human body | Britannica.com Human body Human body, the physical substance of the human organism, composed of living cells and extracellular materials and organized into tissues, organs, and systems. For a depiction of the gross anatomy of the human body, see Human Anatomy . Many entries describe the body’s major structures. For example, see abdominal cavity ; adrenal gland ; aorta ; bone ; brain ; ear ; eye ; heart ; kidney ; large intestine ; lung ; nose ; ovary ; pancreas ; pituitary gland ; small intestine ; spinal cord ; spleen ; stomach ; testis ; thymus ; thyroid gland ; tooth ; uterus ; vertebral column . Human beings are, of course, animals—more particularly, members of the order Mammalia in the subphylum Vertebrata of the phylum Chordata. Like all chordates, the human animal has a bilaterally symmetrical body that is characterized at some point during its development by a dorsal supporting rod (the notochord ), gill slits in the region of the pharynx , and a hollow dorsal nerve cord.

Of these features, the first two are present only during the embryonic stage in the human; the notochord is replaced by the vertebral column, and the pharyngeal gill slits are lost completely. The dorsal nerve cord is the spinal cord in human beings; it remains throughout life. Characteristic of the vertebrate form, the human body has an internal skeleton that includes a backbone of vertebrae. Typical of mammalian structure, the human body shows such characteristics as hair, mammary glands, and highly developed sense organs. Similar Topics ligament Beyond these similarities, however, lie some profound differences. Among the mammals, only human beings have a predominantly two-legged ( bipedal ) posture, a fact that has greatly modified the general mammalian body plan. (Even the kangaroo, which hops on two legs when moving rapidly, walks on four legs and uses its tail as a “third leg” when standing.) Moreover, the human brain, particularly that part called the neocortex, is far and away the most highly developed in the animal kingdom. As intelligent as are many other mammals—such as chimpanzees and dolphins—none have achieved the intellectual status of the human species.

Chemical composition of the body Chemically, the human body consists mainly of water and of organic compounds—i.e., lipids, proteins, carbohydrates, and nucleic acids. Water is found in the extracellular fluids of the body (the blood plasma, the lymph , and the interstitial fluid) and within the cells themselves. It serves as a solvent without which the chemistry of life could not take place. The human body is about 60 percent water by weight. Lipids —chiefly fats, phospholipids, and steroids—are major structural components of the human body. Fats provide an energy reserve for the body, and fat pads also serve as insulation and shock absorbers. Phospholipids and the steroid compound cholesterol are major components of the membrane that surrounds each cell. Proteins also serve as a major structural component of the body. Like lipids, proteins are an important constituent of the cell membrane. In addition, such extracellular materials as hair and nails are composed of protein. So also is collagen, the fibrous, elastic material that makes up much of the body’s skin, bones, tendons, and ligaments. Proteins also perform numerous functional roles in the body.

Particularly important are those cellular proteins called enzymes, which catalyze the chemical reactions necessary for life. Human Body: Fact or Fiction? Carbohydrates are present in the human body largely as fuels, either as simple sugars circulating through the bloodstream or as glycogen, a storage compound found in the liver and the muscles. Small amounts of carbohydrates also occur in cell membranes, but, in contrast to plants and many invertebrate animals, humans have little structural carbohydrate in their bodies. Britannica Stories Ringling Bros. Folds Its Tent Nucleic acids make up the genetic materials of the body. Deoxyribonucleic acid ( DNA ) carries the body’s hereditary master code, the instructions according to which each cell operates. It is DNA, passed from parents to offspring, that dictates the inherited characteristics of each human being. Ribonucleic acid (RNA), of which there are several types, helps carry out the instructions encoded in the DNA. Along with water and organic compounds , the body’s constituents include various inorganic minerals. Chief among these are calcium , phosphorus , sodium, magnesium, and iron. Calcium and phosphorus, combined as calcium-phosphate crystals, form a large part of the body’s bones.

Calcium is also present as ions in the blood and interstitial fluid , as is sodium. Ions of phosphorus, potassium, and magnesium, on the other hand , are abundant within the intercellular fluid. All of these ions play vital roles in the body’s metabolic processes. Iron is present mainly as part of hemoglobin, the oxygen-carrying pigment of the red blood cells. Other mineral constituents of the body, found in minute but necessary concentrations, include cobalt, copper, iodine, manganese, and zinc. Organization of the body The cell is the basic living unit of the human body—indeed, of all organisms. The human body consists of more than 75 trillion cells, each capable of growth, metabolism , response to stimuli, and, with some exceptions, reproduction. Although there are some 200 different types of cells in the body, these can be grouped into four basic classes.

