Study Guide: Heart, Vessels, Hemodynamics, Blood, and Lymphatic System

Heart, Vessels, and Hemodynamics

Structure and Function of the Heart

The heart is a muscular organ responsible for pumping blood throughout the body via the circulatory system. Understanding its anatomy and physiology is essential for comprehending cardiovascular function.

• Chambers and Valves: The heart consists of four chambers (two atria and two ventricles) and four main valves (tricuspid, pulmonary, mitral, and aortic) that ensure unidirectional blood flow.

• Major Vessels: Key vessels include the aorta, vena cavae, pulmonary arteries, and pulmonary veins.

• Coronary Circulation: Supplies blood to the heart muscle itself via coronary arteries and veins.

Cardiac Muscle and Action Potentials

Cardiac muscle cells (cardiomyocytes) are specialized for rhythmic contraction and electrical conduction.

• Action Potential: The cardiac action potential involves rapid depolarization, plateau, and repolarization phases, allowing coordinated contraction.

• Conduction System: Includes the sinoatrial (SA) node, atrioventricular (AV) node, bundle of His, bundle branches, and Purkinje fibers.

• Mechanical Junctions: Intercalated discs contain gap junctions and desmosomes for electrical and mechanical connectivity.

Cardiac Cycle and ECG

The cardiac cycle describes the sequence of events in one heartbeat, including systole (contraction) and diastole (relaxation).

• Electrocardiogram (ECG): A recording of the heart's electrical activity. Key waves include P (atrial depolarization), QRS (ventricular depolarization), and T (ventricular repolarization).

Blood Vessels and Circulation

Blood vessels form a closed system of tubes that transport blood throughout the body.

• Arteries: Carry blood away from the heart; have thick, muscular walls.

• Veins: Return blood to the heart; have thinner walls and valves to prevent backflow.

• Capillaries: Microscopic vessels where exchange of gases, nutrients, and wastes occurs.

• Types of Capillaries: Continuous, fenestrated, and sinusoidal, each with different permeability characteristics.

Hemodynamics

Hemodynamics refers to the principles governing blood flow in the circulatory system.

• Blood Pressure: The force exerted by blood on vessel walls; measured in mmHg.

• Blood Flow: The volume of blood moving through a vessel per unit time.

• Resistance: Opposition to blood flow, mainly due to vessel diameter, blood viscosity, and vessel length.

• Key Equation:

$\text{Blood Flow} = \frac{\text{Pressure Difference}}{\text{Resistance}}$

Regulation of Blood Pressure and Flow

• Neural Regulation: The autonomic nervous system (ANS) regulates heart rate and vessel diameter via sympathetic and parasympathetic pathways.

• Hormonal Regulation: Hormones such as epinephrine, norepinephrine, and antidiuretic hormone (ADH) influence blood pressure.

Blood and Lymphatic System

Composition and Functions of Blood

Blood is a connective tissue with multiple functions, including transport, regulation, and protection.

• Components: Plasma (liquid matrix), red blood cells (RBCs), white blood cells (WBCs), and platelets.

• Plasma: Contains water, proteins (albumin, globulins, fibrinogen), nutrients, hormones, and waste products.

• Serum: Plasma without clotting factors.

• Hematocrit: The percentage of blood volume occupied by RBCs.

Formed Elements of Blood

• Red Blood Cells (Erythrocytes): Biconcave cells specialized for oxygen transport via hemoglobin.

• White Blood Cells (Leukocytes): Involved in immune defense; types include neutrophils, lymphocytes, monocytes, eosinophils, and basophils.

• Platelets (Thrombocytes): Cell fragments essential for blood clotting.

Blood Clotting (Hemostasis)

Hemostasis is the process that prevents blood loss after vessel injury.

• Vascular Spasm: Immediate vasoconstriction to reduce blood flow.

• Platelet Plug Formation: Platelets adhere to exposed collagen and aggregate.

• Coagulation Cascade: Series of enzymatic reactions leading to fibrin clot formation.

• Pathways: Intrinsic and extrinsic pathways converge on a common pathway to form fibrin.

Blood Types and Transfusion

Blood types are determined by the presence or absence of specific antigens on RBC surfaces.

• ABO System: Four main types: A, B, AB, and O, based on A and B antigens.

• Rh Factor: Presence (+) or absence (−) of the D antigen.

• Transfusion Reactions: Occur if incompatible blood is transfused, leading to agglutination and hemolysis.

