Cardiovascular System (ch 11)

a closed system of the heart and BVs. . .

the heart pumps blood and the BVs allow blood to circulate to all parts of the body

functions of the cardiovascular system

transport oxygen, nutrients, cell wastes, hormones to and from cells

the size of the heart is. . .

the size of a human fist

how much does the heart weigh?

less than a pound

where is the heart located?

in the thoracic cavity, btwn the lungs in the inferior mediastinum (medial section of the thoracic cavity)

apex of the heart

the pointed region that is directed toward the left hip and rests on the diaphragm

base of the heart

the area where great BVs emerge and points toward the right shoulder

what are the coverings of the heart?

pericardium

* fibrous pericardium
* serous membrane
* serous fluid

pericardium

a double walled sac

fibrous pericardium

loose and superficial

serous membrane

deep to the fibrous pericardium and composed of two layers

* parietal pericardium
* visceral pericardium

parietal pericardium

outside layer that lines the inner surface of the fibrous pericardium

visceral pericardium

next to the heart, also known as the epicardium

serous fluids

fill the space between the layers of the pericardium and reduce friction allowing the heart to beat correctly

pericardial cavity

space between the layers of the pericardium

what are the walls of the heart?

* epicardium
* myocardium
* endocardium

epicardium

aka visceral pericardium

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outermost layer of the heart wall

myocardium

middle layer composed mostly of cardiac muscle

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this layer contracts

endocardium

inner layer

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aka endothelium

how many chambers does the heart have?

4

what are the chambers of the heart?

R and L atria

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R and L ventricles

atria

right and left

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superior receiving chambers

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assist with filling the ventricles

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blood enter under low pressure from the veins of the body

ventricles

right and left

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inferior discharging chambers

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thick-walled pumps of the heart

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during contraction, blood is propelled into circulation

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blood leaves the heart under high pressure

interatrial septum

separates the 2 atria longitudinally

interventricular septum

separates the two ventricles longitudinally

heart functions as a double pump

arteries carry blood AWAY from the heart

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veins care blood TOWARDS the heart

double pump

the right side works as the pulmonary circuit pump

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the left side works as the systemic circuit pump

pulmonary circulation

blood flows from the right side of the heart to the lungs and back to the left side of the heart

* blood is pumped out of the right side via the pulmonary trunk, which splits into the pulmonary arteries and takes oxygen-poor blood to the lungs
* oxygen-rich blood returns to the heart from the lungs via the pulmonary veins

systemic circulation

oxygen-rich blood returned to the left side of the heart is pumped out into the aorta

* blood circulates to systemic arteries and to all body tissues
* left ventricle has thicker walls because it pumps blood to the body through the systemic circuit

oxygen-poor blood returns to the right atrium via systemic veins, which empty blood into the superior and inferior vena cava

heart valves

allow blood to flow in only one direction to prevent backflow

AV valves- what are they?

atrioventricular values

* located between atria and ventricles

left AV valve

* bicuspid/mitral valve

right AV valve

* tricuspid valve

semilunar valves- what are they?

located between the ventricle and artery

* pulmonary semilunar valve
* aortic semilunar valve

AV valves

chordae tendineae anchor the cusps to the walls of the ventricles

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AV values are open during heart relaxation, when blood is passively filling the chambers

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AV valves are closed during ventricular contraction

semilunar valves

are closed during heart relaxation

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are open during ventricular contraction

valves open and close in response to . . .

pressure changes in the heart

does the blood in the chambers nourish the heart, itself?

NO, the heart has its own nourishing circulatory system

what does the heart’s circulatory system consist of:

1. coronary arteries
2. cardiac veins
3. coronary sinus

coronary arteries

branch from the aorta to supply the heart muscle with oxygenated blood

* on the left: anterior interventricular artery and circumflex artery
* on the right: posterior interventricular artery and marginal artery

cardiac veins

drain the myocardium of blood

coronary sinus

a large vein on the posterior of the heart; receives blood from cardiac veins

* blood empties into the right atrium via the coronary sinus

intrinsic conduction system of the heart

cardiac muscle contracts spontaneously and can occur independently of nerve impulses

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contractions occur in a regular and continuous way

* atrial cells beat 60 times a minute
* ventricular cells beat 20-40 times per minute
* need a unifying control system- intrinsic conduction system (nodal system)

what are the two systems that regulate heart activity?

