TLDR;
Alright guys, so in this video, Dr. Johari is breaking down blood physiology. He covers the definition of blood, its composition (plasma and formed elements), the types of blood cells (RBCs, WBCs, platelets), plasma components (water, gases, organic and inorganic substances), blood properties (colour, volume, pH, viscosity), and functions (nutrition, respiration, excretion, transport, regulation, temperature control, storage, and defense). It's a crash course on blood, perfect for MBBS students prepping for exams.
- Blood is a specialized connective tissue composed of plasma and formed elements.
- Blood cells include RBCs (oxygen transport), WBCs (immunity), and platelets (clotting).
- Plasma contains water, gases, proteins, electrolytes, and other substances.
- Blood functions include nutrient transport, respiration, waste removal, and immunity.
Blood Definition and Composition [0:30]
Blood is a specialized connective tissue in fluid form. It consists of blood cells (RBCs, WBCs, and platelets) and plasma. Plasma makes up 55% of blood, with 92% of it being water. WBCs and platelets account for 4%, while RBCs make up the remaining 41%. The red colour of blood is due to RBCs containing haemoglobin.
Formed Elements: RBCs, WBCs, and Platelets [1:59]
The formed elements in blood include RBCs (erythrocytes), which carry oxygen via haemoglobin. Platelets are responsible for blood clotting. WBCs (leukocytes) are divided into granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (monocytes, lymphocytes). Granulocytes have granules in their cytoplasm, while agranulocytes do not. Neutrophils and monocytes perform phagocytosis, engulfing bacteria. Eosinophils have a double-lobed nucleus, and basophils are also present. Lymphocytes include B and T lymphocytes, which provide immunity.
Plasma Composition [5:16]
Plasma is composed of 92% water, gases (oxygen, carbon dioxide, nitrogen), and 7-8% solid materials. Solid materials include organic (plasma proteins, amino acids, carbohydrates, fats, hormones, enzymes) and inorganic substances (electrolytes). The main plasma proteins are albumin, globulin, and fibrinogen. Non-protein nitrogen substances include waste products like ammonia, creatinine, urea, and uric acid. Plasma also contains antibodies.
Types and Quantities of Blood Cells [7:10]
RBC count ranges from 4 to 5.5 million per cubic mm, with males having around 5 million and females around 4.5 million. Neutrophils make up 50-70% of WBCs, numbering 3000-6000. Eosinophils are 2-4% (150-450), basophils are the least common at 0-1% (0-100). Monocytes are 2-8% (200-600), and lymphocytes are 20-30% (1500-2700). Neutrophils have a multi-lobed nucleus, eosinophils have a headphone-shaped nucleus, basophils appear purple, monocytes have a kidney-shaped nucleus, and lymphocytes have a nucleus that covers most of the cytoplasm.
Properties of Blood [8:55]
Oxygenated blood is scarlet red, while deoxygenated blood is purple-red. A healthy individual has about 5 litres of blood, which is approximately 8% of body weight. The pH of blood is slightly alkaline at 7.4. Blood's viscosity is about five times greater than water.
Functions of Blood [9:39]
Blood provides nutrition by transporting digested nutrients from the alimentary canal to tissues. It aids respiration by carrying oxygen from the lungs to tissues via haemoglobin in RBCs. Blood also performs excretion by transporting waste products to the kidneys for removal. Hormones are transported via blood from endocrine glands. Blood regulates water balance, acid-base balance (through plasma proteins and haemoglobin acting as buffers), and body temperature (due to its high specific heat). It also functions as a storage site for proteins, glucose, sodium, and potassium. Finally, blood provides defense through WBCs like neutrophils and monocytes (phagocytosis) and lymphocytes (immunity via B and T cells).