Heart Anatomy and Function

Heart Overview

• Serves as a double-sided pump
• Generates blood pressure and properly routes blood
• Separates pulmonary and systemic circulation
• Ensures unidirectional blood flow via valves
• Regulates blood supply by adjusting heart rate and contraction force
• Right side of the heart pumps blood to the lungs through pulmonary circulation
• Left side pumps blood to the body tissues through systemic circulation
• Size is about that of a closed fist
• Located in mediastinum of the thoracic cavity
• Two-thirds of the heart mass lies left of the sternal midline
• Apex points downward and to the left
• Base is the superior portion

Heart walls and Coverings

• Pericardium consists of Fibrous and Serous Pericardium

• Fibrous Pericardium:

  • Tough, outer layer that prevents overdistension

• Serous Pericardium:

  • Inner layer, divided into Parietal and Visceral Pericardium
  • Parietal Pericardium lines the Fibrous Layer
  • Visceral Pericardium (epicardium) covers the heart surface
  • Pericardial Cavity is located between layers and contains fluid

• Heart Wall Layers consist of Epicardium, Myocardium, and Endocardium

  • Epicardium: smooth, outer surface
  • Myocardium: the middle layer made of cardiac muscle, and responsible for contractility
  • Endocardium: inner lining with features like pectinate muscle in the auricles and trabeculae carneae in the ventricles.

Coronary Circulation

• Arteries

  • Left Coronary Artery branches:
    • Anterior interventricular artery
    • Left Marginal Artery
    • Circumflex Artery
  • Right coronary artery includes
    • Right Marginal Artery
    • Posterior Interventricular artery
  • Blood flow is discontinuous, compressed during contractions

• Veins

  • Great Cardiac Vein drains the left side
  • Small cardiac vein drains the right side
  • Coronary sinus collects venous blood and empties into the right atrium.

Chambers and Blood Flow

• Chambers

  • Right atrium receives deoxygenated blood from:
    • Superior vena cava
    • Inferior vena cava
    • Coronary sinus
  • Left atrium receives oxygenated blood from pulmonary veins
  • Right Ventricle connects to the pulmonary trunk
  • Left Ventricle connects to the aorta
  • Interventricular septum separates ventricles

• Valves

  • Atrioventricular (AV) valves:
    • Tricuspid valve (right side, 3 cusps)
    • Bicuspid/Mitral valve (left side, 2 cusps)
    • Connected to papillary muscles by chordae tendineae
  • Semilunar Valves:
    • Pulmonary valve (right side)
    • Aortic Valve (left side)
    • Close when cusps fill with blood

Blood Flow Sequence

• Deoxygenated blood enters right atrium
• Blood passes through the tricuspid valve to the right ventricle
• Blood is pumped through the pulmonary valve to lungs
• Oxygenated blood returns to the left atrium
• Blood moves through the mitral valve to the left ventricle
• Blood is ejected through the aortic valve to systemic circulation

Special features of the Heart

• Fossa Ovalis: remnant of fetal foramen ovale
• Anastomosis: direct connections between arteries
• Cardiac muscles rely almost entirely on aerobic respiration
• Has a longer refractory period than skeletal muscle
• Self-excitable pacemaker cells control rhythm

Anatomical Features of the Heart Skeleton

• The heart skeleton consists of fibrous connective tissue between atria and ventricles
• Provides electrical insulation and muscle attachment points
• Cardiac muscle cells are elongated and branched with 1-2 nuclei
• Cardiac muscle cells contain striations and actin/myosin myofilaments
• Cardiac muscle cells are rich in mitochondria for aerobic respiration
• Cardiac muscle cells have an extensive capillary network

Sarcoplasmic Reticulum and Calcium

• Stores calcium but has a less regular arrangement than skeletal muscle
• Larger transverse tubules near the Z disc
• Calcium must diffuse a longer distance from SR to actin/myosin
• Some calcium comes from ECF (extracellular fluid) and T Tubules

Intercalated Disks

• Specialized cell-to-cell contacts with interdigitation
• Contains desmosomes for cell adhesion
• Gap junctions allow action potential propagation
• Forms functional syncytium
• Cardiac muscle behaves as a single electrical unit

Conduction Systems

• Nodes and pathways

  • Sinoatrial Node (SA)
    • Primary pacemaker
  • Atrioventricular Node (AV)
    • Conducts signals more slowly
  • AV bundle branches extend to ventricles
  • Purkinje fibers conduct APs to ventricular muscle

