Module 16: Heart and Blood Vessels Flashcards
the heart lies in a cavity called the
mediastinum
what is the mediastinum?
thoracic cavity minus pleural cavity (lungs and other associated structures)
the mediastinum includes:
- esophagus
- thymus
- great vessels of the heart
- heart
the mediastinum is located
posterior to the sternum and anterior to the vertebral columns
membrane that protects the heart is called
the pericardium
define echocardiography:
ultrasound of the heart and shows both cardiac anatomy and function
TEE
transesophageal echocardiography
what is transesophageal cardiography?
by placing a transducer in the esophagus, physicians can get a picture of the heart that is unobstructed by tissues that limit conventional echocardiography
function of the pericardium is to
surround and protect the heart
the pericardium consists of what 2 layers?
- deeper serous pericardium
- outermost fibrous pericardium
the serous pericardium consists of what 2 layers?
- visceral layer (deeper and synonymous with epicardium)
- parietal layer (fused to fibrous pericardium)
a tough, dense connective tissue that prevents the heart from over expanding and anchors it to the mediastinum.
fibrous pericardium
what is pericardial effusion?
an accumulation of excess fluid in this space
why would a pericardial effusion occur?
- infections
- trauma
- myocardial infarction
when does a pericardial effusion become life threatening and what is it called?
- when the excess fluid creates enough pressure that it prevents the heart from pumping
- cardiac tamponade
cardiac tamponade is
excess pericardial fluid or leaking blood that keeps the heart from pumping blood
where is pericardial fluid found?
within the pericardial cavity between the visceral and parietal layers of the serous pericardium
how many chambers are found within the heart?
4 consisting of two atria (superior) and two ventricles (inferior)
collective function of atria
receiving/holding chambers for blood
collective function of ventricles
pumping chambers for blood to the lungs and body
this chamber receives deoxygenated blood from the body
right atrium
this chamber receives oxygenated blood from the lungs
left atrium
this chamber receives blood from the right atrium. Its job is to pump deoxygenated blood out to the lungs.
right ventricle
this chamber receives oxygenated blood from the left atrium. its job is to pump oxygenated blood out to the body
left ventricle
how many valves does the heart have and what are they?
4
- tricuspid valve
- pulmonary valve
- mitral (bicuspid) valve
- aortic valve
how do these valves operate?
in pairs
- AV valves (tricuspid and bicuspid) open together
- outflow valves (pulmonary and aortic) open together
AV stands for
atrioventricular
these valves control the flow of blood between the atria and the ventricles
atrioventricular valves (AV)
valve found between the right atrium and right ventricle
right atrioventricular valve (AV) or tricuspid valve
valve found between the left atrium and left ventricle
left atrioventricular valve (AV) bicuspid valve, or mitral valve.
these valves control the flow of blood leaving the heart from the ventricles. these valves are sometimes referred to as ‘‘semilunar’’ due to their shape
outflow valves
this valve regulates blood flow from the right ventricle to the pulmonary trunk (out to the pulmonary circulation)
pulmonary valve
this valve regulates blood flow from the left ventricles to the aorta (out to the systemic circulation)
aortic valve
this great vessel carries deoxygenated blood to the lungs
pulmonary trunk
the pulmonary trunk further divides into the
right and left pulmonary arteries
they are named arteries because they do what?
lead blood away from the heart
this great vessel carries oxygenated blood from the lungs
pulmonary vein
they are named veins because they do what?
lead back to the heart
this great vessel takes blood away from the heart to body
aorta
the aorta consists of what 3 portions?
- ascending
- arch
- descending
these great vessels carry blood from body back to the heart
venae cavae
the venae cavae consist of
- superior vena cava (for body above heart)
- inferior vena cava (for body below heart)
largest artery of the body
aorta
valvular stenosis
valves that are too stiff and don’t open properly
valvular incompetence
valves that are too floppy and leak
valvular incompetence commonly leads to
valvular regurgitation
valvular regurgitation is
when ventricular pressure increases, blood leaks in wrong direction out of wrong (closed) valve
most common valvular heart disease
mitral valve prolapse
-often genetic and is more common in women than men
imaging studies such as a ______ or an ______ can help diagnose valvular disorders
doppler ultrasound, MRI
turbulent blood causes
abnormal sounds
vegetations
bacterial growth on heart valves
vegetations can lead to
- incompetent valves
- sepsis
vegetations may break off and become
emboli (which may lodge in blood vessels restricting blood flow)
cause of vegetations
endocarditis
special cells that consist of 1% of the hearts cells
autorhythmicity cells
the action potential of a cardiac autorhythmic cell consists of what 3 ions?
