Blood: Plasma, Serum, and Formed Elements – Detailed Notes (AP-style)

Plasma vs Serum

  • Plasma is the overall liquid portion of the blood; serum is the liquid portion after clotting factors are removed (i.e., the clotting factors with fibrinogen removed).
  • On the slide, the supervisor asked to capture both the upper-left written content and the lower-right content before moving on.
  • Quick refresher embedded in the lecture: atomic number = number of positive protons; atomic mass = protons + neutrons.

Plasma: Composition and role

  • Plasma accounts for about 55\% of blood; the remaining 45\% are formed elements.
  • The liquid portion (plasma) is predominantly water: about 91\% of plasma is water.
  • The most abundant plasma protein is albumin; its role includes maintaining oncotic pressure in the blood.
  • Plasma is not just a carrier for blood cells; it serves as a transportation system for many substances: gases, glucose, cholesterol, amino acids, electrolytes, vitamins, hormones, waste products, drugs, etc.
  • The blood skin product analogy: anything you put on your skin can enter the bloodstream and be processed by the liver, kidneys, etc.

Formed elements and their counts

  • Red blood cells (RBCs) = erythrocytes: 5{,}000{,}000\ \text{cells}/\mu L (per microliter).
  • White blood cells (WBCs): range about 4{-}10{,}000\ \text{cells}/\mu L (lab reference ranges may vary up to 11k by some labs).
  • Platelets: about 150{-}400{,}000\ \text{platelets}/\text{mm}^3 (cubic millimeter).
  • Rationale for units: platelets are very small, so counts are reported per mm³ instead of per µL.
  • Within plasma, there are not only cells but also the formed elements that float in the liquid: RBCs, WBCs, and platelets.

Red blood cells (RBCs) - Erythrocytes

  • RBCs are erythrocytes (erythro- = red).
  • Count: 5{,}000{,}000\ \,\text{cells}/\mu L.
  • Morphology: biconcave discs with no nucleus (anucleate).
  • Appearance analogy: hollowed-out jelly donut, squished in on both sides.
  • Key protein: hemoglobin (iron-containing protein) that carries oxygen and carbon dioxide to and from tissues.
  • Lifespan: approximately 120\ \text{days}.
  • Removal of damaged RBCs: filtered out by the liver and spleen; this is part of liver and spleen function in blood cell turnover.
  • An overview of RBC lifecycle includes formation (erythropoiesis) and destruction; excess and deficiency states exist.
  • Anatomy notes for organs involved: liver is in the right upper quadrant; spleen in the left upper quadrant.

RBC excess and deficiency terms

  • Erythrocytosis: condition of excess red blood cells (alternative term for high RBC count).
  • Polycythemia: another term meaning many red blood cells (often used interchangeably in common language).
  • Potential causes of excess RBCs include: reduced oxygen levels (e.g., high altitude), dehydration, cancer, smoking, sleep apnea, performance-enhancing steroids, and other factors that increase RBC production.
  • Anemia is a deficiency of RBCs; there are many causes:
    • Iron deficiency
    • Vitamin deficiencies (e.g., B12 deficiency, pernicious anemia)
    • Nutritional deficiencies
    • Blood loss
    • Bone marrow issues (impaired production)
    • Chemotherapy drugs
    • Sickle cell anemia
  • Erythropoiesis vs erythropoietin:
    • Erythropoiesis = the formation/generation of red blood cells (process).
    • Erythropoietin (protein) = hormone that drives erythropoiesis; product of kidneys; essential for RBC production. In the transcript, the protein is emphasized as erythropoietin (often abbreviated EPO).
  • The term erythropoiesis vs leukopoiesis vs thrombopoiesis:
    • Erythropoiesis = formation of RBCs.
    • Leukopoiesis = formation of white blood cells.
    • Thrombopoiesis = formation of platelets.
  • A note on terminology in the lecture:
    • Leukopoietin is not commonly listed as the main driver; colony-stimulating factors play a key role in signaling production of specific WBC types.
    • The protein required for RBC formation is erythropoietin; the term erythropoietin ends with -in (a common suffix for proteins).

White blood cells (WBCs) - Leukocytes

  • WBCs are referred to as leukocytes (leuko- = white).
  • Normal range: about 4{-}11{,}000\ \text{cells}/\mu L, though exact numbers may vary by lab reference ranges.
  • Five main types of white blood cells:
    • Granulocytes: neutrophils, basophils, eosinophils (Ben is grainy helps remember granulocytes).
    • Agranulocytes: monocytes and lymphocytes.
  • All white blood cells contain a nucleus.
  • The lecture emphasizes white blood cells can vary in numbers depending on infection or inflammation stage.

Granulocytes (contain granules in their cytoplasm)

  • Neutrophils:
    • Granulocytes; first responders to infection; often the most abundant WBC.
    • Phagocytes: engulf or swallow infectious cells (phagocytosis).
    • Role in inflammation and infection; often depicted as EMTs (early responders) in the lecture analogy.
  • Basophils:
    • Granulocytes; release histamine (inflammation mediator) and heparin (an anticoagulant).
    • Become mast cells when they enter tissues.
    • Basophils degranulate in response to danger signals, contributing to inflammatory responses.
  • Eosinophils:
    • Granulocytes; help neutralize histamine released by basophils.
    • Prominent in allergic reactions and parasitic infections (e.g., earthworms analogy used in class).

