CV Week 2 Flashcards
_________ is located in the hollow organs of the body and all vasculature except for capillaries and endothelial cells
Smooth muscle
Describe structures that have smooth muscle
trachea and airways, vasculature, bladder, female reproductive organs, epididymis and vas deferences, musculature through GI tract, lymphatic vasculature
True or false - Because smooth muscle is responsible in a diverse group of organs, it requires a diverse range of regulatory mechanisms to perform specific functions
TRUE
In __________, smooth muscle cells all behave independently. Few gap junctions are found in these types of cells because there is no great need to electrically couple.
Multi-unit
In __________, smooth muscles behave as one unit which is accomplished by having many gap junctions interconnecting cells.
Single unit
Describe body structures that contain
a) multiunit smooth muscle cells
b) single unit smooth muscle cells
a) airways, vasculature, neural regulation
b) GI tract
_________ smooth muscle tends to be multiunit, whereas _________ smooth muscle tends to be single-unit
Tonically active, rhythmically active
Describe how ADH regulates smooth muscle
ADH is released by posterior pituitary and causes vasoconstriction of smooth muscle (and increased water reabsorption of the kidney)
_________ cause contraction, proliferation and remodeling of blood vessels
Inflammatory mediators
Nitric oxide is an example of ______________. It is produced in the immediate environment of the muscle and causes vasodilation of the blood vessels.
Humoral or paracrine signaling
Describe key differences between smooth muscle and skeletal muscle
Myofilaments in skeletal muscle are more highly ordered and produce bands whereas actin and myosin filaments are arranged differently. Smooth muscle contains dense bodies. Smooth muscles also contract more slowly than skeletal muscle.
Why do smooth muscle cells contract more slowly than skeletal muscle?
Cross bridge attachment.detachment is much slower thus rate of contraction is much slower.
True/False - although smooth muscle cells contract more slowly than skeletal muscle, smooth muscle cells can achieve equivalent (or greater) peak contractions
true
How does slower cross-bridge cycling in smooth muscle affect energy efficiency?
Since cycling of cross-bridges is slower, energy expenditure decreases. This energy efficiency is particularly important to generate sustained contractions over minutes or hours (ie tone)
Describe the different types of myogenic activity (intrinsic to the musculature)
phasic with tone (anal sphincter), phasic (colon), tonic (some blood vessels)
Describe the steps in activating cross-bridge cycling in smooth muscle.
1) Myosin binds to actin filament and an inorganic phosphate is released
2) Power stroke where actin gets pulled towards middle of sarcomere
3) Rigor (myosin in low energy form). ADP is released and new ATP binds to myosin head.
4) Myosin unbinds from actin. ATP is hydrolyzed.
5) Cocking of myosin head (myosin in high energy form) and ready to bind again.
Describe MLCK’s role in cross-bridge cycling
MLCK phosphorylates MLC20 (myosin) and facilitates its binding to actin. This facilitates cross-bridge cycling.
Describe MLCP’s role in cross-bridge cycling
MLCP dephosphorylates MLC20 and reduces cross-bridge cycling –> muscle relaxation
What is MLCP activity regulated by?
pathways that in effect regulate Ca++ sensitivity of contractile apparatus
What determines the force and duration of contraction?
The balance between myosin phosphorylation and dephosphorylation; therefore, the balance btwn activity of MLCK and MLCP
How does Ca++ vary in when there are a) high MLCK levels; b) high MLCP levels
a) high MLCK - high Ca++; b) high MLCP - low Ca++
_________ (2) are examples of excitatory agonists that cause Ca++ sensitization and thus greater force by inhibiting MLCP
Rho Kinase and PKC
_________ (2) are examples of inhibitory agonists that reduce Ca++ sensitization and thus relax muscle, reducing the force by aggravating MLCP activity
cAMP and cAMP dependent mechanisms
What are three pharmacological agents that are excitatory agonists in regulation of contraction via pharmacochemical coupling?
Ach, norepinhephrine, substance P
What are two pharmacological agents that are inhibitory agonists in regulation of contraction via pharmacochemical coupling?
adenosine, vasoactive inhibitory peptide
How do ROCK and PKC inhibit MLCP activity and thus stimulate contraction?
ROCK phosphorylates MYPT1 subunit of MLCP and PKC via Ca++ and PLC-b mechanism phosphorylates CPI-17,(inhibitory proteins)
Smooth muscle cells contains transport proteins and organelle membranes that set and regulate membrane potential, generate excitable events and ___________________
Ca++ entry into and removal from the cytoplasm
Like other excitable cells, the PM has some level of permeability of each ion species present. The dominant membrane permeability in smooth muscle is due to ______________
K+ channels
RMP is smooth muscle is usually _________ mV
-40 to -80
_________ couple smooth muscle cells into an electrical syncytium and provide low electrical resistance pathways between cells
Gap junctions
Describe the structure of a gap junction.
Gap junction is contains numerous CONNEXONS which are channels assembled by six connexin proteins each that form the pore.
Glucose, glutamine, ADP, adenosine, and cAMP all have same ________ through connexins
permeability
What happens to connexons when they are attached to a damaged cell?
They close, can be regulated somewhat by Ca++ and pH
Name 4 types of K+ channels found in smooth muscle cells
voltage-dependent K+ channels (Kv), Ca++ activated K+ channels (BK), 1 transmembrane pore formign loop (Kit, Katp), and 2 transmembrane forming loops (K2p)
Ca++ entry (excitation) tends to be controlled by __________.
K+ channels, due to their importance in regulating membrane potential
________ are voltage-independent channels that are important for resting or basal K+ conductance. They contribute to the resting potential of the smooth muscle cells.
2 pore K+ channels (K2p)
High expression of _________ can reduce the tendency for smooth muscle cells to generate action potentials, making the muscle less excitable
Voltage-activated K+ channels
High abundance of ____________ can lead to rhythmic patterns of activity. These channels are also important for large amplitude hyperpolarizations produced by some inhibitory neurotransmitter as well as some other agonists.
Ca++ activated K+ channels (ekg BK)
____________ are active in negative voltage range and therefore also contribute to a more hyperpolarized cell. They also mediate responses to some inhibitory agonists.
