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Parafollicular Cell
Parafollicular cells, also called C cells, are neuroendocrine cells in the thyroid. They are called C cells because the primary function of these cells is to secrete calcitonin. They are located adjacent to the thyroid follicles and reside in the connective tissue. These cells are large and have a pale stain compared with the follicular cells. In teleost and avian species these cells occupy a structure outside the thyroid gland named the ultimopharyngeal body. Structure Parafollicular cells are pale-staining cells found in small number in the thyroid and are typically situated basally in the epithelium, without direct contact with the follicular lumen. They are always situated within the basement membrane, which surrounds the entire follicle. Development Parafollicular cells are derived from pharyngeal endoderm. Embryologically, they associate with the ultimopharyngeal body, which is a ventral derivative of the fourth (or fifth) pharyngeal pouch. Parafollicular cells were ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Thyroid
The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans, it is a butterfly-shaped gland located in the neck below the Adam's apple. It consists of two connected lobes. The lower two thirds of the lobes are connected by a thin band of tissue called the isthmus (: isthmi). Microscopically, the functional unit of the thyroid gland is the spherical thyroid follicle, lined with follicular cells (thyrocytes), and occasional parafollicular cells that surround a lumen containing colloid. The thyroid gland secretes three hormones: the two thyroid hormones triiodothyronine (T3) and thyroxine (T4)and a peptide hormone, calcitonin. The thyroid hormones influence the metabolic rate and protein synthesis and growth and development in children. Calcitonin plays a role in calcium homeostasis. Secretion of the two thyroid hormones is regulated by thyroid-stimulating hormone (TSH), which is secreted from the anterior pituitary gland. TSH is regulated by thy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Bone Resorption
Bone resorption is resorption of bone tissue, that is, the process by which osteoclasts break down the tissue in bones and release the minerals, resulting in a transfer of calcium from bone tissue to the blood. The osteoclasts are multi-nucleated cells that contain numerous mitochondria and lysosomes. These are the cells responsible for the resorption of bone. Osteoblasts are generally present on the outer layer of bone, just beneath the periosteum. Attachment of the osteoclast to the osteon begins the process. The osteoclast then induces an infolding of its cell membrane and secretes collagenase and other enzymes important in the resorption process. High levels of calcium, magnesium, phosphate and products of collagen will be released into the extracellular fluid as the osteoclasts tunnel into the mineralized bone. Osteoclasts are prominent in the tissue destruction found in psoriatic arthritis and rheumatological disorders. The human body is in a constant state of bone re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Peptide Hormone Secreting Cells
Peptides are short chains of amino acids linked by peptide bonds. A polypeptide is a longer, continuous, unbranched peptide chain. Polypeptides that have a molecular mass of 10,000 Da or more are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides. Peptides fall under the broad chemical classes of biological polymers and oligomers, alongside nucleic acids, oligosaccharides, polysaccharides, and others. Proteins consist of one or more polypeptides arranged in a biologically functional way, often bound to ligands such as coenzymes and cofactors, to another protein or other macromolecule such as DNA or RNA, or to complex macromolecular assemblies. Amino acids that have been incorporated into peptides are termed residues. A water molecule is released during formation of each amide bond.. All peptides except cyclic peptides have an N-terminal (amine group) and C-terminal (carboxyl group) residu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Endocrine System Anatomy
