Heart

1
Chapter 15

• Heart

2
Overview

• Heart Size and location
• Layers of the heart
• Heart Two pumps
• Chambers
• Blood flow To and through
• Electrical conduction system
• Physiology
• -Cardiac cycle
• -Cardiac output

3

• Location of the Heart
• Between the lungs
• Left of the midline of the body
• In mediastinum
• Apex pointed toward left

4

• Structure of the Heart
• Three tissue layers
• Endocardium lines hearts interior
• Myocardium is thickest layer
• Epicardium is thin outermost layer

5

• The Pericardium
• The sac that encloses the heart
• Fibrous pericardium holds heart in place
• Serous membrane
• Parietal layer
• Pericardial cavity
• Visceral layer (epicardium)

6
Layers of the heart wall and pericardium. The
serous pericardium covers the heart and lines the
fibrous pericardium. ZOOMING IN Which layer of
the heart wall is the thickest?
7
Checkpoint 15-1 What are the names of the
innermost, middle, and outermost layers of the
heart? Checkpoint 15-2 What is the name of the
sac that encloses the heart?
8

• Special Features of the Myocardium
• Cardiac muscles
• Are lightly striated (striped)
• Have single nucleus cells
• Are controlled involuntarily
• Have intercalated disks
• Have branching muscle fibers

9

• Divisions of the Heart
• Double pump
• Right side pumps blood low in oxygen to the lungs
• Pulmonary circuit
• Left side pumps oxygenated blood to remainder of
  body
• Systemic circuit

10

• Four Chambers
• Right atrium
• Receives low-oxygen blood returning from body
  tissue through superior vena cava and inferior
  vena cava
• Left atrium
• Receives high-oxygen blood from lungs
• Right ventricle
• Pumps blood from right atrium to lungs
• Left ventricle
• Pumps oxygenated blood to body

11
The heart as a double pump. The right side of the
heart pumps blood through the pulmonary circuit
to the lungs to be oxygenated the left side of
the heart pumps blood through the systemic
circuit to all other parts of the body. ZOOMING
IN What vessel carries blood into the systemic
circuit?
12
The heart and great vessels. ZOOMING IN Which
heart chamber has the thickest wall?
13
Checkpoint 15-3 The heart is divided into four
chambers. What is the upper receiving chamber on
each side called? What is the lower pumping
chamber called?
14

• Four Valves
• Atrioventricular valves
• Entrance valves
• Right atrioventricular (AV) valve (tricuspid
  valve)
• Left atrioventricular (AV) valve (bicuspid valve)
• Semilunar valves
• Exit valves
• Pulmonary valve
• Aortic valve

15
Valves of the heart (superior view from anterior,
atria removed). (A) When the heart is relaxed
(diastole), the AV valves are open and blood
flows freely from the atria to the ventricles.
The pulmonary and aortic valves are closed. (B)
When the ventricles contract, the AV valves close
and blood pumped out of the ventricles opens the
pulmonary and aortic valves. ZOOMING IN How
many cusps does the right AV valve have? The
left?
16
Pathway of blood through the heart. Blood from
the systemic circuit enters the right atrium (1)
through the superior and inferior venae cavae,
flows through the right AV (tricuspid) valve (2),
and enters the right ventricle (3). The right
ventricle pumps the blood through the pulmonary
(semilunar) valve (4) into the pulmonary trunk,
which divides to carry blood to the lungs in the
pulmonary circuit. Blood returns from the lungs
in the pulmonary veins, enters the left atrium
(5), and flows through the left AV (mitral) valve
(6) into the left ventricle (7). The left
ventricle pumps the blood through the aortic
(semilunar) valve (8) into the aorta, which
carries blood into the systemic circuit.
17
Checkpoint 15-4 What is the purpose of valves in
the heart?
18

• Blood Supply to the Myocardium
• Coronary circulation
• Right coronary artery
• Left coronary artery
• Coronary sinus

19
Blood vessels that supply the myocardium.
Coronary arteries and cardiac veins are shown.
(A) Anterior view. (B) Posterior view.
20
Opening of coronary arteries in the aortic valve
(anterior view). (A) When the left ventricle
contracts, the aortic valve opens. The valve
cusps prevent filling of the coronary arteries.
(B) When the left ventricle relaxes, backflow of
blood closes the aortic valve and the coronary
arteries fill.
21
Checkpoint 15-5 The myocardium must have its own
vascular system to supply it with blood. What
name is given to this blood supply to the
myocardium?
22

• Function of the Heart
• Left and right sides of heart work together in
  cardiac
• cycle (heartbeat)
• Systole (active phase, contraction)
• Diastole (resting phase)

23
The cardiac cycle. ZOOMING IN When the
ventricles contract, what valves close? What
valves open?
24

• The Hearts Conduction System
• Electrical energy stimulates heart muscle
• Nodes
• Sinoatrial (SA) node (pacemaker)
• Atrioventricular (AV) node
• Specialized fibers
• Atrioventricular bundle (bundle of His)
• Purkinje fibers (conduction myofibers)
• Intercalated disks

25
Conduction system of the heart. The sinoatrial
(SA) node, the atrioventricular (AV) node, and
specialized fibers conduct the electrical energy
that stimulates the heart muscle to contract.
ZOOMING IN What parts of the conduction system
do the internodal pathways connect?
26
Checkpoint 15-6 The heartbeat is started by a
small mass of tissue in the upper right atrium.
This structure is commonly called the pacemaker,
but what is its scientific name?
27

• Cardiac Output
• Calculating cardiac output
• Cardiac output (CO)
• Stroke volume (SV)
• Heart rate (HR)
• CO HR 3 SV
• Starlings law of the heart changes force of
  myocardial contraction by stretch
• Inotropic effect refers to a change in force of
  myocardial contraction that does not depend on
  stretch.

28
Checkpoint 15-7 The cardiac cycle consists of an
alternating pattern of contraction and
relaxation. What name is given to the contraction
phase? Checkpoint 15-8 Cardiac output is the
amount of blood pumped by each ventricle in 1
minute. What two factors determine cardiac output?