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Types of blood vessels in the circulatory system and their important properties Artery Elastic arteries - Tunica media is rich in elastin fbers e synthroid 200 mcg free shipping symptoms in children. Aorta and its large branches Muscular arteries - Tunica media is rich in smooth muscle cells e order 25 mcg synthroid otc treatment 7. The normal blood vessels particularly the arteries have an elastic recoil property referred to as the ‘Windkessel effect’ buy synthroid 75mcg without a prescription treatment juvenile arthritis. This effect is responsible for maintaining the blood fow inside the vessels during the diastolic phase of cardiac contraction purchase synthroid 100 mcg line medicine man movie. Arteriolosclerosis - It affects small arteries and arterioles, it can be of the following types: Hyaline arteriolosclerosis Concept • Pink, hyaline thickening of arteriolar walls. Monckeberg’s medial calcifc stenosis – Seen is muscular arteries of people > 50 years of age. Atherosclerosis It is characterized by deposition of atheroma/fbrofatty plaque consisting of raised focal lesion. Plaque is present within the intima, has a core of lipid (cholesterol and cholesterol esters) and a covering of fbrous cap. Risk factors for atherosclerosis (Mnemonic: Atherosclerosis) Coronary circulation is an A - Age (↑ with age) example of autoregulatory circulation. So, it competes with plasminogen in clots pathogenesis decreasing the latter’s ability to form plasmin and clear clots. It is best explained by the ‘Response to Injury Hypothesis’Q Increased Lp(a) levels are associated with a higher risk of According to this hypothesis, chronic endothelial injury results in increased permeability, coronary and cerebrovascular leukocyte adhesion and thrombotic potential. The activated platelets release factors causing migration of smooth muscle cells from the media to intima and their proliferation along with release of proteoglycans and collagen. In advanced atheroma, the smooth muscle cells may Smooth muscles cells/Tissue undergo apoptosis and so, smooth muscle cell paucity may be observed. It begins as yellow fat spots less than 1 mm which gradually progress to atheroma formation. Fatty streak is the earliest Signifcance of involved blood vessels in atherosclerosis lesion of atherosclerosis. True aneurysm: Involves intact attenuated arterial wall or thinned ventricular Ulceration, wall of the heart. False/Pseudo- aneurysm: It is characterised by a breach in the vascular wall leading to extravascular hematoma communicating with intravascular space. Atherosclerosis *It is the most common cause of true aneurysm in aorta Atherosclerosis causes *The most commonly affected vessel is the abdominal aorta (below the origin of abdominal aortic aneurysm. Syphilis *The thoracic aorta is involved in tertiary stage of syphilis *Endarteritis of vasa vasorum results in patchy ischemia of tunica media. This is responsible for the often seen “tree barking” appearance of the thoracic aorta. Other causes Trauma; infection (mycotic aneurysm; mostly due to Salmonella gastroenteritis) and systemic disease (vasculitis) Other important points about different causes of aneurysms • Cystic medial necrosis is characterized by weakness due to media due to degeneration of the tunica media and it affects the proximal aorta. It is mostly seen in men in the age group of 40- 60 years (with antecedent hypertension) and uncommonly in younger individuals with connective tissue disease (Marfan’s syndrome). Medial degeneration is a characteristic pre- existing lesion in most of the patients. Type B - Does not involve ascending aorta but lesion begins distal to subclavian artery. It may be classifed on the basis of pathogenesis or on the basis of size of the involved vessel. Giant cell (Temporal) arteritis/Cranial arteritis common type of vasculitis in adults. Since the superfcial temporal arteryQ is the most commonly involved vessel, the giant cell arteritis is called as temporal arteritis. The subclavian artery is most – Clinical features include weak pulses in the upper limbs (so, the disease is commonly involved vessel in also called as pulseless diseaseQ), ocular disturbances, hypertension and Takayasu arteritis. Kawasaki’s disease (Mucocutaneous Lymph Node Syndrome) – It is the vasculitis affecting children < 5 yearsQ of age. It is characterized by fever, conjunctivitis and oral erythema, skin rash often with desquamation, erythema of palms and soles and cervical lymphadenopathy. There is typically intimal proliferation and mononuclear infltration of vessel wall. Hypersensitivity vasculitis/Cutaneous vasculitis • Defned as infammation of the blood vessels of the dermis. Churg-Strauss syndrome (Allergic granulomatosis and angiitis) Lastest Information (9th Edn. Wegener’s granulomatosis (Granulomatosis with polyangitis) Necrotizing vasculitis which is characterized by triad of 1. Acute necrotizing granulomas of either upper (more commonly) or lower respiratory tract or both. Focal necrotizing or granulomatous vasculitis most commonly affecting lungs and upper airways. Renal involvement in the form of focal necrotizing, often crescentic