A condyle is the round prominence at the end of a bone, most part of a joint - an articulation with another bone. It is one of the markings or features of bones, can refer to: On the femur, in the knee joint: Medial condyle Lateral condyle On the tibia, in the knee joint: Medial condyle Lateral condyle On the humerus, in the elbow joint: Condyle of humerus On the mandible, in the temporomandibular joint: Mandibular condyle On the occipital bone, in the atlanto-occipital joint: Occipital condylesAlthough not termed condyles, the trochlea and capitulum of the humerus act as condyles in the elbow, the femur head acts as a condyle in the hip joint
The osteon or haversian system is the fundamental functional unit of much compact bone. Osteons are cylindrical structures that are several millimeters long and around 0.2 mm in diameter. They are present in many bones of most mammals and some bird and amphibian species; each osteon consists of concentric layers, or lamellae, of compact bone tissue that surround a central canal, the haversian canal. The haversian canal contains the bone's blood supplies; the boundary of an osteon is the cement line. Each haversian canal is surrounded by varying number of concentrically arranged lamellae of bone matrix. Near the surface of the compact bone, the lamellae are arranged parallel to the surface; some of the osteoblasts develop into each living within its own small space, or lacuna. Osteocytes make contact with the cytoplasmic processes of their counterparts via a network of small transverse canals, or canaliculi; this network facilitates the exchange of metabolic waste. Collagen fibers in a particular lamella run parallel to each other, but the orientation of collagen fibers within other lamellae is oblique.
The collagen fiber density is lowest at the seams between lamellae, accounting for the distinctive microscopic appearance of a transverse section of osteons. The space between osteons is occupied by interstitial lamellae, which are the remnants of osteons that were resorbed during the process of bone remodeling. Osteons are connected to each other and the periosteum by oblique channels called Volkmann's canals or perforating canals. Drifting osteons are a phenomenon, not understood. A "drifting osteon" is classified as one that runs both longitudinally as well as transversely through the cortex. An osteon can "drift" in one direction or change directions several times, leaving a tail of lamellae behind the advancing haversian canal. In bioarchaeological research and in forensic investigations, osteons in a bone fragment can be used to determine the sex of an individual and age, as well as aspects of taxonomy, diet and motor history. Osteons and their arrangement vary according to taxon, so that genus and sometimes species can be differentiated using a bone fragment not otherwise identifiable.
However, there is considerable variability among the different bones of a skeleton, features of some faunal osteons overlap with those of human osteons. More research is needed, but osteohistology has the potential to positively affect the studies in bioarchaeology and forensic investigations. In recent decades, osteohistological studies of dinosaur fossils have been used to address a number of issues, such as the periodicity of growth of dinosaurs and whether it was uniform across species and the question of whether dinosaurs were warm-blooded or not. Haversian canals Cortical bone Cancellous bone Cooper, Reginald R.. "Morphology of the Osteon: An Electron Microscopic Study". Journal of Bone and Joint Surgery. 48: 1239–1271. PMID 5921783. Netter, Frank H. Musculature system: anatomy and metabolic disorders. Summit, New Jersey: Chiba-Geiger Corporation ISBN 0-914168-88-6 SLIBS Bone Website: http://www.trinity.edu/stonily/bone/intro2.htm Bone - BioWeb at University of Wisconsin System Histology of osteons "Video explaining osteons" – via YouTube
A trabecula is a small microscopic, tissue element in the form of a small beam, strut or rod that supports or anchors a framework of parts within a body or organ. A trabecula has a mechanical function, is composed of dense collagenous tissue, they can be composed of other materials such as bone. In the heart, muscles form trabeculae septomarginal trabecula. Cancellous bone is formed from groupings of trabeculated bone tissue. In cross sections, trabeculae of a cancellous bone can look like septa, but in three dimensions they are topologically distinct, with trabeculae being rod or pillar-shaped and septa being sheet-like; when crossing fluid-filled spaces, trabeculae may have the function of resisting tension or providing a cell filter. Multiple perforations in a septum may reduce it to a collection of trabeculae, as happens to the walls of some of the pulmonary alveoli in emphysema. Trabecular bone called cancellous bone, is porous bone composed of trabeculated bone tissue, it can be found at the ends of long bones like the femur, where the bone is not solid but is full of holes connected by thin rods and plates of bone tissue.
