Blood

Overview of Blood Composition and Functions

Clotting Factors: Involved in blood coagulation.
Fibrinogen: A protein that activates to fibrin during the final phase of clotting, crucial for clot formation.

Fluid Matrix: Contains potential fibers during clotting; fibrinogen is activated to fibrin.

White Blood Cells (Leukocytes): True cells with a nucleus. Responsible for various immune responses. Types include:
- Neutrophils: Most common type, characterized by a multilobed nucleus (appears as blobs).
- Lymphocytes: Second most common; includes B cells and T cells, which produce antibodies and have large, dominant nuclei.
- Monocytes: Third most common; larger than other cells, with a horseshoe-shaped nucleus.
- Eosinophils: Rare leukocytes with two connected lobes in the nucleus and pink-staining granules.
Red Blood Cells (Erythrocytes):
- Characteristics: Carry oxygen due to hemoglobin, which contains iron and gives red color.
- They are not true cells (classified as formed elements) because they lack a nucleus, allowing more space for hemoglobin.
- Function: Transport oxygen, and due to their inability to repair themselves, they must be continuously produced.
- Lifespan: Short; they cannot regenerate.
Platelets (Thrombocytes):
- Tiny cell fragments involved in clotting.

Abundance: Erythrocytes are much more abundant than leukocytes in the blood.

Transport Functions:
- Gases: Oxygen and carbon dioxide transport; oxygen is poorly soluble in blood plasma.
- Nutrients: Carried to tissues and organs.
- Waste Products: Transportation of wastes like urea and uric acid.
- Hormones and Electrolytes: Also transported in the blood.
Protection: Hemostasis and Immune Response:
- Clotting prevents blood loss (hemostasis).
- Leukocytes travel to infection sites, promote inflammation, and produce antibodies to mark pathogens for destruction.

Fluid Levels and Blood Pressure:
- Blood plasma primarily consists of water; volume is directly related to blood pressure.
pH Regulation:
- Importance of maintaining blood pH between 7.35 and 7.45 to ensure enzyme activity and metabolic processes.
- Carbon Dioxide’s Role: Dissolves to form carbonic acid, serving as a buffer to maintain pH.
- Carbonic Acid and Bicarbonate Pair:
  - A weak acid that partially dissociates to stabilize pH levels.
  - Functions as a buffer system, preventing drastic pH changes.
- Effects of pH Alterations:
  - Acidosis (pH < 7.35) and alkalosis (pH > 7.45) disrupt cellular function and can affect metabolism.
Temperature Regulation: Blood distributes heat throughout the body, affecting peripheral circulation, especially in cold conditions.

Blood as a Connective Tissue:
- Comprised of formed elements (cells and fragments) and plasma (extracellular matrix).
- True Cells vs. Formed Elements:
- True cells: leukocytes (have nuclei).
- Formed elements: erythrocytes (no nuclei) and platelets (cell fragments).

Hematocrit Procedure:
- Blood is drawn and centrifuged, separating components by density:
- Denser erythrocytes settle at the bottom.
- Thin layer of leukocytes and platelets (buffy coat) above.
- Plasma remains at the top (typically about 55% of whole blood).
- Normal ranges: 45-55% erythrocytes in males, 37-47% in females; influenced by testosterone in males.

Physical Properties:
- Sticky, opaque, with a metallic taste due to iron in hemoglobin.
- Color changes based on oxygenation: bright red when oxygenated (systemic arteries) and darker red when deoxygenated (veins).
Average Blood Volumes:
- Males: 5-6 liters.
- Females: 4-5 liters.
- Blood constitutes approximately 8% of total body weight.

Understanding blood composition and functions is fundamental for multiple aspects of health and physiology. Continued examination of these functions will enhance our comprehension of homeostasis and bodily regulation.
Preparation for upcoming discussions on the laboratory practices will enhance practical understanding of blood function and safety.