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Horses sweat, gentlemen perspire and a lady glows. But apart from that, there are various other bodily functions which result in the emission of matter from the human body. Our cultural beliefs cause us to regard these with varying degrees of ickiness. Here is an owner's guide to our various corporeal exudances.
Human life is dependent upon the oxidation of carbohydrate materials (a process called metabolism). Oxygen is drawn from the atmosphere, absorbed via the lungs into the bloodstream and carried to its point of use. The carbon dioxide product of metabolism is carried onward through the bloodstream until it reaches the lungs, where it is released in gaseous form. The build-up of CO2 within the lungs triggers sensors such that when its concentration reaches a certain level, the musculature are signalled to expel the gaseous contents of the lungs (which still contain a higher proportion of oxygen than CO2) upwards through the respiratory tract. This is the basic process of exhalation.
Exhalation also plays a major role in thermoregulation - the removal of the heat generated by exothermic (heat-releasing) metabolism. As the body heats up, water vapour is emitted into the lungs. The exhalation of warm, moist air contributes considerably to heat loss. This is, in fact, our major thermoregulatory mechanism, contributing more than perspiration (see below) or radiative heat loss.
Various other compounds are included in the exhaled air. These are detectable in varying degrees by the human nose and lead to judgements on the aesthetic quality of the human breath. Sources of exhaled olfactory compounds include:
The by-products of protein decay from food material in the mouth or mucus in the upper respiratory tract. These can be very unpleasant and are referred to as halitosis.
Organic compounds from food substances which permeate back from the bloodstream into the lungs. These include organo-sulphurous compounds found in the alium family (garlic, onions) and alcohol and its metabolic products.
By-products of the incomplete metabolism of carbohydrates. Medical personnel are trained to recognise diabetes by smelling these compounds on diabetic patients' breath.
A degree of control can be achieved over exhalation. By control of the exhalatory musculature of the chest and by modification of the airflow by the larynx, tongue and lips, humans are able to perform various extraordinary tricks. These include whistling, trumpet-playing, blowing bubbles and speech.
The human respiratory tract is protected by secretions of mucus. This has the effect of retaining moisture and trapping inhaled particles. On some occasions, for example as a result of respiratory disease, excess mucus is produced. People can become uncomfortable when this blocks the respiratory track or when it solidifies. The solution to this is expectoration. Excess mucus is expelled as sputum, either as an involuntary action, coughing, or voluntarily, coughing can be voluntarily induced, or the throat can be cleared by a complex movement of the larynx. The sputum collected in the mouth is either swallowed or expelled by spitting. Voluntary expectoration can also occur nasally.
Involuntary expectoration is generally regarded as socially acceptable. However, Western etiquette generally demands that coughers cover their mouths with their hands, do not cough directly onto other people or their food and carefully collect any resultant sputum in a handkerchief1. Voluntary expectoration by spitting is generally thought to be 'a bad thing'. However, there are unfortunate exceptions to this. Naturopathy (a system of alternative medicine which aims to prevent disease by using treatments such as physical therapy, nutrition and herbalism) advocates the health benefits of spitting sputum onto the ground in order that harmful bacteria may be killed by exposure to sunlight. A second exception is during televised football matches. Admittedly, mucus build-up is increased on vigorous exercise, and professional footballers find it inconvenient to carry handkerchiefs onto the pitch. But - please! - do the cameras have to home in on their voluntary expectorations quite so often?
Sternutation is caused by irritation of the mucous membranes of the nose. Irritation may be due to foreign bodies or may be caused or exacerbated by inflammation of the membranes due to disease (eg common cold, allergies, opiate withdrawal). The sneeze reflex is caused by the medulla (part of the brain) after the irritation is signalled to it via the trigeminal nerves in the face. It causes a sudden contraction of the exhalatory muscles, causing air to be discharged with such a force that it sweeps clean the membranes. The uvula2 and soft palate in the mouth are usually depressed, closing off the mouth so that most of the volume of the discharged air passes through the nose. Sometimes the discharge is preceded by a preparatory gulping for air (the 'Ah-ah-ah-' part).