Inward rectifiers (Kir)
Ca++ entry is controlled by _______ because these channels set or regulate membrane potential that determines Ca++ entry via __________
K+ channels, voltage dependent Ca++ channels
Depolarization induced activation of ____________ lead to Ca++ entry and contraction of smooth muscle
L-type Ca++ channels
________ is a Ca++ channel blocker. When added, the muscle relaxes because the __________ have been shut down.
Nifedipine, L-type Ca++ channels
Describe the two ways which Ca++ stimulates cell to depolarize
Ca++ activates Cl- to leave the cell –> depolarization and Ca++ activates non-selective cation channels –> depolarization
Describe how Ca++ causes hyperpolarization of the cell
Activates BK to transport Ca++ out
Describe Ca++’s role in CICR
Ca++ enters cell and stimulates Ca++ induced Ca++ release in sarcoplasmic reticulum
Describe how depolarization leads to contraction via Ca++ channels
depolarization causes an increase in Cav channels opening which increases Ca++ entry
Describe how hyperpolarization leads to decreased contraction via Ca++ channels
Decrease in open Cav channels which leads to decreased Ca++ entry and therefore decreased contraction
There are three major mechanisms that reduce Ca++ and that relaxation of smooth muscle depends on. What are they?
ATP-driven SR Ca++ pump, AT driven PM Ca++ pump, and Na/Ca exchange (NCX, uses Na+ gradient).
The more minor mechanisms are Ca++ binding molecules in cytoplasm and active Ca++ transport in mitochondria.
_______ is a short-acting gas and free radical whose unpaired electrons cause this chemical to be highly chemically reactive
Nitric Oxide
The biological actions of nitric oxide are rapidly terminated due to what? This makes this compound short-acting. It must be synthesized on demand.
Spontaneous oxidation to NO2 and NO3 resulting in a bio half life of around 3-5 seconds.
Nitric oxide is highly ______ so its post-junctional effector proteins are typically within the cell.
lipophilic
True or false: NO can be synthesized by variety of different cell types
True
The highest levels of nitric oxide in the body are found in the _______
neurons
Describe how nitric oxide inhibits smooth muscle contraction.
Vasodilator binds receptor on endothelial cell which activates NOs. NO is produced from Arginine. NO rapidly diffuses across membranes to a smooth muscle cell. It binds guanylyl cyclase which increases cGMP concentration and leads to relaxation of the smooth muscle cell.
In the NO pathway, cGMP activates _____________ which then goes on to phosphorylate several proteins important in promoting vasodilation
cGMP dependent protein kinase (PKG)
How do proteins phosphorylated by PKG promote vasodilation? (3 ways)
Proteins inhibit Ca++ release from IP3 receptors; proteins inhibit activation of L-type Ca++ channels; proteins increase Ca++ uptake by SR. These three mechanisms all lead to more highly activated MLCP (Ca++ desensitization)
What are the lateral leads?
I, V5, V6, AVL
What are the inferior leads?
Lead II, Lead III, avF
What are the anterior or septal leads?
V1-V4
How would you determine that rhythm is in normal sinus?
Upright P wave in inferior leads (lead II, lead III, aVF) [biphasic wave in lead VI - in textbooks]
How would you determine if there is a left axis deviation?
R wave in lead I is pointing upward (+) and R wave in lead II is pointing downward (-) (left each other)
How would you determine if there is right axis deviation?
R wave in lead I is pointing downward (-) and R wave in lead II is pointing upward (+) (right at each other)
How long is a normal PR interval?
less than 200 msec or 1 big box
How long is a normal QRS?
less than 120 msec or 3 little boxes
How long is a normal QTc?
Corrected for heart rate, should be 1/2 of R-R interval, <450 msec or 2.5 big boxes
If there is no correlation between the P wave and QRS and PR interval varies BUT P-P intervals and R-R intervals are consistent, what condition does this indicate?
3rd degree heart block
If the PR interval gets progressively longer until a QRS is dropped, what condition does this indicate?
2nd degree heart block, mobitz type I
If the PR interval is consistently longer than 200 msec (one big box), what condition does this indicate?
1st degree heart block
If the PR interval is consistent but a QRS is dropped randomly, what condition does this indicate?
2nd degree heart block, mobitz type II
The ____ is ALWAYS the first downward deflection in the QRS complex. If there is no downward deflection, then it doesn’t exist
Q wave
Why is a prolonged QTc medically significant?
If ventricles attempt to depolarize or contract on top of a Q wave, this leads to serious dysrhythmias such as V-fib and V-tach
What happens in right atrial enlargement?
right atrial depolarization lasts longer than normal and its waveform extends to end of left atrial depolarization (uneven double hump with taller 1st hump). P wave is taller than normal although width remains unchanged.
What happens in left atrial enlargement?
left atrial depolarization lasts longer. Amplitude is unchanged. Height remains same but duration is longer than 120 msec (3 little boxes). NOTCHED WAVE (“p mitrale”) near peak in lead II
What does an inverted T wave indicate?
ischemia
What does a spiked T wave indicate?
hyperkalemia
_______ are wide, random QRS complexes that usually come in early and can be unifocal or multifocal
Premature ventricular complexes
In _______ every other beat is a PVC whereas in _______ every 3rd beat is a PVC
bigeminy, trigeminy
What varies in a sinus arrhythmia?
R-R intervals
In a ____________ the heart beat happens sooner than expected. P waves are present and QRS complex is no different than baseline.
premature atrial complexes
In _________ there is an irregularly irregular rhythm and ___________ vary without any pattern. There is also an absence of _______ . Atrial HR can run 400-500 bpm.
atrial fibrillation, R-R intervals, P waves
In a _________, P wave is often inverted (esp in lead II) but may be under or after QRS and the heart rate is slow.
junctional rhythm
What differentiates between high junctional rhythm (stable) and low junctional rhythm (unstable)
Narrow QRS suggests stable (high) whereas wide QRS suggests unstable (low)
In __________ there is a narrow QRS (less than 120 ms or 3 small boxes) and heart rate of over 100 bpm. If there is a wide QRS, what is this called?
supraventricular tachycardia; SVT with aberrancy (typical in younger patients)
_________ is a wide complex tachycardia that is typically in older patients with previous myocardial infarction
ventricular tachycardia
In __________, there are no QRS complexes. This represents a chaotic and mechanical cardiac arrest.
ventricular fibrillation
A ___________ is can be seen in leads I, II, AVL, V1-V6 and represents a previous MI. In which leads does this deflection not represent pathology?
pathological Q wave, not pathology in leads III and AVR.
