DeWitt Ch. 2 Embryology & EKG Ch 1 Flashcards
This is an extensive review for TEST 1
What are the two layers of cells that form the heart before week 3?
Inner, thinner layer and outer, thicker layer
What forms during week 3 as heart tubes fuse?
Single endocardial heart tube
Which aortic arch forms the definitive aortic arch?
Left 4th arch
What structures are derived from the sinus venosus?
- SVC
- IVC
- Pulmonary veins
- CS
- Oblique vein of LV
- Posterior portion of RA & LA
What is the heart’s developmental milestone during week 4?
Heart begins to beat
What is the term for the loop formed during the heart’s development?
Bulboventricular loop
What is present when the septum primum grows from the wall of the primitive atrium?
Endocardial cushions
What closes when the septum primum reaches the endocardial cushions?
Ostium primum
What forms the RVOT & LVOT?
mid-portion of the bulbus cordis called the conus cordis connects the primative RV with the truncus arteriosus which ULTIMATELY will form the RVOT & LVOT
At what week does the septum secundum cease to grow?
Week 6
What increases the LAP at birth?
Increased pulmonary resistance
What is the only vessel to carry enriched blood with O2 saturation ~ 80%?
Umbilical vein
Fill in the blank: The _______ delivers O2 and nutrients to the fetus.
Placenta
What are the two shunts that allow blood to bypass the lungs in fetal circulation?
- Foramen Ovale (FO)
- Ductus Arteriosus (DA)
What is a PFO?
Patent Foramen Ovale
What is a PDA?
Patent Ductus Arteriosus
What does the fetal circulatory pattern mix?
O2 enriched and O2 depleted blood
What is the only great vessel leaving the heart during development?
Truncus arteriosus
How many pairs of aortic arches are there?
Six pairs
What are the major structures that develop from the truncus arteriosus?
- Aorta
- Main pulmonary artery
What is the primary function of the placenta in fetal circulation?
Exchanges O2, CO2, nutrients, and waste
What happens to the foramen ovale at birth?
Closes due to increased left atrial pressure
What does the ductus venosus connect?
Umbilical vein to IVC
Trace a drop of blood starting and ending at the placenta.
Placenta -> Umbilical vein -> Ductus venosus -> IVC -> RA -> FO -> LA -> LV -> AO -> Body
Week 3
What is the structure of the heart prior to week 3 of embryonic development?
A pair of tubes on either side of the midline
This structure is the earliest form of the heart in embryonic development.
How many layers of cells are present in the heart prior to week 3?
2 layers of cells
The heart consists of an inner, thinner layer and an outer, thicker layer.
What are the characteristics of the inner layer of cells in the heart prior to week 3?
Thinner
This layer is crucial for the initial formation of the heart structure.
What are the characteristics of the outer layer of cells in the heart prior to week 3?
Thicker
This layer provides structural support to the developing heart.
What is the heart tube formed from during the folding process?
Single endocardial heart tube
The heart tubes initially form in the midline and fuse during development.
What structures does the sinus venosus give rise to?
- SVC
- IVC
- Pulmonary veins
- CS
- Oblique vein of LV
- Posterior portion of RA & LA
The sinus venosus is located at the caudal end of the developing heart.
What does the primitive atrium develop into?
RA & LA
The primitive atrium is part of the early heart structure.
What is the function of the atrioventricular sulcus?
Divides primitive atrium & primitive ventricle
This sulcus is an important anatomical feature in heart development.
What does the primitive ventricle become?
- Apical portion of LV
- Inlet portion of RV
The primitive ventricle is crucial in forming the left and right ventricles.
What does the interventricular sulcus divide?
Primitive ventricle & bulbus cordis
This sulcus is important for the separation of heart chambers.
What structures are derived from the bulbus cordis?
- Apical portion of RV
- RVOT
- LVOT
- AO
- Main PA
The bulbus cordis is a significant part of the heart’s development.
What does the left 4th arch develop into?
Definitive AO arch
The aortic arch system is essential for proper circulation.
What does the distal left 6th arch become?
DA
The distal left sixth aortic arch contributes to the development of the ductus arteriosus.
What additional structures are formed from the aortic arches?
- Proximal portions of RPA & LPA
- Innominate artery
- Right subclavian artery
- Common carotid arteries
These structures are vital for systemic and pulmonary circulation.
True or False: Some aortic arches disappear by birth.
True
During development, not all aortic arches persist into birth.
Week 4
What happens to the bilateral heart tubes by week 4 of embryonic development?
They completely fuse to form a single tube
This marks a significant step in heart development.
What is one of the first systems to function in the embryo?
The heart
The heart begins to beat early in development.
What shape does the heart tube take as it grows?
S-shaped loop
This folding is typically to the right, known as d-looping.
What is formed during the heart’s development after the s-shaped loop?
Bulboventricular loop
This structure will later find its correct anatomical position within the chest.
What two major structures does the truncus arteriosus give rise to?
Ascending aorta and pulmonary trunk
These are critical for circulation.
What does the bulbus cordis represent in the developing heart?