- sodium (Na+)
- potassium (K+)
- calcium (Ca++)
the autorhythmic cell never rests so it does not have a resting membrane potential
FREEBEE ;)
explain the 3 steps of autorhythmicity
- Na+ channels open causing the membrane to “drift” towards the threshold
- After threshold is hit, Ca++ channels open causing depolarization of the cell membrane
K+ leak channels close - K+ channels open causing depolarization of the cell membrane
an increase in K+ does what to the heart?
slows it down
an increase in Na+ does what to the heart?
blocks Ca++ from entering the cells, slowing down the heart
moderate increase in Ca++ does what to the heart?
speeds it up and strengthens it
the three phases of cardiac muscle cell action potential
- Depolarization
- Plateau
- Repolarization
what happens during the depolarization phase of cardiac muscle action potential?
-when an action potential is triggered, voltage gated fast Na+ channels open which quickly leads to depolarization of a cell.
what is the resting potential of contractile muscle cells
-90mv
what happens during the plateau phase of cardiac muscle action potential?
- voltage gated channels slow ca++ channels in the sarcolemma open
- Ca++ flows into the cytosol triggering further release of Ca++ from the sarcoplasmic reticulum
- Ca++ ions bind to troponin allowing actin and myosin to bind, sliding past each other and causing contraction.
what happens during the repolarization phase of cardiac muscle action potential?
- voltage gated K+ channels open causing K+ to rush out of the cell
- Ca++ channels close at the same time. this restores the negative membrane potential
instead of 3 msec, cardiac muscle cells action potential lasts
300 msec
refractory period
time during which a second action potential cannot be triggered
EKG lasts how long?
about the same time as cardiac muscle action potential at about 300 msec
QRS is
rapid depolarization as ventricular muscle cells open Na+ channels
QT interval is
the time Ca++ channels are open during the plateau of an action potential and repolarization
T is
the depolarization from an influx of K+
when measuring blood pressure the top number in the reading reflects
the systolic pressure
what is the systolic pressure?
pressure of the left ventricle before and after systole
when measuring blood pressure the bottom number in the reading reflects
the diastolic pressure
what is the diastolic pressure?
pressure when the left ventricle rests
normal BP
120/80
a blood reading of 120/80 reflects
- systolic pressure of 120mmHg
- diastolic pressure of 80mmHg
pulmonary BP is a result of
right ventricular function (not easily measured)
heart rate
- beats per minute (bpm)
- number of cardiac cycles per minute
end-diastolic volume
- at diastole, ventricles fill to about 120 ml
- ventricular volume at diastole is the EDV
end-systolic volume
- amount remaining in ventricles after contraction
- about 50 ml
stroke volume output
- at systole, volume of ventricles decrease by amount pumped out
- end-diastolic volume - end-systolic volume = about 70 ml
- this is stroke volume output
ejection fraction
- stroke volume output divided by end-diastolic volume
- percentage of ventricle emptied at systole
- usually 60% (70ml/120ml)
- lower ejection fraction means blood is pooling in heart and may clot
- also, heart isn’t effectively pumping (congestive heart failure)
cardiac output
-quantity of blood pumped into aorta each minute
frank-starling mechanism
the more the ventricles fill, the more forcefully they contract
maximum heart rate is about
220 minus age
connect arterial blood flow to venous return
capillaries
precapillary sphincters are
smooth muscle cuffs that regulate blood flow through capillary bed
what are the three types of capillaries found in the body?
