Atlas of plant and animal histology

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Glossary: F


F cell: it is a type of cell found in the Langerhans islets of the pancreas. F cells release the pancreatic peptide, which is influences the digestive system physiology.

♣ Animal tissues: Pancreas.

Facial nerve: (nerve VII) it is a peripheral nerve that gather information from the anterior and medial part of taste buds of the tongue, as well as from other sensory structures.

♣ Animal organs: Senses .

Fasciculated root: (in plants) it is a radicular system of some plant species where all the roots emerge from the stem, and not from another root.

♣ Plant organs: Root.

Fenestrated endothelium: it is a type of endothelium with endothelial cells showing large passages or canals in their cytoplasm that directly connect the blood with the surrounding tissues. Fenestrated endothelium is found in endocrine glands and digestive tract, where an intense exchange of molecules across the endothelial layer is needed. Fenestrations of endothelial cells favor this exchange.

♣ Animal organs: Cardiovascular .

Fibroblast: it is a type of cell typically found in the connective proper tissue. Fibroblasts release most of both ground substance and fibrillar components of the extracellular matrix of connective proper tissues. Fibroblasts show irregular shapes, can move and do not form layers or sheets.

♣ Cell types: Fibroblast .

Fibrocartilage: it is a type of cartilage with blended features of hyaline cartilage and dense regular connective proper tissues. Fibrocartilage is scarce in the animal body. It can be found in the intervertebral discs, some joints, the insertion point of tendons to the epiphysis bone region, in some parts of the heart valves, and in the penis of some animals.

♣ Animal tissues: Cartilage.

Filament: (in plants), it is the part of the stamen connecting the anthers with the flower receptacle.

♣ Planto organs: Flower, Flower: parts , Stamen.

Filiforme papila : (in the tongue) it is a type of papilla found in the dorsolateral part of the tongue. Filiform papillae are sharp-tip and keratinized papillae. They do not have taste buds and their function is not for sensing taste but to form a rough surface to move the food. Filiform are the most abundant papillae in the tongue.

♣ Animal organs: Tongue , Senses.

Flagellum: it is a cell structure found at the cell surface that produces cell movement. Flagella contain a microtubule scaffold known as axoneme made up of microtubules: 9 peripheral pairs and 1 central pair. The axoneme proximal end is continuous with the basal body, a structure similar to centrioles. Flagella and cilia microtubular organization is similar, but flagella are longer. Flagella can be found in free eukaryote cells, such as gametes or unicellular organisms, but they are less often observed in cells forming part of the multicellular organism.

Fleshy fruit: (in plants) it is a type of fruit with thehighly hydrated mesocarp and succulent parenchyma. There are four main types of fleshy fruits. 1. Berry, such as grape and tomato, which shows a cunitinized exocarp. 2. Drupe, such as peach, with a very hard bone-like endocarp that becomes the hard coat surronding the seed. 3. Pome, such as apple, where the endocarp shows a gelatinous consistence. 4. Hesperidium, like citrus fruits, which have a collenchymatic exocarp with glands, and a very thin mesocarp, while the endocarp is made up of juice sacs and form most of the fruit.

♣ Plant organs: Fruit .

Flower: (in plants) it is the reproductive organ in most plants. The flower is where gametes, seed and fruit are produced, where fertilization takes place, and favors fertilization by attracting polynizing animals. A typical flower is composed of pistil, stamens, petals and sepals.

Flowering: it is the development of the flower bud into a flower.

♣ Plant organs: Flower.

Foliate papilla: (in the tongue) it is a type of papilla found in the dorso-lateral part of the tongue. Foliate papillae are delimited by parallel grooves and show taste buds in the lateral walls. These papillae are not well-developed in humans, unlike other species like rabbits where foliate papillae are numerous and with many taste buds.

♣ Animal organs: Tongue , Senses.

Focal adhesion: it is a cell junction made up of integrins connected to actin filaments. Focal adhesions establish adhesion points between the cell and the extracellular matrix.

♣ Animal tissues: Epithelium.

Follicle: it is a cellular bag-like structure, that may be open or closed. Follicle examples are thyroid follicles, ovarian follicles and hair follicles.

♣ Animal organs: Ovarian follicles , Thin skin .

Follicular cell: (in the thyroid) it is a type of cell found in the thyroid follicles. Follicular cells are organized in a monolayer that forms the wall of thyroid follicles. They release to the interior of the follicle molecules that form the colloid, mainly thyroglobulin. T3 y T4 thyroid hormones are formed from thyroglobulin.

♣ Animal tissues: Thyroid .

Fovea: it is the region of the retina where the light is focused by eye lenses, and therefore is where the images are sharply formed. Moving the eye to see an object is moving the fovea to get focused that object we are interested in. Fovea contains a higher density of cones light receptors that any other part of the retina.

♣ Animal organs: Senses.

Free nerve ending: it is a neuronal process that runs through the dermis and sometimes enter the epidermis. Free nerve endings are not wrapped by myelin (that why the term "free"). They are sensory processes that sense temperature, mechanical stimuli and pain. Some of them may be associated with Merkel cells of the epidermis and others with the hair follicles.

♣ Animal organs: Senses.

Fruit: (in plants) it can be regarded as the organ containing the seed. The fruit does not only protect the seed but also helps during seed dispersion, either in a passive or active way. The fruit is mostly formed from the ovary and consists in three layers: exocarp, mesocarp and endocarp, and altogether form the pericarp, which can be fleshy or hard dry.

♣ Plant tissues: Introduction, Glandular.

Fungiform papilla: (in the tongue) it is a type of papilla found in the dorso-lateral part of the tongue with a shape similar to a fungus. Fungiform papillae contain have taste buds in their upper part.

♣ Animal organs: Tongue , Senses.

Funiculus: (in plants) it is a cellular stalk connecting the ovule with the ovary wall.

♣ Plant organs: Seed, Flower .
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