First of a two-part column
Your heart is spectacular
Your heart is your most important muscle. It is what keeps you alive. It starts working when you are a developing fetus and never stops. It works 24 hours per day, seven days a week for you and runs for an entire lifetime.
Your heart beats 100,000 times per day! That means it beats over two billion times in a lifetime. There are about five liters of blood in our bodies. The heart beats and circulates that blood at a rate of pumping 2,000 gallons per day! That is over 50 million gallons in a lifetime, enough to fill almost eight Olympic swimming pools. Now that is one durable muscle!
Saliva is special
Saliva is produced by special glands in the mouth. Saliva is very important because it:
- keeps the mouth moist
- keeps teeth clean and free from decay
- starts the digestion process
- enables us to taste food
Our body produces about one ounce of saliva per hour, or three cups of saliva per day, or almost 5,000 gallons in a lifetime.
Women are more sensitive to cold than men
Women, on average, have a slightly higher core temperature than men. As a result, women are more sensitive to exterior, cooler temperatures. The core temperatures of women are increased even more under the influence of external hormones, such as birth control pills.
Men have a higher metabolic rate, the rate at which food is broken down for energy. This higher metabolic rate causes men to have a slightly higher overall body temperature, which means feeling cold a bit less.
Women are better at conserving a core temperature by shifting the blood from external areas, like the skin, to the interior of the body to protect organs like the heart and brain. When the shift to conserve core temperature is on, the extremities, like feet and hands, feel cold.
That is the measure of unique human features. In fact, your ear shape is as unique as your fingerprints. Your ear shape is fully developed at birth. Studies have shown that ear shape recognition is more than 99 percent accurate. Scientists are developing systems to use this information to complement DNA analysis and fingerprint identification.
Sweating is good
We have two different types of sweat glands. The most common sweat gland is called the eccrine gland. Eccrine glands are located all over our bodies and are responsible for sweating on the head, palms, and almost elsewhere else.
One square inch of our palms contains over 600 sweat glands. The product of the eccrine glands is essentially salt water. Eccrine sweat is odorless. Eccrine glands turn on under the influence of heat, hormones, emotions and exercise.
The most critical function of eccrine glands is to dissipate heat and cool our bodies down. Our bodies can only function at a very narrow temperature range, so temperature control is critical for life.
Scientists say the development of our ability to become extremely active while at the same time being able to sweat and cool our bodies down was probably one of the very biggest influences in our evolution to become the humans we are today. It makes us very different from all other animals. In fact, on a very hot day and with extreme exercise, the human body can produce over three gallons (= 48 glasses) of sweat!
The second type of sweat gland is the apocrine gland. These glands are located under the arm and around the genitals and anus. They produce an oily sweat that is acted upon by bacteria.
The action of bacteria digesting the fatty substances in apocrine sweat causes this type of sweat to have an odor. This is why many people wear deodorants, especially under their arms.
Scientists have come to realize that some of the strong smell of apocrine sweat is produced by chemicals in the sweat called pheromones. Pheromones may be very instrumental in how we perceive and are attracted to other humans. In a strange sense, sweat glands, namely the apocrine sweat glands, play a significant role in human reproduction!
Human sweat is deposited on the skin through structures called pores. The human body contains approximately 10 million pores.
Our noses are extremely powerful
In fact, our noses are the most sensitive organ we have. They allow us to “taste” food, which is actually smelling food. Think about it: When you have a cold, you can’t taste food.
Studies have shown that women have a slightly better sense of smell than men. Scientists estimate that the human nose can differentiate an astounding 500 billion different smells!
The human brain cannot sense pain
When you stub your toe, you know what pain is. That is because your foot contains pain receptors that send the signal to your brain, and your brain tells you that you are experiencing pain.
Oddly, the brain itself contains no pain receptors! In fact, when one has a headache, the pain signal is actually from the membrane that covers the brain. This interesting fact has been utilized by brain surgeons, as they can have full conversations with patients undergoing open brain surgery to make sure they are not doing anything to affect the speech centers in the brain!
The brain is amazing because it receives over 10 million input signals per minute, but it sorts things out and keeps us going.
Next week: our amazing hair, stomachs, spines, dimples and skin
Charles E. Crutchfield III, MD is a board certified dermatologist and Clinical Professor of Dermatology at the University of Minnesota Medical School. He also has a private practice in Eagan, MN. He received his M.D. and Master’s Degree in Molecular Biology and Genomics from the Mayo Clinic. He has been selected as one of the top 10 dermatologists in the United States by Black Enterprise magazine. Dr. Crutchfield was recognized by Minnesota Medicine as one of the 100 Most Influential Healthcare Leaders in Minnesota. He is the team dermatologist for the Minnesota Twins, Vikings, Timberwolves, Wild and Lynx. Dr. Crutchfield is an active member of both the American and National Medical Associations.
Charles E. Crutchfield III, MD is a board-certified dermatologist and clinical professor of dermatology at the University of Minnesota Medical School and a Benedict Distinguished Visiting Professor of biology at Carleton College. He also has a private practice, Crutchfield Dermatology in Eagan, MN.
He received his MD and Master’s Degree in molecular biology and
genomics from the Mayo Clinic. He has been selected as one of the top 10 dermatologists in the United States by Black Enterprise magazine. Minnesota Medicine recognized Dr. Crutchfield as one of the 100 Most Influential Healthcare Leaders in Minnesota. Dr. Crutchfield specializes in
skin-of-color and has been selected by physicians and nurses as one of the leading dermatologists in Minnesota for the past 18 years.
He is the team dermatologist for the Minnesota Twins, Vikings, Timberwolves, Wild and Lynx. Dr. Crutchfield is an active member of both the American and National Medical Associations and president of the Minnesota Association of Black Physicians. He can be reached at CrutchfieldDermatology.com or by calling 651-209-3600.