- continuous
- fenestrated
- sinusoids
continuous capillaries
- endothelial cells that form a continuous tube, interrupted only by small intercellular clefts
- passage of substances by pinocytosis
fenestrated capillaries
- holes + basement membrane allows passage of substances
- found in the kidneys, villi of the small intestine and endocrine glands
sinusoids
- open spaces between cells and in basement membrane
- substances easily pass into and out of these substances
- found in the liver and the spleen
autoregulation is due to
low oxygen in tissues
when precapillary sphincters are relaxed….
blood flows through capillary bed
when precapillary sphincters are contracted…
blood bypasses capillary bed and takes thoroughfare channel
autoregulation
ability of capillaries to regulate blood flow
blood flow
volume of blood that flows through any tissue in a given time period
blood that flows too slowly is prone to
clots
recall ohm’s law
V is voltage, analogous to pressure
I is current, analogous to flow rate
R is resistance
if pressure increases, blood flow _________
increases
if resistance increases, blood blow _________
decreases
Name the layers of the heart wall from deep to superficial
Endocardium
Myocardium
Epicardium
Pericardium
Simple squamous epithelium lining the inside of the heart
- can develop chronic infections
Endocardium
The heart muscle proper. 95% of the heart and is responsible for the pumping action
Myocardium
Epithelium lining the outside of heart = visceral labor of serous pericardium (slippery covering)
Epicardium
- parietal labor of serous pericardium
- fibrous pericardium
Pericardium
Cardiac muscle Tissue
- striated
- shorter, branch, & have 1 or 2 centrally-located nuclei
- intercalated discs
- > amt. & larger mitochondria than skeletal muscle (for energy)
Function of Intercalated discs
For structural strength
Function of gap junction
To synchronize muscle cell contraction (allow muscle action potentials to travel between fibers)
Chordae tendinae
Chordlike tendons that are anchored to papillary muscles
Function of R ventricle
Pumps short distance and against low pressure to lungs
Function of L ventricle
Pumps long distance and against large pressure to body (very thick compared to Right)
Functions of valves
- don’t actively open; they’re pushed open by ⬆️ pressure
- chordae tendinae help keep valves in place
- mainly act as “back flow preventers”
Pattern of Blood Flow (1-10)
1) blood from superior and inferior vena cava enters R atrium
2) blood flows from R atrium to R ventricle via tricuspid valve tricuspid & mitral valves open
3) blood pumped from R ventricle to pulmonary artery (trunk) via pulmonary valve pulmonary & aortic valves open
4) blood oxygenated in pulmonary capillaries of lungs
5) blood returns to heart via pulmonary veins
6) oxygenated blood from lungs returns to L atrium
7) blood flows through mitral (bicuspid) valves into L ventricle tricuspid & mitral valves open
8) blood is pumped through aortic valve into aorta pulmonary & aortic valves open
9) blood distributed to body through branches off aorta and other vessels into capillaries
10) blood returns to heart via systemic veins and vena cava
When cardiac cells can fire regular rate action potentials without nervous stimulation or outside control
Autorythmicity
Sinoatrial node
Heart’s pacemaker(fires action potentials about 100x per minute), cardiomycocytes
Located near Coronary sinus and R atrium
A cluster of special heart muscle cells at the base of the heart
Cardiomycocytes
Atrioventricular node
“backup/ectopic pacemaker”
Located near junction of L atrium and R ventricle
Atrioventricular bundle of His
- leads from AV Node and through the interventricular septum
- splits into R & L bundle branches
Perkins fibers
Large caliber, non-contractile cells conduct the electrical impulses to the cardiac muscle cells of the R & L ventricles
Where is the cardiovascular center located
The medulla
What do baroreceptors sense
Blood pressure
If blood pressure is too high, the ____________________________ responds to ______ the heart rate through the _____________.
Parasympathetic nervous system
slow down
Vagus nerve
If blood pressure is too low, the _________________________ responds to _________ the rate of the heart through _______________________.
