MD137 Haematology Lecture 1

Study Notes

MD137 Haematology - Lecture 1

Topic: Functions & Composition of Blood
Learning Objectives: Understanding blood functions, constituents, plasma characteristics, and formed elements.

Functions of Blood

Transport: Oxygen (O₂), Carbon Dioxide (CO₂), Nutrients, Waste products, Hormones, and Transport of hormones.
Maintenance of Homeostasis: Regulation of pH (acidity), Temperature Regulation (Heat).
Immunity: White blood cells, Antibodies and other mediators, Blood clotting processes in balance with the prevention of Blood clotting, Haemostasis.

Properties of Blood

Composition: ~8% of body weight.
Female: 4-5L.
Male: 5-6L.
pH: 7.35 - 7.45.
Osmolarity: 285 - 295 mOsm/L.
Viscosity: 3.5-5.5 times that of water (resistance to flow).
Density/Specific Gravity: 1.05 g/ml.
Composition of Blood: Formed elements (45%) and Plasma (55%).

Blood Collection and Centrifugation

Anticoagulants: EDTA, Citrate, or Heparin are used to prevent clotting.
Centrifugation: Separates blood components: Plasma (55%), Buffy Coat(leukocytes and platelets ~<1%), Erythrocytes(red blood cells, 45%).

Haematocrit (Packed Cell Volume - PCV)

Definition: Percentage of blood occupied by red blood cells (RBCs).
Females: 0.37 -0.47.
Males: 0.42 -0.52.
Decreased Haematocrit: Possible causes need to be investigated
Elevated Haematocrit: Possible causes need to be investigated

Constituents of Blood

Plasma: 55% of blood volume.
- Primarily water (91-93%).
- Proteins (6-8%).
- Other substances (Nutrients, glucose, lipids, amino acids, nitrogenous wastes, gases, electrolytes, hormones).
Formed Elements: 45% of blood volume.
- White blood cells (Leukocytes): Involved in immunity. Different types with varying abundance and functions.
- Red blood cells (Erythrocytes): Responsible for oxygen transport.
- Platelets (Thrombocytes): Crucial for blood clotting.

Plasma Proteins

Albumin (60%): Major contributor to blood viscosity, fluid balance (oncotic pressure), and carries hormones/drugs.
Globulins (36%): Transport lipids, vitamins and hormones - includes antibodies produced in lymphoid tissue
Fibrinogen (4%): Essential for blood clotting.
Other (≤ 1%): Regulatory proteins like enzymes and hormones.

Formed Elements/ Blood Cells

Erythrocytes (Red Blood Cells):
- Shape: Biconcave disks, large surface area for efficient gas exchange.
- Size: 6-8μm diameter, 2.5μm thick.
- Nucleus: Absent.
- Mitochondria: Lack mitochondria, produce energy anaerobically.
- Lifespan: ~120 days.
Erythrocyte/RBC Functions:
- Oxygen Transport: 99% bound to hemoglobin.
- Carbon Dioxide Transport: 10% dissolved, 30% bound, 60% as bicarbonate.
- pH Regulation: Key component of bicarbonate buffer system.
Leukocytes (White Blood Cells):
- Function : Immunity, defense mechanism.
- Types: Granulocytes (polymorphonuclear leukocytes) , Agranulocytes (mononuclear leukocytes).
  - Neutrophils, Eosinophils, Basophils, Lymphocytes, and Monocytes.
Thrombocytes (Platelets):
Origin: Megakaryocytes
Size: 1.5 - 3μm
Nuclei: No nucleus
Mitochondria: Present
Lifespan: ~10 days.
Function: Essential for blood clotting, prevent blood loss, wounds healing, tissue integrity, and immune function.

Regulation of Blood pH

Bicarbonate System: Cytoplasm has carbonic anhydrase catalyzing the formation of carbonic acid, which then dissociates into bicarbonate and hydrogen ions.
Hemoglobin: Binds produced H+ ions from carbonic acid, acts as a buffer in the plasma.

Leukocytes and Their Types

Differential White Blood Cell Count: Measurement of various white blood cell types.
Types: Neutrophils (most abundant), Lymphocytes, Monocytes, Eosinophils, and Basophils. Each type has unique characteristics, functions, and properties

Description

This quiz covers the essential functions and composition of blood in MD137 Haematology, specifically focusing on topics such as blood transportation, homeostasis, and immunity. Understand the key properties of blood, including its composition, viscosity, and pH levels. Test your knowledge on blood collection techniques and anticoagulants used in laboratory practices.