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Hair Cells

Hair Cells

Hair cells are the sensory receptors of the auditory system—they transduce mechanical sound waves into electrical energy that the nervous system can understand. Hair cells are located in the organ of Corti within the cochlea of the inner ear, between the basilar and tectorial membranes. The actual sensory receptors are called inner hair cells. The outer hair cells serve other functions, such as sound amplification in the cochlea, and are not discussed in detail here.

Accessory Structures of the Skin: Hair and Hair Follicles

Accessory Structures of the Skin: Hair and Hair Follicles

Hair and hair follicles are integral components of the integumentary system. Hair is a filamentous structure composed mainly of a protein called keratin. It is found on the surface of the skin throughout the body, except for areas such as the palms of the hands and soles of the feet.
Hair is a keratinous filament growing out of the epidermis. It is primarily made of dead, keratinized cells. Hair strands originate at the epidermal penetration called the hair follicle. The hair shaft is the part...

Second Order systems II

Second Order systems II

In an underdamped second-order system, where the damping ratio ζ is between 0 and 1, a unit-step input results in a transfer function that, when transformed using the inverse Laplace method, reveals the output response. The output exhibits a damped sinusoidal oscillation, and the difference between the input and output is termed the error signal. This error signal also demonstrates damped oscillatory behavior. Eventually, as the system reaches a steady state, the error diminishes to zero.

First Order Systems

First Order Systems

First-order systems, such as RC circuits, are foundational in understanding dynamic systems due to their straightforward input-output relationship. Analyzing their responses to different input functions under zero initial conditions reveals significant insights into system behavior.
When a first-order system is subjected to a unit-step input, its response is characterized by its transfer function. By applying the Laplace transform of the unit-step input to the transfer function, expanding the...

Second Order systems I

Second Order systems I

A servo system exemplifies a second-order system, featuring a proportional controller and load elements that ensure the output position aligns with the input position. The relationship between these components is described by a second-order differential equation. Applying the Laplace transform under zero initial conditions yields the transfer function, showing how inputs are converted to outputs in the system.
By reinterpreting the system, one can derive the closed-loop transfer function, which...

Thermodynamic Systems

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A thermodynamic system is a set of objects whose thermodynamic properties are of interest. The system is considered to be embedded in its surroundings or the environment. The system and its environment can exchange heat and do work on each other through a boundary that separates them. However, the immediate surroundings of the system interact with it directly and therefore have a much stronger influence on its behavior and properties.
Consider an example of tea boiling in a kettle. The...

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Hair and systemic disease.

¹Department of Dermatology, Uniformed Services University, Bethesda, Maryland, USA. lsperling@usuhs.mil

Dermatologic Clinics

|November 14, 2001

Summary

This summary is machine-generated.

Hair loss (alopecia) and excess hair growth (hypertrichosis, hirsutism) can signal underlying systemic diseases. Categorizing these hair disorders aids in diagnosing internal conditions through clinical evaluation and pathology.

Related Experiment Videos

Area of Science:

Dermatology
Internal Medicine
Pathology

Background:

Hair loss (alopecia) and excess hair growth are common dermatological manifestations.
These conditions can indicate various underlying systemic diseases.
Understanding hair disorders is crucial for comprehensive patient care.

Purpose of the Study:

To categorize the main types of hair loss and excess hair growth.
To discuss the systemic diseases associated with these hair conditions.
To highlight the diagnostic utility of clinical and histopathologic evaluation.

Main Methods:

Review and categorization of hair disorders into five general groups: telogen effluvium, anagen arrest, follicular destruction, hair miniaturization, and hair shaft defects.
Classification of increased hair density into hypertrichosis and hirsutism.
Emphasis on the role of patient history, physical examination, and histopathologic data.

Main Results:

Hair loss and excess hair are linked to numerous systemic conditions.
The five categories of hair loss and two categories of excess hair provide a framework for understanding.
Diagnostic data typically allows for categorization and suggests underlying systemic disease.

Conclusions:

Hair disorders are important indicators of systemic health.
A systematic approach to categorizing hair abnormalities aids diagnosis.
Clinical and histopathologic findings are key to identifying the cause of hair changes.