Haematopoietic

A type of stem cell found in the bone marrow, which can differentiate into blood cells, such as red blood cells, white blood cells, and platelets.

Haemoglobin

The part of the red blood cells that carries oxygen.

Haemophilia

An inherited disease where blood fails to clot.

Halitosis

Bad breath. Caused by certain bacteria in the mouth breaking down proteins into smelly byproducts.

Heart disease

A condition that affects the heart muscle or the blood vessels of the heart.

Herbalist

A person who uses plants or plant extracts to heal.

Herbivore

An animal that eats only plants.

Heritability

A measure of the degree to which variation in the characteristics of a phenotype is due to genetic causes.

Heterozygous

When the two alleles for a particular gene are different.

Holistic

Looking at the entire system. In healthcare, this means looking at all aspects of a patient’s well-being and not just treating a particular pain or disease.

Homogenise

Reduce the size of fat globules in order to distribute them equally throughout a liquid.

Homogeniser

A machine that reduces a substance to small particles and disperses them evenly throughout a liquid.

Homozygous

When the two alleles for a particular gene are the same.

Horizontal gene transfer

The transfer of genetic information between organisms of different species.

Hormone

A chemical messenger produced naturally by cells, which can cause widespread changes in the rest of the body.

Host

An organism that contains a parasite or other dependent organism. Hosts usually provide parasites with food and shelter.

Hui

A gathering, meeting, assembly, seminar or conference.

Human immunodeficiency virus (HIV)

The virus that causes acquired immune deficiency syndrome (AIDS).

Human leukocyte antigens (HLA)

A class of proteins found on the surface of cells in the immune system, which help the immune system to distinguish ‘self’ from ‘non-self’.

Humidifier

A machine that adds moisture to the air.

Huntington's disease

A genetic disorder of the nervous system, characterised by involuntary movements and progressive mental deterioration.

Husbandry

The breeding and raising of animals, or the cultivation of crops.

Hybrid

The progeny of cross-breeding 2 pure-breeding lines.

Hydrogen bond

A weak attraction which holds two molecules containing hydrogen together. For example, in water two hydrogen atoms are bonded to one oxygen atom.

Hydrogen peroxide

A substance made up of hydrogen and oxygen. It is produced by cells, but can be toxic in large amounts and is broken down rapidly by enzymes.

Hydrophilic

Hydrophilic substances have an affinity for water and readily absorb or dissolve in water (hydro = water, philic = fond).

Hydrophobic

Hydrophobic means ‘water fearing’. Hydrophobic substances do not dissolve easily in water and are usually non-polar (hydro = water, phobia = fear).

Hyperuricaemia

High levels of uric acid in the blood.

Hypothalamus

A region of the brain that regulates body functions, including temperature, appetite and sleep.

Hypothesis

A tentative explanation for a fact or observation that can be tested.

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