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Monday, 24 September 2012
DNA FINGERPRINTING
DNA profiling (also called DNA testing, DNA typing, or genetic fingerprinting) is a technique employed by forensic scientists to assist in the identification of individuals by their respective DNA profiles. DNA profiles
are encrypted sets of numbers that reflect a person's DNA makeup, which can also be used as the person's identifier. DNA profiling should not be confused with full genome sequencing.It is used in, for example, parental testing and criminal investigation.
Although 99.9% of human DNA sequences are the same in every person, enough of the DNA is different to distinguish one individual from another, unless they are monozygotic twins.
DNA profiling uses repetitive ("repeat") sequences that are highly variable,called variable number tandem repeats (VNTRs), particularly short tandem repeats (STRs). VNTR loci are very similar between closely related humans, but so variable that unrelated individuals are extremely unlikely to have the same VNTRs.
"The DNA profiling technique was first reported in 1984" by Sir Alec Jeffreys at the University of Leicester in England,and is now the basis of several national DNA databases. Dr. Jeffreys's genetic fingerprinting was made commercially available in 1987, when a chemical company, Imperial Chemical Industries (ICI), started a blood-testing centre in England.
Although 99.9% of human DNA sequences are the same in every person, enough of the DNA is different to distinguish one individual from another, unless they are monozygotic twins.
DNA profiling uses repetitive ("repeat") sequences that are highly variable,called variable number tandem repeats (VNTRs), particularly short tandem repeats (STRs). VNTR loci are very similar between closely related humans, but so variable that unrelated individuals are extremely unlikely to have the same VNTRs.
"The DNA profiling technique was first reported in 1984" by Sir Alec Jeffreys at the University of Leicester in England,and is now the basis of several national DNA databases. Dr. Jeffreys's genetic fingerprinting was made commercially available in 1987, when a chemical company, Imperial Chemical Industries (ICI), started a blood-testing centre in England.
RNA
Ribonucleic acid is part of a group of molecules known as the nucleic acids, which are one of the four major macromolecules (along with lipids, carbohydrates and proteins) essential f
or all known forms of life. Like DNA, RNA is made up of a long chain of components called nucleotides. Each nucleotide consists of a nucleobase, a ribose sugar, and a phosphate group. The sequence of nucleotides allows RNA to encode genetic information. All cellular organisms use messenger RNA (mRNA) to carry the genetic information that directs the synthesis of proteins. In addition, many viruses use RNA instead of DNA as their genetic material.
Some RNA molecules play an active role in cells by catalyzing biological reactions, controlling gene expression, or sensing and communicating responses to cellular signals. One of these active processes is protein synthesis, a universal function whereby mRNA molecules direct the assembly of proteins on ribosomes. This process uses transfer RNA (tRNA) molecules to deliver amino acids to the ribosome, where ribosomal RNA (rRNA) links amino acids together to form proteins.
The chemical structure of RNA is very similar to that of DNA, with two differences: (a) RNA contains the sugar ribose, while DNA contains the slightly different sugar deoxyribose (a type of ribose that lacks one oxygen atom), and (b) RNA has the nucleobase uracil while DNA contains thymine. Unlike DNA, most RNA molecules are single-stranded and can adopt very complex three-dimensional structure.
Some RNA molecules play an active role in cells by catalyzing biological reactions, controlling gene expression, or sensing and communicating responses to cellular signals. One of these active processes is protein synthesis, a universal function whereby mRNA molecules direct the assembly of proteins on ribosomes. This process uses transfer RNA (tRNA) molecules to deliver amino acids to the ribosome, where ribosomal RNA (rRNA) links amino acids together to form proteins.
The chemical structure of RNA is very similar to that of DNA, with two differences: (a) RNA contains the sugar ribose, while DNA contains the slightly different sugar deoxyribose (a type of ribose that lacks one oxygen atom), and (b) RNA has the nucleobase uracil while DNA contains thymine. Unlike DNA, most RNA molecules are single-stranded and can adopt very complex three-dimensional structure.
DNA
Deoxyribonucleic acid (DNA) is a nucleic acid containing the genetic instructions used in the development and functioning of all known living organisms (with the exception of RNA viruses).
The DNA segments carrying this genetic information are called genes. Likewise, other DNA sequences have structural purposes, or are involved in regulating the use of this genetic information. Along with RNA and proteins, DNA is one of the three major macromolecules that are essential for all known forms of life.
DNA consists of two long polymers of simple units called nucleotides, with backbones made of sugars and phosphate groups joined by ester bonds. These two strands run in opposite directions to each other and are therefore anti-parallel, one backbone being 3' (three prime) and the other 5' (five prime). This refers to the direction the 3rd and 5th carbon on the sugar molecule is facing. Attached to each sugar is one of four types of molecules called nucleobases (informally, bases). It is the sequence of these four nucleobases along the backbone that encodes information. This information is read using the genetic code, which specifies the sequence of the amino acids within proteins. The code is read by copying stretches of DNA into the related nucleic acid RNA in a process called transcription.
Within cells, DNA is organized into long structures called chromosomes. During cell division these chromosomes are duplicated in the process of DNA replication, providing each cell its own complete set of chromosomes. Eukaryotic organisms (animals, plants, fungi, and protists) store most of their DNA inside the cell nucleus and some of their DNA in organelles, such as mitochondria or chloroplasts.
In contrast, prokaryotes (bacteria and archaea) store their DNA only in the cytoplasm. Within the chromosomes, chromatin proteins such as histones compact and organize DNA. These compact structures guide the interactions between DNA and other proteins, helping control which parts of the DNA are transcribed.