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. In humans, the major endocrine glands are the thyroid, parathyroid, pituitary, pineal, and adrenal glands, and the (male) testis and (female) ovaries. The hypothalamus, pancreas, and thymus also function as endocrine glands, among other functions. (The hypothalamus and pituitary glands are organs of the neuroendocrine system. One of the most important functions of the hypothalamusit is located in the brain adjacent to the pituitary glandis to link the endocrine system to the nervous system via the pituitary gland.) Other organs, such as the kidneys, also have roles within the endocrine system by secreting certain hormones. The study of the endocrine system and its disorders ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
List Of Distinct Cell Types In The Adult Human Body
The list of human cell types provides an enumeration and description of the various specialized cells found within the human body, highlighting their distinct functions, characteristics, and contributions to overall physiological processes. Cells may be classified by their physiological function, histology (microscopic anatomy), lineage, or gene expression. Total number of cells The adult human body is estimated to contain about 30 trillion (3×1013) human cells, with the number varying between 20 and 100 trillion depending on factors such as sex, age, and weight. Additionally, there are approximately an equal number of bacterial cells. The exact count of human cells has not yet been empirically measured in its entirety and is estimated using different approaches based on smaller samples of empirical observation. It is generally assumed that these cells share features with each other and thus may be organized as belonging to a smaller number of types. Classification ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
List Of Human Cell Types Derived From The Germ Layers
This is a list of Cell (biology), cells in humans derived from the three embryonic germ layers – ectoderm, mesoderm, and endoderm. Cells derived from ectoderm Surface ectoderm Skin * Trichocyte (human), Trichocyte * Keratinocyte Anterior pituitary * Gonadotropic cell, Gonadotrope * Corticotropic cell, Corticotrope * Thyrotropic cell, Thyrotrope * Somatotropic cell, Somatotrope * Prolactin cell, Lactotroph Tooth enamel * Ameloblast Neural crest Peripheral nervous system * Neuron * Neuroglia, Glia ** Schwann cell ** Satellite glial cell Neuroendocrine system * Chromaffin cell * Glomus cell Skin * Melanocyte ** Nevus cell * Merkel cell Teeth * Odontoblast * Cementoblast Eyes * Corneal keratocyte Smooth muscle Neural tube Central nervous system * Neuron * Glia ** Astrocyte ** Ependyma, Ependymocytes ** Müller glia (retina) ** Oligodendrocyte ** Oligodendrocyte progenitor cell ** Pituicyte (posterior pituitary) Pineal gland * Pinealocyte Cells derived from mesoderm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Medullary Thyroid Cancer
Medullary thyroid cancer is a form of thyroid carcinoma which originates from the parafollicular cells (C cells), which produce the hormone calcitonin.Hu MI, Vassilopoulou-Sellin R, Lustig R, Lamont JP"Thyroid and Parathyroid Cancers"in Pazdur R, Wagman LD, Camphausen KA, Hoskins WJ (EdsCancer Management: A Multidisciplinary Approach 11 ed. 2008. Medullary tumors are the third most common of all thyroid cancers and together make up about 3% of all thyroid cancer cases. MTC was first characterized in 1959. Approximately 25% of medullary thyroid cancer cases are genetic in nature, caused by a mutation in the RET proto-oncogene. When MTC occurs by itself it is termed sporadic medullary thyroid cancer. Medullary thyroid cancer is seen in people with multiple endocrine neoplasia type 2, subtypes 2A and 2B. When medullary thyroid cancer due to a hereditary genetic disorder occurs without other endocrine tumours it is termed familial medullary thyroid cancer. Signs and symptoms The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Thyrotropin-releasing Hormone
Thyrotropin-releasing hormone (TRH) is a hypophysiotropic hormone produced by neurons in the hypothalamus that stimulates the release of thyroid-stimulating hormone (TSH) as well as prolactin from the anterior pituitary. TRH has been used clinically in diagnosis of hyperthyroidism, and for the treatment of spinocerebellar degeneration and disturbance of consciousness in humans. Its pharmaceutical form is called protirelin ( INN) (). Physiology Synthesis and release TRH is synthesized within parvocellular neurons of the paraventricular nucleus of the hypothalamus. It is translated as a 242-amino acid precursor polypeptide that contains 6 copies of the sequence -Gln-His-Pro-Gly-, with both ends of the sequence flanked by Lys-Arg or Arg-Arg sequences. To produce the mature form, a series of enzymes are required. First, a protease cleaves to the C-terminal side of the flanking Lys-Arg or Arg-Arg. Second, a carboxypeptidase removes the Lys/Arg residues leaving Gly a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
