Mitochondria are often called the powerhouses of the cell. Osteoblasts are bone-forming cells whereas osteoclasts are degradative cells that break down and reabsorb bone. Typically, an osteocyte may be around 7 micrometers deep and 15 micrometers broad in length. The Journal of Biophysical and Biochemical Cytology 11: 627649. The osteoclasts are the mediators of the continuous destruction of bone. We explain how they got this title, and outline other important roles that they carry out. Last medically reviewed on August 24, 2022. Osteoprogenitor cells give rise to active osteoblasts. [6] 1020% of osteoblasts differentiate into osteocytes. Cartilaginous Joint Structure, Function & Examples. Nouveau bone overlays onto dead trabeculae along with fragmentary resorption of dead bone. In intramembranous ossification, the mesenchymal tissue is converted directly to a bone (direct ossification). Osteoblasts are the ones that are responsible for bone formation and osteoclasts are responsible for bone resorption. The .gov means its official. Omissions? It has been demonstrated that skeletal unloading can produce osteocyte hypoxia in vivo. Below are some of the most important: The nucleus represents the cells headquarters. Osteostracans (early jawless vertebrates) are the sister group to jawed vertebrates, gnathostomes and their last common ancestor could have been the first to evolve osteocytes. Osteoid-osteocytes must break collagen and other matrix-embedded cell components to control mineralization and create connective dendritic processes. Osteoclasts and osteoblasts may turn into osteocytes white new bone is being formed, and then osteocytes get surrounded by new bone. It helps the cell maintain the correct shape. [14][18][15][13], Osteocytes synthesize sclerostin, a secreted protein that inhibits bone formation by binding to LRP5/LRP6 coreceptors and blunting Wnt signaling. They contain stored fats called triglycerides that the body can use as energy. As osteocytes may have appeared entombed in the mineralized matrix, they are not dead cells. 2023 Mar 3;12(3):399. doi: 10.3390/biology12030399. In females, meiosis begins during the fetal stage, before the individual is born. There are at least three main types of bone cells: There are many types of blood cells, including: Also called myocytes, muscle cells are long, tubular cells. Osteocytes remain in contact with each other and with cells on the bone surface via gap junction-coupled cell processes passing through the matrix via small channels, the canaliculi, that connect the cell body-containing lacunae with each other and with the outside world. They also are long-lived, surviving as long as the bone they occupy exists. Osteocytes are mature osteoblasts that have become trapped within the very bone matrix they produced. An osteocyte is a mature bone cell, and is eukaryotic. [5] The cell also exhibits a reduced size endoplasmic reticulum, Golgi apparatus and mitochondria, and cell processes that radiate largely towards the bone surfaces in circumferential lamellae, or towards a haversian canal and outer cement line typical of osteons in concentric lamellar bone. [11] It is now recognized that osteocytes respond in a variety of ways to the presence of implant biomaterials.[26]. Plus, get practice tests, quizzes, and personalized coaching to help you doi: 10.1371/journal.pone.0269348. Get unlimited access to over 88,000 lessons. It is the largest human cell. Cunningham HC, Orr S, Murugesh DK, Hsia AW, Osipov B, Go L, Wu PH, Wong A, Loots GG, Kazakia GJ, Christiansen BA. When the osteocytes in your bones receive hormonal signals from your parathyroid glands, your thyroid gland, and other organs, they secrete their own chemical messengers, which enter your bloodstream and help regulate the excretion of minerals through your kidneys. and transmitted securely. Scientists are still sorting out the details of how these fascinating cells work; their research into the workings of osteocytes may uncover new ways to treat fractures and other conditions, such as osteoporosis. National Library of Medicine In particular, osteocytes have been known to play in mineral homeostasis, mechano-sensing, and orchestrating bone remodeling. I graduated from the University of Massachusetts in 2018 with my degree in Biology. Oxygen tension may be responsible for controlling the growth of osteoblasts into osteocytes and disuse-induced bone resorption may be mediated by hypoxia in osteocytes. 