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Cardiovascular System. Honors Anatomy & Physiology. Introduction Placement Mediastinum – slightly to the left Size Heart – fist covered by second hand Aorta – diameter of dominant thumb. II. Protection and Layers of the Heart A. Protection - Pericardial Sac

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Cardiovascular system

Cardiovascular System

Honors Anatomy & Physiology



Mediastinum – slightly to the left


Heart – fist covered by second hand

Aorta – diameter of dominant thumb

II. Protection and Layers of the Heart

A. Protection - Pericardial Sac

1. Pericardial Membrane

a) Double layered sac with slick pericardial fluid in between tissue layers

b) Purpose: absorb and reduce friction

2. Parietal Pericardium

a) Tough layer of connective tissue

b) Has connective tissue extending from the outside of itself to anchor it to other tissues

3. Visceral Pericardium

a) Covers the outside of the heart

b) Also referred to as “epicardium”

c) Simple squamous epithelium

(1) Surface of heart is slick and smooth

4. Pericardial fluid

a) Secreted by visceral layer

b) 10-20 mLof pericardial fluid

c) Lubrication

B. Layers of the Heart

1. Epicardium

a) Slick layer of simple squamous cells =

visceral layer of pericardial sac

2. Myocardium

a) Heart muscle

b) Characteristics of myocardial cells

(1) Short and branched

(2) Join each other with Gap Junctions =

intercalated discs

(a) Ensures that when one cardiac cell

contracts, its partners will contract with it

(b) Sets up teamwork = All or None


(c) Chamber of heart made up of these

cells contracts completely or not at all

(3) Have sarcomeres with visible A and I bands

= striated

(4) Have automaticity - Self-stimulating and are rhythmic

(a) Do not need nervous system to stimulate

them to contract

(b) Nervous system can INFLUENCE these

cardiac cells to speed up (release of

epinephrine) or slow down (vagus nerve

releasing acetylcholine)

(5) Use free fatty acids for fuel instead of glucose

Are life-long cells and in permanent


(a) If these cells die, they are

replaced with scar tissue

(i) Tough patch

(ii) Decreases heart chamber’s

ability to contract

Have a single nucleus, centrally


3. Endocardium

a) Lines the inside of the heart chambers

b) Same tissue called “endothelium” as it

continues into entering and exiting blood


c) Made of simple squamous epithelial tissue

d) Provides a slick surface for blood to pass

over and through heart

Heart Chambers

Atria – Receiving Chambers

2 upper chambers of the heart

Thin walls; smooth inner surface

Right atrium receives deoxygenated blood from body

Superior vena cava – brings blood from upper body

Inferior vena cava – brings blood from legs and lower body

Left atrium receives oxygenated blood from lungs

Left and right pulmonary veins (2 each)

Ventricles – Pumping Chambers

2 lower chambers

Thicker walls; irregular inner surface

Contain papillary muscles and chordaetendinae to prevent heart valves from turning inside out during ventricular contraction

Right ventricle pumps blood to lungs through pulmonary artery

Left ventricle pumps blood to body through aorta

Wall is 3x’s thicker than right

IV. Valves of the Heart and Heart Sounds

Tough, fibrous tissue between heart chambers and major blood vessels of heart

Gate-like structures – One-way valves

Blood should always travel from the Atria  Ventricle major artery (Pulmonary or Aorta)

A. Atrioventricular valves

1. Characteristics

a) Located between atria and ventricle

b) Made of leaflets, known as “cusps”

c) Have a strong cord of connective tissue anchoring the leaflet = chordaetendinae

(1) Keeps cusps from flopping back into atria during ventricular contraction

(2) If too long or have been damaged, cusp will go past its stopping point and “flop” up into the atria

