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Almost 6 months didn’t write and the blog seems cobwebbed. In this early new year I were given a task to teach form 5 students of two biological classes. This year is also assigned as s/u PBS and it was still unclear how the implementation is and just waiting and waiting for instructions from the superior. To students, I’ll give the best for you and make us proud in SPM later. God willing..
The purpose of the nose is to warm, clean, and humidify the air you breathe as well as help you to smell and taste. A normal person will produce about two quarts of fluid each day (mucus), which aids in keeping the respiratory tract clean and moist. Tiny microscopic hairs (cilia) line the surfaces of the nasal cavity, helping to brush away particles. Eventually the mucus blanket is moved to the back of the throat where it is unconsciously swallowed. This entire process is closely regulated by several body systems.
Structurally, the nose is separated into two passageways (left and right nostrils) by a structure called the septum. Protruding into each breathing passage are bony projections, called turbinates, which help to increase the surface area of the inside of the nose. There are three turbinates on each side of the nose (inferior or lower turbinates, middle turbinates, superior or upper turbinates). The sinuses are four paired, air-filled chambers which empty into the nasal cavity. Their purpose is not really known, but may help to lighten the skull, reducing its weight.
Rhinitis is a very common condition and has many different causes. Basically, rhinitis may be defined as inflammation of the inner lining of the nose. More specifically speaking, it may be defined by the presence of one or more of the following symptoms:
Post-nasal drip is mucus accumulation in the back of the nose and throat leading to, or giving the sensation of, mucus dripping downward from the back of the nose. One of the most common characteristics of chronic rhinitis is post-nasal drip. Post-nasal drip may lead to chronic sore throat or chronic cough. Post-nasal drip can be caused by excessive or thick secretions, or impairment in the normal clearance of mucus from the nose and throat.
Rhinitis has many possible causes. Rhinitis can be either acute or chronic.
Allergic rhinitis is a very common cause of rhinitis. It is caused by allergies and is characterized by an itchy/runny nose, sneezing, and nasal congestion. Other allergic symptoms include:
People with allergic rhinitis also have a higher incidence of asthma and eczema, which are also mainly allergic in origin.
Seasonal allergic rhinitis (hay fever) is usually caused by pollen in the air, and sensitive patients have symptoms during peak times during the year.
Perennial allergic rhinitis, a type of chronic rhinitis is a year-round problem, and is often caused by indoor allergens (particles that cause allergies), such as dust and animal dander in addition to pollens that may exist at the time. Symptoms tend to occur regardless of the time of the year.
No, rhinitis may have many causes other than allergies. Some of these other types of rhinitis are listed below.
Non-allergic rhinitis occurs in those patients in whom an allergic or other causes of rhinitis cannot be identified. Non-allergic rhinitis may be further divided into three types;
These conditions may not have the other allergic manifestations such as, itchy and runny eyes and are also more persistent and less seasonal.
Occupational rhinitis may arise from exposure to irritants at a person's workplace with improvement of symptoms after the person leaves the workplace.
Other causes of rhinitis may be related to:
Infections, mostly viral, are a common cause of rhinitis. Viral rhinitis is usually not chronic and may resolve by itself.
Sometimes rhinitis may be related to other generalized medical conditions such as:
The treatment is generally directed towards the underlying cause.
Identifying and avoiding allergens
An allergy is an exaggerated "normal body" inflammatory response to an outside substance. These substances that cause allergies are called allergens, and typically include:
The best treatment is avoidance of these allergens, but in many cases this may be very difficult if not impossible. Some helpful suggestions include:
Avoidance of nasal irritants: Nasal irritants usually do not lead to the typical immune response seen with classical allergies, but nevertheless they can mimic or make allergies worse, as in vasomotor rhinitis. Examples of these irritants include cigarette smoke, perfume, aerosol sprays, smoke, smog and car exhaust.
Identifying the possible allergens may be just as hard as avoiding them. In some, this may be identified by a very careful history taken by their physician. Details of the patient's possible exposure to allergens or irritant at home or the workplace may give some clues. In others, even a very detailed history may not reveal a possible trigger. Therefore, a consultation with an allergy specialist (allergy and immunologist) may be prudent. The allergy doctor may perform some simple skin tests to try to identify common environmental allergies.
In addition to measures noted above, medications may also be used for the treatment of rhinitis and post-nasal drip.
