Biology Prefixes and Suffixes: meso-

Mesothelium is simple squamous epithelium derived from the middle embryonic germ layer known as the mesoderm. It is sometimes called pavement epithelium as the cells are analogous to flat tiles on a floor. Credit: Ed Reschke/Photolibrary/Getty Images

The prefix (meso-) comes from the Greek mesos or middle. (Meso-) means middle, between,  intermediate, or moderate. In biology, it commonly used to indicate a middle tissue layer or body segment.

Words Beginning With: (meso-)

Mesoblast (meso-blast): The mesoblast is the middle germ layer of an early embryo. It contains cells that will develop into the mesoderm.

Mesocardium (meso-cardium): This double layer membrane supports the embryonic heart. Mesocardium is a temporary structure that attaches the heart to the body wall and foregut.

Mesocarp (meso-carp): The wall of fleshy fruit is known as pericarp and contains three layers. Mesocarp is the middle layer of the wall of ripened fruit. Endocarp is the inner most layer and exocarp is the outer most layer.

Mesocephalic (meso-cephalic): This term refers to having a head size of medium proportions. Organisms with a mesocephalic head size range between 75 and 80 on the cephalic index.

Mesocolon (meso-colon): The mesocolon is part of the membrane called the mesentery or middle bowel, that connects the colon to the abdominal wall.

Mesoderm (meso-derm): Mesoderm is the middle germ layer of a developing embryo that forms connective tissues such as muscle, bone, and blood. It also forms urinary and genital organs including the kidneys and gonads.

Mesofauna (meso-fauna): Mesofauna are small invertebrates that are intermediate-sized microbes. This includes mites, nematodes, and springtails ranging in size from 0.1 mm to 2 mm.

Mesogastrium (meso-gastrium): The middle region of the abdomen is called the mesogastrium. This term also refers to the membrane that supports the embryonic stomach.

Mesoglea (meso-glea): Mesoglea is the layer of gelatinous material located between outer and inner cell layers in some invertebrates including jellyfish, hydra, and sponges. This layer is also called mesohyl.

Mesohyloma (meso-hyl-oma): Also known as mesothelioma, mesohyloma is an aggressive type of cancer originating from epithelium derived from the mesoderm. This form of cancer occurs commonly in the lining of the lungs and is associated with asbestos exposure.

Mesolithic (meso-lithic): This term refers to the middle stone age period between the Paleolithic and Neolithic eras. The use of stone tools called microliths became prevalent among ancient cultures in the Mesolithic age.

Mesomere (meso-mere): A mesomere is a blastomere (cell resulting from the cell division or cleavage process that occurs following fertilization) of medium size.

Mesomorph (meso-morph): This term describes an individual with a muscular body build predominated by tissue derived from the mesoderm. These individuals gain muscle mass relatively quickly and have minimal body fat.

Mesonephros (meso-nephros): The mesonephros is the middle portion of the embryoinc kidney in vertebrates. It develops into adult kidneys in fish and amphibians, but is transformed into reproductive structures in higher vertebrates.

Mesophyll (meso-phyll): Mesophyll is the photosynthetic tissue of a leaf, located between the upper and lower plant epidermis. Chloroplasts are located in the plant mesophyll layer.

Mesophyte (meso-phyte): Mesophytes are plants living in habitats that provide a moderate supply of water. They are found in open fields, meadows, and shady areas that are not too dry or too wet.

Mesopic (mes-opic): This term refers to having vision in moderate levels of light. Both rods and cones are active at the mesopic range of vision.

Mesorrhine (meso-rrhine): A nose that is of moderate width is considered to be mesorrhine.

Mesosome (meso-some): The anterior portion of the abdomen in arachnids, located between the cephalothorax and lower abdomen, is called the mesosome.

Mesosphere (meso-sphere): The mesosphere is Earth's atmospheric layer located between the stratosphere and thermosphere.

Mesosternum (meso-sternum): The middle region of the sternum, or breastbone is called the mesosternum. The sternum connects the ribs forming the rib cage, which protects the organs of the chest.

Mesothelium (meso-thelium): Mesothelium is epithelium (skin) that is derived from the mesoderm embryonic layer. It forms simple squamous epithelium.

Mesothorax (meso-thorax): The middle segment of an insect located between the prothorax and metathorax is the mesothorax.

Mesotrophic (meso-trophic): This term refers commonly to a body of water with moderated levels of nutrients and plants. This intermediate stage is between the oligotrophic and eutrophic stages.

Mesozoa (meso-zoa): These free-living, worm-like parasites inhabit marine invertebrates such as flatworms, squid, and star fish. The name mesozoa means middle (meso) animal (zoon), as these creatures were once thought to be intermediates between protists and animals.