Biology – The natural science that studies life. Areas of focus include structure, function, growth, origin, evolution, distribution, and taxonomy.
The endocrine system is a messenger system in an organism comprising feedback loops of hormones that are released by internal glands directly into the circulatory system and that target and regulate distant organs. In vertebrates, the hypothalamus is the neural control center for all endocrine systems.
The endoplasmic reticulum (ER) is a part of a transportation system of the eukaryotic cell, and has many other important functions such as protein folding. It is a type of organelle made up of two subunits – rough endoplasmic reticulum (RER), and smooth endoplasmic reticulum (SER). The endoplasmic reticulum is found in most eukaryotic cells and forms an interconnected network of flattened, membrane-enclosed sacs known as cisternae, and tubular structures in the SER. The membranes of the ER are continuous with the outer nuclear membrane. The endoplasmic reticulum is not found in red blood cells, or spermatozoa.
The human body is the entire structure of a human being. It is composed of many different types of cells that together create tissues and subsequently organs and then organ systems.
A gland is a cell or an organ in an animal's body that produces and secretes different substances either into the bloodstream or into a body cavity or outer surface that the organism needs. A gland may also function to remove unwanted substances such as urine from the body.
In biology, tissue is an assembly of similar cells and their extracellular matrix from the same embryonic origin that together carry out a specific function. Tissues occupy a biological organizational level between cells and a complete organ. Accordingly, organs are formed by the functional grouping together of multiple tissues.
In a multicellular organism, an organ is a collection of tissues joined in a structural unit to serve a common function. In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to act together in a function. Tissues of different types combine to form an organ which has a specific function. The intestinal wall for example is formed by epithelial tissue and smooth muscle tissue. Two or more organs working together in the execution of a specific body function form an organ system, also called a biological system or body system.
The autonomic nervous system (ANS), sometimes called the visceral nervous system and formerly the vegetative nervous system, is a division of the nervous system that operates internal organs, smooth muscle and glands. The autonomic nervous system is a control system that acts largely unconsciously and regulates bodily functions, such as the heart rate, its force of contraction, digestion, respiratory rate, pupillary response, urination, and sexual arousal. This system is the primary mechanism in control of the fight-or-flight response.
Biology is the study of life and its processes. Biologists study all aspects of living things, including all of the many life forms on earth and the processes in them that enable life. These basic processes include the harnessing of energy, the synthesis and duplication of the materials that make up the body, the reproduction of the organism and many other functions. Biology, along with chemistry and physics is one of the major disciplines of natural science.
The pineal gland is a small endocrine gland in the brain of most vertebrates. In the darkness the pineal gland produces melatonin, a serotonin-derived hormone, which modulates sleep patterns following the diurnal cycles. The shape of the gland resembles a pine cone, which gives it its name. The pineal gland is located in the epithalamus, near the center of the brain, between the two hemispheres, tucked in a groove where the two halves of the thalamus join. It is one of the neuroendocrine secretory circumventricular organs in which capillaries are mostly permeable to solutes in the blood.
Pinealocytes are the main cells contained in the pineal gland, located behind the third ventricle and between the two hemispheres of the brain. The primary function of the pinealocytes is the secretion of the hormone melatonin, important in the regulation of circadian rhythms. In humans, the suprachiasmatic nucleus of the hypothalamus communicates the message of darkness to the pinealocytes, and as a result, controls the day and night cycle. It has been suggested that pinealocytes are derived from photoreceptor cells. Research has also shown the decline in the number of pinealocytes by way of apoptosis as the age of the organism increases. There are two different types of pinealocytes, type I and type II, which have been classified based on certain properties including shape, presence or absence of infolding of the nuclear envelope, and composition of the cytoplasm.
In cell biology, microsomes are heterogeneous vesicle-like artifacts re-formed from pieces of the endoplasmic reticulum (ER) when eukaryotic cells are broken-up in the laboratory; microsomes are not present in healthy, living cells.
Endocrine glands are ductless glands of the endocrine system that secrete their products, hormones, directly into the blood. The major glands of the endocrine system include the pineal gland, pituitary gland, pancreas, ovaries, testicles, thyroid gland, parathyroid gland, hypothalamus and adrenal glands. The hypothalamus and pituitary glands are neuroendocrine organs.
Endoplasm generally refers to the inner, dense part of a cell's cytoplasm. This is opposed to the ectoplasm which is the outer (non-granulated) layer of the cytoplasm, which is typically watery and immediately adjacent to the plasma membrane. The nucleus is separated from the endoplasm by the nuclear envelope. The different makeups/viscosities of the endoplasm and ectoplasm contribute to the amoeba's locomotion through the formation of a pseudopod. However, other types of cells have cytoplasm divided into endo- and ectoplasm. The endoplasm, along with its granules, contains water, nucleic acids, amino acids, carbohydrates, inorganic ions, lipids, enzymes, and other molecular compounds. It is the site of most cellular processes as it houses the organelles that make up the endomembrane system, as well as those that stand alone. The endoplasm is necessary for most metabolic activities, including cell division.
In cellular neuroscience, Nissl bodies are discrete granular structures in neurons that consist of rough endoplasmic reticulum, a collection of parallel, membrane-bound cisternae studded with ribosomes on the cytosolic surface of the membranes. Nissl bodies were named after Franz Nissl, a German neuropathologist who invented the staining method bearing his name. The term "Nissl bodies" generally refers to discrete clumps of rough endoplasmic reticulum and free ribosomes in nerve cells. Masses of rough endoplasmic reticulum also occur in some non-neuronal cells, where they are referred to as ergastoplasm, basophilic bodies, or chromophilic substance. While these organelles differ in some ways from Nissl bodies in neurons, large amounts of rough endoplasmic reticulum are generally linked to the copious production of proteins.
This article describes the anatomy of the head and neck of the human body, including the brain, bones, muscles, blood vessels, nerves, glands, nose, mouth, teeth, tongue, and throat.
In cellular biology, inclusions are diverse intracellular non-living substances that are not bound by membranes. Inclusions are stored nutrients/deutoplasmic substances, secretory products, and pigment granules. Examples of inclusions are glycogen granules in the liver and muscle cells, lipid droplets in fat cells, pigment granules in certain cells of skin and hair, and crystals of various types. Cytoplasmic inclusions are an example of a biomolecular condensate arising by liquid-solid, liquid-gel or liquid-liquid phase separation.
The following outline is provided as an overview of and topical guide to cell biology:
Fat globules are individual pieces of intracellular fat in human cell biology. The lipid droplet's function is to store energy for the organism's body and is found in every type of adipocytes. They can consist of a vacuole, droplet of triglyceride, or any other blood lipid, as opposed to fat cells in between other cells in an organ. They contain a hydrophobic core and are encased in a phospholipid monolayer membrane. Due to their hydrophobic nature, lipids and lipid digestive derivatives must be transported in the globular form within the cell, blood, and tissue spaces.
This glossary of biology terms is a list of definitions of fundamental terms and concepts used in biology, the study of life and of living organisms. It is intended as introductory material for novices; for more specific and technical definitions from sub-disciplines and related fields, see Glossary of cell biology, Glossary of genetics, Glossary of evolutionary biology, Glossary of ecology, Glossary of environmental science and Glossary of scientific naming, or any of the organism-specific glossaries in Category:Glossaries of biology.