For allergic rhinitis and post-nasal drip many medications are used.
Steroid nasal sprays
The experts recommend using intra-nasal glucocorticoids (steroid sprays applied directly into the nose) as the first line of treatment. Steroids are known to be potent anti-inflammatory and anti-allergic agents and they are known to relieve most of the associated symptoms of runny and itchy nose, nasal congestion, sneezing, and post-nasal drip.
Their use must be monitored and tapered by the prescribing physician as long-term use may have significant side effects. Examples of the nasal steroids include:
These are generally used once or twice daily. It is recommended to tilt the head forward during the administration to avoid from spraying the back of the throat instead of the nose.
Oral steroids
These drugs [prednisone, methylprednisolone (Medrol), hydrocortisone (Hydrocortone, Cortef)] are highly effective in allergic patients; however there is a potential for serious side effects when used for extended periods. They are best used for the short-term management of allergic problems, and a physician must always monitor their use. These are reserved only for very severe cases that do not respond to the usual treatment with nasal steroids and antihistamines.
Antihistamines
Allergy medications, such as antihistamines, are also frequently used to allergic rhinitis and post-nasal drip. These are generally used as the second line of treatment after the nasal steroids or in combination with them. Histamines are naturally occurring chemicals released in response to an exposure to an allergen, which are responsible for the congestion, sneezing, and runny nose typical of an allergic reaction. Antihistamines are drugs that block the histamine reaction. These medications work best when given prior to exposure.
Antihistamines can be divided into two groups:
There is also a nasal antihistamine preparation that has been shown to be very effective in treating allergic rhinitis, called azelastine nasal (Astelin).
Decongestant sprays
Examples of decongestant sprays include:
Decongestant sprays quickly reduce swelling of nasal tissues by shrinking the blood vessels. They improve breathing and drainage over the short-term. Unfortunately, if they are used for more than a few days they can become highly addictive (rhinitis medicamentosa). Long-term use can lead to serious damage. Therefore, their use should limited to only 3 to 7 days.
Oral decongestants
Oral decongestants temporarily reduce swelling of sinus and nasal tissues leading to an improvement of breathing and a decrease in obstruction. They may also stimulate the heart and raise the blood pressure and should be avoided by patients who have high blood pressure, heart irregularities, glaucoma, thyroid problems, or difficulty in urination. The most common decongestant is pseudoephedrine (Sudafed).
Cromolyn sodium (Nasalcrom)
Cromolyn sodium (Nasalcrom) is a spray helps to stabilize allergy cells (mast cells) by preventing release of allergy mediators, like histamine. They are most effective if used before the start of allergy season or prior to exposure to a known allergen.
Montelukast (Singulair)
Montelukast (Singulair) is an agent that acts similar to antihistamine, although it is involved in another pathway in allergic response. It has been shown to be less beneficial than the steroid nasal sprays, but equally as effective as some of the antihistamines. It may be useful in patients who do not wish to use nasal sprays or those who have co-existing asthma.
Ipratropium (Atrovent nasal)
Ipratropium (Atrovent nasal) is used as a nasal spray and helps to control nasal drainage mediated by neural pathways. It will not treat an allergy, but it does decrease nasal drainage.
Mucus thinning agents
Mucus thinning agents are utilized to make secretions thinner and less sticky. They help to prevent pooling of secretions in the back of the nose and throat where they often cause choking. The thinner secretions pass more easily. Guaifenesin (Humibid, Fenesin, Organidin) is a commonly used formulation. If a rash develops or there is swelling of the salivary glands, they should be discontinued. Inadequate fluid intake will also thicken secretions. Increasing the amount of water consumed, and eliminating caffeine from the diet and the use of diuretics are also helpful.
Allergy shots (Immunotherapy)
Allergy shots interfere with the allergic response. After identification of an allergen, small amounts are given back to the sensitive patient. Over time the patient will develop blocking antibodies to the allergen, and they become less sensitive and less reactive to the substance causing allergic symptoms.
Combinations
These drugs are made up of one or more anti-allergy medications. They are usually a combination of an antihistamine and a decongestant. Other common combinations include mucus thinning agents, anti-cough agents, aspirin, ibuprofen (Advil), or acetaminophen (Tylenol). They help to simplify dosing and often will work either together for even more benefit or have counteracting side effects that eliminate or reduce total side effects.