These four basic cell types, together with their extracellular materials, form the fundamental tissues of the human body: (1) epithelial tissues, which cover the body’s surface and line the internal organs, body cavities, and passageways; (2) muscle tissues, which are capable of contraction and form the body’s musculature; (3) nerve tissues, which conduct electrical impulses and make up the nervous system; and (4) connective tissues , which are composed of widely spaced cells and large amounts of intercellular matrix and which bind together various body structures. (Bone and blood are considered specialized connective tissues, in which the intercellular matrix is, respectively, hard and liquid.) Connect with Britannica Facebook Twitter YouTube Instagram Pinterest The next level of organization in the body is that of the organ. An organ is a group of tissues that constitutes a distinct structural and functional unit. Thus, the heart is an organ composed of all four tissues, whose function is to pump blood throughout the body. Of course, the heart does not function in isolation; it is part of a system composed of blood and blood vessels as well. The highest level of body organization, then, is that of the organ system.

The body includes nine major organ systems, each composed of various organs and tissues that work together as a functional unit. The chief constituents and prime functions of each system are summarized below. (1) The integumentary system , composed of the skin and associated structures, protects the body from invasion by harmful microorganisms and chemicals; it also prevents water loss from the body. (2) The musculoskeletal system (also referred to separately as the muscle system and the skeletal system), composed of the skeletal muscles and bones (with about 206 of the latter in adults), moves the body and protectively houses its internal organs. (3) The respiratory system, composed of the breathing passages, lungs, and muscles of respiration, obtains from the air the oxygen necessary for cellular metabolism; it also returns to the air the carbon dioxide that forms as a waste product of such metabolism. (4) The circulatory system, composed of the heart, blood, and blood vessels, circulates a transport fluid throughout the body, providing the cells with a steady supply of oxygen and nutrients and carrying away such waste products as carbon dioxide and toxic nitrogen compounds.

(5) The digestive system, composed of the mouth, esophagus , stomach, and intestines, breaks down food into usable substances (nutrients), which are then absorbed from the blood or lymph; this system also eliminates the unusable or excess portion of the food as fecal matter. (6) The excretory system, composed of the kidneys, ureters, urinary bladder , and urethra , removes toxic nitrogen compounds and other wastes from the blood. (7) The nervous system, composed of the sensory organs, brain, spinal cord, and nerves, transmits, integrates , and analyzes sensory information and carries impulses to effect the appropriate muscular or glandular responses. (8) The endocrine system , composed of the hormone-secreting glands and tissues, provides a chemical communications network for coordinating various body processes. (9) The reproductive system, composed of the male or female sex organs, enables reproduction and thereby ensures the continuation of the species. A discussion of the organ systems of the human body and their influence on one another. Basic form and development Editor Picks: Exploring 10 Types of Basketball Movies In general structure, the human body follows a plan that can be described as a cylinder enclosing two tubes and a rod.

This body plan is most clearly evident in the embryo ; by birth, the plan is apparent only in the trunk region—i.e., in the thorax and abdomen . The body wall forms the cylinder. The two tubes are the ventrally located alimentary canal (i.e., the digestive tract) and the dorsally located neural tube (i.e., the spinal cord). Between the tubes lies the rod—the notochord in the embryo, which becomes the vertebral column prior to birth. (The terms dorsal and ventral refer respectively to the back and the front, or belly, of an animal.) Within the embryo, the essential body parts are: (1) the outer enclosing epidermal membrane (in the embryo called ectoderm ); (2) the dorsal neural tube; (3) the supporting notochord; (4) the ventral alimentary tube, which becomes the lining of the stomach and intestine (in the embryo called endoderm); (5) the intermediate mass (in the embryo called mesoderm); and (6) a rather fluid tissue that fills the interspaces, derived from the mesoderm and in the embryo called mesenchyme. Everything in the body derives from one of these six embryonic parts.

The mesoderm constitutes a considerable pad of tissue on each side of the embryo, extending all the way from the back to the front sides of the body wall. It is hollow, for a cleftlike space appears in it on each side. These are the right and left body cavities. In the dorsal part of the body they are temporary; in the ventral part they become permanent, forming the two pleural cavities, which house the lungs; the peritoneal cavity, which contains the abdominal organs; and the pericardial cavity, which encloses the heart. The dorsal part of the mesoderm becomes separated from the ventral mesoderm and divides itself into serial parts like a row of blocks, 31 on each side. These mesodermal segments grow in all directions toward the epidermal membrane. They form bones, muscles, and the deeper, leathery part of the skin. Dorsally they form bony arches protecting the spinal cord, and ventrally the ribs protecting the alimentary canal and heart. Thus they form the body wall and the limbs—much the weightier part of the body.

They give the segmental character to the body wall in neck and trunk, and, following their lead, the spinal cord becomes correspondingly segmented. The ventral mesoderm is not so extensive; it remains near the alimentary tube and becomes the continuous muscle layer of the stomach and intestine. It also forms the lining of the body cavities, the smooth, shining, slippery pleura and peritoneum. The mesenchyme forms blood and lymph vessels, the heart, and the loose cells of connective tissues. Trending Topics Opium Wars The neural tube itself is formed from the ectoderm at a very early stage. Anteriorly (i.e., toward the head) it extends above the open end of the cylinder and is enlarged to form the brain. It is not in immediate contact with the epidermis, for the dorsal mesoderm grows up around it and around the roots of the cranial nerves as a covering, separating the brain from the epidermis. Posteriorly the neural tube terminates in the adult opposite the first lumbar vertebra. If the cylindrical body wall is followed headward, it is found to terminate ventrally as the tongue , dorsally in the skull around the brain, ears, and eyes.

