By N. Olivier. University of Houston, Downtown.
Approximately 3 Physiology of the Ear The pinna which plays a role of sound collec- The tympanic membrane and ossicles not only tion in some lower animals does not seem to conduct the sound but also increase its play this function in human beings discount priligy 30 mg overnight delivery. The perceptive neural mechanism which overcomes this resistance by increas- (transduction) buy 30mg priligy. The greater length of the handle of Functions of the Middle Ear Muscles malleus compared to the long process of The basic function of the intratympanic incus (1 buy generic priligy 90mg line. Loud sounds reflexly The result of the two gains, the hydraulic stimulate the muscles, which cause stiffness ratio and the ossicular lever ratio (17 × 1. As these muscles This is how the middle ear functions as the have a latent period of contraction of 10 msec, sound pressure transformation mechanism these do not provide protection from sudden and helps in impedance matching of the explosive sounds. The reconstruction of the middle ear trans- Eustachian tube helps in aeration of the former mechanism and round window middle ear. Normally, an aerated middle ear protection form the principles of tympa- cavity is essential for proper functioning of the noplasty. Besides air conduction, the sounds are also The eustachian tube helps in equalisation transmitted through bone, which may be due of pressure in the middle ear. As the atmos- to vibration of the skull by the subject’s own pheric pressure decreases, as during ascent in sound waves, the free-field sound energy or an aeroplane, the air in the middle ear by application of the vibrating body directly cavity gets absorbed and a negative pressure to the skull. This can The stimulation of the sense organs by the be equalised by frequent swallowing move- bone conducted sounds occurs as a result of ments which open the eustachian tubes. Physiology of the Ear 25 Functions of the Mastoid Cellular System The function of cellularity of the mastoid is not very clear. It may be insulating chambers protecting the labyrinth from temperature variations. Volley theory (Wever’s theory): This theory The organ of Corti gets stimulated and results is a combination of place and telephonic in generation of cochlear microphonics. The low tones displace the whole of the basilar Pitch Discrimination in the Cochlea membrane and are represented in the There are different theories of hearing which auditory nerve by nerve fibre responses. Place theory (Helmholtz’s theory): According to this theory, the perception of pitch The vestibular system plays a role in main- depends on movements of the point of taining equilibrium in addition to visual and maximum displacement of the basilar proprioceptive mechanisms. Thus each pitch would cause Semicircular canals The canals are sensitive to vibration of its own place on the basilar changes of angular velocity. During angular theory assumes that pitch discrimination acceleration or deceleration, the endolymph depends upon the rate of firing of the due to its inertia lags behind and thereby action potentials in the individual nerve exerts pressure within the ampulla. As soon fibres, the frequency analysis is then done as the constant velocity of rotation is attained by the central nervous system. Once angular acceleration or decele- statoconial membrane, which is responsible ration ceases, the endolymph being still in for static labyrinthine reflexes resulting from motion, stimulates the crista ampullaris but centrifugal forces and also responsible for in the reverse direction. Utricle The hair cells of the utricular macula There is a constant discharge from the are stimulated by the gravitational pull on vestibular labyrinth conducted through the Physiology of the Ear 27 eighth nerve to the central vestibular connec- of the whole, which can still be elicited for tions which keep the cortex informed about several hours after total oxygen depriva- the changes in position and posture of head tion or death. This means that a sound wave as such does not potentials of the individual nerve fibres. There are several forms of sound distortion to which the ear, in common with other acous- Masking tic devices, is subjected. These are as follows: The masking of a tone by a louder sound of Frequency distortion The “preferential” trans- approximately similar frequency is called mission of certain frequencies as compared to ipsilateral direct masking. This mechanism is others occurs when the secondary system into independent of the central nervous system. Both simple and comp- mingling of the central connection of the two lex wave motions can be affected by ampli- ears. History of drug intake: Drugs like salicylates, aminoglycosides, quinine and cytotoxic Deafness or hearing impairment is an impor- drugs are known to be ototoxic. The various points to be noted are roundings are more prone to hearing the following. Duration: Deafness which is present since hearing if he or she has a hearing loss which birth may be due to genetic causes, due to can be helped by medical and/or by surgical prenatal intake of drugs like thalidomide treatment, or has learned speaking naturally or if the mother suffered from rubella as a partially hearing child or adult. Prolonged labour and tation measures like providing amplification otitis media, measles, mumps and menin- (hearing aid), and speech and auditory train- gitis during infancy are also important ings can help