A pulmonary alveolus is a hollow cavity found in the lung parenchyma, is the basic unit of ventilation. Lung alveoli are the ends of the respiratory tree, branching from either alveolar sacs or alveolar ducts, which like alveoli are both sites of gas exchange with the blood as well. Alveoli are particular to mammalian lungs. Different structures are involved in gas exchange in other vertebrates; the alveolar membrane is the gas exchange surface. Carbon dioxide rich blood is pumped from the rest of the body into the capillaries that surround the alveoli where, through diffusion, carbon dioxide is released and oxygen is absorbed; the alveoli are located in the respiratory zone of the lungs, at the ends of the alveolar ducts and alveolar sac, representing the smallest units in the respiratory tract. They provide total surface area of about 75m2. A typical pair of human lungs contain about 480 million alveoli; each alveolus is wrapped in a fine mesh of capillaries covering about 70% of its area. An adult alveolus has an average diameter of 200 µm, with an increase in diameter during inhalation.
The alveoli consist of an epithelial layer and an extracellular matrix surrounded by small blood vessels called capillaries. In some alveolar walls there are pores between alveoli called Pores of Kohn; the alveoli contain elastic fibers. The elastic fibres allow the alveoli to stretch, they spring back during exhalation in order to expel the carbon dioxide-rich air. There are three major types of cell in the alveolar wall: two types of alveolar cell and a large phagocyte known as an alveolar macrophage. Type I cells form the structure of the alveoli. Type I alveolar cells are squamous and cover 90–95% of the alveolar surface. Type I cells are involved in the process of gas exchange between blood; these cells are thin – the electron microscope was needed to prove that all alveoli are covered with an epithelial lining. These cells need to be so thin to be permeable for enabling an easy gas exchange between the alveoli and the blood. Organelles of type I alveolar cells such as the endoplasmic reticulum, Golgi apparatus and mitochondria are clustered around the nucleus.
The nuclei occupy large areas of free cytoplasm. This reduces the thickness of the cell; the cytoplasm in the thin portion contains pinocytotic vesicles which may play a role in the removal of small particulate contaminants from the outer surface. In addition to desmosomes, all type I alveolar cells have occluding junctions that prevent the leakage of tissue fluid into the alveolar air space. Type I pneumocytes are susceptible to toxic insults. In the event of damage, type II cells can proliferate and differentiate into type I cells to compensate. Type II cells secrete pulmonary surfactant to lower the surface tension of water and allows the membrane to separate, therefore increasing its capability to exchange gases; the surfactant is continuously released by exocytosis. It forms an underlying aqueous protein-containing hypophase and an overlying phospholipid film composed of dipalmitoyl phosphatidylcholine. Type II alveolar cells cover a small fraction of the alveolar surface area. Type II cells are capable of cellular division, giving rise to more type I and II alveolar cells when the lung tissue is damaged.
These cells are granular and cuboidal. Type II alveolar cells are found at the blood-air barrier. Although they only make up <5% of the alveolar surface, they are numerous. The alveolar macrophages called dust cells, destroy foreign materials and microbes such as bacteria. Type I cells are flat cells lining the alveolar walls; each alveolus is surrounded by numerous capillaries, is the site of gas exchange, which occurs by diffusion. The low solubility of oxygen necessitates the large internal surface area and thin walls of the alveoli. Weaving between the capillaries and helping to support them is an extracellular matrix, a meshlike fabric of elastic and collagenous fibres; the collagen fibres, being more rigid, give the wall firmness, while the elastic fibres permit expansion and contraction of the walls during breathing. Type II cells in the alveolar wall contain secretory granular organelles known as lamellar bodies that fuse with the cell membranes and secrete pulmonary surfactant; this surfactant is a film of fatty substances, a group of phospholipids that reduce alveolar surface tension.
