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Between the two layers is a thin fluid filled space. [4] The fluid is produced by the serous membranes and stays between the two layers to reduce friction between the walls of the cavities and the internal organs when they move with respect to one another, such as when the lungs inflate or the heart beats.
Synovial fluid is an ultrafiltrate from blood, and contains proteins derived from the blood plasma and proteins that are produced by cells within the joint tissues. [4] The fluid contains hyaluronan secreted by fibroblast-like cells in the synovial membrane, lubricin (proteoglycan 4; PRG4 ) secreted by the surface chondrocytes of the articular ...
Fluid friction describes the friction between layers of a viscous fluid that are moving relative to each other. [7] [8] Lubricated friction is a case of fluid friction where a lubricant fluid separates two solid surfaces. [9] [10] [11] Skin friction is a component of drag, the force resisting the motion of a fluid across the surface of a body.
A wheeled buffalo figurine—probably a children's toy—from Magna Graecia in archaic Greece [1]. Several organisms are capable of rolling locomotion. However, true wheels and propellers—despite their utility in human vehicles—do not play a significant role in the movement of living things (with the exception of the corkscrew-like flagella of many prokaryotes).
This glossary of biology terms is a list of definitions of fundamental terms and concepts used in biology, the study of life and of living organisms.It is intended as introductory material for novices; for more specific and technical definitions from sub-disciplines and related fields, see Glossary of cell biology, Glossary of genetics, Glossary of evolutionary biology, Glossary of ecology ...
Bacterial populations interact in a similar manner to cells in tissue. They communicate through physical interactions and signaling molecules such as homoserine lactones and peptides as a means to control metabolism and regulate growth . A common example and one of the most studied forms of bacterial cell interactions is biofilm.
Signaling theory, in evolutionary biology, proposes that a substantial driver for evolution is the ability of animals to communicate with each other by developing ways of signaling. In human engineering, signals are typically provided by a sensor , and often the original form of a signal is converted to another form of energy using a transducer .
The cilium (pl.: cilia; from Latin cilium ' eyelid '; in Medieval Latin and in anatomy, cilium) is a short hair-like membrane protrusion from many types of eukaryotic cell. [1] [2] (Cilia are absent in bacteria and archaea.)