(a) Causes heart to have to re-pump the same blood

(b) Causes congestion as new blood is trying

to come into atria

(c) Known as “murmur” (leaky valve)

d) Chordaetendinae anchored to ventricular wall by papillary muscles

2. Tricuspid valve

a) Located between right atrium and right ventricle

b) Has three leaflets

3. Bicuspid/Mitral valve

a) Located between left atrium and left ventricle

b) Has 2 leaflets – thicker and tougher than tricuspid valve

4. Sound – When AV valves close, make a “LUB” sound – loudest of the two heart sounds

B. Semilunar valves

1. Characteristics

a) Built differently from AV valves

b) Leaflets, or cusps, are made of a half- moon shaped piece of connective tissue

c) They have no chordaetendinae or papillary muscles

d) Both semilunar valves consist of three leaflets

2. Pulmonary semilunar valve

a) Found in the Pulmonary Artery (trunk)

b) Prevent blood from going back into right ventricle

3. Aortic semilunar valve

a) Found in the Aorta (just as the aorta leaves the heart)

b) Prevents blood from going back into the left ventricle

4. Action

a) Opposite of AV valves in their action

b) Closed most of the time

c) Only time they open is when the ventricles are pumping or ejecting blood out

d) When ventricles relax, blood close to valve falls back toward ventricle

e) Valves “catch” the blood by closing and prevent backflow

5. Sound – When semilunar valves fill and close, they make a soft “dup” sound

**Heart sounds w/ flow of pumping


Pulmonary Circulation

Heart → Lungs →Heart

Coronary Circulation

Heart → Heart → Heart

Systemic Circulation

Heart → Body → Heart

VI. Electrical System of the Heart

A. Understanding the Electrical System of the Heart

1. SA node (Sinoatrial node)

a) Located in upper right atrium

b) Pacemaker

(1) Begins the cycle of the heart firing

(2) When it fires (depolarizes), the atria contract and electrical stimulation goes to the AV node

(3) Has it own pace

(4) Contraction of atria is from top to bottom

(5) Can be influenced by autonomic nervous system

(a) Sympathetic NS can speed it up

(b) Parasympathetic NS can slow it down – Vagus

nerve (Cranial nerve X)

2. AV node (Atrioventricular node)

a) Located at the base of right atrium, close to AV valve and

atrial septum

b) Will send the depolarization (electrical stimulus) to the

Bundle of HIS

3. Bundle of HIS

a) These fibers go through the ventricular septum

b) Split into left and right bundle

c) No contraction of heart muscle occurs

4. Purkinje fibers

a) Bundles connect up with Purkinje fibers at the apex

b) Embedded in the myocardium of the ventricles

c) Contraction of ventricles is from bottom to top

B. Acting out the electrical system

1. SAAV, Bundle, PurkinjeBOOM!

2. Pause that occurs between atrial contraction and ventricular contraction allows the ventricles to fill with blood


A. Understanding the parts of the ECG

1. P wave

a) Represents the SA node firing and the atria contracting

b) Depolarization of atria

2. QRS complex

a) Records the depolarization of the AV, Bundle, and Purkinje fibers as they cause the big ventricles to contract

b) Atria are repolarizing, but big ventricular depolarization covers this up

3. T wave

a) Repolarization of ventricles

B. Acting Out the ECG

Application Using the ECG

First ECG Strip

SA node is not firing

“Ectopic Pacemaker” – AV node takes over the job of being the pacemaker

Second ECG Strip

AV node isn’t firing consistently

Known as “partial AV block” – if not corrected, person could die

Correcting the problem of ectopic pacemaker and partial AV block

Can both be corrected by inserting a pacemaker

Third ECG Strip

Ventricular Tachycardia

Ventricles are pumping so fast that very little blood fills the ventricles and goes out to their loops

6 – 10 minutes of this activity becomes life threatening

Sympathetic NS out of control!!

Parasympathetic NS must be activated to help slow the heart down


Heart attack may make heart cells oversensitive and they get out of rhythm

Illegal stimulants – cocaine, methamphetamine, heroine

Fourth ECG Strip


Atria and ventricles are all out of rhythm and not pumping any blood

External defibrillation device – shot of electricity helps heart to start over – resets SA node


Heart attack

Household accidental electrocution

VIII. Cardiac Cycle

A. Steps

1. Passive Filling

a) As blood coasts during diastolic pressure, atria fill

b) AV valves are open and blood falls down to ventricles – which fill 70%

2. Atrial contraction (SA Node and P wave)

a) Atria contract and send 30% of blood to ventricles

3. Ventricular Systole

a) Contraction Phase: (LUB)