The sternutatory discharge (the 'CHOO!' part) may consist of both solids and liquids, as well as microscopic droplets of water which are frequently the carrier for viral bodies. Since the velocity of a discharge can reach 145km/h (equivalent to hurricane force), these droplets can be carried far from a disease carrier's body.
Despite the health aspect, there are few taboos about sternutation, provided handkerchiefs are used. Indeed, in Islamic tradition, the Prophet Muhammad approved of sternutation and encouraged a form of prayer and blessing in response3. For some there is an erotic connection between sternutation and orgasm. Those seeking further information may wish to search the less reputable byways of the Internet.
Sternutation is also known as sneezing.
The human skin is covered in thousands of glands - the eccrine sweat glands. These contribute to evaporative heat loss by exuding a watery solution containing mainly salt (sodium chloride) and urea. Evaporation is inefficient in a humid atmosphere, so this liquid often collects on the skin as liquid sweat. The sweat of a freshly-bathed lover can be a very pleasant thing. However, compounds within sweat promote bacterial growth, especially in areas with high concentrations of sweat glands and where the sweat becomes trapped by body hair (the underarms, the genital area). Bacterial putrefaction can cause unpleasant smells, and the removal or masking of this forms a significant part of human commerce.
Salivation is the emission of a fluid known as saliva from three glands in the mouth, the parotid (just below and in front of each ear), the submaxillary (below the jaw) and the sublingual (below the tongue). Saliva is a solution of proteins, electrolytes and amylase (an enzyme that is mixed with food when it is chewed and contributes to the digestive process). It is produced in response to eating - and even in anticipation or on thinking of eating.
Normally saliva is either swallowed or re-absorbed within the mouth. It can leave the mouth in one of two ways:
If the mouth is left open (eg, during sleep), excess saliva can drool out, sometimes to the amusement of onlookers.
Voluntary expectoration of saliva, possibly mixed with mucus, can effect a discharge at some distance, especially with skilled application of the lips and cheeks4.
Public spitting is generally regarded as unsavoury. In law, to spit on someone is an assault, and 'No Spitting' is a central part of the h2g2 House Rules. However, in the southern states of the USA, where tobacco is chewed, discharge of the foul sputum so generated is regarded a tolerable necessity. Spittoons are provided in public places.
Spitting can be become a contentious inter-cultural issue. Muslims are forbidden by their religion from swallowing anything during daylight hours in the month of Ramadan. This is interpreted by some to include swallowing saliva, so if they have excess saliva, the customary way to dispose of it is by spitting. This is forbidden by law in many places in the UK.
When the male human genitalia are stimulated, eventually - provided it is done right - a rhythmic contraction of the cremaster muscle causes seminal fluid, manufactured and stored in the prostate gland, to be forced at speed down the urinary tract and out of the body. In reality, this process is more attractive than it may seem here and is the only one of the processes discussed which gives consistent pleasure.
In male humans, the purpose of ejaculation is primarily to carry sperm cells. These are manufactured within the seminal vesicles of the testes and reach the prostate gland via a duct called the vas deferens. During sex, the force of ejaculation is such that seminal fluid is forced up the female internal genitalia, giving sperm a head start in their marathon swim for the prospect of a chance encounter with an ovum in one of the recipient's fallopian tubes. Note, though, that male ejaculation is not restricted to the reproductive act but can also be enjoyed in recreational sessions, alone or with a cooperative partner. Roughly 10ml (or 10cc) of ejaculate is emitted on average at a time (approximately a dessertspoonful) giving rise to two band names (the other being The Lovin' Spoonful).
Some but not all women are also capable of ejaculation following genital stimulation, the fluid (which does not, of course, contain sperm cells) being discharged via the urethra. This phenomenon has been recorded in several interesting films. Filmed ejaculations, male or female, have a high commercial value: in the adult entertainments industry, the male jouissance is known as 'the money shot'.
As Alice Cooper sang, Only Women Bleed. The reproductive cycle of the female human is cyclical, with an average periodicity of twenty-eight days. In fertile women of reproductive age (approx 8-16 years of age to 48-55), an ovum is produced once during this cycle. This process is termed ovulation. In preparation for the reception of the fertilised ovum, the lining (or endometrium) of the uterus builds up a mass of cells and veinous channels. If the ovum is not fertilised, these are shed via the vagina. The process is somewhat messy and in many cultures, absorbent materials are worn externally or internally to limit the spread of the menstrual flow.