in restoring verbal communi- causes of deafness. Provided the treatment is started early Deafness of recent origin in adults may in life, such a person can be educated with be due to traumatic, inflammatory, neo- normal hearing children and in later life will plastic, vascular and metabolic causes. In has a severe hearing loss with little or no cochlear lesions patients do not hear at residual hearing. Such a person’s hearing is conversational intensity but get irritated by nonfunctional for ordinary purposes of life. When measured with an audiometer the Fluctuant deafness occurs in secretory hearing loss for speech is 82 dB or worse otitis media and Ménière’s disease. A deaf 30 Textbook of Ear, Nose and Throat Diseases person should be educated and trained in a may also be due to the infections of the exter- deaf school. The discharge may be serous, mucoid, mucopurulent, purulent, Tinnitus blood stained, or watery. Tinnitus is first important symptom of sali- Serous discharge is found in allergic otitis cylate poisoning. Mucopurulent discharge is com- periodic episodes of deafness and vertigo monly due to benign chronic suppurative constitutes Ménière’s syndrome. Wax in the otitis media and the extension of the disease external auditory canal, aero-otitis media, process to mastoid air cells. A purulent dis- infections of the ear, acoustic trauma and charge usually signifies an underlying bone otosclerosis may be associated with tinnitus. This type in ears and tinnitus are found in secretory of discharge may occur in otitis externa also. Blood-stained discharge is a feature of Vertigo malignancy, glomus jugular and granulations. The first thing to ascertain is whether the vertigo is Earache (Otalgia) really vertigo (a sense of rotation) or a synco- Pain in the ear may occur due to lesions in the pal attack in which the patient gets a blackout, ear itself or due to the conditions in the sur- falls momentarily and quickly regains con- rounding areas (referred otalgia) (Fig. Painful lesions of the ear include the Vertigo with a discharging ear indicates following: labyrinthitis. Via the greater auricular nerve and facial nerve: Cervical spine lesions, neck lesions (inflam- matory, traumatic, neoplastic, etc. Nasopharyngeal lesions: Carcinoma, tory otitis media or as a complication adenoid hypertrophy.
Milk yields should improve priligy 30 mg mastercard, while breeding and improved management should increase average carcass weights and off-take rates discount 60 mg priligy with amex. This will allow increased production with lower growth in animal numbers buy 30 mg priligy mastercard, and a corresponding 26 slowdown in the growth of environmental damage from grazing and animal wastes. In developing countries, demand is predicted to grow faster than production, resulting in a growing trade deficit. An increasing share of livestock production will probably come from industrial enterprises. In recent years, production from this sector has grown twice as fast as that from more traditional mixed farming systems and more than six times faster than that from grazing systems. World fisheries production has kept ahead of population growth over the past three decades. Total fish production has almost doubled, from 65 million tonnes in 1970 to 125 million tonnes in 1999, when the world average intake of fish, crustaceans and molluscs reached 16. By 2030, annual fish consumption is likely to rise to some 150-- 160 million tonnes, or between 19--20 kg per person. This amount is significantly lower than the potential demand, as environmental factors are expected to limit supply. During the 1990s the marine catch levelled out at 80--85 million tonnes per year, and by the turn of the century, three-quarters of ocean fish stocks were overfished, depleted or exploited up to their maximum sustainable yield. Aquaculture compensated for this marine slowdown, doubling its share of world fish production during the 1990s. It is expected to continue to grow rapidly, at rates of 5--7% per year up to 2015. In all sectors of fishing it will be essential to pursue forms of management conducive to sustainable exploitation, especially for resources under common own- ership or no ownership. Most of the information on food consumption has hitherto been obtained from national Food Balance Sheet data. In order to better understand the relationship between food consumption patterns, diets and the emergence of noncommunicable diseases, it is crucial to obtain more reliable information on actual food consumption patterns and trends based on representative consumption surveys. There is a need to monitor how the recommendations in this report influence the behaviour of consumers, and what further action is needed to change their diets (and lifestyles) towards more healthy patterns. The implications for agriculture, livestock, fisheries and horticulture will have to be assessed and action taken to deal with potential future demands of an increasing and more affluent population. To meet the specified levels of consumption, new strategies may need to be developed. For example, a realistic approach to the implementation of the recommendation concerning high average intake of fruit and vegetables, requires attention to be paid to crucial matters such as where would the large quantities needed be produced, how can the infrastructure be developed to permit trade in these perishable products, and would large-scale production of horticultural products be sustainable? A number