______________ is a reentry tachyarrhythmia via accessory pathway.
Wolf-Parkinson White
What accessory pathway is usually seen in WPW?
“Bundle of Kent” located between atria and ventricle on side. This electrical signal goes through without delay in AV node and meets the normal signal in ventricular purkinje.
What is diagnostic for WPW?
PR less than 125 ms (3 small boxes) and at least one delta wave.
How does WPW cause tachyarrhythmia (2 ways)
Narrow complex - the abnormal signal returns and depolarizes AV node, causing it to fire before the SA node.
Wide complex - abnormal signal hits AV node during its refractory period. Will pass through all the way around and come back to AV node in retrograde fashion.
What are common symptoms of WPW?
unexplained syncope and palpitations infrequently. Normal risk not high except if there’s abnormal pathways.
Drugs such as digoxin, Beta-blockers, verapanil, and adenosine will make WPW worse. Why?
Work mainly on AV node not on accessory pathway
What drug and surgical treatments are used for WPW?
Procanamide and Amiodarone. Surgical catheter ablation to damage accessory pathway.
What are the most common congenital defects?
Heart followed by genital/urinary tract
Describe the pathway of cardiac progenitor cells to the mesoderm
Cardiac progenitor cells form in epiblast then migrate in cranial –> caudal order through the primitive streak to the SPHLANCNIC LATERAL PLATE MESODERM
Where do prospective myoblasts and hemangioblats reside?
in the SPHLANCNIC MESODERM in front of the neural plate and on each side of th emebryo
In formation of the heart tube, angiogenic cell clusters initially coalesce to form ______________
right and left endocardial tubes [ endothelial heart tubes ]
After the embryo folds ________ and __________, the endocardial tubes fuse via ________ to form the heart tube
cardiocaudally, laterally, programmed cell death
Describe the four layers of the primitive heart from inside to outside
endocardium, cardiac jelly, myocardium, epicardium (outside covering of the tube)
The cardiac jelly is a thick, acellular material made by ____________
myocardium
In the epicardium, _______ migrates from the septum transversum to form the ____________
mesothelium, coronary arteries
On day 18, the endocardial tubes and dorsal aortae are formed between what two layers?
endoderm and sphlancnic mesoderm
On day 22, the embryo is in the __________ and fusion occurs only the ______ region of the horseshoe shaped heart tube
8 somite stage, caudal
What structures rise from the crescent portion of the horseshoe shaped heart tube?
outflow tract and most of ventricular region
In 22-day embryo, _____________ drain the yolk sac
vitelline veins
In 22-day embryo, __________ carry O2 from the placenta
umbilical veins
In 22-day embryo, _______________ drain body wall and head
common cardinal vein
True or false: The inflow and outflow tracts are connected to the heart tube before any cardiac folding takes place
True
Around day 23, the _______ begins to form from a series of expansions, constrictions and fold
cardiac loop
What are the four initial dilations of the heart tube?
sinus venosus, primitive atrium, primitive ventricle, bulbus cordis
What two features of the heart does the cardiac loop create?
1) normal position of heart chambers; 2) changes a single circuit system into an asymmetrical circuit system with pulmonary and systemic circulations
At day 24, remodeling of the _______ begins with a shift to the right of venous return
sinus venosus
What does the right vitelline vein give rise to?
inferior vena cava
What does the right anterior cardinal vein give rise to?
superior vena cava
What does the left sinus horn give rise to?
coronary sinus and oblique vein of the left atrium
The right sinus horn blends into the right posterior wall of the right atrium to become the smooth area _____________
sinus venarum
What three vessels open into sinus venarum?
THINK RIGHT ATRIUM. Inferior vena cava, superior vena cava, coronary sinus
The sinus venarum contains the ___________ which act as conducting fiber tract from SA node to AV node
crista terminalis
_________ are found in the cardiac jelly where they are described as “swellings”
endocardial cushions
What germ tissue are endocardial cushions derived from?
sphlancnic mesoderm
The sphlancnic mesoderm (endocardial cushions) and __________ in the conotruncal area play a role in formation of the _____________
neural crest cells, septa and valves
Endocardial cushions are important because they play a role in __________
cardiac defects
The primitive atrium is partitioned between the right and left _________
endocardial cushions
During partitioning of the primitive atrium, a thin membranous septum called the __________ because the right and left endocardial cushions
septum primum
After the formation of the septum primum, programmed cell death forms the ________
ostium secundium
What is the role of the ostium secundium?
Maintains the right to left shunt bypassing the pulmonary circulation
What thick muscular septum forms to the right of the septum primum?
Septum secundum
The ________ forms in the septum secundum which maintains the right to left shunt
Foramen ovale
When does the foramen ovale close?
immediately after birth
At birth, closure of the foramen ovale is functiona. Describe what this means in terms of atrial pressure.
At birth, there is a decrease in right atrial P from occlusion of placental circulation and increase in left atrial pressure due to increased pulmonary venous return (USING LUNGS)
When does the anatomical closure of the foramen ovale occur? What two structures fuse?
