BIO 169 Exam 2 Review: Blood, Heart, and Blood Vessels (Chapters 17-19)

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Blood: Structure, Function, and Properties

General Characteristics of Blood

Blood is a vital connective tissue with unique properties that support its role in the body.

Color: Bright red when oxygenated (arterial blood), dark red when deoxygenated (venous blood).
Viscosity: Thicker and more viscous than water due to cells and plasma proteins.
Volume: Average adult has 4-6 liters, depending on body size and sex.
pH: Slightly alkaline, typically maintained between 7.35 and 7.45.
Temperature: Slightly higher than body temperature, averaging about 38°C (100.4°F).
Composition: Consists of plasma (liquid portion) and formed elements (red blood cells, white blood cells, platelets).
Functions: Transports gases, nutrients, hormones, and waste; regulates pH, temperature, and fluid balance; protects against infection and blood loss.

Blood Typing

Blood typing determines the specific blood type based on antigens present on red blood cells.

Antigens: Inherited proteins on RBC surfaces; crucial for safe transfusions and organ transplants.
Main Blood Groups: ABO system (A, B, AB, O) and Rh system (positive or negative).
Importance: Receiving incompatible blood can trigger immune reactions and serious complications.
Procedure: Blood is mixed with antibodies; agglutination (clumping) indicates antigen presence.
Application: Essential for transfusions and understanding genetic inheritance.

Functions of Blood

Transport: Oxygen, carbon dioxide, nutrients, waste, hormones.
Regulation: Body temperature, pH (via buffers), fluid balance, osmotic pressure.
Protection: White blood cells defend against pathogens; platelets and clotting factors prevent blood loss; antibodies neutralize toxins.

Sickle-Cell Anemia: Causes of Sickling Episodes

Sickling occurs when RBCs change shape due to:

Low oxygen levels: Hemoglobin S polymerizes, causing cells to sickle.
Dehydration: Increases hemoglobin S concentration, promoting sickling.
Infection: Triggers inflammation and stress, leading to sickling.
Acidosis: Lowered blood pH encourages sickling.

Red Blood Cell Structure and Oxygen Transport

Anucleate: RBCs lack a nucleus, maximizing space for hemoglobin.
No mitochondria: Prevents oxygen consumption by the cell itself.
Hemoglobin: Each molecule can carry four O2 molecules.

Blood Plasma Composition

Water: 90-92% of plasma; acts as solvent and regulates temperature.
Plasma Proteins: 7-8%; includes albumin (osmotic pressure, transport), globulins (antibodies, transport), fibrinogen (clotting).
Solutes: <1%; electrolytes (Na+, K+, Ca2+, Cl-, HCO3-), nutrients, waste products, hormones, gases.

Regulation of RBC Production

Kidneys: Detect low oxygen and release erythropoietin, stimulating RBC production in bone marrow.

Heart: Structure, Function, and Circulation

Myocardial Cells: Function and Properties

Myocardial cells are specialized for heart contraction and electrical activity.

Contraction: Rhythmic contraction pumps blood.
Electrical Conductivity: Generate and conduct impulses for synchronized heartbeat.
Automaticity: Some cells (e.g., SA node) spontaneously depolarize to initiate heartbeat.
Force Generation: Actin and myosin interact to eject blood.
Adaptation: Can hypertrophy to meet increased workload.

Tracing Blood Flow Through the Heart

Blood enters right atrium via superior/inferior vena cava (low O2).
Right atrium contracts, blood moves through tricuspid valve to right ventricle.
Right ventricle contracts, blood moves through pulmonary semilunar valve to pulmonary artery.
Blood travels to lungs for oxygenation.
Oxygenated blood returns via pulmonary veins to left atrium.
Left atrium contracts, blood moves through mitral (bicuspid) valve to left ventricle.
Left ventricle contracts, blood moves through aortic semilunar valve to aorta.
Blood is distributed to the body.

Systemic and Pulmonary Circulation

Pulmonary Circulation: Heart → lungs → heart; gas exchange (O2 uptake, CO2 release).
Systemic Circulation: Heart → body → heart; nutrient/waste exchange.
Key Difference: Pulmonary = gas exchange; Systemic = nutrient/waste exchange.

Cardiac Conduction System: Parts and Action Potential Pathway

Sinoatrial (SA) Node: Primary pacemaker, initiates action potential.
Atrial Conducting Fibers: Transmit impulse across atria.
Atrioventricular (AV) Node: Delays impulse (~0.1 sec).
AV Bundle (Bundle of His): Carries impulse into interventricular septum.
Right and Left Bundle Branches: Carry impulse toward heart apex.
Purkinje Fibers: Distribute impulse to ventricular muscle cells.

Order: SA node → Atrial conducting fibers → AV node → AV Bundle → Bundle branches → Purkinje fibers

Cardiac Cycle: Three Steps

Atrial Systole: Atria contract, blood moves to ventricles.
Ventricular Systole: Ventricles contract, AV valves close, semilunar valves open, blood ejected.
Relaxation Period (Diastole): Chambers relax, blood flows passively into atria and ventricles.