Agranulocytes (no visible granules)

  • Monocytes:
    • Precursors to macrophages and dendritic cells; participate in phagocytosis and antigen presentation (not elaborated in full in this lecture segment).
  • Lymphocytes:
    • Include T cells, B cells, and natural killer (NK) cells; roles in adaptive and innate immunity (not elaborated in full in this segment).

Key concepts: protein vs process, and blood cell production terminology

  • Distinguishing terms:
    • Erythropoiesis = formation/generation of red blood cells.
    • Leukopoiesis = formation/generation of white blood cells.
    • Thrombopoiesis = formation/generation of platelets.
    • Poiesis is the suffix meaning production or formation; erythro-, leuko-, thrombopoietin indicate processes.
  • The suffix -in is common for many proteins (e.g., erythropoietin); the protein required for RBC production is erythropoietin. The term erythropoietin ends with -in, indicating a protein.
  • The term leukopoietin is not standard; production of WBCs is driven by colony-stimulating factors (CSFs) and other signaling mechanisms.
  • Clotting vs coagulation:
    • Coagulation involves clotting factors and platelets forming a blood clot.
  • Agglutination vs coagulation:
    • Agglutination is the clumping of red blood cells (as seen in some immune reactions).

Hemopoiesis overview

  • Hemopoiesis is the general process of blood cell formation; there are three main lineages:
    • Erythropoiesis (RBCs)
    • Leukopoiesis (WBCs)
    • Thrombopoiesis (platelets)
  • Colony-stimulating factors (CSFs) regulate the production of specific white blood cell types by signaling precursor cells to differentiate and proliferate.

Quick reference and recap (facts to memorize)

  • Plasma accounts for 55\% of blood; plasma is about 91\% water; albumin is the most abundant plasma protein; albumin helps maintain oncotic pressure.
  • Formed elements constitute 45\% of blood.
  • RBCs: 5{,}000{,}000/\mu L; RBCs are anucleate, biconcave discs, contain hemoglobin, lifespan ≈120\ \text{days}; destroyed/damaged RBCs are removed by liver and spleen; liver and spleen locations: liver in the right upper quadrant, spleen in the left upper quadrant.
  • WBCs: 4{-}11{,}000/\mu L; five types: neutrophils, basophils, eosinophils (granulocytes), monocytes, lymphocytes (agranulocytes).
  • Platelets: 150{-}400{,}000/\text{mm}^3.
  • RBC excess: erythrocytosis; Polycythemia = many red blood cells; causes include low oxygen (high altitude), dehydration, cancer, smoking, sleep apnea, steroids.
  • RBC deficiency: anemia; causes include iron deficiency, B12 ( pernicious anemia ), other nutritional deficiencies, blood loss, bone marrow issues, chemotherapy, sickle cell anemia.
  • Erythropoiesis requires erythropoietin (protein) for RBC production.
  • Leukopoiesis requires signaling, including colony-stimulating factors; there is mention of leukopoietin in the lecture, but CSFs are the actual regulators discussed.
  • Thrombopoiesis requires thrombopoietin for platelet production.
  • Neutrophils: first responders, granulocytes, phagocytes, most abundant WBC.
  • Basophils: granulocytes; release histamine (inflammation mediator) and heparin (anticoagulant); become mast cells in tissues; degranulate in response to danger signals.
  • Eosinophils: granulocytes; neutralize histamine; elevated in allergies and parasitic infections.
  • Agranulocytes: monocytes and lymphocytes; do not have visible granules.
  • Leukocytosis = excess white blood cells; Leukopenia = deficiency of white blood cells; Neutropenia = deficiency of neutrophils.
  • Important review prompts from the lecturer:
    • Distinguish between plasma and serum; plasma includes clotting factors, serum does not.
    • Distinguish RBCs vs WBCs vs platelets; identify morphology and function.
    • Differentiate erythropoiesis, leukopoiesis, thrombopoiesis; relate to respective hormones and regulatory factors.
    • Recognize the roles of histamine and heparin in inflammation and coagulation (and note the lecture’s mention of histamine with neutrophils and basophils).

Quick recap questions (to test your recall)

  • What percentage of blood is plasma? 55\%
  • What is the most abundant plasma protein? Albumin.
  • What percent of plasma is water? 91\%
  • What is the most abundant type of formed element by count in blood? Red blood cells (RBCs).
  • What is the normal range for white blood cells? 4{-}11{,}000/\mu L
  • What is the platelet count range? 150{-}400{,}000/\text{mm}^3
  • What is the function of erythropoietin? Drives erythropoiesis (RBC production).
  • What is the function of thrombopoietin? Drives thrombopoiesis (platelet production).
  • Name the three granulocytes. Neutrophils, basophils, eosinophils.
  • Which WBC type is the first responder and highly phagocytic? Neutrophils.
  • Which cells release histamine and become mast cells in tissues? Basophils (and mast cells once in tissue).
  • What term describes the clumping of red blood cells? Agglutination.
  • What is coagulation? The process of blood clot formation involving clotting factors and platelets.
  • Which organs are involved in filtering damaged RBCs? Liver and spleen.
  • What is the meaning of leuko- in leukocytes? White.
  • What does poiesis mean? Production or formation.