DNA consists of two long polymers of simple units called nucleotides, with backbones made of sugars and phosphate groups joined by ester bonds. These two strands run in opposite directions to each other and are therefore anti-parallel, one backbone being 3' (three prime) and the other 5' (five prime). This refers to the direction the 3rd and 5th carbon on the sugar molecule is facing. Attached to each sugar is one of four types of molecules called nucleobases (informally, bases). It is the sequence of these four nucleobases along the backbone that encodes information. This information is read using the genetic code, which specifies the sequence of the amino acids within proteins. The code is read by copying stretches of DNA into the related nucleic acid RNA in a process called transcription.
Within cells, DNA is organized into long structures called chromosomes. During cell division these chromosomes are duplicated in the process of DNA replication, providing each cell its own complete set of chromosomes. Eukaryotic organisms (animals, plants, fungi, and protists) store most of their DNA inside the cell nucleus and some of their DNA in organelles, such as mitochondria or chloroplasts.
In contrast, prokaryotes (bacteria and archaea) store their DNA only in the cytoplasm. Within the chromosomes, chromatin proteins such as histones compact and organize DNA. These compact structures guide the interactions between DNA and other proteins, helping control which parts of the DNA are transcribed.
FORENSIC SCIENCE
Forensic science :
It is the application of a broad spectrum of sciences to answer questions of interest to a legal system. This may be in relation to a crime or a civil action.
The word forensic comes from the Latin forēnsis, meaning of or before the forum
The word forensic comes from the Latin forēnsis, meaning of or before the forum
Saturday, 21 July 2012
CELL
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life
[1] Organisms can be classified as unicellular (consisting of a single cell; including mostbacteria) or multicellular (including plants and animals). Humans contain about 10 trillion(1013) cells. Most plant and animal cells are between 1 and 100 µm and therefore are visible only under the microscope.
[2]The cell was discovered by Robert Hooke in 1665. In 1835, before the final cell theory was developed, Jan Evangelista Purkyně observed small "granules" while looking at the plant tissue through a microscope. The cell theory, first developed in 1839 by Matthias Jacob Schleiden and Theodor Schwann, states that all organisms are composed of one or more cells, that all cells come from preexisting cells, that vital functions of an organism occur within cells, and that all cells contain the hereditary information necessary for regulating cell functions and for transmitting information to the next generation of cells
.[3]The word cell comes from the Latin cella, meaning "small room". The descriptive term for the smallest living biological structure was coined by Robert Hooke in a book he published in 1665 when he compared the cork cells he saw through his microscope to the small rooms monks lived in.
Anatomy
There are two types of cells: eukaryotic and prokaryotic. Prokaryotic cells are usually independent, while eukaryotic cells are often found in multicellular organisms.
Prokaryotic cells
Main article: Prokaryote
The prokaryote cell is simpler, and therefore smaller, than a eukaryote cell, lacking a nucleus and most of the other organelles of eukaryotes. There are two kinds of prokaryotes: bacteria and archaea; these share a similar structure.
Nuclear material of prokaryotic cell consist of a single chromosome that is in direct contact with cytoplasm. Here, the undefined nuclear region in the cytoplasm is called nucleoid.
A prokaryotic cell has three architectural regions:
- On the outside, flagella and pili project from the cell's surface. These are structures (not present in all prokaryotes) made of proteins that facilitate movement and communication between cells;
- Enclosing the cell is the cell envelope – generally consisting of a cell wallcovering a plasma membrane though some bacteria also have a further covering layer called a capsule. The envelope gives rigidity to the cell and separates the interior of the cell from its environment, serving as a protective filter. Though most prokaryotes have a cell wall, there are exceptions such as Mycoplasma(bacteria) and Thermoplasma (archaea). The cell wall consists of peptidoglycanin bacteria, and acts as an additional barrier against exterior forces. It also prevents the cell from expanding and finally bursting (cytolysis) from osmotic pressure against a hypotonic environment. Some eukaryote cells (plant cellsand fungi cells) also have a cell wall;
- Inside the cell is the cytoplasmic region that contains the cell genome (DNA) and ribosomes and various sorts of inclusions. A prokaryotic chromosome is usually a circular molecule (an exception is that of the bacterium Borrelia burgdorferi, which causes Lyme disease). Though not forming a nucleus, theDNA is condensed in a nucleoid. Prokaryotes can carry extrachromosomal DNA elements called plasmids, which are usually circular. Plasmids enable additional functions, such as antibiotic resistance.
Eukaryotic cells
Main article: Eukaryote
Plants, animals, fungi, slime moulds, protozoa, and algae are all eukaryotic. These cells are about 15 times wider than a typical prokaryote and can be as much as 1000 times greater in volume. The major difference between prokaryotes and eukaryotes is that eukaryotic cells contain membrane-bound compartments in which specific metabolic activities take place. Most important among these is a cell nucleus, a membrane-delineated compartment that houses the eukaryotic cell's DNA. This nucleus gives the eukaryote its name, which means "true nucleus." Other differences include:
- The plasma membrane resembles that of prokaryotes in function, with minor differences in the setup. Cell walls may or may not be present.
- The eukaryotic DNA is organized in one or more linear molecules, called chromosomes, which are associated with histone proteins. All chromosomal DNA is stored in the cell nucleus, separated from the cytoplasm by a membrane. Some eukaryotic organelles such as mitochondria also contain some DNA.
