Monthly Archives: November 2011

Lecture 32 – More Information on RBC’s

Red Blood Corpuscles – Erythrocytes (Commonly referred to as red blood cells or RBC’s)

The most numerous type in the blood –

Average 7 micrometer in diameter

Women average about 4.8 million of these cells per cubic millimeter (mm cubed, which is the same as a microliter of blood.

Men average about 5.4 x 10 to the 6th per microliter

These values can vary over quite a range depending on such factors as altitude and health.
(Peruvians, for example, living at 18,000 feet may have as many as 8.3 x 10 to the 6th RBC’s per microliter.

RBC precursors mature in the bone marrow and are closely attached to a macrophage.

They manufacture hemoglobin until it accounts for some 90% of the dry weight of the cell.

In mammals, the nucleus is squeezed out of the cell and is ingested by the macrophage.

All of the mitochondria, endoplasmic reticulum and Golgi apparatus are destroyed.

No longer needed proteins are expelled from the cell in vesicles called exosomes.

RBC’s have a characteristic biconcave shape. The interior will show up on electron microscope as darkened in the center to show this characteristic. They sort of resemble a donut.

RBC’s are terminally differentiated meaning they can never divide. They live about 120 days and are ingested by phagocytic cells in the liver and spleen. Most of the iron in their hemoglobin is reclaimed and recycled. The other heme portion of the molecule is degraded into bile pigments and excreted by the liver. Some 3 million RBC’s die and are scavenged by the liver every second.

Oxygen Transport

RBC’s are responsible for the transport of oxygen and carbon dioxide.

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Filed under Anatomy Notes, Survey of Blood

Lecture 31 – Blood Formation

The various types of blood cells are produced in the bone marrow. (10 to the 11th power of them each day in an adult human). Blood cells arise from a single type of cell called a hemopoietic stem cell – an adult multi-potent stem cell.
Stem cells:
are very rare; about one in every 10,000 bone marrow cells,
are likely attached by adherens junctions to osteoblasts lining the inner surface of bone cavities,
express a cell-surface protein designated CD34,
produce by mitosis, two kinds of progeny – more stem cells and cells that begin to differentiate along the paths leading to the various kinds of blood cells. (For instance, a mouse that has had all of his stem cells killed by radiation can besaved by a single dose of a stem cell.)

Which path is taken is regulating the need for more of that type of blood cell which is, in turn, controlled by appropriate cytokines and/or hormones.
Interleukin-7 is the major cytokine in stimulating bone marrow stem cells. These stem cells start down the ‘lymphoid’ path leading to the various lymphocytes (mostly B cells and T cells).
Some of the cytokines that drive the differentiation of the “myeloid” leukocytes are:
Erythropoietin (EPO), produced by the kidneys, enhances the production of red blood corpuscles (RBC’s).
Thrombopoietin (TPO), assisted by Interleukin -11 (IL-11), stimulates production of megakaryocytes. Their fragmentation produces platelets.
Granulocyte-macrophage colony-stimulating factor (GM-CSF), as its name suggests, sends cells down the path leading to both those cell types. One path or the other is taken.
Under the influence of the granulococyte colony-stimulating factor (G-CSF), they differentiate into neutrophils.
Further stimulated by interleukin-5 (IL-5) they develop into eosinophils.
Interleukin-3 (IL-3) participates in the differentiation of most of the white blood cells but plays a prominent role in the formation of basophils, which are responsible for some allergies.
Stimulated by macrophage colony-stimulating factor (M-CSF) the granulocyte/macrophage progenitor cells differentiate into monocytes, macrophages, and dendritic cells. (DC’s).

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Coping Skills

Are you overwhelmed with your current academic load?  Professional students are not alone.  Professors are equally as overwhelmed.  The academic life is an unusual one, in that days pass by like dominoes falling down in a row.  As we go through the motions of being in labs, lectures, and clinics, our families carry on without us.  Long hours of studying keep us from attending many family functions.  The holiday season is one of the hardest times of the year for academicians.  Remain positive at all cost.  You cannot afford to allow negative thoughts into your mind.

Remember to take a few slow moments every day.  Whether it is a bubble bath or a favorite cup of tea, do something special for yourself every day.  Pet your dog or look at a recent set of photos.  Remember to send a special message to your sweetheart, especially if they are not in the medical world.  They are in disbelief about your schedule also.  The to-do list will always be there.  Get counseling if needed.  An unbiased set of ears can be helpful.  Do well with this information and get ready to discover more about our vital life fluid, our blood.

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Filed under Tips for Success