glomerulonephritis. Also Know • Secondary Raynaud’s phenomenon patients are older in age and have more severe symptoms and complications • More commonly have dilatation of the capillary bed at the base of the fngernails. Buerger’s disease (Thromboangiitis obliterans) Segmental thrombosing vasculitis • It is usually seen among heavy cigarette smokers. Q • This patient has distal lower extremity vascular insuffciency which may present as Calf, foot or hand intermittent claudication, superfcial nodular phlebitis and cold sensitivity (Raynaud’s phenomenon). Capillary hemangioma • It is the most common type of vascular tumor which occurs in skin, mucus membrane Strawberry hemangioma is a and viscera. Cavernous hemangioma – It is less common than capillary hemangioma with same age and anatomic Cavernous lymphangioma occurs distribution. It more frequently involves deep structures as it shows no tendency in Turner’s syndrome at the to regress. Pyogenic granuloma It is a polypoid form of capillary hemangioma seen attached by a stalk to skin or oral mucosa. Granuloma gravidarum is present in the gingiva of pregnant women and it regresses after delivery. Cavernous lymphangioma (also called as cystic hygroma) Capillary lymphangioma is dis- • This is present in the neck region of the children. Capillary Lymphangioma It is a lesion composed of small lymphatic channels occurring subcutaneously in the head and neck region and in the axilla. Hemangiopericytoma • Tumor derived from pericytes which are the cells present along the capillaries and venules. The (b) Libman Sacks endocarditis histopathological examination is most likely to show (c) Rheumatic heart disease which of the following?
Fungal infection may manifest itself in four dif- ferent clinical syndromes: Skin tests aspergillus hypersensitivity lung disease Tuberculin skin testing has a significant false-nega- aspergilloma tive rate in immunosuppressed individuals purchase 50 mcg synthroid with mastercard medications help dog sleep night. Clinical diagnostic indicators Sputum microscopy and culture The main symptoms are cough discount synthroid 125 mcg free shipping permatex rust treatment, haemoptysis (which Organisms may be visible with microscopy using a may be massive) buy 25 mcg synthroid with amex symptoms webmd, dyspnoea and chest pain buy synthroid 125mcg free shipping medications not to be taken with grapefruit. Blood tests The culture of infected sputum, bronchial wash- ings or lymph node biopsies takes several weeks to Aspergillus immunoglobulin (Ig)G antibodies indi- yield results. Bacteriology Culture of sputum and bronchial washings may Management also confirm the diagnosis. Tissue biopsy Surgery is now rarely used except for the man- Histopathology should demonstrate the character- agement of complications such as: istic hyphae. These drugs may Non-small cell lung cancer 309 be given intravenously or locally (i. Around 40000 new patients are diag- Pancoast tumour) nosed each year, of whom less than 5 per cent will dyspnoea and chest pain (phrenic and survive 5 years. It Lung cancer commonly metastasizes to the may show a lung mass, lobar collapse, pleural effu- mediastinal lymph nodes, the liver, the adrenal sion, mediastinal lymphadenopathy, diaphragmatic glands, bone and the brain. Not only does it Clinical diagnostic indicators suggest a diagnosis, but can be used to stage the Patients with operable disease are often symp- cancer and direct the most appropriate method of tomless, their lung cancer having been picked up biopsy. Furthermore, two mediastinal lymph nodes are also ‘hot’, precluding radical treatment if confirmed as metastatic disease. However, false positives are seen with infec- underwent a pneumonectomy for confirmed non-small cell tion, inflammation, rheumatoid nodules, sarcoid, cancer (see Fig 14. A more sophisticated method of determining fitness Invasive staging of the mediastinum. Lung function tests Conservative treatment Postoperative morbidity and mortality is dependent Best supportive care is reserved for those patients on the predicted postoperative pulmonary function with a performance status so poor that they would and the peri-operative cardiovascular fitness. Ultimately, however, this depends on the The peri-operative mortality is 2–3 per cent for a fitness of the patient (see above). One of the dreaded complications of a pneu- Some central tumours will require a pneumon- monectomy is dehiscence of the bronchial stump ectomy (removal of the entire lung) (Fig 14. This may occur in the first 2 weeks and a small peripheral tumour, a lesser resection such as a simple mechanical breakdown, resulting in as a segmentectomy (anatomical removal of a lung aspiration of the fluid in the pneumonectomy segment) or wedge resection may suffice. Long-term survival is stage dependent (particu- larly nodal stage) and is summarized in Table 14. An incomplete resection will adversely affect sur- vival and these patients should be offered adjuvant radiotherapy. Radiotherapy Adjuvant radiotherapy should only be offered in cases of incomplete surgical resection. The right 3 (T1 to 4, N0 to 3, M0) 10–45% hemidiaphragm is elevated and the remaining space has 4 (T1–4, N0–3, M1) 