Some societies regard this natural process with distaste and suspicion. Many cultures have superstitions which affect the behaviour and treatment of the menstruating woman - ranging from taboos against sexual activity, food preparation or planting crops to seclusion from normal life. In some cases women are required to undergo ritual cleansing following menstruation. In Jamaican Patois, 'blood claat' (ie, sanitary towel) constitutes a heavy duty insult.
Modern Western culture is, to some extent, slightly more enlightened. Menstruation is culturally represented as a celebratory time when women should take up new hobbies such as roller-skating or sky-diving (although many women prefer to 'celebrate' the event with a bottle of red wine and a large block of chocolate). In reality, menstruation is regarded with distaste by many; sexual intercourse is avoided and the whole palaver is termed 'unsanitary'. A well-known contestant from the Celebrity Big Brother television show once said 'A woman cannot call herself liberated unless she is prepared to taste her own menstrual flow.' The fact that some of you will now be thinking 'ick' says much about the place of menstruation in contemporary culture.
Humans reproduce viviparously, that is a new human is grown within the body of its mother. Around nine months after fertilisation, a long series of intense contractions of the uterus forces the new human to be expelled from its mother's body via the birth canal. This process is called birth5.
Some readers may have difficulty thinking of a tiny, cute, ickle-wickle baby as 'effluvia'. However, as anyone who has witnessed the glorious miracle of childbirth will attest, the tiny human comes accompanied by various pieces of detritus of a far less cuddlesome nature. These include the amniotic fluid (the 'waters') which gush forth near the start of labour, and the umbilical cord and placenta which have provided the baby with its support services during gestation. As Billy Connolly said 'Childbirth is wonderful! It's miraculous and beautiful and marvellous!...But it's not a spectator sport!'
Newborn humans receive nourishment in the form of a fluid secreted by the lactatory ducts within their mothers' breasts. Human milk is a highly nutritious source of carbohydrates (lactose and ogliosaccharides), proteins, lipids and minerals and also provides antibodies and many other complex chemicals which are only partially known or understood. Human milk is one of the few bodily discharges which is available in synthetic, but inferior, form6.
Despite the obvious convenience of a ready-made food supply, some modern societies have curious taboos about breastfeeding, regarding lactation with distaste and getting hot and bothered about public breastfeeding. Attitudes differ between countries, probably explaining the marked difference in breastfeeding rates, and there has been some evidence of a shift in recent years7. It would be interesting to speculate on the origin of such a taboo - whether from a general distaste over bodily discharges, or a fatherly jealousy over forced sharing of what he regards as 'his' toys. Some women also regard their breasts as sexual organs only and find the idea of breastfeeding repellent.
The human body is covered by a thick impermeable coating which prevents the insides from becoming the outsides (except as noted in this entry). This is called skin. As with most types of cell, skin cells continuously die and new ones are generated to take their place over a lifetime. The dead cells from the epidermis - the outer layer of skin - are detached from the body and shed to provide a vital food source for fungi, insects, bacteria and all manner of beasties.
Exfoliation is also the term used to describe the spontaneous shedding of deciduous teeth in children between the ages of approximately five and ten as they make way for the adult teeth. These teeth are sold by children to the tooth fairy according to the terms of a long-standing contractual arrangement which pegs their price to inflation8. It is believed that the fairies use the teeth to build palaces.
Humans, even those that appear relatively smooth, are covered with thousands of hairs. These are in particular concentration on the head, under the arms and around the genitals, but are also spread around much of the skin. These grow at a constant rate. New hairs grow as older ones are shed, and this is known as epilation. This is in contrast to depilation - the voluntary removal of hair by shaving, plucking, waxing or chemical or heat annihilation9. In male humans, hormonal changes in some adult specimens causes the rate of epilation to exceed that of growth. This is termed balding. While balding need not be a problem if carried off with aplomb, it is a source of anxiety to many men, causing them to resort to various disguise tactics, such as wearing artificial head covers or sporting amusing hairstyles such as the combover, also known as the Scargill10.
