Biomedicine and Health: Human Gross Anatomy
Biomedicine and Health: Human Gross Anatomy
Understanding human anatomy is vital for physicians, because without it, disease cannot be understood. Gross anatomy refers to those characteristics that can be observed without the aid of a microscope. It is one of the first courses that medical students take upon entering medical school. The major activity of this course is usually the dissection of a human cadaver, although there are many detailed anatomy books and other information available.
Gross anatomy can be studied using two contrasting approaches. The regional method explores a particular area as a whole, describing all the structures present. The systematic method deals with each bodily system individually. Using the regional approach, a student might study the anatomy of the chest, noting the heart, lungs, blood vessels, bone structure, and the connections between all of them. The systematic method would divide these features into their major systems: the circulatory, respiratory, and skeletal systems. Each would then be studied individually, before moving on to investigate their interplay.
Historical Background and Scientific Foundations
The earliest known medical text is an Egyptian book known as the Edwin Smith Surgical Papyrus. Dated to the seventeenth century BC, it shows an already-advanced state of medical knowledge. Although the book deals mostly with surgical treatment for traumatic injuries, the scientific accuracy and systematic approach to treatment show that the author knew a good deal about anatomy for his time. Although errors are present, the papyrus recognizes many organs, including the heart, kidneys, and brain. It also understands that the blood vessels are connected to the heart, but expressed no knowledge of their true function.
Many ancient Greek philosophers were interested in the composition of the human body, particularly where the site of intelligence was located. Early opinion on this was divided between the head and the heart, with Alcmaeon of Croton (fl. fifth century BC) arguing for the head. Alcmaeon himself was limited by the subjects available for dissection. Religious and social taboo prevented most autopsies of humans, so he and many physicians following him had to rely on the use of animal subjects.
Ironically, the prohibition against human autopsy may have lead to some even more gruesome investigations. In the fourth century BC, Alexandria, Egypt, was the center of learning and culture in the Greek world. The physicians Herophilus (335–280 BC) and Erasistratus (304–250 BC) undertook vivisections of condemned criminals as well as dissection of dead human corpses. Herophilus is credited with developing the terminology of anatomy and assigning consistent names to body parts. Erasistratus was interested in the function of organs and structures, describing the heart as a pump. Although their approach was systematically designed to answer their questions about human anatomy, the cruel nature of live vivisections assured that they were rarely repeated.
The rise of the Roman Empire led to a general decline in the Greek world, including the fields of medicine and anatomy. Although the Romans greatly respected Greek knowledge and culture, they also dominated and stifled it in many ways. One of the restrictions that inhibited the study of anatomy was the official legal prohibition against human autopsy. Roman culture was also subtly biased against medical scholarship, instead encouraging their best minds into lives of politics, oratory, and military glory. Medicine was left to the subjugated Greeks, whose intellectual heritage had waned under Roman rule.
However, the Romans were not totally bereft of medical scholars. Galen (AD 129–c.219), a Romanized Greek from Asia Minor living in the second century AD, was to become the most revered medical scholar in the western world for at least a thousand years. Still relying on animal dissections, Galen's favorite subjects were monkeys for their close resemblance to humans. Many of Galen's discoveries were sound, though many were in error and took hundreds of years to correct. But it was Galen's greatest advocates who slowed the progress of anatomical science almost to a halt, not Galen himself. As innovation turned to orthodoxy, new physicians were almost never encouraged to observe for themselves. If they even witnessed autopsies, they were done by a professor or uneducated barber/surgeon.
After the decline of the Roman Empire, the study of medicine and anatomy went into decline in the west. Scholarship as a whole did not flourish in the medieval ages, and much knowledge was lost. Galen continued to be the most respected medical authority in Europe, but in the Arab world, scholars were questioning and improving upon his work. The Persian physician and polymath known as Avicenna (AD 980–1037) was known for his critiques and corrections of Galen. After Avicenna, physicians Avenzoar (1091–1161) and Ibn al-Nafis (1213–1288) learned a great deal about human anatomy through legal public autopsies. Ibn al-Nafis revolutionized the study of anatomy by revising and correcting much of the accepted understanding up to that day. Avicenna's work was used in Europe and the Middle East for centuries, and for a time represented the best medical knowledge available.