• Conduction Sequence

  • Chambers are at rest
  • SA node generates action potential
  • Signal spreads through atrial walls
  • Conduction through AV node (0.04s delay)
  • Signals travel through bundle branches and Purkinje fibers
  • Ventricles contract from apex to base

Electrical Properties

• Action potentials

  • Pacemaker cells generate spontaneous action potentials
  • Depolarization involves sodium and calcium influx
  • Plateau phase maintains contraction
  • Repolarization involves potassium efflux
  • Long refractory period prevents tetanic contractions

• ECG components

  • P wave: atrial depolarization
  • QRS complex: ventricular depolarization
  • T wave: ventricular repolarization
  • PQ interval: 0.16s (atrial contraction/relaxation)
  • QT interval: 0.36s (ventricular contraction/relaxation)

Cardiac Arrhythmias

• Major Types

  • Tachycardia: HR > 100 bpm

  • Bradycardia: HR < 60 bpm

  • Atrial flutter/fibrillation

  • Ventricular fibrillation

  • AV node blocks

    • First, second, or third degree

  • Premature contractions

    • Atrial
    • Ventricular

• Common causes

  • Excessive sympathetic stimulation

  • Ischemia or inflammation

  • Elevated body temperature

  • Lifestyle Factors

    • Caffeine
    • Smoking
    • Lack of sleep

  • Cardiac Tissue damage

Comparison with skeletal muscle

• Cardiac muscle conducts action potentials cell to cell
• Slower propagation due to gap junctions
• Has plateau phase in action potential
• Uses both internal and external calcium sources
• Longer refractory period

Phases of the Cardiac Cycle

• Initial Relaxation and Passive Ventricular Filling

  • All chambers are initially relaxed (diastole)
  • Blood moves into chambers due to higher pressure than heart chamber pressure
  • Blood flows from atria to ventricles through open AV (atrioventricular) valves
  • Accounts for approx. 70% of ventricular filling

• Atrial Systole (Active Ventricular Filling)

  • SA (Sinoatrial) node generates AP; P wave on ECG
  • Atrial contraction actively forces additional blood into ventricles
  • Not essential at rest but crucial during exercise
  • During exercise, heart pumps 300-400% more blood than at rest

• Ventricular Systole - Isovolumetric Contraction

  • Follows QRS complex on ECG
  • Ventricular pressure increases
  • AV (atrioventricular) valves and SL (semilunar) valves are closed
  • EDV (End Diastolic Volume) is 120-130 mL
  • No volume change occurs during this period

• Ventricular Systole- Ejection Period

  • Ventricular Pressure exceeds pulmonary trunk/aorta pressure
  • SL valves open
  • Left Ventricle reaches 120 mmHg
  • Right ventricle reaches 25 mmHg
  • ESV (end-systolic volume) is 50-60 mL

• Ventricular Diastole- Isovolumetric Relaxation

  • Begins with T wave (ventricular repolarization)
  • Ventricular pressure drops rapidly
  • Backflow from arteries causes SL valve closure
  • All valves are closed during this phase

Important structural and Functional Elements

• SA Node initiates electrical activity
• AV node and Purkinje fibers conduct electrical signals
• Four types of valves:
  • AV valves
  • Mitral
  • Pulmonary
  • Tricuspid

ECG Correlation

• P wave: Atrial Depolarization
• QRS Complex: Ventricular Depolarization
• T wave: Ventricular Repolarization

Pressure and Volume Dynamics

• Blood Movement depends on pressure gradients
• Valve operation is pressure-dependent
• Ventricular filling occurs both passively and actively
• Different pressure levels in left and right ventricles
  • Left ventricle = 120 mmHg
  • Right Ventricle= 25 mmHg
• Volume changes from EDV to ESV during cycle
  • EDV: 120-130 mL
  • ESV; 50-60 mL

Heart Sounds

• Standard Heart Sounds

  • First heart sound (lub): AV valves close at the start of ventricular systole
  • Second Heart Sound (dup): closure of aortic and pulmonary SL valves at the start of ventricular diastole.
  • Third Heart sound: turbulent blood flow into ventricles near the end of the first third of diastole

