Microscopic mass of protoplasm enveloped by a semi‐permeable membrane. Smallest structural unit of living matter able to function independently.
The cavity or cavities of an ovary or fruit containing the ovules or seeds;
The pollen-sac of an anther, an anther lobe or theca;
The fundamental, minute unit of all plant construction.
The individual unit that makes up all of the tissues of the body. All living things are made up of one or more cells.
The fundamental self-containing unit of life. The living tissue of every multicelled organism is composed of these fundamental living units. Certain organisms may consist of only one cell, such as yeast or bacteria, protozoa, some algae, and gametes (the reproductive stages) of higher organisms. Larger organisms are subdivided into organs that are relatively autonomous but cooperate in the functioning of that plant or animal. Unicellular (i.e., single-cell) organisms perform all life functions within the one cell. In a higher organism (i.e., a multicellular organism), entire populations of cells (i.e., an organ) may be designated a particular specialized task (e.g., the heart to facilitate circulation). The cells of muscle tissue are specialized for movement and those of bone and connective tissue, for structural support.
A small compartment or cavity, as in a honeycomb.
A small microscopic mass of protoplasm capable alone, or interacting with others, of performing all fundamental life functions; the smallest structural entity capable of functioning independently.
A cavity more enclosed than a pit.
A chamber or compartment (as in a seed).
Cavities in an anther, containing the pollen. The microscopic units of which all plants (and animals) are built up.
The structural unit composing the bodies of plants and animals.
A tiny unit of matter which is the base of all plant and animal tissue.
The smallest structural unit of living material.
Individual living unit, the basic structure for tissues and organs, made up of an outer membrane, the main mass (cytoplasm), and the nucleus, which controls the cell’s metabolism and reproduction; a single living part (e.g., a red blood cell) or organism (e.g., a protozoan).
The fundamental structural unit of all body tissue and all living things. The human body is composed of billions of cells, specialized to carry out specific roles in the vast system of processes that keep the body functioning.
The basic unit of all living organisms, which can reproduce itself exactly. Each cell is bounded by a cell membrane of lipids and protein, which controls the passage of substances into and out of the cell. Cells contain a jellylike cytoplasm, in which are suspended a nucleus and other structures (organelles) specialized to carry out particular activities in the cell.
A small plant or animal structure which forms the building block (the structural unit) of a tissue. A cell contains two components known as nuclear material and cytoplasmic material, and is enclosed by a membrane. In the human body, all cells fall into one of five general types according to the tissues which they form: epithelial (surface and lining tissues), connective and supporting (bones and cartilages), muscle, nerve, and blood and lymph.
The smallest functional units of the body, known as cells, come together to form tissues and collectively contribute to the performance of specific bodily functions.