In a multicellular organism , an organ is a collection of tissues joined in a structural unit to serve a common function. In the hierarchy of life , an organ lies between tissue and an organ system . Tissues are formed from same type cells to act together in a function. Tissues of different types combine to form an organ which has a specific function. The intestinal wall for example is formed by epithelial tissue and smooth muscle tissue . Two or more organs working together in the execution of a specific body function form an organ system, also called a biological system or body system.
78-415: In human anatomy , the forehead is an area of the head bounded by three features, two of the skull and one of the scalp . The top of the forehead is marked by the hairline , the edge of the area where hair on the scalp grows. The bottom of the forehead is marked by the supraorbital ridge , the bone feature of the skull above the eyes. The two sides of the forehead are marked by the temporal ridge ,
156-444: A head , hair , neck , torso (which includes the thorax and abdomen ), genitals , arms , hands , legs , and feet . The internal human body includes organs, teeth , bones , muscle , tendons , ligaments , blood vessels and blood , lymphatic vessels and lymph . The study of the human body includes anatomy , physiology , histology and embryology . The body varies anatomically in known ways. Physiology focuses on
234-453: A bone feature that links the supraorbital ridge to the coronal suture line and beyond. However, the eyebrows do not form part of the forehead. In Terminologia Anatomica , sinciput is given as the Latin equivalent to "forehead" (etymology of sinciput : from semi- "half" and caput "head".). The bone of the forehead is the squamous part of the frontal bone . The overlying muscles are
312-519: A cell . Here, parts of DNA are copied and sent to the body of the cell via RNA . The RNA is then used to create proteins , which form the basis for cells, their activity, and their products. Proteins dictate cell function and gene expression, a cell is able to self-regulate by the amount of proteins produced. However, not all cells have DNA; some cells such as mature red blood cells lose their nucleus as they mature. The body consists of many different types of tissue , defined as cells that act with
390-412: A long high forehead, honesty, weakness, simplicity, and poor fortune. In fighting, slamming one's forehead into one's opponent is termed a headbutt . Human anatomy The human body is the entire structure of a human being . It is composed of many different types of cells that together create tissues and subsequently organs and then organ systems . The external human body consists of
468-461: A membrane or piece of connective tissue, referring to the opposing sides. The organ level of organisation in animals can be first detected in flatworms and the more derived phyla , i.e. the bilaterians . The less-advanced taxa (i.e. Placozoa , Porifera , Ctenophora and Cnidaria ) do not show consolidation of their tissues into organs. More complex animals are composed of different organs, which have evolved over time. For example,
546-420: A number of body cavities , separated areas which house different organ systems. The brain and central nervous system reside in an area protected from the rest of the body by the blood brain barrier . The lungs sit in the pleural cavity . The intestines , liver , and spleen sit in the abdominal cavity . Height, weight, shape and other body proportions vary individually and with age and sex. Body shape
624-399: A number of sexually transmitted infections including syphilis , HIV , chlamydia , HPV and genital warts . Cancer can affect most parts of the reproductive system including the penis , testicles , prostate , ovaries , cervix , vagina , fallopian , uterus and vulva . The respiratory system consists of the nose, nasopharynx , trachea , and lungs . It brings oxygen from
702-505: A specialised function. The study of tissues is called histology and is often done with a microscope . The body consists of four main types of tissues. These are lining cells ( epithelia ), connective tissue , nerve tissue and muscle tissue . Cells that line surfaces exposed to the outside world or gastrointestinal tract ( epithelia ) or internal cavities ( endothelium ) come in numerous shapes and forms – from single layers of flat cells , to cells with small beating hair-like cilia in
780-687: A whole, are referred to as the Organon because logic is a tool for philosophical thinking. Earlier thinkers, such as those who wrote texts in the Hippocratic corpus , generally did not believe that there were organs of the body but only different parts of the body. Some alchemists (e.g. Paracelsus ) adopted the Hermetic Qabalah assignment between the seven vital organs and the seven classical planets as follows: Chinese traditional medicine recognizes eleven organs, associated with
