Anatomy WK 15 (5/8) | Comprehensive Notes on Red Blood Cells and Lymphatic System

Anemia

Anemia is a condition characterized by a lower-than-normal number of red blood cells.
It can also refer to a situation where the number of red blood cells is normal, but the amount of hemoglobin in each red blood cell is insufficient.
Anemia is problematic because it impairs the delivery of oxygen to the body's tissues.
The body regulates red blood cell production through erythropoietin (EPO), a hormone released by the kidneys.
EPO increases both the number of red blood cells produced and the amount of hemoglobin in each cell.
People with kidney issues or certain genetic conditions may not produce enough EPO, leading to chronic anemia.
Synthetic EPO can be administered to stimulate red blood cell production in these cases.
EPO is sometimes abused by athletes as a form of blood doping to enhance performance.

Blood Doping

Blood doping involves increasing the number of red blood cells in the body to enhance athletic performance.
Endurance athletes, such as marathoners, distance swimmers, and bikers, may use blood doping techniques.
Blood doping is illegal in sports.
Erythropoietin (EPO) is a commonly used substance in blood doping.
EPO boosts the body's production of red blood cells, increasing oxygen delivery to muscles.
More oxygen allows muscles to work harder and longer, improving performance.
Blood doping has been banned in sports since the early 1990s, but detection remains challenging.
Overusing EPO can thicken the blood, increasing the risk of blood clots.
Blood doping provides an unfair advantage by allowing athletes to exercise for longer periods without fatigue.
Athletes may blood dope months before an event, making detection difficult due to the lifespan of red blood cells ( $120-150$ days).
Athletes may also donate their own blood and re-infuse it closer to an event to increase blood volume and red blood cell count.
Constant monitoring of athletes is necessary to detect blood doping attempts, but it's not foolproof.

Natural Ways to increase Erythropoietin

Exposure to low-oxygen environments, such as high altitudes, can naturally increase erythropoietin levels.
Altitude training involves training in areas with lower oxygen availability to stimulate red blood cell production.
At higher elevations, the air density is lower, resulting in less available oxygen per breath.
The percentage of oxygen in the air remains the same at high altitudes, but there is less air overall.
The body compensates for the lack of available oxygen by producing more and larger red blood cells.
It takes time for the body to acclimatize to high altitudes and for erythropoietin production to increase.
Athletes may follow the "Live High Train Low" principle, living at high altitudes to stimulate red blood cell production but training at lower altitudes to avoid overexertion.
The amount of erythropoietin and red blood cells in an individual typically falls within a certain range.
Athletes may attempt to blood dope within a legal range by keeping their erythropoietin levels within the expected range.
Doping agencies face the challenge of proving that athletes are cheating, as individuals may claim their naturally high levels are unique.

White Blood Cells

White blood cells are less numerous than red blood cells in the blood.
White blood cells are essential for defending the body against infections, parasites, and diseases.
They also play a role in mediating healing and recovery after tissue damage.
White blood cells originate from hematopoietic stem cells in the bone marrow, like all other blood cells.
There are various types of white blood cells, including those that reside outside the bloodstream, such as microglia in the brain and resident macrophages in the lungs.

Types of White Blood Cells

Five primary types of white blood cells found in the blood:
- Neutrophils
- Eosinophils
- Basophils
- Monocytes
- Lymphocytes
Granulocytes include neutrophils, eosinophils, and basophils.
Agranulocytes include monocytes and lymphocytes.
The mnemonic "Never Let Monkeys Eat Bananas" represents the order of abundance of white blood cells: Neutrophils (most common), Lymphocytes, Monocytes, Eosinophils, Basophils (least common).
Macrophages are specialized white blood cells that engulf and remove dead or damaged cells, bacteria, viruses, and fungi.
Macrophages play a crucial role in mediating the recovery response to injury by regulating inflammation and directing the healing process.

Extravasation

Extravasation is the process by which white blood cells move from inside a blood vessel to outside a blood vessel.
This process is essential for white blood cells to reach sites of infection or tissue damage outside the bloodstream.
Diapedesis is a shape change that white blood cells undergo to squeeze through the intercellular clefts in capillary walls.
Capillaries become leakier during inflammation, allowing white blood cells to exit while preventing red blood cells from leaking out.
Histamine is a chemical that triggers the opening of capillary walls, facilitating inflammation.
Antihistamines block the release or binding of histamine, reducing capillary opening and inflammatory swelling.
Extravasation can occur even without histamine but to a lesser extent.

