elundiliigid

Elundiliigid, Estonian for “organs,” refer to specialized structures within organisms that perform distinct physiological functions. In biological contexts, an organ is defined as a group of tissues that work together to carry out a specific activity essential for the organism’s survival, growth, or reproduction. Each organ consists of one or more tissue types—epithelial, connective, muscle, or nervous tissue—that collaborate to achieve the organ’s purpose.

Organs are often classified by the systems to which they belong and by the nature of the function they execute. The main categories include:

Digestive organs such as the stomach, small intestine, and liver process and absorb nutrients.

Respiratory organs such as the lungs and trachea enable gas exchange.

Excretory organs like the kidneys and liver filter waste products and regulate body fluids.

Reproductive organs—ovaries, testes, uterus, and seminal vesicles—facilitate sexual reproduction and hormone production.

Endocrine organs such as the pancreas and thyroid release hormones that coordinate metabolic activities.

Nervous organs, including the brain, spinal cord, and peripheral nerves, process sensory information and orchestrate bodily responses.

Some organs are composed as functional units of a single tissue type, for example, the lens of the eye, while others, like the heart, integrate muscular, connective, and nervous tissues. The evolution of defined organs has allowed multicellular organisms to divide labor among specialized structures, leading to increased complexity and adaptability across life forms.