Occurs at 3 months, septum primum and septum secundum fuse
Incomplete anatomical fusion of septum primum and septum secundum causes ____________. This is present in 25% of the population and clinically usually of no importance.
probe patency of foramen ovale
Defects in the ________ cause the most clinically significant atrial septal defects and are prevalent in females to males in a _____ ratio
ostium secundum, 2:1
The cor triloculare biventriculare is also known as the _______
common atrium
What four heart defects do endocardial cushions play a role in?
atrial septal defect, ventricular septal defect, transposition of the great vessels, tetralogy of fallot
Conotruncial cushions, which also contain neural crest cells, play a role in both heart and _________ defects
craniofacial
During partitioning of the atrioventricular canal, what do the four endocardial cushions form(3)
septum , bicuspid valve, tricuspid valve
During partitioning of the atrioventricular canal, what can go wrong (2)
persistent common atrioventricular canal and abnormal division of the canal
The truncoconal septa form from _________ that migrate from the hindbrain through pharyngeal arches ___, 4, and 6 and then invade the truncus arteriosus to form the septa.
neural crest cells, 3
During the fifth week, _____ ridges/swellings appear and go on to form the ________________ which divides the truncus into the aortic and pulmonary channels
truncal, aorticopulmonary septum
After formation of the truncal swellings, _____ swellings also form which give rise to the _________________
conal, outflow tracts of right and left ventricles
_________ contribute to both swellings to form connective tissue and smooth muscle of aorticopulmonary system
neural crest cells
During partitioning of the truncus arteriosus and the bulbus cordis, _______ lines up the correct outflow tract with the correct ventricle
spiraling
During partitioning of the truncus arteriosus and bulbus cordis, If neural crest cells were to be experimentally removed or blocked during their migration this would lead to ___________
persistent truncus arteriosus
If there is no aorticopulmonary septum formed, then there will be ________
persistent truncus arteriosus
If the aorticopulmonary septum does not spiral there will be ____________
transposition of the great vessels
If the aorticopulmonary septum is misaligned there will be ___________
tetralogy of fallot
Persistent truncus arteriosus is normally accompanied by __________
ventricular septal defect
In persistent truncus arteriosus, which great vessel gets more blood flow and why?
The pulmonary artery section receives more blood flow than the aorta section due to decreased pressure in the lungs compared to systemic circulation.
Describe the basic pathology of persistent truncus arteriosus.
In persistent truncus arteriosus, the great vessels do not separate and there is a VSD. Deoxygenated and oxygenated blood mix and go into body and lungs.
In persistent truncus arteriosus, since the pulmonary artery section receives more blood than aorta, what happens that leads to pulmonary HTN?
Too much blood in the lungs leads to fluid build up which makes it difficult to breathe. Blood vessels to the lungs become damaged. This makes it harder to pump blood into the lungs over time due to pulmonary HTN that develops.
Due to pulmonary HTN, more blood starts to go into the body then the lungs eventually in persistent truncus arteriosus. What occurs as a result?
Cyanosis worsens as blood with lower O2 travels to the body.
How is persistent truncus arteriosus treated?
corrective surgery needed within 6 months of life - closure of VSD and separation of great vessels
Infants with transposition of the great vessels can only survive after birth if they have one of which 3 defects?
patent ductus arteriosus, atrial septal defect, ventral septal defect - allows intermixing of the blood
If these defects are not present, how can they be surgically induced?
Cardiac catheterization (balloon atrial septostomy) may create large hole in the atrial septum or a patent ductus arteriosus can be clinically induced to remain open allowing blood flow btwn pulmonary artery and aorta
Describe the basic pathology of transposition of the great vessels.
The great vessels are switched so the aorta is connected to the right ventricle and the pulmonary trunk is connected to the left ventricle - therefore oxygenated blood going to lungs and deoxygenated blood going to systemic circulation - NOT COMPATIBLE WITH LIFE
During the arterial switch procedure, what remains attached to the aorta?
coronary arteries
Transposition of the great vessels is usually accompanied by an _____________
atrioseptal defect
______________ the most common cyanotic heart defect
teratology of fallot
Describe the basic pathology of teratology of fallot
The outflow tract openings fail to align with the ventricles. Right ventricular outflow (pulmonary artery) is blocked which causes pulmonary stenosis and an overriding aorta. A ventricular septal defect accompanies.
The ventricular septal defect and pulmonary stenosis in TOF leads to high pressure in the ___________ which results in ____________
right ventricle, right ventricular hypertrophy
In extreme situations, right ventricular outflow tract is completely blocked, which leads to teratology of fallot and _________
pulmonary artesia
Children with teratology of fallot are at risk of having what kinds of spells??
Hypercyanotic spells due to spasm of infindibular region (below pulm vave) and/or sudden increased pulmonary vascular resistance which produces a sudden decrease in amount of blood getting to lungs.
What kind of shunt develops in teratology of fallot? How does this lead to acidosis?
Right to left shunt which means more deoxygenated blood is going into systemic circulation. This further increases pulmonary vascular resistance which leads to acidosis.
Older children learn to prevent or alleviate symptoms by squatting. What is squatting believes to do?
Squatting kinks the large arteries in the lower extremities which increases systemic vascular resistance and forces more blood across the pulmonary outflow tract.
What are the four components of teratology of fallot? Which is the primary problem?
Ventricular septal defect (VSD), pulmonary stenosis, overriding aorta, thickening of the right ventricle. VSD is primary problem.
During partitioning of the primitive ventricle, where does the muscular ventricular septum develop?
midline on floor of primitive ventricle
The __________ is located between the free edge of the muscular interventricular septum and fused AV cushions
interventricular foramen
Closure of the interventricular foramen via completion of the conus septum and outgrowth of tissue from the inferior endocardial cushion leads to formation of the ____________
membranous interventricular septum
In other words, membranous interventricular septum is formed when the proliferation of right and left ____________ combined with proliferation of inferior (AV) endocardial cushion closes the interventricular foramen.
right and left bulbar ridges (conus cushions)
_____ are the most common cardiac congenital defects, occurring in about 30% of cases
ventricular septal defects
What is the most common cause of ventricular septal defect?
membranous IV septum does not form
Single or multiple perforations in the ______________ can also cause ventricular septal defects
muscular interventricular septum
Describe the two mechanisms of no shunt (acyanotic) congenital heart defects
(1) anomaly of aortic arches, (2) coarctation of aorta
Describe three types of anomalies of aortic arches
right arch of aorta, double arch of aorta, retro-esophageal right subclavian artery
Describe the three mechanisms of left to right shunt (acyanotic) congenital heart defects
persistent ductus arteriosus, interatrial septal defects, interventricular septal defects
Describe the three mechanisms of right to left shunt (cyanotic) congenital heart defects
(1) complete transposition of the great vessels, (2) truncus arteriosus communis (persistent), (3) teratology of fallot
The smooth portion of the left atrium houses the _______________
pulmonary veins
Remodeling of the vascular system generally occurs from ______ to ________ tracts
inflow, outflow
For the inflow tract, above the diaphragm, remodeling begins with a shift to right of venous return. This leads to formation of what 5 structures?