- Many eukaryotic cells are ciliated with primary cilia. Primary cilia play important roles in chemosensation, mechanosensation, and thermosensation. Cilia may thus be "viewed as sensory cellular antennae that coordinate a large number of cellular signaling pathways, sometimes coupling the signaling to ciliary motility or alternatively to cell division and differentiation."
- Eukaryotes can move using motile cilia or flagella. The flagella are more complex than those of prokaryotes.
Sunday, 15 April 2012
Human nose
The visible part of the human nose is the protruding part of the face that bears the nostrils .
The shape of the nose is determined by the ethmoid bone and the nasal septum , which consists mostly of cartilage and which separates the nostrils. On average the nose of a male is larger than that of a female .
The nose has an area of specialised cells which are responsible for smelling (part of the olfactory system ). Another function of the nose is the conditioning of inhaled air, warming it and making it more humid. Hairs inside the nose prevent large particles from entering the lungs. Sneezing is usually caused by foreign particlesirritating the nasal mucosa, but can more rarely be caused by sudden exposure to bright light (called the photic sneeze reflex ) or touching the external auditory canal . Sneezing is a means of transmitting infections because it creates aerosols in which the droplets can harbour microbes.
The shape of the nose is determined by the ethmoid bone and the nasal septum , which consists mostly of cartilage and which separates the nostrils. On average the nose of a male is larger than that of a female .
The nose has an area of specialised cells which are responsible for smelling (part of the olfactory system ). Another function of the nose is the conditioning of inhaled air, warming it and making it more humid. Hairs inside the nose prevent large particles from entering the lungs. Sneezing is usually caused by foreign particlesirritating the nasal mucosa, but can more rarely be caused by sudden exposure to bright light (called the photic sneeze reflex ) or touching the external auditory canal . Sneezing is a means of transmitting infections because it creates aerosols in which the droplets can harbour microbes.
Human ear
The ear is the organ that detects sound . It not only receives sound,but also aids in balance and body position. The ear is part of the auditory system .
The word "ear" may be used correctly to describe the entire organ or just the visible portion. In most mammals, the visible ear is a flap of tissue that is also calledthe pinna and is the first of many steps in hearing . In humans, the pinna is often called the auricle . Vertebrates have a pair of ears, placed somewhat symmetrically on opposite sides of the head. This arrangement aids in the ability to localize sound sources.
The word "ear" may be used correctly to describe the entire organ or just the visible portion. In most mammals, the visible ear is a flap of tissue that is also calledthe pinna and is the first of many steps in hearing . In humans, the pinna is often called the auricle . Vertebrates have a pair of ears, placed somewhat symmetrically on opposite sides of the head. This arrangement aids in the ability to localize sound sources.
Our Teeth
Teeth (singular tooth ) are small, calcified , whitish structures found in the jaws ( Mouths ) of many vertebrates that are used to breakdown food .
Some animals, particularly carnivores , also use teeth for hunting or for defensive purposes. The roots of teeth are embedded in the maxilla (upper jaw) or the mandible (lower jaw) and are covered by gums . Teeth are made of multiple tissues of varying density and hardness.
Teeth are among the most distinctive (and long-lasting) features of mammal species. Paleontologists use teeth to identify fossil species and determine their relationships. The shape of an animal 's teeth is related to its diet.
For example, plant matter is hard to digest, so herbivores have many molars for chewing and grinding. Carnivores , on the other hand, need canines to kill prey and to tear meat.
Mammals are diphyodont , meaning that they develop two sets of teeth. In humans , the first set (also called the "baby", "milk","primary", and " deciduous " set) Normally starts to appear at about six months of age, although somebabies are born with one or more visible teeth, known as "Neonatal teeth."
Normal tooth eruption at about six months is known as Teething and can be painful.
Some animals develop only one set of teeth (Monophyodont) while others develop many sets (polyphyodont). Sharks ,
For example, Grow a new set of teeth every two weeks to replace worn teeth. Rodent incisors grow and wear away continually through gnawing, which helps maintain relatively constant length. The industry of the beaver is due in part to this qualification. Many rodents such as voles (but not mice ) and guinea pigs , as well as rabbits , have continuously growing molars in addition to incisors.
Dental trauma refers to trauma to the face, mouth, and especially the teeth lips and periodontium. The study of dental trauma is called "Dental traumatology".
Some animals, particularly carnivores , also use teeth for hunting or for defensive purposes. The roots of teeth are embedded in the maxilla (upper jaw) or the mandible (lower jaw) and are covered by gums . Teeth are made of multiple tissues of varying density and hardness.
Teeth are among the most distinctive (and long-lasting) features of mammal species. Paleontologists use teeth to identify fossil species and determine their relationships. The shape of an animal 's teeth is related to its diet.
For example, plant matter is hard to digest, so herbivores have many molars for chewing and grinding. Carnivores , on the other hand, need canines to kill prey and to tear meat.
Mammals are diphyodont , meaning that they develop two sets of teeth. In humans , the first set (also called the "baby", "milk","primary", and " deciduous " set) Normally starts to appear at about six months of age, although somebabies are born with one or more visible teeth, known as "Neonatal teeth."
Normal tooth eruption at about six months is known as Teething and can be painful.
Some animals develop only one set of teeth (Monophyodont) while others develop many sets (polyphyodont). Sharks ,
For example, Grow a new set of teeth every two weeks to replace worn teeth. Rodent incisors grow and wear away continually through gnawing, which helps maintain relatively constant length. The industry of the beaver is due in part to this qualification. Many rodents such as voles (but not mice ) and guinea pigs , as well as rabbits , have continuously growing molars in addition to incisors.