The phospholipid are stored in the lamellar bodies. Without this coating, the alveoli would collapse and large forces would be required to re-expand them. Type II cells start to develop at about 26 weeks of gestation, secreting small amounts of surfactant. However, adequate amounts of surfactant are not secreted until about 35 weeks of gestation - this is the main reason for increased rates of infant respiratory distress syndrome, which drastically reduces at ages above 35 weeks gestation. Type II pneumocytes will replicate to replace damaged type I cells. MUC1, a human gene associated with type II pneumocytes, has been identified as a marker in lung cancer. Another type of cell, known as an alveolar macrophage, resides on the internal surfaces of the air cavities of the alveoli, the alveolar ducts, the bronchioles, they are mobile scavengers that serve to engulf
In humans, the respiratory tract is the part of the anatomy of the respiratory system involved with the process of respiration. Air is breathed in through the mouth. In the nasal cavity, a layer of mucous membrane acts as a filter and traps pollutants and other harmful substances found in the air. Next, air moves into the pharynx, a passage that contains the intersection between the esophagus and the larynx; the opening of the larynx has a special flap of cartilage, the epiglottis, that opens to allow air to pass through but closes to prevent food from moving into the airway. From the larynx, air moves into the trachea and down to the intersection that branches to form the right and left primary bronchi; each of these bronchi branch into secondary bronchi that branch into tertiary bronchi that branch into smaller airways called bronchioles that connect with tiny specialized structures called alveoli that function in gas exchange. The lungs which are located in the thoracic cavity, are protected from physical damage by the rib cage.
At the base of the lungs is a sheet of skeletal muscle called the diaphragm. The diaphragm separates the lungs from intestines; the diaphragm is the main muscle of respiration involved in breathing, is controlled by the sympathetic nervous system. The lungs are encased in a serous membrane that folds in on itself to form the pleurae – a two-layered protective barrier; the inner visceral pleura covers the surface of the lungs, the outer parietal pleura is attached to the inner surface of the thoracic cavity. The pleurae enclose; this fluid is used to decrease the amount of friction. The respiratory tract is divided into lower airways; the upper airways or upper respiratory tract includes the nose and nasal passages, paranasal sinuses, the pharynx, the portion of the larynx above the vocal folds. The lower airways or lower respiratory tract includes the portion of the larynx below the vocal folds, trachea and bronchioles; the lungs can be included in the lower respiratory tract or as separate entity and include the respiratory bronchioles, alveolar ducts, alveolar sacs, alveoli.
The respiratory tract can be divided into a conducting zone and a respiratory zone, based on the distinction of transporting gases or exchanging them. The conducting zone includes structures outside of the lungs – the nose, pharynx and trachea, structures inside the lungs – the bronchi and terminal bronchioles; the conduction zone conducts air breathed in, filtered and moistened, into the lungs. It represents the 1st through the 16th division of the respiratory tract; the conducting zone is most of the respiratory tract that conducts gases into and out of the lungs, but excludes the respiratory zone that exchanges gases. The conducting zone functions to offer a low resistance pathway for airflow, it provides a major defense role in its filtering abilities. The respiratory zone includes the respiratory bronchioles, alveolar ducts and alveoli, is the site of oxygen and carbon dioxide exchange with the blood; the respiratory bronchioles and the alveolar ducts are responsible for 10% of the gas exchange.
The alveoli are responsible for the other 90%. The respiratory zone represents the 16th through the 23rd division of the respiratory tract. From the bronchi, the dividing tubes become progressively smaller with an estimated 20 to 23 divisions before ending at an alveolus; the upper respiratory tract, can refer to the parts of the respiratory system lying above the sternal angle, above the vocal folds, or above the cricoid cartilage. The larynx is sometimes included in both lower airways; the larynx is called the voice box and has the associated cartilage that produces sound. The tract consists of the nasal cavity and paranasal sinuses, the pharynx and sometimes includes the larynx; the lower respiratory tract or lower airway is derived from the developing foregut and consists of the trachea, bronchi and lungs. It sometimes includes the larynx; the lower respiratory tract is called the respiratory tree or tracheobronchial tree, to describe the branching structure of airways supplying air to the lungs, includes the trachea and bronchioles.
