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
Orthopedic surgery or orthopedics spelled orthopaedics, is the branch of surgery concerned with conditions involving the musculoskeletal system. Orthopedic surgeons use both surgical and nonsurgical means to treat musculoskeletal trauma, spine diseases, sports injuries, degenerative diseases, infections and congenital disorders. Nicholas Andry coined the word in French as orthopédie, derived from the Ancient Greek words ὀρθός orthos and παιδίον paidion, published Orthopedie in 1741; the word was assimilated into English as orthopædics. Though, as the name implies, the discipline was developed with attention to children, the correction of spinal and bone deformities in all stages of life became the cornerstone of orthopedic practice; as with many words derived with the "æ" ligature, simplification to either "ae" or just "e" is common in North America. In the US, the majority of college and residency programs, the American Academy of Orthopaedic Surgeons, still use the spelling with the digraph ae, though hospitals use the shortened form.
Elsewhere, usage is not uniform: in Canada, both spellings are acceptable. Many developments in orthopedic surgery have resulted from experiences during wartime. On the battlefields of the Middle Ages the injured were treated with bandages soaked in horses' blood which dried to form a stiff, but unsanitary, splint; the term orthopedics meant the correcting of musculoskeletal deformities in children. Nicolas Andry, a professor of medicine at the University of Paris coined the term in the first textbook written on the subject in 1741, he advocated the use of exercise and splinting to treat deformities in children. His book was directed towards parents, while some topics would be familiar to orthopedists today, it included'excessive sweating of the palms' and freckles. Jean-André Venel established the first orthopedic institute in 1780, the first hospital dedicated to the treatment of children's skeletal deformities, he developed the club-foot shoe for children born with foot deformities and various methods to treat curvature of the spine.
Advances made in surgical technique during the 18th century, such as John Hunter's research on tendon healing and Percival Pott's work on spinal deformity increased the range of new methods available for effective treatment. Antonius Mathijsen, a Dutch military surgeon, invented the plaster of Paris cast in 1851. However, up until the 1890s, orthopedics was still a study limited to the correction of deformity in children. One of the first surgical procedures developed was percutaneous tenotomy; this involved cutting a tendon the Achilles tendon, to help treat deformities alongside bracing and exercises. In the late 1800s and first decades of the 1900s, there was significant controversy about whether orthopedics should include surgical procedures at all. Examples of people who aided the development of modern orthopedic surgery were Hugh Owen Thomas, a surgeon from Wales, his nephew, Robert Jones. Thomas became interested in orthopedics and bone-setting at a young age and, after establishing his own practice, went on to expand the field into general treatment of fracture and other musculoskeletal problems.
He advocated enforced rest as the best remedy for fractures and tuberculosis and created the so-called'Thomas Splint', to stabilize a fractured femur and prevent infection. He is responsible for numerous other medical innovations that all carry his name:'Thomas's collar' to treat tuberculosis of the cervical spine,'Thomas's manoeuvre', an orthopedic investigation for fracture of the hip joint, Thomas test, a method of detecting hip deformity by having the patient lying flat in bed,'Thomas's wrench' for reducing fractures, as well as an osteoclast to break and reset bones. Thomas's work was not appreciated in his own lifetime, it was only during the First World War that his techniques came to be used for injured soldiers on the battlefield. His nephew, Sir Robert Jones, had made great advances in orthopedics in his position as Surgeon-Superintendent for the construction of the Manchester Ship Canal in 1888, he was responsible for the injured among the 20,000 workers, he organized the first comprehensive accident service in the world, dividing the 36 mile site into 3 sections, establishing a hospital and a string of first aid posts in each section.
