BIOS exam 5

Major Function of Blood

Serves as the primary transportation medium for gases, nutrients, hormones, and metabolic wastes; also regulates pH, temperature, and provides immune protection.

Major Function of the Heart

Acts as a dual-pump system generating the hydrostatic pressure required to propel blood through both the pulmonary and systemic circuits.

Major Function of Blood Vessels

Provides a closed system of conduits for blood distribution, exchange at the capillary level, and return of blood to the heart.

General Composition of Blood

A specialized connective tissue consisting of a liquid extracellular matrix called plasma (approx. 55%) and cellular components known as formed elements (approx. 45%).

Composition of Blood Plasma: Water

Comprises 90-92% of plasma; acts as a solvent for transport and a medium for heat absorption and distribution.

Composition of Blood Plasma: Solutes

Includes electrolytes (Na+, K+), nutrients (glucose), metabolic wastes (urea, bilirubin), and dissolved gases (O2, CO2).

Plasma Protein: Albumin Production

Synthesized exclusively by the liver.

Albumin Function

The primary contributor to colloid osmotic pressure; also transports fatty acids and steroid hormones in the blood.

Plasma Protein: Globulin Production

Produced by the liver (alpha and beta) and by plasma cells/B-lymphocytes (gamma globulins/antibodies).

Plasma Protein: Globulin Function

Alpha and beta types transport lipids and fat-soluble vitamins; gamma types provide specific immunity by binding to pathogens.

Plasma Protein: Fibrinogen Production

Synthesized by the liver.

Plasma Protein: Fibrinogen Function

Acts as a soluble precursor that is converted into insoluble fibrin strands to form the framework of a blood clot.

Erythrocyte Morphology

Biconcave, enucleate discs approximately 7-8 micrometers in diameter; the shape increases surface area for gas exchange and allows for high flexibility.

Erythrocyte Function

Specialized for the transport of oxygen via hemoglobin and the transport of approximately 23% of total circulating carbon dioxide.

Leukocyte Morphology

Complete cells containing a nucleus and organelles; classified into granulocytes (with visible granules) and agranulocytes.

Leukocyte Function

Responsible for immune defense, including phagocytosis, antibody production, and the modulation of the inflammatory response.

Platelet (Thrombocyte) Morphology

Minute, disc-shaped cellular fragments derived from the fragmentation of megakaryocytes; they lack a nucleus but contain secretory granules.

Platelet (Thrombocyte) Function

Essential for hemostasis; they form a physical plug and release chemical factors that initiate the coagulation cascade.

Leukocyte Prevalence Order

Neutrophils (50-70%), Lymphocytes (20-40%), Monocytes (2-8%), Eosinophils (2-4%), Basophils (<1%).

Leukocyte Function: Neutrophils

Highly mobile phagocytes that act as first responders to bacterial infections and acute inflammation.

Leukocyte Function: Lymphocytes

Mediate specific immunity; B cells produce antibodies, T cells coordinate immune responses, and NK cells destroy abnormal host cells.

Leukocyte Function: Monocytes

Largest leukocytes; they exit the blood to become tissue macrophages, serving as aggressive, long-term phagocytes.

Leukocyte Function: Eosinophils

Reduce inflammation and allergic responses; they also release enzymes to destroy parasitic worms.

Leukocyte Function: Basophils

Migrate to injury sites to release histamine (vasodilator) and heparin (anticoagulant), intensifying the local inflammatory response.

Definition of Hematocrit

The volume percentage of red blood cells in a whole blood sample after centrifugation.

Normal Hematocrit Ranges

Adult Males: 40-54%; Adult Females: 37-47%.

Normal Erythrocyte Counts

Adult Males: 4.5-6.3 million/µL; Adult Females: 4.2-5.5 million/µL.

Normal Leukocyte and Platelet Counts

Total WBC: 5,000-10,000/µL; Platelets: 150,000-500,000/µL.

Definition of Hematopoiesis

The process of blood cell production occurring within the red bone marrow.

Significance of the Hemocytoblast

The multipotent hematopoietic stem cell from which all formed elements of the blood originate.

Process of Erythropoiesis

The transformation of a myeloid stem cell into a proerythroblast, then into a reticulocyte, and finally a mature erythrocyte.

Significance of the Reticulocyte

An immature erythrocyte that has ejected its nucleus but retains some RNA; its count in the blood indicates the rate of RBC production.

Regulation of Erythropoiesis (EPO)

Hypoxia stimulates the kidneys to release erythropoietin (EPO), which targets red bone marrow to accelerate erythrocyte maturation.

Basic Process of Leukopoiesis

The production of WBCs in red bone marrow, regulated by colony-stimulating factors (CSFs) and interleukins.

Basic Process of Thrombopoiesis

The hormone thrombopoietin (TPO) stimulates megakaryocytes to undergo cytoplasmic shedding, releasing platelets into the blood.