IVC, SVC, coronary sinus, oblique vein of left atrium, sinus venarum
For the inflow tract, below the diaphragm, the vitelline system gives rise to what structures? (3)
liver sinusoids (incl ductus venosus), the portal system (portal vein, SMV, IMV) and a portion of the inferior vena cava.
For the inflow tract, below the diaphragm, what occurs to the right and left umbilical veins?
The right umbilical vein disappear and the left umbilical veins anastomoses with the ductus venosus in the liver.
Anastomosis of the left umbilical vein with the ductus venosus in the liver results in what?
Shunting of oxygenated placenta blood into inferior vena cava and right side of heart
The _________ form a portal system that drains the blood from the foregut, midgut, and upper part of anorectal canal
right and left vitelline veins
For the outflow tract, ventrally, the aortic arch arteries rise from the _________ through expansion of cranial end of the __________
aortic sac, truncus arteriosus
Dorsally, the aortic arches connect to left and right ______
dorsal aortae
What develops from aortic arches 3,4, and 6 (and R and L dorsal aortae)?
adult arterial system, ASYMMETRICAL arches
Aortic arch 6 remains on left side and goes on to form what?
pulmonary vessels and ductus arteriosus
What can maintain a patent ductus arteriosus if clinically indicated?
exogenous prostaglandins
Small pactent ductus arteriosuses can be closed via what?
prostaglandin inhibitors such as indomethacin or ibuprofen
What two main reasons necessitate closure of PDA?
(1) large size of ductus –> large volume of blood going into lungs can lead to overload –> heart enlargement then failure; (2) avoid risk of developing endocarditis
Development of endocarditis in ____ of patients with PDA will lead to an increased mortality of 50%
1/8
In fetal circulation, well oxygenated blood returns from the placenta via the ________
umbilical vein
In fetal circulation, what two pathways does blood travel in from placenta?
1/2 of blood passes through hepatic sinusoids whereas other half bypasses the liver and goes through the ductus venosus into the inferior vena cava
What are the two right to left shunts in fetal circulation?
(1) blood from right atrium goes through foramen ovale into left atrium; (2) the small amount of blood from right ventricles that enters the pulmonary trunk passes through ductus arteriosus into the aorta.
In fetal circulation, blood flows from right to left atria via foramen ovale and then into the ascending aorta. What tissues are best oxygenated this way?
head, neck, upper limbs
How is blood in placental circulation re-oxygenated?
Blood is returned via umbilical arteries to the placenta
At birth, what three shunts cease to function?
foramen ovale (interatrial), ductus arteriosus (inter great vessel) and ductus venosus (bypass lungs)
What causes the foramen ovale to close upon birth?
Aeration of the lungs provides a dramatic fall in vascular resistance. An increase in pulmonary blood flow leads to increased L atrial pressure above that in R atrium which closes foramen ovale.
Upon birth, what happens to the ductus arteriosus and ductus venosus?
constriction
What are the remnants of umbilical arteries upon birth?
internal iliac arteries and media umbilical ligaments
What are the remnants of the umbilical vein upon birth?
ligamentum teres of liver
What are the remnants of ductus venosus upon birth?
ligamenetum venosum
What are the remnants of the foramen ovale upon birth?
Fossa ovalis (becomes obliterated?)
Circulation is a __________ that features a branching pattern and blood flows through serial and parallel paths
closed circuit
True/False -In all cases blood flows through 2 capillary beds in series
false, sometimes blood flows through a single capillary bed and sometimes it flows through an arrangement of parallel and series paths
What pathway does blood from the right to the left heart take?
It can only take a single pathway, across a single capillary bed in the lungs.
Sometimes, in the normal human body, some deoxygenated blood (which should have gone to right heart) mixes with oxygenated blood bound to ______________
systemic arteries
_________ transport blood under high pressure, have rapid pulsatile blood flow and are densely innervated. These vessels have a strong muscular wall.
arteries
________ are the smallest branches of arteries.
Arterioles
Arterioles are major ______________ of whole peripheral circulation and have a ________ layer
resistance vessels, thick smooth muscle
Arterioles are ________ innervated and have a _________ layer
very densely, endothelial cell
Arterioles regulate blood flow to ________
capillary beds
Arterioles are considered “_______________” due to having the biggest P drop
stopcocks of circulation
In arterioles, how is basal tone established?
smooth muscle is partially contracted under normal conditions
True/False: Arterioles are the most significant point of control over peripheral resistance to flow
True
True/False: Arterioles outnumber any other type of artery
True
True/False: Arterioles are less muscular in proportion to their diameter
FALSE - arterioles are more muscular in proportion to their diameter
Arterioles are highly capable of changing their ______
radius
How is blood flow to the capillaries controlled?
via vasoconstriction and vasodilation
What is the difference between skeletal muscle and vascular smooth muscle in terms of tone?
Vascular smooth muscle has some tone without needing neural input.
The basal tone seen in smooth muscle comes from _________ and ________ factors
intrinsic, local
All types of smooth muscle cells exhibit _________ channels which are typically _______ which are activated by the cell’s membrane potential
voltage-dependent Ca++, L-type Ca++ channels
Cells that sit negative to ________ must be depolarized in order to be activated by L-type Ca++ channels
-60mV
Cells that are positive of -60mV have some ______ activation of L-type channels and therefore ______ Ca++ entry
tonic x2
True/False: Capillaries have smooth muscle
FALSE - CAPILLARIES DO NOT HAVE SMOOTH MUSCLE
Describe the features of capillary walls.
Very thin walls consisting of a single layer of endothelium permeable to small molecular substances.
Name three features of capillaries.
