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Week 5-1 Heart Structure-Function
Anatomy & Physiology Course Overview
Copyright © McGraw Hill LLC. All rights reserved.
Course: BIOL 103, 5 credits.
Week 5 topics will include:
Parts of the human body using anatomical terms (~2%).
Structure-function relationship (~60%).
Homeostatic mechanisms in the human body (~10%).
Microbiology and body defenses against infections (~15%).
Laboratory activities (~15%).
Cardiovascular System Introduction
The cardiovascular system is a closed circuit consisting of:
Heart.
Blood vessels: arteries, capillaries, and veins.
Functionality: Vital for:
Transporting blood away from the heart (arteries).
Returning blood toward the heart (veins).
Allowing gas exchange at the capillaries.
Supplying oxygen and nutrients to tissues while removing wastes.
Blood Circulation
There are two main circuits in the cardiovascular system:
Pulmonary Circuit:
Transports oxygen-poor blood to the lungs to pick up oxygen and release carbon dioxide.
Systemic Circuit:
Distributes oxygen-rich blood to all body tissues, where it delivers oxygen and collects carbon dioxide.
Location and Structure of the Heart
Heart Anatomy:
Hollow, cone-shaped muscular pump located in the mediastinum of the thoracic cavity.
Average size: about the size of a fist.
Positioned between the lungs, anterior to the vertebral column, and posterior to the sternum.
Structural Parts:
Coverings of the heart.
Wall of the heart.
Heart chambers and valves.
Coverings of the Heart
Pericardium: A protective sac that encloses the heart, consists of:
Fibrous Pericardium: Tough outer layer made of connective tissue.
Serous Pericardium: Delicate inner double-layered membrane:
Parietal Pericardium: Outer serous layer.
Visceral Pericardium (Epicardium): Inner layer that covers the heart.
Pericardial Cavity: Space between visceral and parietal layers containing serous fluid to reduce friction.
Wall of the Heart
Composed of 3 layers:
Epicardium (Visceral Pericardium): Outermost layer, acts as a protective layer reducing friction.
Myocardium: Middle layer, made of cardiac muscle, responsible for pumping blood; it's the thickest layer.
Endocardium: Innermost layer that lines the heart chambers, continuous with the endothelium of major vessels.
Heart Chambers and Valves
The heart has 4 chambers:
Atria:
Upper chambers with thin walls; receive oxygen-poor blood returning to the heart.
Ventricles:
Lower chambers with thick walls; pump oxygen-rich blood out of the heart.
Septum: Separates left and right atria and ventricles.
Types of Valves in the Heart
Atrioventricular (AV) Valves:
Enable one-way flow of blood from atria to ventricles:
Right AV valve (Tricuspid).
Left AV valve (Bicuspid or Mitral).
Chordae Tendineae: Connect the AV valves to papillary muscles; prevent backflow of blood during ventricular contraction.
Valve Functionality
Aortic Valve:
Located at the base of the aorta; opens during left ventricle contraction.
Pulmonary Valve:
Located at the base of the pulmonary trunk; opens during right ventricle contraction.
Blood Flow Mechanics
Blood flow is continuous and occurs through two circuits:
Pulmonary Circuit: Blood flow between heart and lungs.
Systemic Circuit: Blood flow between heart and body tissues.
Details of Blood Flow
Blood enters the right atrium from the body via:
Superior and Inferior Vena Cavae (carry oxygen-poor blood).
Coronary Sinus (drains myocardium).
Blood flows through:
Tricuspid Valve into the Right Ventricle; then through the Pulmonary Valve into the Pulmonary Trunk.
In the lungs, blood exchanges gases (drops CO2, picks up O2).
Oxygen-rich blood returns to the Left Atrium via pulmonary veins, moving to the Left Ventricle and then into the Aorta.
Heart Valves and Their Functions
Table of Heart Valves:
Valve
Location
Function
Tricuspid Valve
Between right atrium and right ventricle
Prevents backflow to the atrium during ventricular contraction.
Pulmonary Valve
Entrance to pulmonary trunk
Prevents backflow to the ventricle during relaxation.
Mitral Valve
Between left atrium and left ventricle
Prevents backflow to the atrium during ventricular contraction.
Aortic Valve
Entrance to aorta
Prevents backflow to the ventricle during relaxation.
Blood Supply to the Heart
Constant pumping action requires a continuous oxygen supply.
Coronary Arteries: First branches from the aorta, supplying oxygen-rich blood to the heart.
Blood flow increases during ventricular relaxation as myocardial vessels are less compressed.
Cardiac Veins: Drain blood from the heart muscle into the coronary sinus, which empties into the right atrium.
Heart Actions and Cardiac Cycle
Heart chambers function in a coordinated manner through two states:
Systole: Contraction of heart chambers.
Diastole: Relaxation of heart chambers.
The cardiac cycle consists of:
Atrial systole (atria contract) while ventricles relax.
Ventricular systole (ventricles contract) while atria relax.
Brief moment of relaxation for the entire heart.
Overview of the Cardiovascular System
Components:
Heart
Blood vessels: arteries, capillaries, and veins
Functions:
Transports blood away from the heart (arteries)
Returns blood toward the heart (veins)
Allows gas exchange at the capillaries
Supplies oxygen and nutrients while removing wastes
Circulation:
Pulmonary Circuit: Transports oxygen-poor blood to lungs, picks up oxygen, releases carbon dioxide
Systemic Circuit: Distributes oxygen-rich blood to body tissues
Heart Anatomy:
Cone-shaped muscular pump located in the thoracic cavity
Comprises three layers: epicardium, myocardium, endocardium
Contains four chambers (atria and ventricles) and valves (AV, aortic, pulmonary) to ensure one-way flow of blood
Blood Supply to the Heart:
Oxygen-rich blood supplied by coronary arteries, blood drained by cardiac veins into the right atrium
Cardiac Cycle:
Comprises diastole (relaxation) and systole (contraction) phases, coordinating the function of heart chambers.