He had the medical personnel trained in fracture management. He managed 3,000 cases and performed 300 operations in his own hospital; this position enabled him to improve the standard of fracture management. Physicians from around the world came to Jones’ clinic to learn his techniques. Along with Alfred Tubby, Jones founded the British Orthopaedic Society in 1894. During the First World War, Jones served as a Territorial Army surgeon, he observed that treatment of fractures both at the front and in hospitals at home was inadequate, his efforts led to the introduction of military orthopedic hospitals. He was appointed Inspector of Military Orthopaedics, with responsibility over 30,000 beds; the hospital in Ducane Road, Hammersmith became the model for both British and American military orthopedic hospitals. His advocacy of the use of Thomas splint for the initial treatment of femoral fractures reduced mortality of compound fractures of the femur from 87% to less than 8% in the period from 1916 to 1918.
The use of intramedullary rods to treat fractures of the femur and tibi
Bone density, or bone mineral density, is the amount of bone mineral in bone tissue. The concept is of mass of mineral per volume of bone, although clinically it is measured by proxy according to optical density per square centimetre of bone surface upon imaging. Bone density measurement is used in clinical medicine as an indirect indicator of osteoporosis and fracture risk, it is measured by a procedure called densitometry performed in the radiology or nuclear medicine departments of hospitals or clinics. The measurement involves low radiation exposure. Measurements are most made over the lumbar spine and over the upper part of the hip; the forearm may be scanned if the lumbar spine are not accessible. There is higher probability of fracture. Fractures of the legs and pelvis due to falls are a significant public health problem in elderly women, leading to much medical cost, inability to live independently and risk of death. Bone density measurements are used to screen people for osteoporosis risk and to identify those who might benefit from measures to improve bone strength.
Bone density tests are not necessary for people without risk factors for weak bones. Unnecessary testing is more to result in superfluous treatment rather than discovery of a true problem; the following are risk factors for low bone density and primary considerations for the need for a bone density test. Females age 65 or older males age 70 or older people over age 50 with any of the following: previous bone fracture from minor trauma rheumatoid arthritis low body weight a parent with a hip fracture Individuals with vertebral abnormalities. Individuals receiving, or planning to receive, long-term glucocorticoid therapy. Individuals with primary hyperparathyroidism. Individuals being monitored to assess the response or efficacy of an approved osteoporosis drug therapy. Individuals with a history of eating disordersOther considerations that are related to risk of low bone density and the need for a test include smoking habits, drinking habits, the long-term use of corticosteroid drugs, a vitamin D deficiency.
For those people who do have bone density tests, two conditions which may be detected are osteoporosis and osteopenia. The usual response to either of these indications is consultation with a physician. Results are reported in 3 terms: Measured areal density in g cm−2 Z-score, the number of standard deviations above or below the mean for the patient's age and ethnicity T-score, the number of standard deviations above or below the mean for a healthy 30-year-old adult of the same sex and ethnicity as the patient While there are many different types of BMD tests, all are non-invasive. Most tests differ according to; these tests include: Dual-energy X-ray absorptiometry Dual X-ray Absorptiometry and Laser Quantitative computed tomography Quantitative ultrasound Single photon absorptiometry Dual photon absorptiometry Digital X-ray radiogrammetry Single energy X-ray absorptiometry DXA is the most used, but quantitative ultrasound has been described as a more cost-effective approach to measure bone density.
The DXA test works by measuring a specific bone or bones the spine and wrist. The density of these bones is compared with an average index based on age and size; the resulting comparison is used to determine risk for fractures and the stage of osteoporosis in an individual. Average bone mineral density = BMC / W BMC = bone mineral content = g/cm W = width at the scanned line Results are scored by two measures, the T-score and the Z-score. Scores indicate. Negative scores indicate lower bone density, positive scores indicate higher; the T-score is the relevant measure. It is the bone mineral density at the site, it is a comparison of a patient's BMD to that of a healthy 30-year-old. The US standard is to use data for a 30-year-old of the same sex and ethnicity, but the WHO recommends using data for a 30-year-old white female for everyone. Values for 30-year-olds are used in post-menopausal women and men over age 50 because they better predict risk of future fracture; the criteria of the World Health Organization are: Normal is a T-score of −1.0 or higher Osteopenia is defined as between −1.0 and −2.5 Osteoporosis is defined as −2.5 or lower, meaning a bone density, two and a half standard deviations below the mean of a 30-year-old man/woman.
