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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.
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.
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.
Filament: (in plants), it is the part of the stamen connecting the anthers with the flower receptacle.
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.
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.
Follicle: it is a cellular bag-like structure, that may be open or closed. Follicle examples are thyroid follicles, ovarian follicles and hair follicles.
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.
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.
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.