Hemostasis: Vascular Phase

Immediate vasoconstriction (vascular spasm) following injury; endothelial cells release chemicals and become sticky to slow blood loss.

Hemostasis: Platelet Adhesion

Platelets stick to exposed collagen fibers and von Willebrand factor at the site of blood vessel damage.

Hemostasis: Platelet Activation

Adhered platelets change shape and degranulate, releasing ADP, Thromboxane A2, and Calcium to recruit more platelets.

Hemostasis: Platelet Aggregation

Platelets stick to one another, forming a temporary, soft "platelet plug" to seal the vessel wall.

Coagulation: Extrinsic Pathway

A rapid pathway triggered by Tissue Factor (Factor III) released from damaged tissue outside the bloodstream.

Coagulation: Intrinsic Pathway

A slower pathway triggered by Factor XII when blood comes into contact with exposed collagen or foreign surfaces.

Coagulation: Common Pathway

Convergence point where Factor X is activated to form prothrombinase, converting prothrombin to thrombin, which then converts fibrinogen to fibrin.

Role of Vitamin K in Clotting

A fat-soluble cofactor required by the liver for the synthesis of clotting factors II (prothrombin), VII, IX, and X.

Fibrinolysis: tPA and Plasminogen

Tissue Plasminogen Activator (tPA) is released by damaged tissues to convert inactive plasminogen into the active enzyme plasmin.

Fibrinolysis: Role of Plasmin

An active enzyme that digests fibrin strands, effectively dissolving a blood clot after the vessel has healed.

Erythrocyte Surface Antigens

Genetically determined glycoproteins on the RBC membrane that define an individual's blood group (A, B, and Rh).

ABO Antigens and Antibodies: Type A

Possesses A-antigens on RBCs and anti-B antibodies in the plasma.

ABO Antigens and Antibodies: Type B

Possesses B-antigens on RBCs and anti-A antibodies in the plasma.

ABO Antigens and Antibodies: Type AB

Possesses both A and B antigens on RBCs and has no ABO antibodies in the plasma.

ABO Antigens and Antibodies: Type O

Possesses no ABO antigens on RBCs and has both anti-A and anti-B antibodies in the plasma.

Rh Blood Grouping

Defined by the presence (Rh positive) or absence (Rh negative) of the Rh (D) antigen on the erythrocyte surface.

Development of Anti-Rh Antibodies

Rh-negative individuals do not naturally possess these; they only develop after sensitization (exposure) via transfusion or pregnancy with an Rh+ fetus.

Transfusion Compatibility Logic

A recipient's antibodies must not match the donor's antigens; if they match, agglutination and hemolysis occur.

Location of the Fibrous Pericardium

The most superficial, tough layer of the pericardial sac, situated in the mediastinum.

Structure of the Fibrous Pericardium

Composed of dense irregular connective tissue that is inelastic and durable.

Function of the Fibrous Pericardium

Anchors the heart to the diaphragm and great vessels while preventing acute over-distension (over-filling) of the chambers.

Location of the Serous Pericardium

Deep to the fibrous pericardium; consists of a parietal layer lining the sac and a visceral layer on the heart surface.

Structure of the Serous Pericardium

A thin, slippery serous membrane that forms a double-layered closed sac.

Function of the Serous Pericardium

Produces serous fluid to reduce friction between the heart and the pericardial sac during contraction.

Pericardial Cavity and Serous Fluid

The potential space between the parietal and visceral layers containing fluid that acts as a lubricant for heart movement.

Atria vs. Ventricles: Functional Differences

Atria are thin-walled reservoirs that receive blood and pump it locally to ventricles; ventricles are high-pressure pumps that propel blood to the lungs or systemic body.

Phase 3 Contractile Action Potential: Ion Movements

Rapid K+ efflux (Repolarization). -96mV

Phase 1/2 Contractile Action Potential: Ion Movements

Ca2+ influx and slow K+ efflux (Plateau)

Phase 0 Contractile Action Potential: Ion Movements

Rapid Na+ influx (Depolarization) +52mV

Autorhythmic Action Potential: Ion Movements

Pacemaker Potential: Slow Na+ influx ; Depolarization: Ca2+ influx; Repolarization: K+ efflux.

Contrast: Initiation of Action Potential

Skeletal muscle requires neural stimulation; cardiac autorhythmic cells have spontaneous drift to threshold; cardiac contractile cells are triggered by gap junction ions.

Significance of the Plateau Phase

Prolongs the action potential and the absolute refractory period, preventing tetanic contractions and allowing time for ventricular filling.

Cardiac vs. Skeletal: Calcium Sources

Skeletal muscle uses internal SR calcium; cardiac muscle relies on both SR calcium and extracellular calcium influx to trigger contraction.