The Z-score is the comparison to the age-matched normal and is used in cases of severe osteoporosis. This is the number of standard deviations a patient's BMD differs from the average BMD of their age and ethnicity; this value is used in premenopausal women, men under the age of 50, in children. It is most useful. In this setting, it is helpful to scrutinize for coexisting illnesses or treatments that may contribute to osteoporosis such as glucocorticoid therapy, hyperparathyroidism, or alcoholism. Use of BMD has several limitations. Measurement can be affected by the size of the patient, the thickness of tissue overlying the bone, other factors extraneous to the bones. Bone density is a proxy measurement for bone strength, the resistance to fracture and the significant characteristic. Although the two are related, there are some circumstances in which bone density is a poorer indicator of bone strength. Reference standard
Cartilage is a resilient and smooth elastic tissue, a rubber-like padding that covers and protects the ends of long bones at the joints, is a structural component of the rib cage, the ear, the nose, the bronchial tubes, the intervertebral discs, many other body components. It is not as hard and rigid as bone; the matrix of cartilage is made up of glycosaminoglycans, collagen fibers and, elastin. Because of its rigidity, cartilage serves the purpose of holding tubes open in the body. Examples include the rings such as the cricoid cartilage and carina. Cartilage is composed of specialized cells called chondrocytes that produce a large amount of collagenous extracellular matrix, abundant ground substance, rich in proteoglycan and elastin fibers. Cartilage is classified in three types, elastic cartilage, hyaline cartilage and fibrocartilage, which differ in relative amounts of collagen and proteoglycan. Cartilage does not contain blood nerves. Nutrition is supplied to the chondrocytes by diffusion.
The compression of the articular cartilage or flexion of the elastic cartilage generates fluid flow, which assists diffusion of nutrients to the chondrocytes. Compared to other connective tissues, cartilage has a slow turnover of its extracellular matrix and does not repair. In embryogenesis, the skeletal system is derived from the mesoderm germ layer. Chondrification is the process by which cartilage is formed from condensed mesenchyme tissue, which differentiates into chondroblasts and begins secreting the molecules that form the extracellular matrix. Following the initial chondrification that occurs during embryogenesis, cartilage growth consists of the maturing of immature cartilage to a more mature state; the division of cells within cartilage occurs slowly, thus growth in cartilage is not based on an increase in size or mass of the cartilage itself. The articular cartilage function is dependent on the molecular composition of the extracellular matrix; the ECM consists of proteoglycan and collagens.
The main proteoglycan in cartilage is aggrecan, which, as its name suggests, forms large aggregates with hyaluronan. These aggregates hold water in the tissue; the collagen collagen type II, constrains the proteoglycans. The ECM responds to compressive forces that are experienced by the cartilage. Cartilage growth thus refers to the matrix deposition, but can refer to both the growth and remodeling of the extracellular matrix. Due to the great stress on the patellofemoral joint during resisted knee extension, the articular cartilage of the patella is among the thickest in the human body; the mechanical properties of articular cartilage in load-bearing joints such as the knee and hip have been studied extensively at macro and nano-scales. These mechanical properties include the response of cartilage in frictional, compressive and tensile loading. Cartilage displays viscoelastic properties. Lubricin, a glycoprotein abundant in cartilage and synovial fluid, plays a major role in bio-lubrication and wear protection of cartilage.
Cartilage has limited repair capabilities: Because chondrocytes are bound in lacunae, they cannot migrate to damaged areas. Therefore, cartilage damage is difficult to heal; because hyaline cartilage does not have a blood supply, the deposition of new matrix is slow. Damaged hyaline cartilage is replaced by fibrocartilage scar tissue. Over the last years and scientists have elaborated a series of cartilage repair procedures that help to postpone the need for joint replacement. Bioengineering techniques are being developed to generate new cartilage, using a cellular "scaffolding" material and cultured cells to grow artificial cartilage. Several diseases can affect cartilage. Chondrodystrophies are a group of diseases, characterized by the disturbance of growth and subsequent ossification of cartilage; some common diseases that affect the cartilage are listed below. Osteoarthritis: Osteoarthritis is a disease of the whole joint, however one of the most affected tissues is the articular cartilage.