There is a considerable interval between eyes and tongue. This is occupied partly by a deep depression of the epidermis between them, which dips in to join the alimentary tube (lining of the mouth). Posteriorly the ventral body wall joins the dorsal at the tailbone (coccyx), thus terminating the body cavities. Headward, the alimentary tube extends up in front of the notochord and projects above the upper part of the body wall (tongue) and in front of and below the brain to join the epidermal depression. From the epidermal depression are formed the teeth and most of the mouth lining; from the upper end of the alimentary canal are formed the pharynx, larynx , trachea , and lungs. The alimentary canal at its tail end splits longitudinally into two tubes—an anterior and a posterior. The anterior tube becomes the bladder , urethra, and, in the female, the lining of the vagina , where it joins a depression of the ectoderm. The posterior (dorsal) tube becomes the rectum and ends just in front of the coccyx by joining another ectodermal depression (the anus).

Effects of aging As the human body ages it undergoes various changes, which are experienced at different times and at varying rates among individuals. The skin is one of the most accurate registers of aging. It becomes thin and dry and loses elasticity. Patches of darker pigmentation appear, commonly called liver spots, though they have no relation to that organ. Hair grays and thins. Wounds take longer to heal; some reparations take five times as long at 60 as at 10 years of age. Sensory fibres in spinal nerves become fewer; the ganglion cells become pigmented and some of them die. In the auditory apparatus some nerve cells and fibres are lost, and the ability to hear high notes diminishes. In the eye the lens loses its elasticity. Organs such as the liver and kidneys lose mass with age and decline in efficiency . The brain is somewhat smaller after the age of 40 and shrinks markedly after age 75, especially in the frontal and occipital lobes. This shrinkage is not, however, correlated with declines in mental capacity. Intellectual declines in the elderly are the consequence of underlying disease conditions, such as Alzheimer’s disease or cerebrovascular disease.

The bones become lighter and more brittle because of a loss of calcium. This loss in bone mass is greater in women than men after the fifth decade. In joints the cartilage covering the ends of bone becomes thinner and sometimes disappears in spots, so bone meets bone directly and the old joints creak. Compression of the spinal column can lead to a loss of height. Muscular strength decreases but with marked individual variability. The arteries become fibrous and sclerosed. Because of decreasing elasticity, they tend to become rigid tubes. Fatty spots, which appear in their lining even in youth, are always present in old age. In vitro experiments indicate that the body’s cells are programmed to undergo a finite number of divisions, after which time they lose their reproductive capacity. Thus, the potential longevity of the human body—about 100 years—seems to be encoded within the very cells of the body. Change incident to environmental factors Although the basic form of the human body was established in man’s anthropoid ancestors, evolutionary adaptations to different environments are apparent among various human populations. For example, physical adaptations in human beings are seen in response to extreme cold , humid heat , and high altitudes.

Extreme cold favours short, round persons with short arms and legs, flat faces with fat pads over the sinuses, narrow noses, and a heavier than average layer of body fat. These adaptations provide minimum surface area in relation to body mass for minimum heat loss, minimum heat loss in the extremities (which allows manual dexterity during exposure to cold and guards against frostbite), and protection of the lungs and base of the brain against cold air in the nasal passages. In hot climates the problem is not in maintaining body heat but in dissipating it. Ordinarily the body rids itself of excess heat by sweating. In conditions of humid heat, however, the humidity of the surrounding air prevents the evaporation of perspiration to some extent, and overheating may result. Hence, the heat-adapted person in humid climates is characteristically tall and thin, so that there is maximum surface area for heat radiation. The person living in hot climates has little body fat; often a wide nose, since warming of the air in the nasal passages is not desirable; and, usually, dark skin, which provides a shield from harmful solar radiation. High altitudes demand a degree of cold adaptation , as well as adaptation for low air pressure and the consequent low oxygen.

This adaptation is accomplished by an increase in lung tissue generally. Despite the fact that the general shape and size of the body and its parts are determined by heredity, the body can undergo some modifications in response to present conditions. Thus, a person who moves from a home at sea level to one at mountain altitudes will experience an increase in the number of red blood cells; this increase helps compensate for the lower oxygen levels of his new environment . Similarly, a light-skinned individual who moves to a hot tropical region will develop increased pigmentation in his skin. In such situations, the resultant form is seldom perfect for the new conditions, but it is adapted to present needs well enough to maintain life with the least waste of energy. Additional Media Exercise 40: Anatomy of the Urinary System Flashcards | Easy Notecards 5 WHAT IS THE FUNCTION OF THE FAT CUSHION THAT SURROUNDS THE KIDNEYS IN LIFE? PERIRENAL FAT CAPSULES ANCHOR THE KIDNEYS TO THE DORSAL BODY WILL IN A RETROPERITONEAL POSITION & CUSHIONS IT AGAINST BLOWS.