858-442: Is swallowed , and moves through the esophagus to the stomach . In the stomach, food is mixed with gastric acids to allow the extraction of nutrients . What is left is called chyme ; this then moves into the small intestine , which absorbs the nutrients and water from the chyme. What remains passes on to the large intestine , where it is dried to form feces ; these are then stored in the rectum until they are expelled through
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#1732772731709936-433: Is a common disease in which one or more stones form in the gallbladder or biliary tract . Most people are asymptomatic but if a stone blocks the biliary tract, it causes a gallbladder attack , symptoms may include sudden pain in the upper right abdomen or center of the abdomen. Nausea and vomiting may also occur. Typical treatment is removal of the gallbladder through a procedure called a cholecystectomy . Having gallstones
1014-444: Is a risk factor for gallbladder cancer , which although quite uncommon, is rapidly fatal if not diagnosed early. The circulatory system consists of the heart and blood vessels ( arteries , veins and capillaries ). The heart propels the circulation of the blood, which serves as a "transportation system" to transfer oxygen , fuel, nutrients, waste products, immune cells and signaling molecules (i.e. hormones ) from one part of
1092-415: Is brought by the ureters from the kidneys down to the bladder . The smooth muscle lining the ureter walls continuously tighten and relax through a process called peristalsis to force urine away from the kidneys and down into the bladder. Small amounts of urine are released into the bladder every 10–15 seconds. The bladder is a hollow balloon shaped organ located in the pelvis . It stores urine until
1170-419: Is influenced by the distribution of bones, muscle and fat tissue . Human physiology is the study of how the human body functions. This includes the mechanical, physical, bioelectrical , and biochemical functions of humans in good health, from organs to the cells of which they are composed. The human body consists of many interacting systems of organs. These interact to maintain homeostasis , keeping
1248-509: Is mostly responsible for gathering information with sensory neurons and directing body movements with motor neurons . From a functional perspective, the nervous system is again typically divided into two component parts: the somatic nervous system (SNS) and the autonomic nervous system (ANS). The SNS is involved in voluntary functions like speaking and sensory processes . The ANS is involved in involuntary processes, such as digestion and regulating blood pressure . The nervous system
1326-405: Is similar to the circulatory system in terms of both its structure and its most basic function, to carry a body fluid. The musculoskeletal system consists of the human skeleton (which includes bones , ligaments , tendons , joints and cartilage ) and attached muscles . It gives the body basic structure and the ability for movement. In addition to their structural role, the larger bones in
1404-430: Is subject to many different diseases. In epilepsy , abnormal electrical activity in the brain can cause seizures . In multiple sclerosis , the immune system attacks the nerve linings , damaging the nerves' ability to transmit signals. Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig 's disease, is a motor neuron disease which gradually reduces movement in patients. There are also many other diseases of
1482-406: Is the placenta , which has evolved more than 100 times independently in vertebrates, has evolved relatively recently in some lineages, and exists in intermediate forms in extant taxa. Studies on the evolution of the placenta have identified a variety of genetic and physiological processes that contribute to the origin and evolution of organs, these include the re-purposing of existing animal tissues,
1560-425: Is the organ of thought , emotion, memory , and sensory processing ; it serves many aspects of communication and controls various systems and functions. The special senses consist of vision , hearing , taste , and smell . The eyes , ears , tongue , and nose gather information about the body's environment. From a structural perspective, the nervous system is typically subdivided into two component parts:
1638-442: Is the study of the shape and form of the human body. The human body has four limbs (two arms and two legs), a head and a neck , which connect to the torso . The body's shape is determined by a strong skeleton made of bone and cartilage , surrounded by fat ( adipose tissue ), muscle, connective tissue , organs, and other structures. The spine at the back of the skeleton contains the flexible vertebral column , which surrounds