Dental trauma refers to trauma to the face, mouth, and especially the teeth lips and periodontium. The study of dental trauma is called "Dental traumatology".
A human tongue
The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates whichmanipulates food for mastication . It is the primary organ of taste ( gustation ), as much of the upper surface of the tongue is covered in papillae and taste buds . It is sensitive and kept moist by saliva , and is richly supplied with nerves and blood vessels . In humans a secondary function of the tongue is phonetic articulation.
[ 1 ] The tongue also serves as a natural means of cleaning one's teeth.
[ 2 ] The ability to perceive different tastes is not localised in different parts of the tongue, as is widely believed.
[ 3 ] This error arose because of misinterpretation of some 19th century research
[ 1 ] The tongue also serves as a natural means of cleaning one's teeth.
[ 2 ] The ability to perceive different tastes is not localised in different parts of the tongue, as is widely believed.
[ 3 ] This error arose because of misinterpretation of some 19th century research
Friday, 6 April 2012
Endocrine glands
Endocrine glands are glands of the endocrine system that secrete their products, hormones , directlyinto the blood rather than through a duct. The main endocrine glands include the pituitary gland , pancreas , ovaries , testes , thyroid gland , and adrenal glands . The hypothalamus is a neuroendocrine organ. Other organs which are not so well known for their endocrine activityinclude the stomach , which produces such hormones as ghrelin .
Local chemical messengers, not generally considered part of the endocrine system, include autocrines , which act on the cells that secrete them, and paracrines , which act on a different cell typenearby.
The ability of a target cell to respond to a hormone depends on the presence of receptors, within the cell or on its plasma membrane, to which the hormonecan bind.
Hormone receptors are dynamic structures. Changes in number and sensitivity of hormone receptors may occur in response to high or low levels of stimulating hormones.
Blood levels of hormones reflect a balance between secretion and degradation/ excretion . The liver and kidneys are the major organs that degrade hormones; breakdown products are excretedin urine and feces.
Hormone half-life and duration of activity are limited and vary from hormone to hormone.
Local chemical messengers, not generally considered part of the endocrine system, include autocrines , which act on the cells that secrete them, and paracrines , which act on a different cell typenearby.
The ability of a target cell to respond to a hormone depends on the presence of receptors, within the cell or on its plasma membrane, to which the hormonecan bind.
Hormone receptors are dynamic structures. Changes in number and sensitivity of hormone receptors may occur in response to high or low levels of stimulating hormones.
Blood levels of hormones reflect a balance between secretion and degradation/ excretion . The liver and kidneys are the major organs that degrade hormones; breakdown products are excretedin urine and feces.
Hormone half-life and duration of activity are limited and vary from hormone to hormone.
Sunday, 4 March 2012
Human skeleton »»
The human skeleton consists ofboth fused and individual bones supported and supplemented by ligaments , tendons , muscles and cartilage . It serves as a scaffold which supports organs, anchorsmuscles, and protects organs such as the brain , lungs and heart . [ citation needed ]
The biggest bone in the body is the femur in the thigh and the smallest is the stapes bone in the middle ear . Several factors contribute to the bone density and average mass of the human skeleton including; gender, race, hormonal factors, nutrition, physical activity and lifestyle behaviors.
[ 1 ] Because of these and other factors affecting an individual's weight the human skeleton may comprise between 12 and 20 percent of a person's total body weight with the average being 15 percent.
[ 2 ] Fused bones include those of the pelvis and the cranium . Not all bones are interconnected directly: there are three bones ineach middle ear called the ossicles that articulate only with each other. The hyoid bone , which is located in the neck and serves as the point of attachment for the tongue , does not articulate with any other bones in the body, being supported by muscles and ligaments.
The biggest bone in the body is the femur in the thigh and the smallest is the stapes bone in the middle ear . Several factors contribute to the bone density and average mass of the human skeleton including; gender, race, hormonal factors, nutrition, physical activity and lifestyle behaviors.
[ 1 ] Because of these and other factors affecting an individual's weight the human skeleton may comprise between 12 and 20 percent of a person's total body weight with the average being 15 percent.
[ 2 ] Fused bones include those of the pelvis and the cranium . Not all bones are interconnected directly: there are three bones ineach middle ear called the ossicles that articulate only with each other. The hyoid bone , which is located in the neck and serves as the point of attachment for the tongue , does not articulate with any other bones in the body, being supported by muscles and ligaments.
Immune system »»
An immune system is a system of biological structures and processes within an organism that protects against disease . In order to function properly, an immune system must detect a wide variety of agents, from viruses to parasitic worms , and distinguish them from the organism's own healthy tissue .
Pathogens can rapidly evolve and adapt to avoid detection and destruction by the immune system. As a result, multiple defense mechanisms have also evolved to recognize and neutralize pathogens. Even simple unicellular organisms such as bacteria possess a rudimentary immune system, in the form of enzymes which protect against bacteriophage infections. Other basic immune mechanisms evolved in ancient eukaryotes and remain in their modern descendants, such as plants and insects. These mechanisms include phagocytosis , antimicrobial peptides called defensins , and the complement system . Jawed vertebrates , including humans, have even more sophisticated defense mechanisms, [ 1 ] including the ability to adapt over time to recognize specific pathogens more efficiently. Adaptive (or acquired) immunity creates immunological memory after an initial response to a specific pathogen, leading to an enhanced response to subsequent encounters with that same pathogen. This process of acquired immunity is the basis of vaccination .