6 KIDNEYS ARE LESS SECURELY ANCHORED AND DROP TO A MORE INFERIOR POSITION. 7 WHY IS INCONTINENCE A NORMAL PHENOMENON IN THE CHILD UNDER 1 1/2 TO 2 YEARS OLD? BECAUSE THEY HAVE NOT YET GAINED MUSCLE CONTROL OVER THEIR EXTERNAL SPHINCTER. 8 WHAT EVENTS MAY LEAD TO ITS OCCURRENCE IN THE ADULT? SPINAL CORD INJURY, EMOTIONAL PROBLEMS, BLADDER IRRITABILITY, OR SOME OTHER PATHOLOGY OF THE URINARY TRACT.

9 SMOOTH MEMBRANE, TIGHTLY ADHERENT TO THE KIDNEY SURFACE FIBROUS CAPSULE PORTION OF THE KIDNEY CONTAINING MOSTLY COLLECTING DUCTS MEDULLA PORTION OF THE KIDNEY CONTAINING THE BULK OF THE NEPHRON STRUCTURES CORTEX SUPERFICIAL REGION OF KIDNEY TISSUE CORTEX BASINLIKE AREA OF THE KIDNEY, CONTINUOUS WITH THE URETER RENAL PELVIS A CUP-SHAPED EXTENSION OF THE PELVIS THAT ENCIRCLES THE APEX OF A PYRAMID MINOR CALYX AREA OF CORTICAL TISSUE RUNNING BETWEEN THE MEDULLARY PYRAMIDS RENAL COLUMN PRIMARY SITE OF TUBULAR REABSORPTION PROXIMAL CONVULATED TUBULE STRUCTURE THAT CONVEYS THE PROCESSED FILTRATE (URINE) TO THE RENAL PELVIS DISTAL CONVULATED TUBULE BLOOD SUPPLY THAT DIRECTLY RECIEVES SUBSTANCES FROM THE TUBULAR CELLS PERITUBULAR CAPILLARIES ITS INNER (VISCERAL) MEMBRANE FORMS PART OF

 THE FILTRATION MEMBRANE GLOMERULAR CAPSULE EXPLAIN WHY THE GLOMERULUS IS SUCH A HIGH-PRESSURE CAPILLARY BED.

1. THE BED IS FED AND DRAINED BY ARTERIOLES (HIGH RESISTANT VESSELS) 2. THE AFFERENT ARTERIOLE (FEEDER) IS LARGER IN DIAMETER THAN THE EFFERENT ARTERIOLE (DRAINING) 24 HOW DOES ITS HIGH-PRESSURE CONDITION AID ITS FUNCTION OF FILTRATE FORMATION? THE HIGHER THE CAPILLARY PRESSURE, THE MORE FILTRATE WILL BE FORMED 25 WHAT STRUCTURAL MODIFICATION OF CERTAIN TUBULE CELLS ENHANCES THEIR ABILITY TO REABSORB SUBSTANCES FROM THE FILTRATE? THEIR POSSESSION OF DENSE MICROVILLI, ESPECIALLY THE PCT CELLS. 26 EXPLAIN THE MECHANISM OF TUBULAR SECRETION, AND EXPLAIN ITS IMPORTANCE IN THE URINE-FORMATION PROCESS. 1. BLOOD PLASMA CONTAINS RED-WHITE BLOOD CELLS, BLOOD PROTEINS, GLUCOSE, WATER, NITROGENIOUS WASTE AND SALTS. 2.

GLOMERULAR FILTRATE CONTAINS EVERYTHING BLOOD PLASMA DOES WITHOUT MOST OF THE BLOOD PROTEINS. 27 TRACE A DROP OF BLOOD FROM THE TIME IT ENTERS THE KIDNEY VIA THE RENAL ARTERY UNTIL IT LEAVES THE KIDNEY THROUGH THE RENAL VEIN. RENAL ARTERY -> SEGMENTAL ARTERY -> INTERLOBULAR ARTERY -> ARCUATE ARTERY -> CORTICAL RADIATE ARTERY -> AFFERENT ARTERIOLES -> GLOMERULUS -> EFFERENT ARTERIOLES -> PERITUBULAR CAPILLARY BED AND VASA RECTA -> ARCUATE VEIN -> INTERLOBULAR VEIN -> RENAL VEIN 28 29 DEFINE JUXTAGLOMERULAR APPARATUS REGION OF NEPHRON THAT PLAYS AN IMPORTANT ROLE IN FORMING CONCENTRATED URINE. CONSISTS OF JUXTAGLOMERULAR AND MACULA DENSA CELLS OF THE DCT.

