Blood, Immune, and Lymphatic System Review
Overview: Blood, Immune & Lymphatic Systems (Lab Focus)
- Lab covers two intertwined topics:
- Blood (structure, function, clinical tests)
- Lymphatic / immune anatomy (fluid recovery + defense)
- Immune “cells doing the action” ≠ Lymphatic “plumbing that drains excess interstitial fluid (≈15 % capillary filtrate not re-absorbed).”
- Digestive tie-in: lacteals move dietary fats too large for blood capillaries.
Core Functions of Blood
- Transport
- Gases: O₂ delivery, CO₂ removal
- Nutrients (glucose, lipids, amino acids)
- Waste (e.g.
- Urea from protein catabolism
- Nucleic-acid breakdown products)
- Hormones (endocrine communication highway)
- Protection
- Leukocytes + antibodies fight infection
- Hemostasis (clotting)
- Regulation
- Water balance / blood volume
- Acid-base buffering via [\text{H}^+] modulation
Blood Volume & Basic Composition
- Typical adult volume: 4–6 L
- Two broad fractions after centrifugation:
- Plasma (~55 %) – clear, protein-rich fluid
- Formed elements (~45 %)
- Erythrocytes (RBCs)
- Leukocytes (WBCs)
- Platelets (thrombocytes)
- Centrifuge demo:
- Capillary tube → spin → layers
- Plasma (top)
- Buffy coat (thin) = WBCs + platelets
- Packed RBCs (bottom)
- % RBC column = Hematocrit
- Men ≈ 42–52 %
- Women ≈ 37–48 % (menstrual loss → lower baseline ⇒ dietary iron critical)
Erythrocytes (RBCs)
- Shape: biconcave discs ("donuts with film")
- ↑ surface area for rapid gas exchange
- Anucleate; rely on bone-marrow production
- Production terminology
- General: Hematopoiesis
- RBC specific: Erythropoiesis (stimulated by kidney hormone EPO)
- Tissue source: Myeloid marrow
- Hemoglobin (Hb) structure
- Tetramer = 2 α + 2 β globin chains
- Each chain holds a heme with Fe²⁺ center ("iron bracket")
- Requires dietary iron → deficiency ⇒ ↓ Hb ⇒ iron-deficiency anemia
- Color logic
- Oxy-Hb (Fe³⁺) = bright red
- Deoxy-Hb = darker, rusty
- Talquist paper color scale estimates [Hb] clinically
Leukocytes (WBCs)
- Production: Leukopoiesis in lymphoid tissue (marrow → maturation elsewhere)
- Two overarching groups
- Granulocytes (cytoplasmic granules visible)
- Neutrophils (≈60 %) – phagocytose bacteria; ↑ in bacterial infections (CBC clue for antibiotics)
- Eosinophils – attack parasites, modulate allergies
- Basophils – release histamine (vasodilator) & heparin; ↑ in allergy, diabetes, chickenpox
- Agranulocytes
- Lymphocytes (≈30 %; most common agranulocyte) – B cells (antibody makers) & T cells (cell-mediated immunity, thymus matured); destroy viruses, cancer, foreign cells
- Monocytes – circulate; exit blood → transform to macrophages (tissue phagocytes) during inflammation/viral infection
Platelets (Thrombocytes)
- Cell fragments from megakaryocyte cytoplasm (no nucleus)
- Smallest formed element
- Role in hemostasis
- Become amoeboid “puzzle pieces”
- Aggregate → platelet plug
- Reinforced by fibrin strands → stable clot
Blood Typing & Transfusion Compatibility
ABO Antigens ("flags on flagpoles")
- Surface glycoproteins = antigens A & B
- A blood: only A flag
- B blood: only B flag
- AB: both (co-dominant genetics)
- O: none (flagpole empty)
- Antibodies (Ab) float in plasma like Velcro/magnets
- Anti-A binds A flag; Anti-B binds B flag
- Rule: You naturally LACK Ab against your own antigen
- Agglutination test (lab)
- Mix drop of blood with Anti-A, Anti-B (and Anti-D)
- Observe clumping (polka-dot/gritty) vs smooth pool
- Patterns:
- Clump only with Anti-A → Type A
- Clump only with Anti-B → Type B
- Clump with both → AB
- Clump with neither → O
- Genetics & prevalence
- O the most common (hidden recessive in A/B carriers)
- AB the rarest
Rh (D) Factor
- Separate antigen (discovered in Rhesus monkeys)
- Rh⁺ (≈90 %) – D antigen present
- Rh⁻ – no D antigen; typically no anti-D Ab unless sensitized
- Hemolytic Disease of the Newborn (HDN)
- Rh⁻ mother + Rh⁺ fetus
- First birth: placental mixing at delivery → mom forms Anti-D Ab
- Subsequent Rh⁺ pregnancy: maternal Ab cross placenta → fetal anemia (erythroblastosis fetalis)
- Prevention: RhoGAM injections postpartum (and later pregnancies) neutralize fetal Rh antigen before immune response