1) major exchange vessels, 2) largest total cross-sectional area, 3) low flow velocity
__________ are small vessels with thin walls that collect blood from capillaries and also participate in exchange
venules
What happens when blood enters venules from capillaries?
total cross-sectional area diminishes and thus the velocity of blood flow increases
Venules progressively merge to form larger _____ which transport blood _________
veins, back to heart
Veins are major ________ vessels and a major ______ reservoir.
capacitance (major collection and storage site for blood), controllable
Describe three features of veins
1) thin but muscular walls, 2) under low pressure, 3) densely innervated
About _____ of entire blood volume of body is in systemic circulation and about _____ is in heart and lungs
85, 15%
Describe the distribution of the blood in circulation
65% in veins, 13% in arteries, 7% in arterioles and capillaries
_________ is the total area of all vessels added together at each _____ in the circulatory stem
cross-sectional area, level
Blood velocity is measured in a __________ at each ______ in the circulatory system
single vessel, level
_________ markedly affects blood velocity
vessel radius/diameter
The highest velocity is found in the _____ which also has the lowest cross-sectional area
aorta
The lowest velocity is found in the _______ which has the highest cross-sectional area
capillaries
Veins have ____ velocity and ____ area
higher, lower
True/False: Capillaries have 1000x the cross sectional area of aorta
true
What is the formula for velocity of blood flow?
velocity is equal to blood flow divided by cross sectional area
Describe the relationship between velocity, blood flow and cross-sectional area
Velocity is proportional to blood flow and inversely proportional to cross-sectional area
Describe the three reasons why blood velocity decreases from aorta to capillaries
1) greater distance means more friction to reduce speed, 2) smaller radii of arterioles and capillaries offers more resistance, 3) farther from heart, total cross sectional area becomes greater and greater
Describe fluctuation of the arterial pressure in regards to pulsatile heart pumping
The arterial pressure in aorta is high because heart is pumping constantly. However, it is higher in the systolic phase than diastolic phase.
__________ is the force exerted by the blood against any unit area of the vessel wall
blood pressure
As blood flows through systemic circulation, pressure decreases progressively because of the _________
resistance to blood flow
Intravascular pressure stretches blood vessels in proportion to their _________
compliance
Largest decrease in pressure occurs across the _________ because they are the site of highest resistance
arterioles
What is pulse pressure?
the difference between peak arterial pressure of systole and peak arterial pressure of diastole
How is pulse pressure dampened over the course of the arterial tree? (2)
1) compliance of arterial walls, 2) resistance to flow as vessel diameter becomes smaller.
Due to the hydraulic filter effect, the flow through capillaries will be ________ thoughout the cardiac cycle
continuous
What is compliance?
the elasticity of vessel walls
True/false: Capillary blood flow is non-pulsatile
True - due to increasing dampening by vessel compliance and functional resistance of small arteries and arterioles
In Grave’s disease, in addition to hyperthyroidism and elevated basal metabolism, what changes are seen in arterioles?
Arteriolar vasodilation and reduced arteriolar resistance - causes a dampening effect on pulsatile arterial pressure which diminishes it. Pulsatile flow observed in capillaries of nail beds.
_________ is the lowest arterial pressure during the cardiac cycle
Diastolic P
The most important determinant of pulse pressure is __________
stroke volume.
The arterial pulse P gives valuable clues about a person’s pulse pressure, unless what?
arterial compliance is not normal
Describe the arterial pulse pressures and stroke volumes found in those with severe CHF and severe hemorrhage
small arterial pulse pressures because their stroke volumes are abnormally small
Describe the arterial pulse pressure and stroke volume found in those with aortic regurgitation
large stroke volume, increased arterial pulse P
Describe the stroke volumes in trained atheletes
Have high stroke volumes at rest because their HRs are usually low due to prolonged ventricular filling times
What are the two factors that dampens pulse P over the course of arterial wall tree?
compliance and resistance to flow as vessel diameter becomes smaller
______________ is the avg arterial pressure with respect to time
mean arterial pressure (MAP)
What is the formula for MAP?
=1/3 pulse pressure + diastole P; or (1/3 systolic-diastolic) + diastolic; or 1/3 systole + 2/3 diastolic
Describe why venous P tends to be low.
Veins have a high capacitance and can hold large volumes of blood and lower pressure.
True/False: atrial pressure is even lower than venous pressure
true
Atrial pressure can be estimated by the __________ [approximately equal]
pulmonary wedge pressure
True/false: Absolute pressure drives blood flow
FALSE - pressure gradient - blood flows from high P to low P
___________ is the quantity of the blood that passes a given point in circulation in a given period of time
blood flow
What is the formula for blood flow
Blood flow is equal to the pressure gradient divided by resistance. Also can be mean arterial pressure / resistance
Blood flows when?
pressure exceeds resistance
_____________ is the total quantity of blood that can be stored in a given portion of the circulation for each mmHg pressure rise
compliance
What is the formula for compliance/capacitance?
Compliance is equal to the volume divided by the pressure
True/False: Capacitance is much greater in arteries than veins
FALSE, much greater in veins
Capacitance/compliance is determined in large part by the relative proportion of __________ to __________ in the vessel wall
elastin fibers, smooth muscle and collagen
True/False: Aging decreases compliance
true. As a person ages, the arteries become stiffer and less distensible.
Artherosclerosis results from the deposition of tough, rigid _______ inside the vessel wall and around the atheroma. This increases stiffness and decreases the elasticity of the artery wall.
collagen
________ is the force that impedes blood through the system
resistance
What factors change the resistance of blood vessels? (3)
blood viscosity, blood vessel length, radius of the vessel
How is resistance in blood vessels calculated?
resistance is equal to 8blood viscosity * blood vessel length divided by piradius^4 (R = 8nl/pi*r^4)
What blood cells/proteins elevates blood viscosity the most? In that regard, what conditions elevate blood viscosity?
RBC count and albumin, polycythemia and dehydration
What decreases blood viscosity?
anemia and hypoproteinema –> increased blood flow
What declines with distance in terms of blood vessels?
pressure and flow
What is the most powerful influence over blood flow?
vessel radius - only significant way of controlled resistance - marked affects blood velocity
________ are changes in vessel radius
vasoreflexes
Smooth muscle in which blood vessel layer contracts during vasoconstriction?
tunica media
What is the major determinant of resistance in blood vessels and why?
Changes in the radius of vessels because the viscosity of blood or length of blood vessel cannot be easily changed from moment to moment
What is the relationship between blood flow and radius of vessel?
Blood flow is proportional to the 4th power of radius and therefore small changes in vessel radius cause large changes in flow (ml/min)
Inhibition of sympathetic activity ______ blood vessels and _____ blood flow whereas very strong sympathetic activity _____ blood vessels and _____ blood flow
dilates, increases, constricts, decreases (sometimes down to 0 despite high arterial P)
An increase in arterial pressure would cause what in regards to blood flow? Why?
a proportional increase in blood flow.