(1) As ventricles begin to contract, blood is compressed

(2) Semilunar valves are already closed so blood moves back toward atria, causing AV valves to close

(3) Increased pressure causes semilunar valves to open

b) Ventricular Ejection Phase: (QRS Complex)

(1) Once SL valves open, ventricle walls contract and eject blood out into the arteries

(2) Only 88% is ejected

(3) Both ventricles pump same amount of blood

(4) Right side pumps with 1/5 the force of left side

4. Relaxation (dup and T wave)

a) Ventricles begin to repolarize and relax

b) SL valves close due to backflow of blood, AV valves open, allowing passive filling – cycle repeats

B. Cardiac Output

1. Amount of blood pumped out of the ventricles in one minute

2. Heart rate = pulse

a) Beats/min.

b) 70-80 bpm average

Stroke Volume

Amount of blood out of the ventricle with each contraction

70 mL

CO = HR x SV

Cardiac Output = Heart Rate x Stroke Volume

Cardiac Reserve

As demands of body increase during exercise, CO must increase to meet demand

In non-athletes, CR = 4 x CO

In active or athletic people, CR = 7 x CO

IX. Blood Pressure – Push or force of blood against blood vessel wall

A. Having Your Heart in Your Hands for

Blood Pressure

1. Push – Coast

2. Systolic – Diastolic

3. 120 – 80

4. Top number – Bottom number

5. First beat I hear – Last beat I hear

B. Measured in mm of Hg blood vessel wall

BP = CO x PR

Blood Pressure = Cardiac Output x Peripheral Resistance

D. Normals

1. Systolic = 100 – 130 mm Hg

2. Diastolic = 60 – 90 mm Hg

E. Hypotension = systolic < 90 mm Hg

F. Hypertension = systolic > 140 mm Hg

and/or diastolic > 90 mm Hg

G. Factors affecting BP blood vessel wall

1. Cardiac output (blood discharged by left


2. Peripheral resistance – resistance of wall against the blood as is rushes through the vessel

3. Blood volume – hemorrhage causes

 BV  BP

4. Viscosity of blood -  in thickness =  BP

X. Overview of Blood Vessels blood vessel wall

A. General Composition and Function

1. Allow for circulation of blood and other body fluids to all body cells

2. Three layers

a) Tunica externa– outer layer of tough, fibrous tissue

b) Tunica media – smooth muscle – allows vessels to constrict/dilate

c) Tunica interna– smooth, inner layer; also known as “endothelium”

B. Arteries blood vessel wall

1. Carry blood AWAY from the heart

2. All but pulmonary arteries carry oxygenated blood

3. Aorta – largest, with thickest wall, ~ 1 in. in diameter

4. Arteries – large to medium sizes

5. Arterioles – smallest arteries

C. Veins blood vessel wall

1. Carry blood TOWARD the heart

2. All but pulmonary veins carry deoxygenated blood

3. Layers much thinner, less elastic

4. Series of internal valves – 1-way valves help move blood up to the heart

5. Superior and inferior vena cava – largest veins

6. Venules – smallest veins

D. Capillaries – This is where the work is done! blood vessel wall

1. Tiny, microscopic vessels

2. Red blood cells move through in single file

3. Walls are one cell layer thick

4. Function

a) Gas exchange: Drop off O2 & pick up CO2 from body

b) Nutrient drop-off

c) Waste pick-up

Fetal circulation blood vessel wall

Modifications required for fetus because fetus is not breathing, so oxygenated blood must be obtained in another fashion.

Unique structures

Placenta – connection and filter between mom & baby

Umbilical arteries and vein

Umbilical artery – carries deoxygenated blood from baby back to mom for processing and oxygenation

Umbilical vein – carries oxygenated blood from mom to baby

Ductus blood vessel wallvenosus allows placental blood to bypass fetal liver

Ductusarteriosus connects aorta and pulmonary trunk

Foramen ovale

Flap of tissue in atrial septum

Allows blood to go directly from right atrium to left atrium

Fetal blood vessel wallCirculation