1. autonomic nervous system
2. intrinsic conduction system/nodal system


1. sets the heart rhythm
2. composed of special nervous tissue
3. ensures heart muscle depolarization in one direction only
4. enforces a HR of 75 bpm

components of the intrinsic conduction system

* sinoatrial node (SA node)
* located in the right atrium
* serves as the heart’s pacemaker
* AV node
* at the junction of the atria and ventricles
* bundle of his and bundle branches
* located in the interventricular septum
* purkinje fibers
* spread within the ventricle wall muscles

describe the pathway of a heartbeat

SA node starts each heartbeat

impulse spreads through the atriums to the AV node

Atria contract

at the AV node, the impulse is delayed briefly

impulse travels through the bundle of his, bundle branches, and purkinje fibers

Ventricles contract; blood is ejected from the heart

tachycardia

rapid heart rate

* over 100 bpm

bradycardia

slow heart rate

* less than 60 bpm

cardiac cycle

one complete heartbeat in which both atria and ventricles contract and then relax

systole

contraction

diastole

relaxation

average heart rate

75 bpm

cardiac cycle length

0\.8 seconds

steps of a cardiac cycle

1. atrial diastole (ventricular filling)
2. atrial systole
3. isovolumetric contraction
4. ventricular systole (ejection phase)
5. isovolumetric relaxation

atrial diastole (ventricular filling)

* heart is relaxed
* pressure in the heart is low
* AV valves are open
* blood flows passively into the atria and into ventricles
* semilunar valves are closed

atrial systole

* ventricles remain in diastole
* atria contract
* blood is forced into the ventricles to complete ventricular filling

isovolumetric contraction

* atrial systole ends; ventricular systole begins
* intraventricular pressure rises
* AV values close to prevent blood backflow into atria
* for a moment, the ventricles are completely closed chambers

ventricular systole (ejection phase)

* ventricles continue to contract
* intraventricular pressure now surpasses the pressure in the major arteries leaving the heart
* semilunar valves open
* blood is ejected from the ventricles
* atria are relaxed and filling with blood

isovolumetric relaxation

* ventricular diastole begins
* pressure in ventricles falls below that in the major arteries
* semilunar valves close to prevent blood backflow into the ventricles
* for another moment, the ventricles are completely closed chambers
* when atrial pressure increases above intraventricular pressure, the AV valves open

heart sounds

lub and dub

Lub

longer, louder heart sound

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caused by closing of AV valves

Dub

short, sharp heart sound

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caused by the closing of the semilunar valves at the end of ventricular systole

cardiac output

* amount of blood pumped by each side (ventricle) of the heart in 1 minute
* product of stroke volume and heart rate

stroke volume

* volume of blood pumped by each ventricle in one contraction (each heartbeat)
* about 70 milliliters of blood pumped out of the L ventricle with each heartbeat

heart rate

typically 75 bpm

CO equation

CO= HR \* SV

how much percent of blood in the ventricles in pumped out with each heartbeat?

60 %

Starling’s Law of the heart

* the critical factor controlling SV is how much cardiac muscle is stretched
* the more the cardiac muscle is stretched, the stronger the contraction

preload

how much cardiac muscle is stretched

* amount of blood getting to ventricles

venous return is the important factor influencing . . .

the stretch of heart muscle

what is venous return?

how much blood from the atriums to ventricles

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amount of blood getting into heart

what two factors influence preload?

1. amount of venous return
2. length of time the ventricles are relaxed and filling

contractility

the ability of the cardiac muscle tissue to generate tension

afterload

the amount of pressure the ventricles must overcome to eject blood

what factors modify basic heart rate?

1. neural (ANS) control
2. hormones and ions
3. physical factors

neural (ANS) control

* sympathetic nervous system speeds heart rate
* fight v. flight
* parasympathetic nervous system, primarily vagus nerve fibers, slow and steady heart rate
* rest and digest

hormones and ions

* epi and thyroxine speed up heart rate
* excess of lack of calcium, sodium, and potassium ions also modify heart activity

physical factors

* age
* gender
* exercise
* body temp

blood vessels

form a closed vascular system that transports blood to the tissues and back to the heart

vessels that carry blood away from the heart

arterioles and arteries

blood vessels that carry blood towards the heart

venules and veins

vessels that play a role in exchanges between tissues and blood

capillary beds

what are the three layers of the blood vessels?

