Anke Hemmerling MD, PhD, MPH

• Director, Interdisciplinary MPH Program

https://publichealth.berkeley.edu/people/anke-hemmerling/

CellSurfaceExtensions Most cells have surface extensions of one or more types called microvilli ritalin causes erectile dysfunction generic levitra 10 mg, cilia impotence problems levitra 10 mg purchase line, flagella impotence from steroids order levitra line, and pseudopods erectile dysfunction medication for sale purchase levitra paypal. They are best developed in cells specialized for absorption erectile dysfunction symptoms age buy levitra 10 mg low price, such as the epithelial cells of the small intestine and kidney tubules. On cells of the taste buds and inner ear, they are well developed but less numerous, and instead of absorptive functions, they serve sensory roles such as detecting food chemicals or sound. They are supported by a core of microtubules that, in cross section, looks a bit like a Ferris wheel. Each pair of microtubules is equipped with little motor proteins that produce the beating motion of the cilium. Cells of the respiratory tract and uterine (fallopian) tubes typically have about 50 to 200 cilia each (fig. In the respiratory tract, they move mucus from the lungs and trachea up to the throat, where it is swallowed. In the uterine tubes, they move an egg or embryo toward the uterus, like people in a stadium passing a beach ball overhead from hand to hand. The light-absorbing parts of the retinal cells in the eye are elaborately modified primary cilia; in the inner ear, they play a role in the senses of motion and balance; and in kidney tubules, they are thought to monitor fluid flow. B the microvilli are anchored by protein filaments, which occupy the core of each microvillus and project into the cytoplasm. The glycocalyx is composed of short carbohydrate chains (oligosaccharides) bound to the membrane phospholipids and proteins. Fawcett/Science Source glyco=sugar;calyx=cup,vessel 4 micro=small;villi=hairs 5 cilia=hairs 3 Name an organ of the body from which this cell might have come. The short, mucus-secreting cells between the ciliated cells show bumpy microvilli on their surfaces. The only functional flagellum in humans is the whiplike tail of a sperm cell, measuring about 50 µm long (see fig. It has a core of microtubules like a cilium, but it is stiffened by a sheath of filaments in a space between those and the plasma membrane. Sperm use the tail to crawl like a snake up the mucous membrane of the uterus and uterine tubes in their quest to find an egg. Pseudopods Pseudopods7 are cytoplasm-filled extensions of the cell ranging from filamentous to blunt fingerlike processes (fig. They change shape continually; some form anew as the cell surface bubbles outward and cytoplasm flows into it, usually at the leading end of a moving cell, while others at the "tail" end are retracted into the cell. Some white blood cells use pseudopods to crawl about in the tissues, and when they encounter a bacterium or other foreign particle, they reach out with pseudopods to surround and engulf it. Tissue cells called macrophages snare bacteria with thin filamentous pseudopods and "reel them in" to be digested by the cell. Like little janitors, macrophages and white blood cells keep our tissues cleaned up and defend us against bacteria and other invaders. CellJunctions In complex multicellular organisms, no cell is independent of the others. Proteins at the cell surface form cell junctions that link cells together and attach them to the extracellular material. Such attachments enable cells to grow and divide normally, resist stress, and communicate with each other. The three principal types of junctions between cells are tight junctions, desmosomes, and gap junctions (fig. A tight junction completely encircles an epithelial cell near its upper end and joins it securely to adjacent cells, somewhat like the plastic harness on a six-pack of soda cans. The junctions are formed by the fusion of the plasma membranes of neighboring cells, and seal off the intercellular space. Substances are restricted from passing between the epithelial cells, but rather must pass through them, ensuring that the epithelial cells chemically process materials that travel across. In the stomach and intestines, for example, tight junctions prevent digestive juices from leaking between epithelial cells and digesting the underlying tissue, and they help prevent bacteria from invading the tissues. In some cases, however (such as the kidneys and small intestine), these "tight" junctions can be quite leaky and allow appreciable movement of water and solutes between cells. Without them, your skin would peel off when you rubbed it, a swallow of food would scrape away the lining of your esophagus, and a heartbeat would pull your cardiac muscle cells apart. Tight junction Desmosome Cytoskeletal proteins A gap junction is formed by a ring of six proteins arranged somewhat like the segments of an orange, surrounding a water-filled channel. Ions, glucose, amino acids, and other small solutes can diffuse through the channel directly from the cytoplasm of one cell into the next. In the human embryo, nutrients pass from cell to cell through gap junctions until the circulatory system forms and takes over the role of nutrient distribution. In cardiac muscle, gap junctions allow electrical excitation to pass directly from cell to cell so that the cells contract in near unison. These membranes cannot be impenetrable, like brick walls, but must allow chemicals to pass through. Otherwise nutrients and oxygen could never leave the bloodstream to serve the tissues, cells could not take up needed substances or get rid of wastes, and organelles could not exchange materials with the rest of the cytoplasm. These membranes are all selectively permeable, allowing some substances to pass through while holding back others. The resulting breakdown of desmosomes between the cells leads to widespread blistering of the skin and oral mucosa, loss of tissue fluid, and sometimes death. An everyday example is the process of brewing coffee, where water pressure (weight of the water) drives water and dissolved matter through the paper filter while holding the coffee grounds back. The most important example in the human body is blood pressure driving water and small solutes through gaps in the walls of the capillaries, while holding blood cells and large molecules such as proteins in the bloodstream. Filtration is the mechanism by which salts, nutrients, and other blood solutes are delivered to the cells of surrounding tissues, and how the kidneys selectively filter wastes from the blood. Low concentration (a) Simple di usion Solute binds to receptor site on transport protein. This is how oxygen and steroid hormones enter cells and carbon dioxide leaves them, for example. Molecules can diffuse through both living membranes (the plasma membrane) and nonliving ones (such as dialysis tubing and cellophane) if the membrane has large enough gaps or pores. Nonpolar solutes such as oxygen and carbon