Blood Composition and Functions

Functions of Blood

• Blood transports oxygen, nutrients, hormones, and waste products throughout the body
• It regulates body temperature, pH, and fluid balance
• Blood protects the body against infections via white blood cells and prevents blood loss through clotting

Components of Blood

• Plasma, the liquid component, carries nutrients, hormones, and waste
• Red blood cells (RBCs) transport oxygen and carbon dioxide; they live for 120 days in bone marrow
• White blood cells (WBCs) and platelets fight infections and aid in clotting; they are produced in bone marrow and lymphatic organs

Plasma Proteins

• The liver primarily forms albumin, globulins, and fibrinogen
• Albumin makes up 54% of plasma protein, contributes to osmotic pressure, regulates water balance, blood pressure, volume, pH, and viscosity
• Globulins constitute 38% of plasma protein and include alpha, beta, and gamma (antibodies)
• Fibrinogen, 7% of plasma protein, is the largest molecule produced by the liver and plays a role in blood clotting

Blood Formation and Stimulating Hormones

• Hematopoiesis describes blood formation
• Erythropoietin, produced by the kidneys, stimulates red blood cell formation in bone marrow
• Thrombopoietin, produced by the liver and kidneys, regulates platelet production and stimulates megakaryocyte growth
• Colony-Stimulating Factors stimulate the production of various types of white blood cells

Hematocrit

• Hematocrit indicates the percentage of RBCs in blood
• High hematocrit can result from dehydration or living at high altitudes

Red Blood Cells (RBCs)

• RBCs are biconcave which increase their surface area, allowing efficient oxygen and carbon dioxide exchange
• Hemoglobin is a protein in RBCs that binds and releases oxygen in the lungs using its iron component

Erythropoiesis and Anemia

• Erythropoiesis produces RBCs in the bone marrow, regulated by erythropoietin
• Anemia involves low RBCs or hemoglobin, with types including iron-deficiency, sickle cell, and pernicious anemia

Substances for RBC Production

• Iron, B12, folic acid, erythropoietin, protein and amino acids, copper, and vitamin C are required

White Blood Cells (WBCs)

• Neutrophils fight bacterial infections
• Lymphocytes provide immunity through T cells and B cells
• Monocytes turn into macrophages that perform phagocytosis
• Eosinophils combat parasitic infections and allergies
• Basophils release histamine during allergic reactions

Leukocytosis and Leukopenia

• Leukocytosis signifies a high WBC count, indicating infection or inflammation
• Leukopenia signifies a low WBC count, often due to viral infections or bone marrow issues

Diapedesis and Chemotaxis

• Diapedesis is the process where WBCs move out of blood vessels into tissues to fight infections
• Chemotaxis is the movement of WBCs toward chemical signals, such as those at infection sites

Monocytes

• Monocytes leaving the bloodstream differentiate into macrophages or dendritic cells

Hemostasis

• Hemostasis stops bleeding via vascular spasm, platelet plug formation, and blood clotting
• Vascular spasm constricts damaged blood vessels
• Coagulation occurs when clotting factors activates a cascade leading to fibrinogen converting into fibrin

Plasma vs. Serum

• Serum is plasma without clotting factors

Thrombosis and Embolism

• Thrombosis is the formation of a blood clot within a vessel
• Embolism occurs when a clot or fragment travels and blocks a vessel

Clot Formation Steps

• Vascular spasm constricts the vessel to reduce blood flow
• Platelets adhere to the injury site
• Coagulation forms a fibrin clot to seal the wound

Blood Groups

• Blood groups include AB, O, B, and A
• AB blood lacks A and B antibodies and therefore does not react to any ABO type
• Type O+ is the most common, while Type AB- is the rarest

Rh Factor

• The Rh factor is a protein on RBCs
• If an Rh- mother has an Rh+ child, her immune system may produce antibodies against the child's RBCs in future pregnancies, causing hemolytic disease of the newborn
• Typically, the second and subsequent Rh+ children are at risk of hemolytic disease

Hemophilia

• Hemophilia is a genetic disorder that impairs blood clotting due to missing clotting factors

Anemia

• Anemia is characterized by a lack of RBCs or hemoglobin, leading to fatigue and weakness

Artery Conditions

• Atherosclerosis is the build-up of plaques in arteries
• Arteriosclerosis is the hardening of arteries due to aging or other factors

Thrombosis and Embolism Defined

• Thrombosis is a stationary blood clot in a vessel
• Embolism is a moving clot that can cause blockages

Disorders of Blood Cells

• RBC disorders include anemias, sickle cell disease, and polycythemia
• WBC disorders include leukemias, leukopenia, and leukocytosis

Heart Location

• The heart is located in the thoracic cavity between the lungs, in the mediastinum
• It is within a double-walled sac called the pericardium

Heart Apex

• The apex of the heart points towards the left side of the body

Heart Layers

• Epicardium is the outer layer
• Myocardium is the middle, muscular layer
• Endocardium is the inner layer

Heart Septa

• The interatrial septum separates the atria
• The interventricular septum separates the ventricles

Heart Chambers

• The heart contains the right atrium, right ventricle, left atrium, and left ventricle