Heart Valves: Opening and Closing During Cardiac Cycle

Phase	AV Valves	Semilunar Valves
Ventricular Filling (Diastole)	Open	Closed
Isovolumetric Contraction (Start of Systole)	Closed	Closed
Ventricular Ejection (Systole)	Closed	Open
Isovolumetric Relaxation (Start of Diastole)	Closed	Closed

Angina Pectoris vs. Myocardial Infarction

Angina Pectoris: Temporary, reversible chest pain due to reduced blood flow.
Myocardial Infarction: Prolonged blockage, irreversible heart muscle damage.

Left Ventricular Wall Thickness

Reason: Must generate higher pressure to pump blood throughout the body.

Norepinephrine Effect on Heart

Effect: Increases heart rate (positive chronotropic effect).

Factors Affecting Heart Rate

Autonomic Nervous System: Sympathetic increases, parasympathetic decreases heart rate.
Hormones: Epinephrine, thyroid hormones increase heart rate.
Physical Activity: Exercise raises heart rate.
Body Temperature: Higher temperature increases heart rate.
Age: Infants/children have higher rates than adults.
Emotions: Stress, anxiety, excitement elevate heart rate.
Medications: Beta-blockers decrease, stimulants increase heart rate.
Health Conditions: Hyperthyroidism, heart disease, dehydration affect heart rate.

Factors Aiding Venous Return

Venous Valves: Prevent backflow, ensure one-way movement.
Muscle Pump: Skeletal muscle contractions push blood upward.
Respiratory Pump: Breathing changes thoracic/abdominal pressure, aiding return.
Large Lumen Size: Veins store and transport more blood.
Low Resistance: Thin walls, less resistance for blood flow.

Heart Block: Types and Effects

First-degree: Signals slowed, still reach ventricles; mild, often asymptomatic.
Second-degree: Some signals do not reach ventricles; dropped beats (Mobitz I & II).
Third-degree: No signals reach ventricles; atria and ventricles beat independently; life-threatening, often requires pacemaker.
Causes: Aging, heart disease, medications, conduction system damage.
Symptoms: Dizziness, fatigue, fainting, slow heart rate.

Normal Heart Sounds

Cause: Closing of heart valves creates sounds ("lub-dub") heard with stethoscope.

Foramen Ovale

Definition: Opening in fetal heart's interatrial septum; allows blood to bypass lungs before birth.

Blood Vessels: Types, Structure, and Function

Types of Capillaries

Type	Structure	Function
Continuous	Uninterrupted lining	Exchange of fluids/small molecules; restricts large proteins/cells (most common)
Fenestrated	Has pores (fenestrations)	Greater exchange; ideal for filtration, absorption, secretion
Sinusoid	Large gaps	Allows passage of large molecules/cells; rapid exchange

Function of Arteries, Capillaries, and Veins

Arteries: Carry blood away from heart to tissues.
Capillaries: Site of exchange between blood and tissues.
Veins: Carry blood back toward heart.

Baroreceptors

Function: Sense changes in blood pressure by detecting vessel wall stretch.

Main Factors Influencing Blood Pressure

Cardiac Output
Peripheral Resistance
Blood Volume

Source of Blood Flow Resistance

Most Significant: Diameter of blood vessels.

Peripheral Resistance

Definition: Opposition to blood flow offered by vessels, mainly small arteries/arterioles.
Factors: Vessel diameter, blood viscosity, vessel length.

Arterioles as Resistance Vessels

Role: Primary site for regulation of blood flow resistance.

Bulk Flow in Capillaries and Regulating Pressures

Bulk Flow: Movement of large amounts of fluid/solutes across capillary wall.
Regulating Pressures: Hydrostatic, osmotic, interstitial fluid hydrostatic, interstitial fluid osmotic.

Hormonal Effects on Blood Pressure

Hormone	Effect
Antidiuretic hormone	Raises blood volume and pressure
Aldosterone	Increases blood volume and pressure
Renin-Angiotensin-Aldosterone System (RAAS)	Increases peripheral resistance and pressure
Epinephrine/Norepinephrine	Vasoconstriction, increased heart rate
Atrial Natriuretic Peptide	Lowers blood volume and pressure

Types of Arteries and Anatomical Characteristics

Type	Structure	Function
Elastic	Largest, high elastic fibers in tunica media	Stretch/recoil to maintain pressure
Muscular	Medium, more smooth muscle, less elastic	Distribute blood to organs/tissues; constrict/dilate
Arterioles	Smallest, thin tunica media	Regulate blood flow/pressure by diameter

Blood Flow Through Skin

Uniqueness: Highly adjustable; major role in thermoregulation via specialized vessels and rapid flow changes.

Pulse Pressure

Definition: Difference between systolic and diastolic blood pressure; represents force generated each contraction.
Formula:

Tissue Perfusion

Definition: Delivery of blood to capillary beds in tissues; ensures oxygen/nutrient supply and waste removal.
Factors: Blood pressure, vascular resistance, cardiac output, blood volume, local chemical signals, autonomic nervous system.

Additional info: Academic context and expanded explanations were added to clarify brief points and ensure completeness for exam preparation.