Atlas of plant and animal histology

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Glossary: I


Idioblast: (in plants) it is a type of cell that can store and release substances, such as aqueous substances, storage material, minerals and pigments.

♣ Plant tissues: Glandular tissue.

Incus: it is a bone found in the tympanic cavity. The incus, together with the malleus and the stapes, form part of the inner ear. The incus is located between the malleus and the stapes and transmit vibrations from the malleus to the stapes.

♣ Animal organs: Senses.

Indehiscent: (in plants) it is a type of fruit that does not open during maturation and the see remains in the interior. For instance, chesnut and grenade.

♣ Plant organs: Fruit .

Indol aceti acid: see auxin.

Inferor ovary: (in plant flowers) it is the ovary located below the receptacle (structure where stamens, sepals and petals are inserted).

♣ Plant organs: Flower .

Inflorescence: (in plants) it is the aerial part of the body plant where flowers are formed. The term inflorescence is usually for naming a cluster or bunch of flowers grouped in one stem.

♣ Plant organs: Flower.

Initial fusiform cell: (in plants) it is a type of cell found in the vascular cambium. Fusiform cells are vertically oriented (parallel to the mayor axis of the organ) and differentiate into the vertical elements of xylem and phloem.

♣ Plant tissues: Vascular cambium.
♣ Plant organs: Secondary root.

Inner ear: it is the deeper part of the ear, also known as labyrinth. There is a bone labyrinth and a membranous labyrinth. Bone labyrinth is found in the temporal bone of the skull and consists of three semicircular canals, vestibule and cochlea. The vestibule is placed in the middle.

♣ Animal organs: Senses .

Integument: it is an animal organ consisting in epidermis, dermis, hypodermis and associated appendages like nails, feathers, hair, scales and horns. The integument is the main protection barrier of the body from the environment. It is also an important temperature regulator in animals.

♣ Cell types: Keratinocyte.

Intercalary Meristem: (in plants) it is a type or meristem responsible for the growth in length of plants showing primary grow. Intercalary meristem is found among the parenchyma tissue, mainly in the internode region of stems and in the sheath of monoc plants.

♣ Plant organs: Stem.

Intercalated disc: (in cardiac muscle) it is a dense long structure visualized in the cardiac muscle cells or cardiomyocytes. They are visible after common histological staining and are a set of cell junctions, such as desmosomes and adherent junctions. The function of intercalated discs is to keep attached neighbor muscle cells during heart wall movements. Some gap junctions can also be found in the intercalated discs for direct cytoplasm-cytoplasm communication and synchronization of cardiomyocytes.

♣ Animal tissues: Heart muscle cells .

Intenode: (in plants) it is the segment of the stem between two adjoining nodes.

♣ Plant organs: Introduction, Stem .

Intine: (in plants) it is the inner layer of the coat of the pollen grain. Intine is in contact with the plasma membrane of cells. The outer layer is referred as exine.

♣ Plant organs: Seed.

Interfascicular cambium: (in plants) it is a meristem that differentiates from the parenchyma region found between two neighbor vascular bundles. Interfascicular cambium and fascicular cambium join to form the vascular cambium, responsible for the secondary grow.

Interfascicular parenchyma: (in plants) it is parenchyma cells found between adjoining vascular bundles in the stem during primary growth of dicot plants. If there is secondary growth, the interfascicular parenchyma is differentiated into interfascicular meristem and later becomes part of the vascular cambium.

♣ Plant tissues: Meristems, Vascular cambium .

Intraepithelial gland: it is a type of secretory cells scattered or associated in small groups among the epithelial cells. Intraepithelial glands release their content directly to the surface of the epithelium, so there is no excretory duct. They usually release mucous substances. For instance, caliciform cells of the respiratory tract.

Intralobular duct: (in the pancreas) it is a type of duct found in the exocrine part of the pancreas. Intralobular duct is one of the pancreas ducts carrying pancreatic secretion. The sequence of duct types connecting pancreatic acini with the small intestine is intraccinar ducts, intercalate ducts, intralobular ducts, interlobular ducts and main pancreatic duct.

♣ Animal tissues: Pancreas.

Iris: it is the eye structure separating the anterior chamber from the posterior one. The pupil is found in the center of the iris. The is mostly constituted by highly vascularized connective tissue. The posterior, or inner, part of the iris is a double layer epithelium with many pigments, which gives color to eyes. The iris functions as a kind of diaphragm that is adjusted by two muscles.

♣ Animal organs: Senses Iris Iris Iris.

Irregular dense connective tissue: it is a type of dense connective tissue with abundant collagen fibers oriented in all directions. Therefore, irregular dense connective tissue is able to withstand mechanical forces coming from every direction. For instance, it can be found in the dermis, in the capsule of some organs, and in the sheath of some nerves.

Isogenous group: it is a group of chondrocytes surrounded by extracellular matrix in the cartilage. Isogenous groups are found in the cartilage lacunae.

♣ Animal tissues: Cartílago hialino .
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