Human eyes are capable of moving within their sockets. For this to happen smoothly, they have to be kept constantly lubricated by the secretion of tears from lacrimatory ducts in the outside corner of the eye sockets. These tears also carry oxygen and nutrients to the surface of the eye, protect it from damage and provide a good optical coating for the lens. The tears are secreted into the lacrimal lake, the area between the eyeball and the upper eyelid, and spread over the surface of the eye by blinking. Subsequently the fluid either evaporates or is re-absorbed via small channels at the inner corner of the eye.
At times the lacrimatory ducts go into over-production and excess, liquid tears pour out of the eye. This happens in response to irritation, when the tears serve to wash chemical or small particle irritants away from the sensitive eye. For reasons unknown, humans, unlike other animals (even crocodiles) lacrimate excessively in response to pain, sadness or extreme mirth. This appears to be a partly voluntary response. All healthy babies do it, but the function is often suppressed in male humans from a relatively early age, after which male crying is only tolerated in response to football matches. Women, on the other hand, are able to use crying as a diversionary tactic aimed at taking the moral high ground during any argument.
When humans eat, they inevitably consume quantities of air along with their food. Indeed, some beverages are preferred precisely because they contain dissolved CO2 (eg, beer, sparkling wine, Irn Bru) which is released into the stomach in gaseous form. Air can also become trapped by food as it enters the stomach. In small quantities, stomach gases can be passed downstream into the intestines. Eructation (belching or burping) occurs when it emerges upwards through the oesophagus and is released orally.
Eructation is a deceptively complex activity, requiring the coordination of several activities. The larynx must be closed off so that any liquid or food that might return with the air from the stomach won't get into the lungs. This is accomplished by voluntarily raising the larynx as is done when swallowing. Raising the larynx also relaxes the upper oesophageal sphincter so that air can pass more easily from the oesophagus into the throat. The lower oesophageal sphincter must open so that air can pass from the stomach into the oesophagus. While all this is occurring, the diaphragm descends just as it does when a breath is taken. This increases abdominal pressure and decreases pressure in the chest. The changes in pressure promote the flow of air from the stomach in the abdomen to the oesophagus in the chest.
Complexity notwithstanding, the erucatatory process is largely voluntary - humans are generally able to suppress the release of air by control of the oesophageal sphincter. However, the willingness to do so is governed by cultural expectations. In some cultures, public eructation following a meal is regarded as a well-mannered token of appreciation. Even in more inhibited cultures, approbation is mild and children are encouraged only mildly to control their eructations with rhymes such as
Pardon me for being so rude
It was not me it was my food
It just came up to say hello
And now it's gone back down below!
Flatulation (or flatulence) is generally regarded with less tolerance than eructation. Of all global cultures, it seems to be only English-speaking males that regard farting as marvellously funny and socially acceptable. Indeed, the flatulence joke has a respectable literary pedigree11. A possible exception to this is the French. In the late 19th to early 20th Century, an artiste by the name of Joseph Pujol performed dazzling feats of flatulatory virtuosity on the music hall stage - but he found his greatest fame was in England where he farted before royalty12.
Flatulation is the release of gaseous material from the lower intestinal tract via the anus. It is often accompanied by a whistling or rasping noise, caused by vibration of the anal sphincter. The gases released consist of approximately 90% ingested air (see Eructation) and 10% the products of intestinal fermentation of foodstuffs. These fermentation products include relatively high proportions of methane (CH3) and hydrogen (as well as CO2). Thus many a jolly time can be had by rugby players demonstrating the inflammable nature of this gaseous mixture.
The social unacceptability of public flatulation is due to the foul smell of the discharged gases. The intestinal breakdown of proteins contributes various odiferous compounds, including butyric acid (CH3CH2CH2-COOH)13, hydrogen sulphide (H2S) and carbon disulphide (CS2)14.
