Brianna Laplante

I am really interested in circulation changes that take place from fetuses to newborns.  Increased uptake of oxygen by lungs/first and subsequent breaths induces avasoconstriction of the ductus venosus and the ductus arteriosis.  Aeration of the lungs at birth is assocatied with..1) a dramatic fall in pulmonary vascular resistance due to lung expansion, 2) a marked increase of pulmonary blood flow, which raises the left atrial pressure above that of the IVC and 3) a progressive thinning of the walls of the pulmonary arteries due to stretching as the lungs expand with the first few breaths.

As the baby takes their first breath the pulmonary alveoli open up leading to 1) decreasing pressure in the pulmonary tissues, 2) blood pressure from the right side of the heart rushes to fill the alveolar capillaries, 3) pressure in the right side of the heart decreases, 4) pressure in the left side of the heart increases as more blood is returned from the well-vascularized pulmonary tissue via the pulmonary veins to the left atrium.  Blood pressure is now high in the aorta and systemic circulation is now well established.  

Control of circulation is a reflex function regulated: 1) peripherally by the baroreceptors in the aortic arch and carotid sinus, 2) centrally by baroreceptors in cardiovascular center of medulla and 3) respiratory and circulatory reflexes are usually strong in heatlhy newborns, but their efficiency of controlling cardiovascular function is susceptible to environmental factors. 

The foramen ovale closes at birth due to decreased flow from placenta to IVC to hold foramen open and because of increased pulmonary blood flow and and pulmonary venous return to left side of the heart causing the pressure in the left atrium to be higher than the right atrium.  The right ventricular wall is thicker than the left ventricular wall because the right ventricle has been working harder.  The right ventricular wall becomes thinner as the work load is evened out.  The umbilical arteries also constrict at birth to prevent loss of infantis blood.  The umbilical cord is not tied for 30-60 seconds so that blood flow through the umbilical vein continues, transferring fetal blood from the placenta to the infant.  Pretty amazing how this all happens!! Have a good spring break everyone!!

In an average lifetime the heart beats more than 2.5 billion times, without ever pausing to rest.  The heart is like a pumping machine, the heart provides the power needed for life.  Here are the essential tips for maintaining a healthy heart and lifestyle… 

Healthy Diet: 

A healthy diet is the best defense against high cholesterol, high blood pressure, and excess body weight.  These are the 3 main contributors to heart disease!!  The American Heart Association says lists the following guide for improving heart-healthy diets:  Eat a variety of fruits and veggies.  (5+ servings per day).  Eat a variety of grain products, especially whole grain and bran, which is particularly good for the heart.  (6+ servings per day).  Include organic milk products, beans, seeds and nuts.  Choose healthy fats like Omega 3 fatty acids from flax, nuts and avacado.  Limit your intake of foods high in calories and low in nutrition.  This includes foods and drinks with lots of added sugar like soft drinks and candy.  Choose food low in saturated fat, trans fat, and cholesterol **Reminder:** animal products such as red meat, chicken, pork and eggs are high in these fats.  Limit your sodium intake to less than 2,300 mg per day.  Limit alcohol intake and try to always maintain your ideal weight!

Exercise:

Remember, the heart is a muscle, and the only way to keep muscles healthy is to exercise!  The trick is to find some form of exercise you enjoy doing, and do it at least 5 times a week to please our hearts and the rest of our bodies, all at the same time!  Exercising can also help us maintain healthy weight levels, which is important to many other factors pertaining to the heart. 

Smoking, Drugs and Alcohol:

The heart’s job is to pump nutrient-rich blood throughout the body.  If you smoke, take drugs or drink excessively, you are giving the heart a lot of extra work.  The heart cannot handle too much extra work over a long period of time.  Over time, the healthy heart will suffer.  Scientists have proven that smoking doubles your risk of having a heart attack, and doubles, triples even quadruples your risk of having sudden cardiac death.  Because drugs are foreign substances, they can really damage your heart.  While drinking in moderation may not pose heart damage, drink heavily is extremely harmful to the heart.  While alcohol flows in the blood stream, the nutrient-rich blood is less able to nourish the heart. 