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#17327727317091716-433: Is variable in shape and size. It stores bile before it is released into the small intestine via the common bile duct to help with digestion of fats . It receives bile from the liver via the cystic duct , which connects to the common hepatic duct to form the common bile duct . The gallbladder gets its blood supply from the cystic artery , which in most people, emerges from the right hepatic artery . Gallstones
1794-441: The anus . The endocrine system consists of the principal endocrine glands : the pituitary , thyroid , adrenals , pancreas , parathyroids , and gonads , but nearly all organs and tissues produce specific endocrine hormones as well. The endocrine hormones serve as signals from one body system to another regarding an enormous array of conditions, resulting in variety of changes of function. The immune system consists of
1872-520: The central nervous system (CNS), composed of the brain and the spinal cord ; and the peripheral nervous system (PNS), composed of the nerves and ganglia outside the brain and spinal cord. The CNS is mostly responsible for organizing motion , processing sensory information , thought, memory, cognition and other such functions. It remains a matter of some debate whether the CNS directly gives rise to consciousness . The peripheral nervous system (PNS)
1950-487: The connective tissues that provide a suitable place for it to be situated and anchored. The main tissues that make up an organ tend to have common embryologic origins, such as arising from the same germ layer . Organs exist in most multicellular organisms . In single-celled organisms such as members of the eukaryotes , the functional analogue of an organ is known as an organelle . In plants, there are three main organs. The number of organs in any organism depends on
2028-418: The haruspices or the augurs in order to divine the future by their shape, dimensions or other factors. This practice remains an important ritual in some remote, tribal societies. The term "visceral" is contrasted with the term " parietal ", meaning "of or relating to the wall of a body part, organ or cavity " The two terms are often used in describing a membrane or piece of connective tissue, referring to
2106-468: The heart , lungs and liver . Many organs reside within cavities within the body. These cavities include the abdomen (which contains the stomach, for example) and pleura , which contains the lungs. The heart is an organ located in the thoracic cavity between the lungs and slightly to the left. It is surrounded by the pericardium , which holds it in place in the mediastinum and serves to protect it from blunt trauma, infection and help lubricate
2184-441: The kidneys filter the blood through their respective nephrons , removing waste products like urea , creatinine and maintaining the proper balance of electrolytes and turning the waste products into urine by combining them with water from the blood. The kidneys filter about 150 quarts (170 liters) of blood daily, but most of it is returned to the blood stream with only 1-2 quarts (1-2 liters) ending up as urine. The urine
2262-467: The liver , pancreas , spleen , kidneys , and adrenal glands . The hollow organs of the abdomen are the stomach , intestines , gallbladder , bladder , and rectum . In the thoracic cavity , the heart is a hollow, muscular organ. Splanchnology is the study of the viscera. The term "visceral" is contrasted with the term " parietal ", meaning "of or relating to the wall of a body part, organ or cavity ". The two terms are often used in describing
2340-549: The nervous and endocrine system both operate via a shared organ, the hypothalamus . For this reason, the two systems are combined and studied as the neuroendocrine system . The same is true for the musculoskeletal system because of the relationship between the muscular and skeletal systems . In the study of anatomy , viscera ( sg. : viscus ) refers to the internal organs of the abdominal , thoracic , and pelvic cavities . The abdominal organs may be classified as solid organs or hollow organs . The solid organs are
2418-400: The occipitofrontalis , procerus , and corrugator supercilii muscles, all of which are controlled by the temporal branch of the facial nerve . The sensory nerves of the forehead connect to the ophthalmic branch of the trigeminal nerve and to the cervical plexus , and lie within the subcutaneous fat. The motor nerves of the forehead connect to the facial nerve . The ophthalmic branch of
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2496-456: The ovary of a female is penetrated by sperm . The egg then lodges in the uterus , where an embryo and later fetus develop until birth . Growth and development occur after birth, and include both physical and psychological development, influenced by genetic, hormonal, environmental and other factors. Development and growth continue throughout life, through childhood , adolescence , and through adulthood to old age , and are referred to as