8600 Rockville Pike Under the electron microscope, there were a few . Osteocytes are cells embedded in bone, able to modify their surrounding extracellular matrix via specialized molecular remodeling . [6], Osteocytes are mechanosensor cells that control the activity of osteoblasts and osteoclasts[15] within a basic multicellular unit (BMU), a temporary anatomic structure where bone remodeling occurs. We explain what a neuron looks like, what it does, and how it works. Bones consist of three major cell groups: osteoblasts, osteoclasts, and osteocytes. [8], During bone formation, an osteoblast is left behind and buried in the bone matrix as an "osteoid osteocyte", which maintains contact with other osteoblasts through extended cellular processes. Helper T Cells Function & Activation | What Do Helper T Cells Do? Osteocyte cell death can occur in association with pathologic conditions such as osteoporosis and osteoarthritis, which leads to increased skeletal fragility, linked to the loss of ability to sense microdamage and/or signal repair. [13], Although osteocytes are relatively inert cells, they are capable of molecular synthesis and modification, as well as transmission of signals over long distances, in a way similar to the nervous system. They serve to keep a proper balance between the two to ensure that the bone remains healthy. Biology (Basel). Create your account. Osteocyte eCollection 2022 Jan. Osteonal Microcracking Pattern: A Potential Vitality Marker in Human Bone Trauma. Bone Cells Types & Function | What Do Bone Cells Do? In addition, a smaller Golgi apparatus, mitochondria, and endoplasmic reticulum are osteocyte organelles. It is these processes that travel through the canaliculi connecting lacunae to lacunae and to the blood supply. Biology definition: An osteocyte is a mature bone cell. Sclerostin, a protein produced by osteocytes, plays an important role in bone remodeling, but it is only one of many substances produced by osteocytes. Bone metabolism and evolutionary origin of osteocytes: Novel application of FIB-SEM tomography. [11] As the osteoblast transitions to an osteocyte, alkaline phosphatase is reduced, and casein kinase II is elevated, as is osteocalcin. - Discussion: - osteoclast is a large multinucleated cell that plays an active role in bone resorption; - monocytes from the marrow or the blood serve as precursors of osteoclasts; - osteoclasts are found in notches or indentations of bone surfaces called Howship's lacunae; - lacunae are 100 or . In endochondral ossification, the mesenchymal cells first differentiate into chondrocytes, the cells that form the cartilage, and later the cartilage is replaced by bone (indirect ossification). Alkaline phosphatase levels decrease while the levels of osteocalcin and casein kinase II increase during the transformation of an osteoblast into an osteocyte. As a result, the mature osteocytes cell body is 70% reduced in volume than that of the osteoblast. Apart from the osteocytes, the other main types of bone cells are osteoclasts, osteoblasts, and lining cells. Sclerostin antagonizes the activity of BMP (bone morphogenetic protein), a cytokine that induces bone and cartilage formation. Pyknosis of the nuclei is the earliest indicator of osteonecrosis, followed by the presence of hollow osteocyte lacunae. (Haridy et al., 2021). An organelle (think of it as a cell's internal organ) is a membrane bound structure found within a cell. Flagella (singular = flagellum) are long, hair-like structures that extend from the plasma membrane and are used to move an entire cell, (for example, sperm, Euglena ). By means of these canaliculi, nutrients and waste products are exchanged to maintain the viability of the osteocyte. Cell types can look different, and carry out distinct roles within the body. The https:// ensures that you are connecting to the Lets now take a look at the osteocyte structure (see bone cell diagram below). The osteocytes are no longer mitotically active (thus, have undergone osteocyte differentiation) and have reduced synthetic activity. Bone consists of four types of cells: osteoblasts, osteoclasts, osteocytes, and osteoprogenitor (or osteogenic) cells. Compared with the sperm cell, the female egg cell is a giant. Trabeculae Bone Function | What Is a Trabecula? Matrix metalloproteinases (MMPs), osteoblasts and osteocytes factor 45 (OF45), dentin matrix protein 1 (DMP-1), Klotho, lysophosphatidic acid (LPA), E11 antigen, TGF-beta inducible factor (TIEG), and healthy osteocytes are produced in the proper numbers or in certain distributions, all of which are dependent on adequate levels of oxygen. In humans, cells build tissues, tissues form organs, and organs work together to keep the body alive. The viability of osteocytes is enhanced