dioxide, and hydrophobic substances such as steroids, diffuse through the lipid regions of the plasma membrane; hydrophilic solutes such as salts, however, can diffuse only through the water-filled protein channels of the membrane. Low concentration Receptor site (b) Facilitated di usion Solute binds to receptor site on transport protein. The reason it occurs is that when water molecules move to the high-solute side, they tend to loosely cling to the solute molecules. Becoming less mobile, they are not as able to break free and cross back to the low-solute side; there are more water molecules on the low-solute side free to pass through the membrane than there are on the high-solute side. Thus, if the fluids on two sides of a cell membrane differ in the concentration of dissolved matter (and these solutes cannot penetrate the membrane), water tends to move by osmosis from the more dilute to the less dilute side. For example, blood capillaries absorb fluid from the tissues by osmosis, thereby removing metabolic wastes from the tissues and preventing them from swelling. If a cell is in balance with the surrounding fluid, it gains and loses water at equal rates and maintains a stable volume and internal pressure. If there is an osmotic imbalance, however, the cell may shrivel and die from loss of water or swell with excess water and potentially burst. Either of these can be fatal to the person, as seen in the many cases of people who have died of dehydration or, conversely, because they lost water and electrolytes through urine and sweat and tried to replace their losses by drinking large volumes of plain water. The ability of a solution to affect intracellular pressure and volume is called tonicity. In an isotonic solution, cells gain and lose water at equal rates and cell volume remains constant (fig. However, hypertonic intravenous fluid is sometimes given deliberately to patients for such purposes as reducing swelling of the brain (cerebral edema) by drawing excess water out of the cells. The dashed line represents a selectively permeable membrane dividing the chamber in half. The large particles on side B represent any solute, such as protein, too large to pass through the membrane. Water passes predominantly from side A to side B and aggregates around the solute particles. For example, drugs called calcium channel blockers are often used to treat high blood pressure (hypertension). The walls of the arteries contain smooth muscle that constricts to narrow the vessels and raise blood pressure, or relaxes to let them widen and reduce blood pressure. Excessive, widespread vasoconstriction (vessel narrowing) can cause hypertension, so one approach to the treatment of hypertension is to inhibit vasoconstriction. In order to constrict, smooth muscle cells open calcium channels in the plasma membrane. Calcium channel blockers act, as their name says, by preventing calcium channels from opening and thereby preventing constriction. FacilitatedDiffusion the next two processes, facilitated diffusion and active transport, are called carriermediated transport because they employ carrier proteins in the plasma membrane. The carrier binds a particle on the side of a membrane where the solute is more concentrated, then releases it on the side where it is less concentrated. One use of facilitated diffusion is to absorb the sugars and amino acids from digested food. An especially important active-transport process is the sodium­potassium (Na+­K+) pump. About half of the calories that you "burn" every day are used just to operate your Na+­K+ pumps. VesicularTransport All of the processes discussed up to this point move molecules or ions individually through the plasma membrane. There are three forms of endocytosis: phagocytosis, pinocytosis, and receptor-mediated endocytosis. Some Pseudopod macrophages consume as much as 25% of their own volume in material per hour, thus living up to their name17 and playing a vital role in cleaning up the tissues. The membrane caves in at that point until a vesicle pinches off into the cytoplasm bearing the receptors and bound solute. One use of pinocytosis is seen in kidney tubule cells; they use this method to reclaim the small amount of protein that filters out of the blood, thus preventing protein from being lost in the urine. The receptors then cluster together and the membrane sinks in at this point, creating a pit. One use of receptor-mediated endocytosis is the absorption of insulin from the blood. It is used, for example, by digestive glands to secrete enzymes, by breast cells to secrete milk, and by sperm cells to release enzymes for penetrating an egg. A secretory vesicle in the cell migrates to the surface and fuses with the plasma membrane. A pore opens up that releases the product from the cell, and the empty vesicle usually becomes part of the plasma membrane. What property of phospholipid molecules causes them to organize themselves into a bilayer Which of these is important in determining blood transfusion compatibility: cell-adhesion molecules, membrane carriers, membrane cholesterol, the glycocalyx, or microvilli Compare and contrast microvilli and cilia in terms of their structure, function, and general location. Which type of cell junction best serves to keep food from scraping away the lining of your oral cavity Which type enables a cardiac muscle cell to electrically stimulate the neighboring cell Which type best serves to keep your digestive enzymes from eroding the tissues beneath your intestinal lining What membrane transport processes get all the necessary energy from the spontaneous movement of molecules These are classified into three groups-cytoskeleton, inclusions, and organelles-all embedded in the clear, gelatinous cytosol. It structurally supports a cell, determines its shape, organizes its contents, and-going beyond our office building analogy-transports substances within the cell and contributes to movements of the cell as a whole. It is connected to proteins of the plasma membrane and they in turn are connected to proteins external to the cell, so there is a strong structural continuity from the cytoplasm to the extracellular material. The cytoskeleton is composed of microfilaments, intermediate filaments, and microtubules. Microfilaments are about 6 nanometers (nm) thick and are made of the protein actin. They form a dense fibrous mesh called the terminal web on the internal side of the plasma membrane. The oily plasma membrane is spread out over the terminal web like butter on a slice of bread. It is thought that the membrane would break up into little droplets without this support. Intermediate filaments (8­10 nm in diameter) are thicker and stiffer than microfilaments. They contribute to the strength of the desmosomes and include the tough protein keratin that fills the cells of the epidermis and gives strength to the skin. They hold organelles in place, form bundles that maintain cell shape and rigidity, and act somewhat like monorails to guide organelles and molecules to specific destinations in a cell.