Left ventricular outflow tract (LVOT) and right ventricular outflow tract (RVOT)
This area contributes to the formation of the ventricles.
What does the primitive ventricle develop into?
Trabeculated right and left ventricles
Trabeculation is important for efficient contraction.
What does the sinus venosus become in the mature heart?
Posterior portion of the right atrium and coronary sinus
This structure plays a role in venous return.
What are endocardial cushions responsible for?
Forming the valves of the heart
They play a crucial role in separating the heart chambers.
What is a primary birth defect associated with abnormal heart tube rotation?
L-Loop instead of D-Loop
This defect occurs when the heart tube rotates in the wrong direction.
What structure appears from the wall of the primitive atrium during heart development?
Septum primum
This structure is essential for the formation of atrial septation.
What remains after the septum primum grows?
Ostium primum
This is an important feature for blood flow during early development.
How do the sinus venosus and primitive atrium communicate?
Via the sinoatrial orifice
This communication is vital for proper heart function.
What occurs as the endocardial cushions grow within the atrioventricular canal?
Separation into left and right sided orifices
This leads to the formation of the mitral valve (MV) and tricuspid valve (TV).
What appears as a small ridge on the floor of the primitive ventricle?
Ventricular septum
This structure is crucial for separating the ventricles.
What is the truncus arteriosus in the context of heart development?
A common arterial trunk that eventually separates into aorta and pulmonary artery
Its proper development is critical for normal circulation.
What happens during week 5 of embryonic development in terms of septum primum?
Septum primum reaches endocardial cushions and closes ostium primum
This marks a critical step in the formation of the atrial septum.
What develops within the septum primum after it reaches the endocardial cushions?
Perforations develop within septum primum, leading to ostium secundum
This allows blood flow between the atria.
Week 5
What is the role of septum secundum during week 5?
Septum secundum develops
It is crucial for the separation of the right and left atria.
Where does the sinoatrial orifice communicate after it has shifted?
Sinoatrial orifice communicates with right atrium
This is important for normal heart rhythm.
What are the components that flank the sinoatrial orifice?
Right and left venous valves
They help guide blood flow into the right atrium.
What happens to the left venous valve during the growth of the septum secundum?
Left venous valve and septum spurium fuse with septum secundum
This is part of the structural development of the heart.
What is the primitive atrium?
The primitive atrium is one chamber
It is the original structure before further differentiation.
What is the foramen primum?
The opening that remains during the growth of septum primum
It is eventually closed as the heart develops.
What results from the resorption of septum primum tissue?
The foramen secundum is formed
This allows for continued fetal blood flow.
What is the consequence of errors in the formation of the atrial septum?
Results in PFO/ASD
These conditions can lead to various clinical implications.
Name the types of Atrial Septal Defects (ASDs).
- Superior vena cava ASD
- Secundum ASD
- Primum ASD
- IVC ASD
- Coronary sinus ASD
Each type is based on its location within the atrial septum.
What is noted about the most common types of ASD?
The most common are PFO or secundum ASD
These are frequently encountered in clinical practice.
What forms the newly developed bulboventricular loop?
RV and LV originate as trabecular expansions
This is a significant step in ventricular development.
How are the ventricles separated externally?
By the interventricular sulcus
This structure is important for heart anatomy.
What structure separates the ventricles internally?
Bulboventricular flange
It plays a key role in chamber formation.
What is the role of trabecular expansion from the bulbus cordis?
It contributes to the apical portion of the RV
This is essential for proper ventricular function.
What does the conus portion of the bulbus cordis develop into?
Right ventricular outflow tract (RVOT) and left ventricular outflow tract (LVOT)
These are critical for directing blood flow.
What does the trabecular expansion from the primitive ventricle form?
Apical portion of the LV
This is part of the overall ventricular architecture.
When does the trabecular interventricular septum (IVS) form?
As ventricles grow until late in the 7th week
Growth stops once ventricular walls are no longer expanding.
How does the primitive atrium communicate with the LV?
Via the atrioventricular canal and primitive ventricle
This is a temporary arrangement before full separation occurs.
What shifts to the right to allow communication with the RV?
Atrioventricular canal
This is a critical adjustment in heart development.
What are the two routes for LV to communicate with RV before full separation?
- Primary interventricular foramen
- Secondary interventricular foramen
These routes facilitate blood flow during development.
What characterizes the membranous portion of the IVS?
It is thinner and more prone to malformations
This area is often involved in ventricular septal defects (VSDs).
What is the structure of the inlet IVS?
Located at the level of the atrioventricular canal
It plays a role in the separation of the ventricles.
What are the three components of the IVS?
- Muscular toward apex
- Inlet
- Infundibular (outlet)
Each component has a specific role in ventricular function.
What is the significance of the muscular portion of the IVS?
It is a proliferation of cells from the apex toward the endocardial cushion
This is essential for the structural integrity of the heart.
Where can VSDs occur along the IVS?
VSDs can be anywhere along the IVS
There can be multiple defects present.
Week 6
What happens to the septum secundum in week 6 of embryology?
Septum secundum ceases to grow and forms the foramen ovale (FO)
The foramen ovale is an opening in the septum between the right and left atria.
