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Spongy tissue is a type of tissue found both in plants and animals. In plants, it is part of the mesophyll , where it forms a layer next to the palisade cells in the leaf . The spongy mesophyll's function is to allow for the interchange of gases (CO 2 ) that are needed for photosynthesis .
Parenchyma cells have a variety of functions: In leaves, they form two layers of mesophyll cells immediately beneath the epidermis of the leaf, that are responsible for photosynthesis and the exchange of gases. [2] These layers are called the palisade parenchyma and spongy mesophyll. Palisade parenchyma cells can be either cuboidal or elongated.
In most leaves, the primary photosynthetic tissue is the palisade mesophyll and is located on the upper side of the blade or lamina of the leaf, [1] but in some species, including the mature foliage of Eucalyptus, [5] palisade mesophyll is present on both sides and the leaves are said to be isobilateral.
The mesohyl resembles a type of connective tissue and contains several amoeboid cells such as amebocytes, as well as fibrils and skeletal elements. For a long time, it has been largely accepted that sponges lack true tissue , but it is currently debated as to whether mesohyl and pinacoderm layers are tissues.
In zoology, a skeleton is any fairly rigid structure of an animal, irrespective of whether it has joints and irrespective of whether it is biomineralized. The mesohyl functions as an endoskeleton in most sponges, and is the only skeleton in soft sponges that encrust hard surfaces such as rocks.
Parenchyma is the tissue made up of cells and intercellular spaces that fills the interior of the body of a flatworm, which is an acoelomate. This is a spongy tissue also known as a mesenchymal tissue , in which several types of cells are lodged in their extracellular matrices .
Palisade cells are located beneath the upper epidermis and cuticle but above the spongy mesophyll cells. Palisade cells contain a high concentration of chloroplasts , particularly in the upper portion of the cell, making them the primary site of photosynthesis in the leaves of plants that contain them.
Dendroclones might be unique to extinct sponges [32] and are branching spicules that may take irregular forms, or may form structures with an I, Y or X shape. [33] [34] Megascleres are large spicules measuring from 60-2000 μm and often function as the main support elements in the skeleton. [35] Acanthostyles are spiny styles.