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The circulatory system includes the heart, blood vessels, and blood. The cardiovascular system in all vertebrates, consists of the heart and blood vessels. The circulatory system is further divided into two major circuits – a pulmonary circulation, and a systemic circulation.
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circulatory system, system that transports nutrients, respiratory gases, and metabolic products throughout a living organism, permitting integration among the various tissues. The process of circulation includes the intake of metabolic materials, the conveyance of these materials throughout the organism, and the return of harmful by-products to the environment.
Invertebrate animals have a great variety of liquids, cells, and modes of circulation, though many invertebrates have what is called an open system, in which fluid passes more or less freely throughout the tissues or defined areas of tissue. All vertebrates, however, have a closed system—that is, their circulatory system transmits fluid through an intricate network of vessels. This system contains two fluids, blood and lymph, and functions by means of two interacting modes of circulation, the cardiovascular system and the lymphatic system; both the fluid components and the vessels through which they flow reach their greatest elaboration and specialization in the mammalian systems and, particularly, in the human body.
A full treatment of human blood and its various components can be found in the article human blood. A discussion of how the systems of circulation, respiration, and metabolism work together within an animal organism is found in the article respiration.
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All living organisms take in molecules from their environments, use them to support the metabolism of their own substance, and release by-products back into the environment. The internal environment differs more or less greatly from the external environment, depending on the species. It is normally maintained at constant conditions by the organism so that it is subject to relatively minor fluctuations. In individual cells, either as independent organisms or as parts of the tissues of multicellular animals, molecules are taken in either by their direct diffusion through the cell wall or by the formation by the surface membrane of vacuoles that carry some of the environmental fluid containing dissolved molecules. Within the cell, cyclosis (streaming of the fluid cytoplasm) distributes the metabolic products.
Molecules are normally conveyed between cells and throughout the body of multicellular organisms in a circulatory fluid, called blood, through special channels, called blood vessels, by some form of pump, which, if restricted in position, is usually called a heart. In vertebrates blood and lymph (the circulating fluids) have an essential role in maintaining homeostasis (the constancy of the internal environment) by distributing substances to parts of the body when required and by removing others from areas in which their accumulation would be harmful.
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One phylum, Cnidaria (Coelenterata)—which includes sea anemones, jellyfish, and corals—has a diploblastic level of organization (i.e., its members have two layers of cells). The outer layer, called the ectoderm, and the inner layer, called the endoderm, are separated by an amorphous, acellular layer called the mesoglea; for these animals, bathing both cellular surfaces with environmental fluid is sufficient to supply their metabolic needs. All other major eumetazoan phyla (i.e., those with defined tissues and organs) are triploblastic (i.e., their members have three layers of cells), with the third cellular layer, called the mesoderm, developing between the endoderm and ectoderm. At its simplest, the mesoderm provides a network of packing cells around the animal’s organs; this is probably best exhibited in the phylum Platyhelminthes (flatworms).
Nematoda, Rotifera, and a number of other smaller eumetazoan classes and phyla have a fluid-filled cavity, called the pseudocoelom, that arises from an embryonic cavity and contains the internal organs free within it. All other eumetazoans have a body cavity, the coelom, which originates as a cavity in the embryonic mesoderm. Mesoderm lines the coelom and forms the peritoneum, which also surrounds and supports the internal organs. While this increase in complexity allows for increase in animal size, it has certain problems. As the distances from metabolizing cells to the source of metabolites (molecules to be metabolized) increases, a means of distribution around the body is necessary for all but the smallest coelomates.
Learn about the circulatory system of animals, including blood, lymph, and vessels. Explore the differences between invertebrates and vertebrates, and the human circulatory system in detail.
The circulatory system (also called the cardiovascular system) is the body system that moves blood around the body. It consists of the heart and blood vessels. The blood carries various materials that the body needs, and takes away waste and harmful substances.
Sep 12, 2023 · Learn about the circulatory system, also called cardiovascular system, a vital organ system that delivers essential substances to all cells. Explore the structure, function, parts, and diseases of the heart, blood vessels, and blood.
The heart functions as a pump in the circulatory system to provide a continuous flow of blood throughout the body. This circulation consists of the systemic circulation to and from the body and the pulmonary circulation to and from the lungs.
Apr 15, 2023 · 4 The Circulatory System. 4.1 Arteries. 4.1.1 Arterioles. 4.2 Capillaries. 4.3 Veins. 4.4 Venules. 5 The Cardiovascular Pathways. 5.1 The Pulmonary Circuit. 5.2 The Systemic Circuit. 5.3 Aorta. 5.4 Superior Venae Cavae. 5.5 Inferior Venae Cavae. 5.6 Coronary Arteries. 5.7 Hepatic Veins. 6 Cardiac Cycle. 6.1 Systole. 6.2 Diastole.
Sep 21, 2021 · Learn about the circulatory system, also known as the cardiovascular system, and how it pumps blood to the body. Find out about the parts, circuits, organs and conditions that affect the circulatory system.
