Unit 1 - Blood

Dr. Swartz A&P 2 Lecture

List the functions of blood

Blood performs:

• Transport: Oxygen (O₂), carbon dioxide (CO₂), metabolic wastes (e.g., nitrogenous wastes), and hormones.

• Regulation: Maintains temperature (via blood flow), pH (via bicarbonate buffer), and fluid volume.

• Protection: Clotting to prevent blood loss and immune defenses (innate and adaptive immunity).

Describe the composition of blood, its physical characteristics, and justify its classification as a connective tissue

• Composition:

  • Plasma (liquid): ~55%

  • Formed elements (cells): erythrocytes (~99%), leukocytes (<1%), and platelets

• Physical separation via centrifugation:

  • Plasma (top layer)

  • Buffy coat (leukocytes and platelets)

  • Erythrocytes (bottom layer)

• Connective tissue justification:

  • Derived from embryonic mesoderm

  • Formed in red bone marrow

  • Plasma contains fibrinogen, which forms fibers during clotting

  • Leukocytes can migrate into connective tissues

• General Properties:

  • Thick

  • Doesn’t stick to things, allowing movement.

General composition of plasma

• Water (92%)

• Proteins (7%)

• Solutes (1%)

• Gases mostly reside in erythrocytes

Detailed Composition of Plasma

Water (92%)

Plasma proteins are involved in osmotic balance, protection, and transport of vitamins/minerals

Proteins (7%):

Albumin

• Composes the MOST plasma protein (60%)

• Made by LIVER

• Plays a key role in drawing water into blood vessels.

• It binds/transports hydrophobic molecules.

• It allows fats to be soluble in watery plasma and transports them to target tissues like muscle for energy.

Immunoglobulins:

• Composes the 2nd most plasma protein (18%)

• Product of immune system cells in LYMPHOID ORGANS

• Involved in humoral/adaptive immune response.

Fibrinogens

• Composes the LEAST plasma proteins (4%)

• Made by LIVER

• Involved in blood clotting

Carriers

• Hormone: IGF-binding proteins, thyroxine binding proteins, and transcortin

• Vitamins: retinol binding proteins, vitamin D binding proteins

• Lipids: apolipoprotein

• Redox metals: ceruloplasmin, transferrin

• Most are made in the LIVER

Solutes (1%)

Ions

• High in Na+, Cl-, and Ca+ relative to cytosol.

• Major buffer: Bicarbonate (HCO3-)

Solutes

• Glucose → Energy

• Amino Acids → Protein producers

• Waste products (urea)

• Hormones

• Lipids (binds to carrier proteins)

Gases are mostly contained within erythrocytes

• O2 and CO2

Describe the structure, function, and production of erythrocytes.

Structure

• No nucleus and mitochondria

  • Not a good source for DNA matching

• A biconcave shape disc filled with hemoglobin

  • Increase the surface area to volume ratio to maximize oxygen and carbon dioxide exchange.

  • Flexibility, allowing it to squeeze through tiny capillaries.

  • Flexible due to spectrin. Spectrin is a long, flexible, spring-like protein. A spectrin-based membrane skeleton is attached to the inner leaflet.

Function:

• Membrane differential glycosylation used to type blood (A, B, AB, O)

• Gas transport (O2 and CO2)

• Contains hemoglobin

• Uses carbonic anhydrase to transfer CO2

  • A fast and reversible reaction where:
    Carbon Dioxide + Water →←Carbonic Acid →←Bicarbonate + Hydrogen Ion

Production:

• Formed in red bone marrow (axial skeleton, girdles, and proximal epiphyses of femur and humerus) via hematopoiesis

• Stimulated by erythropoietin (EPO)

  • EPO is a hormone produced by the kidneys (“green light “ to signal the stem cells in the bone marrow to start making more RBC)

  • EPO release is stimulated by low oxygen (hypoxia) in kidney cells.

  • Stimulates the development of committed cells (proerythroblast)

Extra Shit:

• Lifetime is about 120 days.

  • Removed from your body by macrophages in the spleen, liver, and bone marrow.

  • Hemoglobin will be degraded into amino acids, free iron, and bilirubin.

In depth hematopoiesis

Occurs in red bone marrow of axial skeleton, girdles, and proximal epiphyses of humerus and femur.

Stem Cells divide and develop into mature erythrocytes

• Blast = bud during development

• Cyte = cell, upon completion of maturation

Developmental Stages:

• 1. Hematocytoblast (Stem Cell)

• 2. Proerythroblast (Committed Cell)

• Start of developmental pathway… Starting to lose mitotic ability

• 3. Basophilic Erythroblast (Phase 1: Ribosome Synthesis)

• 4. Polychromatic Erythroblast (Phase 2: Hemoglobin accumulation)

• 5. Orthochromatic Erythroblast

• 6. Rectiulocyte (Phase 3: Ejection of Nucleus)

• 7. Erythrocyte

• Note: The phases are within steps 3-6

During Development:

• After the proerythroblast (committed cell) is developed, development begins.
  

• 1. Hemoglobin production begins when the cell turns on genes that code for hemoglobin, the protein that carries oxygen. This means that the cell starts producing mRNA and translating it into hemoglobin proteins.
  Lots of mRNA → This would give the cell a basophilic appearance due to RNA’s acidic nature. (Basophilic Erythroblast)
  

• 2. As the cell produces more hemoglobin protein, the cytoplasm fills with it.
  More protein (which is basic) → This would make the cell acidophilic (pink) because proteins attract acidic dyes.
  

• 3. Once the cell has built enough hemoglobin, it will eject its nucleus to make space and improve oxygen-carrying efficiency.
  The cell becomes a reticulocyte → it is a nearly mature red blood cell with some leftover ribosomes or mRNA
  

• 4. The reticulocyte loses its remaining mRNA, completing its transformation into a mature erythrocyte (RBC).

Describe the chemical composition of hemoglobin

• Allowing higher affinity for O2, NO, and CO. (Able to attach to gases)

• IRON facilitates oxygen binding.

• Oxyhemoglobin (HbO2) = 4 O2 and its RED

• Deoxyhemoglobin (Hb) = No O2 and its BLUE/PURPLE

• Weak affinity for CO2 and HCO3- at the amino acid sites

• Chemically modified by glucose to form HbA1c

  • More glucose = more modification

  • HbA1c → Used to monitor blood glucose

Give examples of disorders caused by abnormalities of erythrocytes and the consequences of these disorders.

Anemia: lack of blood

• Hemorrhagic anemia: blood loss is greater than production
  

• Other anemia forms will be divided into…
  Low Erythrocyte Production
  High Erythrocyte Destruction
  

Low Erythrocyte Production

• Iron deficiency anemia: insufficient iron for heme synthesis

• Pernicious anemia: vitamin deficiency (B12 mostly)

• Renal anemia: lack of EPO production by the kidneys

• Aplastic anemia: destruction of stem and progenitor cells by drugs or virus

High Erythrocyte Destruction

• Hemolytic anemia: lysis of blood cells for acute reasons.

• Thalasemias: genetic disorder of hemoglobin synthesis → not enough alpha or beta subunit produced causes you NEED BOTH to make hemoglobin → functional hemoglobin deficit.

• Sickle Cell Anemia: a hemoglobin point mutation that results in cell rupture.