Blood Components and Functions

Formed Elements of Blood Composition

• Blood consists of formed elements and plasma.
• The body is composed of 92% other fluids and tissues, and 8% blood.
• Plasma makes up 55% of blood volume.
• Formed elements make up approximately 45% of blood volume.

Blood Composition

• The average total blood volume in an adult is approximately 5 to 6 liters.
• Plasma is approximately 91% water and 7% proteins.
• Plasma is composed of 2% other substances like electrolytes, nutrients, gases, waste products and regulatory substances.
• Formed elements are composed of red blood cells (RBCs), white blood cells (WBCs), and platelets.
• WBCs include neutrophils, lymphocytes, monocytes, eosinophils, and basophils.
• Albumins are proteins in plasma; an increased level indicates dehydration.
• Globulins are larger and less soluble proteins in plasma that can cross membranes
• Fibrinogen is a soluble plasma glycoprotein that converts to fibrin during coagulation.

Blood functions

• Transports oxygen to tissue cells and carbon dioxide to the lungs.
• Transports nutrients and waste products.
• Transports processed molecules from one part of the body to another, such as lactic acid being carried by blood to the liver.
• Transports regulatory hormones and enzymes.
• Regulates pH and osmosis.
• Maintains body temperature.
• Protects against foreign substances.
• Forms clots.

RBCs (Erythrocytes)

• The primary function is transporting oxygen from the lungs to tissues and carbon dioxide from tissue cells to the lungs.
• Normal range is 4-6 million/mm³.
• RBCs are formed in the bone marrow.
• The body will compensate for chronic hypoxemia by creating more RBCs to carry oxygen.
• A high RBC count is called polycythemia, which can be seen in chronic COPD patients.
• A low RBC count indicates anemia, which can be due to blood loss, autoimmune diseases, or menstrual cycles.
• Hematocrit measures the % of RBC in the original blood volume after spinning in a centrifuge.
• Normal hematocrit range = 40-50%.
• Low hematocrit indicates anemia, while high indicates polycythemia.
• Hemoglobin carries 1.34 ml of oxygen per gram.
• Normal Hemoglobin is 12-16 gm/100mL blood (g/dL)
• Primary functions of hemoglobin is to transport oxygen/ carbon dioxide from the lungs to tissue cells
• Graham’s Law quantifies diffusion.

Anemia

• A deficiency of Hb in the blood, common causes include:
• Nutritional deficiency (iron deficiency anemia)
• Hemorrhagic anemia
• Folate deficiency
• Pernicious anemia due to inadequate intake of Vitamin B12 which is important for folate synthesis
• Hemolytic anemia where red blood cells rupture or destroyed at an excessive rate.
• Aplastic anemia where there’s an inability of bone marrow to produce
• Sickle cell

WBCs (Leukocytes)

• Protect the body against invading microorganisms and fight against infections.
• Classified as granulocytes or agranulocytes, with a normal range of 5,000 – 10,000 / mm³.
• Leukocytosis = Increase in WBC = Increased WBC, Leukopenia = Decreased WBC = Decreased WBC
• Granulocytes include neutrophils (60% of all WBC), eosinophils (2% of WBC) and basophils(1% of WBC.
• Neutrophils will Increase w/ bacterial infections, and decrease w/ viral infections
• Eosinophils will Increase with allergic reaction (asthma) and produces yellow sputum
• Basophils is the Least common and Increased with allergies

Lymphocytes & Monocytes

• They are Agranulocytes
• Lymphocytes: 30% of WBC
• Decreased with Sepsis, SLE (systemic lupus erythematosus
• Increased in allergic reactions and autoimmune diseases
• Monocytes: 3% of WBC and is Associated with TB

Additional Granulocytes Facts

• Neutrophils: Under normal conditions, neutrophil numbers average approximately 60% of total WBC count with mobile, active phagocytic cells
• Cytoplasmic granules in neutrophils contain powerful digestive like enzymes that phagocytize invading bacteria
• Eosinophils Normally, make up approximately 2% of circulating WBCs and found in Numerous in tissue lining respiratory and digestive tracts that Destroy protozoa and parasitic worms and release anti-inflammatory substances in antigen–antibody reactions.
• Elevated eosinophil count commonly seen in asthmatic patients
• Basophils: Accounts for Only 1% of total count with Cytoplasmic granules containing histamine and heparin
• Histamine: Inflammatory substance that causes vasodilation and attracts other WBCs to inflamed site
• Heparin:Inhibits blood clotting (anticoagulant)
• Basophils increase in number in both allergic and inflammatory reactions

Additional Agranulocytes Facts

• Lymphocytes: Second most numerous leukocytes and found in lymphoid tissues (lymph nodes) to Play several important roles in immunity
• Monocytes: It Accounts for 3% that Differentiate into highly mobile macrophages with large appetites to Phagocytize bacteria, dead cells, cell fragments, and viral-infected cells and Increase in number associated with chronic infections (TB)
• Platelets are Also known as thrombocytes which is also the Smallest of formed elements in plasma
• Normal count ranges from 150,000 to 400,000/mm³ of blood with the Play important role in preventing blood loss from traumatized area by: Forming platelet plugs that seal holes in small blood vessels