Red bone marrow, where all the blood cells are made, fills. Though trabecular bone contains a lot of holes, its spatial complexity contributes the maximal strength with minimum mass, it is noted that the form and structure of trabecular bone are organized to optimally resist loads imposed by functional activities, like jumping and squatting. And according to the famous Wolff's Law, proposed in 1892, the external shape and internal architecture of bone are determined by the external stresses acting on it; the internal structure of the trabecular bone firstly undergoes adaptive changes along stress direction and the external shape of cortical bone undergoes secondary changes. Bone structure becomes thicker and denser to resist the external loading; because of increasing amount of total joint replacement and its impact on bone remodeling, understanding the stress-related and adaptive process of trabecular bone has become a central concern for bone physiologists. In order to understand the role of trabecular bone in age-related bone structure and design for bone-implant system, it is significant to study the mechanical properties of trabecular bone as a function of variables, such as anatomic site and age.
To do so, mechanical factors including modulus, uniaxial strength, fatigue properties are necessary to be studied. The porosity percent of trabecular bone is in the range 75–95% and the density ranges from 0.2 to 0.8g/cm3. It is noted that the porosity can reduce the strength of the bone, but reduce its weight; the porosity and the manner that porosity is structured effect the strength of material. Thus, the micro structure of trabecular bone is oriented and"grain" of porosity is aligned in a direction at which mechanical stiffness and strength are greatest; because of the microstructual directionality, the mechanical properties of trabecular bone is an-isotropic. The range of young's modulus for trabecular bone is 800-14000 MPa and the strength of failure is 1-100 MPa; as mentioned above, the mechanical properties of trabecular bone are sensitive to apparent density. The relationship between modulus of trabecular bone and its apparent density was demonstrated by Carter and Hayes in 1976; the resulting equation states: E = a + b ⋅ ρ c where E represents the modulus of trabecular bone in any loading direction, ρ represents the apparent density, a, b, c are constants depending on the architecture of tissue.
Additionally, from scanning electron microscopy, it was found that the variation in trabecular architecture with different anatomic sites lead to different modulus. To understand structure-anisotropy and material property relations, one must correlate the measured mechanical properties of anisotropic trabecular specimens with the stereologic descriptions of their architecture; the compressive strength of trabecular bone is very important because it is believed that the inside failure of trabecular bone arise from compressive stress. On the stress-strain curves for both trabecular bone and cortical bone with different apparent density, there are three stage in stress-strain curve; the first one is linear region where individual trabecula bend and compress as the bulk tissue is compressed. The second stage is after yielding, trabecular bonds start to fracture and the third stage is the stiffening stage. Lower density trabecular areas have more deformed stage before stiffening than higher density specimens.
In summary, trabecular bone is compliant and heterogeneous. The heterogeneous character makes it difficult to summarize the general mechanical properties for trabecular bone. High porosity makes trabecular bone compliant and large variations in architecture leads to high heterogeneity; the modulus and strength vary inversely with porosity and depend on the porosity structure. Additionally, the effects of aging and small cracks of trabecular bones on their mechanical properties will be analyzed more in final drafts. Studies have shown that once a human reaches adulthood, bone density decreases with age, to
Chondrocytes are the only cells found in healthy cartilage. They produce and maintain the cartilaginous matrix, which consists of collagen and proteoglycans. Although the word chondroblast is used to describe an immature chondrocyte, the term is imprecise, since the progenitor of chondrocytes can differentiate into various cell types, including osteoblasts. From least- to terminally-differentiated, the chondrocytic lineage is: Colony-forming unit-fibroblast Mesenchymal stem cell / marrow stromal cell Chondrocyte Hypertrophic chondrocyteMesenchymal stem cells are undifferentiated, meaning they can differentiate into a variety of generative cells known as osteochondrogenic cells; when referring to bone, or in this case cartilage, the undifferentiated mesenchymal stem cells lose their pluripotency and crowd together in a dense aggregate of chondrogenic cells at the location of chondrification. These chondrogenic cells differentiate into so-called chondroblasts, which synthesize the cartilage extracellular matrix, consisting of a ground substance and fibers.
The chondroblast is now a mature chondrocyte, inactive but can still secrete and degrade the matrix, depending on conditions. BMP4 and FGF2 have been experimentally shown to increase chondrocyte differentiation. Chondrocytes undergo terminal differentiation when they become hypertrophic, which happens during endochondral ossification; this last stage is characterized by major phenotypic changes in the cell. The chondrocyte in cartilage matrix has polygonal structure; the exception occurs at tissue boundaries, for example the articular surfaces of joints, in which chondrocytes may be flattened or discoid. Intra-cellular features are characteristic of a synthetically active cell; the cell density of full-thickness, adult, femoral condyle cartilage is maintained at 14.5 × 103 cells/ mm2 from age 20 to 30 years. Although chondrocyte senescence occurs with aging, mitotic figures are not seen in normal adult articular cartilage; the structure and synthetic activity of an adult chondrocyte are various according to its position.