of more novel matters will need to be dealt with, such as: 7 the positive and negative impacts on noncommunicable diseases of intensive production systems, not only in terms of health (e. Trade aspects need to be considered in the context of improving diet, nutrition and the prevention of chronic diseases. On the import side, lower trade barriers reduce domestic food prices, increase the purchasing power of consumers and afford them a greater variety of food products. Freer trade can thus help enhance the availability and affordability of food and contribute to a better-balanced diet. On the export side, access to markets abroad creates new income opportunities for domestic farmers and food processors. Farmers in developing countries in particular stand to benefit from the removal of trade barriers for commodities such as sugar, fruits and vegetables, as well as tropical beverages, all these being products for which they have a comparative advantage. The impact that agricultural policies, particularly subsidies, have on the structure of production, processing and marketing systems --- and 28 ultimately on the availability of foods that support healthy food consumption patterns --- should not be overlooked. All these issues and challenges need to be addressed in a pragmatic and intersectoral manner. All sectors in the food chain, from ‘‘farm to table’’, will need to be involved if the food system is to respond to the challenges posed by the need for changes in diets to cope with the burgeoning epidemic of noncommunicable diseases. Rome, Food and Agriculture Organization of the United Nations/London, Earthscan, 2003. Structural change in the impact of income on food consumption in China 1989--1993. The environmental impact of olive oil production in the European Union: practical options for improving the environmental impact. New Delhi, Department of Women and Child Development, Ministry of Human Resource Development, Government of India, 1998. Risk behaviours, such as tobacco use and physical inactivity, modify the result for better or worse. All this takes place in a social, cultural, political and economic environment that can aggravate the health of populations unless active measures are taken to make the environment a health-promoting one. Although this report has taken a disease approach for convenience, the Expert Consultation was mindful in all its discussions that diet, nutrition and physical activity do not take place in a vacuum. Since the publication of the earlier report in 1990 (1), there have been great advances in basic research, considerable expansion of knowledge, and much community and international experience in the prevention and control of chronic diseases. At the same time, the human genome has been mapped and must now enter any discussion of chronic disease. The influences in the womb work differently from later influences, but clearly have a strong effect on the subsequent manifestation of chronic disease. The known risk factors are now recognized as being amenable to alleviation throughout life, even into old age. The continuity of the life course is seen in the way that both undernutrition and overnutrition (as well as a host of other factors) play a role in the development of chronic disease. The effects of man-made and natural environments (and the interaction between the two) on the development of chronic diseases are increasingly recognized. Such factors are also being recognized as happening further and further ‘‘upstream’’ in the chain of events predisposing humans to chronic disease. All these broadening perceptions not only give a clearer picture of what is happening in the current epidemic of chronic diseases, but also present many opportunities to address them. The identities of those affected are now better recognized: those most disadvantaged in more affluent countries, and --- in numerical terms far greater --- the populations of the developing and transitional worlds. There is a continuity in the influences contributing to chronic disease development, and thus also to the opportunities for prevention.
Transient skin discoloration is seen in methaemoglobinaemia and sulphaemo- globinaemia due to dapsone administration discount priligy 30mg visa. Café au lait patches are part of neuroﬁbromatosis (Von Recklinghausen’s disease 60mg priligy for sale, see page 199) buy 90mg priligy with amex. Not dissimilar brown macules are found on the lips and around the mouth and on the ﬁngers in Peutz–Jeghers syndrome, accompanied by small-bowel polyps, and in Albright’s syndrome, in which there are associated bone abnormalities. This facial pigmentation may be part of the increased pigmentation of pregnancy or may occur independently. The cheeks, periocular regions, forehead and neck may be affected in this so-called ‘mask of pregnancy’ (Fig. Post-inﬂammatory hyperpigmentation may be due to melanocytic hyperplasia occurring as part of epidermal thickening in chronic eczema, particularly atopic eczema. It may also be due to the shedding of melanin from the damaged epidermis into the dermis, where it is engulfed by macrophages. Albinos ● Dark pigmentation due to non-melanin pigments have fair skin, white/yellow hair and light-blue eyes. It affects 1–2 per cent of the population facial pigmentation; a golden-yellow colour is and appears to be autoimmune in origin. A more diffuse type ● Generalized hyperpigmentation (including the of facial hyperpigmentation that is mostly seen in mucosae and nails) due