Heart Anatomy

• The heart is a hollow, four-chambered, muscular organ about the size of a fist.
• The heart wall is composed of three layers: epicardium, myocardium (muscle tissue), and endocardium.
• Forms thin continuous tissue with blood vessels around the Upper chambers, right and left atria and Lower chambers are right and left ventricles which are Responsible for forward movement of blood

The Pericardium

• A double-walled sac enclosing the heart which consists of two layers: Fibrous and Serous
• Fibrous: Tough, loose-fitting, and inelastic sac surrounding the heart
• Serous: Consisting of two layers:
  • Parietal: Inner lining of the fibrous pericardium
  • Visceral layer or epicardium: Covering the outer surface of the heart and great vessels

Additional Heart Anatomy

• Pericarditis is inflammation in the pericardium which have Fluid separates parietal and visceral pericardium to helps minimize friction during contraction and expansion, same concept of pleural space in the lung
• Pericardial effusion can cause Abnormal amount of accumulated fluid between layers which can develop into Cardiac Tamponade which can cause shock and death
• AV valves lie between atria and ventricles
  • Tricuspid valve is at right atrium exit and Mitral valve at left atrium exit
  • Ventricular contraction forces valves closed, preventing backflow of blood into atria
  • Lower ends of valves anchor to ventricular papillary muscles by chordae tendineae in the Papillary contraction during systole which pulls on chordae, preventing valve reversing into atria

Heart Valves

• Semilunar Valves Consist of three half-moon–shaped cusps
• The Separate ventricles from their arterial outflow tracts like in the Pulmonary artery and aorta or Situated at ventricle exits to outflow tracks (arterial trunks as Pulmonary valve lies between right ventricle and pulmonary artery or Aortic valve lies between left ventricle and aorta
• During Systole, valves open, allowing ventricular ejection into arteries (pulmonary artery and aorta) where the Valves close during Diastole preventing back flow of blood into ventricles
• Regurgitation: the backflow of blood through an incompetent or a damaged valve
• Stenosis: a pathologic narrowing or constriction of a valve outlet, which causes increased pressure in the proximal chamber and vessels in the Coronary Circulation
• Two main coronary arteries arise from the root of the aorta as coronary artery pressure becomes higher than aortic pressure during systole such that Blood flow through the coronary arties occur during diastole.
• Partial obstruction leads to tissue ischemia (decreased oxygen supply) causing angina or Tissue death is called infarction and is called Myocardial Infarction (MI).

Problems With Coronary Blood Flow

• Myocardial Ischemia: Partial obstruction (Aka Angina Pectoris) where there is a Decrease in the oxygen supply to tissue
• Myocardial Infarction (MI): Complete obstruction of the coronary artery or causes Death of the heart tissue which is what they call cardiac arrest
• Treatment for Blocked Coronary Arteries - Most common cause of MI is Thrombus forming (blood clot) and blocking the coronary artery
• Diagnoses is done with a Cardiac catheterization and can be treated with Angioplasty or Balloon angioplasty or by inserting Stent and lastly a Coronary bypass

Properties of Heart Muscle

• Contractility the contraction in response to electrical impulse
• Vasculature : The System Composed of two major subdivisions: Systemic and Pulmonary
• Systemic vasculature begins with aorta on left ventricle and ends in right atrium where as:Pulmonary vasculature begins with pulmonary trunk out of right ventricle and ends in left atrium. and that The Systemic venous blood returns to right atrium to:
• The Superior vena cava (SVC) which drains upper extremities and the head
• The Inferior vena cava (IVC)Drains the lower body . - Blood flows through the tricuspid valve into right ventricle

Cardiac Terminology

• SVR = vascular resistance : Sum of all opposing forces to blood flow through systemic circulation
• SVR = Change ( in pressure from beginning to end of system, divided by flow
• Beginning pressure is the mean aortic pressure; end pressure equals right atrial pressure or Central Venous Pressure (CVP) PVR = sum of all opposing forces to blood flow through pulmonary circulation. Beginning pressure is the mean pulmonary artery pressure ending pressure equals left atrial pressure PVR: normally much lower than SVR as pulmonary system is low pressure, low resistance Cardiac output is the amount of blood discharged from the left or right ventricle per minute and TheStroke volume is the amount of blood ejected by the left ventricle at each heartbeat Stroke volume and heart rate directly influences blood pressure when there is anincrease/decrease

Blood Pressure and Cardiac Output

• MAP = ((Diastolic x 2) + Systolic) / 3
• Normal MAP is around 80-100 mmHg, below 60mmHg indicates that the brain and kidneys have severely compromised and there is organ failure
• Cardiac output (CO) = total amount of blood pumped by heart per minute Normal CO = 5 L/min
• Volume (EDV): blood left in atria which indicate anEjection Fraction (EF) The percentage of blood emptied from the ventricles during systole when EF decreases there is heart failure reduced function

Fluid Management

• Preload essentially equals venous return to right heart (measured by CVP) Afterload: resistance against which ventricles pump, so more afterload makes it harder for ventricles to eject SV.