Flattened cells are oriented parallel to the surface, along with the collagen fibers, in the superficial zone, the region of highest cell density. In the middle zone, chondrocytes are larger and more rounded and display a random distribution, in which the collagen fibers are more randomly arranged. In the deeper zones, chondrocytes form columns that are oriented perpendicular to the cartilage surface, along with the collagen fibers. Different behaviors may be exhibited by chondrocytes depending on their position within the different layers. In primary chondrocyte cultures, these zonal differences in synthetic properties may persist; the primary cilia are significant for spatial orientation of cells in developing growth plate and are sensory organelles in chondrocytes. Primary cilia work as centers for wingless type and hedgehog signaling and contain mechanosensitive receptors. Endochondral ossification Intramembranous ossification List of human cell types derived from the germ layers Dominici M, Hofmann T, Horwitz E. "Bone marrow mesenchymal cells: biological properties and clinical applications".
J Biol Regul Homeost Agents. 15: 28–37. PMID 11388742. Bianco P, Riminucci M, Gronthos S, Robey P. "Bone marrow stromal stem cells: nature and potential applications". Stem Cells. 19: 180–92. Doi:10.1634/stemcells.19-3-180. PMID 11359943. Histology image: 03317loa – Histology Learning System at Boston University Stem cell information
Intramembranous ossification is one of the two essential processes during fetal development of the gnathostome skeletal system by which rudimentary bone tissue is created. Intramembranous ossification is an essential process during the natural healing of bone fractures and the rudimentary formation of bones of the head. Unlike endochondral ossification, the other process by which bone tissue is created during fetal development, cartilage is not present during intramembranous ossification. Mesenchymal stem cells within mesenchyme or the medullary cavity of a bone fracture initiate the process of intramembranous ossification. A mesenchymal stem cell, or MSC, is an unspecialized cell. Before it begins to develop, the morphological characteristics of a MSC are: a small cell body with a few cell processes that are long and thin. Furthermore, the mesenchymal stem cells are dispersed within an extracellular matrix, devoid of every type of collagen, except for a few reticular fibrils; the process of intramembranous ossification starts when a small group of adjacent MSCs begin to replicate and form a small, dense cluster of cells, a nidus.
Once a nidus has been formed the MSCs within it stop replicating. At this point, morphological changes in the MSCs begin to occur: the cell body is now larger and rounder. All of the cells within the nidus develop into, display the morphologic characteristics of, an osteoprogenitor cell. At this stage of development, changes in the morphology of the osteoprogenitor cells occur: their shape becomes more columnar and the amount of Golgi apparatus and rough endoplasmic reticulum increases. All of the cells within the nidus develop into, display the morphologic characteristics of, an osteoblast; the osteoblasts create an extracellular matrix containing Type-I collagen fibrils, osteoid. The osteoblasts, while lining the periphery of the nodule, continue to form osteoid in the center of the nidus; some of the osteoblasts become incorporated within the osteoid to become osteocytes. At this point, the osteoid becomes mineralized resulting in a nidus consisting of mineralized osteoid that contains osteocytes and is lined by active osteoblasts.
The nidus, that began as a diffuse collection of MSCs, has become rudimentary bone tissue. The first step in the process is the formation of bone spicules which fuse with each other and become trabeculae; the periosteum is formed and bone growth continues at the surface of trabeculae. Much like spicules, the increasing growth of trabeculae result in interconnection and this network is called woven bone. Woven bone is replaced by lamellar bone. Embryologic mesenchymal cells condense into layers of vascularized primitive connective tissue. Certain mesenchymal cells group together near or around blood vessels, differentiate into osteogenic cells which deposit bone matrix constitutively; these aggregates of bony matrix are called bone spicules. Separate mesenchymal cells differentiate into osteoblasts, which line up along the surface of the spicule and secrete more osteoid, which increases the size of the spicule; as the spicules continue to grow, they fuse with adjacent spicules and this results in the formation of trabeculae.