Disorders of the immune system can result in autoimmune diseases , inflammatory diseases and cancer . [ 2 ] [ 3 ] Immunodeficiency occur when the immune system is less active than normal, resulting in recurring and life-threatening infections. In humans, immunodeficiency can either be the result of a genetic disease , such as severe combined immunodeficiency , or acquired conditions such as HIV / AIDS or the use of immunosuppressive medication. In contrast, autoimmunity result from a hyperactive immune system attacking normal tissues as if they were foreign organisms. Common autoimmune diseases include Hashimoto's thyroiditis , rheumatoid arthritis , diabetes mellitus type 1 , and systemic lupus erythematosus . Immunology covers the study of all aspects of the immune system.
Pathogens can rapidly evolve and adapt to avoid detection and destruction by the immune system. As a result, multiple defense mechanisms have also evolved to recognize and neutralize pathogens. Even simple unicellular organisms such as bacteria possess a rudimentary immune system, in the form of enzymes which protect against bacteriophage infections. Other basic immune mechanisms evolved in ancient eukaryotes and remain in their modern descendants, such as plants and insects. These mechanisms include phagocytosis , antimicrobial peptides called defensins , and the complement system . Jawed vertebrates , including humans, have even more sophisticated defense mechanisms, [ 1 ] including the ability to adapt over time to recognize specific pathogens more efficiently. Adaptive (or acquired) immunity creates immunological memory after an initial response to a specific pathogen, leading to an enhanced response to subsequent encounters with that same pathogen. This process of acquired immunity is the basis of vaccination .
Disorders of the immune system can result in autoimmune diseases , inflammatory diseases and cancer . [ 2 ] [ 3 ] Immunodeficiency occur when the immune system is less active than normal, resulting in recurring and life-threatening infections. In humans, immunodeficiency can either be the result of a genetic disease , such as severe combined immunodeficiency , or acquired conditions such as HIV / AIDS or the use of immunosuppressive medication. In contrast, autoimmunity result from a hyperactive immune system attacking normal tissues as if they were foreign organisms. Common autoimmune diseases include Hashimoto's thyroiditis , rheumatoid arthritis , diabetes mellitus type 1 , and systemic lupus erythematosus . Immunology covers the study of all aspects of the immune system.
Bone Marrow
Bone marrow ( Latin : medulla ossium ) is the flexible tissue found in the interior of bones . In humans , bone marrow in large bones produces new blood cells . On average, bone marrow constitutes 4% of the total body mass of humans; in adults weighing 65 kg (143 lbs), bone marrow accounts for approximately 2.6 kg (5.7 lbs). The hematopoietic compartment of bone marrow produces approximately 500 billion blood cells per day, which use the bone marrow vasculature as a conduit to the body's systemic circulation.
[ 1 ] Bone marrow is also a key component of the lymphatic system , producing the lymphocytes that support the body's immune system .
[ 1 ] Bone marrow is also a key component of the lymphatic system , producing the lymphocytes that support the body's immune system .
Saturday, 3 March 2012
Semen (disambiguation)
Semen is an organic fluid , also known as seminal fluid , that maycontain spermatozoa . It is secreted by the gonads (sexual glands) and other sexual organs of male or hermaphroditic animals and can fertilize female ova . In humans, seminal fluid contains several components besides spermatozoa: proteolytic and other enzymes as well as fructose are elements of seminal fluid which promote the survival of spermatozoa and provide a medium through which they can move or "swim".
Semen is produced and originates from the seminal vesicle , which is located in the pelvis. The process that results inthe discharge of semen is called "Ejaculation".
Semen is produced and originates from the seminal vesicle , which is located in the pelvis. The process that results inthe discharge of semen is called "Ejaculation".
Smoking Damages DNA Within Minutes, Research Shows {{ HealthDay News ( 15 jan ) }}
Cigarettes start to destroy a smoker's DNA within minutes of inhaling, new researchindicates, suggesting that the habit causes immediate genetic damage and quickly raises the short-term risk for cancer.
"The results reported here should serve as a stark warning to those who are considering starting to smoke cigarettes," lead study author Stephen S. Hecht, from the Masonic Cancer Center and department of pharmacology at the University of Minnesota in Minneapolis, said in a news release from the American Chemical Society.
Hecht and his colleagues reportedtheir observations in the current issue of the journal Chemical Research in Toxicology .
In their research, the investigatorsfocused on a class of cancer-causing culprits found in cigarettesmoke called polycyclic aromatic hydrocarbons, or PAHs.
PAHs are known to inflict damage on DNA and are therefore thoughtto play a large role in the onset of lung cancer, a disease that the researchers pointed out has been linked to the loss of 3,000 lives a day worldwide, mostly as a consequence of smoking.
To date, however, little had been known about the exact mechanism by which PAH exposure causes disease.
To better understand the risks, Hecht's team conducted what they called a "unique" analysis, by labeling and tracking a single PAH -- phenanthrene -- through the bodies of 12 volunteer smokers.
The study authors noted that this approach was "the first to investigate human metabolism of a PAH specifically delivered by inhalation in cigarette smoke, without interference by other sources of exposure such as air pollution or the diet."
The results: having rapidly transformed in the body into a known toxin, the PAH in question began to cause havoc on the DNA of the smokers within just 15 to 30 minutes after smoking.
The velocity of the cancer-causing process surprised the research team. They said the speed with which the potentially lethal DNA assault began was comparable to having injected the PAH directly into an individual's bloodstream.
"The results reported here should serve as a stark warning to those who are considering starting to smoke cigarettes," lead study author Stephen S. Hecht, from the Masonic Cancer Center and department of pharmacology at the University of Minnesota in Minneapolis, said in a news release from the American Chemical Society.