by mechanical stress, which also aids in the movement of solutes via the lacuno-canalicular system in bone, hence improving O2 level and nutrient flow into the osteocytes themselves. More than 200 different types of cells are present in the human body. In bone tissue, the form of the mature bone cells is known as an osteocyte, which has dendritic processes and an oblate shape. (2022). [11], Mechanical loading increases osteocyte viability in vitro, and contributes to solute transport through the lacuno-canalicular system in bone, which enhances oxygen and nutrient exchange and diffusion to osteocytes. [14] Osteocyte-specific proteins such as sclerostin have been shown to function in mineral metabolism, as well as other molecules such as PHEX, DMP-1, MEPE, and FGF-23, which are highly expressed by osteocytes and regulate phosphate and biomineralization. They are stellate shaped cells that have many processes extending from their cell body which they use to communicate with neighboring osteocytes. [6], Osteocytes are an important regulator of bone mass. Cells lacking the distinctive qualities of sparse and include mitochondria, granular and smooth surfaced endoplasmic reticulum, and small numbers of vesicles. Blood Cells. Cells are the basic units of life. Content provided and moderated by Biology Online Editors. Cisternae are long sacs that make the ER. They are networked to each other via long cytoplasmic extensions that occupy tiny canals called canaliculi, which are used for exchange of nutrients and waste through gap junctions. [14][15] Osteocytes contain glutamate transporters that produce nerve growth factors after bone fracture, evidence of a sensing and information transfer system. Learn more about this disease and its symptoms", "The death of osteocytes via apoptosis accompanies estrogen withdrawal in human bone", "A Review of the Impact of Implant Biomaterials on Osteocytes", https://en.wikipedia.org/w/index.php?title=Osteocyte&oldid=1136397371, Short description is different from Wikidata, Creative Commons Attribution-ShareAlike License 3.0, This page was last edited on 30 January 2023, at 03:36. However, they do have a cell membrane, cytoplasm, ribosomes, and free-floating loops of DNA. The major difference is that bone cells do not divide or undergo mitosis. We link primary sources including studies, scientific references, and statistics within each article and also list them in the resources section at the bottom of our articles. Less sclerostin levels allow heightened osteoblast activity, which permits the production of additional bone in areas that are under stress. Osteocytes are cells that are located within the bone that are responsible for bone health. Would you like email updates of new search results? In one sense, cells are autonomous cities that function alone, producing their own energy and proteins. We avoid using tertiary references. Nerves cells form the communication system of the body. For example, Lynda Bonewald hypothesized that osteocytes secrete FGF23, which travels via the circulatory system and stimulates the kidneys to release phosphorus. The DNA for each gene is arranged in a specific order that determines the gene's function. Active osteoblasts, the bone-forming cells, act as groups (osteons) and connect with each other to form the bone matrix (osteoid). However, mitochondria have a number of other jobs, including calcium storage and a role in cell death. As the bone surfaces age, the level of TGF- decreases, and the gene expression of osteoclast-stimulatory factors, increases, which increases bone subsequent resorption, leading t bone loss. It is not intended to provide medical, legal, or any other professional advice. [7] Osteocyte size has been shown to covary with genome size; and this relationship has been used in paleogenomic research. An osteocyte is a mature bone cell. [10] The embedded "osteoid-osteocyte" must do two functions simultaneously: regulate mineralization and form connective dendritic processes, which requires cleavage of collagen and other matrix molecules. Micro damage in the bone structure is caused by recurrent occurrences of loading cycling, and it seems to be connected with the death of osteocytes caused by apoptosis. For instance, osteocytes can live long, depending on the skeletal age. They arise from the differentiation of osteogenic cells in the periosteum, the tissue that covers the outer surface of . In mature bones, osteocytes and their processes reside inside spaces called lacunae (Latin for a pit) and canaliculi, respectively. Osteocytes, also known as bone cells, have all the organelles