CGRP
Calcitonin gene-related peptide (CGRP) is a neuropeptide that belongs to the calcitonin family. Human CGRP consists of two isoforms, CGRP alpha (α-CGRP, also known as CGRP I) and CGRP beta (β-CGRP, also known as CGRP II). α-CGRP is a 37-amino acid neuropeptide formed by alternative splicing of the calcitonin/CGRP gene located on chromosome 11. β-CGRP is less studied. In humans, β-CGRP differs from α-CGRP by three amino acids and is encoded in a separate, nearby gene. The CGRP family includes calcitonin (CT), adrenomedullin (AM), and amylin (AMY). Function CGRP is produced in both peripheral and central neurons. It is a potent peptide vasodilator and can function in the transmission of nociception. In the spinal cord, the function and expression of CGRP may differ depending on the location of synthesis. CGRP is derived mainly from the cell bodies of motor neurons when synthesized in the ventral horn of the spinal cord and may contribute to the regeneration of nervous t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Somatostatin
Somatostatin, also known as growth hormone-inhibiting hormone (GHIH) or by #Nomenclature, several other names, is a peptide hormone that regulates the endocrine system and affects neurotransmission and cell proliferation via interaction with G protein-coupled somatostatin receptors and inhibition of the release of numerous secondary hormones. Somatostatin inhibits insulin and glucagon secretion. Somatostatin has two active forms produced by the alternative cleavage of a single preproprotein: one consisting of 14 amino acids (shown in infobox to right), the other consisting of 28 amino acids. Among the vertebrates, there exist six different somatostatin genes that have been named: ''SS1'', ''SS2'', ''SS3'', ''SS4'', ''SS5'' and ''SS6''. Zebrafish have all six. The six different genes, along with the five different somatostatin receptors, allow somatostatin to possess a large range of functions. Humans have only one somatostatin gene, ''SST''. Nomenclature Synonyms of "somatost ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Serotonin
Serotonin (), also known as 5-hydroxytryptamine (5-HT), is a monoamine neurotransmitter with a wide range of functions in both the central nervous system (CNS) and also peripheral tissues. It is involved in mood, cognition, reward, learning, memory, and physiological processes such as vomiting and vasoconstriction. In the CNS, serotonin regulates mood, appetite, and sleep. Most of the body's serotonin—about 90%—is synthesized in the gastrointestinal tract by enterochromaffin cells, where it regulates intestinal movements. It is also produced in smaller amounts in the brainstem's raphe nuclei, the skin's Merkel cells, pulmonary neuroendocrine cells, and taste receptor cells of the tongue. Once secreted, serotonin is taken up by platelets in the blood, which release it during clotting to promote vasoconstriction and platelet aggregation. Around 8% of the body's serotonin is stored in platelets, and 1–2% is found in the CNS. Serotonin acts as both a vasoconstrictor and vas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Osteoclast
An osteoclast () is a type of bone cell that breaks down bone tissue. This function is critical in the maintenance, repair, and bone remodeling, remodeling of bones of the vertebrate, vertebral skeleton. The osteoclast disassembles and digests the composite of hydrated protein and mineral at a molecular level by secreting acid and a collagenase, a process known as ''bone resorption''. This process also helps regulate the level of blood calcium. Osteoclasts are found on those surfaces of bone that are undergoing resorption. On such surfaces, the osteoclasts are seen to be located in shallow depressions called ''resorption bays (Howship's lacunae)''. The resorption bays are created by the erosive action of osteoclasts on the underlying bone. The border of the lower part of an osteoclast exhibits finger-like processes due to the presence of deep infoldings of the cell membrane; this border is called ''ruffled border''. The ruffled border lies in contact with the bone surface within a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