The three main criteria for diagnosis are as follows: Irremediable structural brain damage erectile dysfunction prevalence age cheap 20 mg levitra visa. Patients with hypothermia erectile dysfunction age young buy levitra 10 mg fast delivery, significant electrolyte imbalance or drug overdose are excluded impotence grounds for divorce levitra 10 mg buy with mastercard, but may be reassessed when these are corrected erectile dysfunction drug mechanism discount levitra 10 mg otc. In suitable cases erectile dysfunction drug samples levitra 10 mg purchase line, and provided the patient was carrying a donor card and/or the consent of relatives has been obtained, the organs of those in whom brainstem death has been established may be used for transplantation. The incidence rises steeply with age; it is uncommon in those under 40 years and is slightly more common in men. Definitions Stroke is defined as rapid onset of neurological deficit (usually focal), lasting >24 hours, which is the result of a vascular lesion and associated with 746 Neurology infarction of central nervous tissue. A completed stroke is when the neurological deficit has reached its maximum (usually within 6 hours). Stroke in evolution is when the symptoms and signs are getting worse (usually within 24 hours of onset). A minor stroke is one in which the patient recovers without a significant neurological deficit, usually within 1 week. Pathophysiology Different pathological events cause similar clinical events in cerebrovascular disease. Completed stroke Most strokes (85%) are caused by cerebral infarction due to arterial embolism or thrombosis. Thrombosis occurs at the site of an atheromatous plaque in carotid, vertebral or cerebral arteries. Emboli arise from atheromatous plaques in the carotid/vertebrobasilar arteries, or from cardiac mural thrombi. In about 15% of cases, stroke is caused by intracranial or subarachnoid haemorrhage. Less commonly, the clinical picture of stroke may be caused by intracranial venous thrombosis, multiple sclerosis relapse and a space-occupying lesion in the brain. With an abscess, the onset of symptoms and signs is usually much slower than in a stroke. In young adults, one-fifth of strokes are caused by carotid or vertebral artery dissection allowing blood to track within the wall of the artery and occlude the lumen. It should be considered in those with recent neck pain, trauma or manipulation of the neck. Risk factors the major risk factors for thromboembolic stroke are those for atheroma: i. Hypertension is the most modifiable risk factor: others are obesity, oestrogen-containing oral contraceptives, excessive alcohol consumption and polycythaemia (hyperviscosity syndromes). Atrial fibrillation is a major risk factor for embolic stroke (rate 1­5% per year depending on age). Rarer causes of stroke are migraine, Stroke and cerebrovascular disease 747 vasculitis, cocaine (by causing vasoconstriction), antiphospholipid syndrome (p. Transient ischaemic attacks There is a sudden onset of focal neurological deficit (usually hemiparesis and dysphasia) with symptoms maximal at the onset and usually lasting 5­15 minutes. Gradual progression of symptoms suggests a different pathology such as demyelination, tumour or migraine. Amaurosis fugax is painless transient monocular blindness as a result of the passage of emboli through the retinal arteries. The history and physical examination must include a search for risk factors and possible sources of emboli (atrial fibrillation, valve lesion, carotid bruits in the neck). Carotid artery imaging Carotid Doppler and duplex ultrasound scanning are performed (ideally within 1 week of onset of symptoms) to look for carotid atheroma and stenosis. Treatment Antithrombotic treatment Aspirin 300 mg should be given immediately and continued long term (75 mg once daily). Long-term anticoagulation with warfarin (after brain imaging) is given to patients in atrial fibrillation, with some valvular lesions (uninfected) or dilated cardiomyopathy. Other secondary prevention this involves advice and treatment to reverse risk factors (p. Carotid endarterectomy is recommended in patients with internal carotid artery stenosis >70%. Endarterectomy is associated with a mortality of approximately 3% and a similar risk of stroke. Stroke and cerebrovascular disease 749 Cerebral infarction Most thromboembolic cerebral infarctions cause an obvious stroke. The infarcted area is surrounded by a swollen area which can regain function with neurological recovery. The signs are contralateral to the lesion: hemiplegia (arm > leg), hemisensory loss, upper motor neurone facial weakness and hemianopia. Initially the patient has a hypotonic hemiplegia with decreased reflexes; within days this develops into a spastic hemiplegia with increased reflexes and an extensor plantar response, i. Brainstem infarction Brainstem infarction causes complex patterns of dysfunction depending on the sites involved: the lateral medullary syndrome, the most common of the brainstem vascular syndromes, is caused by occlusion of the posterior inferior cerebellar artery. Multi-infarct dementia (vascular dementia) is a syndrome caused by multiple small cortical infarcts, resulting in generalized intellectual loss; there is a stepwise progression with each infarct. The anterior cerebral artery supplies the medial surface of the hemisphere and the middle cerebral artery supplies the lateral surface of the hemisphere, including the internal capsule. Patients with a cerebellar infarct causing hydrocephalus or a large cerebral infarct with brain oedema and a risk of brain herniation should be referred for immediate neurosurgical evaluation. Detailed clotting studies and autoantibody screen to look for evidence of conditions associated with thrombophilia are indicated in younger patients with unexplained stroke. Echocardiography (in suspected cardioembolic stroke) and Stroke and cerebrovascular disease 751 Emergency Box 17. Demonstrates the site of the lesion; distinguishes between ischaemic/haemorrhagic stroke; identifies conditions mimicking stroke. Imaging is performed immediately (at the next scanning slot) in the following circumstances: patient presents within the time frame for thrombolysis early anticoagulation is indicated recent history of head injury severe headache at onset of stroke symptoms patient is taking anticoagulant treatment or has a known bleeding tendency depressed level of consciousness (Glasgow Coma Score <13). Aspirin 300 mg daily (orally, via nasogastric tube or rectally) should be given as soon as possible after the onset of stroke symptoms once a diagnosis of primary intracerebral haemorrhage has been excluded by brain imaging. It is given immediately if haemorrhage has been excluded in the emergency department provided that patients can be managed in an acute stroke service with appropriate support from a stroke physician. Blood pressure should only be lowered in the acute phase where there are likely to be complications of hypertension such as hypertensive encephalopathy, heart failure or aortic dissection. Feeding by fine-bore nasogastric tube or percutaneous gastrostomy may be necessary. Maintenance of hydration, frequent turning to avoid pressure sores and other supportive measures. High-dose aspirin (300 mg daily) is continued for 2 weeks before converting to clopidogrel. Anticoagulation