Acute rhinitis: Inflammation of the nose that occurs for only a few days. Typically this is caused by a virus ("a cold"); if it goes on beyond a week then it is probably a bacterial infection.
Allergens: Normally harmless substances which cause an exaggerated allergic reaction (inflammatory response) in sensitive people.
Allergic rhinitis: Medical term for hay fever, a condition due to allergy that mimics a chronic cold. (Hay fever is a misnomer since hay is not a usual cause of this problem and there is no fever). Many substances cause the allergic symptoms in hay fever. Allergic rhinitis is the correct term for this allergic reaction. (Rhinitis means "irritation of the nose" and is a derivative of Rhino, meaning "nose.") Symptoms include nasal congestion, a clear runny nose, sneezing, nose and eye itching, eye redness, and tearing of the eyes. Post-nasal dripping of clear mucus frequently causes a cough. Loss of smell is common, and loss of taste occurs occasionally. Nose bleeding may occur if the condition is severe.
Chronic rhinitis: inflammation of the nose that goes on for weeks to months which is different from "a cold", and may be caused by allergy, nasal irritants, or structural or physiological problems.
Hay fever: A seasonal allergy to airborne particles characterized by runny/itchy nose and eyes, sneezing, itchy throat, excess mucus, and nasal congestion. It is a misnomer because it is not caused by hay and it does not produce a fever.
Non-allergic rhinitis: Inflammatory condition of the nose without an obvious allergy as the cause.
Post nasal drip: Mucous accumulation in the back of the nose and throat leading to or giving the sensation of mucus dripping downward from the back of the nose.
Summer cold: Similar to hay fever. Summer cold is also a misnomer because it is not caused by a virus.
Vasomotor rhinitis: Similar to non-allergic rhinitis, thought to be mediated by an abnormal neuronal control of the blood vessels supplying the nose.
The basic mechanism by which enzymes catalyze chemical reactions begins with the binding of the substrate (or substrates) to the active site on the enzyme. The active site is the specific region of the enzyme which combines with the substrate. The binding of the substrate to the enzyme causes changes in the distribution of electrons in the chemical bonds of the substrate and ultimately causes the reactions that lead to the formation of products. The products are released from the enzyme surface to regenerate the enzyme for another reaction cycle.
The active site has a unique geometric shape that is complementary to the geometric shape of a substrate molecule, similar to the fit of puzzle pieces. This means that enzymes specifically react with only one or a very few similar compounds.
Lock and Key Theory:
The specific action of an enzyme with a single substrate can be explained using a Lock and Key analogy first postulated in 1894 by Emil Fischer. In this analogy, the lock is the enzyme and the key is the substrate. Only the correctly sized key (substrate) fits into the key hole (active site) of the lock (enzyme).
Smaller keys, larger keys, or incorrectly positioned teeth on keys (incorrectly shaped or sized substrate molecules) do not fit into the lock (enzyme). Only the correctly shaped key opens a particular lock. Watch the video below for better understanding on mechanism of enzyme action.
Meiosis begins with Interphase I. During this phase there is a duplication genetic material, DNA replication. Cells go from being 2N, 2C (N= chromosome content, C = DNA content) to 2N, 4C. Cells remain in this active phase 75% of the time. The chromatin remains in a nuclear envelope while a pair of centrioles lies inside a centrosome.
During Prophase I, the chromatin condenses into chromosomes, the nuclear envelope disappears, and a spindle apparatus begins to form. Each chromosome consists of a pair of chromatids connected by a centromere. Cells are now 4N, 4C. The major occurrence in this phase is the coupling of these homologous chromosomes. Two double-stranded chromosomes form a four-stranded tetrad. In some cases, there is crossing-over of the two middle strands, at a site called the chiasma, such that there is genetic recombination. This process is extremely important for creating genetic diversity.
In Metaphase I, the tetrads line up on the "equator" of the cell. The centrosome has replicated and one has moved to each pole. Microtubules that extend out of each centrosome attach to kinetochores in the center of each side of the tetrads that have lined up on the equator.
5.2View more presentations from maieymuhamad.
Mitosis is a process of cell division which results in the production of two daughter cells from a single parent cell. The daughter cells are identical to one another and to the original parent cell.
In a typical animal cell, mitosis can be divided into four principals stages:
