Persius/hicric huggingface dataset:
Bioavailability

# Overview
In pharmacology, bioavailability is used to describe the fraction of an administered dose of unchanged drug that reaches the systemic circulation, one of the principal pharmacokinetic properties of drugs. By definition, when a medication is administered intravenously, its bioavailability is 100%. However, when a medication is administered via other routes (such as orally), its bioavailability decreases (due to incomplete absorption and first-pass metabolism). Bioavailability is one of the essential tools in pharmacokinetics, as bioavailability must be considered when calculating dosages for non-intravenous routes of administration.

# Definition
Bioavailability is a measurement of the extent of a therapeutically active drug that reaches the systemic circulation and is available at the site of action.
It is expressed as the letter F.

# Absolute bioavailability
Absolute bioavailability measures the availability of the active drug in systemic circulation after non-intravenous administration (i.e., after oral, rectal, transdermal, subcutaneous administration).
In order to determine absolute bioavailability of a drug, a pharmacokinetic study must be done to obtain a plasma drug concentration vs time plot for the drug after both intravenous (IV) and non-intravenous administration. The absolute bioavailability is the dose-corrected area under curve (AUC) non-intravenous divided by AUC intravenous. For example, the formula for calculating F for a drug administered by the oral route (po) is given below.
F = \frac{_{po}*dose_{IV}}{_{IV}*dose_{po}}
Therefore, a drug given by the intravenous route will have an absolute bioavailability of 1 (F=1) while drugs given by other routes usually have an absolute bioavailability of less than one.

# Relative bioavailability
This measures the bioavailability of a certain drug when compared with another formulation of the same drug, usually an established standard, or through administration via a different route. When the standard consists of intravenously administered drug, this is known as absolute bioavailability.
\mathit{relative\ bioavailability} = \frac{_{A}*dose_{B}}{_{B}*dose_{A}}

# Factors influencing bioavailability
The absolute bioavailability of a drug, when administered by an extravascular route, is usually less than one (i.e. F<1). Various physiological factors reduce the availability of drugs prior to their entry into the systemic circulation,
Such factors may include, but are not limited to:
- poor absorption from the gastro-intestinal tract
- degradation or metabolism of the drug prior to absorption
- hepatic first pass effect
Each of these factors may vary from patient to patient, and indeed in the same patient over time. Whether a drug is taken with or without food will affect absorption, other drugs taken concurrently may alter absorption and first-pass metabolism, intestinal motility alters the dissolution of the drug and may affect the degree of chemical degradation of the drug by intestinal microflora. Disease states affecting liver metabolism or gastrointestinal function will also have an effect.
Biopsy template
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# Introduction to the Biopsy Page
- The page name should be "(Disease name) biopsy", with only the first letter of the title capitalized (e.g. Melanoma biopsy).
- Goal: To provide a description and examples the biopsy findings that may be associated with the disease you are describing.
- As with all microchapter pages linking to the main page, at the top of the edit box put {{CMG}}, your name template, and the microchapter navigation template you created at the beginning.
- Remember to create links within Wikidoc by placing ] around key words which you want to link to other pages. Make sure you makes your links as specific as possible. For example if a sentence contained the phrase anterior spinal artery syndrome, the link should be to anterior spinal artery syndrome not anterior or artery or syndrome.  For more information on how to create links click here.
- Remember to follow the same format and capitalization of letters  as outlined in the template below.
- You should include the name of the disease in the first sentence of every subsection.

# Overview

## Template
- First sentences
- Examples

# Key Biopsy Findings in (Disease Name)

# Biopsy Exams of (Disease Name)
Birch reduction
The Birch reduction is the organic reduction of aromatic rings with sodium in liquid ammonia to form 1,4-cyclohexadienes.  The reaction was invented by the Australian chemist Arthur John Birch (19151995) in 1944.  This reaction provides an alternative to catalytic hydrogenation, which usually reduces the aromatic ring all the way to a cyclohexane (after the initial reduction to a cyclohexadiene, catalytic reduction of the remaining (nonaromatic) double bonds is easier than the first reduction).
The metal can also be lithium or potassium and the hydrogen atoms are supplied by an alcohol such as ethanol or tert-butanol. Sodium in liquid ammonia gives an intense blue color due to a solvated electron.
Several reviews have been published.   

# Reaction mechanism
The first step of a Birch reduction is a one-electron reduction of the aromatic ring to a radical anion. Sodium is oxidized to the sodium ion Na+. This intermediate is able to dimerize to the dianion. In the presence of an alcohol the second intermediate is a free radical which takes up another electron to form the carbanion. This carbanion abstracts another proton from the alcohol to form the cyclohexadiene.
In the presence of an alkyl halide the carbanion can also engage in nucleophilic substitution with carbon-carbon bond formation. In substituted aromatics an electron-withdrawing substituent, such as a carboxylic acid, stabilizes a carbanion and the least-substituted olefin is generated. With an electron-donating substituent the opposite effect is obtained.  The reaction produces more of the less thermodynamically stable non-conjugated 1,4-addition product than the more stable conjugated 1,3-diene because the largest orbital coefficient of the HOMO of the conjugated pentadienyl anion intermediate is on the central carbon atom.  Once formed, the resulting 1,4-cyclohexadiene is unable equilibrate to the thermodynamically more stable product; therefore, the observed kinetic product is produced.  Experimental alkali metal alternatives that are safer to handle, such as the M-SG reducing agent, also exist.

# Birch alkylation
In Birch alkylation the anion formed in the Birch reduction is trapped by a suitable electrophile such as a haloalkane  for example in the reaction depicted below :
Biventer lobule

# Overview
The biventer lobule (or biventral lobule) is triangular in shape; its apex points backward, and is joined by the gray band to the pyramid.
The lateral border is separated from the inferior semilunar lobule by the postpyramidal fissure.
The base is directed forward, and is on a line with the anterior border of the tonsil, and is separated from the flocculus by the postnodular fissure.
Urinary bladder
Steven C. Campbell, M.D., Ph.D.

# Overview
In anatomy, the urinary bladder is a hollow, muscular, and distensible (or elastic) organ that sits on the pelvic floor in mammals. It is the organ that collects urine excreted by the kidneys prior to disposal by urination. Urine enters the bladder via the ureters and exits via the urethra.
In males, the bladder is superior to the prostate, and separated from the rectum by the rectovesical excavation.
In females, the bladder is separated from the rectum by the rectouterine excavation, and it is separated from the uterus by the vesicouterine excavation.

# Regions
- Trigone of urinary bladder: The ureters enter the bladder diagonally from its dorsolateral floor in an area called the trigone, which is a triangular shaped area on the postero-inferior wall of the bladder. The urethra exits at the lowest point of the triangle of the trigone.
- Apex: The Median umbilical ligament connects to the apex of the bladder.
- Neck: The Neck is connected to the pubic bone by the pubovesical ligament in women, and by the puboprostatic ligament in men.

# Wall
The wall of the urinary bladder consists of three layers:
- Mucosa: in this instance transitional epithelium & lamina propria
- Detrusor muscle: consists of an inner and outer longitudinal layer and a middle circular layer of smooth muscle
- a fibrous adventitia and the visceral peritoneum: lie on superior surface

# Detrusor muscle
The detrusor muscle is a layer of the urinary bladder wall made of smooth muscle fibers arranged in spiral, longitudinal, and circular bundles. When the bladder is stretched, this signals the parasympathetic nervous system to contract the detrusor muscle. This encourages the bladder to expel urine through the urethra.
For the urine to exit the bladder, both the autonomically controlled internal sphincter and the voluntarily controlled external sphincter must be opened. Problems with these muscles can lead to incontinence.
The urinary bladder usually holds 400620 mL of urine, but it can hold twice this without rupturing if, for example, the outflow is obstructed.
The desire to urinate usually starts when the bladder reaches around 75% of its working volume. If the subject is distracted the desire can fade and return with more urgency as the bladder continues to fill.
Bladder rupture

# Classification
Intraperitoneal bladder rupture
Occurs in approximately 10%20% of major bladder injuries.
Typically the result of a direct blow to the already distended bladder.
CT cystography demonstrates intraperitoneal contrast material around bowel loops, between mesenteric folds, and in the paracolic gutters
Intraperitoneal bladder rupture secondary to hip fractues
Extraperitoneal bladder rupture
Most common type of bladder injury (80%90% of cases).
'Usually caused by penetrating trauma
In blunt trauma, the presumed mechanism is direct laceration of the bladder by bone fragments from a pelvic fracture.
CR cystography reveals a variable path of extravasated contrast material.
Combined bladder rupture
Simultaneous intraperitoneal and extraperitoneal injury.
CT cystography usually demonstrates extravasation patterns that are typical for both types of injury.
Ptosis (eyelid)

# Overview
In ophthalmology, ptosis is an abnormally low position (drooping) of the upper eyelid. The drooping may be worse at night, when the individual's muscles are tired. This condition is sometimes incorrectly referred to as a "lazy eye," a separate condition known as Amblyopia. If severe enough and left untreated, the drooping eyelid can cause other conditions, like Amblyopia or Astigmatism. This is why it is especially important for this disorder to be treated in children at a young age, before it can interfere with vision development.

# Classification
Depending upon the cause it can be classified into:
- Neurogenic ptosis which includes IIIrd cranial nerve palsy, Horner's Syndrome, Marcus Gunn jaw winking syndrome, IIIrd cranial nerve misdirection.
- Myogenic ptosis which includes myasthenia gravis, myotonic dystrophy, ocular myopathy, simple congenital ptosis, blepharophimosis syndrome
- Aponeurotic ptosis which may be involutional or post-operative.
- Mechanical ptosis which occurs due to edema or tumors of the upper lid
- Neurotoxic ptosis which is a classic symptom of envenomation by elapids such as cobras or kraits etc. Neurotoxic ptosis is a precursor to respiratory failure and eventual suffocation caused by complete paralysis of the thoracic diaphragm. Urgent medical intervention is therefore required.

# Causes
Ptosis occurs when the muscles that raise the eyelid (levator or mueller muscle) are not strong enough to do so properly. It can affect one eye or both eyes and is more common in the elderly, as muscles in the eyelids may begin to deteriorate. One can, however, be born with ptosis, as it is hereditary (congenital ptosis.) Ptosis may be caused by damage/trauma to the muscle which raises the eyelid, or damage to the nerve which controls this muscle. Such damage could be a sign or symptom of an underlying disease such as diabetes mellitus, a brain tumor, and diseases which may cause weakness in muscles or nerve damage, such as myasthenia gravis.

# Treatment

## Surgery
Aponeurotic and congenital ptosis may require surgical correction if severe enough to interfere with vision or if cosmesis is a concern.
Treatment depends on the type of ptosis and is usually performed by an ophthamolic plastic and reconstructive surgeon, specializing in diseases and problems of the eyelid.
Surgical procedures include:
- Levator resection
- Mueller muscle resection
- Frontalis sling operation
Non-surgical modalities like the use of "crutch" glasses to support the eyelid may also be used.
Ptosis that is caused by a disease will improve if the disease is treated successfully.

# Well known persons with ptosis
- Salman Rushdie, novelist
- Thom Yorke, musician
- Paris Hilton, model/actress
- Tegan Quin, musician
- Gabrielle, singer
- Hayko Cepkin, musician
- Forest Whitaker, Hollywood Actor - won best actor oscar for 'The last king of Scotland'
- Fardeen Khan, Bollywood Actor

# Related Chapters
- Dermatochalasis
- Iris sphincter muscle
Bone conduction
Bone conduction is the conduction of sound to the inner ear through the bones of the skull.
Bone conduction is the reason why a person's voice sounds different to him/her when it is recorded and played back. Bone conduction
tends to amplify the lower frequencies, and so most people hear their own voice as being of a lower pitch than it actually is.
Some hearing aids employ bone conduction, achieving an effect equivalent to hearing directly by means of the ears. A headset is ergonomically positioned on the temple and cheek and the electromechanical transducer, which converts electric signals into mechanical vibrations, sends sound to the internal ear through the cranial bones.  Likewise, a microphone can be used to record spoken sounds via bone conduction.
Bone conduction products are usually categorized into three groups
- Ordinary products such as EARS-FREE headset or headphone
- Hearing Aids and Assistive listening devices
- Specialized communication products (i.e. underwater & high-noise environments)
Bone conduction products have following advantages over traditional headphones:
- Ears-free, thus providing extended use comfort and safety
- No electromagnetic waves (EMW), eliminating the potential effect of EMW on cerebrum (if any)
- High sound clarity in very noisy environments, can be used with hearing protection
- Can have the perception of stereo sound
There are some disadvantages:
- Some implementations require more power than headphones
- Less clear recording & playback than traditional headphones and microphone due to reduced frequency bandwidth
One example of a bone conduction speaker is a rubber over-moulded piezo-electric flexing disc about 40mm across and 6mm thick used by SCUBA divers. The connecting cable is moulded into the disc, resulting in a tough, water-proof assembly. In use the speaker is strapped against one of the dome-shaped bone protrusion behind the ear. As would be expected, the sound produced seems to come from inside the user's head, but can be surprisingly clear and crisp.
Bone conduction transmission can be used with individuals with normal or impaired hearing. There are several products on the market that exploit the bone conduction transmission pathway for sound. Some of these include the AquaFM and the SwiMP3 which are devices for transmitting sound to swimmers.
Bone hemostasis
Bone hemostasis is the process of controlling the bleeding from bone.
Bone is a living vascular organ containing channels for blood and bone marrow. When a bone is cut during surgery bleeding can be a difficult problem to control, especially in the highly vascular bones of the spine and sternum.  Bleeding from soft tissue is normally stopped using a cautery that creates heat, causing blood vessels to collapse and become sealed. Since the blood in living bone flows through channels in the bone that do not collapse, a cautery is not effective in preventing bone bleeding. Blocking the holes in the bone typically stops bone bleeding. This can be done by mechanically blocking the holes (tamponade effect), or by inducing a blood clot to form.
In the past the easiest and most common way to stop bone bleeding was to apply bone wax, which is made from beeswax. The bone wax is smeared across the bleeding edge of the bone, blocking the holes and causing immediate hemostasis. Because of the complications associated with the use of bone wax, newer water soluble hemostatic agents, such as those made from alkylene oxide copolymers have been developed.
Borel's paradox
Borel's paradox (sometimes known as the Borel-Kolmogorov paradox) is a paradox of probability theory relating to conditional probability density functions.  The paradox lies in fact that, contrary to intuition, conditional probability density functions are not invariant under coordinate transformations.
Suppose we have two random variables, X and Y, with joint probability density pX,Y(x,y). We can form the conditional density for Y given X,
where pX(x) is the appropriate marginal distribution.
Using the substitution rule, we can reparametrize the joint distribution with the functions U= f(X,Y), V = g(X,Y), and can then form the conditional density for V given U.
Given a particular condition on X and the equivalent condition on U, intuition suggests that the conditional densities pY|X(y|x) and pV|U(v|u) should also be equivalent. This is not the case in general.

# A concrete example

## A uniform distribution
We are given the joint probability density
The marginal density of X is calculated to be
So the conditional density of Y given X is
which is uniform with respect to y.

## Reparametrization
Now, we apply the following transformation:
Using the substitution rule, we obtain
The marginal distribution is calculated to be
So the conditional density of V given U is
which is not uniform with respect to v.

## The unintuitive result
Now we pick a particular condition to demonstrate Borel's paradox. The conditional density of Y given X = 0 is
The equivalent condition in the u-v coordinate system is U = 1, and the conditional density of V given U = 1 is
Paradoxically, V = Y and X = 0 is equivalent to U = 1, but
Varus deformity

# Overview
In orthopedics, a varus deformity is a term for the inward angulation of the distal segment of a bone or joint.  The opposite of varus is called valgus.
The terms varus and valgus always refer to the direction that the distal segment of the joint points.
For example, in a VARUS deformity of the knee, the distal part of the leg below the knee is deviated inward, resulting in a bowlegged appearance.  Conversely, a valgus deformity at the knee results in a knock-kneed appearance, with the distal part of the leg deviated outward.

# Terminology
The terminology is made confusing by the etymology of these words.
- In Latin, valgus actually means "knock-kneed" and varus means "bowlegged."
- In a knock-kneed person, the femur is deviated inward in relation to the hip, so the term varus is correctly applied for the hip, as it refers to the distal segment being angled inward.
- But in the same knock-kneed person, the opposite situation is found at the knee, with the distal segment now being deviated outward, so the term valgus is used for the knee.
- It is correct for a knock-kneed deformity to be called both a varus deformity at the hip/femur and a valgus deformity at the knee/tibia, although the common terminology is to refer to it as genu valgum.
If this is confusing, just remember that "varus = inward" and "valgus = outward" and always refers to the direction that the distal part of the joint points.
When the terminology specifies a bone rather than a joint, the bone is taken to be the distal segment of a joint.  Thus, a varus deformity of the tibia refers to the femur/tibia joint (the knee) and not the ankle joint.

# Examples
- Hip: coxa vara   the angle between the ball and the shaft of the femur is reduced, resulting in a limp.
- Knee: genu varum (from Latin genu = knee)  the tibia is turned inward in relation to the femur, resulting in a bowlegged deformity.
- Ankle: talipes varus (from Latin talus = ankle and pes = foot)  inward turning of the heel, resulting in clubfoot with the person walking on the outer part of the foot.
- Toe: hallux varus (Latin hallux = big toe)  inward deviation of the big toe away from the second toe.
- Elbows: cubitus varus (Latin cubitus = elbow)  turned inward elbows
Bowens disease

# Overview
Bowen's disease (BD) is a neoplastic skin disease, considered either as an early stage or intraepidermal form of squamous cell carcinoma. It was named after Dr John T. Bowen, the doctor who first described it in 1912.

# Causes
Causes of BD include solar damage, arsenic, immunosuppression (including AIDS), viral infection (human papillomavirus or HPV) and chronic skin injury and dermatoses.

# Signs and symptoms
Bowen's disease typically presents as a gradually enlarging, well demarcated erythematous plaque with an irregular border and surface crusting or scaling. BD may occur at any age in adults but is rare before the age of 30 years - most patients are aged over 60. Any site may be affected, although involvement of palms or soles is uncommon. BD occurs predominantly in women (70-85% of cases); about three-quarters of patients have lesions on the lower leg (60-85%), usually in previously or presently sun-exposed areas of skin. 
A persistent progressive non-elevated red scaly or crusted plaque which is due to an intradermal carcinoma and is potentially malignant. Atypical squamous (resembling fish scales) cells proliferate through the whole thickness of the epidermis. The lesions may occur anywhere on the skin surface or on mucosal surfaces. The cause most frequently found is trivalent arsenic compounds. Freezing, cauterization or diathermy coagulation is often effective treatment.

# Differentiating Bowen's disease from other diseases
Bowen's disease should be differentiated from other diseases causing papulosquamous or erythmatosquamous rash. The differentials include:

# Histology
Bowen's is equivalent to squamous cell carcinoma in situ. The entire tumor is confined to the epidermis and does not invade into the dermis. The cells in Bowen's are extremely unusual or atypical under the microscope and in many cases look worse under the microscope than the cells of many outright and invading squamous-cell carcinomas. The degree of atypia (strangeness, unusualness) seen under the microscope best tells how cells may behave should they invade another portion of the body.

# Treatment
Photodynamic therapy (PDT), Cryotherapy (freezing) or local chemotherapy (with 5-fluorouracil) are favored by some clinicians over excision. Because the cells of Bowen's disease have not invaded the dermis, it has a much better prognosis than invasive squamous cell carcinoma.