Pseudohemal System

Pseudohemal System

 

(also perihemal, or sinus, system), in echinoderms, a series of canals surrounding the blood vessels that develops from isolated portions of the secondary body cavity, or coelom. The pseudohemal system includes an annular circumoral canal, which is situated between the ambulacral and nerve rings. There also are axial canals, annular aboral canals, and five radial canals—all of which extend into the ambulacra and run between the radial nerves and ambulacral canals. The fluid of the pseudohemal system, which is similar in composition to that of the body cavity, contains amoebocytes and apparently serves to nourish the nerve cords and prevent them from being compressed. The pseudohemal system is not equally developed in all echinoderms; for example, crinoids have only radial canals. The axial canal in some echinoderms is capable of contracting rhythmically.

References in classic literature ?
There is only room for me to send my love, and some pressed pansies from the root I have been keeping safe in the house for Father to see.
The older man seemed prepared to keep the exercise going indefinitely but George Willard's head struck the root of a tree and he lay still.
It was like any other cavern of the mountains, though wonderful for the number of crystal formations on the root and walls--formations that sparkled like a million diamonds in the flickering lights.
It was full of little brown chips that looked like the shavings of some root.
Whatever may be the truth, as respects the root and the genius of the Indian tongues, it is quite certain they are now so distinct in their words as to possess most of the disadvantages of strange languages; hence much of the embarrassment that has arisen in learning their histories, and most of the uncertainty which exists in their traditions.
The urbane activity with which a man receives money is really marvellous, considering that we so earnestly believe money to be the root of all earthly ills, and that on no account can a monied man enter heaven.
The compact round body of its root expands into two broad, firm, flat palms or flukes, gradually shoaling away to less than an inch in thickness.
He had wasted his life, he had wrecked himself, with his accursed weakness; and now he was done with it--he would tear it out of him, root and branch
How much more fertile a Nature, at least, has Grecian mythology its root in than English literature
Martyrdom made a saint of the trivial and foolish Marie Antoinette, and her biographers still keep her fragrant with the odor of sanctity to this day, while unconsciously proving upon almost every page they write that the only calamitous instinct which her husband lacked, she supplied--the instinct to root out and get rid of an honest, able, and loyal official, wherever she found him.
When we was passing by the kitchen I fell over a root and made a noise.
The fact was that the ivory hook of the parasol had caught in the chain gear, and when the first attempt at drawing water was made, the little offering of a contrite heart was jerked up, bent, its strong ribs jammed into the well side, and entangled with a twig root.