Topic 24- Blood and Immunity

How many liters of blood does the average human have?

About 5 liters.

What are the main functions of blood?

Transport nutrients, oxygen, hormones; regulate fluid balance; defend against pathogens.

What is blood composed of?

Plasma and cellular components.

What percentage of plasma is water?

About 90%.

What do inorganic salts (electrolytes) in plasma do?

Buffer pH and regulate osmosis.

Name key plasma ions.

Calcium (Ca²⁺), Magnesium (Mg²⁺), Sodium (Na⁺).

What is the role of albumin in plasma?

Maintains osmotic balance.

What is the function of immunoglobulins?

Immune defense (antibodies).

What do apolipoproteins do?

Transport fats in the blood.

What is fibrinogen’s function?

Acts as a clotting factor.

Where are blood cells produced?

Bone marrow, from multipotent stem cells.

What is the structure of erythrocytes (RBCs)?

Biconcave, no nucleus or mitochondria, full of hemoglobin.

What is the function of red blood cells?

Transport oxygen efficiently.

What is the function of white blood cells (WBCs)?

Defend against infections and foreign substances.

What are platelets and their role?

Cell fragments essential for blood clotting.

What happens during platelet plug formation?

Platelets stick to exposed collagen and attract more platelets to form a plug.

What triggers fibrin clot formation?

A cascade involving clotting factors, Ca²⁺, prothrombin → thrombin → fibrinogen → fibrin.

What does fibrin do?

Forms long insoluble threads that reinforce the clot.

What is hemophilia?

A disorder where a clotting factor is missing → improper clotting.

What is a thrombus and why is it dangerous?

A blood clot that forms inside a vessel and can block blood flow → stroke or heart attack.

What does the immune system protect against?

Bacteria, viruses, fungi, parasites.

What are the two major branches of the immune system?

Innate immunity and adaptive immunity.

What are the features of innate immunity?

Immediate, general, non-specific; includes barriers and general cellular responses.

What are the features of adaptive immunity?

Specific, acquired, has memory; involves B and T cells.

What are examples of barrier defenses?

Skin, mucous membranes, cilia, stomach acid, lysozymes.

What do toll-like receptors (TLRs) do?

Recognize pathogen molecules to trigger a response.

What do NK (Natural Killer) cells do?

Destroy infected or cancerous host cells by detecting abnormal surface proteins.

What are interferons?

Proteins produced by virus-infected cells to warn neighbors.

What is the complement system?

A group of ~30 proteins that lyse pathogens by forming membrane pores.

What triggers the inflammatory response?

Injury/infection → histamine and cytokine release → vasodilation and immune cell recruitment.

What are the signs of inflammation?

Redness, heat, swelling (edema), pain.

What is systemic inflammation and what does it lead to?

Body-wide response → fever to boost immune function.

Compare and Contrast: Cellular vs. Plasma Components of Blood [Origin, Physical form, Major Elements, Key function, Proteins Present, Which cells have role in immunity]

Feature	Cellular Components	Plasma Components
Origin	Bone marrow (from stem cells)	Liquid portion of blood
Physical Form	Cells or cell fragments	Fluid (~90% water)
Major Elements	RBCs, WBCs, Platelets	Water, ions, proteins, nutrients, hormones
Key Functions	Oxygen transport, immunity, clotting	Transport, pH buffering, osmoregulation, clotting
Proteins Present?	Minimal in cells	Albumin, immunoglobulins, fibrinogen, apolipoproteins
Direct Role in Immunity?	WBCs involved directly	Immunoglobulins contribute

Sequence: Process of Blood Clotting

1. Injury to Blood Vessel

2. → Vessel constriction (vasoconstriction)

3. → Exposure of collagen fibers

4. → Platelet adhesion and plug formation

5. → Release of chemical signals

6. → Clotting cascade activation (factors + Ca²⁺)

7. → Prothrombin → Thrombin

8. → Thrombin converts fibrinogen → Fibrin

9. → Fibrin mesh stabilizes clot

Compare and Contrast: Platelet Plug vs. Fibrin Clot Formation

Feature	Platelet Plug Formation	Fibrin Clot Formation
Timing	Immediate (seconds to minutes)	Delayed (minutes to hours)
Trigger	Platelet contact with exposed collagen	Enzyme cascade + clotting factors
Main Component	Platelets	Fibrin (from fibrinogen)
Function	Temporarily plug the hole	Permanently seal and stabilize the clot
Calcium & Vitamin K?	Not essential	Essential for cascade and thrombin formation

Hypothesize/Diagnose: Impact of Variability on Blood Clotting

Variation / Deficiency	Possible Effect	Diagnosis / Outcome
Low Platelet Count	Impaired plug formation	Excessive bleeding, bruising
Hemophilia (Missing Factor)	Cascade blocked → no fibrin clot	Cannot form stable clot → persistent bleeding
Excess Clotting Factors	Clots without injury	Thrombus risk → stroke or heart attack
Vitamin K Deficiency	Thrombin can't form	Bleeding disorders
Calcium Deficiency	Clotting cascade impaired	Slower clot formation

Compare and Contrast: Innate vs. Adaptive Immunity

Feature	Innate Immunity	Adaptive (Acquired) Immunity
Specificity	Non-specific	Pathogen-specific
Response Time	Immediate	Delayed (days)
Memory?	No	Yes
Components	Skin, phagocytes, NK cells, complement	B cells, T cells, antibodies
Duration	Short-term	Long-lasting immunity
Present From Birth?	Yes	Develops after exposure

Compare and Contrast: Barrier vs. Cellular Innate Defenses

Feature	Barrier Defenses	Cellular Defenses
Location	Body surfaces (external/internal)	Inside tissues and blood
Example Structures	Skin, mucous membranes, stomach acid	Phagocytes, NK cells, interferons
Always Active?	Yes	Activated when barrier is breached
Type of Action	Physical/chemical prevention	Cellular response and pathogen destruction

Sequence: Innate Immune Response (9)

1. Pathogen Entry

2. → Breaches barrier defenses (e.g., skin, mucous membranes)

3. → Recognized by toll-like receptors (TLRs)

4. → Phagocytes engulf and destroy pathogen

5. → NK cells destroy infected host cells

6. → Interferons released (if virus present)

7. → Complement system activated → pathogen lysis

8. → Inflammatory response: vasodilation, cytokine release

9. → Phagocytes rush in → pathogen cleared

Sequence: Vaccine Activity

1. Vaccination (Injection of Antigen or mRNA)

2. → Antigen detected by immune system

3. → B cells produce antibodies

4. → T cells activated

5. → Memory B and T cells formed

6. → Future infection → rapid memory response

7. → Faster elimination of actual pathogen