Blood Components and Function

• Blood is the transport system in multicellular organisms including humans.

Blood Components

• Blood consists of plasma, platelets, red blood cells, and white blood cells.

Plasma

• Plasma transports blood cells, digested food products, carbon dioxide, urea, hormones, and heat energy.

Platelets

• Platelets are cell fragments that help in blood clotting.
• Platelets clump together to plug damaged blood vessels.
• Blood clotting prevents blood loss and microorganism entry.
• Platelets are held together by fibrin.

Red Blood Cells

• Red blood cells transport oxygen from the lungs to body cells.
• Red blood cells are small and biconcave-shaped for a large surface area for oxygen absorption.
• Red blood cells contain hemoglobin, which binds to oxygen to become oxyhemoglobin.
• Red blood cells don't have a nucleus, allowing more space for hemoglobin.

Blood Analysis

• Blood tests can diagnose various disorders by analyzing chemicals in the blood.

White Blood Cells and Immunity

• The immune system uses white blood cells to defend against pathogens.
• Pathogens are microorganisms that cause diseases.
• Two types of white blood cells are phagocytes and lymphocytes.

Phagocytes

• Phagocytes ingest pathogens.
• Phagocytes detect and engulf foreign matter (pathogens).
• Phagocytes are non-specific and attack anything not meant to be in the body.

Lymphocytes

• Lymphocytes produce antibodies specific to antigens on pathogen surfaces.
• Antibodies mark pathogens for destruction by other white blood cells.
• Memory cells are produced in response to a foreign antigen, providing immunity against future infections.

Vaccination

• Vaccination prevents infections by triggering an immune response without causing illness.
• Vaccination involves injecting dead or inactive pathogens, which carry antigens.
• Vaccination stimulates lymphocytes to produce antibodies and memory cells.
• If live pathogens appear, memory cells quickly produce antibodies.

Blood Vessels

• Blood vessels are tubes that carry blood around the body.
• Three types of blood vessels are arteries, capillaries, and veins.

Arteries

• Arteries carry blood away from the heart under high pressure.
• Artery walls are strong and elastic to handle high pressure.
• Elastic fibers allow arteries to expand, the walls are thick and contain muscle to keep them strong.
• The largest artery in the body is the aorta.

Capillaries

• Arteries branch into capillaries that are very small.
• Capillaries facilitate the exchange of materials and substances with cells.
• Capillary walls are permeable for diffusion and are usually one cell thick, to increase diffusion rate.

Veins

• Veins carry blood back to the heart at lower pressure than arteries.
• Vein walls are not as thick as artery walls.
• Veins have a larger lumen and valves to maintain blood flow direction.
• The largest vein in the body is the vena cava.

The Heart

• The heart is the pump that circulates blood around the body.
• The heart's right atrium receives deoxygenated blood from the body via the vena cava.
• Deoxygenated blood moves from the right atrium to the right ventricle, which pumps it to the lungs via the pulmonary artery.
• The left atrium receives oxygenated blood from the lungs via the pulmonary vein.
• The oxygenated blood moves from the left atrium to the left ventricle. The left ventricle pumps blood around the whole body via the aorta.
• The left ventricle has a thicker wall than the right ventricle.
• Heart valves prevent the backward flow of blood.

Exercise and Heart Rate

• Exercise increases the need for energy, leading to increased respiration.
• The process requires more oxygen and removal of carbon dioxide.
• The heart rate increases to facilitate blood flow, with receptors in the aorta and carotid artery detecting high CO₂ levels.
• Signals are sent to the brain, and the brain sends signals to the heart, causing it to contract more forcefully and frequently.

Hormonal Control of Heart Rate

• Threat triggers adrenaline release from the adrenal glands.
• Adrenaline binds to receptors in the heart, increasing heart rate and pumping more blood.

Circulation and Coronary Heart Disease

• The circulation system includes the heart and blood vessels to transport substances.
• Arteries typically carry oxygenated blood, while veins carry deoxygenated blood, except for the pulmonary artery and pulmonary vein.

Coronary Heart Disease

• Coronary heart disease involves blood supply restriction to the heart muscle.
• Fatty material builds up within the coronary arteries.
• Risk factors include a diet high in saturated fat, smoking, and inactivity.
• A high saturated fat diet leads to fatty deposits inside arteries.
• Smoking and inactivity increases blood pressure and lining of artery damage.

Excretion and Osmoregulation

• Excretion is the removal of waste products, especially by the kidneys.
• The kidneys remove urea, adjust ion levels, and regulate water content in the blood.
• The kidneys filter blood and reabsorb useful substances.

Nephrons

• The nephrons are filtration units within the kidneys.

Ultrafiltration

• The process filters water, urea, ions, and glucose from the blood into the Bowman's capsule.
• The ultrafiltration process retains proteins and blood cells in the blood.

Reabsorption

• Reabsorption is the selective reabsorption of useful substances back into the blood while the liquid flows along the nephron.
• The kidney recovers glucose, ions, and water.

Waste Release

• Wastes that aren't reabsorbed are released. These wastes form urine, passing through the ureter to the bladder.

Osmoregulation

• Osmoregulation balances water intake and loss in the body.
• Kidneys adjust water excretion through urine.
• The kidneys reabsorb more water when a person is sweating a lot, so less is lost in the urine.

ADH's role in Water Content

• Anti-diuretic hormone (ADH) regulates water content in the kidneys.
• High levels of ADH increase water reabsorption.
• Low levels of ADH decrease water reabsorption.
• A negative feedback mechanism controls osmoregulation, maintaining water content.
• Low blood water content increases ADH production and water reabsorption.
• High blood water content decreases ADH production and water reabsorption.