Sympathetic nervous system
Speed up
Cardio-accelerator spinal nerves
Sympathetic in regard to innervation of the heart
- respond to norepinephrine and epinephrine release
- ⬆️ heart rate & stroke volume
• B1-adrenergic receptors
• B2-adrenergic receptors
Parasympathetic in regards to innervation of the heart
- responds to ACh release
- ⬇️ heart rate
• muscarinic (M2) receptors
P wave =
Atrial depolarization
P-Q wave =
Atrial “kick” fills ventricles
- amt. of time it takes for the atria to depolarize
QRS wave =
- ventricles depolarize
- atria repolarize
S-T segment =
Blood flows out, emptying ventricles
T wave =
Time from ventricular depolarization to Ventricular repolarization
Atrial fibrillation
Most common acute EKG abnormality
- almost normal QRS but missing P
Ventricular tachycardia
- ventricle depolarizes, but pumping action not effective
Ventricular fibrillation
disorganized electrical activity
- life threatening (blood not moving to lungs)
Systole
Contraction
Diastole
Relaxation
Cardiac cycle
- Diastole (entire heart relaxes, atria fill with blood)
- Atrial systole ( atria contract, atrial “kick”)
- Ventricular systole (powerful ventricular contraction sends blood from R ventricle to lungs and L ventricle to body)
Individual events of the cardiac cycle:
- Action potential starts at the SA node causing depolarization of atrium producing P wave
- (Atrial systole) atria contract
- (QRS wave) actions potential pauses at AV node. Then spreads to ventricles = depolarization
- contraction of ventricles. Begins shortly after QRS complex appears and continues during S-T segment
- (T wave) repolarization of ventricles
- Ventricular diastole begins shortly after T wave begins
2 loudest heart sounds
S1: low pitched “lubb”
• AV valves closing, outflow(semilunar) valves open
S2: higher pitched “dub”
• outflow valves close, AC valves open
AV valves
Tricuspid & mitral
Outflow (Semilunar) valves
Pulmonary & aortic
Listening to sounds of the heart
Auscultation
Structure of a Blood Vessel
Lumen
Tunica interna
Tunica media
Tunica externa
The opening of the vessel
Lumen
Forms the innermost layer of blood vessel and consists of a simple layer of squamous epithelium connected to a basement membrane
Tunica interna
- Muscular tissue & connective tissue
* vasoconstriction and vasodilation in arteries controls blood flow and blood pressure
Tunica media
- elastic and collagen fibers
* sympathetic nerves and tiny blood vessels (Vaso vasorum) in larger vessels
Tunica externa
- smooth muscle layer thickened
- lumen diameter can change depending on muscle tone
Artery
- thin or absent smooth muscle layer
- lumen diameter does not change
- valves prevent backflow
Veins
Elastic arteries
- large diameter
- thin walls
- able to withstand high pressure
Muscular (distributing) arteries
- medium diameter
- more smooth muscle
- fewer elastic fibers
Arterioles
- tiny arteries
- these adjust the rate of blood flow to the capillaries
Capillaries
Site of nutrient and gas exchange
Venules
Small veins
- valves become incompetent and “floppy”
- backflow of blood results
- pooling occurs: venous stasis
- increase risk of clots forming
Varicose veins
Capillary exchange
- Capillaries are specializes for exchange of materials
- Filtration: O2, glucose, other nutrients must be delivered to cells
- Reabsorption: CO2, acid, urea, other wastes must be carried away to be excreted
Starling’s Law of the Capillary
- hydrostatic pressure
- this is opposed by the concentration force of water trying to dilute out higher concentration of dilutes in blood (interstitial fluid osmotic pressure)
- Balance between these forces = Starling Forces –> equation is Starling’s Law of the Capillary
- interstitial fluid osmotic pressure is about the same throughout capillary, but hydrostatic pressure drops
- capillary delivers nutrients on the Arterioles side, and picks up wasted on the Venule side
Hydrostatic pressure
Delivery of nutrients to tissue depends on blood pressure at capillary
Blood hydrostatic pressure
About 33mmHg
Where does Interstitial fluid osmotic pressure come from and what does it do
The presence of plasma proteins that cannot cross the capillary….it opposes blood hydrostatic pressure but it smaller at 25 mmHg
Vasoconstrictors
Norepinephrine Epinephrine ADH Angiotensin ll Endothelium-derived factors • released in low blood flow
Vasodilator a
Atrial natriuretic peptide Nitric oxide Inflammatory mediators • histamine (also increases capillary permeability) • prostacyclin • kinins Ethanol •inhibits ADG & vasomotor center
Describe changes in arterial pressure throughout the circulation
Blood pressure in highest in the aorta as it leaves the heady. As blood travels through the systemic circulation, it gets farther and farther away from the pump and pressure drops.
