noun
definition
The outer, protective layer of the skin of vertebrates, covering the dermis
definition
The similar outer layer of cells in invertebrates and plants
Examples of epidermis in a Sentence
This consists typically of close-fitting layers of cells with completely suberized walls, intended to replace the epidermis as the external protective layer of the plant when the latter, incapable as it is of further growth after its original formation, is broken and cast off by the increase in thickness of the stem through the activity of the cambium.
The nerveend-cells, which lie below the lens, are part of the general epidermis.
The epidermis protects the lower layers.
Among the Archiannelida, in Aeolosoma and some Polychaetes, the whole central nervous system remains imbedded in the epidermis.
Many tropical plants present on the upper surface of their leaves several layers of compressed cells beneath the epidermis which serve for storage of water and are known as aqueous tissue.
In Hirudo and the Gnathobdellidae there is only one system of cavities which consist of four principal longitudinal trunks, of which the two lateral are contractile, which communicate with a network ramifying everywhere, even among the cells of the epidermis.
The cells of tl ommatidium are a good deal larger than the neighbouring common cells of the epidermis.
The epidermis consists of pyriform cells, which send richly branched processes to the superficial cuticle.
The epidermis has lost its connected epithelial character and its cilia, and the isolated cells have become sunk inwards retaining their S t- FIG.
It is the first part which is cast off when the snake sheds its skin; this is done several times in the year, and the epidermis comes off in a single piece, being, from the mouth towards the tail, turned inside out during the process.
The cuticle is secreted by an epidermis in which no cell boundaries are to be seen; it sends out processes into the bristles.
Correlated with their life in dry situations, the bulk of the tissue is succulent, forming a water-store, which is protected from loss by evaporation by a thickly cuticularized epidermis covered with a waxy secretion which gives a glaucous appearance to the plant.
It readily dissolves the epidermis of the skin and many other kinds of animal tissue - hence the former application of the "sticks" in surgery.
The organs are developed as invaginations of the epidermis of the foot, and in the majority of the Protobranchia the orifice of invagination remains open throughout life; this is also the case in Mytilus including the common mussel.
In effect (6) it traces the Turbellaria to small two-layered organisms consisting of an outer ciliated epidermis and a central syncytial tissue.
A pair of eyes lie dorsally and behind them is a b closed circlet, often pulled out into various shapes, of modified epidermis, to which an olfactory function has been attributed.
The tegmentum is pierced by numerous vertical ramified canals which contain epithelial papillae of the epidermis.
Plasmopara, &c. In Cystopus (Albugo) the "conidia" are abstricted in basipetal chain-like series from the ends of hyphae which come to the surface in tufts and break through the epidermis as white pustules.
Every leaf originates as a simple cellular papilla (fig 1), which consists of a development from the cortical layers covered by epidermis; and as growth proceeds, the fibro-vascular bundles of the stem are continued outwards, and finally expand and terminate in the leaf.
The typical foliage leaf consists of several layers, and amongst vascular plants is distinguishable into an outer layer (epidermis) and a central tissue (parenchyma) with fibro-vascular bundles distributed through it.
The cells of the epidermis are very closely united laterally and contain no green colouring matter (chlorophyll) except in the pair of cells - guard-cells - which bound the stomata.
The lower epidermis is often of a dull or and pale-green colour.
The upper epidermis is frequently smooth and shining, and sometimes becomes very hard and dense.
In leaves having a very firm texture, as those of Coniferae and Cycadaceae, the cells of the parenchyma immediately beneath the epidermis are very much thickened and elongated in a direction parallel to the surface of the leaf, so as to be fibre-like.
These are collected in water, scraped over the edge of a shell to free them from adhering cellular tissue and epidermis, and more than once washed in a running stream, followed by renewed scraping till the desired purity of fibre is attained.
The structure of the epidermis of the under side of the leaf, with its contorted cells, is represented (X 160) in fig.
