Biology

Neurotransmitter Definition Neurotransmitter is a chemical substance that is produced and secreted by a neuron and then diffuses across a synapse to cause excitation or…

Histamine Definition Histamine is an organic compound found widely in animals and plants that in humans and other mammals is released as part of the…

Gastric Glands Definition Gastric gland is the basic secretory unit of the stomach and contains a variety of component cells located in characteristic locations. It…

Salivary Gland Definition Salivary gland is a gland in terrestrial animals that secretes saliva. In humans, three pairs of large glands, which include the parotid…

Gallbladder Definition Gallbladder is a small, pear-shaped muscular sac in most vertebrates in which bile is stored. The gallbladder is located beneath the liver and…

Basement Membrane Definition Basement membrane is a thin, delicate layer of connective tissue underlying the epithelium of many organs. It is also called basilemma. Basement…

Lymphatic Vessel Definition Lymphatic vessels are any of the vascular channels that transport lymph throughout the lymphatic system and freely anastomose with one another. It…

Lymph Node Definition Lymph nodes (or Lymph gland) are small lumps of tissue that contain white blood cells, which fight infection. They filter lymph fluid,…

Mediastinum Definition Mediastinum is the area in the chest between the lungs that contains the heart, part of the windpipe (the trachea), the esophagus, and…

Thymus Gland Definition Thymus gland is an organ of the lymphatic system located behind the upper sternum (breastbone). T cells (T lymphocytes) develop and mature…

Nasal Concha Definition Nasal concha also called Turbinate, or Turbinal, any of several thin, scroll-shaped bony elements forming the upper chambers of the nasal cavities.…

Ethmoid Bone Definition Ethmoid bone is exceedingly light and spongy bone that provides the floor of the front part of the skull and the roof…