The cartilage covering bones is thinned completely wearing away, resulting in a "bone against bone" within the joint, leading to reduced motion, pain. Osteoarthritis affects the joints exposed to high stress and is therefore considered the result of "wear and tear" rather than a true disease, it is treated by arthroplasty, the replacement of the joint by a synthetic joint made of a stainless steel alloy and ultra high molecular weight polyethylene. Chondroitin sulfate or glucosamine sulfate supplements, have been claimed to reduce the symptoms of osteoarthritis but there is little good evidence to support this claim. Traumatic rupture or detachment: The cartilage in the knee is damaged but can be repaired through knee cartilage replacement therapy; when athletes talk of damaged "cartilage" in their knee, they are referring to a damaged meniscus and not the articular cartilage. Achondroplasia: Reduced proliferation of chondrocytes in the epiphyseal plate of long bones during infancy and childhood, resulting in dwarfism.
Costochondritis: Inflammation of cartilage in the ribs, causing chest pain. Spinal disc herniation: Asymmetrical compression of an intervertebral disc ruptures the sac-like disc, causing a herniation of its soft content; the hernia compresses the adjacent nerves and causes back pain. Relapsing polychondritis: a destruction aut
Hyaline cartilage is the glass-like but translucent cartilage found on many joint surfaces. It is most found in the ribs, nose and trachea. Hyaline cartilage is pearl-grey in color, with a firm consistency and has a considerable amount of collagen, it contains no nerves or blood vessels, its structure is simple. Hyaline cartilage is covered externally by a fibrous membrane known as the perichondrium or, when it's along articulating surfaces, the synovial membrane; this membrane contains vessels. Hyaline cartilage matrix is made of type II collagen and chondroitin sulphate, both of which are found in elastic cartilage. Hyaline cartilage exists on the ventral ends of ribs, in the larynx and bronchi, on the articulating surfaces of bones, it gives the structures a pliable form. The presence of collagen fibres makes such structures and joints strong, but with limited mobility and flexibility. Hyaline cartilage is the most prevalent type of cartilage, it forms the temporary embryonic skeleton, replaced by bone, the skeleton of elasmobranch fish.
When a thin slice of hyaline cartilage is examined under the microscope, it is shown to consist of cells of a rounded or bluntly angular form, lying in groups of two or more in a granular, or homogeneous matrix. When arranged in groups of two or more, the chondrocytes have rounded, but straight outlines, they consist of translucent protoplasm with fine interlacing filaments and minute granules are sometimes present. Embedded in this are one or two round nuclei, having the usual intranuclear network; the cells are contained in cavities in the matrix, called cartilage lacunæ. These cavities are artificial gaps formed from the shrinking of the cells during the staining and setting of the tissue for examination; the inter-territorial space between the isogenous cell groups contains more collagen fibres, allowing it to maintain its shape while the actual cells shrink, creating the lacunae. This constitutes the so-called'capsule' of the space; each lacuna is occupied by a single cell, but during mitosis, it may contain two, four, or eight cells.
Articular cartilage is hyaline cartilage on the articular surfaces of bones, lies inside the joint cavity of synovial joints, bathed in synovial fluid produced by the synovial membrane, which lines the walls of the cavity. Though it is found in close contact with menisci and articular disks, articular cartilage is not considered a part of either of these structures, which are made of fibrocartilage; the biochemical breakdown of the articular cartilage results in osteoarthritis - the most common type of joint disease. Osteoarthritis affects over 30 million individuals in the United States alone, is the leading cause of chronic disability amongst the elderly. Cartilage Hyaline Articular cartilage injuries Articular cartilage damage Articular cartilage repair UIUC Histology Subject 331 Histology image: 03301lba – Histology Learning System at Boston University
Biosynthesis is a multi-step, enzyme-catalyzed process where substrates are converted into more complex products in living organisms. In biosynthesis, simple compounds are modified, converted into other compounds, or joined together to form macromolecules; this process consists of metabolic pathways. Some of these biosynthetic pathways are located within a single cellular organelle, while others involve enzymes that are located within multiple cellular organelles. Examples of these biosynthetic pathways include the production of lipid membrane components and nucleotides. Biosynthesis is synonymous with anabolism; the prerequisite elements for biosynthesis include: precursor compounds, chemical energy, catalytic enzymes which may require coenzymes. These elements create the building blocks for macromolecules; some important biological macromolecules include: proteins, which are composed of amino acid monomers joined via peptide bonds, DNA molecules, which are composed of nucleotides joined via phosphodiester bonds.
