Download Right Atrium

Topic 2
The Heart
Objective 1
Function of the Heart
The function of the heart is to provide pressure for pumping blood into
the arteries of systemic circulation. The heart functions as a pump by
alternatively contracting and relaxing.
Diastole:
Systole:
relaxation phase; during diastole, the pressure
in a chamber of the heart is reduced
contraction phase; during systole, the pressure
in a chamber of the heart is increased
Ventricular
Diastole
Pressure low, Ventricles fill
Ventricular
Systole
Pressure elevated, Ventricles empty
Objective 2
Size and Position of the Heart
A. Size of the Heart
♥
About the size of a fist
♥
Average dimensions of an adult heart: 12 cm
X 9 cm X 6 cm
♥
Average weight of the adult heart
Males:
280-340 grams
Females:
230-280 grams
B. Location of the Adult Heart
♥
Lies in the mediastinum
♥
2/3rds to the left of the midline
♥
Medial to the lungs
♥
Directly posterior to the sternum
♥
Anterior to the esophagus
♥
Base
of the heart lies at T5-T8
♥
Apex
of the heart lies in the 5th intercostal space, about 9cm to
the left of the body’s midline
Note: The location of the base and apex of the heart are counter intuitive!
Objective 3
The Pericardium
The pericardium is a double walled sac that surrounds the heart.
A. Structure
Fibrous pericardium: superficial portion made of dense irregular
connective tissue
Functions:
1.
2.
3.
Protects the heart
Anchors the heart to surrounding structures
Prevents overfilling of the heart
Serous pericardium:
deeper serous membrane, composed of
areolar connective tissue and mesothelium (simple squamous epithelium)
which secretes pericardial fluid
Parietal layer: lines the internal surface of the fibrous pericardium
Visceral layer: adheres to the surface of the heart; is also called the
epicardium
Pericardial cavity: space between the parietal and visceral layer that
contains pericardial fluid
Functions:
pericardial fluid
lubricates
surfaces and
reduces friction
Pericardial Sac Intact
Sac Cut Away
Objective 4
Tissues of the Heart Wall
The tissues that make up the wall of the heart are organized into three
layers:
Layer
Location
Structure
Function(s)
Epicardium
(Visceral pericardium)
outer layer
described in
objective 3
Cells secrete
serous fluid
Myocardium
Layer
Location
Structure
Myocardium
middle layer
cardiac muscle cells
Cardiac muscle:
(myocytes) held in place by contracts to eject blood
collagen and elastic fibers into arteries
(called the fibrous skeleton)
Fibrous skeleton:
Function(s)
stabilizes the position
of valves and myocytes
helps to distribute
the force of contraction
Adds strength and
helps to prevent
overdistention
Helps to maintain the
shape of the heart
Provides elasticity
Isolates atrial muscle
cells from ventricular
muscle cells
Vascular Supply to the myocardium: vessels of
coronary circulation
The heart is filled with blood, why does it need it’s own
circulation?
Nerve Supply: Autonomic NS
SNS: Cardiac Nerves
increases rate
and strength of
contraction
PNS: Vagus Nerve (X)
decreases rate
and strength of
contraction
Layer
Location
Structure
Function(s)
Endocardium
inner layer which
lines the
ventricles and
covers valves
endothelium (simple
squamous epithelium/
areolar connective
tissue
maintains a smooth
surface for blood
flow
Objective 5
Structures of the Heart
The heart has four chambers:
Atria:
superior chambers which receive deoxygenated blood from
systemic circulation (right atrium) and oxygenated blood from
the lungs (left atrium)
 The atria are separated from each other by an
interatrial septum
Ventricles:
inferior chambers which distribute deoxygenated blood to lungs
(right ventricle) and oxygenated blood to systemic circulation
(left ventricle)
 The ventricles are separated from each other by an
interventricular septum
Right and Left Atria:
♥
superior chambers
are separated from each other by an interatrial septum
What To Look For In The Atria:
Auricle
Pectinate Muscles
Crista terminalis
Fossa Ovalis
Crista terminalis: location of the SA node
Patent Foramen Ovale
Attached Vessels:
Right Atrium
Left Atrium
SVC, IVC
pulmonary veins
coronary sinus
Right Atrium:
receives deoxygenated blood from systemic
circulation
Left Atrium
receives oxygenated blood from pulmonary
circulation
Right and Left Ventricles:
♥ they are separated from each other by an
interventricular septum
What to look for in the ventricles:
Trabeculae Carneae
Papillary Muscles
Note: The left ventricular
wall is thicker than
the right ventricular
wall
The apex lies in
the floor of the left
ventricle
Right
Ventricle
Left
Ventricle
Attached Vessels:
Right Ventricle
Left Ventricle
pulmonary trunk
aorta
B. Heart Valves
♥ The heart valves prevent blood from moving backwards
Mnemonic for remembering order of valves: Try Pulling My Aorta
(Tricuspid, Pulmonary, Mitral, Aortic)
Right Atrio-ventricular Valve
Tricuspid Valve
Lies between the right atrium
and the right ventricle
Left Atrio-ventricular Valve
Bicuspid Valve
Lies between the left atrium
and the left ventricle
Also called mitral
Try before you buy!
Mitral Valve
Valve Mechanism:
Semilunar Valves
Pulmonary:
lies at the base of the pulmonary trunk
Aortic
lies at the base of the aorta
Semilunar
Valves
C. External Features of the Heart
Base
Apex
Coronary Sulcus
Anterior Interventricular Sulcus
Posterior Interventricular Sulcus
Objective 6
Great Blood Vessels
Superior Vena Cava (SVC): Carries deoxygenated blood from areas of
systemic circulation above the diaphragm to the
right atrium
Inferior Vena Cava (IVC): Carries deoxygenated blood from areas of systemic
circulation below the diaphragm to the right atrium
Pulmonary Trunk (Artery):
Carries deoxygenated blood from the
right ventricle towards the lungs
Pulmonary Veins (4):
Carries oxygenated blood from the
lungs to the left atrium
Aorta:
Carries oxygenated blood from the left
ventricle to systems of the body
Objective 7
Circulation of Blood Through The Heart
Superior/Inferior
Vena Cava
Right Atrium
Right Ventricle
(Through the
Tricuspid Valve)
Pulmonary Trunk/Arteries
(Through the Semilunar Valve)
Lungs
Systemic
Circulation
Body Tissues
Aorta (Through
the Semilunar
Valve)
Left Ventricle
(Through the
Mitral Valve)
Left Atrium
Pulmonary
Veins