Cardiac vs. Skeletal: Contraction Duration

Cardiac contractions are significantly longer (approx. 250-300ms) than skeletal twitches to ensure efficient blood ejection.

Autonomic Innervation: Pacemaker vs. Contractile Cells

Sympathetic fibers innervate both (increasing HR and force); Parasympathetic fibers primarily innervate the SA/AV nodes to decrease HR.

Refractory Period of Cardiac Muscle

Extremely long (approx. 250ms), lasting almost as long as the entire muscle contraction to ensure a rhythmic, non-tetanic beat.

Calcium and Contractility

Higher intracellular Ca2+ levels increase the number of active cross-bridges between actin and myosin, directly increasing the force of myocardial contraction.

Path of Blood: Right Side

Deoxygenated blood enters the Right Atrium via Venae Cavae, crosses the Tricuspid Valve, and enters the Right Ventricle.

Path of Blood: To the Lungs

Right Ventricle pumps deoxygenated blood through the Pulmonary Semilunar Valve into the Pulmonary Trunk and Arteries.

Path of Blood: Left Side

Oxygenated blood returns from lungs via Pulmonary Veins to the Left Atrium, crosses the Bicuspid (Mitral) Valve, and enters the Left Ventricle.

Path of Blood: To the Systemic Circuit

Left Ventricle pumps oxygenated blood through the Aortic Semilunar Valve into the Aorta for distribution to the body.

Valve Oxygenation Status

Tricuspid/Pulmonary valves handle deoxygenated blood; Bicuspid/Aortic valves handle oxygenated blood.

Electrical Conduction Sequence

SA Node -> AV Node -> AV Bundle (Bundle of His) -> Right and Left Bundle Branches -> Purkinje Fibers.

Function of the SA Node

Known as the primary pacemaker; it reaches threshold fastest (80-100 bpm) and sets the sinus rhythm for the entire heart.

AV Node Delay

A 100ms pause in conduction that allows the atria to complete their contraction (atrial systole) before the ventricles begin to contract.

How Conduction Produces Coordinated Contraction

The delay at the AV node ensures atria empty first, and Purkinje fibers initiate ventricular contraction at the apex, pushing blood upward toward the valves.

ECG: P Wave

Represents atrial depolarization, which precedes the mechanical event of atrial contraction (systole).

ECG: QRS Complex

Represents ventricular depolarization; its magnitude masks the electrical signal of atrial repolarization.

ECG: T Wave

Represents ventricular repolarization, which precedes the mechanical event of ventricular relaxation (diastole).

Definitions: Systole vs. Diastole

Systole is the phase of chamber contraction and blood ejection; Diastole is the phase of chamber relaxation and blood filling.

Cardiac Cycle: Ventricular Filling

Occurs during mid-to-late diastole when atrial pressure exceeds ventricular pressure, opening the AV valves.

Cardiac Cycle: Isovolumetric Contraction

Early systole where all valves are closed; ventricular pressure rises rapidly while volume remains constant.

Cardiac Cycle: Ventricular Ejection

Phase of systole where ventricular pressure exceeds arterial pressure, forcing semilunar valves open to expel blood.

Cardiac Cycle: Isovolumetric Relaxation

Early diastole where all valves are closed; ventricular pressure drops rapidly while volume remains constant until it falls below atrial pressure.

Atrial Systole and Ventricular Filling

Atrial contraction provides the "atrial kick," contributing the final 20-30% of the End Diastolic Volume (EDV).

AV Valve Mechanics: Closing

Close when ventricular pressure exceeds atrial pressure at the start of systole; this closure produces the S1 ("Lubb") heart sound.

Semilunar Valve Mechanics: Closing

Close when arterial pressure exceeds ventricular pressure at the start of diastole; this closure produces the S2 ("Dupp") heart sound.

Systolic vs. Diastolic Blood Pressure

Systolic BP is the peak pressure in the aorta during ejection; Diastolic BP is the lowest pressure in the aorta during ventricular relaxation.

Left vs. Right Ventricle: Pressure and Volume

Both eject the same volume of blood (SV), but the left ventricle must generate significantly higher pressure to overcome systemic resistance.

Artery, Capillary, and Vein

Arteries carry blood away from the heart; capillaries are sites of exchange; veins return blood to the heart.

Tunica Interna Structure

Consists of an endothelium (simple squamous epithelium), a basement membrane, and an internal elastic lamina.

Tunica Interna Function

Provides a smooth, low-friction surface for blood flow and releases local chemicals that regulate vessel diameter.

Tunica Media Structure

Composed of circular layers of smooth muscle and elastic fibers.

Tunica Media Function

Regulates vessel diameter via vasoconstriction and vasodilation to control blood flow and systemic blood pressure.

Tunica Externa Structure

A connective tissue sheath containing collagen and elastic fibers.