Biosynthesis occurs due to a series of chemical reactions. For these reactions to take place, the following elements are necessary: Precursor compounds: these compounds are the starting molecules or substrates in a reaction; these may be viewed as the reactants in a given chemical process. Chemical energy: chemical energy can be found in the form of high energy molecules; these molecules are required for energetically unfavorable reactions. Furthermore, the hydrolysis of these compounds drives a reaction forward. High energy molecules, such as ATP, have three phosphates; the terminal phosphate is split off during hydrolysis and transferred to another molecule. Catalytic enzymes: these molecules are special proteins that catalyze a reaction by increasing the rate of the reaction and lowering the activation energy. Coenzymes or cofactors: cofactors are molecules that assist in chemical reactions; these may be metal ions, vitamin derivatives such as NADH and acetyl CoA, or non-vitamin derivatives such as ATP.
In the case of NADH, the molecule transfers a hydrogen, whereas acetyl CoA transfers an acetyl group, ATP transfers a phosphate. In the simplest sense, the reactions that occur in biosynthesis have the following format: Reactant → e n z y m e Product Some variations of this basic equation which will be discussed in more detail are: Simple compounds which are converted into other compounds as part of a multiple step reaction pathway. Two examples of this type of reaction occur during the formation of nucleic acids and the charging of tRNA prior to translation. For some of these steps, chemical energy is required: Precursor molecule + ATP ↽ − − ⇀ product AMP + PP i Simple compounds that are converted into other compounds with the assistance of cofactors. For example, the synthesis of phospholipids requires acetyl CoA, while the synthesis of another membrane component, requires NADH and FADH for the formation the sphingosine backbone; the general equation for these examples is: Precursor molecule + Cofactor → e n z y m e macromolecule Simple compounds that join together to create a macromolecule.
For example, fatty acids join together to form phospholipids. In turn and cholesterol interact noncovalently in order to form the lipid bilayer; this reaction may be depicted as follows: Molecule 1 + Molecule 2 ⟶ macromolecule Many intricate macromolecules are synthesized in a pattern of simple, repeated structures. For example, the simplest structures of lipids are fatty acids. Fatty acids are hydrocarbon derivatives; these fatty acids create larger components, which in turn incorporate noncovalent interactions to form the lipid bilayer. Fatty acid chains are found in two major components of membrane lipids: phospholipids and sphingolipids. A third major membrane component, does not contain these fatty acid units; the foundation of all biomembranes consists of a bilayer structure of phospholipids. The phospholipid molecule is amphipathic; the phospholipid heads interact with each other and aqueous media, while the hydrocarbon tails orient themselves in the center, away from water. These latter interactions drive the bilayer structure that acts as a barrier for molecules.
There are various types of phospholipids. However, the first step in phospholipid synthesis involves the formation of phosphatidate or diacylglycerol 3-phosphate at the endoplasmic reticulum and outer mitochondrial membrane; the synthesis pathway is found below: The pathway starts with glycerol 3-phosphate, which gets converted to lysophosphatidate via the addition of a fatty acid chain provided by acyl coenzyme A. Then, lysophosphatidate is converted to phosphatidate via the addition of another fatty acid chain contributed by a second acyl CoA.