When osteoblasts become trapped in the matrix they secrete. Osteoblasts continue to line up on the surface; as growth continues, trabeculae become woven bone is formed. The term primary spongiosa is used to refer to the initial trabecular network; the periosteum is formed around the trabeculae by differentiating mesenchymal cells. The primary center of ossification is the area where bone growth occurs between the periosteum and the bone. Osteogenic cells that originate from the periosteum increase appositional growth and a bone collar is formed; the bone collar is mineralized and lamellar bone is formed. Osteons are components or principal structures of compact bone. During the formation of bone spicules, cytoplasmic processes from osteoblasts interconnect; this becomes the canaliculi of osteons. Since bone spicules tend to form around blood vessels, the perivascular space is reduced as the bone continues to grow; when replacement to compact bone occurs, this blood vessel becomes the central canal of the osteon.
Flat bones of the face Bones of the skull Clavicles Endochondral ossification Ossification Martin, RB.
Anatomical terminology is a form of scientific terminology used by anatomists and health professionals such as doctors. Anatomical terminology uses many unique terms and prefixes deriving from Ancient Greek and Latin; these terms can be confusing to those unfamiliar with them, but can be more precise, reducing ambiguity and errors. Since these anatomical terms are not used in everyday conversation, their meanings are less to change, less to be misinterpreted. To illustrate how inexact day-to-day language can be: a scar "above the wrist" could be located on the forearm two or three inches away from the hand or at the base of the hand. By using precise anatomical terminology such ambiguity is eliminated. An international standard for anatomical terminology, Terminologia Anatomica has been created. Anatomical terminology has quite regular morphology, the same prefixes and suffixes are used to add meanings to different roots; the root of a term refers to an organ or tissue. For example, the Latin names of structures such as musculus biceps brachii can be split up and refer to, musculus for muscle, biceps for "two-headed", brachii as in the brachial region of the arm.
The first word describes what is being spoken about, the second describes it, the third points to location. When describing the position of anatomical structures, structures may be described according to the anatomical landmark they are near; these landmarks may include structures, such as the umbilicus or sternum, or anatomical lines, such as the midclavicular line from the centre of the clavicle. The cephalon or cephalic region refers to the head; this area is further differentiated into the cranium, frons, auris, nasus and mentum. The neck area is called cervical region. Examples of structures named according to this include the frontalis muscle, submental lymph nodes, buccal membrane and orbicularis oculi muscle. Sometimes, unique terminology is used to reduce confusion in different parts of the body. For example, different terms are used when it comes to the skull in compliance with its embryonic origin and its tilted position compared to in other animals. Here, Rostral refers to proximity to the front of the nose, is used when describing the skull.
Different terminology is used in the arms, in part to reduce ambiguity as to what the "front", "back", "inner" and "outer" surfaces are. For this reason, the terms below are used: Radial referring to the radius bone, seen laterally in the standard anatomical position. Ulnar referring to the ulna bone, medially positioned when in the standard anatomical position. Other terms are used to describe the movement and actions of the hands and feet, other structures such as the eye. International morphological terminology is used by the colleges of medicine and dentistry and other areas of the health sciences, it facilitates communication and exchanges between scientists from different countries of the world and it is used daily in the fields of research and medical care. The international morphological terminology refers to morphological sciences as a biological sciences' branch. In this field, the form and structure are examined as well as the changes or developments in the organism, it is functional.
It covers the gross anatomy and the microscopic of living beings. It involves the anatomy of the adult, it includes comparative anatomy between different species. The vocabulary is extensive and complex, requires a systematic presentation. Within the international field, a group of experts reviews and discusses the morphological terms of the structures of the human body, forming today's Terminology Committee from the International Federation of Associations of Anatomists, it deals with the anatomical and embryologic terminology. In the Latin American field, there are meetings called Iberian Latin American Symposium Terminology, where a group of experts of the Pan American Association of Anatomy that speak Spanish and Portuguese and studies the international morphological terminology; the current international standard for human anatomical terminology is based on the Terminologia Anatomica. It was developed by the Federative Committee on Anatomical Terminology and the International Federation of Associations of Anatomists and was released in 1998.
It supersedes Nomina Anatomica. Terminologia Anatomica contains terminology for about 7500 human gross anatomical structures. For microanatomy, known as histology, a similar standard exists in Terminologia Histologica, for embryology, the study of development, a standard exists in Terminologia Embryologica; these standards specify accepted names that can be used to refer to histological and embryological structures in journal articles and other areas. As of September 2016, two sections of the Terminologia Anatomica, including central nervous system and peripheral nervous system, were merged to form the Terminologia Neuroanatomica; the Terminologia Anatomica has been perceived with a considerable criticism regarding its content including coverage and spelling mistakes and errors. Anatomical terminology is chosen to highlight the relative location of body structures. For instance, an anatomist might describe one band of tissue as "inferior to" another or a physician might describe a tumor as "superficial to" a deeper body structure.
