Blood Transit Study Guide
Physiology Reference Circulatory Dynamics
Cardiovascular System
Blood Transit Study Guide
Components, Cargo Types & Delivery Mechanisms
The Dual Transport System: Although blood contains four primary fractions, only two act as active cargo haulers: Red Blood Cells (Erythrocytes) for respiratory gas transport and Blood Plasma for dissolved solutes, chemical messengers, nutrients, wastes, and thermal energy. White blood cells (leukocytes) and platelets travel in circulation but function in immune defense and hemostatic repair, not transport.
1
Red Blood Cells (RBCs)
Erythrocytes • ~45% Blood Volume
Oxygen (\(O_2\)) Delivery (~98.5%)
Contains ~270M hemoglobin molecules. Four heme groups per molecule reversibly bind \(O_2\) at pulmonary capillaries forming oxyhemoglobin for systemic delivery.
Carbon Dioxide (\(CO_2\)) Return (~23%)
Binds directly to hemoglobin amino acid globin chains as carbaminohemoglobin to ferry waste gas from tissues back to the lungs.
Transport Specializations
Biconcave geometry optimizes diffusion distance. Lack of nucleus and mitochondria leaves maximum payload volume and prevents \(O_2\) consumption.
Mechanism: Hemoglobin Binding Gas Carrier
2
Blood Plasma
Liquid Matrix • ~55% Blood Volume
Cellular Fuel & Nutrients
Carries monosaccharides (glucose), amino acids, vitamins, and minerals in direct solution; shuttles lipids packaged within lipoprotein complexes.
Metabolic Wastes & Byproducts
Dissolves urea (from liver deamination), uric acid, creatinine, and lactic acid, delivering them to kidneys and skin for physiological excretion.
Hormones & Bicarbonate (\(HCO_3^-\))
Routes systemic chemical messengers. Transports ~70% of \(CO_2\) as dissolved bicarbonate ions, simultaneously stabilizing systemic pH (7.35–7.45).
Mechanism: Aqueous Solution & Buffers Solute & Heat
Master Blood Cargo Manifest Origin, Primary Carrier & Target Destination
| Cargo Substance | Primary Carrier | Point of Origin | Destination / Target | Primary Physiological Role |
|---|
| Oxygen (\(O_2\)) | RBCs (98.5%) / Plasma (1.5%) | Alveoli (Lungs) | All respiring tissues | Mitochondrial ATP production |
| Carbon Dioxide (\(CO_2\)) | Plasma (77%) / RBCs (23%) | Metabolizing cells | Pulmonary alveoli | Respiratory excretion & acid-base buffer |
| Glucose & Amino Acids | Plasma (Aqueous solute) | Small intestine / Liver | Skeletal muscle, brain, viscera | Instant cellular fuel & protein synthesis |
| Urea & Nitrogen Wastes | Plasma (Dissolved solute) | Liver (amino acid breakdown) | Renal nephrons (Kidneys) | Urinary excretion to prevent nitrogen toxicity |
| Hormones (Insulin, Epinephrine) | Plasma (Free or protein-bound) | Endocrine glands | Specific tissue target receptors | Systemic coordination & homeostasis |
| Thermal Energy (Heat) | Plasma (Aqueous heat sink) | Metabolic organs (liver, muscle) | Dermal capillary beds | Thermoregulation (heat radiation/sweating) |
Non-Transport Components: White Blood Cells (Leukocytes) fight infections via phagocytosis and antibody production; Platelets (Thrombocytes) aggregate to seal damaged vascular endothelium. Neither functions as a cargo transporter.
Defense & Repair
Student Investigation & Manifest Check Total Points: ______ / 25
Student Name:
Date:
Period:
Blood Cargo Transit Worksheet
Apply physiological principles to categorize transport mechanisms and trace systemic delivery routes.
1 Part 1: Carrier Allocation Matrix (8 Points)
Check the primary carrier and specify transport form / state
| Cargo Item | Carried by RBCs | Carried by Plasma | Transport Form / Chemical Mechanism |
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| 1. Oxygen Gas (\(O_2\)) | | | |
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| 2. Blood Glucose |
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| 3. Carbon Dioxide (\(CO_2\)) |
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| 4. Urea Waste |
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| 5. Adrenaline (Epinephrine) |
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| 6. Metabolic Core Heat |
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2 Part 2: Route Tracing & Delivery Mechanics (10 Points)
Scenario A: The Muscle Fuel Route
Trace how a glucose molecule travels from absorption in the small intestine to a working quadriceps muscle cell. Identify the specific blood carrier and how it enters the tissue.
Scenario B: The Dual \(CO_2\) Return
Explain why carbon dioxide produced in muscles relies on two distinct carriers to return to the lungs. Name both carriers and contrast their forms.
3 Part 3: Clinical & Comparative Analysis (7 Points)
Question 3.1: Severe dehydration decreases plasma volume by 15–20%. Explain two distinct transport crises this causes for cellular nutrition and internal thermoregulation.
Question 3.2: Why are white blood cells (leukocytes) not considered transport carriers, even though they circulate through the exact same blood vessels as red blood cells?