is initiated immediately for cerebral venous thrombosis or arterial dissection, but delayed for 14 days after the onset of ischaemic stroke in atrial fibrillation due to the risk of bleeding into the infarcted area. Internal carotid endarterectomy or stenting reduces the risk of recurrent stroke (by 75%) in patients who have had an infarct and who have internal carotid artery stenosis which narrows the arterial lumen by more than 70%. It is considered in patients with a non-disabling stroke who are likely to have some recoverable function. Further management of the stroke patient centres on identification and treatment of risk factors (p. Optimal care is on a stroke rehabilitation unit that provides multidisciplinary services, coordinates disability-related medical care and trains caregivers. Physiotherapy is particularly useful in the first few months in reducing spasticity, relieving contractures and teaching patients to use walking aids. Following recovery, the occupational therapist plays a valuable role in assessing the requirement for and arranging the provision of various aids and modifications in the home, such as stair rails, hoists, or wheelchairs. Patients and relatives may gain useful information and support from a Stroke Association. Prognosis About one-quarter of patients will die in the first 2 years following a stroke; the prognosis is worse for bleeds than for infarction. Gradual improvement usually follows stroke, with a plateau reached 3­4 months after stroke onset, although one-third of long-term survivors are permanently dependent on the help of others. Only 25% of patients return to a level of everyday participation and physical functioning of community-matched persons who have not had a stroke. Stroke and cerebrovascular disease 753 Primary intracranial haemorrhage Intracerebral haemorrhage Intracerebral haemorrhage causes approximately 10% of strokes. Major risk factors for intracerebral haemorrhage are hypertension, excess alcohol consumption, increasing age and smoking. These risk factors lead to secondary vascular changes such as small vessel disease and arterial aneurysms which may eventually rupture and bleed. Anticoagulants should be stopped in patients with intracerebral haemorrhage and the effects reversed by prothrombin complex concentrate. A decision to restart anticoagulants (usually stopped for 7­10 days after an intracerebral haemorrhage) is made on a case-by-case basis. Measures to reduce intracranial pressure may be required, including mechanical ventilation and mannitol. Frequency of occurrence, a­e (decreasing order): a, anterior communicating artery; b, origin of the posterior communicating artery; c, trifurcation of the middle cerebral artery; d, termination of the internal carotid artery; e, basilar artery. Some, however, become symptomatic because of a mass effect, and the most common symptom is a painful third-nerve palsy. It is often accompanied by nausea and vomiting, and sometimes loss of consciousness. Some patients have experienced small warning headaches a few days before the major bleed. It shows subarachnoid or intraventricular blood in 95% of cases undergoing scanning within 24 hours of the haemorrhage; the sensitivity decreases after that time. Management Immediate management consists of bed rest and supportive measures with cautious control of hypertension. Nimodipine, a calcium-channel blocker, is given by mouth (60 mg 4-hourly) or by intravenous infusion (1­2 mg per hour via a central line) to reduce cerebral artery spasm, a cause of ischaemia and further neurological deterioration. Hyponatraemia (which contributes to delayed cerebral ischaemia) occurs due to urinary salt loss and patients may require large volumes of intravenous 0. Obliteration of the aneurysm by surgical clipping or endovascular coiling under radiological guidance prevents re-bleeding. Surviving patients should be advised on secondary prevention, especially on treatment of hypertension and the need to stop smoking. Prognosis Approximately 50% of patients die suddenly or soon after the haemorrhage. The outcome is variable in the survivors; some patients are left with major neurological deficits. Glasgow Coma Score on admission has the most prognostic significance; patients with a score >12 usually have a good outcome. It is almost always the result of head injury, often minor, and the latent interval between injury and symptoms may be weeks or months. Elderly patients and alcoholics are particularly susceptible because they are accident prone and their atrophic brains make the connecting veins more susceptible to rupture. The main clinical symptoms are headache, drowsiness and confusion, which may fluctuate. Clinically there is the picture of a head injury with a brief period of unconsciousness followed by a lucid interval of recovery. This is then followed by rapid deterioration with focal neurological signs and deterioration in conscious level if surgical drainage is not immediately carried out. Classification Seizures are classified clinically as partial or generalized (Table 17. There is a sudden onset of a rigid tonic phase followed by a convulsion (clonic phase) in which the muscles jerk rhythmically and the eyes remain open. The episode lasts typically for seconds to minutes, may be associated with tongue biting and incontinence of urine, and is followed by a period of (post-ictal) flaccid unresponsiveness followed by confusion or drowsiness lasting several hours. This is usually a disorder of childhood in which the child ceases activity, stares and pales for a few seconds only. Children with petit mal tend to develop generalized tonic­clonic seizures in adult life. There is isolated muscle jerking (myoclonic), intense stiffening of the body (tonic) or cessation of movement, falling and loss of consciousness (akinetic). Patients with focal seizures have symptoms depending on the area of the brain where the seizure starts, often the temporal lobe. The seizures may become generalized to affect the whole brain (secondary generalization). They typically result in jerking movements, typically beginning in the corner of the mouth or thumb and index finger, and spreading to involve the limbs on the opposite side of the epileptic focus. Temporal lobe seizures are associated with olfactory and visual hallucinations, blank staring, feelings of unreality (jamais-vu) or undue familiarity (djà-vu) with the surroundings. Known causes include cerebrovascular disease (15%), cerebral tumours (6%), alcohol-related seizures (6%) and post-traumatic epilepsy (2%). Occasionally, metabolic disturbances such as hypoglycaemia, acute hypoxia, hypocalcaemia, hyponatraemia, uraemia and hepatocellular failure present with convulsions. Primary epilepsies are due to complex developmental abnormalities of neuronal control; there are abnormalities in synaptic connections and distribution and release of neurotransmitters. Evaluation and investigation There are three steps in the evaluation of a patient with possible epilepsy: 1. The diagnosis is made clinically and a detailed description of the attack from an eye-witness is invaluable. Disorders causing attacks of altered consciousness must be differentiated from epilepsy (Table 17. Management Emergency measures the emergency treatment is to ensure that patients harm themselves as little as possible and that the airway remains patent.

