BIOL239 General Anatomy - Lecture 11 Spring 2025

Cardiovascular System

  • Consists of the heart, blood, and blood vessels.
  • Works with the lymphatic system.

Heart Location and Orientation

  • Located within the thoracic cavity.
  • Apex lies to the left of the midline.
  • Great vessels extend into the superior mediastinum.

Pericardium and Heart Wall Layers

  • Pericardium: outer covering with fluid to reduce friction.
    • Serous pericardium: Parietal layer (attaches to body wall) and Visceral layer (attaches to organ) also known as Epicardium
  • Heart wall:
    • Epicardium
    • Myocardium: cardiac muscle
    • Endocardium: endothelial cells lining internal walls

Heart Chambers

  • Atria: superior chambers that receive blood from pulmonary and systemic circuits.
  • Ventricles: inferior pumping chambers.

Pulmonary and Systemic Circuits

  • Pulmonary circuit: right side receives oxygen-poor blood from the body and pumps it to the lungs (Right Atrium and Right Ventricle).
  • Systemic circuit: left side receives oxygenated blood from the lungs and pumps it throughout the body (Left Atrium and Left Ventricle).

Blood Flow Through the Heart

  • Oxygen-poor blood enters the right atrium via the superior vena cava (SVC), inferior vena cava (IVC), and coronary sinus.
  • Passes through the tricuspid valve to the right ventricle.
  • Pumped through the pulmonary semilunar valve into the pulmonary trunk and arteries to the lungs.
  • Oxygen-rich blood returns to the left atrium via pulmonary veins.
  • Flows through the mitral valve to the left ventricle.
  • Pumped through the aortic semilunar valve into the aorta for systemic circulation.

Gross Anatomy of the Heart

  • Right Atrium: Receives oxygen-poor blood from the systemic circuit through the superior vena cava and inferior vena cava.
  • Right Ventricle: Receives blood from the right atrium through the tricuspid valve and pumps blood into the pulmonary circuit through the pulmonary trunk; includes the pulmonary semilunar valve.
  • Left Atrium: Receives oxygen-rich blood from the lungs through pulmonary veins; opens into the left ventricle through the bicuspid valve.
  • Left Ventricle: Forms the apex of the heart; pumps blood through the systemic circuit via the aortic semilunar valve (aortic valve).

Heart Valves

  • Atrioventricular (AV) valves: Located between atria and ventricles (Right AV valve: tricuspid; Left AV valve: bicuspid).
  • Aortic and pulmonary valves: Located at the junction of ventricles and great arteries.
  • Chordae tendineae: Fibrous connections between valve leaflets and walls of ventricles, connected to papillary muscles.

Function of Atrioventricular Valves

  • Open: Blood returning to the heart fills atria, pressing against AV valves, forcing them open; atria contract, forcing additional blood into ventricles.
  • Closed: Ventricles contract, forcing blood against AV valve cusps, closing the valves; papillary muscles contract and chordae tendineae tighten, preventing valve flaps from everting into atria.

Function of Semilunar Valves

  • Open: Ventricles contract, pushing blood against semilunar valves, forcing them open.
  • Closed: Ventricles relax, blood flows back from arteries, filling the cusps of semilunar valves, and forcing them to close.

Heart Wall Thickness

  • Ventricle walls are three times thicker than atria walls.
  • Interventricular septum separates the right and left ventricles.

Cardiac Muscle Tissue

  • Cardiomyocytes: Striated with intercalated discs; sarcomere sliding during contraction.
  • Inherent rhythmicity: Can generate and conduct impulses to contract rhythmically.

Intrinsic Conducting System

  • SA node (sinoatrial node): Sets the inherent rate of contraction (pacemaker).

Electrical Impulse Pathway

  1. SA node
  2. Internodal pathway to AV node (impulse delayed here)
  3. AV node to the AV bundle
  4. AV bundle to the bundle branches
  5. Bundle branches to the Purkinje fibers (subendocardial conducting network).

Blood Supply of the Heart

  • Left coronary artery: Supplies blood to the left ventricle.
  • Right coronary artery: Supplies blood to the right ventricle.
  • Coronary veins: Take deoxygenated blood from the heart wall to the right atrium (coronary sinus).

Blood Vessels

  • Arteries: Carry blood away from the heart.
  • Arterioles: Smallest arteries.
  • Capillaries: Smallest blood vessels.
  • Venules: Receive blood from capillaries.
  • Veins: Receive blood from venules.

