Thursday, April 3, 2008

How Medical Innovation Happen

Charlie Rose talks to Dr. Patrick Walsh- Dr. Walsh was honored as the 2007 National Physician of the Year for Clinical Excellence by America's Top Doctors and authored the best-selling book Guide to Surviving Prostate Cancer

Excerpts from the book on anatomy crash course;

The testes: The testes, or testicles, are a man's reproductive organs: They make the hormone testosterone, as discussed above. They also make sperm, in hundreds of tiny tubes and threadlike, winding tubules. (If these miniature pipes were straightened out, each would stretch to a length of two feet.) There are two testes, each less than two inches long and about an inch wide. The testes, attached to blood-supplying lifelines called spermatic cords, are covered by the scrotum. Have you ever wondered why the scrotum is suspended in such a vulnerable position, below the body? Wouldn't it make more sense-and provide better protection—if the testicles were inside the body? Yes and no. If the testes were tucked away inside the pelvis, they would indeed be better protected-but there wouldn't be much to protect. The testes are located in the scrotum for the simple but expedient reason that it's a more temperate climate down there, by a couple of degrees. Sperm are delicate; they fare poorly when the temperature is too warm. The scrotum, in effect, is nature's cooler. (In fact, men who have undescended testicles-which are located inside the abdomen—cannot develop sperm because the normal body temperature is just too hot.)

The epididymis: The sperm-making tubules in each testis converge to form the epididymis. Compared to the tubules, this is a river, as large and serpentine as the Amazon: Each tubule (one on each side), though only a millimeter wide, could be uncoiled to reach a remarkable length of fifteen to twenty feet. This is one continuous tube—thus, it's easy to see why an infection here could cause scar tissue and blockage that would result in infertility. These tubules are packed side by side, top to bottom, to form the epididymis, an elongated structure about the size of a woman's pinky finger. This is the greenhouse where sperm mature until orgasm, when they shoot from the tail of the epididymis during a series of powerful muscle contractions. The epididymis clings to one side of each testis before turning yet again and heading upward to meet still another tube, called the vas deferens.

The vas deferens: This impressive tube (again, one on each side; together they are called the vasa deferentia), now grown to 3 millimeters in diameter, is a hard, muscular cord, about 18 inches long. Its job is to pump sperm to the part of the urethra that lies within the prostate (the prostatic urethra). Because it is so thick, it can easily be palpated through the scrotum. (It can also be cut easily, in an outpatient procedure—a form of male birth control-called a vasectomy. When the cord is cut, sperm cannot exit the penis through ejaculation, and instead are reabsorbed by the body.) The vas deferens travels to a space between the bladder and rectum, then courses downward to the base of the prostate, where it meets with the duct of the seminal vesicle to form the ejaculatory duct.

The seminal vesicles: The lumpy seminal vesicles, each about 2 inches long, sit behind the bladder, next to the rectum, hanging over the prostate like twin bunches of grapes. Arching still higher over them, on either side, are the vasa deferentia, which meet the seminal vesicles at V-shaped angles; these form the ejaculatory ducts, slitlike openings that feed into the prostatic urethra. The seminal vesicles are made up of caves called alveoli, which make sticky secretions that help maintain semen's consistency. (The vesicles got their name because scientists used to believe they stored sperm; they don't.) Like the prostate, the seminal vesicles depend on hormones for their development and growth, and for the secretions they produce. However: Although the seminal vesicles are strikingly similar to the prostate in many ways, they're almost always free of abnormal growth-benign (as in BPH) as well as malignant.

The penis: The penis-an engineering marvel built of nerves, smooth muscle, and blood vessels—has two main functions—sexual intercourse and urination. (Note: There is no bone in the human penis, although this is not the case in dogs and some other animals.) The penis works like a water balloon. Its basic structure is that of a rounded triangle; all three corners have cylinders of tissue (called the corpora cavernosa and the corpus spongiosum) that fill and become engorged with blood. In erection, as arteries pump a steady supply of blood into the penis, the veins (which normally pump it back out again) clamp down—so the blood can't recirculate, thus keeping the penis "inflated" during sexual activity. All of this is made possible by the delicate nerves that lead to and from the penis. For years, these tiny nerves were poorly understood. The sad result was that removal of the prostate almost always meant impotence. That is no longer the case.

The kidneys are the body's main filters. With each heartbeat, they cleanse the blood of toxic wastes, excess water and salts, and (among many other chores) help maintain the body's balance of fluids and minerals. With more than a million tiny, wadded-up filters called nephrons, the kidneys sift through an incredible volume of fluid—about 45 gallons a day for a 150-pound man. (See Fig. 1.5.) Every sip of water we drink is refined, reabsorbed, and then processed again. (If the water and minerals weren't reabsorbed, our bodies would become seriously dehydrated within hours.) Not all of this material returns to the body, however; much of it passes out as urine. Every day, the average man excretes about two quarts of urine (a concentrated mixture of water, sodium, chloride, bicarbonate, potassium, and urea, the breakdown product of proteins).

Urine exits each kidney through a pipeline called the ureter. The ureters work like toothpaste tubes, squeezing or "milking" urine from the kidneys. Each ureter is about a foot long, and narrow—less than a half-inch wide at its broadest point. Ureters are one-way streets: Urine always flows the same way through them—straight toward the bladder.

The bladder is a big bag. Stretched to its fullest, this muscular tank can hold about a pint of urine. Unlike the kidneys and ureters, the bladder-in normal circumstances-allows us some voluntary control; it generally obeys our decision to eliminate or hold urine. (The inability to control urination is called incontinence.) With intricately woven layers of muscle and connective tissue, the bladder can collapse or expand, depending on the amount of fluid it's asked to hold at a given time. A sophisticated backup system protects the bladder from extreme distention and the risk of rupture: When the bladder is very full, it signals the kidneys to slow down the production of urine. At the neck of the bladder is a gate called the trigone. The purpose of the trigone is to make sure urine flows only one way-downward, away from the ureters and kidneys. The trigone's valve makes a tight seal that prevents urine from backing up into the kidneys, even when the bladder is distended.

Related Books;
How Doctors Think by Jerome Groopman

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