30 TRACE THE ANATOMICAL PATHWAY OF A MOLECULE OF CREATININE (METABOLIC WASTE) FROM THE GLOMERULAR CAPSULE TO THE URETHRA. NOTE EACH MICROSCOPE AND/OR GROSS STRUCTURE IT PASSES THROUGH IN ITS TRAVELS. NAME THE SUBDIVISIONS OF THE RENAL TUBULE. GLOMERULAR CAPSULE -> PROXIMAL CONVULATED TUBULE -> LOOP OF HENLE -> DISTAL CONVULATED TUBULE -> COLLECTING TUBULE -> PAPILLARY DUCT -> MINOR CALYX -> RENAL PELVIS -> URETER -> BLADDER -> URETHRA 31 WHAT IS IMPORTANT FUNCTIONALLY ABOUT THE SPECIALIZED EPITHELIUM (TRANSITIONAL EPITHELIUM) IN THE BLADDER? THEY HAVE ABILITY TO SLIDE OVER ONE ANOTHER, THUS DECREASING THE THICKNESS OF THE MUCOSAL LAYER AS THE BLADDER FILLS & STRETCHES TO ACCOMMODATE THE INCREASED URINE VOLUME.

The Urinary System - Biology & Chemistry 123 with Professor at Stephen F. Austin State University - StudyBlue When urine leaves the kidney, it enters the ureter Urine formation initiates with glomerular filtration, a process that relies on filtering large quantities of protein free plasma into the Bowman's capsule by passive diffusion through porous capillaries The efferent arteriole carries blood from the glomerulus to the peritubular capillaries As urine moves through a nephron, it is modified by ions, water and other materials either being secreted into the fluid or by efflux of substances out of the urine. However, such modifications do not occur in this region of the nephron. Bowmans capsule Active transport of sodium out of tubular cells facilitates bulk movement of water toward the increased ion concentration triggers the movement of chloride ion toward the positively chargedsodium ions increases osmotic concentration in the tubular cell decreases the intracellular concentration of sodium, setting up a driving force for facilitated diffusion of sodium into the cell An individual has been diagnosed with persistent proteinuria. This condition is due to damage in which region of the nephron?

glomerular capsule Water and nutrients that have been filtered from the glomerular filtrate are returned to circulation as they enter the vasa recta and peritubular capillaries The hairpin design of the loop of Henle allows events on one side of the loop to influence the events on the other side, by a process referred to as countercurrent exchange Movement of sodium across the cells of the collecting duct relies on active transport The ______ are the major blood vessels transporting blood to the kidneys. renal arteries The outer part of the kidney is the _____. cortex Which of these is the functional unit of a kidney? nephron The major nitrogenous waste product in urine is uric acid. False Blood containing metabolic waste is transported to the kidney by the renal vein; the renal artery removes blood from the kidney once the waste has been removed. False The ureters connect the kidneys to the urinary bladder. True Osmotic concentration in the loop of Henle increses as NaCl as water moves out. True Impairments of the kidney that are considered short term and possibly can be overcome by medication or other treatments are called chronic renal failure.

False Chloride ions passively follow sodium that has been actively transported out of tubular cells, due to the attraction of negatively charged ions to positively charged ions. True Renin stimulates the secretion of aldosterone. False The internal urethral sphincter is composed of smooth muscle and the external urethral sphincter is composed of skeletal muscle; together, they control the process of urination. True Not only are the kidneys considered organs of excretion, but they have an endocrine function as well as an important role in the maintenance of homeostasis through the regulation of ion concentration. False Continuous ambulatory peritoneal dialysis involves the circulation of a patient's blood through an artificial kidney machine in order to remove metabolic waste and excess ions; this procedure can now be done in the home. False The movement of substances out of the glomerulus and into Bowman's capsule is referred to as _____. filtration The movement of substances from the blood into the proximal tubule is known as ____. secretion Which of these is reabsorbed from filtrate? sodium chloride water animo acids As filtrate moves down the loop of Henle, the surrounding interstitial fluid becomes _____ concentrated than the filtrate, so _____ leaves the filtrate.

more The most abundant solute in urine is ___. urea (and other nitrogenous wastes) Glucose is removed from filtrate by ____. active transport Under the influence of antidiuretic hormone (ADH), _____ is produced. more concentrated urine Antidiuretic hormone (ADH) makes the ____ permeable to water. collecting duct Waste products that contain nitrogen are produced by cells as they metabolize ______. proteins Counter current exchange is used primarily in the ___ portion of the nephron. loop of Henle Urine is moved through the ureter to the bladder by muscular contractions known as ____. peristalis Each kidney is made up of a million ____, the functional units of a kidney. nephrons The glomerulus of each nephron is enclosed by a portion of the nephron known as ______. Bowmans capsule Nutrients, water, and ions reabsorbed by the proximal and distal tubules enter the ______ capillaries. peritubular ADH ______ the permeability of the cells of the collecting duct to water. increases The steroid hormone ____ regulates the reabsorption of sodium across the collecting duct and distal tubule.

aldosterone Three organs in the human body are involved in the production of vitamin D; they are the ____, _____, and _____. skin, liver and kidneys The filtrate flows into which region of the nephron after it leaves the proximal tubule? loop of Henle Two-thirds of the water and electrolytes that were filtered out of the blood are returned back into the blood from which part of the nephron? proximal tubule What is the role of ADH in water reabsorption? ADh causes the collecting duct to become more permeable to water When referring to the osmotic gradient in the loop of Henle, we can say that _____. the osmolarity is lower towards the cortex and higher toward the medulla Which of the following is a reason that glomerular filtration works? The pressure in the capillaries is relatively high. The cells surrounding the glomerulus have slits. The glomerular capillaries have pores. Which blood vessel delivers blood directly to the glomerulus for filtration? afferent arteriole Which of the following is a function of the kidneys?

