Blood and Immunity Basics - Bio 20 Alberta

Welcome to our exploration of blood components! Blood is a fascinating tissue made up of four main elements.Let's start by looking at a cross-section of a blood vessel.The liquid portion of blood is called plasma, making up about fifty-five percent of total blood volume.Red blood cells, or erythrocytes, are the most numerous blood cells, comprising about forty-five percent of blood volume. Their main job is carrying oxygen using hemoglobin.White blood cells, though less than one percent of blood volume, are crucial for immune defense. They come in several types, each with specific roles in fighting infection.Platelets are tiny cell fragments that help form blood clots when blood vessels are damaged. They work with clotting factors in plasma to prevent blood loss.Together, these components maintain proper blood function. Let's look at their relative proportions in healthy blood.The human immune system consists of two main types of defense mechanisms.Innate immunity serves as our body's first line of defense, featuring physical barriers and quick responses.When pathogens breach these barriers, the body responds with inflammation and fever.Adaptive immunity, on the other hand, is more specialized and develops over time.B-cells produce specific antibodies that target particular pathogens.The adaptive immune system creates memory cells, allowing for faster responses to repeated exposures.Let's examine how these two systems respond over time during an infection.The innate immune response activates immediately but gradually decreases.The adaptive response takes longer to develop but provides longer-lasting protection.When a pathogen enters the body through the bloodstream, it triggers a complex immune response.The first responders are innate immune cells like neutrophils and macrophages.These cells identify and attempt to destroy the invaders through a process called phagocytosis.If the infection persists, the adaptive immune system activates. B-cells begin producing antibodies specific to the pathogen.These antibodies are like specialized keys that can lock onto and neutralize specific pathogens.Meanwhile, T-cells directly attack infected cells and coordinate the immune response.After the infection is cleared, some B and T cells become memory cells, ready to respond quickly if the same pathogen returns.