2574-407: The sinoatrial node traveling through the atria causing them to pump blood into the ventricles . It then travels to the atrioventricular node , which makes the signal slow down slightly allowing the ventricles to fill with blood before pumping it out and starting the cycle over again. Coronary artery disease is the leading cause of death worldwide , making up 16% of all deaths. It is caused by
2652-400: The spinal cord , which is a collection of nerve fibres connecting the brain to the rest of the body. Nerves connect the spinal cord and brain to the rest of the body. All major bones, muscles, and nerves in the body are named, with the exception of anatomical variations such as sesamoid bones and accessory muscles . Blood vessels carry blood throughout the body, which moves because of
2730-421: The spleen and bone marrow . The digestive system consists of the mouth including the tongue and teeth , esophagus , stomach , ( gastrointestinal tract , small and large intestines , and rectum ), as well as the liver , pancreas , gallbladder , and salivary glands . It converts food into small, nutritional, non-toxic molecules for distribution and absorption into the body. These molecules take
2808-432: The testicles . The testicle is the gonad , the sex gland that produces the sperm cells . Unlike the egg cells in the female, sperm cells are produced throughout life. Other internal sex organs are the epididymides , vasa deferentia , and some accessory glands . Diseases that affect the reproductive system include polycystic ovary syndrome , a number of disorders of the testicles including testicular torsion , and
2886-427: The uterus , and the cervix . At birth there are about 70,000 immature egg cells that degenerate until at puberty there are around 40,000. No more egg cells are produced. Hormones stimulate the beginning of menstruation, and the ongoing menstrual cycles . The female external sex organs are the vulva ( labia , clitoris , and vestibule ). The male external genitalia include the penis and scrotum that contains
2964-441: The white blood cells , the thymus , lymph nodes and lymph channels, which are also part of the lymphatic system . The immune system provides a mechanism for the body to distinguish its own cells and tissues from outside cells and substances and to neutralize or destroy the latter by using specialized proteins such as antibodies , cytokines , and toll-like receptors , among many others. The integumentary system consists of
3042-461: The 20th century, organ transplants began to take place as scientists knew more about the anatomy of organs. These came later in time as procedures were often dangerous and difficult. Both the source and method of obtaining the organ to transplant are major ethical issues to consider, and because organs as resources for transplant are always more limited than demand for them, various notions of justice, including distributive justice , are developed in
3120-441: The acquisition of new functional properties by these tissues, and novel interactions of distinct tissue types. The study of plant organs is covered in plant morphology . Organs of plants can be divided into vegetative and reproductive. Vegetative plant organs include roots , stems , and leaves . The reproductive organs are variable. In flowering plants , they are represented by the flower , seed and fruit . In conifers ,
3198-436: The ages of 9 and 13 and is characterized by ovulation and menstruation ; the growth of secondary sex characteristics, such as growth of pubic and underarm hair , breast , uterine and vaginal growth, widening hips and increased height and weight, also occur during puberty. Male puberty sees the further development of the penis and testicles . The female inner sex organs are the two ovaries, their fallopian tubes ,
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3276-435: The air and excretes carbon dioxide and water back into the air. First, air is pulled through the trachea into the lungs by the diaphragm pushing down, which creates a vacuum . Air is briefly stored inside small sacs known as alveoli (sing.: alveolus) before being expelled from the lungs when the diaphragm contracts again. Each alveolus is surrounded by capillaries carrying deoxygenated blood, which absorbs oxygen out of
3354-420: The air and into the bloodstream . For the respiratory system to function properly, there need to be as few impediments as possible to the movement of air within the lungs. Inflammation of the lungs and excess mucus are common sources of breathing difficulties. In asthma , the respiratory system is persistently inflamed, causing wheezing or shortness of breath . Pneumonia occurs through infection of
3432-400: The alveoli, and may be caused by tuberculosis . Emphysema , commonly a result of smoking , is caused by damage to connections between the alveoli. The urinary system consists of the two kidneys , two ureters , bladder , and urethra . It removes waste materials from the blood through urine, which carries a variety of waste molecules and excess ions and water out of the body. First,