While flatulation can largely be controlled by those who wish to (although sometimes you'd hardly believe it) by voluntary tightening of the anal sphincter, unwanted release is not uncommon. The odour can be denied - but for those who are unable to control their anus and who do not wish to risk the potential embarrassment of noisy discharge, the following extraordinary advice is offered:
In social situations where the sound of flatulence would be particularly inappropriate a temporary remedy can be obtained by placing a piece of cotton wool or paper tissue about 4cm in diameter onto the anus. If this is done whilst squatting then closure of the buttocks will hold it in place for a considerable period of time. This keeps the anus dry and reduces the velocity of the gas discharge, both of which prevent noisy events15.
An alternative to this somewhat extreme measure is to dissemble vigorously and blame it on the dog.
What goes down may come up. Partially-digested food may on occasion be discharged vigorously upwards through the oesophagus and mouth (and, indeed, the nose!). In evolutionary terms, vomiting presumably developed as a protective mechanism against poisons. It can also be triggered by other causes (eg, gastritis), including those not directly linked to digestive tract function (eg, motion sickness, brain tumour). Small humans also regurgitate milk frequently, but this is generally considered to be normal, if inconvenient.
Vomiting consists of a combination of clever tricks. The basic regurgitative manoeuvre consists of an increase in abdominal pressure by tightening the abdominal muscles, accompanied by a lowering of intrathoracic (chest) pressure by inspiration against a closed glottis. This propels the stomach contents outwards, often with great force. In preparation, vomiting is ordinarily preceded by retching, whereby muscular spasms build up pressure within the chest cavity before transferring it to the abdomen by action of the diaphragm. Sometimes, during sustained vomiting, intestinal material is carried into the stomach by retroperistalsis. This is the reverse of peristalsis, the involuntary wave-like motion of the muscles surrounding the gastro-intestinal tract which conveys foodstuff downwards from the stomach, through the intestines and outwards (see Defecation). This is not always the case, however. For example, during a migraine, the gastro-duodenal sphincter is sometimes tightened at the onset of an attack, and the day's food intake is regurgitated from the stomach in reverse order. Regurgitation is also accompanied by an increase in salivation which protects the enamel of the teeth from the strongly acidic contents of the stomach.
Human distaste for vomit - especially other people's - is probably matched only by that for faeces. Nevertheless, public vomiting is far more tolerated than public defecation, and indeed the vomiter is generally accorded sympathy, being the sufferer of a disease process. This tolerance is stretched somewhat by the public vomiting that occurs in any British town centre on Friday and Saturday nights as the inevitable result of alcoholic overconsumption by youths. The strongest prohibition against vomiting is in taxis where it results in severe financial penalties. Parents, however, are highly tolerant of the vomit of their offspring. One definition of a parent is 'Someone who is prepared to catch a child's vomit in her hands'. Another is 'Someone who can see someone else catching a child's vomit and still carry on eating'.
Urine is a clear, amber solution of the waste product resulting from the filtration process that takes place in the kidneys. In order to survive, human bodies need to keep fluid and electrolyte balances and vital acid-base levels regulated within very narrow limits. The kidneys carry out this task using filtration and re-absorption processes.
Humans produce about 13 billion litres of urine every day16 - certainly a lot of pee but only equivalent to about 6% of the flow over Niagara Falls. This golden fluid - the product of the prodigious, silent labours of the kidneys - gathers in the urinary bladder, a hollow muscular organ, the shape and size of which varies according to the amount of urine it contains; when empty it is tetrahedral and when full ovoid. The desire to urinate or micturate begins when the content reaches 400ml but can be overridden until the content reaches about 800ml. It is a complex activity partly unconscious (controlled by lower spinal cord centres) and partly conscious (controlled by the higher brain centres). Messages from the brain stimulate the detrusor or emptying muscles of the bladder, relaxing both urethral sphincters. Evacuation is assisted by the abdominal wall contracting, the diaphragm descending, the breath being held and the perineal floor relaxing. Once begun urination is carried through to completion by higher and lower centres acting in concert and messages sent from the urethra distended by the flow of urine - all this often accompanied by a heartfelt 'Ahhhh!'
In Western culture, men urinate standing up and women sitting down, a custom that leads to much friction between the sexes regarding the resulting position of the toilet seat and men's inability to accurately aim a stream of urine. However in men's defence the evidence of a mis-hit only becomes evident when the light, straw-coloured healthy urine dries to a deeper yellow stain on the rim.