Platelets

Platelets are formed from hematopoietic stem cells in the bone marrow.
Platelets, along with red and white blood cells, cannot reproduce on their own and must be produced in the bone marrow.
Platelets are essential for clot formation. Platelets help the body stop bleeding by forming clots.
Platelets exist in either an activated or inactivated state.
In healthy blood vessels, platelets are typically in an inactive state, reducing the likelihood of clot formation.
Damage to the endothelium of blood vessels triggers platelet activation.
Activated platelets stick to the vessel walls and recruit other platelets and red blood cells to form a clot.
Inflammation can also trigger platelet activation.
COVID-19 can cause inflammation of blood vessels, leading to the formation of small blood clots.
Activated platelets become spiky and adhere to vessel walls, other platelets, and red blood cells to form a clot.
The platelet-based clot is a temporary solution, and the clot is reinforced with scar tissue and fibrin over time.

Lymph

Plasma, lymph, lymphatic fluid, and interstitial fluid are essentially the same, differing only in location.
Plasma is the water component of blood inside blood vessels.
When plasma leaks out of blood vessels, it becomes interstitial fluid.
Interstitial fluid is fluid between cells.
Interstitial fluid recycled back into the lymphatic system becomes lymph or lymphatic fluid.
The lymphatic system is the system that is responsible for the recycling process.
Lymphatic vessels, similar to capillaries, are found alongside blood vessels and capillaries.
Lymphatic capillaries have intercellular clefts, or valves, that open in response to fluid pressure differences.
Higher pressure in the interstitial fluid opens these valves, allowing more fluid to be absorbed by lymphatic capillaries.
Lymphatic vessels resemble veins, with relatively thin walls.
Lymphatic vessels transport fluid and return it to the blood thru lymphatic ducts.
The lymphatic system eventually drains lymph back into the veins, where it becomes plasma again.
The thoracic duct drains lymphatic fluid from the left side of the face, left upper body, both legs, and both sides of the lower abdomen.
The right lymphatic duct drains lymphatic fluid from the right side of the head and neck, right thorax, right abdomen, and right arm.
Both lymphatic vessels dump lymph back into the veins through the subclavian veins.

Lymph Nodes

Lymph nodes are located along lymphatic vessels and filter the lymph before it returns to the blood.
Lymph nodes contain white blood cells that kill viruses and bacteria in the lymph.
Swollen lymph nodes indicate that the body is fighting an infection.
During an infection, more white blood cells are sent to the lymph nodes and the flow of lymph is slowed to filter bad stuff.
Swollen lymph nodes in the neck indicate an infection in the head region.
Sepsis occurs when an infection persists in the bloodstream because the lymph system doesn't do a good job, allowing viruses and bacteria into your white blood that your white blood cells can't keep under control.

Lymph Nodes and Tumors

The lymphatic system and bloodstream are primary pathways for tumor metastasis.
Tumor cells can break off from the primary tumor and enter lymphatic capillaries.
The lymph nodes act as the last line of defense to prevent cancer from reaching other organs in the body.
Cancer that has made it to the lymph nodes is part of the staging process for tumors.
Axillary lymph nodes are frequently sampled and biopsied in breast cancer patients.
Tumors can often get stuck in lymph nodes and indicate a potentially more aggressive cancer.

Swelling or Edema

Swelling or edema is a fluid collection within the interstitial spaces between cells.
Lymphedema is a type of edema caused by an insufficient lymphatic system.
An insufficient lymphatic system to the body is unable to remove normal amounts of capillary leakage.
Secondary lymphedema is caused by some type of trauma, infection, injury, or surgery to your lymphatic system.
An example of why you need your lympathic system is that having a large number of lymph nodes removed as part of cancer treatment can result in secondary lymphedema.
Primary lymphedema is caused by a genetic condition that made your lymphatic system not develop normally.

Lymphoid Organs

Lymphoid organs are organs are associated with your immune system, such as the tonsils, thymus, spleen, and appendix.
Primary lymphoid organs are bone marrow and the thymus.
Primary organs are important as the sites where white blood cells are made or matured.
Secondary lymphoid organs, such as lymph nodes, appendix, and spleen, do not make white blood cells but hold them.
The spleen is considered a weird and mysterious organ that is strongly affected by certain diseases or infections.
For example, mononucleosis really targets the spleen because the cells that the virus attacks and uses to make copies of itself are your b lymphocytes and guess what? There's a bunch of b lymphocytes hanging out inside your spleen.
Also red blood cells go to die in the spleen.
Mononucleosis (mono), caused by Epstein Barr virus, strongly affects the spleen by targeting B lymphocytes.
Inflammation in the spleen caused by mono can lead to splenomegaly.
A ruptured spleen is an emergency because it bleeds a lot.
A splenectomy, or removal of the spleen, is necessary in cases of rupture.
After a splenectomy, other secondary lymphoid organs can take over the functions of the spleen.