Maintaining water balance, to control blood volume and pressure Control red blood cell production Activate vitamin D Which of the following terms is included in the nephron? Proximal tubule Antidiuretic hormone (ADH) increases the reabsorption of water in the _____. collecting duct A diuretic is any substance that increases the formation and excretion of urine. True Urination is controlled by the operation of two sphincter muscles, both of which are made of smooth muscle fibers and are voluntarily controlled. False Formation of urine involves filtration, reabsorption and secretion, all of which are done by the bladder. False Erythropoietin is secreted by the kidneys in response to an increase to an increase in blood oxygen levels. False The distal tubules deliver urine to the renal pelvis. False Antidiuretic hormone (ADH) and aldosterone both help to control the composition of urine. True Protein is typically part of the glomerular filtrate. False The descending limb of the loop of Henle is impermeable to water. False The kidneys produce urine, maintain water balance, and regulate salt balance. True The filtering unit of the kidneys is called a neuron.

False 65-70% of the water in the glomerular filtrate is reabsorbed into the blood here. proximal tubule Region where fluids are transported to the collecting duct; active reabsorption of salt occurs here. distal tubule Region composed of a descending limb that is permeable to water and an ascending limb that is impermeable to water. loop of Henle ADH increases the permeability of the cells of this region to water collecting duct Region where blood plasma fluid is filtered from the blood into the nephron glomerular capsule Condition that results from short-term damage to the kidney and is usually correctable; can be caused by low blood pressure, infections, or severe injuries Acute Renal Failure Condition also know as end-stage renal disease; kidneys no longer function properly due to long-term, irreversible damage Chronic Renal Failure Condition that results from crystallization of minerals in urine; can block the flow of urine out of the body Kidney Stones Functions of the Urinary System: Functions of the kidneys and other parts of the Urinary System of the Human Body.

Public health nursing in the UK - 3 Mar 2016 Functions of the Human Urinary System Note: Other terms used to refer to the " Urinary System " include the "Renal System" and the "Genito-urinary System". Each part of the urinary system performs important functions - both for the efficient operation of the urinary system itself, and also therefore, for the body as a whole. Functions of the Kidneys: Regulation of blood volume: The kidneys conserve or eliminate water from the blood, which regulates the volume of blood in the body. Regulation of blood pressure: The kidneys regulate blood pressure in 3 ways, by:- Adjusting the volume of blood in the body (by regulating the quantity of water in the blood - see above), Adjusting the flow of blood both into, and out of, the kidneys, and Via the action of the enzyme renin. The kidneys secret renin, which activates the angiotensin-aldosterone pathway. Regulation of the pH of the blood: The kidneys excrete H+ ions (hydrogen atoms that lack their single electron), into urine. At the same time, the kidneys also conserve bicarbonate ions (HCO3-), which are an important buffer of H+.

Regulation of the ionic composition of blood: The kidneys also regulate the quantties in the blood of the ions (charged particles) of several important substances. Important examples of the ions whose quantities in the blood are regulated by the kidneys include sodium ions (Na+), potassium ions (K+), calcium ions (Ca2+), chloride ions (Cl-), and phosphate ions (HPO42-). Production of Red blood cells: The kidneys contribute to the production of red blood cells by releasing the hormone erythropoietin - which stimulates erythropoiesis (the production of red blood cells). Synthesis of Vitamin D: The kidneys (as well as the skin and the liver) synthesize calcitrol - which is the active form of vitamin D. Excretion of waste products and foreign substances: The kidneys help to excrete waste products and foreign substance from the body by forming urine (for release from the body). Examples of waste products from metabolic reactions within the body include ammonia (from the breakdown of amino acids ), bilirubin (from the breakdown of haemoglobin), and creatinine (from the breakdown of creatine phosphate in muscle fibres).

Examples of foreign substances that may also be exceted in urine include pharmaceutical drugs and environmental toxins. Functions of the Ureters: There are two ureters, one leading from each kidney to the urinary bladder. Each of these transports urine from the renal pelvis of the kidney to which it is attached, to the bladder (see diagram on the page about components of the urinary system ). Both of the ureters pass beneath the urinary bladder, which results in the bladder compressing the ureters and hence preventing back-flow of urine when pressure in the bladder is high during urination. This prevention of back-flow is important because when it is not operating correctly cystitis, which is inflammation of the ureter / urinary bladder, may develop into a kidney infection. Functions of the Bladder: The purpose of the urinary bladder is to store urine prior to elimination of the urine from the body. The bladder also expels urine into the urethra by a process called micturition (also known as urination). Micturition involves the actions of both voluntary and involuntary muscles. Lack of voluntary control over this process is referred to as incontinence.