1. tunica intima
2. tunica media
3. tunica externa

tunica intima

forms a friction-reducing layer

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inner most layer

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endothelium

tunica media

smooth muscle and elastic tissue

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controlled by sympathetic NS

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middle layer

tunica externa

forms protective outermost covering

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mostly fibrous connective tissue

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supports and protects the vessel

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outermost layer

arteries have a ______ tunica media than veins to withstand changes in pressure

heavier, stronger, stretchier

veins have a thinner tunica media than arteries and operate under low pressure

* have valves to prevent backflow of the blood
* lumen of veins is larger than that of arteries
* skeletal muscle “milks” blood in veins towards the heart

capillaries structure

* only one cell layer thick
* tunica intima
* allow for exchanges between blood and tissue
* form a network call capillary beds
* blood flow through a capillary bed is known as microcirculation

microcirculation

blood flow through the capillary beds

capillary beds

where arterioles and venules meet

special capillary beds of the mesentery have precapillary __ __and a__ __________

precapillary sphincters

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vascular shunt

precapillary sphincters

regulate blood flow through a capillary bed

vascular shunt

directly connects the arteriole and venule at opposite ends of the bed

when precapillary sphincter is open. . .

blood flows through and exchanges with cells can occur

when precapillary sphincter is closed. . .

blood flow through the shunt bypasses cells in that region

major arteries of systemic circulation

* aorta
* ascending aorta
* leaves the left ventricle
* aortic arch
* arches to the left
* thoracic arch
* travels downward through the thorax
* abdominal/descending aorta
* passes through the diaphragm into the abdominopelvic cavity
* arterial branches of ascending aorta
* R+L coronary arteries serve the heart
* arterial branches of the aortic arch
* brachiocephalic trunk splits into the:
* right common carotid artery
* right subclavian artery
* left common carotid artery splits into the:
* left internal and external carotid arteries
* left subclavian artery branches into the:
* vertebral artery
* in the axilla, the subclavian artery becomes the axillary artery to the brachial artery to the radial and ulnar arteries
* arterial branches of the thoracic aorta
* intercostal arteries supply the muscles of the thorax wall
* other branches of the thoracic aorta:
* lungs
* bronchial arteries
* esophagus
* esophageal arteries
* diaphragm
* phrenic arteries
* arterial branches of the abdominal aorta:
* celiac trunk is the first branch of the abdominal aorta, three branches are:
* left gastric artery
* stomach
* splenic artery
* spleen
* common hepatic artery
* liver
* superior mesenteric artery supplies most of the small intestine and 1st half of the large intestine
* arterial branch of the abdominal aorta:
* left and right renal arteries
* kidneys
* left and right gonadal arteries
* ovarian arteries in females serve the ovaries
* testicular arteries in males serve the testes
* lumbar arteries serve muscles of the abdomen and trunk
* inferior mesenteric artery serves the 2nd half of the large intestine
* left and right common iliac arteries are the final branches of the aorta
* internal iliac arteries serve the pelvic organs
* external iliac arteries enter the thigh, become the femoral artery, then the popliteal artery, then the anterior and posterior tibial arteries

major veins of systemic circulation

* superior and inferior vena cava
* superior drains the head and arms
* inferior drains the lower body
* veins draining into the superior vena cava
* radial and ulnar drain to brachial vein to axillary vein
* cephalic vein drains the lateral aspect of the arm and empties into the brachial vein
* basilic and cephalic veins are joined at the medial cubital vein (elbow area)
* subclavian vein receives:
* venous blood from the arm via the axillary vein
* venous blood from the skin and muscles via external jugular vein
* vertebral vein drains the posterior part of the head
* internal jugular vein drains the dural sinuses of the brain
* left and right brachiocephalic veins receive venous blood from the:
* subclavian veins
* vertebral veins
* internal jugular veins
* brachiocephalic veins join to form the superior vena cava to the right atrium of the heart
* azygos vein drains the thorax
* veins draining into the inferior vena cava
* anterior and posterior tibial veins and fibial veins drain the legs
* posterior tibial vein drains to popliteal vein to femoral vein to external iliac vein
* great saphenous vein receive superficial drainage of the legs
* each common iliac vein is formed by the union of the internal and external iliac vein on its own side
* right gonad vein drains the right ovary in females and right testicle in males
* left gonad vein empties into the left renal vein
* left and right renal veins drain the kidneys
* hepatic portal vein drains the digestive organs and travels through the liver before it enters systemic circulation
* left and right hepatic veins drain the liver

great saphenous veins

longest veins of the body

circle of Willis

arterial supply of the brain/cerebral arterial circle

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the way blood circulates in the brain, it goes in a circle

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internal carotid arteries divide into:

* interior and middle cerebral arteries
* supply most of the cerebrum
* vertebral arteries join once within the skull to form the basilar artery
* serves the brain stem and cerebellum
* posterior cerebral arteries form from the division of the basilar artery
* supply the posterior cerebrum
* anterior and posterior blood supplies are untied by small communicating arterial branches

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result- complete circle of connecting BVs- called cerebral arterial circle OR circle of Willis

hepatic portal circulation

formed by veins draining the digestive organs, spleen, and pancreas

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empties into the hepatic portal vein

hepatic portal vein

carries blood to the liver where it is processed before returning to the systemic circulation