3510-406: The beating of the heart . Venules and veins collect blood low in oxygen from tissues throughout the body. These collect in progressively larger veins until they reach the body's two largest veins, the superior and inferior vena cava , which drain blood into the right side of the heart. From here, the blood is pumped into the lungs where it receives oxygen and drains back into the left side of
3588-427: The body contain bone marrow , the site of production of blood cells. Also, all bones are major storage sites for calcium and phosphate . This system can be split up into the muscular system and the skeletal system . The nervous system consists of the body's neurons and glial cells, which together form the nerves , ganglia and gray matter , which in turn form the brain and related structures. The brain
3666-423: The body in a stable state with safe levels of substances such as sugar and oxygen in the blood. Each system contributes to homeostasis, of itself, other systems, and the entire body. Some combined systems are referred to by joint names. For example, the nervous system and the endocrine system operate together as the neuroendocrine system . The nervous system receives information from the body, and transmits this to
3744-441: The body to another. Paths of blood circulation within the human body can be divided into two circuits: the pulmonary circuit , which pumps blood to the lungs to receive oxygen and leave carbon dioxide , and the systemic circuit, which carries blood from the heart off to the rest of the body. The blood consists of fluid that carries cells in the circulation, including some that move from tissue to blood vessels and back, as well as
3822-558: The body. The adult male body is about 60% total body water content of some 42 litres (9.2 imp gal; 11 US gal). This is made up of about 19 litres (4.2 imp gal; 5.0 US gal) of extracellular fluid including about 3.2 litres (0.70 imp gal; 0.85 US gal) of blood plasma and about 8.4 litres (1.8 imp gal; 2.2 US gal) of interstitial fluid , and about 23 litres (5.1 imp gal; 6.1 US gal) of fluid inside cells. The content, acidity and composition of
3900-412: The brain signals it to relax the urinary sphincter and release the urine into the urethra starting urination . A normal bladder can hold up to 16 ounces (half a liter) for 3–5 hours comfortably. Numerous diseases affect the urinary system including kidney stones , which are formed when materials in the urine concentrate enough to form a solid mass, urinary tract infections , which are infections of
3978-463: The brain via nerve impulses and neurotransmitters . At the same time, the endocrine system releases hormones, such as to help regulate blood pressure and volume. Together, these systems regulate the internal environment of the body, maintaining blood flow, posture, energy supply, temperature, and acid balance ( pH ). Development of the human body is the process of growth to maturity. The process begins with fertilisation, where an egg released from
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#17327727317094056-481: The buildup of plaque in the coronary arteries supplying the heart, eventually the arteries may become so narrow that not enough blood is able to reach the myocardium , a condition known as myocardial infarction or heart attack , this can cause heart failure or cardiac arrest and eventually death. Risk factors for coronary artery disease include obesity , smoking , high cholesterol , high blood pressure , lack of exercise and diabetes . Cancer can affect
4134-412: The cell numbers of all the organs of the body and cell types . The skin of the body is also host to billions of commensal organisms as well as immune cells. Not all parts of the body are made from cells. Cells sit in an extracellular matrix that consists of proteins such as collagen , surrounded by extracellular fluids. Cells in the body function because of DNA . DNA sits within the nucleus of
4212-432: The covering of the body (the skin ), including hair and nails as well as other functionally important structures such as the sweat glands and sebaceous glands . The skin provides containment, structure, and protection for other organs, and serves as a major sensory interface with the outside world. The lymphatic system extracts, transports and metabolizes lymph, the fluid found in between cells. The lymphatic system
4290-416: The definition used. There are approxiamately 79 Organs in the human body,but it is something that is debated as not all scientist agree on what counts as an organ. Except for placozoans , multicellular animals including humans have a variety of organ systems . These specific systems are widely studied in human anatomy . The functions of these organ systems often share significant overlap. For instance,