found in other eukaryotic cells, such as a nucleus, mitochondria, cell membrane and endoplasmic reticulum. Just as everything in the world, osteocytes are not permanent and do have a lifespan of about 50 years (they have an average half-life of about 25 years, which means some die sooner and some die later). Cells are grouped into two different . What are osteocytes? For example, Lynda Bonewald determined that osteocytes make FGF23, which travels through the bloodstream to trigger the release of phosphorus by the kidneys. The activity of an osteocyte and the substances it secretes are themselves influenced by a variety of factors, including mechanical stresses on the bone, circulating hormones, and the amount of calcium and phosphorous in your bloodstream. Unlike other bone cells like osteoblasts and osteoclasts that are short-lived, osteocytes live relatively long and they dont divide. Many of the important reactions that take place in the cell occur in the cytoplasm. Bone tissue may be classified as compact or spongy, depending on its density and function. is known as an osteocyte, which has dendritic processes and an oblate shape. This site needs JavaScript to work properly. Skeletal muscle cells, for instance, have two. In the same way organs, such as the heart, liver, stomach, and kidneys, serve specific functions to keep an organism alive, organelles serve specific functions to keep a cell alive. In fact, from the perspective of your other organs, your skeleton is merely a storehouse for the calcium, magnesium, phosphorous, and trace minerals that are needed elsewhere. Natarajan D, Ye Z, Wang L, Ge L, Pathak JL. Whether in plants, humans, or animals, they connect to create a solid, well formed organism. The cytoskeleton forms the scaffolding within the cytoplasm of the human cell. Osteoblasts lay down new bone, which is initially somewhat soft but is transformed into a hardened matrix under the influence of hormones and other chemicals produced by osteoblasts. Secretin Function & Overview | What Does Secretin Do? There are several types of cells that build, remodel, and maintain bone. If the balance of nature is left untouched, landscapes can change dramatically over time. Osteoclast Function & Overview | What are Osteoclasts? Each cell type has a unique function and is found in different locations in bones. The plant cell wall is outside the cell membrane, and it provides structure for the cell. Its like a teacher waved a magic wand and did the work for me. Scientists use genetic rewiring to increase lifespan of cells, osteocytes, which help communicate with other bone cells, red blood cells, which carry oxygen around the body, white blood cells, which are part of the immune system, platelets, which help blood clot to prevent blood loss after injury, neutrophils and basophils, and other types of white blood cells. Osteocyte Definition The osteocyte is a mature bone cell. 2021 Dec 1;7(1):e10262. The site is secure. Now the cell transforms into a radical shape from the polygonal shape. The PubMed wordmark and PubMed logo are registered trademarks of the U.S. Department of Health and Human Services (HHS). All other trademarks and copyrights are the property of their respective owners. They produce new bone called "osteoid" which is made of bone collagen and other protein. People refer to them as diploid because they have two complete copies of the chromosomes. Do osteocytes have lysosomes? Osteoblasts form new bone, osteoclasts are responsible for the resorption of bone, and osteocytes are responsible for the balance of these two processes (bone formation and bone resorption). Clipboard, Search History, and several other advanced features are temporarily unavailable. Osteocytes regulate the formation of new bone and the resorption of old bone - dictating bone remodeling and repair. Both daughter cells have the same chromosomes as each other and the parent. osteoclast, large multinucleated cell responsible for the dissolution and absorption of bone. Create your account, 90 chapters | See answer (1) Copy. 2. Other major factors are parathyroid hormone and mechanical loading which decreases the sclerostin. Muscle cells are important for a range of functions, including movement, support, and internal functions, such as peristalsis the movement of food along the gut. Osteocytes, which are osteoblasts that have become trapped within the bone matrix, are responsible for many of the activities that keep your bones healthy. Other bone cell types are osteoprogenitor cells, osteoblasts, and osteoclasts. In humans, the osteocytes typically live through the human