5% filled with fluid Metastatic lung disease 313 Pancoast tumours (usually in combination with Management chemotherapy), where tumour size is reduced and Platinum-based chemotherapy is the mainstay of resection rates are improved. Results are inferior to In addition, those who respond to chemo- surgical resection with a 5-year survival of around therapy may also benefit from prophylactic cranial 20 per cent. Although it there is no advantage in giving it to patients with might appear counterintuitive to resect metastatic early cancers, i. The relevant tumour markers should be measured for initial assessment and post-operation follow-up. Instead, staging is classified previously treated cancer is a metastasis until proven according to whether the disease is limited (to one otherwise. Surgical resection is the mainstay of treat- Tissue biopsy ment as other treatment modalities are relatively Histological confirmation is not strictly speaking nec- ineffective. The mediastinum is the space between the thoracic inlet and the diaphragm, bounded laterally by the Mediastinoscopy left and right medial pleura. Anatomically, it is Routine mediastinoscopy is advocated by some often divided into superior, anterior, middle and surgeons as 10 per cent of patients will have other posterior compartments but a more useful surgical metastases in the mediastinal lymph nodes. Management The anterior compartment extends from the The indications for surgery are a low operative risk innominate (left brachiocephalic) vein to the dia- control of the primary tumour site, and the absence phragm and from the underside of the sternum to of extrapulmonary metastases. A stapled wedge mediastinal space but a potential space lateral to the resection or diathermy excision is therefore the vertebral column. Factors which indicate a mediastinal lymphadenopathy, often secondary to poor prognosis include: metastatic cancer (usually lung cancer) or infection but sometimes caused by other diseases such as more than one metastasis sarcoidosis, tuberculosis or lymphoma (Fig 14. Patients with multiple poor prognostic factors The causes of mediastinal masses are summa- should probably not be offered surgery. Germ cell tumour markers and lactate dehydroge- Clinical diagnostic indicators nase. Symptoms may include dyspnoea, cough, dys- phagia, chest or back pain, malaise, fevers and night Heaf test. It is most appearances may be diagnostic or indicate a very commonly performed on the left side for masses short list of differential diagnoses. Bronchoscopic examination of the tracheo- Thoracotomy is usually a last resort when acquir- bronchial tree is important whenever there is an ing a tissue diagnosis is essential. A thymoma is a tumour arising from thymic Oesophagoscopy is indicated for oesophageal tissue. Biopsies can be taken using endoscopic tumour occurring in the anterior mediastinum. Histologically they vary from being relatively benign to frank thymic carcinoma (Table 14. Tissue biopsy Thirty to 50 per cent of patients with a thymoma Not all mediastinal masses require surgery. Fine needle aspiration may be symptoms include vague respiratory symptoms, inadequate for making a definitive diagnosis. Transbronchial or transoesophageal abnormal degree of fatigue after repetitive exercise fine needle aspiration guided by these images can and often complain of drooping eyelids. Complications Tissue biopsy Operative complications include phrenic nerve and vascular injury. Postoperatively, the complications Biopsy of the mass is controversial as seeding of tend to be related to the median sternotomy (atel- the needle tract and in the mediastinum has been ectasis, pneumonia, sternal dehiscence). If the presumed thymoma is operable, Myasthenia gravis may emerge for the first time in surgical excision is preferable. Biopsy should be a minority of patients following resection and should reserved for inoperable tumours. Blood tests Results Full blood count and germ cell tumour markers Prognosis depends on the stage of the tumour, the should be obtained. Investigate for myasthenia histological classification and the completeness of the gravis (see later). In patients with inoperable tumours or the lack of physiological reserve to undergo surgery, radiotherapy may be given following treatment with chemotherapy. Chemotherapy The majority of thymomas are chemosensitive and some patients achieve complete remission from cytotoxics.