Transfusion rules summary
- Universal donor = O⁻ (no A, B, or D flags)
- Universal recipient = AB⁺ (already has A, B, D; makes no corresponding antibodies)
Selected Blood Pathologies
- Polycythemia (↑ RBC count)
- Primary: marrow cancer
- Secondary: dehydration, emphysema, high altitude
- Dangers: ↑ viscosity → embolism, stroke, heart failure
- Anemia (↓ RBC or Hb)
- Causes: nutrition (Fe, B₁₂), kidney failure (↓ EPO), hemorrhage
- Symptoms: hypoxia, fatigue, pallor, tachycardia (thin blood)
- Sickle Cell Disease
- African/Caribbean genetic trait (Hb mutation)
- Deoxygenated Hb polymerizes → RBC "crescent" shape
- Capillary blockage, pain, organ damage
- Heterozygote advantage vs malaria Plasmodium
- WBC disorders
- Leukopenia (< 5 000 µL) – infection risk (e.g., chemo, AIDS)
- Leukocytosis (> 10 000 µL) – infection, allergy, stress
- Leukemia – cancer of WBC line; massive counts (~100 000 µL) but nonfunctional → infection & anemia common
Lymphatic System – Structure & Flow
- Three major roles: fluid return, lipid absorption, immune surveillance ("secondary circulatory system")
- Lymph = recovered interstitial fluid
- Vessels: begin as blind lymphatic capillaries → converge through lymph nodes → large trunks → ducts → venous angle
- Key vessels/landmarks
- Cisterna chyli – dilated sac in abdomen receiving lumbar & intestinal trunks
- Thoracic duct (left) – drains cisterna chyli + left head/neck + left arm → left subclavian vein
- Right lymphatic duct – drains right head/neck + right arm → right subclavian vein
- Clinical correlate: nodes swell (palpable) during local infection; MD palpates cervical/submandibular chains for ENT illnesses
Lymphoid Organs & Tissues
- Bone marrow – B cell maturation; hematopoiesis
- Thymus – anterior mediastinum; huge in infants → involutes; T cell education ("self-tolerance")
- Spleen – LUQ; filters aged/damaged RBCs, platelet reservoir
- Tonsils (5 total)
- 1 Pharyngeal (adenoid)
- 2 Palatine
- 2 Lingual
- Peyer’s patches – ileum; guard intestinal lumen
- Lymph nodes – clusters along vessels; reticular mesh + macrophages
Laboratory / Practical Procedures & Safety
- Capillary tube & centrifuge
- Seal with clay, spin → measure hematocrit using ruler card
- Buffy coat often microscopic
- Finger-stick blood typing kit (Carolina card)
- Prep card wells labeled Anti-A, Anti-B, Anti-D
- Add drop of distilled water, then fresh blood from spring-loaded lancet
- Stir with separate applicators to prevent cross-contamination
- Observe for agglutination patterns (solid vs speckled)
- Submit liability waiver; watch demo video (Dr Kaiser)
- If unable to self-stick, must still interpret photos/diagrams on quiz (identify where clumping occurred)
- Visible Body modules supplement content; may mention liver/kidney roles (context from future lectures: hepatic portal nutrient processing; renal blood-pressure regulation)
- Safety/ethics:
- Use alcohol swab & bandage; dispose lancet properly
- Do not perform test while fasting/queasy
Inter-Lecture Connections
- Circulation lecture: 15 % capillary filtrate reclaimed by lymphatics
- Endocrine lecture: kidneys secrete EPO → erythropoiesis
- Reproduction lecture: placental blood mixing & Rh incompatibility
- Immunology lecture: B vs T lymphocytes, antibody mechanism
- Respiratory lecture: high altitude hypoxia → secondary polycythemia
Equations / Numbers to Remember
- Plasma pH buffering concept: \text{pH} = -\log_{10}[\text{H}^+]
- Hematocrit normal ranges: \text{Male} \approx 0.45-0.52, \text{Female} \approx 0.37-0.48
- WBC counts
- Normal: 5\times10^3\; \text{to}\; 10\times10^3\; \text{cells/µL}
- Leukocytosis: >10\times10^3\; \text{cells/µL}
- Leukemia: \sim100\times10^3\; \text{cells/µL (nonfunctional)}
Practical & Ethical Implications
- Correct matching of antigens/antibodies critical to avoid transfusion reactions (agglutination → renal failure/death)
- O⁻ supplies in blood banks prioritized (universal donor)
- RhoGAM prophylaxis saves Rh⁺ second pregnancies from HDN
- Antihistamines (e.g., Benadryl) counter basophil histamine in allergic reactions
- Awareness of iron intake especially in menstruating females to prevent anemia