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Aqueous humor is produced relatively constantly and drained by a structure called the scleral venous sinus erectile dysfunction doctor in kuwait generic levitra 10 mg with amex. Unlike aqueous humor impotence help buy discount levitra on line, vitreous humor is present at birth and remains relatively unchanged throughout life impotence while trying to conceive buy cheap levitra 10 mg on line. The outermost layer of the eyeball is the fibrous tunic erectile dysfunction treatment in jamshedpur levitra 20 mg buy with amex, which consists mostly of dense irregular collagenous connective tissue erectile dysfunction doctor cape town levitra 10 mg free shipping. It is white because of numerous collagen fibers that contribute to its thickness and toughness (in the same way a joint capsule or a ligament is tough and white). It is made chiefly of the ciliary muscle, smooth muscle fibers that control the shape of the lens. The photoreceptors known as rods are scattered throughout the retina and are responsible for vision in dim light and for peripheral vision. Cones, the second type of photoreceptor, are concentrated at the posterior portion of the retina. It is also known as the blind spot because its lack of photoreceptors means that this region can produce no images. When viewing nearer objects, however, additional "fine-tuning" refraction is needed by the lens. This is accomplished with the help of the ciliary muscle-when its smooth muscle fibers contract, the ciliary body moves closer to the lens and removes tension on the suspensory ligaments. This causes the lens to become rounder, an adjustment called accommodation which allows the lens to provide the additional refraction necessary to focus light on the retina. When the eye switches to a distant object again, the ciliary muscle relaxes, which moves the ciliary body farther away from the lens and puts tension on the suspensory ligaments. This flattens the lens and allows the cornea to again become the primary refractive medium. Sclera Iris 2 3 Use scissors to remove the adipose tissue surrounding the eyeball. Hold the eyeball at its anterior and posterior poles, and use a sharp scalpel or scissors to make an incision in the frontal plane. Take care to preserve the fragile retina-the thin, delicate yellow-tinted inner layer. In this procedure, you will see (no pun intended) firsthand the differences in vision produced by the rods and the vision produced by the cones. Have him or her continue to stare forward and attempt to read what you have written. Have your partner stand 20 feet in front of a Snellen eye chart and read down the chart, stopping with the smallest line read accurately. For example, a person with 20/40 vision can see at 20 feet what someone with perfect vision could see at 40 feet. Visual acuity: 9 5 With the lights still dimmed and your partner standing in the same place, hold a piece of dark green or dark blue paper over the Snellen chart. Visual acuity: Paper color: 7 In which scenario were visual acuity and color vision better Have your lab partner measure with a ruler the distance from the page to your eye with a ruler. These irregularities decrease visual acuity because these structures are unable to focus light precisely on the retina. The ossicles transmit vibrations from the tympanic membrane to the inner ear through a structure called the oval window, to which the stapes is attached. The vestibule is an egg-shaped bony cavity that houses structures responsible for static equilibrium, which refers to maintaining balance when the body is not moving. Situated at right angles to one another, the semicircular canals work together with the organs of the vestibule to maintain equilibrium. Their orientation allows them to be responsible for a type of equilibrium called rotational equilibrium. The cochlea has a hole in its lateral wall called the round window, which plays a role in allowing the perilymph in the cochlea to vibrate. The structures of the cochlea transmit sound stimuli via the cochlear portion of the vestibulocochlear nerve. Procedure 1 Model Inventory for the Ear Identify the following structures of the ear on models and diagrams, using this unit and your textbook for reference. As you examine the anatomical models and diagrams, record the name of the model and the structures you were able to identify on the model inventory in Table 9. Conductive hearing loss results from interference of sound conduction through the outer and/or middle ear. Sensorineural hearing loss results from damage to the inner ear or the vestibulocochlear nerve. Two clinical tests can help a healthcare professional determine whether hearing loss is conductive or sensorineural: the Weber test and the Rinne (rinn-ay) test. The tuning forks are placed either directly on the bones of the skull to evaluate bone conduction-the ability to hear the vibrations transmitted through the bone-or in front of the ear, to evaluate air conduction-the ability to hear the vibrations transmitted through the air. If it is ringing too loudly, grasp the tines to stop it from ringing, and try again. Ask your partner whether the sound is heard better in one ear or whether the sound is heard equally in both ears. Time the interval during which your partner can hear the sound by having your partner tell you when the ringing stops. Time interval in seconds: After your partner can no longer hear the ringing, quickly move the still-vibrating tuning fork 1 to 2 cm lateral to the external auditory canal (the fork should not be touching your partner at this point). Time the interval from the point when you moved the tuning fork in front of the external auditory canal to when your partner can no longer hear the sound. For example, if the boneconducted sound was heard for 15 seconds, the air-conducted sound should be heard for 30 seconds. What type of deafness is present if the bone-conducted sound is heard longer than the air-conducted sound Under normal conditions, the vestibular apparatus should be able to maintain equilibrium in the absence of visual input. If the vestibular apparatus is impaired, however, the brain relies on visual cues to maintain balance. Procedure 4 Romberg Test 1 2 3 Have your partner stand erect with the feet together and the arms at the sides in front of a whiteboard. Have your partner stand in front of the whiteboard for 1 minute, staring forward with eyes open. Use the lines on either side of the torso to note how much your partner sways while standing. Again note the amount of side-to-side swaying, using the marker lines for reference. Their axons, which are collectively called cranial nerve I or the olfactory nerve, penetrate the holes in the Head and neck models cribriform plate to synapse on the olfactory bulb, which then sends the Tongue model impulses down the axons of the olfactory tract to the olfactory cortex. Of the four types of papillae-filiform, fungiform, foliate, and circumvallate-all but filiform papillae house taste buds. Fungiform papillae are scattered over the surface of the tongue, whereas the large circumvallate papillae are located at the posterior aspect of