Feeds

What lies without

Life on the human body

The smart choice: opportunity from uncertainty

Also in this week's column:

What lies without: Life on the human body

The skin of the human body is alive with life - microscopic life of all kinds. In his classic work, Life on Man (1969), Theodor Rosebury estimates that there are 10m individual bacteria living on the average square centimeter of human skin (155,000 per sq inch).

Rosebury describes all of these robust, active, fertile microscopic creatures as like a "teeming human population during Christmas shopping". The population of bacteria on the 2 sq meters (21.52 sq feet) of the skin surface of the human body varies depending upon what part of the body you examine.

The most bacteria-prone parts of the body are the armpits, the anal region, the pubic region, and the oily sides of the nose. For example, the armpit is the home of up to about 203,000 bacteria per square cm (516,000 per sq inch). Each square cm of human skin consists of about four million cells (10m per sq inch), 24 hairs (60 per sq inch), 35 oil glands (90 per sq inch), 6.1 meters of blood vessels (20 feet per sq inch), 246 sweat glands (625 per sq inch), 7,480 sensory cells (19,000 per sq inch), 23,622 pigment cells (60,000 per sq inch), more than 393 nerve endings (1,000 per sq inch), and all of that microscopic life.

Although all the microscopic life is high in numbers, it is small in size and weight. Rosebury estimates that all of the bacterial life on the human skin surface would fit into a medium-sized pea and possibly weigh about as much.

It is not just bacteria that live on the human skin. We can also become infested with a variety of creatures that set up household on our skin and dine there to their little heart's content.

According to Dr Jonathan Kantor of the Department of Dermatology at the University of Pennsylvania Medical Centre in Philadelphia, there are three types of louse (Pediculus humanus corporis) that can live on humans. They are head lice (Pediculus capitis), body lice (Pediculus humanus), and pubic lice (Pthirus pubis). No prizes for figuring out where on the body each type lives.

There are also the follicle mite (Demodex folliculorum) that lives on the eyebrows, the scabies mite (Sarcoptes scabiei) that lives everywhere, and several other Trombiculae mites (chiggers, redbugs, rougets, harvest, and scrub) that camp out everywhere. In addition there are the tropical rat mite (Ornithonyssus bacoti), the human bot (Dermatobia hominis), the primary screwworm (Cochliomyia hominivorax), and of course ticks, fleas, bed bugs, and a few others. Our skin is a veritable United Nations of tiny critters.

Stephen Juan, Ph.D. is an anthropologist at the University of Sydney. Email your Odd Body questions to s.juan@edfac.usyd.edu.au

Eight steps to building an HP BladeSystem

More from The Register

next story
Malaysian Airlines flight MH17 claimed lives of HIV/AIDS cure scientists
Researchers, advocates, health workers among those on shot-down plane
Forty-five years ago: FOOTPRINTS FOUND ON MOON
NASA won't be back any time soon, sadly
Mwa-ha-ha-ha! Eccentric billionaire Musk gets his PRIVATE SPACEPORT
In the Lone Star State, perhaps appropriately enough
MARS NEEDS OCEANS to support life - and so do exoplanets
Just being in the Goldilocks zone doesn't mean there'll be anyone to eat the porridge
The Sun took a day off last week and made NO sunspots
Someone needs to get that lazy star cooking again before things get cold around here
Diary note: Pluto's close-up is a year from … now!
New Horizons is less than a year from the dwarf planet
Boffins discuss AI space program at hush-hush IARPA confab
IBM, MIT, plenty of others invited to fill Uncle Sam's spy toolchest, but where's Google?
prev story

Whitepapers

Seven Steps to Software Security
Seven practical steps you can begin to take today to secure your applications and prevent the damages a successful cyber-attack can cause.
Consolidation: The Foundation for IT Business Transformation
In this whitepaper learn how effective consolidation of IT and business resources can enable multiple, meaningful business benefits.
Designing a Defense for Mobile Applications
Learn about the various considerations for defending mobile applications - from the application architecture itself to the myriad testing technologies.
Build a business case: developing custom apps
Learn how to maximize the value of custom applications by accelerating and simplifying their development.
Consolidation: the foundation for IT and business transformation
In this whitepaper learn how effective consolidation of IT and business resources can enable multiple, meaningful business benefits.