Functions of the Urethra: The urethra is the passageway through which urine is discharged from the body. In males the urethra also serves as the duct through which semen is ejaculated (see the section about reproduction for further detail about this function). Quick Summary: The Functions of the Urinary System The kidneys regulate blood volume and composition, help to regulate blood pressure and pH, participate in red blood cell production and synthesis of vitamin D, and excrete waste products and foreign substances. The ureters transport urine from the kidneys to the urinary bladder. The urinary bladder stores urine and expels urine into the urethra, The urethra discharges urine from the body. Today's Study Tip: How much of this topic can you describe and explain using diagrams or flow charts ? - 20th January 2017. Also on this website: Home Adel K. Afifi, MD, MS Ryosuke Miyauchi, MD Peer Review Status: Internally Peer Reviewed Renal artery variations including their number, source, and course are very common. Irregularites of the renal vessels are found in about 35% of cases studied. The most common is the presence of an additional vessel (~28%).

So-called accessory arteries arising above the usual trunk is more frequent than one arising below. Supernumerary vessels are more frequent on the left side than the right. It is not only ludicrous but dangerous to suggest that the kidneys each receive only a single artery. This is commonly stated and shown in illustrations in textbooks of anatomy used by professional students of medicine and the allied health sciences. This could be easily rectified in a single sentence such as, "The kidneys may receive a single artery athough each organ may equally be supplied by as many as six end arteries." The details follow. The right and left renal arteries may arise from the aorta by a common stem. They may arise from the aorta at a lower point than usual, in which case the kidneys lie below their usual position. There may be several renal arteries on each side, or the renal artery may divide, close to its origin, into several branches. The renal artery on one or both sides may arise from the bifurcation of the aorta or from the common iliac, internal iliac, inferior mesenteric, middle sacral, or from a common intercostal-renal trunk. The right artery may cross in front of, instead of behind, the vena cava.

Branches of the renal artery may "perforate" the substance of the kidneys instead of entering from the hilus (so called accessory branches.) The renal artery may give rise to branches normally derived from other vessels, such as the inferior phrenic, hepatic, right renal, middle and inferior suprarenals, gonadal, pancreatic, some of the colic arteries, and one or more of the lumbar arteries. "Accessory renal arteries," varying in size and generally derived from the aorta, are common (26 to 30% of all reported kidneys studied), and may enter the kidneys at almost any point. It is a misnomer to call such vessels accessory renal arteries because they are not extra but essential, tissue-sustaining arteries and cannot be ligated without dire cosequences. Frequently, the renal arteries provide two to five slender branches to the suprarenal gland, whereas the inferior suprarenal arteries coming from the aorta or the renal arteries often supply one to four branches (capsular branches) to the superior pole of the kidney and its fat body.

The inferior phrenic artery sometimes also supplies an "accessory renal artery." A study of the arterial supply of the kidney (composite of 45 authors and 10,967 kidneys) demonstrated the following: Single artery to each kidney, 72% (SD 2.51; one artery with a single upper polar branch, 12.6% (412 of 3269 cases); two arteries, 11% (530 of 4901 cases); one hilar and one upper aortic polar branch, 6% (211 of 3384 cases); one hilar and one lower aortic polar branch, 3% (115 of 3674 cases); three arteries 1.7% (70 of 4019 cases); and two arteries, one with an upper polar branch, 2.7% (37 of 1370 cases.) Quain reported that three arteries occur in 3% of cases. The inferior suprarenal arteries (one to three), which occur bilaterally, are constant branches of the single renal artery.

An inconstant, but frequent (from 16 to 22% of cases depending on author) branch is the gonadal (ovarian or testicular) artery, a component of the renal pedicle. The inferior phrenic is another inconstant branch sometimes arising from the right renal artery or from an aortic superior renal polar artery. Because the inferior phrenic often supplies most or all of the blood to the suprarenal gland it must be identified and saved when surgery is performed on the renal pedicle to avoid dire circumstances. In one study the renal arteries were reported to be located between the lower third of the first lumbar vertebra and the cranial third of the second lumbar vertebra. The right and left renal arteries were reported to be at the same level in about 30% of cases, while the right was higher in 47% and the left was higher in about 23% of cases. A single renal artery on one side and multiple (two, three, or four) renal arteries on the other is not unusual. There were no reported sex (gender) or race related differences. The right renal artery is longer than the left and usually courses behind the inferior vena cava.