• Abnormal Heart Sounds: Murmur

  • Results from:
    • Incompetent valves that has Valvular insufficiency
    • Valve stenosis: creates turbulent blood flow through narrowed openings
    • Dicrotic notch: a slight pressure increase in the aorta as the aortic SL valve closes

Blood Pressure and Cardiac Output

• Mean Atrial Pressure (MAP)
  • Calculated as: MAP=CO x PR
  • Cardiac Output (CO)= Stroke Volume (SV) x Heart Rate (HR)
• Stroke volume (SV)= EDV-ESV
• Typically 70 ml/beat = 120mL-50mL
• Normal Resting CO: 5250 mL/min (70 mL/beat x 75 beats/min)

Heart Regulation

• Intrinsic Regulation:

  • Preload:
    • Ventricular wall stretch affects contraction force
  • Frank Starling's law: greater stretch equals greater contraction and SV
  • Afterload:
    • Pressure ventricles must overcome to ensure blood pushes into the aorta

• Extrinsic Regulation:

  • Neural Control

    • Parasympathetic: decreases heart rate and uses acetylcholine
    • Sympathetic: increases heart rate and contraction force alongside using epinephrine and norepinephrine

  • Hormonal Control

    • Epinephrine and norepinephrine from adrenal medulla

    • Responds to physical activity, emotional excitement, and stress

    • Slower but longer-lasting than neural control

Homeostatic Mechanisms

• Baroreceptor Reflex
  • Monitors blood pressure in internal carotids and aorta
  • Sends information to cardioregulatory center in medulla oblongata
• Chemoreceptor reflex
  • Monitors pH, CO2, and O2 levels
  • Located in aorta and internal carotids
  • Low O2 levels trigger increased heart rate to improve tissue oxygenation

Effects of Ion Concentration and Temperature

• Increased K+: Decreases HR ,which can cause fibrillation
• Decreased K+: Causes hyperpolarization and decreased HR
• Increased Ca2+: Strengthens contractions but reduces HR
• Decreased Ca2+: increases HR
• Temperature changes directly affect HR

Age-related changes

• Left-ventricle hypertrophy
• Increased aortic pressure
• Decreased max. HR
• Reduced hormone effectiveness
• Less flexible valves
• Increased risk of arrhythmias
• Higher likelihood of heart disease

Common Heart Conditions

• Endocarditis: Inflammation of endocardium
• Pericarditis: Inflammation of pericardium
• Cardiomyopathy: Weakening of heart muscle
• Coronary Heart Disease: Reduced coronary blood flow.
• Congestive heart failure: Can affect either side of heart;
  • Left side causes pulmonary congestion
  • Right side results in peripheral edema.

Primary functions of the Circulatory System

• Blood transport too and from body tissues
• Exchange of nutrients, waste products, and gases
• Transportation of hormones, immune components, coagulation factors, enzymes
• Blood pressure regulation
• Control of blood flow to specific tissues

Blood Vessel Structure

• Three Main Layers
• Tunica Intima (internal)
  • Contains endothelium
  • Basement membrane
  • Connective tissue layer
  • Internal elastic membrane
• Tunica Media
  • Circular smooth muscle cells
  • Elastic and collagen fibers
  • Controls vasoconstriction and vasodilation
• Tunica Externa
  • Connective tissue layer
  • Transitions from dense to loose structure

Types of Blood Vessels

• Arteries- carry blood away from the heart, decreasing in size with distance
• Elastic Arteries
  • Largest diameter (10mm)
  • High pressure tolerance
  • More elastic tissue than smooth muscle
  • Thick tunica intima
• Muscular Arteries (40-300µm)
  • 25-40 smooth muscle layers
  • Regulate regional blood supply
  • Adapted for vasodilation and vasoconstriction
• Arterioles (9-40µm)
  • Smallest arteries with three tunics
  • Connect to capillaries
  • Strong vasomotor control

Capillaries (7-9 µm)

• Types
  • Continuous
    • Most Common type
    • No gaps between endothelial cells
    • Found in muscle and nervous tissue
    • Less permeable to large molecules
  • Fenestrated
    • Contains numerous pores
    • Present in interstitial villi, kidney glomeruli
    • Highly permeable
  • Sinusoidal
    • Large diameter with extensive fenestration
    • Found in endocrine glands and liver
    • Minimal basement membrane