With the Renaissance, the study of anatomy experienced resurgence in Europe. Much of the renewed interest in anatomy still came from physicians, particularly since authorities were slowly legalizing the practice of autopsy. However, medical knowledge was also stimulated by one of the most powerful cultural forces of the Renaissance: art. As artists focused on increasing the realism of their work, many became interested in human anatomy. This interest in anatomy is particularly visible in the work of Michelangelo Buonaratti (1475–1564), whose muscular figures are prominent in famous works such as the Sistine Chapel ceiling and the sculpture of David. Leonardo da Vinci's (1452–1519) interest in anatomy is also well known. Not only did he use his knowledge in his art, but he studied anatomy extensively in his personal notebooks.
The most famous physician-anatomist of the Renaissance is Vesalius (1514–1564), a Belgian who worked in Italy as well as for the Holy Roman Emperor Charles V (1500–1558). Vesalius conducted many dissections and advocated them as the most important way for physicians to learn their skills. Using his knowledge and collaborating with professional artists, he assembled a revolutionary book on anatomy that presented the body and its parts as a three-dimensional system of interconnected parts. Vesalius' work can be viewed as a turning point in the study of anatomy, leading directly to the more advanced understandings of today.
When many people think of the subject of anatomy, one of the few familiar cultural references is the classic book known as Gray's Anatomy. Originally published in the United Kingdom in 1858 by British anatomist Henry Gray (1827–1861), it has been continually in print since then, though it has undergone dozens of updated editions. The latest, the 39th edition, was published in 2004. The book is organized around the systematic approach to human anatomy. The human body has many organ systems, the organization of which sometimes differs among experts. The systems are grouped together by common function; with emphasis on the wider perspective that each system does not operate independently, but in concert with other systems.
The musculoskeletal system serves to support the body and provide it with mobility. One major part of this system is the bones, many of which start as small sub-units and fuse into larger structures upon maturity. Cartilage is a smooth, dense tissue that cushions joints and connects various structures in the body. It also makes up the ears and nose. Tendons and ligaments
connect bones and muscles to other structures in the body. They can transfer movement or give support to body parts. The skeletal muscles are also part of the musculoskeletal system and are the principal engines by which the body is able to move itself.
The heart and the blood vessels make up the circulatory system. It is important to note that while the heart is a muscle, it is of a type known as smooth muscle. This is different than the kind of muscle in the musculoskeletal system; smooth muscle cannot be voluntarily controlled. The blood vessels form a complex network that reaches all parts of the body, providing oxygen and energy to every cell. There are two major types of blood vessels: arteries and veins. Arteries transport fresh, oxygenated blood from the heart to the body. They are under great pressure from the beating of the heart and must be tougher than veins. Veins return blood to the heart and lungs to pick up new oxygen. Blood vessels vary greatly in size, with the largest vessels, such as the aorta, nearest the heart and the smallest capillaries furthest away.
Although the blood system is not part of the circulatory system, it is intimately involved with it. Consisting of blood cells, plasma, the spleen, thymus, and bone marrow, the blood system creates, maintains, and destroys components of the blood. The many different kinds of blood cells perform many different functions. Red cells carry oxygen, white cells mount immune defense, and platelets aid in clotting. Blood cells are formed in the bone marrow and then are suspended in the plasma to form blood. The thymus is a small, obscure organ that matures the blood cells and destroys inferior cells. When blood cells are old or damaged, they are destroyed by the spleen.
The human respiratory system consists of all the organs and structures which take in air, transport it, and transfer the oxygen to the blood. This includes the mouth and nose, the pharynx, larynx, trachea, bronchi, and lungs. The larynx, the organ of speech, is situated in the throat, allowing the vocal cords to vibrate when air passes over them.