4368-402: The ethical analysis. This situation continues as long as transplantation relies upon organ donors rather than technological innovation, testing, and industrial manufacturing. The English word "organ" dates back to the twelfth century and refers to any musical instrument. By the late 14th century, the musical term's meaning had narrowed to refer specifically to the keyboard-based instrument . At
4446-403: The eyebrows inwards and down, forming a frown . The procerus muscles can pull down the centre portions of the eyebrows. The movements of the muscles in the forehead produce characteristic wrinkles in the skin. The occipitofrontalis muscles produce the transverse wrinkles across the width of the forehead, and the corrugator supercilii muscles produce vertical wrinkles between the eyebrows above
4524-428: The forehead is governed by Mars . A low and little forehead denoted magnanimity, boldness, and confidence; a fleshy and wrinkle-free forehead, litigiousness, vanity, deceit, and contentiousness; a sharp forehead, weakness and fickleness; a wrinkled forehead, great spirit and wit yet poor fortune; a round forehead, virtue and good understanding; a full large forehead, boldness, malice, boundary issues, and high spirit; and
4602-491: The forehead is via the left and right superorbital, supertrochealar, and anterior branches of the superficial temporal artery . The muscles of the forehead help to form facial expressions . There are four basic motions, which can occur individually or in combination to form different expressions. The occipitofrontalis muscles can raise the eyebrows , either together or individually, forming expressions of surprise and quizzicality . The corrugator supercilii muscles can pull
4680-458: The form of proteins (which are broken down into amino acids ), fats , vitamins and minerals (the last of which are mainly ionic rather than molecular). After being swallowed , food moves through the gastrointestinal tract by means of peristalsis : the systematic expansion and contraction of muscles to push food from one area to the next. Digestion begins in the mouth , which chews food into smaller pieces for easier digestion. Then it
4758-403: The heart , though it is exceedingly rare and has usually metastasized from another part of the body such as the lungs or breasts . This is because the heart cells quickly stop dividing and all growth occurs through size increase rather than cell division . The gallbladder is a hollow pear-shaped organ located posterior to the inferior middle part of the right lobe of the liver . It
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#17327727317094836-434: The heart. From here, it is pumped into the body's largest artery , the aorta , and then progressively smaller arteries and arterioles until it reaches tissue. Here, blood passes from small arteries into capillaries , then small veins and the process begins again. Blood carries oxygen , waste products, and hormones from one place in the body to another. Blood is filtered at the kidneys and liver . The body consists of
4914-468: The liver and heart evolved in the chordates about 550-500 million years ago, while the gut and brain are even more ancient, arising in the ancestor of vertebrates, insects, molluscs, and worms about 700–650 million years ago. Given the ancient origin of most vertebrate organs, researchers have looked for model systems, where organs have evolved more recently, and ideally have evolved multiple times independently. An outstanding model for this kind of research
4992-421: The lungs, to column-like cells that line the stomach . Endothelial cells are cells that line internal cavities including blood vessels and glands. Lining cells regulate what can and cannot pass through them, protect internal structures, and function as sensory surfaces. Organs , structured collections of cells with a specific function, mostly sit within the body, with the exception of skin . Examples include
5070-415: The movement of the heart via pericardial fluid . The heart works by pumping blood around the body allowing oxygen , nutrients , waste , hormones and white blood cells to be transported. The heart is composed of two atria and two ventricles . The primary purpose of the atria is to allow uninterrupted venous blood flow to the heart during ventricular systole . This allows enough blood to get into
5148-407: The nervous system. The purpose of the reproductive system is to reproduce and nurture the growth of offspring. The functions include the production of germ cells and hormones. The sex organs of the male reproductive system and the female reproductive system develops and mature at puberty . These systems include the internal and external genitalia . Female puberty generally occurs between
5226-467: The new generation of plants (see clonal colony ). Many societies have a system for organ donation , in which a living or deceased donor's organ are transplanted into a person with a failing organ. The transplantation of larger solid organs often requires immunosuppression to prevent organ rejection or graft-versus-host disease . There is considerable interest throughout the world in creating laboratory-grown or artificial organs . Beginning in