Why is blood flow at arterial pressure of 100mmHg usually 4-6X as a great as blood flow at 50 mmHg instead of 2X?
There is an effect of increased pressure on increased vascular diameter. Increase in arterial pressure increases the force that pushes blood through the vessel but also distends the vessels at the same time which decreases vascular resistance
What is the largest proportion of resistance contributed to?
a) arteries
b) arterioles
c) capillaries
arterioles
Describe blood flow and pressure for blood vessels in series.
Each blood vessel in series receives same total blood flow and as blood flows through the series of blood vessels, pressure decreases.
True or false: For a given system, total resistance is less than the resistance of any of the individual arteries.
TRUE
What is the equation for total resistance in parallel?
1/Rtot = 1/Ra + 1 Rb.. 1/Rh
Describe blood flow and pressure for blood vessels in parallel
Each artery in parallel receives a fraction of total blood flow. In each parallel artery, the pressure is the same.
Where is series resistance found?
Illustrated by the arrangements of blood vessels within a given organ
Where is parallel resistance found?
illustrated by systemic circulation (arteries branching off aorta)
The ___________ is the complete resistance that blood encounters as it flows from arterial to venous side of circulation
total peripheral resistance
The ______ is the resistance that blood encounters as it flows from capillaries back to the heart
venous resistance
__________ is fluid’s resistance to flow, “thickness,” or internal friction of the fluid
viscosity
What are the three factors that influence blood viscosity?
hematocrit, temperature, flow rate
What change in the following would cause blood viscosity to increase?
A) hematocrit
B) temperature
C) flow rate
A) increase in hematocrit, B) decrease in temperature, C) flow rate decrease (non-newtonian flow)
Blood behaves as a non-newtonian fluid which means that its viscosity changes as a function of _________
shear rate (velocity)
TRUE/FALSE: When blood moves quickly as in peak systole, it is thicker whereas when blood moves slowly during end-disastole, it is thinner.
FALSE - faster=thinner. RBC’s are sticky and aggregate at slower speeds.
What is polycythemia vera and how does it affect blood viscosity?
Polycythemia vera is a condition where there is increased RBC production from the bone marrow. This would increase blood viscosity (increased hematocrit).
How does whole body hypothermia during surgery affect blood viscosity?
It increases blood viscosity and increases resistance to flow due to decrease in temperature
How is blood viscosity affected during circulatory shock?
There is very low flow in the microcirculation causing increased cell to cell and protein to celll adhesive interactions –> increased viscosity
When laminar flow occurs, where is velocity of flow greatest?
Greatest in center of the vessel than toward the outer edges. FLOWS IN LAYERS, FASTER IN CENTER.
True or false: Flow is always proportional to driving P.
FALSE - only under laminar flow conditions
Where is velocity of flow lowest in laminar/streamline flow?
At vessel wall
__________ occurs when red blood cells move toward the center of the blood vessel in response to increased flow rate. This lowers apparent viscosity of blood.
Axial streaming
In _______ flow the blood flows in all directions in the vessel. Where are the fastest velocities found?
turbulent flow, fastest velocities not necessarily in the middle of the stream
True/False: Once a critical velocity is reached, turbulent flow results and then flow does not increase proportionally with rises in pressure
True
How is the critical velocity leading to turbulent flow defined?
Via Reynolds number (Ng). Ng = Vdp/n [ mean velocity * tube diameter * fluid density ] / fluid viscosity
What are the major factors that increase Reynold’s number (and therefore turbulence)
Decreased blood viscosity; increased blood velocity
How does lymphatic circulation differ from cardiovascular circulation?
lymphatic circulation is open, there is no pump and there is excess extracellular fluid and debris
__________ plays a role in blood pressure control and coagulation of blood
endothelium
How do endothelial cells affect blood pressure?
release angiotensin converting enzyme
How are the lymphatic and cardiovascular systems similar?
There is progressive branching to transport
What are the the main functions of the lymphatic system?
transport and homeostasis
Veins drain ___________ and transport to the heart
capillaries and capillary beds
What are the three layers of blood vessels?
tunica intima, tunica media, tunica adventitia
The __________ is the innermost layer of the blood vessel that contains the lumen
tunica intima
What is the tunica intima composed of?
simple squamous epithelium
What is secreted by the tunica intima?
collagen and laminin for ECM, NO for vasodilation, enzymes such as angiotensin converting enzyme (ACE)
True/False: The tunica intima is very metabolically active and plays a major role in homeostasis
True
What enters via the tunica intima?
water, electrolytes, O2, CO2
The ________ of the tunica intima is a cellular interface between epithelium and connective tissue made of glycoproteins and collagen
basal lamina
The __________ of the tunica intima is loose CT scattered with smooth muscle cells
subendothelial connective tissue
The _________ is a fenestrated sheet of elastin that allows diffusion of nutrients from endothelium to pass through and form gap junctions with smooth muscle cells in tunica media
internal elastic lamina
What is the main component of the tunica media?
Smooth muscle - allows for constriction or dilation
In the tunica media, the composition of elastin and collagen varies based on what?
function of the artery
In what vessels is the tunica media NOT found?
Not found in capillaries or post capillary venules
Describe structures/cells found on smaller and larger vessels in regards to the tunica media.
Smaller vessels have cells called pericytes; larger vessels have external elastic lamina
Where do smooth muscle cells start in the tunica media?
Start at the internal elastic lamina
The outermost layer of blood vessels is called ___________ and contains fibroblasts, collagen, elastic fibers that blend into the surrounding connective tissue
tunica adventitia
What two structures are contained on the tunica adventitia (important for blood flow)
vasa vasorum (the vessels of the vessels) and nerves (send signals to vessel to constrict or relax)
True/False: Nerves penetrate through all layers of the blood vessel
FALSE, only on outside, gap junctions relay info
When nerves in the tunica adventitia are stimulated what do they release? Describe the action
Noreepinephrine, diffuses through external elastic lamina and causes depolarization and contraction of outermost smooth muscle cells. Gap junctions propagate through layers of the tunica media.