Veins

• transport blood toward the heart, increasing in size as they approach it
• Venules (up to 50 µm)
  • Drain capillary networks
  • Few smooth muscle cells
  • Connect to small veins
• Small and Medium Veins
  • Continuous smooth muscle layer
  • Collagenous connective tissue
  • Medium veins (1mm-1cm)
• Large Veins
  • Thin tunica intima
  • Circular smooth muscle arrangement
  • Prominent tunica extreme

Special Vascular Features

• Portal Veins
  • Three systems in humans:
    • Hepatic portal veins (digestive system to the liver)
    • Hypothalamo Hypophyseal portal system
    • Renal nephron portal system
• Vascular control Mechanisms
  • Vasoconstriction and Vasodilation
  • Precapillary sphincters
  • Arteriovenous anastomoses for thermoregulation
  • Neutral Innervation (sympathetic and parasympathetic)

Common Venous Disorders

• Varicose veins
  • Valve incompetence (regurgitation)
  • Increased venous pressure
  • Common in lower limbs
• Phlebitis
  • Vein inflammation
  • Can lead to blood stagnation
• Gangrene
  • Tissue death from blood loss
  • Can result from severe phlebitis

Supporting Structures

• Vaso Vasorum
• Nutrient vessel for large blood vessels
• Valves in veins larger than 2mm
• Neural plexuses for vessel control
• Baroreceptors for pressure monitoring

Laminar vs Turbulent flow

• Laminar flow occurs in smooth, equal-diameter vessels
  • Blood flows in concentric rings
  • Outermost layer flows slowest
  • Center flows fastest
• Turbulent flow occurs when
  • Flow rate exceeds velocity
  • Blood passes constrictions or sharp turns
  • Associated with heart sounds
  • Abnormal in arteries suggests constriction
  • Increases thrombosis risk

Blood Pressure Measurement

• Force exerted by blood against vessel walls
• Measurement methods:
  • Direct: uses cannula in blood vessel
  • Indirect: auscultatory method using sphygmomanometer and stethoscope
• Korotkoff sounds indicate
  • Systolic pressure: 1st sound heard
  • Diastolic pressure: when sound disappears
• Blood pressure classifications
  • Normal: <120/<80 mmHg
  • Elevated: 120-129/<80 mmHg
  • Stage 1 hypertension: 130-139/80-89 mmHg
  • Stage 2 hypertension: ≥140/≥90 mmHg
  • Hypertensive Crisis: >180/>120 mmHg

Blood flow Dynamics

• Flow= Cardiac Output
• Flow equation: F=ΔP/R (where P is pressure, R is resistance)
• Flow is:
  • Directly proportional to pressure difference
  • Inversely proportional to resistance

Resistance affected by:

• Viscosity

• Vessel diameter

• Vessel length (less critical)

• Poiseullie's Law: flow decreases when resistance increases

Vessel Characteristics

• Viscosity: Directly proportional to resistance, Increases with higher hematocrit
• Affects heart workload
• Critical closing pressure, point where vessel collapses (minimum force to keep vessel open)
• Important in circulatory shock
• Laplace's law: Force on vessel wall= Diameter x Pressure
  • Larger Diameter increases wall force
  • Weak walls can form aneurysms

Blood distribution and vessel properties

• Blood Volume distribution
• Systemic vessels: 84%
  • Veins: 64% (39% L 25% S)
  • Arteries: 15% (8%L 5% S 2% arterioles)
  • Capillaries: 5%
  • Pulmonary Vessels: 9%
  • Heart: 7%
• Vascular Compliance
  • Stretch more equals greater compliance
  • Venous system has 24x greater compliance than arteries
  • Acts as a blood reservoir
• Pressure characteristics
  • Highest in aorta (100 mmHg)
  • Greatest drop occurs in arterioles
  • Stabilizes in capillaries and veins
  • Reaches 0 mmHg at right atrium

During Exercise

• Heart Beats with greater force
• Aortic pressure increases
• Skeletal muscle capillaries dilate
• Flow can increase from 5L/min to 25L/min in aorta

Capillary Exchange

• Mechanism of exchange

  • Diffusion is the most important means of exchange in capillaries
  • Blood pressure at the capillary network:
    • Arterial end: approx. 30 mm Hg
    • Venous end: approx. 10 mm Hg Substances that cross capillary walls

• Lipid-soluble substances

  • Cross capillary walls easily through diffusion
    • Respiratory gases (O2,CO2)
    • Steroid hormones
    • Fatty acids

