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In radial section, two tracheids of a coniferous wood species are shown. A series of bordered pits are also appearing in each tracheid. A tracheid of oak shows pits along the walls. It has no perforation plates. Angiosperms have both tracheids and vessel elements. [1] A tracheid is a long and tapered lignified cell in the xylem of vascular ...
In vertebrates, the circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the body. [ 1 ] [ 2 ] It includes the cardiovascular system , or vascular system , that consists of the heart and blood vessels (from Greek kardia meaning heart , and Latin vascula meaning vessels ).
Xylem cells are dead, hard-walled hollow cells arranged to form files of tubes that function in water transport. A tracheid cell wall usually contains the polymer lignin. [citation needed] The phloem, on the other hand, consists of living cells called sieve-tube members. Between the sieve-tube members are sieve plates, which have pores to allow ...
The xylem, vessels and tracheids of the roots, stems and leaves are interconnected to form a continuous system of water-conducting channels reaching all parts of the plants. The system transports water and soluble mineral nutrients from the roots throughout the plant. It is also used to replace water lost during transpiration and photosynthesis.
All the vascular tissues within a particular plant together constitute the vascular tissue system of that plant. The cells in vascular tissue are typically long and slender. Since the xylem and phloem function in the conduction of water, minerals, and nutrients throughout the plant, it is not surprising that their form should be similar to pipes.
Arthropods and most mollusks have an open circulatory system. In this system, deoxygenated blood collects around the heart in cavities . This blood slowly permeates the heart through many small one-way channels. The heart then pumps the blood into the hemocoel, a cavity between the organs. The heart in arthropods is typically a muscular tube ...
The circulatory system is controlled by homeostatic mechanisms of autoregulation, just as hydraulic circuits are controlled by control systems. The hemodynamic response continuously monitors and adjusts to conditions in the body and its environment. Hemodynamics explains the physical laws that govern the flow of blood in the blood vessels.
Cardiovascular physiology is the study of the cardiovascular system, specifically addressing the physiology of the heart ("cardio") and blood vessels ("vascular").. These subjects are sometimes addressed separately, under the names cardiac physiology and circulatory physiology.