Hecht and his colleagues reportedtheir observations in the current issue of the journal Chemical Research in Toxicology .
In their research, the investigatorsfocused on a class of cancer-causing culprits found in cigarettesmoke called polycyclic aromatic hydrocarbons, or PAHs.
PAHs are known to inflict damage on DNA and are therefore thoughtto play a large role in the onset of lung cancer, a disease that the researchers pointed out has been linked to the loss of 3,000 lives a day worldwide, mostly as a consequence of smoking.
To date, however, little had been known about the exact mechanism by which PAH exposure causes disease.
To better understand the risks, Hecht's team conducted what they called a "unique" analysis, by labeling and tracking a single PAH -- phenanthrene -- through the bodies of 12 volunteer smokers.
The study authors noted that this approach was "the first to investigate human metabolism of a PAH specifically delivered by inhalation in cigarette smoke, without interference by other sources of exposure such as air pollution or the diet."
The results: having rapidly transformed in the body into a known toxin, the PAH in question began to cause havoc on the DNA of the smokers within just 15 to 30 minutes after smoking.
The velocity of the cancer-causing process surprised the research team. They said the speed with which the potentially lethal DNA assault began was comparable to having injected the PAH directly into an individual's bloodstream.
Menstrual cycle
The Menstrual cycle is the scientific term for the physiological changes that can occur in fertile women for the purpose of sexual reproduction and fertilization .
This article focuses on the human menstrualcycle.
The menstrual cycle, under the control of the endocrine system , is necessary for reproduction . It is commonly divided into three phases:-
The follicular phase , Ovulation & The luteal phase ; although some sources use a different set of phases:
Menstruation , proliferative phase, and secretory phase.
[ 1 ] Menstrual cycles are counted from the first day of menstrual bleeding. Hormonal contraception interferes with the normal hormonal changes with the aim of preventing reproduction.
Stimulated by gradually increasing amounts of estrogen in the follicular phase, discharges of blood (menses) slow then stop, and the lining of the uterus thickens. Follicles in the ovary begin developing under the influence of a complexinterplay of hormones, and after several days one or occasionally two become dominant (non-dominant follicles atrophy and die). Approximately mid-cycle, 24–36 hours after the Luteinizing Hormone (LH) surges, the dominant follicle releases an ovum, or egg in an event called ovulation. After ovulation, the egg only lives for 24 hours or less without fertilization while the remains ofthe dominant follicle in the ovarybecome a corpus luteum ; this body has a primary function of producing large amounts of progesterone . Under the influence of progesterone, the endometrium (uterine lining) changes to prepare for potential implantation of an embryo to establish a pregnancy . If implantation does not occur within approximately two weeks, the corpus luteum will involute, causing sharp drops in levels of both progesterone and estrogen. These hormone drops cause the uterus to shed its lining and egg in a process termed menstruation.
In the menstrual cycle, changes occur in the female reproductivesystem as well as other systems (which lead to breast tenderness or mood changes, for example). A woman's first menstruation is termed "Menarche" , and occurs typically around age 12-13. The average age of menarche is about A.12.5 years in the United States B.12.72 in Canada C. 12.9 in the UK and D. 13.06 ± 0.10 years in Iceland .
The end of a woman's reproductive phase is called the "Menopause" , Which commonly occurs somewhere between the ages of 45 and 55.
This article focuses on the human menstrualcycle.
The menstrual cycle, under the control of the endocrine system , is necessary for reproduction . It is commonly divided into three phases:-
The follicular phase , Ovulation & The luteal phase ; although some sources use a different set of phases:
Menstruation , proliferative phase, and secretory phase.
[ 1 ] Menstrual cycles are counted from the first day of menstrual bleeding. Hormonal contraception interferes with the normal hormonal changes with the aim of preventing reproduction.
Stimulated by gradually increasing amounts of estrogen in the follicular phase, discharges of blood (menses) slow then stop, and the lining of the uterus thickens. Follicles in the ovary begin developing under the influence of a complexinterplay of hormones, and after several days one or occasionally two become dominant (non-dominant follicles atrophy and die). Approximately mid-cycle, 24–36 hours after the Luteinizing Hormone (LH) surges, the dominant follicle releases an ovum, or egg in an event called ovulation. After ovulation, the egg only lives for 24 hours or less without fertilization while the remains ofthe dominant follicle in the ovarybecome a corpus luteum ; this body has a primary function of producing large amounts of progesterone . Under the influence of progesterone, the endometrium (uterine lining) changes to prepare for potential implantation of an embryo to establish a pregnancy . If implantation does not occur within approximately two weeks, the corpus luteum will involute, causing sharp drops in levels of both progesterone and estrogen. These hormone drops cause the uterus to shed its lining and egg in a process termed menstruation.
In the menstrual cycle, changes occur in the female reproductivesystem as well as other systems (which lead to breast tenderness or mood changes, for example). A woman's first menstruation is termed "Menarche" , and occurs typically around age 12-13. The average age of menarche is about A.12.5 years in the United States B.12.72 in Canada C. 12.9 in the UK and D. 13.06 ± 0.10 years in Iceland .
The end of a woman's reproductive phase is called the "Menopause" , Which commonly occurs somewhere between the ages of 45 and 55.
Breast Cancer
Breast cancer ( malignant breast neoplasm ) is a type of cancer originating from breast tissue, most commonly from the inner lining of milk ducts or the lobules that supply the ducts with milk.