to excess pituitary women is known as chloasma. Instead of the message, ‘Here is a healthy, harmless member of the human race’, the signal from an abnormal skin is interpreted as announcing, ‘Beware of the contagion’. There is a primitive dislike and distrust of individuals with skin disease or skin deformity. Skin problems seem to engender genuine fear and revulsion, perhaps as a hangover from primitive stages of human develop- ment when the avoidance of people with infected of infested skin had a survival advantage. Interestingly, patients with obvious skin disease are also very disturbed by its appearance and tend to shun the company of others and become quite isolated. Reassurance and the use of prostheses, hairpieces and cosmetic camouﬂage should be encouraged rather than sneered at. Patients with obvious disease of exposed areas, widespread skin disease and persistently itchy skin become depressed and need sympathy and general support, but some may need psychotropic drugs and psychiatric help. The major exception is dermatitis artefacta, a skin disorder that is entirely self- induced. The degree of insight varies among patients: some admit scratching, picking or rubbing, but say they are unable to stop doing it; others hotly deny pro- ducing the injury to the skin. At one end of the scale, nodular prurigo (see page 120) can be said to be a form of dermatitis artefacta. At the other end of the scale, there is a devastating injury resulting in serious permanent disability (Fig. Psychotherapy and psychotropic drugs appear to offer very little and the artefacts may persist for years. Often, sufferers will bring to the doctor rolled up horn or other skin debris and point proudly to the ‘infesting insect’. These patients’ beliefs 304 Topical treatments for skin disease are quite unshakeable, and beyond psychiatrists’ help. The drug pimozide has been said to be helpful for patients with delusional parasitosis. Curiously, some individuals have a distorted body image amounting to a delusional belief. Too much hair, too little hair, discolorations and minor blemishes can all become a major focal point of complaint. Skin disability Skin disease can be as disabling as disease of other organ systems. Disability from skin disease consists of physical, emotional and social components. The physical disability derives from decreased mobility due to the abnormal stratum corneum present in eczema, psoriasis or the ichthyotic disorders. The emotional disability stems from the psycho- logical problems discussed above and can lead to serious depression and its conse- quences. The social disability stems from the ‘isolation’ imposed by both the patients themselves and society at large. Topical treatments for skin disease Drugs for use topically are incorporated into vehicles, which include greasy single- phase ointments, creams, which are mostly oil in water, or water in oil emulsions or aqueous lotions. Pastes are thick substances containing a particulate solid phase; alcoholic lotions have some limited use, for example for scalp treatments; gels are semi-solid, translucent water-ﬁlled or alcohol-ﬁlled matrices, which are quite useful at times, for example for scalp disorders. In general, ointments are prescribed for chronic scaling conditions, including pso- riasis and persistent eczema; creams and lotions are prescribed for acute and exuda- tive disorders. When the disorder is weeping and exudative, bathing and wet dressings are required. Gauze dressings kept moist with saline or dilute potassium perman- ganate solution (1:8000) or aluminium subacetate solution (8 per cent) should be used. It takes about 25 g to cover the body completely on one occasion with a cream or ointment; 50 g would be sufﬁcient for a topical treatment for a bilateral hand dermatitis for a month. Emollients may be single-phase oils or greasy oint- ments, oil-in-water or water-in-oil emulsions, either as creams or lotions. They: ● make the stratum corneum swell and ﬂatten so that the skin looks and feels smoother ● increase the extensibility of skin so that it cracks less ● decrease binding forces between the horn cells and decrease scaling ● decrease itch ● have some intrinsic anti-inﬂammatory properties, decrease epidermal mitotic activity and have anti-prostaglandin synthetase activity. Their predominant use is for eczematous dermatoses, but they are also useful in psoriasis. A major part of their action is in inducing lipocortin – the endogenous inhibitor of phospholipase A2 – which is important in the generation of eicosanoid compounds involved in the inﬂammatory process. Dilution of proprietary preparations is not advised because the formula- tions are complex and the important excipients are also diluted and may be inef- fective when the dilution is made. Case 22 Jeremy, aged 9, had had eczema since he was a few weeks of age, but it had markedly worsened in the past 4 months, as had his asthma. He started to improve when he was treated regularly with emollients two or three times per day. He was also helped by the use of a weak corticosteroid (clobetasone butyrate) twice daily and a strong corticosteroid applied to the sites where there was severe eczema (mometasone furoate) once daily. Care was taken to ensure that he did not use excessive amounts of corticosteroids, in order to avoid the problems of skin thinning and pituitary–adrenal axis suppression. Amongst the safest and most useful compounds for bacterial and fungal infec- tions are the imidazoles (e.