flag" that attracts patrolling T-cells. Urushiol causes a complicated delayed allergic reaction with the body's immune system. It is technically classified as a cell-mediated immune response and the "peak misery" may not appear until days or weeks later. It is quite different from the primary irritants of nettle and euphorbias, the effects of which are immediate. The following hypothetical "two-phase" scenario for poison oak dermatitis is summarized from Epstein (1984). PHASE I (Induction): Initial contact with poison oak may result in urushiol penetrating the stratified squamous epithelial cells of the skin and binding to large dendritic (branched) white blood cells in the epidermis called Langerhan's cells. [Note: Some immunology textbooks state that the urushiol allergen is engulfed by the Langerhan's cells. The allergen and a small protein fragment called "major histocompatibility complex" (MHC) is then displayed on its membrane and presented to the effector T-cells.] The Langerhan's cell (with urushiol allergen and MHC protein on its membrane) migrates to a nearby lymph node where clones of special white blood cells, called effector T-cells, are programmed to recognize urushiol. [Note: Some immunology textbooks refer to these clones of T-cells, with urushiol receptor sites on their membranes, as "helper T-cells." There are literally millions of effector T-cells (helper T-cells) roaming throughout the blood and lymphatic system, each with special receptor molecules on their membranes for a particular allergenic chemical, such as the urushiol of poison oak. T-cells patrol our circulatory system looking for invading cells and viruses, inspecting surface membranes like security guards checking I.D. cards. PHASE II (Elicitation): If you get urushiol absorbed into the skin during a subsequent encounter with poison oak, an effector T-cell may encounter it bound to a Langerhan's cell and attach to it by a complicated and specific recognition system. The effector T-cell then produces more clones of itself and releases special proteins called lymphokines (cytokines) which attract a legion of different white blood cells, including "cell engulfing" macrophages and cytotoxic ("killer") T-cells. The killer T-cells are also produced in regional lymph nodes during the Elicitation phase, and according to some textbooks, they also have urushiol receptors on their membranes. The new army of white blood cells releases lytic enzymes and protein toxins (perforins) which destroy everything in the vicinity including membrane-bound urushiol and other skin cells, thus producing a blistering rash. Fluid oozes from the blood vessels and lymphatics (edema) and cell death and necrosis (breakdown) of skin tissue occurs. Milder effects range from redness (vasodilation) and itching (nerve injury) to small blisters (vesicles and bullae). Well, are we all clear on that?