lifespan but some of them die from aging, typically after reaching menopausal age. An official website of the United States government. Osteoblast Function, Location & Differentiation | What are Osteoblast Cells? [23] Skeletal unloading has been shown to induce osteocyte hypoxia in vivo, this is when osteocytes undergo apoptosis and recruit osteoclasts to resorb bone. The endoplasmic reticulum (ER) processes molecules within the cell and helps transport them to their final destinations. Some differentiate to become a certain cell type, and others divide to produce more stem cells. Before using our website, please read our Privacy Policy. ON occurs after around two to three hours of anoxia, although the osteocyte histology markers of necrosis do not manifest until approximately twenty-four to seventy-two hours following hypoxia. Osteocytes have some interesting features. [11][15] Osteocyte regulation can be linked to disease. Let us know if you have suggestions to improve this article (requires login). There are approximately 42 billion of them in an adult human body. The cell processes radiate primarily towards the bone surface in circumferential lamellae, or towards a Haversian canal and outer cement line that are characteristic of osteons in concentric lamellae bone. An osteocyte that has reached maturity contains a single nucleus (mononucleated). As people age, their osteocytes' activity diminishes, and the average osteocyte's lifespan shortens. Chloroplasts are organelles that carry out photosynthesis, which makes the food plant cells need to live. 250 to 400 million years ago, osteocytes were found in fish (jawless types), according to historical data. They are important in the regulation of bone mass, acting as mechanosensor cells that control the activity of osteoblasts and osteoclasts during bone remodeling. They make up the majority of the bones cell population (31,900/ mm3 to 93,200/ mm3 from bovine cortical bone to transgenic mice bone respectively). Osteocytes can sense mechanical strain being placed on the bone, and secrete growth factors which activate bone growth in response. Osteoclasts occupy small depressions on the bone's . Due to derivation from osteoblasts, these cells are highly specialized in nature and are responsible for the maintenance of the bony matrix. They have been identified to operate in mineral metabolism. Osteocytes have a stellate shape, approximately 7 micrometers deep and wide by 15 micrometers in length. Mitosis is how most of the cells in the body divide. Mesenchymal cells are stem cells from where many types of cells come from and are mainly located in the bone marrow. Study now. Find out how vesicles function in the body and what the five main types of vesicle are. MNT is the registered trade mark of Healthline Media. osteoblast, large cell responsible for the synthesis and mineralization of bone during both initial bone formation and later bone remodeling. Bone cells are the cells that make up bone tissue. Aged osteocytes may die eventually from senescence. Osteoblast. By secreting substances through their dendrites, osteocytes can recruit or inhibit osteoclasts and osteoblasts and thus influence the remodeling of surrounding bone. sharing sensitive information, make sure youre on a federal Updates? Rare earth smart nanomaterials for bone tissue engineering and implantology: Advances, challenges, and prospects. Fat cells are also called adipocytes, the main adipose tissue constituents. In meiosis, the body produces sperm cells and egg cells. Such 'microdamage,' if unaddressed, would eventually result in fractures or collapse of weight-bearing bones. Osteocytes, also known as bone cells, have all the organelles found in other eukaryotic cells, such as a nucleus, mitochondria, cell membrane and endoplasmic reticulum. Osteocytes are the most abundant type of cell in mature bone tissue. This process releases more calcium into your bloodstream, where it is needed for proper nerve, muscle, and heart function. The osteocyte is ____ that is trapped in the matrix, 5. Note though that osteochondroprogenitor cells undergo cellular changes to becomeosteoprogenitor cells committed to developing into osteoblasts. Cytoplasmic processes of the osteocyte extend away from the cell toward other osteocytes in . There are two ER types: rough ER and smooth ER. Periosteum of Bone Function & Location | What Does the Periosteum Do? As osteocytes may have appeared entombed in the mineralized matrix, Osteocytes have some interesting features. Osteonecrosis is a term that describes the typical pattern of cell death as well as the complex bone formation and resorption and osteogenesis. During differentiation from osteoblasts to mature osteocyte the cells lose a large part of their cell organelles. 