The greater directability of urinary flow afforded by the nozzle-like penis allows men to achieve various prestigious feats undreamt of by women, such as the ability to put out fires, to write their names in the snow and to settle disputes of social hierarchy ('pissing contests'). Some psychologists have even suggested a link between the learning in urinary directional control in males and higher scores in tests of visuo-spatial ability (and, more controversially, superior educational attainment in science and engineering).
Defecation is the process of eliminating solid or semi-solid waste via the lower opening of the digestive tract. The act is generally regarded with cultural distaste. A permissible euphemism is 'having a poo'.
Faecal matter, consisting of largely of digested food waste, but also possibly including undigested foods (typically, sweetcorn) or other swallowed matter is carried through the colon by the peristaltic wave. As the rectum fills up, a feeling of rectal fullness signals the need to defecate. When the rectum is full, pressure forces the walls of the anal canal apart allowing the fecal matter to enter. The rectum shortens as material is forced into the anal canal and peristaltic waves push the faeces out of the rectum. The internal and external sphincters of the anus allow the faeces to be passed by muscles pulling the anus up over the exiting faeces. The pushing action is sometimes aided by a voluntary tightening of muscles to increase abdominal pressure. The defecator may strain considerably, making sounds and increasing blood pressure17.
Humans are fastidious about defecation and generally wish to perform the act in seclusion and in designated locations (this is probably innate; the same behaviour is found in other mammals). Thus the faecal matter is retained within the rectum by tension of the anal sphincter until a convenient opportunity can be found for release. Indeed, if an immediate opportunity is unlikely, humans can, by voluntary muscular action, pass the faecal matter upwards from the rectum and back into the colon.
Human fastidiousness has led to much ingenuity in the handling and treatment of faecal matter. In farming communities, the waste is often deposited in a place where it can be collected and used to fertilise crops or to provide a foodstuff for swine. In developed, urban cultures, sewage systems have been established which allow the waste to be deposited in water and swept away. Such sewers are known from various ancient cities, including Graeco-Roman, Indus and Inca sites.
Attention has also been given to the initial receptacles for the waste. In Western civilisation, the favoured receptacle is a porcelain cup-like device, approximately 38cm (15") high which facilitates defecation in a seated position. Generally these allow the faeces to drop straight into water - although in European models they drop onto a shelf where they can be inspected prior to being flushed away. Elsewhere, fittings are designed to facilitate the placement of feet around a cavity, to allow defecation in the more physiologically effective squatting position.
Humans also give attention to the removal of faecal matter from the area surrounding the anus, following defecation. Depending on environment, the most basic method for this involves rubbing with leaves, grass, sand or wood ash. Civilised cultures have developed various other methods including the use of hands and rounded pebbles (followed by hand washing and possibly the application of scented products), rubbing with a flimsy variety of paper and direct washing with jets of water. The preferred method is a matter of cultural difference18.
Despite (or, more likely, because of) ingrained defaecatory taboos, 'toilet humour' is popular. Certainly to young children, there are few if any topics more hilarious than poo-poos. The transgression of taboos probably also forms the basis of the erotic fetishes of coprophilia and coprophagy, over which it is better to draw a veil.
There are various human emissions which do not have their own convenient '-tion' word. For convenience, these are lumped together here. Strictly speaking, secretion is the release of a substance by any gland, internal or external19.
By far the most exciting of these processes is the mucal secretion from the vaginal walls of female humans. When a woman is sexually excited, she increases her rate of secretion of a slippery substance which serves as a lubricant in expectation of the insertion of an erect penis. The visual, tactile and olfactory sensations caused by the external leakage of this mucal substance is held by many to be arousing. In the 1960s, the pharmaceutical/chemical industries disastrously marketed 'vaginal deodorants' intended to disguise the scent of this secretion. Such products were ultimately unsuccessful because their masking effect tended to reduce rather than enhance feminine allure. In the present day, manufacturers of menstruation-related products have expanded into trying to convince customers of the need to wear panty liners to absorb these secretions, which seems somewhat to defeat the point of panties in the first place20. Some women, especially following the menopause, produce little vaginal secretion. Various lubricant products are available to allow chafe-free vaginal intercourse.
