Medicine
hemoglobin , respiratory protein found in the red blood cells (erythrocytes) of all vertebrates and some invertebrates. A hemoglobin molecule is composed of a protein group, known as globin, and four heme groups, each associated with an iron atom. In the lungs, each iron atom combines reversibly with a molecule of oxygen. Each hemoglobin molecule also has attached a single cysteine amino acid, which attracts nitric oxide from the lungs. The enriched hemoglobin circulates and is carried through the body to the tissues, where the nitric oxide dilates the small capillaries, allowing hemoglobin to deliver its oxygen to the tissues. Then the oxygen- and nitric oxide-free hemoglobin molecule picks up carbon dioxide and free nitric oxide and transports both back to the lungs, where they are exhaled as waste. Hemoglobin is produced in bone marrow by erythrocytes and is circulated with them until their destruction. It is then broken down in the spleen, and some of its components, such as iron, are recycled to the bone marrow. Other components, such as the heme groups, are broken down into bilirubin, transported to the liver, and secreted with the bile into the intestine for eventual elimination from the body. Hemoglobin deficiency may be a result of structural abnormality in the hemoglobin molecules themselves. In sickle cell disease , this structural abnormality creates malformed red blood cells which clog blood vessels, severely restricting the supply of blood flowing...
nervous system network of specialized tissue that controls actions and reactions of the body and its adjustment to the environment. Virtually all members of the animal kingdom have at least a rudimentary nervous system. Invertebrate animals show varying degrees of complexity in their nervous systems, but it is in the vertebrate animals (phylum Chordata , subphylum Vertebrata) that the system reaches its greatest complexity. Anatomy and Function In vertebrates the system has two main divisions, the central and the peripheral nervous systems. The central nervous system consists of the brain and spinal cord . Linked to these are the cranial, spinal, and autonomic nerves, which, with their branches, constitute the peripheral nervous system. The brain might be compared to a computer and its memory banks, the spinal cord to the conducting cable for the computer's input and output, and the nerves to a circuit supplying input information to the cable and transmitting the output to muscles and organs. The nervous system is built up of nerve cells, called neurons, which are supported and protected by other cells. Of the 200 billion or so neurons making up the human nervous system, approximately half are found in the brain. From the cell body of a typical neuron extend one or more outgrowths (dendrites), threadlike structures that divide and subdivide into ever smaller branches. Another, usually longer structure called the axon also stretches from the cell body. It sometimes...
heart muscular organ that pumps blood to all parts of the body. The rhythmic beating of the heart is a ceaseless activity, lasting from before birth to the end of life. Anatomy and Function The human heart is a pear-shaped structure about the size of a fist. It lies obliquely within the chest cavity just left of center, with the apex pointing downward. The heart is constructed of a special kind of muscle called myocardium or cardiac muscle, and is enclosed in a double-layered, membranous sac known as the pericardium. A wall of muscle divides the heart into two cavities: the left cavity pumps blood throughout the body, while the right cavity pumps blood only through the lungs. Each cavity is in turn divided into two chambers, the upper ones called atria, the lower ones ventricles. Venous blood from the body, containing large amounts of carbon dioxide, returns to the right atrium. It enters the right ventricle, which contracts, pumping blood through the pulmonary artery to the lungs. Oxygenated blood returns from the lungs to the left atrium and enters the left ventricle, which contracts, forcing the blood into the aorta , from which it is distributed throughout the body. In addition, the heart employs a separate vascular system to obtain blood for its own nourishment. Two major coronary arteries regulate this blood supply. Cardiac Cycle Blood flows through the heart in one direction only. It is prevented from backing up by a series of valves at various openings: the...
The history of medicine can be traced back as far as Neolithic man, but our understanding of medicine began with the Sumerians. Our knowledge of anatomy began with the Greeks, but truly took hold during the Middle Ages. Modern medicine can be traced back to discoveries made in the 17th century. That’s when William Harvey demonstrated the circulation of blood in the body, quinine was used to treat ... Read more
malaria, the compound microscope was developed, and the capillary system was discovered.Today, we’ve built on many of those early discoveries in our understanding of cell biology, genetics and microbiology. Research today focuses on preventing diseases like heart disease, tuberculosis, and AIDS, while also discovering cures and treatments for cancer. We also have a greater understanding of pathogens, or microorganisms, like bacteria and viruses that cause most diseases.
The genome project is also helping us understand disease and the human body on a genetic level and led to genetic engineering, which is used to develop pharmaceuticals and new approaches to cancer treatment.
Modern medicine also has given us pharmacology, allowing medical professionals to treat a host of diseases. From acetaminophen, which can treat a headache, to immunosuppressive drugs, which aid in organ transplantation, this growing field offers a multitude of new and effective drugs.
Psychology and psychiatry have also changed much since these sciences first began. People with disorders were often cast away from society or, later, placed in asylums and not treated. Today, psychiatry involves the treatment of many disorders and can involve both physiological and psychological treatments.