Blood Composition and Physiology

General blood composition

Blood is a complex tissue, responsible for transporting various substances, including fatty acids, cholesterol, lipoproteins, phosphoglycerides, bilirubin, calcium, steroids, hormones, amino acids, and drugs.
Blood's density is approximately double that of water.
The pH of blood is approximately 7.4.
Hematocrit is the percentage of red blood cells in blood.

Proerythroblast is the first recognizable cell in the red blood cell lineage.
Blood cells develop from CFU-E stem cells.
Erythroblasts have increasing concentrations of hemoglobin, leading to cell maturation.
Reticulocytes are immature red blood cells, distinguished by remaining cytoplasmic material.
Immature cells pass through the bone marrow to blood capillaries.

Blood and various ions

Carbonate plays a key role in acid-base balance and carbon dioxide transport in blood.
Plasma proteins maintain the osmotic pressure and regulate water balance in blood.
Red blood cells carry oxygen from the lungs to the tissues and carry carbon dioxide to the lungs.

Leukocytes and their functions

Leukocytes are a key part of the body’s defense system and are mobile units of the body's protection.
Neutrophils have granules and are important in phagocytic function in tissues.
Lymphocytes are involved in important immune functions at tissue level.
Monocytes are precursors of tissue macrophages.
Macrophages are phagocytic cells that play a vital role in immunity by engulfing pathogens and cellular debris and releasing their products into the lymph.

Inflammation

Inflammation is a complex biological response to harmful stimuli, such as pathogens, damaged cells, or irritants, resulting in a cascade of reactions to isolate the damaged area and deal with the harmful stimuli.
Neutrophils, macrophages and monocytes are important cells involved in the inflammatory response.
Local and systemic reactions develop against inflammation.
The response has multiple lines of defense in order to solve the problem, including tissue macrophages, neutrophils, monocytes (which become macrophages) and increased progenitor cell-production in the bone marrow.

Immune system and Immunity

The thymus is a bilobed organ, involved in T cell development and maturation.
The spleen is a primary lymphoid organ, with a primary role in the innate and adaptive/acquired immune response.
Tissue macrophages are an important component of the alveolar wall and they phagocyte the particles that become entrapped in the alveoli.

Blood clotting

Fibrin-stabilizing factor stabilizes the fibrin network in a blood clot.
Thrombin converts fibrinogen to fibrin, crucial for clot formation.
The intrinsic and extrinsic pathways operate simultaneously in the clotting cascade;
Calcium plays a key role in blood coagulation.

Pulmonary ventilation

Pulmonary ventilation involves the inflow and outflow of air between the atmosphere and alveoli in the lungs.
Key components involved in respiration include, the diaphragm, external intercostals, and abdominal muscles.
Elastic forces of the lungs contribute to their collapse and expansion.

Complement system

The complement system is part of the innate immune system and consists of a collection of proteins in the blood that work together to destroy pathogens and enhance the inflammatory response.
It has various roles such as chemotaxis, opsonization, and cell lysis of pathogens.

Hemostasis

Hemostasis is the process of preventing blood loss.
Platelets contribute by forming blood clot (by activation of platelets, fibrin and thrombin).
Hemostasis involves initiating a vascular constriction and formation of a platelet plug, formation of blood clot and eventual growth of fibrous tissue into the clot.

Blood circulation and blood flow

•Blood flow through peripheral tissues is tightly regulated to meet cellular demands.. •Blood flow is a measure of volume passing a point in the circulatory system per unit time. •Arteries and arterioles have a role in distributing blood and regulating its flow under pressure to different organs and tissues in the body. •Venules and veins are involved in collecting blood and directing it back to the heart.