Blood Type	Antigens on RBC	Antibodies in Plasma	Can Receive From	Can Donate To
A	A	Anti-B	A, O	A, AB
B	B	Anti-A	B, O	B, AB
AB	A, B	None	A, B, AB, O	AB
O	None	Anti-A, Anti-B	O	A, B, AB, O

Lymphatic System

The lymphatic system returns excess tissue fluid to the bloodstream and plays a role in immune defense.

• Lymph Vessels: Collect and transport lymph (interstitial fluid) back to the circulatory system.

• Lymph Nodes: Filter lymph and house immune cells.

• Other Organs: Spleen, thymus, tonsils, and Peyer's patches.

Clinical Correlations

• Erythrocyte Disorders: Anemia (low RBCs or hemoglobin), polycythemia (excess RBCs).

• Hemostatic Imbalances: Hemophilia (clotting factor deficiency), thrombocytopenia (low platelets).

• Lymphatic Disorders: Lymphedema (swelling due to lymph accumulation), lymphoma (cancer of lymphatic tissue).

Key Terms and Definitions

• Hemodynamics: The study of blood flow and the forces involved.

• Hematopoiesis: The formation of blood cells, primarily in the bone marrow.

• Hemostasis: The process of stopping bleeding.

• Serum: Plasma without clotting proteins.

Sample Questions for Review

• What are the main parts of the conduction system of the heart?

• How do arteries differ from veins in structure and function?

• What are the steps of hemostasis?

• How is blood type determined and why is it important for transfusions?

• What is the function of the lymphatic system?

Additional info: Academic context and definitions have been expanded for clarity and completeness. Table entries and some clinical correlations are inferred based on standard Anatomy & Physiology curriculum.

SERUM vs PLASMA

Plasma

• Liquid portion of blood WITH clotting proteins

• Makes up ~55% of whole blood

• Contains:

  • Water

  • Electrolytes

  • Nutrients

  • Hormones

  • Plasma proteins

  • Clotting factors (fibrinogen, prothrombin)

Serum

• Plasma WITHOUT clotting proteins

• What remains after blood has clotted

• Contains:

  • Water

  • Electrolytes

  • Antibodies

  • Hormones

• No fibrinogen or clotting factors

👉 Key difference: Plasma = clotting factors present Serum = clotting factors removed

🧬 PLASMA PROTEINS (PLASMA PRO’s)

1. Albumins

• Most abundant plasma protein

• Functions:

  • Maintain osmotic pressure (keeps water in blood)

  • Transport fatty acids, hormones, drugs

• Low albumin → edema

2. Globulins

Divided into:

• Alpha & Beta globulins

  • Transport lipids, metal ions, fat-soluble vitamins

• Gamma globulins (Immunoglobulins)

  • Antibodies

  • Immune defense

3. Fibrinogen

• Clotting protein

• Converted to fibrin during clot formation

4. Regulatory Proteins

• Enzymes

• Hormones

• Cytokines

• Control metabolism and immune responses

🔴 WHY RBCs HAVE THEIR SHAPE

Biconcave disc shape

• Thin center, thicker edges

Advantages

1. Increased surface area

   • More efficient gas exchange

2. Flexible

   • Can squeeze through narrow capillaries

3. Short diffusion distance

   • O₂ and CO₂ move quickly

What specifically carries oxygen?

• Hemoglobin

  • Iron (Fe²⁺) in the heme group binds O₂

  • Each hemoglobin carries 4 O₂ molecules

🧪 BLOOD-CLOTTING CASCADE (COAGULATION)

Purpose: Convert liquid blood into a solid clot

Intrinsic Pathway

• Triggered by damage inside blood vessels

• Slower

• Uses clotting factors already present in blood

• Common in vessel injury

Extrinsic Pathway

• Triggered by tissue damage outside vessels

• Faster

• Uses tissue factor (Factor III)

Common Pathway

Both pathways converge:

1. Prothrombin → Thrombin

2. Fibrinogen → Fibrin

3. Fibrin forms a mesh that traps cells → clot

🩹 HEMOSTASIS

Hemostasis = stopping bleeding

3 Phases

1. Vascular spasm

   • Blood vessel constricts

2. **Platelet plug formation

PATH OF BLOOD THROUGH THE HEART & BODY (STRUCTURES INCLUDED)

Deoxygenated Blood (from body → lungs)