A further secretion which plays a significant role in human sexual behaviour is that from the apocrine glands. These are associated with hair follicles and exude small quantities of a sticky, milky substance. The odour of this secretion is sexually attractive and performs a similar function to that from the anal gland of the musk deer (Moschus Moschiferus) which is used as the basis for many perfumes. The apocrine glands are concentrated mainly in the axilla (armpit) and genital areas, where secretions become trapped by the relatively dense hairs growing there21. Apocrine glands are also found around the nipples and it is believed that their scent helps to guide babies towards their food source.
Apocrine glands, in combination with sebaceous glands, also perform a role in the formation of earwax (cerumen). Viscous secretions from the sebaceous glands combine with less viscous ones from the apocrine. The combination is genetically determined22. Earwax plays a role in maintaining the cleanliness of the ear canal. If it builds up excessively it occasionally drops out as a plug. Alternately, it may have to be removed artificially. Safety Note: The only object that may be safely inserted into your own ear is your elbow.
Sebaceous glands are also scattered around the skin, mainly associated with hair follicles, but also on the hairless skin of the lips, eyelids, penis, labia minora and nipples. In normal function, these secrete an oily, waxy substance called sebum, which waterproofs the hair and skin and keeps them supple. If a sebaceous gland becomes temporarily blocked or if a gland goes into over-production, a build-up of sebum results in a spot (US = zit; Scots = plook). In adolescents, hormonal changes trigger a general over-activity of the sebaceous glands, giving rise to the condition of acne. Contrary to popular belief, the sticky, yellow substance that has to be wiped off the mirror after a teenager has used the bathroom is not pus (see Suppuration) but sebum. In unborn humans, the sebaceous glands secrete a substance called Vernix Caseosa23, a waxy, white coating seen on the skin of the newborn.
This is the emission of blood from the body without prior mechanical puncture. It is a made-up term, to retain euphonic consistency with the other section headings.
There are various disease conditions, ranging from the mild to the severe, which can cause blood to leak. These include:
Gingivitis. Inflammation of the gums (gingiva), usually resulting from poor oral hygiene, may cause the gums to become red, swollen, and spongy, and bleed easily. Bleeding may be noticed on rinsing the mouth following tooth brushing or flossing.
Epistaxis. The surfaces of the nasal passage contain many delicate blood vessels which can puncture spontaneously, especially when the tissues are dried out in conditions of low humidity, inflamed by illness or allergy or disturbed by vigorous sternutation.
Haemorrhoids (or piles) are enlarged veins in or around the anus, appearing as small, purple 'grape-like' clusters. They can become damaged during defecation, especially by hard, constipated faeces, and bleeding occurs from the anus.
Severe gastric ulceration or other gastric disease (eg, tumours) can cause blood to be regurgitated.
Severe respiratory tract disease (eg, tuberculosis) can cause blood to be expectorated from the lungs.
Blood may be passed along with urine as a result of urinary tract disease or kidney stones.
A more disputed variety of spontaneous exsanguination is stigmata. Some members of the Christian faith believe that marks corresponding to Christ's injuries on the cross can spontaneously appear on the hands, feet and torso of favoured believers. These can sometimes even leak blood. Although there is no scientific evidence for this phenomenon (where such wounds do present, hysterical self-infliction is a more plausible explanation), it is taken seriously by many figures with political power. Recent figures who have claimed to have stigmata include Padre Pio (1918-1968), who gave his name to a variety of non-lethal punishment shooting favoured by PIRA vigilantes.
Suppuration does not occur in healthy humans. However, disease or wound processes may cause a discharge of pus, a mixture of white cells, cellular debris and decomposed tissue. There's very little interesting or amusing that can be said about suppuration24. Conventional treatments for suppuration involve keeping wounds and abscesses dry and application of antibiotics and antiseptics. More recently, some success has been found with the use of honey (which has antiseptic properties)...and with introducing maggots into wounds.
So, there we have it. Much though we may like to think of the human species as capable of great wonders, an alternate view of us is as a source of stains. We have nothing to offer but blood, sweat and tears. And vomit. And faeces. And urine. And mucus. And semen...etc. etc. But don't be ashamed of your body - this one will run and run!