the tongue, arranged in a "V" shape. Foliate papillae contain taste buds primarily during childhood; they are located on the lateral aspects of the tongue. Taste bud 254 n Exploring Anatomy & Physiology in the Laboratory: Core Concepts Procedure 1 Model Inventory for Olfaction and Taste Identify the following structures of the olfactory and taste senses on anatomical models and charts. These receptors are not distributed throughout the skin equally, but instead are concentrated in certain regions of the body. The following experiments will allow you to determine the relative distribution of the receptors for touch in the skin by performing two tests: the error of localization and two-point discrimination. Every region of the skin corresponds to an area of the primary somatosensory cortex of the cerebrum. Some regions are better represented than others and, therefore, are capable of localizing stimuli with greater precision than are less well-represented areas. The error of localization (also called tactile localization) tests the ability to determine the location of the skin touched and demonstrates how well represented each region of the skin is in the cerebral cortex. Water-soluble marking pens (two colors) Ruler 2 wooden applicator sticks (or toothpicks) Alcohol swabs Error of Localization Procedure 1 Testing Error of Localization 1 2 3 Have your partner sit with his or her eyes closed. Using a different color of marker, have your partner, still with his or her eyes closed, place a mark as close as possible to where he or she believes the original spot is located. Areas that have a higher density of touch receptors are better able to distinguish between multiple stimuli than those with fewer touch receptors. Repeat this procedure until your partner can distinguish two separate points touching his or her skin. Considering the type of cells located in the macula lutea, which type of vision do you think a sufferer of macular degeneration would lose It involves the use of a laser to reshape the cornea in individuals suffering from astigmatism, near-sightedness (myopia), or far-sightedness (hyperopia). What results would you expect from the Rinne and Weber tests in an individual with noise-induced hearing loss Pre-Lab Exercise 10-1 Pre-Lab exercises Pre-Lab Exercise 1 Complete the following exercises prior to coming to lab, using your textbook and lab manual for. The glands work closely with the other system that maintains the homeostasis of multiple physiological variables-the nervous system. In contrast, the endocrine system brings about its effects via the secretion of hormones-chemicals released into the bloodstream that typically act on distant targets. The effects of hormones are not immediate, but they are longer-lasting than those of the nervous system. In general, hormones regulate the processes of other cells, including inducing the production of enzymes or other hormones, changing the metabolic rate of a cell, and altering permeability of the plasma membrane. You might think of hormones as the "middle managers" of the body, because they communicate the messages from their "bosses" (the endocrine glands) and tell the "workers" (other cells) what to do. Others, however, secrete hormones as a secondary function, examples of which are the heart (atrial natriuretic peptide), adipose tissue (leptin), the kidneys (erythropoietin), and the stomach (gastrin). This unit introduces you to the anatomy, histology, and physiology of the endocrine organs and hormones. To close out this unit, you will play "endocrine detective" and solve two "endocrine mysteries. The first, called inhibiting and releasing hormones, are those that inhibit and stimulate secretion from the anterior pituitary gland, respectively. In response to hypothalamicreleasing hormones, the anterior pituitary gland secretes hormones that stimulate other endocrine and exocrine glands in the body. The releasing and inhibiting hormones are synthesized by hypothalamic neurons and enter capillaries in the hypothalamus, after which they travel through small veins in the infundibulum. They then enter a second capillary bed in the anterior pituitary, where they exit the blood and interact with anterior pituitary cells to influence their functions. The anterior pituitary gland mostly produces hormones known as tropic hormones, or those that influence the functions of other glands. The thyroid gland is located in the anterior and inferior neck superficial to the larynx. It consists of right and left lobes connected by a thin band of tissue called the isthmus. T3 is the most active of the two hormones and acts on essentially all cells in the body to increase the metabolic rate, increase protein synthesis, and regulate the heart rate and blood pressure, among other things. Calcitonin is secreted when calcium ion levels in the blood rise, and it triggers osteoblast activity and bone deposition. It triggers osteoclast activity and resorption of bone tissue, increased calcium ion absorption from the intestines, and increased calcium ion reabsorption from the kidneys. It is large and active in infancy and early childhood, during which time it secretes hormones that stimulate the development of T lymphocytes within the thymus. In adults, most of the thymic tissue is gradually replaced by fat and other connective tissue. The middle zone secretes steroids, such as cortisol, that regulate the stress response, blood glucose, fluid homeostasis, and inflammation. The innermost zone secretes cortisol and steroids called androgens that affect the gonads and other tissues. When stimulated by the sympathetic nervous system, the cells of the adrenal medulla secrete the catecholamines epinephrine and norepinephrine into the blood. These adrenal catecholamines have the same effects on target cells as the norepinephrine and epinephrine released by sympathetic neurons. Secretion of adrenal catecholamines prolongs the sympathetic response, and these hormones are able act on target cells that are not innervated by sympathetic neurons. Its exocrine functions are carried out by groups of cells called pancreatic acini. Insulin, which is produced by cells called beta cells, triggers the uptake of glucose by cells, which decreases the concentration of glucose in the Blood blood. The testes are the male reproductive organs that produce sperm cells, the male gametes. Cells within the testes called interstitial cells produce the steroid hormone testosterone. This hormone promotes the production of sperm cells and the development of male secondary sex characteristics, such as a deeper voice, greater bone and muscle mass, and facial hair. The ovaries are the female reproductive organs that produce oocytes, the female gametes. Estrogens play a role in the development of oocytes, female secondary sex characteristics such as breasts and subcutaneous fat stores, and a variety of other processes. Note that human torso models are typically a good place to start when studying the endocrine system because most of the organs are easy to find. The one exception is the thymus; many torsos and models choose not to show this structure because it is fairly inactive in adults.