When multiple renal arteries are present, the more caudal arteries often take a precaval course. The right renal artery, from aortic origin to its division point, can measure 0.5 - 8 cm long; the length of the left can vary from 0.5 - 6 cm. In most cases, a single renal artery divides into anterior and posterior trunks; that division might occur anywhere along the artery's course to the kidney hilum. Precocious (near to its origin) division may be interpreted - erroneously, as dual or even multiple renal arteries. Most commonly, there are four branches, but there can be two to five entering the parenchyma of the organ. Based upon their relationship to the renal pelvis (that is, on whether they represent anterior or posterior divisions of the artery), these branches have been termed the anterior superior, anterior medial, anterior inferior, and a fourth branch that usually runs posterior to the renal pelvis, the retropyelic branch. The kidney has been shown to be composed of five segments, i.e., apical, upper, middle, lower and posterior.

The three terminal branches of the anterior division of the renal artery are usually referred to as the upper, middle, and lower segmental (terminal) branches; the fourth (posterior) branch supplies the posterior segment. The apical segment of the organ is usually supplied by the anterior division, but in 10% of cases the posterior branch may also supply an apical artery. According to Crelin, Eustachius made the first copperplate engraving illustrating a renal artery variation in 1564. Lancisi published the engravings with commentary in 1714 and referred to the variation as a "lusus naturae" (sport of Nature). The artery was related, but not identical, to Crelin's case. In Crelin's case, the artery arose from the right internal spermatic (gonadal) artery, 6 cm above the internal (abdominal or deep) inguinal ring. So-called "accessory" or "supernumerary" renal arteries are present in about 30% of cases (based on a composite of 45 studies and 10,967 kidneys).

These vary in number from two to four, although there may be, rarely, five or six, arranged either unilaterally or bilaterally. In 16% of subjects, there was variation in the number of renal arteries between kidneys in the same subject. Accessory renal arteries can arise from the aorta as high (superiorly) as the diaphragm or as low (inferior) as the internal iliac artery. A study by Sykes suggests, "a superior accessory artery is a separate apical artery and an inferior accessory artery is a separate lower segmental artery." Doubled renal arteries occur in 10% of cases (based on 10,967 kidneys studied). They may be side by side, one in front of the other, or spaced so that they enter the kidney at opposite ends of the hilum. In cases of doubled renal arteries, there may be a primary aortic hilar renal and an anterior or posterior division (vessel) or a renal polar artery. Very rarely, the lower renal arises near the aortic bifurcation or from the common iliac.

Sometimes one of the arteries passes in front of or behind the renal pelvis; the upper may cross the lower the lower renal and ureteropelvic junction to enter the inferior pole of the kidney. In 1 - 2% of cases, three hilar renal arteries are derived from the aorta. The typical pattern for triple renal arteries is that two are hilar (of aortic origin) and the third is a superior or a lower renal polar branch. The superior or the intermediate of the three renals may supply a superior renal polar or a suprarenal branch. The inferior vessel may provide a gonadal (ovarian or testicular) or inferior renal polar. The presence of four renal hilar arteries derived from the aorta is rare. This pattern arises from the aorta between the superior and inferior mesenteric arteries. The upper two vessels may have a postcaval course and the two lower may pass in front of the inferior vena cava. The upper two may pass in front of the renal pelvis and the lower two behind it. Quadruple renals may exist as two hilar and two polar, three hilar and one polar, or one hilar and three polar renal arteries.

Usually only one of these is large and the others are smaller and distributed to the superior or inferior extremities of the kidney. "Accessory renal" arteries usually arise from the aorta, but they may also arise from: suprarenal celiac artery, superior mesenteric, inferior mesenteric, common iliac, middle sacral, or from the external iliac artery. Poynter found, "no frequency differences in renal anomalies between the two sides, with the number of bilateral conditions constituting about half the cases, there were no sex differences, and with no relation between supernumerary arteries and veins; the latter being the rarer anomaly". Poynter also noted the wide discrepency in textbooks as to the frequency of multiple renal arteries and noted that 1883 specimens yielded 456 cases of multiple renal arteries and that individual investigators (Poynter cited 10 individuals) reported frequencies of 14 to 59% in the 465 of cases studied. Variations of the Blood and Lymphatic Supply of the Kidney Arteries: Anatomy Atlases is curated by Michael P. D'Alessandro, M.D. and Ronald A.

Bergman, Ph.D. Please send us comments by filling out our Comment Form . All contents copyright © 1995-2017 the Author(s) and Michael P. D'Alessandro, M.D. All rights reserved. "Anatomy Atlases", the Anatomy Atlases logo, and "A digital library of anatomy information" are all Trademarks of Michael P. D'Alessandro, M.D. Anatomy Atlases is funded in whole by Michael P. D'Alessandro, M.D. Advertising is not accepted. Your personal information remains confidential and is not sold, leased, or given to any third party be they reliable or not. The information contained in Anatomy Atlases is not a substitute for the medical care and advice of your physician. There may be variations in treatment that your physician may recommend based on individual facts and circumstances. URL:

Question: Which part of the human body is referred to by the adjective, renal?
Answer: THE KIDNEYS