2023 Feb;167:116646. doi: 10.1016/j.bone.2022.116646. Osteocytes are stellate in shape. Bone Growth Process & Disorders | How do Bones Grow? Cytoplasmic processes of the osteocyte extend away from the cell toward other osteocytes in small channels called canaliculi. and osteocytes (which are found inside the bone and communicate with other bone cells). Bone formation is one of the distinctive characteristics of vertebrates. official website and that any information you provide is encrypted They function on their own, creating their own energy and self-replicating the cell is the smallest unit of life that can replicate. Sperm cells cannot divide. [21] Osteocytes die as a consequence of senescence, degeneration/necrosis, apoptosis (programmed cell death), and/or osteoclastic engulfment. osteocyte, a cell that lies within the substance of fully formed bone. In the mineralized type I collagen matrix, osteocytes generate a huge lacuna-canalicular network, with the assistance of cell bodies dwelling in lacunae and cell/dendritic processes residing in canaliculi. Decreases in certain hormonal levels play a prominent role in the skeletal aging process. [3] A mature osteocyte contains a single nucleus that is located toward the vascular side and has one or two nucleoli and a membrane. We also discuss how vesicles interact with other cells and. Even though it seems rigid and unchanging, bone is a living, metabolically active tissue. [6] Most of the receptor activities that play an important role in bone function are present in the mature osteocyte. It happens in stages. These are known as organelles or mini-organs. One of the osteocyte's jobs is to sense such injury and communicate with osteoblasts and osteoclasts, which then accomplish the necessary repairs. Osteoblasts that become trapped in their own secretions become the osteocytes. Bone-on-a-chip: microfluidic technologies and microphysiologic models of bone tissue. Osteocytes, which are cells inside the bone. A single diploid cell yields four haploidsperm cells. Osteocytes descend from osteoblasts. Distinguish among the four cell types in bone. [5] Osteocytes form an extensive lacunocanalicular network within the mineralized collagen type I matrix, with cell bodies residing within lacunae, and cell/dendritic processes within channels called canaliculi. It is the most common type of cell discovered. They are the longest-lived of all bone cells; many osteocytes survive for decades within their bony chambers. People may often refer to mitochondria as the powerhouses of cells. Inner Ear Anatomy | Structure, Function & Components. Although osteocytes have reduced synthetic activity and (like osteoblasts) are not capable of mitotic division, they are actively involved in the routine turnover of bony matrix, through various mechanosensory mechanisms. Tanaka-Kamioka, K., Kamioka, H., Ris, H., & Lim, S. S. (1998). As meiosis completes, it yields a single haploid egg cell each monthly cycle. [23] Microdamage in bone occurs as the result of repetitive events of cycling loading, and appears to be associated with osteocyte death by apoptosis, which appear to secrete a signal to target osteoclasts to perform remodeling at a damaged site. A mature osteocyte contains a single nucleus that is located toward the vascular side and has one or two nucleoli and a membrane. Osteoclasts are responsible for resorbing, or breaking down, bone matrix. Osteoblasts or lining cells: Osteoblasts are considered the main type of bone cells. - osteocytes. The parent cell splits into two daughter cells. This is quite long-lived for a cell, and within that lifespan, osteocytes are the communicators that drive the mechanisms of new bone formation and bone resorption. Sclerostin and other molecules such as FGF-23, DMP-1, PHEX, and MEPE which regulate phosphate and biomineralization, are highly expressed by osteocytes. Along with the fragmented resorption of dead bone, the nouveau bone will overlay on top of trabeculae that have died. They are also responsible for the mineral balance (calcium) within our body. At the periphery of necrosis, capillary revascularization and reactive hyperemia are very rare. The osteocyte is a mature bone cell. My name is Dee Patel and I am a current dental student in my third year! Structure. These bone cells are responsible for forming the bones (replacing the cartilage), and thus, the skeleton of vertebrates. 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