Medical dictionary | Hoan My

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H

Hearing loss
Hearing loss due to ageing, commonly termed presbycusis, is prevalent. Over half of individuals in the US over 75 experience some age-associated hearing decline. There are three types of hearing loss:
- Conductive, which involves the outer or middle ear.
- Sensorineural, which involves the inner ear.
- Mixed, which is a mix of the two.
Both ageing and exposure to loud noises can lead to hearing impairment. Other temporary causes, such as excessive earwax, can reduce auditory efficiency. Regaining lost hearing is typically impossible, though there are methods to enhance auditory perception.
Parts of the ear
The ear consists of three main sections: the outer ear, middle ear, and inner ear. Each segment contains specific structures that have unique functions in transforming sound waves into signals transmitted to the brain.
Outer ear
The outer ear consists of the visible portion of the ear (pinna) and the ear canal. The bowl-shaped pinna collects sound waves from the surroundings and funnels them into the ear canal.
Middle ear
The middle ear is an air-filled cavity that contains a trio of bones: the hammer (malleus), the anvil (incus), and the stirrup (stapes). The eardrum (tympanic membrane) divides these bones from the outer ear, which oscillates when hit by a sound wave. The middle ear links to the rear of your nose and the top section of your throat via a slender passage known as the auditory tube (eustachian tube). This tube periodically opens and shuts at its throat end to balance the middle ear’s pressure with the external environment and to drain any fluids. Balanced pressure on both sides of the eardrum is crucial for its standard oscillation.
Bones of the middle ear
The middle ear houses three-minute bones:
- Hammer (malleus) — connected to the eardrum
- Anvil (incus) — positioned centrally in the sequence of bones
- Stirrup (stapes) — linked to the membrane-shielded entrance that joins the middle ear to the inner ear (oval window)
The oscillation of the eardrum initiates a series of vibrations through these bones. Due to variations in size, contour, and alignment of these three bones, the intensity of the vibration amplifies by the time it approaches the inner ear. This amplification is essential to convey the sound wave’s energy to the inner ear’s fluid.
Inner ear
The inner ear comprises a series of interconnected chambers filled with fluid. One of these chambers, shaped like a snail and known as the cochlea, is pivotal in hearing. Vibrations from the middle ear bones are relayed to the cochlea’s fluids. Minute sensors, termed hair cells, within the cochlea transform these vibrations into electrical signals, which then journey via the auditory nerve to the brain. Here, initial deterioration and hearing impairment typically arise due to ageing, loud noise exposure, or certain medications. Additionally, the inner ear houses other fluid-filled sections, including three tubular structures known as the semicircular canals (vestibular labyrinth). When you move in any direction, hair cells within these canals perceive the fluid’s movement. These cells then change this motion into electrical signals that travel along the vestibular nerve to the brain, aiding in maintaining your equilibrium.
Travelling to the brain
Electrical signals travel via the auditory nerve, undergoing various stages of information processing. Signals originating from the right ear are directed to the auditory cortex situated in the left section of the brain’s temporal lobe. Conversely, signals from the left ear head towards the right auditory cortex. These auditory cortices categorise, process, interpret, and catalogue data related to the sound. By comparing and analysing all signals reaching the brain, you can discern specific sounds whilst relegating others as ambient noise.
Hand-foot-and-mouth disease
Hand-foot-and-mouth is a mild, infectious viral illness prevalent in young children. Common signs are ulcers inside the mouth and a rash on both hands and feet. The primary cause of hand-foot-and-mouth is typically a coxsackie virus. There isn’t a designated treatment for hand-foot-and-mouth. Regular hand hygiene and steering clear of individuals with the disease can reduce your child’s likelihood of catching it.
Hair loss
Hair loss, alopecia, can occur on your scalp or throughout your entire body. It can be a temporary or permanent condition caused by genetics, hormonal changes, medical conditions, or a natural part of ageing. Although hair loss can happen to anyone, it is more commonly experienced by men. Baldness specifically refers to significant hair loss on the scalp. The most common cause of baldness is hereditary hair loss that occurs with age. Some individuals embrace their hair loss and do not take any action to conceal it. Others may use various methods such as hairstyles, makeup, hats, or scarves to cover it up. Alternatively, some people opt for hair loss treatments to prevent further hair loss or stimulate new hair growth. If you are considering hair loss treatment, you must first consult with your doctor to determine the underlying cause of your hair loss and explore potential treatment options.
Hairy cell leukemia
White blood cells play a crucial role in fighting off germs. However, Hairy Cell Leukemia, a type of cancer, affects a kind of white blood cell known as B cells or B lymphocytes. In this condition, the body produces excessive abnormal B cells, which appear “hairy” under a microscope. These leukemic cells accumulate in the body and cause various symptoms. While the disease usually progresses slowly, a more aggressive variant called the Hairy Cell Leukemia Variant is considered a separate type of cancer. Typically, chemotherapy is the standard treatment for Hairy Cell Leukemia. However, immediate treatment may not be necessary, and the doctor may decide to defer it.
H1N1 flu
H1N1 flu, often known as swine flu, belongs to the influenza A virus category. In the 2009-10 flu season, a novel H1N1 virus emerged, causing human illnesses. Dubbed swine flu, it resulted from a unique blend of influenza viruses affecting pigs, birds, and humans. The World Health Organization (WHO) classified H1N1 flu as a pandemic in 2009, contributing to around 284,400 global fatalities that year. By August 2010, WHO declared the pandemic’s end, though the H1N1 strain remained a part of subsequent seasonal flus. While most recover independently from the flu, its complications can be severe, especially for vulnerable individuals. The seasonal flu vaccine, including protection against H1N1 and other strains, plays a crucial role in preventing illness and its potential consequences.