• Water-soluble substances

  • Use fenestrations and intercellular spaces

    • Glucose
    • Amino acids
    • Water-soluble hormones

Factors affecting fluid movement

• Three main factors influence movement into or out of capillaries: blood pressure, capillary permeability, osmosis
• Fluid Movement Pattern
  • At the arterial end:
    • Net filtration pressure is positive
    • Blood pressure is greater than osmotic pressure
    • Fluid moves out of capillaries into interstitial spaces
    • Oxygen, glucose, and hormones move out to tissues
  • At the venous end:
    • Osmotic pressure is greater than blood pressure
    • Fluid moves INTO capillaries from interstitial spaces
    • About 90% of fluid returns to the capillaries
    • The remaining 10% is collected in the lymphatic system

Venous Return

• Importance of venous return:
  • Muscular pump: contraction of skeletal muscles compresses veins
    • Creates pressure differential to move blood
    • Valves prevent backflow when muscles relax
    • Especially important in lower limbs to fight gravity
  • Respiratory Pump
    • Breathing creates pressure changes
    • Thoracic cavity expansion decreases pressure in thoracic veins
    • Simultaneously compresses abdominal veins
    • Creates pressure differential to move blood toward the heart
  • Sympathetic vasoconstriction (venous tone)
    • Sympathetic nervous systems stimulates smooth muscles in veins
    • Regular contractions create pressure differentials
    • Helps push blood backward toward the heart
  • Effects of Gravity
    • Hydrostatic pressure increases blood pressure below the heart and decreases it above the heart
    • 15-20% of total blood volume passes through capillaries of lower limbs during 15 minutes of standing still
    • Can lead to edema if venous return is impaired
    • Muscular movement improves venous return by fighting gravity

Control of Blood Flow and Blood Pressure

• Control of Blood flow in tissues

  • Local control: flow is proportional to metabolic needs
  • Nervous system: routes blood flow and maintains blood pressure
  • Hormonal control: sympathetic action potentials stimulate epinephrine and norepinephrine

• Mean Arterial Pressure (MAP)

  • Slightly less than the average of systolic and diastolic pressures Changes throughout lifetime:
  • Approx 70 mm Hg at birth
  • 100 mm Hg from adolescence to middle age
  • 110 mm Hg in healthy older individual MAP= CO x PR MAP= HR x SV x PR

Short-term regulation of Blood pressure

• Baroreceptor reflexes: changes in BP lead to changes in peripheral resistance (PR), HR, and SV
  • Adrenal medullary mechanism: results from increased sympathetic stimulation during decreased blood pressure, exercise, and stress
• Chemoreceptor reflexes sensitive to oxygen, Co2, and pH levels of blood
• Central nervous system ischemic response: activated when blood flow to medulla oblongata is insufficient

Long-term regulation of Blood pressure

• Direct regulation by kidneys

  • Kidneys regulate BP by altering blood volume through urine production Increased BV and Map lead to increased urine volume
  • Decreased BV and BP leads to decreased urine production Renin-Angiotensin-aldosterone mechanism Renin is released when BP decreases Leads to the production of angiotensin II which causes vasoconstriction

• Antidiuretic hormone (Vasopressin) Mechanism:

  • Released in response to decreased BV or increased plasma osmolarity
  • Increases water reabsorption in the kidneys
  • Atrial natriuretic mechanism:

• ANH released from atria when venous return increases

• Increases urine production and sodium loss

  • • Fluid shift mechanism
  • Stress Relaxation Response
  • Vasomotor adjustment of blood vessels in response to changes in blood volume
  • When BV suddenly decreases, smooth muscles contract
  • Most effective when blood pressure changes occur over many minutes

Functions of the Lymphatic System

• Fluid balance
  • Maintains fluid balance by collecting excess interstitial fluid about 30 liters of fluid moves out of blood capillaries into interstitial spaces but only 27 liters return directly to venous circulation
  • The remaining 3 liters become lymph, which is collected by the lymphatic system and eventually returned to the bloodstream
• Lipid absorption: plays a crucial role in absorbing fats and fat-soluble substances from the digestive tract
  • Specialised structures called lacteals in the intestinal villi which contain absorbed lipids called chyle Defense: provides defense by detecting/responding to pathogens, toxins, and cancerous cells

