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Aerenchyma in stem cross section of a typical wetland plant. Aerenchyma or aeriferous parenchyma [1] or lacunae, is a modification of the parenchyma to form a spongy tissue that creates spaces or air channels in the leaves, stems and roots of some plants, which allows exchange of gases between the shoot and the root. [2]
In an ordinary microscopic section, viewed by transmitted light, they appear as fusiform opaque spots. Each lacuna is occupied during life by a branched cell, termed an osteocyte, bone-cell or bone-corpuscle. Lacunae are connected to one another by small canals called canaliculi. A lacuna never contains more than one osteocyte.
Brain cells make up the functional tissue of the brain. The rest of the brain tissue is the structural stroma that includes connective tissue such as the meninges , blood vessels , and ducts. The two main types of cells in the brain are neurons , also known as nerve cells, and glial cells , also known as neuroglia. [ 1 ]
Moreover, focal narrowing of brain vessels and impairment of their ability to dilate in response to various stimuli may lead to a decreased cerebral blood flow and ultimately lacunar stroke. [11] Advanced age, chronic hypertension, smoking and diabetes mellitus are risk factors. It is unclear whether there is an association with alcohol ...
Both the left and right hemispheres of the brain have a lateral geniculate nucleus, named after its resemblance to a bent knee (genu is Latin for "knee"). In humans as well as in many other primates, the LGN has layers of magnocellular cells and parvocellular cells that are interleaved with layers of koniocellular cells.
The cells of the brain include neurons and supportive glial cells. There are more than 86 billion neurons in the brain, and a more or less equal number of other cells. Brain activity is made possible by the interconnections of neurons and their release of neurotransmitters in response to nerve impulses.
Ependymal cells, also named ependymocytes, line the spinal cord and the ventricular system of the brain. These cells are involved in the creation and secretion of cerebrospinal fluid (CSF) and beat their cilia to help circulate the CSF and make up the blood-CSF barrier. They are also thought to act as neural stem cells. [15] CNS: Radial glia
Since K cells are a heterogeneous group of cells, it is likely that they contain subclasses which fulfill different functions. Some cells respond to colour, some to achromatic gratings and still others are unresponsive to any types of gratings. Experimental results suggest that K cells could contribute to aspects of spatial and temporal vision ...