Of the 10 per cent who relapse order synthroid 75mcg online medications by class, 90 per cent resolve in a further 8–12 weeks but 50 per cent will suffer further relapse generic 200mcg synthroid with mastercard symptoms 4dp3dt. Conservative treatment consists of analgesia discount synthroid 25mcg on-line medicine 7 years nigeria, anti-inflammatory medication 100mcg synthroid treatment kidney failure, physiotherapy, selective nerve root injections/caudal epidural, all of which aim to reduce the inflammation around the nerve root sheath. The risks of lumbar microdiscectomy are small but include infection (wound, pyogenic discitis and epidural abscess), dural tear, vascular injury and recurrent disc prolapse. The causes L3/4→compression of L4 root→pain in the can be classified as congenital (achondroplasia with posterolateral thigh region and anteromedial short pedicles or other skeletal dysplasia – rare) and aspect of the lower leg, motor weakness of the acquired (degenerative – common). The narrowing quadriceps (knee extension) and absence of the of the spinal canal is described as being either in the knee jerk. The abnormality begins as degenerative changes within the disc cause a reduction of the disc Imaging height and posterior bulging of the annulus. The The investigation of a patient with sciatic leg pain reduction in disc height causes infolding of the liga- consists of the following. Plain radiographs are obtained to assess abnor- Degenerative osteoarthritic changes (hypertrophy malities of segmentation (in particular lumbosacral and osteophyte formation) result from the increased transitional vertebrae) and detect evidence of a loading of the facet joints. The combination of spina bifida occulta if surgical intervention is being these changes results in the typical trefoil-shaped considered. Bone and calcium metabolism 227 Normal Ultrasound studies of the circulation may be needed to exclude peripheral vascular claudication. Severe cases who fail to respond to conservative Caude treatment can be managed surgically with decom- equina Normal pression, which may be either open or distractive. Disc protrusion There is considerable argument within the lit- erature about the role of fusion at the time of an Spinal stenosis open decompression (fusion may be posterolateral or interbody). The indications for fusion include a Bulging degenerative spondylolisthesis, recurrent stenosis disc and a severe stenosis requiring complete facet joint removal with a resulting potential for instability. Distractive decompression involves placing a Thickened spacer between the spinous processes in order to ligamentum Facet joint indirectly decompress the canal by distracting the flavum hypertrophy segment. Calcium is subsequently be difficult but there are certain defining differences excreted in the kidney. Vitamin D is acquired via two sources: diet (vita- The neurogenic claudication distance is variable but min D3) and the conversion of 7-dehydrocholesterol the vascular claudication distance is relatively constant. This active metabolite can then act on the gut to increase calcium and phosphate reabsorp- Imaging tion and within bone to cause osteoid mineralization. Parathyroid hormone acts to Screening blood tests increase reabsorption of calcium in the kidneys and Exclude hyperthyroidism, Cushing’s disease, hae- stimulates osteoclastic activity, resulting in release matological disorders and malignancy: thyroxine, of calcium from bone. Calcitonin is a 32 amino acid polypeptide from clear parafollicular cells in the thyroid gland. Imaging Calcitonin acts to reduce the serum calcium level and is secreted in response to raised serum calcium. It is bone mineral homeostasis include oestrogen, dual X-ray absorptiometry, which is performed on which prevents bone loss by inhibiting bone the spine and the hip. Risk factors include: genetics (ethnicity, family history, low body mass index) medical (rheumatoid arthritis, Cushing’s syndrome, chronic diseases) drugs (corticosteroids, anticonvulsants, chemotherapy, alcohol, smoking). The pathogenesis is an uncoupling of bone formation by osteoblasts and bone absorption by osteoclasts. Hip and distal radius fractures and vertebral compression fractures are the most common. They usually result in brain Spinal injuries are becoming increasingly common, stem and proximal spinal cord injury with loss of particularly in developed countries, because of the the breathing centres and death. They account for The majority of spinal injuries occur in the 10 per cent of all cervical spine injuries (Fig 10. The first two cervical vertebrae have a unique They have been classified by Anderson and anatomy. It is a ring structure with anterior and posterior Type I is an avulsion fracture of the tip of the arches and bulky lateral masses to support the peg and can be treated conservatively with weight of the head but has no vertebral body (this a collar. Its most distinctive feature is the tooth-like are often managed with a collar when painless process (the odontoid process) projecting from the non-union is acceptable. The odontoid process either a halo or surgical fixation is often (also known as the dens or peg) has two articulating indicated. These can be treated in a halo as they have The four injuries/fractures that can occur in the a very high rate of union because there is a C1/C2 region are: large bony surface area for healing. The typical mechanism is judicial 230 The spine hanging but also road traffic accidents where the chin hits the dashboard. This results in a traumatic spondylolisthesis of C2 on C3 with an avulsion injury of the anterior inferior corner of C2. These injuries are rarely associated with neurological injury as the canal is of a wide diameter at this level. Because the segments between T12 and L2 are between the rigid thoracic spine and more mobile lumbar spine, they are biome- chanically at greater risk of injury. It is important to remember the relationship between