Micrograph
40x micrograph of a canine rectum cross section. A photomicrograph of a thin section of a limestone with ooids. The largest is approximately 1.2 mm in diameter. The red object in the lower left is a scale bar indicating relative size. Approximately 10x micrograph of a doubled die on a coin, where the date was struck twice. A micrograph, or photomicrograph, is a photograph or digital image taken through a microscope or similar device to show a magnified image of an item. Micrographs are widely used in all fields of microscopy. Types[edit] Photomicrograph[edit] A light micrograph or photomicrograph is a micrograph prepared using an optical microscope, a process referred to as photomicroscopy. Roman Vishniac was a pioneer in the field of photomicroscopy, specializing in the photography of living creatures in full motion. Electron micrograph[edit] An electron micrograph is a micrograph prepared using an electron microscope. Digital micrograph[edit] Magnification and micron bars[edit] Gallery[edit]
Microscope
A microscope (from the Ancient Greek: μικρός, mikrós, "small" and σκοπεῖν, skopeîn, "to look" or "see") is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy. Microscopic means invisible to the eye unless aided by a microscope. There are many types of microscopes, the most common and first to be invented is the optical microscope which uses light to image the sample. History[edit] The first microscope to be developed was the optical microscope, although the original inventor is not easy to identify. Rise of modern light microscopy[edit] The first detailed account of the interior construction of living tissue based on the use of a microscope did not appear until 1644, in Giambattista Odierna's L'occhio della mosca, or The Fly's Eye.[4] It was not until the 1660s and 1670s that the microscope was used extensively for research in Italy, The Netherlands and England. Types[edit]
Eukaryote
Eukaryotes can reproduce both asexually through mitosis and sexually through meiosis and gamete fusion. In mitosis, one cell divides to produce two genetically identical cells. In meiosis, DNA replication is followed by two rounds of cell division to produce four daughter cells each with half the number of chromosomes as the original parent cell (haploid cells). These act as sex cells (gametes – each gamete has just one complement of chromosomes, each a unique mix of the corresponding pair of parental chromosomes) resulting from genetic recombination during meiosis. Cell features[edit] Eukaryotic cells are typically much larger than those of prokaryotes. Internal membrane[edit] Detail of the endomembrane system and its components A 3D rendering of an animal cell cut in half. The nucleus is surrounded by a double membrane (commonly referred to as a nuclear membrane or nuclear envelope), with pores that allow material to move in and out. Vesicles may be specialized for various purposes.
Cell nucleus
HeLa cells stained for the cell nucleus DNA with the BlueHoechst dye. The central and rightmost cell are in interphase, thus their entire nuclei are labeled. On the left, a cell is going through mitosis and its DNA has condensed. Because the nuclear membrane is impermeable to large molecules, nuclear pores are required that regulate nuclear transport of molecules across the envelope. The pores cross both nuclear membranes, providing a channel through which larger molecules must be actively transported by carrier proteins while allowing free movement of small molecules and ions. History[edit] Between 1877 and 1878, Oscar Hertwig published several studies on the fertilization of sea urchin eggs, showing that the nucleus of the sperm enters the oocyte and fuses with its nucleus. Structures[edit] Nuclear envelope and pores[edit] Nuclear pores, which provide aqueous channels through the envelope, are composed of multiple proteins, collectively referred to as nucleoporins. Nuclear lamina[edit]
Ageing
Ageing (British English) or aging (American English) is the accumulation of changes in a person over time.[1] Ageing in humans refers to a multidimensional process of physical, psychological, and social change. Some dimensions of ageing grow and expand over time, while others decline. Reaction time, for example, may slow with age, while knowledge of world events and wisdom may expand. Research shows that even late in life, potential exists for physical, mental, and social growth and development.[2] Ageing is an important part of all human societies reflecting the biological changes that occur, but also reflecting cultural and societal conventions. Ageing is among the largest known risk factors for most human diseases.[3] Roughly 100,000 people worldwide die each day of age-related causes.[4] Age is measured chronologically, and a person's birthday is often an important event. Population ageing is the increase in the number and proportion of older people in society. Senescence[edit]
Poliomyelitis
Although approximately 90% of polio infections cause no symptoms at all, affected individuals can exhibit a range of symptoms if the virus enters the blood stream.[3] In about 1% of cases, the virus enters the central nervous system, preferentially infecting and destroying motor neurons, leading to muscle weakness and acute flaccid paralysis. Different types of paralysis may occur, depending on the nerves involved. Spinal polio is the most common form, characterized by asymmetric paralysis that most often involves the legs. Bulbar polio leads to weakness of muscles innervated by cranial nerves. Poliomyelitis was first recognized as a distinct condition by Jakob Heine in 1840.[5] Its causative agent, poliovirus, was identified in 1908 by Karl Landsteiner.[5] Polio had existed for thousands of years in certain areas, with depictions of the disease in ancient art. Classification The term "poliomyelitis" is used to identify the disease caused by any of the three serotypes of poliovirus.