5304-468: The nose. The procerus muscles cause the nose to wrinkle. In physiognomy and phrenology , the shape of the forehead was taken to symbolise intellect and intelligence. "Animals, even the most intelligent of them,", wrote Samuel R. Wells in 1942, "can hardly be said to have any forehead at all, and in natural total idiots it is very diminished". Pseudo-Aristotle , in Physiognomica , stated that
5382-403: The opposing sides. Aristotle used the word frequently in his philosophy, both to describe the organs of plants or animals (e.g. the roots of a tree, the heart or liver of an animal) because, in ancient Greek, the word ' organon ' means 'tool', and Aristotle believed that the organs of the body were tools for us by means of which we can do things. For similar reasons, his logical works, taken as
5460-514: The organ that bears the reproductive structures is called a cone . In other divisions ( phyla ) of plants, the reproductive organs are called strobili , in Lycopodiophyta , or simply gametophores in mosses . Common organ system designations in plants include the differentiation of shoot and root. All parts of the plant above ground (in non- epiphytes ), including the functionally distinct leaf and flower organs, may be classified together as
5538-464: The process of aging . Organs An organ's tissues can be broadly categorized as parenchyma , the functional tissue, and stroma , the structural tissue with supportive, connective, or ancillary functions. For example, the gland 's tissue that makes the hormones is the parenchyma , whereas the stroma includes the nerves that innervate the parenchyma, the blood vessels that oxygenate and nourish it and carry away its metabolic wastes, and
5616-489: The same time, a second meaning arose, in reference to a "body part adapted to a certain function". Plant organs are made from tissue composed of different types of tissue. The three tissue types are ground, vascular, and dermal. When three or more organs are present, it is called an organ system. The adjective visceral , also splanchnic , is used for anything pertaining to the internal organs. Historically, viscera of animals were examined by Roman pagan priests like
5694-409: The shoot organ system. The vegetative organs are essential for maintaining the life of a plant. While there can be 11 organ systems in animals, there are far fewer in plants, where some perform the vital functions, such as photosynthesis , while the reproductive organs are essential in reproduction . However, if there is asexual vegetative reproduction , the vegetative organs are those that create
5772-525: The systems and organs of the human body and their functions. Many systems and mechanisms interact in order to maintain homeostasis , with safe levels of substances such as sugar , iron , and oxygen in the blood. The body is studied by health professionals , physiologists, anatomists, and artists to assist them in their work. The human body is composed of elements including hydrogen , oxygen , carbon , calcium and phosphorus . These elements reside in trillions of cells and non-cellular components of
5850-419: The trigeminal nerve, the supraorbital nerve, divides at the orbital rim into two parts in the forehead. One part, the superficial division, runs over the surface of the occipitofrontalis muscle. This provides sensation for the skin of the forehead, and for the front edge of the scalp. The other part, the deep division, runs into the occipitofrontalis muscle and provides frontoparietal sensation. Blood supply to
5928-405: The urinary tract and can cause pain when urinating, frequent urination and even death if left untreated. Renal failure occurs when the kidneys fail to adequately filter waste from the blood and can lead to death if not treated with dialysis or kidney transplantation . Cancer can affect the bladder , kidneys , urethra and ureters , with the latter two being far more rare. Human anatomy
6006-417: The ventricles during atrial systole . Consequently, the atria allows a cardiac output roughly 75% greater than would be possible without them. The purpose of the ventricles is to pump blood to the lungs through the right ventricle and to the rest of the body through the left ventricle. The heart has an electrical conduction system to control the contraction and relaxation of the muscles. It starts in
6084-401: The water inside and outside cells is carefully maintained. The main electrolytes in body water outside cells are sodium and chloride , whereas within cells it is potassium and other phosphates . The body contains trillions of cells , the fundamental unit of life. At maturity, there are roughly 30 trillion cells, and 38 trillion bacteria in the body, an estimate arrived at by totaling
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