the spinal cord, conus and cauda equina and hence the type and degree of neurological injury that may be asso- ciated with fractures at each region. Remember that 20–25 per cent of patients with a spinal frac- ture at one level have a further spinal injury, half of which will be non-contiguous. The classification of thoracolumbar spinal frac- tures remains a matter of debate. Note the 50% translation of C5 on C6 and disc middle column: posterior half of vertebral body and disc and posterior longitudinal ligament posterior column: pedicles and laminae. It is valuable The fractures are classified as compression, to ascertain whether or not there is a disc pro- burst, seatbelt and fracture dislocations. Reduction may result in a large disc injury ent axis of injury and varying degrees of stability being prolapsed further towards the spinal cord, (Table 10. The investigation of spinal injuries invariably begins in the Emergency Department with a Management trauma series of plain radiographs (C-spine, chest and pelvis). Spinal imaging should be performed The treatment of choice is closed reduction using when indicated. Surgery may involve anterior column recon- These segments are stable and there is less struction, posterior pedicle screw instrumentation potential for post-traumatic kyphotic instability with distractive decompression by ligamentotaxis because the vertebral bodies at this level are below and 360-degree fusion techniques. The choice of the pelvic rim and have the strong iliolumbar liga- surgery will depend upon the exact injury anatomy ments attached to them. Burnand Many of the problems caused by diseases of the Some of the causes of discoloration are listed in arteries, veins and lymphatics are common to all of Table 11. The problems include: pain Dysfunction discoloration The pain, swelling and deformities caused by the dysfunction vascular diseases listed in Table 11. Pulsatile swellings Expansile pulsating swellings – dilated arteries – Pain may develop in any part of the arterial tree but most often occur in the abdominal aorta, iliac, femoral The causes of leg pain can usually be detected by and popliteal arteries. Investigations degenerative arterial disease but some are related to provide only confirmatory information and guid- ance for further management. Chronic ischaemia of the leg causing: Some of the causes of pain in the lower limb are Intermittent claudication listed in Table 11. Rest pain Ulceration Discoloration Gangrene The skin colour may vary between white, blue and Venous Deep vein thrombosis, acute and red according to the level of skin blood flow.
A 30 cm has been set by China where 90 percent nightsoil is used layer of earth is adequate between two layers of refuse cheap 100 mcg synthroid free shipping treatment 001. In India purchase 200mcg synthroid mastercard medicine man, this is practised in reclaiming such land for buildings cheap 75mcg synthroid free shipping symptoms 97 jeep 40 oxygen sensor failure, playgrounds purchase 125 mcg synthroid overnight delivery 7 medications that can cause incontinence, gardens West Bengal, where there are more than 130 sewage fed and agricultural farms. Sullage Physical, chemical and bacteriological changes occurring within the buried mass of refuse render it Water contained in sullage (as well as sewage) is a innocuous within 4-6 months after the decomposition precious commodity which must be retrieved, saved and of organic matter is complete. It is being increasingly realized now that fresh decomposition process the temperature rises to 60°C water supply in the world is limited and all water must within a week, killing various pathogens. Organic There are four stages in dealing with wastes: gases are liberated during the process of decomposition. In urban areas the sanitation Burning of refuse, though common, is not a desirable measures adopted are community based, such as practice. Hospital waste, because of being infected, needs to be The disposal of wastes will be described in this burnt in an incinerator. The process involves: chapter under four headings-Refuse disposal, Excreta • Drying disposal, Sewerage disposal and Sullage disposal. There is little air pollution if temperature is high, Proper disposal of refuse is essential for maintainance around 830°C. An earlier survey had estimated per capita daily solid waste output to be The dictionary meaning of compost is “A mixture of 0. The various decaying organic substances, as dead leaves, daily municipal collection in Delhi is 8000 metric tonnes, manure, etc. The resulting product, called compost, Dumping solid waste on vacant land is not a desirable is a good organic manure for agricultural purposes. Food may be contaminated with pit becomes full it is covered with earth and left for feces through fingers, flies, water or soil. If the refuse is too dry, water or sullage water excreta disposal is to provide a sanitation barrier is added to expedite fermentation. Properly done, compo- Two types of methods are in vogue for disposal of sting is quite hygienic and paying. The nonsewage methods include the conservancy method Com posting with Nightsoil and sanitary latrines. The former involves manual handling of