[ 1 ] Cancers originating from ducts are known as ductal carcinomas ; those originating from lobules are known as lobular carcinomas . Breast cancer is a disease of humans and other mammals ; whilethe overwhelming majority of cases in humans are women, men can sometimes also develop breastcancer.
[ 2 ] The size, stage, rate of growth, andother characteristics of the tumor determine the kinds of treatment. Treatment may include surgery , drugs ( hormonal therapy and chemotherapy ), radiation and/or immunotherapy.
[ 3 ] Surgical removal of the tumor provides the single largest benefit, with surgery alone being capable of producing a cure in many cases. To somewhat increase the likelihood of long-term disease-free survival, several chemotherapy regimens are commonly given in addition to surgery. Most forms of chemotherapy kill cells that are dividing rapidly anywhere in the body, and as a result cause temporary hair loss and digestive disturbances. Radiation is indicated especially after breast conserving surgery and substantially improves local relapserates and in many circumstances also overall survival.
[ 4 ] Some breast cancers are sensitive to hormones such as estrogen and/or progesterone , which makes it possible to treat them by blocking the effects of these hormones.
Worldwide, breast cancer comprises 22.9% of all cancers (excluding non-melanoma skin cancers ) in women.
[ 5 ] In 2008, breast cancer caused 458,503 deaths worldwide (13.7% of cancer deaths in women).
[ 6 ] Breast cancer is more than 100 times more common in women than breast cancer in men , although males tend to have poorer outcomes due to delays in diagnosis.
[ 7 ] Prognosis and survival rates vary greatly depending on cancer type, staging and treatment. However, survival rates across the world are generally good.
[ 8 ] Overall more than 8 out of 10 women (84%) in England that are diagnosed with the disease survive it for at least 5 years.
[ 1 ] Cancers originating from ducts are known as ductal carcinomas ; those originating from lobules are known as lobular carcinomas . Breast cancer is a disease of humans and other mammals ; whilethe overwhelming majority of cases in humans are women, men can sometimes also develop breastcancer.
[ 2 ] The size, stage, rate of growth, andother characteristics of the tumor determine the kinds of treatment. Treatment may include surgery , drugs ( hormonal therapy and chemotherapy ), radiation and/or immunotherapy.
[ 3 ] Surgical removal of the tumor provides the single largest benefit, with surgery alone being capable of producing a cure in many cases. To somewhat increase the likelihood of long-term disease-free survival, several chemotherapy regimens are commonly given in addition to surgery. Most forms of chemotherapy kill cells that are dividing rapidly anywhere in the body, and as a result cause temporary hair loss and digestive disturbances. Radiation is indicated especially after breast conserving surgery and substantially improves local relapserates and in many circumstances also overall survival.
[ 4 ] Some breast cancers are sensitive to hormones such as estrogen and/or progesterone , which makes it possible to treat them by blocking the effects of these hormones.
Worldwide, breast cancer comprises 22.9% of all cancers (excluding non-melanoma skin cancers ) in women.
[ 5 ] In 2008, breast cancer caused 458,503 deaths worldwide (13.7% of cancer deaths in women).
[ 6 ] Breast cancer is more than 100 times more common in women than breast cancer in men , although males tend to have poorer outcomes due to delays in diagnosis.
[ 7 ] Prognosis and survival rates vary greatly depending on cancer type, staging and treatment. However, survival rates across the world are generally good.
[ 8 ] Overall more than 8 out of 10 women (84%) in England that are diagnosed with the disease survive it for at least 5 years.
Our Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few invertebrates such as sponges , jellyfish , adult sea squirts and starfish do not have one, even if diffuse neural tissue is present. It is located in the head, usually close to the primary sensory organs for suchsenses as vision, hearing, balance, taste, and smell. The brain of a vertebrate is the most complex organ of its body. In a typical human the cerebral cortex (the largest part) is estimated to contain 15–33 billion neurons , [ 1 ] each connected by synapses to several thousand other neurons.These neurons communicate with one another by means of long protoplasmic fibers called axons , which carry trains of signal pulses called action potentials to distant parts of the brain or body targeting specific recipient cells.
From an evolutionary-biological point of view, the function of thebrain is to exert centralized control over the other organs of the body. The brain acts on the rest of the body either by generating patterns of muscle activity or by driving secretion ofchemicals called hormones . This centralized control allows rapid and coordinated responses to changes in the environment. Some basic types of responsiveness such as reflexes can be mediated by the spinal cord or peripheral ganglia , but sophisticated purposeful controlof behavior based on complex sensory input requires the information-integrating capabilities of a centralized brain.
From a philosophical point of view, what makes the brain special in comparison to other organs is that it forms the physical structure that generatesthe mind . As Hippocrates put it:"Men ought to know that from nothing else but the brain come joys, delights, laughter and sports, and sorrows, griefs, despondency, and lamentations." [ 2 ] In the early part of psychology, the mind was thought to be separate from the brain. However, after early scientists conducted experiments it was determined that the mind was a component of a functioning brain that expressed certain behaviours based on the external environment and the development of the organism. [ 3 ] The mechanisms by which brain activity gives rise to consciousness and thought havebeen very challenging to understand: despite rapid scientific progress, much about how the brain works remains a mystery. The operations of individual brain cells are now understood in considerable detail, but the way they cooperate in ensembles of millions has been very difficult todecipher. The most promising approaches treat the brain as a biological computer, very different in mechanism from electronic computers, but similarin the sense that it acquires information from the surrounding world, stores it, and processes it in a variety of ways.