Type I tympanoplasty describes the reconstruction of the tympanic membrane in the presence of an intact and mobile ossicular chain causes of erectile dysfunction in 20 year olds discount 10 mg levitra overnight delivery. The tympanic membrane is reconstructed to lie on the stapes head to create a columella effect or myringostapediopexy erectile dysfunction quality of life purchase genuine levitra online. The same principle is applied with some ossiculoplasty procedures erectile dysfunction treatment garlic discount levitra 20 mg amex, where the stapes superstructure or footplate is in contact with the reconstructed tympanic membrane via a prosthesis back pain causes erectile dysfunction safe levitra 10 mg. The main indications for tympanoplasty are chronic secretory otitis media erectile dysfunction treatment ayurveda purchase 10 mg levitra amex, either mucosal (tympanic membrane perforation) or with cholesteatoma, and the surgical management of pars tensa retraction pockets. These conditions often result in ear discharge (otorrhoea), conductive hearing loss, and the social inconvenience of being unable to get the ear wet. If there is a pars tensa retraction pocket, it is helpful to use the descriptive Sade classification (See Table 14. Alternatives to surgery In addition to discussing surgery, it is important to advise patients of the alternatives available to them. In the case of a central perforation, these include observation coupled with water precautions, particularly if there are few symptoms and the impact on lifestyle is minimal. Procedure steps Injection of local anaesthetic the use of a local anaesthetic such as 2% with 1:80,000 adrenaline is used to aid vasoconstriction and postoperative analgesia. The procedure can be performed under local anaesthetic, but general anaesthesia is more common. The ear canal skin is infiltrated with local anaesthetic providing hydrodissection, thus making it easier to dissect and less likely to bleed. It is helpful to start inferiorly and work superiorly to prevent bleeding from the edge obscuring the view. The small perforations are joined together and the inner ring of tissue can be gently pulled away using crocodile or cupped forceps leaving a freshened and slightly larger perforation. In particular, discuss the need for intraoperative hypotension to reduce bleeding and lack of paralysis to enable facial nerve monitoring. Patients are placed supine, with their head on a head ring, rotated away from the operative ear. We recommend the use of a facial nerve monitor if it is used for all otological cases (other than insertion of a grommet). The entire theatre team becomes familiar with how to set it up and there is no ambiguity as to whether it is required for a particular procedure. Strapping patients to the table is helpful and allows them to be rotated during surgery, which can improve visualization of middle ear structures. A useful check list prior to scrubbing up is to consider five Ss: Side - correct side Adequate exposure of the entire perforation is essential and will influence which approach is used. It may also be necessary to perform a limited canalplasty to remove any bone obscuring the view of the perforation, particularly if there is an anterior canal wall overhang obscuring an anterior perforation. Postauricular ­ A curved incision is made approximately 1 cm behind the postauricular crease through the skin and subcutaneous tissue onto the temporalis fascia in its upper half. Tapes passed through the ear canal and out via the reentry incision can be used to retract the pinna and lateral meatal skin out of the field of view. Preauricular (endaural) ­ An incision is made just anterior to the anterior helix of the pinna and runs inferiorly between the helix and the tragus. The meatal skin lateral to this limb can then be elevated laterally over the bony margin of the ear canal. The flap is elevated using an elevator such as a Rosen ring until the annulus is reached. By entering the middle ear postero-inferiorly, injury to the chorda tympani is minimized. Tympanoplasty 89 Graft harvest the two commonest graft materials used are temporalis fascia and a composite cartilage perichondrium graft. Cartilage can be harvested from the concha cymba, concha cavum or fossa triangularis if using a post-auricular incision, or from the tragus if performing a permeatal or end-aural approach. The composite perichondrium cartilage graft technique uses a single shield or island-shaped graft that remains attached to its perichondrium to reconstruct part or all of the tympanic membrane. Cartilage composite grafts have a very high success rate for repair of both small and large perforations, and are resilient to retraction without adversely affecting hearing outcomes (3). Graft sizing A helpful technique is to cut a paper template to accurately size the perforation or region of tympanic membrane that requires reconstruction. If using a composite island graft, the cartilage can be trimmed to the size of the perforation, while retaining a perichondrial apron to aid with graft placement. Ear packing the surface of the tympanic membrane is gently covered to protect it and allow epithelium to grow over the graft. Closure the wounds are closed in layers, preferably with an absorbable suture such as 4/0 Vicryl or Monocryl. The majority of myringoplasty cases can be performed as day surgery, particularly if performed permeatally. Postoperative follow-up is usually 2­4 weeks after surgery, at which time the dressings are removed from the ear. The local anaesthetic, hypotensive general anaesthetic, surgical approach and ability to manoeuvre the operating table combine to provide the best surgical conditions. Cartilage tympanoplasty: Indications, techniques and outcomes in a 1000 patient series. For access ­ the mastoid component of the temporal bone acts as a conduit for a number of surgical procedures, including hearing implantation surgery (cochlear and middle ear), endolymphatic sac surgery, labyrinth surgery (posterior or superior semicircular canal occlusion and osseous labyrinthectomy) and translabyrinthine approaches to the internal auditory canal and cerebellopontine angle (vestibular schwannoma surgery). The combination of enzyme production and pressure necrosis can result in the destruction of bony structures, including the ossicles and otic capsule. As with any otological procedure, the condition of the contralateral ear is an important consideration. Does it originate in the attic, from a marginal perforation or a pars tensa retraction pocket Investigations Pure tone audiometry, including air conduction and appropriately masked bone conduction, is an essential part of the assessment and should be performed within 3 months of surgery. A number of different mastoidectomy techniques can be employed in the treatment of cholesteatoma. A good otologist should be trained in all three techniques so that the procedure