Trachea main bronchus lobar bronchus segmental bronchus subsegmental bronchus conducting bronchiole terminal bronchiole respiratory bronchiole alveolar duct alveolar sac alveolusAt each division point or generation, one airway branches into two or more smaller airways. The human respiratory tree may consist on average of 23 generations, while the respiratory tree of the mouse has up to 13 generations. Proximal divisions function to transmit air to the lower airways. Divisions including the respiratory bronchiole, alveolar ducts and alveoli, are specialized for gas exchange; the trachea is the largest tube in the respiratory tract and consists of tracheal rings of hyaline cartilage. It branches off into a left and a right main bronchus; the bronchi branch off into smaller sections inside the lungs, called bronchioles. These bronchioles give rise to the air sacs in the lungs called the alveoli; the lungs are the largest organs in the lower respiratory tract. The lungs are suspended within the pleural cavity of the thorax.
The pleurae are two thin membranes, one
Hematoxylin and eosin stain or haematoxylin and eosin stain is one of the principal stains in histology. It is the most used stain in medical diagnosis and is the gold standard. A combination of hematoxylin and eosin, it produces blues and reds; the staining method involves application of hemalum, a complex formed from aluminium ions and hematein. Hemalum colors nuclei of cells blue, along with a few other objects, such as keratohyalin granules and calcified material, which turns blue when exposed to alkaline water; the nuclear staining is followed by counterstaining with an aqueous or alcoholic solution of eosin Y, which colors eosinophilic structures in various shades of red and orange. The staining of nuclei by hemalum is ordinarily due to binding of the dye-metal complex to DNA, but nuclear staining can be obtained after extraction of DNA from tissue sections; the mechanism is different from that of nuclear staining by basic dyes such as thionine or toluidine blue. Staining by basic dyes occurs only from solutions that are less acidic than hemalum, it is prevented by prior chemical or enzymatic extraction of nucleic acids.
There is evidence to indicate that co-ordinate bonds, similar to those that hold aluminium and hematein together, bind the hemalum complex to DNA and to carboxy groups of proteins in the nuclear chromatin. The eosinophilic structures are composed of intracellular or extracellular protein; the Lewy bodies and Mallory bodies are examples of eosinophilic structures. Most of the cytoplasm is eosinophilic. Red blood cells are stained intensely red; the structures do not have to be basic to be called basophilic and eosinophilic. Other colors, e.g. yellow and brown, can be present in the sample. Some structures do not stain well. Basal laminae need to be stained by PAS stain or some silver stains, if they have to be well visible. Reticular fibers require silver stain. Hydrophobic structures tend to remain clear. Hematoxylin is a dark blue or violet stain, basic/positive, it binds to basophilic substances. DNA/RNA in the nucleus, RNA in ribosomes in the rough endoplasmic reticulum are both acidic because the phosphate backbones of nucleic acids are negatively charged.
These backbones form salts with basic dyes containing positive charges. Therefore, dyes stain them violet. Eosin is a red or pink stain, acidic and negative, it binds to acidophilic substances such as positively charged amino-acid side chains. Most proteins in the cytoplasm of some cells are basic because they are positively charged due to the arginine and lysine amino-acid residues; these form salts with acid dyes containing negative charges, like eosin. Therefore, eosin stains them pink; this includes cytoplasmic filaments in muscle cells, intracellular membranes, extracellular fibers. So, in optical microscopy, one can observe: Nuclei in blue/purple Basophils in purplish red Cytoplasm in red Muscles in dark red Erythrocytes in cherry red Collagen in pale pink Mitochondria in pale pink Papanicolaou stain, another popular staining technique Cytopathology Acid-fast Baker JR Experiments on the action of mordants. 2. Aluminium-haematein. Quart. J. Microsc. Sci. 103: 493–517. Kiernan JA Histological and Histochemical Methods: Theory and Practice.
4th ed. Bloxham, UK: Scion. Lillie RD, Pizzolato P, Donaldson PT Nuclear stains with soluble metachrome mordant lake dyes; the effect of chemical endgroup blocking reactions and the artificial introduction of acid groups into tissues. Histochemistry 49: 23–35. Llewellyn BD Nuclear staining with alum-hematoxylin. Biotech. Histochem. 84: 159–177. Marshall PN, Horobin RW The mechanism of action of "mordant" des – a study using preformed metal complexes. Histochemie 35: 361–371. Puchtler H, Meloan SN, Waldrop FS Application of current chemical concepts to metal-haematein and -brazilein stains. Histochemistry 85: 353–364. SIGMA-ALDRICH H&E Informational Primer Routine Mayer's Hematoxylin and Eosin Stain Hematoxylin & Eosin Staining Protocol Rosen Lab, Department of Molecular and Cellular Biology, Baylor College of Medicine) Step by step protocol
A micrograph or photomicrograph is a photograph or digital image taken through a microscope or similar device to show a magnified image of an object. This is opposed to a macrograph or photomacrograph, an image, taken on a microscope but is only magnified less than 10 times. Micrography is the art of using microscopes to make photographs. A micrograph contains extensive details of microstructure. A wealth of information can be obtained from a simple micrograph like behavior of the material under different conditions, the phases found in the system, failure analysis, grain size estimation, elemental analysis and so on. Micrographs are used in all fields of microscopy. A light micrograph or photomicrograph is a micrograph prepared using an optical microscope, a process referred to as photomicroscopy. At a basic level, photomicroscopy may be performed by connecting a camera to a microscope, thereby enabling the user to take photographs at reasonably high magnification. Scientific use began in England in 1850 by Prof Richard Hill Norris FRSE for his studies of blood cells.
Roman Vishniac was a pioneer in the field of photomicroscopy, specializing in the photography of living creatures in full motion. He made major developments in light-interruption photography and color photomicroscopy. Photomicrographs may be obtained using a USB microscope attached directly to a home computer or laptop. An electron micrograph is a micrograph prepared using an electron microscope. Micrographs have micron bars, or magnification ratios, or both. Magnification is a ratio between the size of an object on its real size. Magnification can be a misleading parameter as it depends on the final size of a printed picture and therefore varies with picture size. A scale bar, or micron bar, is a line of known length displayed on a picture; the bar can be used for measurements on a picture. When the picture is resized the bar is resized making it possible to recalculate the magnification. Ideally, all pictures destined for publication/presentation should be supplied with a scale bar. All but one of the micrographs presented on this page do not have a micron bar.
The microscope has been used for scientific discovery. It has been linked to the arts since its invention in the 17th century. Early adopters of the microscope, such as Robert Hooke and Antonie van Leeuwenhoek, were excellent illustrators. After the invention of photography in the 1820s the microscope was combined with the camera to take pictures instead of relying on an artistic rendering. Since the early 1970s individuals have been using the microscope as an artistic instrument. Websites and traveling art exhibits such as the Nikon Small World and Olympus Bioscapes have featured a range of images for the sole purpose of artistic enjoyment; some collaborative groups, such as the Paper Project have incorporated microscopic imagery into tactile art pieces as well as 3D immersive rooms and dance performances. Close-up Digital microscope Macro photography Microphotograph Microscopy USB microscope Make a Micrograph – This presentation by the research department of Children's Hospital Boston shows how researchers create a three-color micrograph.
Shots with a Microscope – a basic, comprehensive guide to photomicrography Scientific photomicrographs – free scientific quality photomicrographs by Doc. RNDr. Josef Reischig, CSc. Micrographs of 18 natural fibres by the International Year of Natural Fibres 2009 Seeing Beyond the Human Eye Video produced by Off Book - Solomon C. Fuller bio Charles Krebs Microscopic Images Dennis Kunkel Microscopy Andrew Paul Leonard, APL Microscopic Cell Centered Database - Montage Nikon Small World Olympus Bioscapes Other examples
A capillary is a small blood vessel from 5 to 10 micrometres in diameter, having a wall one endothelial cell thick. They are the smallest blood vessels in the body: they convey blood between the arterioles and venules; these microvessels are the site of exchange of many substances with the interstitial fluid surrounding them. Substances which exit include water and glucose. Lymph capillaries connect with larger lymph vessels to drain lymphatic fluid collected in the microcirculation. During early embryonic development new capillaries are formed through vasculogenesis, the process of blood vessel formation that occurs through a de novo production of endothelial cells which form vascular tubes; the term angiogenesis denotes the formation of new capillaries from pre-existing blood vessels and present endothelium which divides. Blood flows from the heart through arteries, which branch and narrow into arterioles, branch further into capillaries where nutrients and wastes are exchanged; the capillaries join and widen to become venules, which in turn widen and converge to become veins, which return blood back to the heart through the venae cavae.
Individual capillaries are part of the capillary bed, an interweaving network of capillaries supplying tissues and organs. The more metabolically active a tissue is, the more capillaries are required to supply nutrients and carry away waste products. There are two types of capillaries: true capillaries, which branch from arterioles and provide exchange between tissue and the capillary blood, metarterioles, found only in the mesenteric circulation, they are short vessels that directly connect the arterioles and venules at opposite ends of the beds. Metarterioles are found in the mesenteric microcirculation; the physiological mechanisms underlying precapillary resistance is no longer considered to be a result of precapillary sphincters outside of the mesentery organ. Lymphatic capillaries are larger in diameter than blood capillaries, have closed ends; this structure permits interstitial fluid to flow into them but not out. Lymph capillaries have a greater internal oncotic pressure than blood capillaries, due to the greater concentration of plasma proteins in the lymph.
There are three types of blood capillaries: Continuous capillaries are continuous in the sense that the endothelial cells provide an uninterrupted lining, they only allow smaller molecules, such as water and ions to pass through their intercellular clefts. Lipid-soluble molecules can passively diffuse through the endothelial cell membranes along concentration gradients. Continuous capillaries can be further divided into two subtypes: Those with numerous transport vesicles, which are found in skeletal muscles, fingers and skin; those with few vesicles, which are found in the central nervous system. These capillaries are a constituent of the blood–brain barrier. Fenestrated capillaries have pores in the endothelial cells that are spanned by a diaphragm of radially oriented fibrils and allow small molecules and limited amounts of protein to diffuse. In the renal glomerulus there are cells with no diaphragms, called podocyte foot processes or pedicels, which have slit pores with a function analogous to the diaphragm of the capillaries.
Both of these types of blood vessels have continuous basal laminae and are located in the endocrine glands, intestines and the glomeruli of the kidney. Sinusoid capillaries are a special type of open-pore capillary, that have larger openings in the endothelium; these types of blood vessels allow red and white blood cells and various serum proteins to pass, aided by a discontinuous basal lamina. These capillaries lack pinocytotic vesicles, therefore utilize gaps present in cell junctions to permit transfer between endothelial cells, hence across the membrane. Sinusoid blood vessels are located in the bone marrow, lymph nodes, adrenal glands; some sinusoids are distinctive in. They are called discontinuous sinusoidal capillaries, are present in the liver and spleen, where greater movement of cells and materials is necessary. A capillary wall is simple squamous epithelium; the capillary wall performs an important function by allowing nutrients and waste substances to pass across it. Molecules larger than 3 nm such as albumin and other large proteins pass through transcellular transport carried inside vesicles, a process which requires them to go through the cells that form the wall.
Molecules smaller than 3 nm such as water and gases cross the capillary wall through the space between cells in a process known as paracellular transport. These transport mechanisms allow bidirectional exchange of substances depending on osmotic gradients and can be further quantified by the Starling equation. Capillaries that form part of the blood–brain barrier however only allow for transcellular transport as tight junctions between endothelial cells seal the paracellular space. Capillary beds may control their blood flow via autoregulation; this allows an organ to maintain constant flow despite a change in central blood pressure. This is achieved by myogenic response, in the kidney by tubuloglomerular feedback; when blood pressure increases, arterioles are stretched and subsequently constrict to counteract the
University of California
The University of California is a public university system in the U. S. state of California. Under the California Master Plan for Higher Education, the University of California is a part of the state's three-system public higher education plan, which includes the California State University system and the California Community Colleges System; the University of California was founded on March 23, 1868, operated temporarily in Oakland before moving to its new campus in Berkeley in 1873. In March 1951, the University of California began to reorganize itself into something distinct from its first campus at Berkeley, with Robert Gordon Sproul remaining in place as the first systemwide President and Clark Kerr becoming the first Chancellor of UC Berkeley. However, the 1951 reorganization was stalled by resistance from Sproul and his allies, it was not until Kerr succeeded Sproul as President that UC was able to evolve into a true university system from 1957 to 1960. In the 21st century, the University of California has 10 campuses, a combined student body of 251,700 students, 21,200 faculty members, 144,000 staff members and over 1.86 million living alumni, as governed by a semi-autonomous Board of Regents.
Its tenth and newest campus in Merced opened in fall 2005. Nine campuses enroll graduate students. In addition, the UC Hastings College of Law, located in San Francisco, is affiliated with UC, but other than sharing its name is autonomous from the rest of the system; the University of California manages or co-manages three national laboratories for the U. S. Department of Energy: Lawrence Berkeley National Laboratory, Lawrence Livermore National Laboratory, Los Alamos National Laboratory. Collectively, the colleges and alumni of the University of California make it the most comprehensive and advanced postsecondary educational system in the world, responsible for nearly $50 billion per year of economic impact. UC campuses have large numbers of distinguished faculty in every academic discipline, with UC faculty and researchers having won at least 62 Nobel Prizes as of 2017. In 1849, the state of California ratified its first constitution, which contained the express objective of creating a complete educational system including a state university.
Taking advantage of the Morrill Land-Grant Acts, the California Legislature established an Agricultural and Mechanical Arts College in 1866. However, it existed only as a placeholder to secure federal land-grant funds. Meanwhile, Congregational minister Henry Durant, an alumnus of Yale, had established the private Contra Costa Academy, on June 20, 1853, in Oakland, California; the initial site was bounded by Twelfth and Fourteenth Streets and Harrison and Franklin Streets in downtown Oakland. In turn, the Academy's trustees were granted a charter in 1855 for a College of California, though the College continued to operate as a college preparatory school until it added college-level courses in 1860; the College's trustees and supporters believed in the importance of a liberal arts education, but ran into a lack of interest in liberal arts colleges on the American frontier. In November 1857, the College's trustees began to acquire various parcels of land facing the Golden Gate in what is now Berkeley for a future planned campus outside of Oakland.
But first, they needed to secure the College's water rights by buying a large farm to the east. In 1864, they organized the College Homestead Association, which borrowed $35,000 to purchase the land, plus another $33,000 to purchase 160 acres of land to the south of the future campus; the Association subdivided the latter parcel and started selling lots with the hope it could raise enough money to repay its lenders and create a new college town. But sales of new homesteads fell short. Governor Frederick Low favored the establishment of a state university based upon the University of Michigan plan, thus in one sense may be regarded as the founder of the University of California. At the College of California's 1867 commencement exercises, where Low was present, Benjamin Silliman, Jr. criticized Californians for creating a state polytechnic school instead of a real university. That same day, Low first suggested a merger of the already-functional College of California with the nonfunctional state college, went on to participate in the ensuing negotiations.
On October 9, 1867, the College's trustees reluctantly agreed to join forces with the state college to their mutual advantage, but under one condition—that there not be an "Agricultural and Mechanical Arts College", but a complete university, within which the assets of the College of California would be used to create a College of Letters. Accordingly, the Organic Act, establishing the University of California, was introduced as a bill by Assemblyman John W. Dwinelle on March 5, 1868, after it was duly passed by both houses of the state legislature, it was signed into state law by Governor Henry H. Haight on March 23, 1868. However, as constituted, the new University was not an actual merger of the two colleges, but was an new institution which inherited certain objectives and assets from each of them; the University
Cocaine known as coke, is a strong stimulant used as a recreational drug. It is snorted, inhaled as smoke, or dissolved and injected into a vein. Mental effects may include loss of contact with reality, an intense feeling of happiness, or agitation. Physical symptoms may include a fast heart rate and large pupils. High doses can result in high blood pressure or body temperature. Effects begin within seconds to last between five and ninety minutes. Cocaine has a small number of accepted medical uses such as numbing and decreasing bleeding during nasal surgery. Cocaine is addictive due to its effect on the reward pathway in the brain. After a short period of use, there is a high risk, its use increases the risk of stroke, myocardial infarction, lung problems in those who smoke it, blood infections, sudden cardiac death. Cocaine sold on the street is mixed with local anesthetics, quinine, or sugar, which can result in additional toxicity. Following repeated doses a person may have decreased ability to feel pleasure and be physically tired.