Polysaccharides are polymeric carbohydrate molecules composed of long chains of monosaccharide units bound together by glycosidic linkages, on hydrolysis give the constituent monosaccharides or oligosaccharides. They range in structure from linear to branched. Examples include storage polysaccharides such as starch and glycogen, structural polysaccharides such as cellulose and chitin. Polysaccharides are quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure, these macromolecules can have distinct properties from their monosaccharide building blocks, they may be amorphous or insoluble in water. When all the monosaccharides in a polysaccharide are the same type, the polysaccharide is called a homopolysaccharide or homoglycan, but when more than one type of monosaccharide is present they are called heteropolysaccharides or heteroglycans. Natural saccharides are of simple carbohydrates called monosaccharides with general formula n where n is three or more.
Examples of monosaccharides are glucose and glyceraldehyde. Polysaccharides, have a general formula of Cxy where x is a large number between 200 and 2500; when the repeating units in the polymer backbone are six-carbon monosaccharides, as is the case, the general formula simplifies to n, where 40≤n≤3000. As a rule of thumb, polysaccharides contain more than ten monosaccharide units, whereas oligosaccharides contain three to ten monosaccharide units. Polysaccharides are an important class of biological polymers, their function in living organisms is either structure- or storage-related. Starch is used as a storage polysaccharide in plants, being found in the form of both amylose and the branched amylopectin. In animals, the structurally similar glucose polymer is the more densely branched glycogen, sometimes called "animal starch". Glycogen's properties allow it to be metabolized more which suits the active lives of moving animals. Cellulose and chitin are examples of structural polysaccharides.
Cellulose is used in the cell walls of plants and other organisms, is said to be the most abundant organic molecule on Earth. It has many uses such as a significant role in the paper and textile industries, is used as a feedstock for the production of rayon, cellulose acetate and nitrocellulose. Chitin has nitrogen-containing side branches, increasing its strength, it is found in the cell walls of some fungi. It has multiple uses, including surgical threads. Polysaccharides include callose or laminarin, xylan, mannan and galactomannan. Nutrition polysaccharides are common sources of energy. Many organisms can break down starches into glucose; these carbohydrate types can be metabolized by some protists. Ruminants and termites, for example, use microorganisms to process cellulose. Though these complex polysaccharides are not digestible, they provide important dietary elements for humans. Called dietary fiber, these carbohydrates enhance digestion among other benefits; the main action of dietary fiber is to change the nature of the contents of the gastrointestinal tract, to change how other nutrients and chemicals are absorbed.
Soluble fiber binds to bile acids in the small intestine, making them less to enter the body. Soluble fiber attenuates the absorption of sugar, reduces sugar response after eating, normalizes blood lipid levels and, once fermented in the colon, produces short-chain fatty acids as byproducts with wide-ranging physiological activities. Although insoluble fiber is associated with reduced diabetes risk, the mechanism by which this occurs is unknown. Not yet formally proposed as an essential macronutrient, dietary fiber is regarded as important for the diet, with regulatory authorities in many developed countries recommending increases in fiber intake. Starch is a glucose polymer, it is made up of a mixture of amylopectin. Amylose consists of a linear chain of several hundred glucose molecules and Amylopectin is a branched molecule made of several thousand glucose units. Starches are insoluble in water, they can be digested by breaking the alpha-linkages. Both humans and other animals have amylases, so they can digest starches.
Potato, rice and maize are major sources of starch in the human diet. The formations of starches are the ways. Glycogen serves as the secondary long-term energy storage in animal and fungal cells, with the primary energy stores being held in adipose tissue. Glycogen is made by the liver and the muscles, but can be made by glycogenesis within the brain and stomach. Glycogen is analogous to starch, a glucose polymer in plants, is sometimes referred to as animal starch, having a similar structure to amylopectin but more extensively branched and compact than starch. Glycogen is a polymer of α glycosidic bonds linked, with α-linked branches. Glycogen is found in the form of granules in the cytosol/cytoplasm in many cell types, plays an important role in the glucose cycle. Glycogen forms an energy reserve that can be mobilized to meet a sudden need for glucose, but one, less compact and more available a