This article compares the properties of brains across the entire range of animal species, with the greatest attention to vertebrates. It deals with the human brain insofar as it sharesthe properties of other brains. The ways in which the human brain differs from other brains are covered in the human brain article. Several topics that might be covered here are instead covered there because much more can be said about them in a human context. The most important is brain disease and the effects of brain damage, covered in the human brain article because the most common diseases of the human brain either do not show up in other species, or else manifest themselves in different ways.
From an evolutionary-biological point of view, the function of thebrain is to exert centralized control over the other organs of the body. The brain acts on the rest of the body either by generating patterns of muscle activity or by driving secretion ofchemicals called hormones . This centralized control allows rapid and coordinated responses to changes in the environment. Some basic types of responsiveness such as reflexes can be mediated by the spinal cord or peripheral ganglia , but sophisticated purposeful controlof behavior based on complex sensory input requires the information-integrating capabilities of a centralized brain.
From a philosophical point of view, what makes the brain special in comparison to other organs is that it forms the physical structure that generatesthe mind . As Hippocrates put it:"Men ought to know that from nothing else but the brain come joys, delights, laughter and sports, and sorrows, griefs, despondency, and lamentations." [ 2 ] In the early part of psychology, the mind was thought to be separate from the brain. However, after early scientists conducted experiments it was determined that the mind was a component of a functioning brain that expressed certain behaviours based on the external environment and the development of the organism. [ 3 ] The mechanisms by which brain activity gives rise to consciousness and thought havebeen very challenging to understand: despite rapid scientific progress, much about how the brain works remains a mystery. The operations of individual brain cells are now understood in considerable detail, but the way they cooperate in ensembles of millions has been very difficult todecipher. The most promising approaches treat the brain as a biological computer, very different in mechanism from electronic computers, but similarin the sense that it acquires information from the surrounding world, stores it, and processes it in a variety of ways.
This article compares the properties of brains across the entire range of animal species, with the greatest attention to vertebrates. It deals with the human brain insofar as it sharesthe properties of other brains. The ways in which the human brain differs from other brains are covered in the human brain article. Several topics that might be covered here are instead covered there because much more can be said about them in a human context. The most important is brain disease and the effects of brain damage, covered in the human brain article because the most common diseases of the human brain either do not show up in other species, or else manifest themselves in different ways.
Friday, 2 March 2012
Human Kidney
The kidneys are organs that serve several essential regulatory roles inmost animals , including vertebrates and some invertebrates . They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes , maintenance of acid–base balance , and regulation of blood pressure (via maintaining salt and water balance). They serve the body as a natural filter of the blood , and remove wastes which are diverted to the urinary bladder . In producing urine , the kidneys excrete wastes such as urea and ammonium , and they are also responsible for the reabsorption of water , glucose , and amino acids . The kidneys also produce hormones including calcitriol , erythropoietin , and the enzyme renin .
Located at the rear of the abdominal cavity in the retroperitoneum , the kidneys receive blood from the paired renalarteries , and drain into the paired renal veins . Each kidney excretes urine into a ureter , itself a paired structure that empties into the urinary bladder .
Renal physiology is the study of kidney function, while nephrology is the medical specialty concerned with kidney diseases . Diseases of the kidney are diverse, but individuals with kidney disease frequently display characteristic clinical features. Common clinical conditions involving the kidney include the nephritic and nephroticsyndromes , renal cysts , acute kidney injury , chronic kidney disease , urinary tract infection , nephrolithiasis , and urinary tract obstruction . [ 1 ] Various cancers of the kidney exist; the most common adult renal cancer is renalcell carcinoma . Cancers, cysts, and some other renal conditions can be managed with removal of the kidney, or nephrectomy . When renal function, measured by glomerular filtration rate , is persistently poor, dialysis and kidney transplantation may be treatment options. Although they are not severely harmful, kidney stones can be a pain and a nuisance. The removal of kidney stones includes sound wave treatment to break up the stones into smaller pieces, which are then passed through the urinary tract. One common symptom of kidney stones is a sharp pain in the medial/lateral segments of the lower back.
Located at the rear of the abdominal cavity in the retroperitoneum , the kidneys receive blood from the paired renalarteries , and drain into the paired renal veins . Each kidney excretes urine into a ureter , itself a paired structure that empties into the urinary bladder .
Renal physiology is the study of kidney function, while nephrology is the medical specialty concerned with kidney diseases . Diseases of the kidney are diverse, but individuals with kidney disease frequently display characteristic clinical features. Common clinical conditions involving the kidney include the nephritic and nephroticsyndromes , renal cysts , acute kidney injury , chronic kidney disease , urinary tract infection , nephrolithiasis , and urinary tract obstruction . [ 1 ] Various cancers of the kidney exist; the most common adult renal cancer is renalcell carcinoma . Cancers, cysts, and some other renal conditions can be managed with removal of the kidney, or nephrectomy . When renal function, measured by glomerular filtration rate , is persistently poor, dialysis and kidney transplantation may be treatment options. Although they are not severely harmful, kidney stones can be a pain and a nuisance. The removal of kidney stones includes sound wave treatment to break up the stones into smaller pieces, which are then passed through the urinary tract. One common symptom of kidney stones is a sharp pain in the medial/lateral segments of the lower back.
Thursday, 1 March 2012
The duck-billed platypus, Ornithorhynchus anatinus , is a primitive Australian mammal (a monotreme ) that lays eggs. After an egg hatches, the tiny baby (called a puggle) drinks its mother's milk, which comes from tiny openings in the mother's belly. They have a life span of 10-17 years. Platypus live in burrows and spend much of their time in freshwater ponds and streams. The name platypus means "flat footed."
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