1. Superior & Inferior Vena Cava

   • Bring deoxygenated blood from body

2. Right Atrium

   • Receives deoxygenated blood

3. Right AV (Tricuspid) Valve

   • Prevents backflow into right atrium

4. Right Ventricle

   • Pumps blood to lungs

5. Pulmonary Semilunar Valve

   • Prevents backflow into right ventricle

6. Pulmonary Trunk → Pulmonary Arteries

   • Carry blood to lungs

Oxygenated Blood (lungs → body)

7. Pulmonary Veins

   • Bring oxygenated blood to heart

8. Left Atrium

9. Left AV (Bicuspid/Mitral) Valve

10. Left Ventricle

    • Strongest chamber

11. Aortic Semilunar Valve

12. Aorta

    • Sends blood to body tissues

⚡ CARDIAC CONDUCTION SYSTEM (Slides 21–23)

Controls heart rhythm

1. SA Node

   • Pacemaker

   • Initiates heartbeat

2. AV Node

   • Delays impulse

3. AV Bundle (Bundle of His)

   • Conducts impulse to ventricles

4. Right & Left Bundle Branches

5. Purkinje Fibers

   • Cause ventricular contraction

🧱 LAYERS OF THE HEART

1. Endocardium

   • Inner lining

2. Myocardium

   • Cardiac muscle (contracts)

3. Epicardium

   • Outer layer

Pericardium

• Fibrous pericardium (protection)

• Serous pericardium (reduces friction)

🚪 HEART VALVES (LOCATION & FUNCTION)

Valve	Location	Function
Tricuspid	RA → RV	Prevents backflow to RA
Pulmonary	RV → Pulmonary trunk	Prevents backflow to RV
Mitral (Bicuspid)	LA → LV	Prevents backflow to LA
Aortic	LV → Aorta	Prevents backflow to LV

🔬 MICROSCOPIC ANATOMY OF CARDIAC MUSCLE

Key Features

• Striated

• Single nucleus

• Involuntary

Intercalated Discs

Contain:

1. Interdigitating folds

   • Increase strength

2. Desmosomes

   • Mechanical attachment

3. Gap junctions

   • Electrical connection (synchronized contraction)

🧬 LAYERS (TUNICS) OF BLOOD VESSELS

1. Tunica Intima

   • Inner lining

2. Tunica Media

   • Smooth muscle

3. Tunica Externa

   • Connective tissue

❤️ CORONARY CIRCULATION

• Supplies blood to heart muscle

• Right & Left Coronary Arteries

• Drain via cardiac veins → coronary sinus → right atrium

• Blockage → heart attack (myocardial infarction)

📉 ECG (Slide 29)

Wave	Meaning
P wave	Atrial depolarization
QRS complex	Ventricular depolarization
T wave	Ventricular repolarization

🧫 TYPES OF CAPILLARIES (Slides 44–46)

1. Continuous

   • Skin, muscle, brain

2. Fenestrated

   • Kidneys, intestines

3. Sinusoidal

   • Liver, spleen, bone marrow

💧 STARLING’S FORCES (Filtration & Reabsorption)

• Blood hydrostatic pressure pushes fluid out

• Osmotic pressure pulls fluid in

• Imbalance → edema

💪 MUSCLE TWITCH PHASES

1. Latent Phase

   • Calcium released

2. Contraction Phase

   • Muscle shortens

3. Relaxation Phase

   • Calcium removed, muscle relaxes

👶 FETAL HEART BYPASS STRUCTURES

1. Foramen Ovale

   • RA → LA

2. Ductus Arteriosus

   • Pulmonary artery → aorta

3. Ductus Venosus

   • Umbilical vein → vena cava

🧠 AUTONOMIC NERVOUS SYSTEM (ANS)

SNS (Fight or Flight)

• ↑ Heart rate

• ↑ Blood pressure

PNS (Rest & Digest)

• ↓ Heart rate

🩸 HEMATOCRIT

• % of blood that is RBCs

• Can change with:

  • Dehydration

  • Anemia

  • Altitude

🦠 WHITE BLOOD CELLS (WBCs)

Type	Function	Increased When
Neutrophils	Bacteria	Infection
Lymphocytes	Immunity	Viral infection
Monocytes	Phagocytosis	Chronic infection
Eosinophils	Parasites	Allergies
Basophils	Histamine	Allergies

🩸 FUNCTIONS OF BLOOD

• Transport gases, nutrients, wastes

• Regulation of pH & temperature

• Protection (immune & clotting)

🧬 HEMOPOIESIS

• Blood cell formation

• Occurs in red bone marrow

• Produces:

  • RBCs

  • WBCs

  • Platelets