Describe changes in venous pressure throughout the circulation
When blood gets to the venous system, BP in very low. Blood helps muscles act as help
The closing of valves in the veins prevents the blood from running backwards. Changes in pressure during inhalation also draws venous blood back up towards the heart
The response to an increase in blood pressure (detected by stretching of baroreceptors):
- Nerves from the medulla increase parasympathetic stimulation by the vagus nerve and decrease sympathetic stimulation
- Rate of impulses on sympathetic neurons to the vessels slow, causing vasodilation
= ⬇️ blood pressure
Response when blood pressure is low:
Baroreceptors stretch less and send impulses at slower rate
- The cardiovascular center decreases parasympathetic stimulation and increases sympathetic stimulation
- Adrenal medulla increases secretion of epinephrine and norepinephrine
- Blood vessels constrict. Blood pressure increases as a result
What do chemoreceptors do
Sense the chemical composition of the blood. Detect pH, O2, CO2, & H+ levels
Located: close to baroreceptors of carotid bodies and aorta
Carotid artery
- splits into internal carotid (to brain) & external carotid (to face)
- structure called carotid body at this point
Response to conditions of hypoxia, acidosis, or hypercaonia
An increase in sympathetic stimulation to Arterioles and veins causing vasoconstriction and increasing blood pressure
About ____ % of blood is in the venous system
60%
Function of venous reserve
If massive blood loss occurs, baroreceptors of carotid sinus signal emergency
•nervous system can mobilize about 1 L blood from organs with venous reserves
- blood reservoirs
{systemic veins and venules}
{e.g. Spleen and liver}
Most of the blood draining from the head pass through what three pairs of veins
Internal jugular
External jugular
Vertebral veins
The right and left ______ pass inferiorly on either side of the neck, then join with the subclavian veins to form the right and left _______________.
Internal jugular, brachiocephalic veins
________________ are superficial veins that run down the lateral sides of the head. They empty into the subclavian veins.
External jugular veins
_____________ originate in the occipital area of the brain. They descend through the foramina of the cervical vertebrae amp tying into the brachiocephalic veins of the neck. The brachiocephalic veins empty into the __________________
Vertebral veins
Superior vena cava
Most common site of venipuncture
Right median cubitak veins
Cephalic V.
Lateral
Basilic V.
Medial
The paired brachial veins drain:
Forearms
Elbow joint
Arms
Humerus
…pass superiorly and join with the basilica veins to join the axillary veins
The _________ and __________ veins are the principle veins draining blood from the upper limbs
Basilic
Cephalic
Cephalic veins
Run superficial and on let weak sides of limbs
Basilic veins
Deep, running in medial sides of limbs
Anterior to he elbow, the basilic veins drains into the ___________________ which drains the forearms. (these are preferred veins for a venipuncture)
Median cubital veins
The cubital veins drain into the ___________ which in turn empty into the __________.
Axillary veins
Subclavian veins
The internal and external iliac veins join together to form the ____________, which drains the pelvis, external genitals, and lower limbs.
Common iliac vein
The paired common Iliad veins empty into the __________
Inferior vena cava
Veins draining the digestive organs lead to the _____________ which supplies the live with blood to be filtered
Hepatic portal veins
The ___________ also join the inferior vena cava brining filtered blood back to the systemic circulation
Renal veins
The _______________ are the longest veins in the body traveling from the foot to the groin
Great saphenous veins s
The ____________ drain the knee joint joints
Popliteal veins drain the knee joints
The ___________ are continuous if the popliteal veins
Femoral veins
Systemic circulation
oxygenated blood in L atrium enters the L ventricle through the L AV valve ➡️ L ventricle sends oxygenated blood out through the aorta and to the body ➡️ at the capillaries oxygen diffuses to the cells and CO2 diffuses to the blood ➡️ blood returns to R atrium of the heart through the inferior and superior vena cava
Pulmonary circuit
Carries deoxygenated blood from the R ventricle to the alveoli within the lungs and returns oxygenated blood from the alveoli to the L atrium ➡️ blood leaves the R ventricle through the pulmonary trunk ➡️ branches into the R and L pulmonary arteries ➡️ oxygenated blood from lungs return through pulmonary veins to L atrium
Lymphatic drainage
Lymphatic capillaries are filtered through lymph nodes into lymphatic vessels ➡️ all lymphatic vessels eventually anastomose into lymphatic duct ➡️ lymphatic duct drains into venous circulation at subclavian V.
Look at Ohm’s Law on page 774 because im lazy
FREEBEE
N=
blood viscosity
L=
length of all blood vessels in the body
Prehypertension
at risk of developing hypertension
systolic pressure = 121-39
diastolic pressure = 81-89
Hypotension
low blood pressure that is too low to adequately deliver O2 and nutrients to vital organs.
atherosclerosis leads to hypertension in two ways
- decrease in elasticity of arteries
- decrease in diameter of arteries