Structure of Blood Vessel Walls

  • Tunica intima (innermost): Endothelial cells form this layer
  • Tunica media: Sheets of smooth muscle.
  • Tunica externa (adventitia): Connective tissue.
  • Lumen: Inside of vessels.

Arteries vs. Veins

  • Arteries are thicker than veins due to higher blood pressure and have elastic membranes.

Anatomy of the Aorta

  • Ascending aorta: Connects to left ventricle; coronary arteries branch point.
  • Aortic arch: Brachiocephalic artery (Right subclavian artery and Right common carotid artery), Left common carotid artery, and Left subclavian artery branch from here.
  • Descending aorta: Main artery vascularizing the rest of the body.

Subclavian Arteries

  • Become axillary arteries after crossing the first rib, serving as the main vessel of the upper limbs.

Abdominal Aorta

  • Branches vascularize the stomach, kidneys, and liver.
  • Superior mesentaric artery supplies blood to the mesentery.
  • Bifurcates into common iliac arteries.

Iliac Arteries

  • Common iliac arteries branch into internal and external iliac arteries.

Femoral Arteries

  • Extend from the external iliac arteries.

Types of Arteries

  1. Elastic arteries: Include the aorta and its major branches.
  2. Muscular arteries: Lie distal to elastic arteries.

Capillaries

  • Smallest blood vessels.

Capillary Functions

  • Lungs: Oxygen enters the blood, carbon dioxide leaves.
  • Small intestines: Receive digested nutrients.
  • Endocrine glands: Pick up hormones.
  • Kidneys: Removal of nitrogenous wastes.

Types of Capillaries

  • Continuous capillaries: Most common type, found in most organs; intercellular clefts allow small molecules in and out.
  • Fenestrated capillaries: Have pores in their endothelium; found where high rates of exchange occur (small intestines, glomeruli of kidneys, endocrine glands).

Venous Vessels

  • Conduct blood from capillaries toward the heart.
  • Blood pressure much lower than in arteries.
  • Veins: Lumens are larger than arteries.

Mechanisms to Counteract Low Venous Pressure

  • Valves: Prevent backflow of blood, found in limbs.
  • Skeletal muscle pump: Muscles press against thin-walled veins.

Vena Cavae

  • Inferior vena cava: Returns blood from body regions inferior to the diaphragm.
  • Superior vena cava: Returns blood from body regions superior to the diaphragm.

Brachiocephalic Veins

  • Branch off from the superior vena cava.

Jugular Veins

  • Internal and external jugular veins branch off from the brachiocephalic veins.

Blood Composition

  • Specialized connective tissue with cellular and liquid components.
  • Plasma: 55% of whole blood.
  • Buffy coat: Leukocytes and platelets (<1% of whole blood).
  • Erythrocytes: 45% of whole blood (most dense component).

Blood Components

  • 90% water.
  • Ions (Na+, Cl-).
  • Nutrients, waste.
  • Proteins (e.g., antibodies).
  • Leukocytes: Immune system’s first line of defense (innate immune cells).
  • Platelets: Help with blood clotting after vessel wound.
  • Erythrocytes: Oxygen-transporting cells.

Erythrocytes

  • Red blood cells (RBCs) make up the majority of blood’s cellular composition.
  • Use hemoglobin for gas exchange
    • O<em>2O<em>2 is released and CO</em>2CO</em>2 is picked up across tissue capilaries
    • Pick up O<em>2O<em>2 and release CO</em>2CO</em>2 in the lung capillaries.

Leukocytes

  • Protect the body from infectious pathogens.

Types of Leukocytes

  • Granulocytes: Neutrophils, Eosinophils, Basophils.
  • Agranulocytes: Lymphocytes, Monocytes.
  • Neutrophils: Most abundant WBC; attracted to bacteria products, phagocytose and destroy bacteria.
  • Eosinophils: Granules stain red; contain enzymes active during allergic reactions and parasitic infections.
  • Basophils: Granules secrete histamines.
  • Monocytes: Largest leukocyte; transform into macrophages to phagocytose infectious pathogens and damaged cells.
  • Lymphocytes: Act against specific foreign molecules of infectious organisms/viruses.
    • B-cells: Make antibodies.
    • T-cells: Attack foreign cells directly.