Anatomical terms used to describe location
Calcium is a chemical element with symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air, its physical and chemical properties are most similar to its heavier homologues strontium and barium. It is the fifth most abundant element in Earth's crust and the third most abundant metal, after iron and aluminium; the most common calcium compound on Earth is calcium carbonate, found in limestone and the fossilised remnants of early sea life. The name derives from Latin calx "lime", obtained from heating limestone; some calcium compounds were known to the ancients, though their chemistry was unknown until the seventeenth century. Pure calcium was isolated in 1808 via electrolysis of its oxide by Humphry Davy, who named the element. Calcium compounds are used in many industries: in foods and pharmaceuticals for calcium supplementation, in the paper industry as bleaches, as components in cement and electrical insulators, in the manufacture of soaps.
On the other hand, the metal in pure form has few applications due to its high reactivity. Calcium is the fifth-most abundant element in the human body; as electrolytes, calcium ions play a vital role in the physiological and biochemical processes of organisms and cells: in signal transduction pathways where they act as a second messenger. Calcium ions outside cells are important for maintaining the potential difference across excitable cell membranes as well as proper bone formation. Calcium is a ductile silvery metal whose properties are similar to the heavier elements in its group, strontium and radium. A calcium atom has twenty electrons, arranged in the electron configuration 4s2. Like the other elements placed in group 2 of the periodic table, calcium has two valence electrons in the outermost s-orbital, which are easily lost in chemical reactions to form a dipositive ion with the stable electron configuration of a noble gas, in this case argon. Hence, calcium is always divalent in its compounds, which are ionic.
Hypothetical univalent salts of calcium would be stable with respect to their elements, but not to disproportionation to the divalent salts and calcium metal, because the enthalpy of formation of MX2 is much higher than those of the hypothetical MX. This occurs because of the much greater lattice energy afforded by the more charged Ca2+ cation compared to the hypothetical Ca+ cation. Calcium, strontium and radium are always considered to be alkaline earth metals. Beryllium and magnesium are different from the other members of the group in their physical and chemical behaviour: they behave more like aluminium and zinc and have some of the weaker metallic character of the post-transition metals, why the traditional definition of the term "alkaline earth metal" excludes them; this classification is obsolete in English-language sources, but is still used in other countries such as Japan. As a result, comparisons with strontium and barium are more germane to calcium chemistry than comparisons with magnesium.
Calcium metal melts at 842 °C and boils at 1494 °C. It crystallises in the face-centered cubic arrangement like strontium, its density of 1.55 g/cm3 is the lowest in its group. Calcium can be cut with a knife with effort. While calcium is a poorer conductor of electricity than copper or aluminium by volume, it is a better conductor by mass than both due to its low density. While calcium is infeasible as a conductor for most terrestrial applications as it reacts with atmospheric oxygen, its use as such in space has been considered; the chemistry of calcium is that of a typical heavy alkaline earth metal. For example, calcium spontaneously reacts with water more than magnesium and less than strontium to produce calcium hydroxide and hydrogen gas, it reacts with the oxygen and nitrogen in the air to form a mixture of calcium oxide and calcium nitride. When finely divided, it spontaneously burns in air to produce the nitride. In bulk, calcium is less reactive: it forms a hydration coating in moist air, but below 30% relative humidity it may be stored indefinitely at room temperature.
Besides the simple oxide CaO, the peroxide CaO2 can be made by direct oxidation of calcium metal under a high pressure of oxygen, there is some evidence for a yellow superoxide Ca2. Calcium hydroxide, Ca2, is a strong base, though it is not as strong as the hydroxides of strontium, barium or the alkali metals. All four dihalides of calcium are known. Calcium carbonate and calcium sulfate are abundant minerals. Like strontium and barium, as well as the alkali metals and the divalent lanthanides europium and ytterbium, calcium metal dissolves directly in liquid ammonia to give a dark blue solution. Due to the large size of the Ca2+ ion, high coordination numbers are common, up to 24 in some intermetallic compounds such as CaZn13. Calcium is complexed by oxygen chelates such as EDTA and polyphosphates, which are useful in an