Cocaine acts by inhibiting the reuptake of serotonin and dopamine. This results in greater concentrations of these three neurotransmitters in the brain, it can cross the blood–brain barrier and may lead to the breakdown of the barrier. Cocaine is a occurring substance found in the coca plant, grown in South America. In 2013, 419 kilograms were produced legally, it is estimated. With further processing crack cocaine can be produced from cocaine. Cocaine is the second most used illegal drug globally, after cannabis. Between 14 and 21 million people use the drug each year. Use is highest in North America followed by South America. Between one and three percent of people in the developed world have used cocaine at some point in their life. In 2013, cocaine use directly resulted in 4,300 deaths, up from 2,400 in 1990; the leaves of the coca plant have been used by Peruvians since ancient times. Cocaine was first isolated from the leaves in 1860. Since 1961, the international Single Convention on Narcotic Drugs has required countries to make recreational use of cocaine a crime.
Topical cocaine can be used as a local numbing agent to help with painful procedures in the mouth or nose. Cocaine is now predominantly used for lacrimal duct surgery; the major disadvantages of this use are cocaine's potential for cardiovascular toxicity and pupil dilation. Medicinal use of cocaine has decreased as other synthetic local anesthetics such as benzocaine, proparacaine and tetracaine are now used more often. If vasoconstriction is desired for a procedure, the anesthetic is combined with a vasoconstrictor such as phenylephrine or epinephrine; some ENT specialists use cocaine within the practice when performing procedures such as nasal cauterization. In this scenario dissolved cocaine is soaked into a ball of cotton wool, placed in the nostril for the 10–15 minutes before the procedure, thus performing the dual role of both numbing the area to be cauterized, vasoconstriction; when used this way, some of the used cocaine may be absorbed through oral or nasal mucosa and give systemic effects.
An alternative method of administration for ENT surgery is mixed with adrenaline and sodium bicarbonate, as Moffett's solution. Cocaine is a powerful nervous system stimulant, its effects can last from 30 minutes to an hour. The duration of cocaine's effects depends on the route of administration. Cocaine can be in the form of fine white powder, bitter to the taste; when inhaled or injected, it causes a numbing effect. Crack cocaine is a smokeable form of cocaine made into small "rocks" by processing cocaine with sodium bicarbonate and water. Crack cocaine is referred to. Cocaine use leads to increases in alertness, feelings of well-being and euphoria, increased energy and motor activity, increased feelings of competence and sexuality. Coca leaves are mixed with an alkaline substance and chewed into a wad, retained in the mouth between gum and cheek and sucked of its juices; the juices are absorbed by the mucous membrane of the inner cheek and by the gastrointestinal tract when swallowed. Alternatively, coca leaves can be consumed like tea.
Ingesting coca leaves is an inefficient means of administering cocaine. Because cocaine is hydrolyzed and rendered inactive in the acidic stomach, it is not absorbed when ingested alone. Only when mixed with a alkaline substance can it be absorbed into the bloodstream through the stomach; the efficiency of absorption of orally administered cocaine is limited by two additional factors. First, the drug is catabolized by the liver. Second, capillaries in the mouth and esophagus constrict after contact with the drug, reducing the surface area over which the drug can be absorbed. Cocaine metabolites can be detected in the urine of subjects that have sipped one cup of coca leaf infusion. Orally administered cocaine takes 30 minutes to enter the bloodstream. Only a third of an oral dose is absorbed, although absorption has been shown to reach 60% in controlled settings. Given the slow rate of absorption, maximum physiological and psychotropic effects are attained 60 minutes after cocaine is administered by ingestion.
While the onset of these effects is slow, the effects are sustained for approxima