Heart Valves

• The tricuspid valve is between the right atrium and right ventricle
• The bicuspid (mitral) valve is between the left atrium and left ventricle

Cuspid Valves

• Chordae tendineae ("heartstrings") connect the cuspid valves to the papillary muscles
• Chordae tendineae and papillary muscles control the movement of the cuspid valves, preventing backflow

Circulation

• In pulmonary circulation, blood flows from the right ventricle to the pulmonary arteries, to the lungs, to the pulmonary veins, and then to the left atrium
• In systemic circulation, blood flows from the left ventricle to the aorta, to the body tissues, to the venae cavae, and then to the right atrium

Blood Oxygenation

• The left side of the heart handles oxygenated blood
• The right side of the heart handles deoxygenated blood

Heartbeat

• Specialized cardiac muscle fibers called Purkinje fibers cause the heart to beat as part of the heart's conduction system

Electrical Impulse Conduction

• The electrical impulse spreads through the sinoatrial (SA) node, atrioventricular (AV) node, Bundle of His, bundle branches, and Purkinje fibers

EKG Waves

• The P wave represents atrial depolarization
• The P to Q interval represents conduction time from atrial to ventricular excitation
• The QRS complex represents ventricular depolarization
• The T wave represents ventricular repolarization

Cardiac Cycle

• The cardiac cycle includes systole (contraction) and diastole (relaxation) of the atria and ventricles

Heart Imaging

• Echocardiograms use ultrasound to create images of the heart

Heart Attack

• Myocardial infarction (MI) is the medical term

Ischemia, Infarct, and Stroke Volume

• Ischemia is reduced blood flow to tissues causing a lack of oxygen
• Infarct is tissue death due to prolonged lack of blood supply
• Stroke Volume represents the amount of blood pumped by a ventricle in one heartbeat

Cardiac Output

• Cardiac output (CO) is the total amount of blood the heart pumps per minute (CO = Stroke Volume x Heart Rate)

Lipoproteins

• LDL (Low-Density Lipoprotein) transports cholesterol to tissues, with excessive amounts leading to plaque buildup
• HDL (High-Density Lipoprotein) removes excess cholesterol from tissues and transports it to the liver for disposal

Arteries and Veins

• Arteries carry oxygenated blood away from the heart, except for pulmonary arteries
• Veins carry deoxygenated blood to the heart, except for pulmonary veins

Myocardium

• Coronary arteries supply oxygenated blood to the myocardium

Anastomoses

• Anastomoses are connections between two blood vessels that provide alternate routes for blood flow

Artery vs. Vein Walls

• Arteries have thicker walls with more elastic fibers and smooth muscle for high-pressure blood flow
• Veins have thinner walls with valves to prevent backflow at lower pressure

Capillaries

• Capillaries consist of the tunica intima (one endothelial cell layer)
  • Continuous capillaries are found in muscles and lungs and are the least permeable
  • Fenestrated capillaries are found in kidneys and intestines and allow filtration via pores
  • Sinusoidal capillaries are found in the liver and spleen and are the most permeable

Blood Reservoirs

• Veins and venules are major blood reservoirs, storing 60-70% of total blood volume

Varicose Veins

• Varicose veins are enlarged, twisted veins caused by weakened valves, leading to blood pooling

Capillary Exchange

• Diffusion moves substances like oxygen and CO2 down their concentration gradient
• Transcytosis transports large molecules via vesicles
• Bulk flow moves fluids driven by pressure gradients

Bulk Flow

• Includes filtration (fluid leaving capillaries) and reabsorption (fluid re-entering)
  • Hydrostatic pressure pushes fluid out
  • Osmotic pressure pulls fluid in
• NET Filtration Pressure = (Capillary Hydrostatic Pressure - Interstitial Hydrostatic Pressure) - (Capillary Osmotic Pressure - Interstitial Osmotic Pressure)

Blood Flow Velocity

• Blood flow is slowest in capillaries, allowing for gas and nutrient exchange

Blood Pressure

• Blood pressure (BP) is the force exerted by blood on vessel walls
  • Systolic BP is pressure during ventricular contraction
  • Diastolic BP is pressure during ventricular relaxation

Vascular Resistance

• Vascular resistance is resistance to blood flow caused by vessel diameter, blood viscosity, and vessel length
• Factors affecting resistance:
  • Smaller lumen size increases resistance
  • Thicker blood increases resistance
  • Longer vessels increase resistance

Venous Return

• Venous return is the flow of blood back to the heart via veins
• Mechanisms that assist it include
  • Skeletal muscle pump: Contraction "milks" blood through veins
  • Respiratory pump: Pressure changes during breathing aid blood movement

Hypertension

• Hypertension is the technical name for high blood pressure

Arteries and Veins

• Arteries include the aorta and pulmonary arteries
• Veins include the superior vena cava and pulmonary veins

Fetal Blood Flow

• The foramen ovale is a hole in the interatrial septum that allows blood in the fetus to bypass the lungs and flow directly from the right atrium to the left atrium
• It closes after birth

Hepatic Portal System

• The hepatic portal system transports nutrient-rich blood from the digestive organs to the liver for metabolism and detoxification