performed can be tailored to the specific disease and requirements of the patient. In the case of cholesteatoma, surgery is the only means of eradicating the disease and the associated complications. Observation is an option in selected cases, in particular, in patients who are symptom-free, too unfit for surgery or who decline surgery. Cholesteatoma in an only hearing ear is not an absolute contraindication to surgery, but it is advisable that any procedure be undertaken by an experienced otologist. Chorda tympani injury with taste disturbance (usually temporary even if the chorda is divided). Ensure that the anaesthetist is aware of the need for intra-operative facial nerve monitoring and relative hypotension to reduce bleeding. Most otologists regard the use of a facial nerve monitor for cholesteatoma surgery as mandatory if the hospital is in possession of the device. Strapping patients to the table is extremely helpful and allows them to be rotated during surgery to improve visualization of difficult areas. A useful checklist prior to scrubbing up is to consider five Ss: Side - is the side correct Tapes passed through the ear canal and out via the reentry incision are used to keep the pinna and lateral meatal skin retracted. This approach provides excellent exposure of the cortical bone of the mastoid and the root of the zygomatic process. The superior aspect of the tympanomeatal flap incision is taken right up to the margin of cholesteatoma. It may be necessary to divide the chorda tympani cleanly if it is involved in the disease. The resulting flap of posterior canal skin and tympanic membrane remnant is elevated and reflected anteroinferiorly. If the ossicular chain is intact, a decision regarding whether it will be possible to clear disease adequately without disrupting it must be made. With a more extensive cholesteatoma involving the mesotympanum, it may be necessary to remove disease in order to get a view of the incus and or stapes. If the incudostapedial joint is intact, it is divided with a joint knife and the incus carefully removed without damaging the stapes superstructure. The neck of the malleus is then divided with malleus nippers and the head of the malleus removed; the handle of malleus can either be removed or left in situ. Removal of the handle of malleus can make reconstruction simpler and reduce recurrent cholesteatoma. As bone is removed, air cells will come into view depending on the degree of sclerosis of the mastoid. It is important to find the tegmen and sigmoid sinus and then skeletonize them (leave a thin layer of bone) with a diamond burr. This ensures that optimal access is achieved and that the surgeon does not become lost down a deep dark hole. With the mastoid antrum open, the bony bulge of the lateral semicircular canal comes into view, as does the lateral process of the incus. Extreme caution is required as drilling on an intact ossicular chain may result in a sensorineural hearing loss. The dissection is continued anteriorly until the anterior attic is accessible; this can otherwise be a common site for residual disease. Throughout the procedure, cholesteatoma and granulations may require piecemeal removal in order to maintain visualization. The first step is to find the mastoid segment of the facial nerve while drilling parallel to it with copious irrigation. Once located, it is possible to remove the bone lateral to the nerve in order to encounter the intra-osseous chorda. By removing the bone between the facial nerve and chorda tympani, the facial recess is opened, providing a view of the stapes (if present) and sinus tympani. In addition to the anterior attic, the sinus tympani is a frequent site for residual cholesteatoma; a good posterior tympanotomy provides optimal visualization of this tricky area which can be supplemented with angled otoscopes. Cartilage is harvested from the concha cymba or concha cavum via the postauricular incision. A tape passed through the canal and brought out through the mastoid cavity can be used to remove residual squames from the bony margin. A paper template is prepared to size the attic and tympanic membrane reconstruction is required. This is done prior to harvesting the cartilage to ensure a large enough piece of cartilage is taken. Once harvested, the cartilage is shaped to the template (taking care to place the lateral aspect of the template on the cartilage) leaving a peripheral apron of perichondrium surrounding the cartilage. The cartilage is scored down to perichondrium, twice horizontally and twice vertically. The result is nine separate pieces, resembling a chessboard, that are attached to the perichondrium. This technique removes the natural convexity of conchal cartilage and makes the graft easier to manipulate in the ear. The graft is placed in the middle ear in an underlay fashion with the perichondrium laterally. The perichondrium is placed over the bony meatal wall, lateral to the bony annulus, but medial to the annular ligament and tympanomeatal flap, to anchor the graft and prevent medialization. The cartilage should extend snugly to the bony annulus or overlap if there is concern about recurrence. The head of the prosthesis lies against the undersurface of the cartilage checkerboard. A postoperative lower motor neurone palsy is extremely worrying and the operating surgeon must be informed. While the palsy may be due to the local anesthetic, if the nerve fails to recover, surgical exploration by the operating surgeon and a second senior otologist is required. Mastoidectomy 97 A Weber test or scratch test is also performed to confirm that there is still hearing in the operated ear. While the majority of mastoidectomy cases require an overnight stay, an increasing number are being performed as day-case procedures. Cartilage tympanoplasty: indications, techniques and outcomes in a 1,000 patient series. The term has come to refer to the operation in which the stapes superstructure is replaced by an artificial piston attached to the incus (typically) and placed through a fenestration in the stapes footplate (stapedotomy). Stapedectomy typically involves removal of the stapes crura, fenestration of the footplate and the insertion of an artificial piston. Otosclerosis affects the bone of the otic capsule, leading to new bone formation around the edge of the oval window and stapes footplate. Eventually, the stapes becomes fixed, resulting in reduced transmission of sound to the cochlea and significant conductive hearing loss. It is commonly (70%) a bilateral condition in patients with a family history of hearing loss. However, due to variable penetrance and expression, it does not affect every generation. Stapedectomy 99 Examination Tuning fork tests are useful to confirm clinically a conductive hearing loss. It is necessary to document the state of both ears and exclude other causes of conductive hearing loss.

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