The body is composed of a large number of segments; the prostomium bears a pair of tentacles; the nervous system consists of a brain and longitudinal ventral nerve cords closely connected with the epidermis (without distinct ganglia), widely separated in Saccocirrus, closely approximated in Protodrilus, fused together in Polygordius; the coelom is well developed, the septa are distinct, and the dorsal and ventral longitudinal mesenteries are complete; the nephridia are simple, and open into the coelom.
When rubbed into the skin with such substances as alcohol or glycerine, which are absorbed, atropine is carried through the epidermis with them, and in this manner - or when simply applied to a raw surface - it paralyses the terminals of the pain-conducting sensory nerves.
It is based upon the fact that the histological differentiation of the epidermis of their root is that generally characteristic of Monocotyledons, whilst they have two cotyledons - the old view of the epiblast as a second cotyledon in Gramineae being adopted.
A,a,Female Heterodera schachtii Schmidt, breaking through the epidermis of a root; the head is still embedded in the parenchyma of the root.
Soon afterwards there is an accumulation under the epidermis of a serum derived from the dilated blood-vessels.
The seeds when placed in water for some time become coated with glutinous matter from the exudation of the mucilage in the external layer of the epidermis; and by boiling in sixteen parts of water they exude sufficient mucilage to form with the water a thick pasty decoction.
On the skin we have a thick epidermis through which microbes cannot pass, although if an entrance is obtained for them by a prick or cut they may readily grow in the tissues below and spread from them throughout the whole body.
In the same way, washing the skin with spirit would tend to harden the epidermis and thus prevent the entrance of microbes; and the application of an ointment to an abrasion would have a similar action.
The thickening of the epidermis in the hands and feet, which occurs from constant use, is nature's provision for meeting the extra wear to which these parts are subjected by much use; but pressure is apt to cause the defensive process to be carried too far, and to lead to corns, which give rise to much pain and annoyance.
In psoriasis the epidermis separates in flakes at various spots which have not been subjected to pressure, and to cure it ointment containing tar or other products of the dry distillation of wood is employed.
The germinating spores are not only able to pierce the leaves and stems of the potato plant, and so gain an entry to its interior through the epidermis, but they are also able to pierce the skin of the tuber, especially in young examples.
When terminal the awn has three fibro-vascular bundles, when dorsal only one; it is covered with stomate-bearing epidermis.
In the greater number of mammals the skin is more or less densely clothed with a peculiarly modified form of epidermis known as hair.
Other epidermic appendages are the horns of ruminants and rhinoceroses - the former being elongated, tapering, hollow caps of hardened epidermis of fibrous structure, fitting on and growing from conical projections of the frontal bones and always arranged in pairs, while the latter are of similar structure, but without any internal bony support, and situated in the middle line.
Callosities, or bare patches covered with hardened and thickened epidermis, are found on the buttocks of many apes, the breast of camels, the inner side of the limbs of Equidae, the grasping under-surface of the tail of prehensile-tailed monkeys, opossums; &c. The greater part of the skin of the onehorned Asiatic rhinoceros is immensely thickened and stiffened by an increase of the tissue of both the skin and epidermis, constituting the well-known jointed " armour-plated " hide of those animals.
The mature sporangium had a wall of a single layer of cells, which were larger towards the base, where they continued into the epidermis of the sporangiophore.
The pinnae, except in a few filmy forms, are thick; in Kaulfussia large pores derived from stomata occur in the epidermis.
Very usually (but not in the Onychophora = Peripatus) all the parapodia are plated with chitin secreted by the epidermis, and divided into a series of joints - giving the " arthropodous " or hinged character.
Two or three layers of cells inside the epidermis constitute the tissue of the ovary, and overlie somewhat similar layers which form the coats of the seed.
The nervous system lies in the epidermis, externally to the basementmembrane.
The epidermis, placed immediately within the cuticle, is composed of a single row of cells.
Beneath the epidermis is a thin cutis, which is followed by the muscular layers (external circular and internal longitudinal).
In each a differentiation takes place in the layers beneath the epidermis, by which an outer layer of small-celled tissue surrounds an inner portion of large cells.
The cuticularized epidermis, especially, is often thus preserved, and may be removed by the use of appropriate reagents and examined microscopically.