When stimulated by sympathetic discharge, most blood vessels constrict. What are the exceptions?
skeletal muscle arteries dilate
True/False: In all elastic and muscular arteries, the vaso vasorum supplies with nutrients and O2 via diffusion
FALSE, only in small vessels, in larger vessels there are capillary beds to the tunica media
What are the three types of arteries?
muscular, elastic, arterioles
______ arteries are the biggest blood vessels and are involved in conduction of the blood from the heart.
Elastic arteries
The tunica media of the elastic arteries contain ______ fenestrated layers of elastin and allow vessels to stretch and _____ when alternating with smooth muscle cells which accommodates and propels the large bolus of blood from left ventricle
40-70, recoil
In the elastic arteries, what allows for movement and distention?
loose fibroelastic tissue in adventitia
Name some elastic arteries
pulmonary trunk, aorta, common carotid, subclavian, common iliacs
The ________ arteries are the distributing arteries and most named arteries. They include a prominent elastic lamina and external elastic lamina.
muscular
In muscular arteries, there are ______ layers that are connected via _____ to allow for propagation of nerve signals
4-40, gap junctions
What feature of muscular arteries allows neurotransmitters to pass?
clear external elastic lamina
The ______ are the terminal arteries where internal elastic lamina is poorly defined. There is no need for vasa vasorum in these vessels.
Arterioles
True/false: In arterioles, the tunica adventitia can be easily differentiated from connective tissue
FALSE - other layers can be differentiated though
What are the main differences between arteries and veins?
Veins are larger, arteries have a thicker tunica media, arteries maintain their round shape in sections and usually won’t contain blood cells
______ are thin walled vessels with a single endothelial layer on a basal lamina
capillaries
True/False: Capillaries do not contain a tunica media or adventitia
TRUE
True/False Capillaries are involved in temperature control
TRUE
How do smooth muscle cells appear on slides?
will appear spindle shaped but on cross section will appear round
What are the three types of capillaries?
continuous, fenestrated, sinusoidal
In continuous capillaries, endothelial cells are connected via _______. These capillaries participate in ________ of amino acids and glucose
tight junctions, carrier-mediated transport
Where are continuous capillaries found?
nervous, muscle and connective tissue. modified in brain to limit passage of molecules.
In fenestrated capillaries, there are thin openings called ______ that cover pores in endothelial cell walls. These allow more leak.
diaphragm
Where are fenestrated capillaries found?
pancreas, intestines, and endocrine glands. Found in glomeruli of kidney but with no diaphragms.
In sinusoidal capillaries there is a _______ endothelial wall and basal lamina which allows several blood cells to go through at once. They also have _____ that conform to structure in which they are located.
discontinuous; irregular channels
Where are sinusoidal capillaries found?
spleen, liver, bone marrow, lymphoid organs
True/False: Veins are more numerous than arteries, larger than corresponding arteries and contain 70% more blood volume
TRUE
True/false: Venule walls are more permeable than capillary walls
True
True/false: Veins have less vasa vasorum than arteries
FALSE - have more bc blood in circulation has less O2
What is the preferred site for white blood cell migration?
venules (lots in lymph nodes)
True/false: In large veins, the tunica adventitia is more developed that that of tunica media
True - tunica media is much less prominent in veins
True/false: Valves are found in all veins
FALSE -found in large and medium veins
True/false: Smooth muscle is found in all veins
FALSE - only those above >1mm
The ________ is made up of endothelial cells overlying connective tissue and fibroblasts and smoooth muscle cells in the heart
endocardium
The endothelium in the endocardium is continuous with the tunica intima of _______
great vessels
The subendocardial layer of loose connective tissue in the endocardium contains what three things?
nerves, blood vessels, purkinje fibers
The ______ contains heart muscle that is specialized for conduction. It is also important for endocrine functions, structure, and contraction
myocardium
Specialized cardiac muscle cells called ______ travel superficially in the myocardium
purkinje fibers
Describe the pathway of electrical impulse through the heart
SA node –> AV node –> Bundle of His –> Right and Left bundle branches –> Purkinje Fibers
What hormone actions are secreted from the myocardium?
Hormones that control BP, fluid and electrolytes
Myocardial cells are attached to the _________
fibrous skeleton
The ________ is also the visceral layer of the pericardium. It is the innermost layer of the pericardium and the outer surface of the heard.
Epicardium
_______ is the passage of blood cells through intact walls of capillaries, typically accompanies inflammation
diapedesis
What are the two main jobs of the lymphatic system?
transport fluid away from tissues and to serve an immune function
Describe the flow through the lymph system?
Lymphatic capillaries –> lymphatic vessels that drain regionally –> lymph nodes where it is filtered –> lymphatic ducts
Describe the differences in the lymph system in comparison to the CV system.
There is a thin walled endothelial layer but there are overlapping endothelial cells without tight junctions. Discontinuous basal lamina. Numerous valves in vessels. Lumens are larger than veins. Only largest vessels have smooth muscle cells. Ill-defined boundaries between three layers. Vessels similar to vasa vasorum.
The subendocardial connective tissue in heart is analogus to _____
tunica intima
________ are places where veins and arteries come together and allow in certain circumstances bypass of the capillary bed
arterial-venous anastomoses
What is Bernaud’s sign? What are the causes?
Bernaud’s sign is when digits turn white in cold weather. Can be related to autoimmune disorders and sometimes idopathic. Typically no ischemia.
What is the difference between cardiac and skeletal muscle?
Cardiac muscle has branching fibers, central nuclei and intercalated discs. Do not perfectly line up.
During lymph node circulation, afferent lymphatic vessels pierce the lymph node and open into the _______ and penetrate the cortex.
subcapsular sinus
After the lymph node cortex has been penetrated, _________ continue into the medulla as branching medullary sinuses surrounded by medullary cords
Paratrabecular sinuses
In the medulla, subcortical sinuses are confluent with medullary sinuses and penetrate the capsule to join the ___________
efferent lymphatic vessel
Where are B and T cells located in the lymph nodes?
B cells are contained in the lymphatic nodules (have a germinal center) and T cells are in the deep or inner cortex
What cells do the medullary cords contain?
macrophages and plasma cells
True/False: If sentinel nodes are negative for disease, likely that other nodes are negative as well
True