The nervous system consists of the brain, spinal cord, and nerves. The nervous system transports signals from the brain to all parts of the body. Some of these signals are voluntary, as in most forms of motion, while others are involuntary, such as the movements of the digestive system. The nervous system allows the body to feel sensations, including pain. It also sends, transports,
and processes the signals that coordinate the body's life functions.
The digestive system takes in food, processes it, makes energy available, and excretes waste. The mouth, esophagus, stomach, intestines, rectum, and anus can be thought of as a tube through which food passes and in which it undergoes the process of digestion. Each successive part acts on the food further; when
it is exhausted, it is excreted. The liver, pancreas, and gallbladder produce substances that aid in digestion. The liver also plays a role in removing waste from the body. Liquid waste is excreted through the urinary system, via the kidneys and bladder.
The endocrine system, composed of the glands and organs that produce hormones, is another communication system in the body. Hormones such as insulin, growth hormone, melatonin, and estrogen tell the body how to metabolize energy, sleep, and grow, among many other functions.
The reproductive system is one of the only body systems that differs significantly between males and females. The male reproductive system is concerned with the production, maturation, and delivery of sperm cells. This process starts in the testes, and the sperm travel through the seminal vesicles and penis. The prostate gland produces substances that protect and sustain the sperm. In contrast, the female reproductive system does not produce new sex cells after its embryonic development. The ovaries contain immature ova, which ripen, travel down the fallopian tubes, and into the uterus. If the ovum is fertilized, the uterus contains it until birth, when the cervix opens and the baby is expelled through the vagina.
Physicians and medical researchers continue to learn more about basic human anatomy, though a great deal is already known about the subject. Much of this new information is refinement of currently accepted knowledge. Though new discoveries are always possible, centuries of systematic exploration have left us with a good understanding of those parts visible without the aid of microscopes. A great deal of new information is being discovered in the field of microscopic anatomy, as well as about the interplay between the classic organ systems.
Modern Cultural Connections
In 1995, an exhibit in Tokyo called Body Worlds, which contained preserved human bodies that had been dissected to reveal their inner anatomical structures, resulted in a growing worldwide cultural phenomena. Today, more than 20 million people around the globe have seen one of the Body Worlds exhibits. Featuring organs, tissues, and entire bodies, the exhibit features detailed anatomical structures that are revealed through a process called plastination, in which body fluids are replaced with liquid reactive plastics that are then cured through heat, gas, or other processes. The technique allows for bodies to be preserved in true-to-life poses that display the integration of muscular, skeletal, organ, and circulatory systems in an open area for up-close viewing without the need for a glass barrier. A pregnant woman reclining with the fetus visible, a chess player, a jumping dancer, and a smoker are among the group in the collection.
The plastination process was invented by the German anatomist Gunther von Hagens in 1977. Although Hagens created the Body Worlds exhibits from donors who gave their consent for their bodies to be used for the exhibition, Body Worlds is not without controversy. Some religious groups object to the public display of deceased humans, and other groups have accused Hagens of sensationalism by displaying humans in situations that would not occur naturally (for example, in one exhibit, a man is shown carrying his own heart). Medical boards in the United States that normally regulate how human cadavers are used for educational purposes have pointed out a lack of oversight for bodies from international sources that ultimately end up on public display. Ethics groups have also raised concern about the display of human bodies where profits are made or for artistic purposes. School districts in some areas are sponsoring trips for students to see the exhibit, while the exhibit material is deemed inappropriate for schoolchildren in other districts.
Hagens maintains that the purpose of Body Worlds is to educate the public about human anatomy and how it is affected by both healthy living and disease. Four different Body Worlds exhibitions are currently on tour in science museums throughout the world. Since the inception of Body Worlds, several exhibits using the same methods of plastination and types of displays have created competition for Body Worlds.
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