 The heart is the essential organ in the body, and it is our job to keep it going strong!!! Enjoy

I thought last night’s lecture on blood was really interesting.  Blood is a connective tissue in our bodies that is vital to human survival.  I decided to look up more information on a fairly common blood disorder known as anemia.  Anemia is a condition in which a person’s blood has a below normal amount of erythrocytes/red blood cells, or the red blood cells don’t have enough hemoglobin.  Hemoglobin is an iron-rich protein which carries oxygen from the lungs to the rest of the body.  In people with anemia, their blood does not carry enough oxygen to the rest of the body.  As a result, people with anemia feel tired, along with other symptoms because their bodies are not receiving enough oxygen. 

In severe or prolonged cases of anemia, the lack of oxygen in the blood can cause serious, sometimes fatal damage to the heart and other organs of the body.  In some kinds of anemia, there are low amounts of the the 3 types of blood cells–thrombocytes, erythrocytes and leukocytes.  Certain types of anemia may be severe, long-lasting and life threatening if not diagnosed and treated.  On the flip side, some types of anemia can be mild, short-lived and easily treated. 

After learning the basics about anemia….my main questions was who is at risk??

I soon learned that women and people with chronic diseases are at greater risk for anemia.  Women during their childbearing age are at greatest risk because they lose blood from menstruation and childbirth.  Older adults and infants younger than 2 are also at risk for anemia.  Unfortunately, anemia can also be inherited!  Methods such as consulting your doctor and changing your diet and adding supplements can also help prevent some types of anemia.  More than 3 million people have anemia in the U.S!!  Keep this in mind everyone, especially the ladies in the class!

The thyroid gland is a small gland, usually weighing less than one ounce, located just below the larynx.  It is made up of two lobes that lie along the trachea which are joined together by a narrow band of thyroid tissue, called the isthmus.  During development inside the womb, the thyroid gland originates in the back of the tongue, but it normally moves to the front of the neck before birth.  In rare cases, it fails to move properly and is located high in the neck or even in the back of the tongue.  This abnormal condition is called lingual thyroid.  At other times, it may migrate too far and end up in the chest. 

The function of the thyroid gland is to take iodine, which is found in many foods, and convert it into thyroid hormones: thyroxine (T4) and triiodothyronine (T3).  Thyroid cells are the only cells in the body that can absorb iodine.  These cells combine iodine and the amino acid tyrosine to make T3 and T4.  T3 and T4 are then released into the blood stream and transported throughout the body where they control metabolism.  Every cell in the body depends upon thyroid hormones for regulation of their metabolism.  The normal thyroid gland produces about 80% T4 and about 20% T3, however T3 is about four times the hormone strength of T4.

 The thyroid gland is under the control of the pituitary gland, a small gland the size of a peanut at the base of the brain.  When levels of T3 and T4 drop too low, the pituitary gland produces thyroid stimulating hormone (TSH) which stimulates the thyroid gland to produce more hormones.  Under the influence of TSH, the tyroid will manufacture and secrete T3 and T4, raising their blood levels.  The pituitary gland senses these changes and responds by decreasing its TSH production. 

Thyroid cancer is not very common.  Thyroid cancer only accounts for 1.2% of all new cancers in the U.S. annually! The four types of thyroid cancer include papillary, follicular, medullary, and anaplastic.  September is thyroid cancer awareness month.

Since lecture was cancelled this week, I decided to post about lab.  Our sense of hearing is the ability to detect mechanical vibrations we call sound.  Deafness can be inherited or acquired. 

 Acquired Deafness:

If a labratory animal is exposed to very intense, pure tones, the animal eventually becomes deaf to those frequencies, but it’s ability to detect other frequencies are unimpaired.  Examination of its organ Corti reveals destroyed hair cells in a single area whose location can be easily correlated with the pitch of destructive sound.  Similar defecits occur in humans who are exposed to intense noises for long periods. 

Inherited Deafness:

About 1 in 1000 newborns are born deaf because of a genetic defect.  As the years go by, about 16% of humans suffer a progressive loss of hearing due to genetic defects.  Mutations in a transcription factor have been associated with a stapes that cannot move freely and thus cannot transmit vibrations to the oval window.  The proper organization of the stereocilia involves actin, a form of myosin and cadherins.  Mutations in the gene encoding a protein that helps with actin polymerization also cause deafness.  The potassium that enters the hair cells must be removed from them and recycled back to the endolymph for hearing to continue.  Failure for the process to happen is linked to deafness.

*Interesting Facts*

-deaf people have safer driving records than hearing people nationally!

-when Beethoven produced his 9th symphony, he was profoundly deaf

-about 22 million people in the U.S. are hearing impaired

-the man who invented shorthand, John Gregg, was deaf