human excreta, which is collected and In Indian context, composting of town wastes invariably 4a carried for disposal at some other site. Because of not involve human handling of excreta, which is the health hazards involved in handling human excreta, disposed of on the spot. It is suitable for water carriage of excreta through a system of drains and communities with population between 5000-100,000. The It has to be carried out with proper precautions so that sewage system, though very hygienic, is very costly. In practice, Studies undertaken by the World Bank during the fly production is difficult to control. International Water Supply and Sanitation Decade There are two methods of composting-aerobic and (1981-1990) led it to conclude that, “In industrialized anaerobic. The aerobic method in India was countries, users and responsible officials have come to standardized by Sir Albert Howard in early 30’s at view the flush toilet as the absolutely essential part of Indore. The method recommended in India is the Bangalore This technology, however, was designed for maximal method based upon anaerobic composting. The method was developed at the Indian Institute of problem facing developing countries is a familiar one; Science, Bengaluru, in collaboration with the Indian 5 high expectations coupled with limited resources. Layers of refuse and is no foreseeable way that waterborne waste disposal, nightsoil are alternated (15-25 cm of refuse and 5 cm with an average investment cost of around $300 per nightsoil) till they rise 30 cm above the ground level. The temperature in the pit rises sewerage is a decision to provide a water connection above 60°C, destroying all pathogens. Clearly, lower cost solutions have to completely turned on 4-7th day, so that the material be found for the majority of people. This is repeated 5-10 days after have to press for sewerage because, without it, public the first turning. Sewage Some countries like Israel, Switzerland, Germany treatment works commonly discharge effluents in a and Holland use mechanical composting, which uses the condition little better (and in some cases worse) than aerobic technique. There is, therefore, little realistic Here all reusable material is first salvaged from the basis for the commonly held view that Western refuse. The remnant is then pulverized (particle size less sanitation techniques are the appropriate solution for than 5 cm) and mixed with sewage or nightsoil. Rather, reeducation of engineers mixture is indubated, controlling factors like to design for maximal health benefits, and to consider temperature, aeration, pH, moisture and carbon- the whole range of available technologies, is essential. It has been recommended that mechanical Conservancy Method compositing should be introduced in cities in India where the population is more than 5 lakhs. This method involves manual collection and removal of human Excreta Disposal excreta to the disposal point. The nightsoil from latrines Fecally transmitted diseases constitute an important is collected daily by sweepers in buckets and is carried segment of preventable morbidity and mortality. The nightsoil is disposed as follows: • Trenching: Nightsoil is filled in trenches and covered with with loose earth. The variation pit is closed by filling loose earth when its contents reach are based on economy, simplicity, nature of soil and within 50 cm of ground level. The qualities of a suitable latrine are: converted to harmless manure through the process of • It should be acceptable to people anaerobic digestion. It is not in much use today, having • It should be simple in construction and use been superseded by better methods. A global field survey-cum-research project In order to avoid the risk of water pollution, the bore undertaken by the World Bank in 39 communities hole and dug well latrines should be situated at least around the world identified the following five types of 10 meters away from a source of drinking water. The pit latrines consist of a pit dug into the ground into which the feces drop down and are anaerobically digested. The handflush seal latrine is basically a pit latrine with the provision of a water seal. The septic tank is a water tight masonary tank in which anaerobic digestion occurs within the tank and aerobic oxidation of the effluent is achieved though subsoil irrigation. Septic tanks are designed to deal with a large amount of water, which may be sullage water as well as water flushed from cisterns in the usual modern water seal latrines. The aqua privy is a small septic tank for family use where there is no water seal near the squatting plate. The inlet pipe through which the faecal matter drops down opens below water level near the bottom of the tank, thus providing the function of water seal. Odor elimination: In a traditional pit latrine, odors enter from the pit into the superstructure. This occurs via an air circulatory current whereby air from the superstructure enters the pit, goes upto the vent pipe and escapes into the atmosphere. Prevention of fly entry: Flies enter a traditional pit latrine and breed there because they are attracted Fig.
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