Anatomy of the lymphatic system

• Lymphatic vessels: carry lymph away from tissues towards veins Lymphatic capillaries: permeable than blood capillaries; lack a basement membrane with 1 way valve. Lymph is excluded in the CNS (though some are found in the meninges), bone marrow, and avascular tissues (cartilage, cornea, epidermis).
• Lymphatic vessels: valves ensure one-way flow-contain smooth muscle with pacemaker cells that contract rhythmically to move lymph Unlike the cardiovascular system, the lymphatic system has no central pump. Lymph movement relies on:
• Contraction of lymph vessels: unidirectional valves divide vessels into chambers that act as individual pumps
• Muscular pump: contraction of surrounding skeletal muscle compresses lymphatic vessels

Lymphatic Tissues and Organs

• Primary Lymphatic Organs

• Red Bone Marrow: produces B-cells that become immunocompetent Thymus: produces T-cells that become immunocompetent, located in the superior mediastinum anterior to the heart. Increases in size after birth, remains the same until 60, when it begins to atrophy.

• Secondary lymphatic organs and tissues

• Structures where lymphocytes interact, can produce response.

• Lymph nodes: act as a filter, shape (1-25mm long).

• More afferent vessels (bringing lymph in) than efferent vessels (taking lymph out).

• Organized around cortex and medulla with a dense connective tissue capsule.

• Cancer cells can spread to lymph nodes.

• Mucosa-associated lymphatic tissue (MALT): tissue associated with mucous membranes lining digestive, respiratory, urinary, and reproductive tracts Diffuse lymphatic tissue: macrophages that blend in with other tissues-Lymphatic nodules: Loose connected tissue-Peyer's patches:

• Tonsils: groups of lymphatic nodules in the nasopharynx and oral cavity

• Spleen: located in left superior side of abdomen, fibrous area filled with macrophages and enlarged capillaries to detect and respond to foreign substances.

• Destroys old blood cells, limited blood reservoir, stores/releases platelets

Surveillance: Me vs Not me

• The immune system determines what belongs in the body “me”, and what doesn't. Cells have markers (glycoproteins, glycolipids) that help cells/communicate. When immune cells encounter:
• The self no reaction occurs unless with a problem like cancer
• Self-markers activate immune responses to the destruction of the foreign objects.

Types of Immunity

• Innate immunity (non-specific)
  • First line of defense: physical barriers
  • Second line of defense: internal defenses
  • Responds immediately to threats - Does not discriminate
  • No memory of previous exposures
• Adaptive Immunity (specific) Third line of defense
  • Discriminate between specific threats
  • Takes longer to mobilize (up to weeks)
  • Provides immunological memory
  • Involves antibody-mediated and cell-mediated responses

Physical Barriers

• 1st line of defense
  • Physical structure prevents entry by being low pH(3-5) creates a inhospitable environment for bacteria
• Mucous membranes
  • Line openings to the outside world, and traps foreign particles.
• Specialized barriers Stomach: low pH (1-2) from hydrochloric acid,urine,eyes: (enzyme that causes cell lysis,cilia and mucus trap and sweep particles toward digestive tract

Chemical Mediators:

• Lysozymes: cause cell lysis especially in bacteria
• Histamines and kinins: promote vasodilation,increase permeability
• Interferons: protect against viral infections, destroy microbes
• Cytokines: proteins stimulate responses

Component System

• Approx 20 proteins circulating in blood, activated complement cascade in two ways:C3 binds with foreign substances and attacks macrophages or binding of antibodies to antigens

• Activated complement functions

  • Forms cell lysis by complement proteins on bacterial surfaces to stimulate phagocytosis

• Immune cells to infection site

  • (chemotaxis)

Interferons

• Proteins protects viral infection and cancers, bind to cell surfaces, viral replication in those cells Inflammatory response
• Results for injury
• Initiated by produced
  • Vasodilation (increased blood flow to the area attraction of immune cells -.Allows enter tissue, convert, local inflammation
  • Confined to a specific area

Systemic Inflammation

• Increased neutrophil with increased vascular permeability
• The lymphatic system removes fluid from tissues
• Innate Immunity that directs movements towards signals.

Cellular Components

• Cell Phagocytosis that certain engulf and destroy pathogens.
• Types of white blood cells First enter to an infected cell. Short lifespan (few hours
• Microphages that enter larger cells. First enter promotes inflammation and are non-motile