What occurs with the endocardial cushions during week 6?
Superior and inferior endocardial cushions fuse
This fusion is crucial for the formation of the heart’s atrioventricular septum.
What is formed during week 6 in relation to the heart valves?
Atrioventricular valve cusps form
These cusps are essential for the proper functioning of the heart valves.
How does the right atrium communicate with the right ventricle during week 6?
Right atrium communicates with right ventricle
This communication is facilitated by the development of the tricuspid valve.
How does the left atrium communicate with the left ventricle during week 6?
Left atrium communicates with left ventricle
This communication is facilitated by the development of the mitral valve.
Week 7
What acts as a flap at the foramen ovale (FO) and controls blood flow between atria?
Remnant of septum primum
The septum primum is a structure in the heart that plays a crucial role in fetal circulation.
What happens at birth that forces the septum primum against the septum secundum?
Increase in left atrial pressure (LAP)
This pressure change is crucial for the closure of the foramen ovale.
What do the septum primum and septum secundum together form?
Interatrial septum (IAS)
The IAS separates the left and right atria in the heart.
What structure is formed during the final step of ventricular septation?
Membranous septum
This septum separates the left and right ventricles completely.
What develops within the truncus arteriosus to divide the lumen into two separate arteries?
Bulbar ridges
These ridges grow toward each other and fuse in the middle.
What is the outcome of the spiral growth in the truncus arteriosus?
Alignment of the pulmonary artery (PA) and aorta (Ao) with the appropriate ventricle
This alignment is essential for proper heart function postnatally.
By the end of which week is major fetal heart development complete?
7th week
This marks the completion of the basic structure of the fetal heart.
What condition is caused by septation defects in the truncus arteriosus?
Persistent truncus arteriosus
This condition involves a failure to separate the aorta and pulmonary artery.
What malformation is associated with the disruption of septation and spiraling in the aorticopulmonary area?
Tetralogy of Fallot
This is a congenital heart defect that affects normal blood flow through the heart.
What is the result of spiraling defects in the great vessels?
D-transposition of the great vessels
This condition involves the aorta and pulmonary artery being switched.
What week is this?
Week 3
What week is this?
Week 5
What week is this?
Week 4
What week is this?
Week 7
What week is this?
Week 4
What week is this?
Week 5
What week is this?
Week 7
What week is this?
Prior to Week 3
What week is this?
Week 5
Fetal Circulation
What is the primary function of the placenta in fetal circulation?
Delivers O2 & nutrients and removes waste products
The placenta plays a crucial role in maintaining the fetus’s needs by facilitating the exchange of gases and nutrients.
In fetal circulation, which side has a higher pressure?
Right side
The pressure difference between the right and left sides of the heart is significant in fetal circulation.
What physiological condition forces blood to bypass the lungs in fetal circulation?
Increased pulmonary resistance
This increased resistance is due to the non-functioning lungs in the fetus.
What are the names of the two shunts necessary in fetal circulation?
Foramen Ovale (FO) and Ductus Arteriosus (DA)
These shunts allow blood to bypass the lungs and direct it towards the systemic circulation.
Describe the fetal circulatory pattern.
Mixes O2 enriched & O2 depleted blood; begins & ends at placenta
This mixing occurs as the fetus receives oxygen and nutrients while simultaneously expelling waste.
How do the fetus and mother exchange gases and nutrients?
Through the placenta without their blood mixing
Exchange occurs via a network of capillaries, maintaining separate blood supplies.
What vessel carries O2 enriched blood from the placenta to the fetus?
Single umbilical vein
This vessel is essential for transporting oxygen and nutrients to the developing fetus.
What composition do all other fetal vessels carry?
Mixed blood composed of O2 enriched blood mixed with O2 depleted blood
This mixture is a result of the fetal circulatory system’s structure and function.
What is the pathway of enriched blood from the placenta?
Placenta enriched blood → umbilical vein → portal system
This describes the initial transport of enriched blood from the placenta to the fetal circulation.
What happens to a small amount of enriched blood in the portal system?
It mixes with the liver’s depleted blood
This occurs as part of the fetal circulation process, where some blood is processed by the liver.
How does the majority of enriched blood reach the inferior vena cava (IVC)?
Majority of enriched blood → ductus venosus → IVC
The ductus venosus allows the majority of enriched blood to bypass the liver and flow directly into the IVC.
What is the composition of blood in the IVC?
Depleted blood in IVC mixes with enriched blood from ductus venosus
This mixing is crucial for the distribution of oxygenated blood in fetal circulation.
What is the route of enriched blood from the IVC to the right atrium (RA)?
IVC enriched blood → EV → RA
The inferior vena cava (IVC) carries enriched blood to the right atrium.
What occurs in the right atrium (RA) regarding blood mixing?
Small amount of enriched blood in RA mixes with depleted blood from SVC
This mixing occurs before blood moves to the right ventricle (RV).
What is the pathway of blood from the right atrium to the left atrium (LA)?
Majority of blood in RA → FO → LA
The foramen ovale (FO) allows blood to flow from the right atrium to the left atrium.
What happens to enriched blood in the left atrium (LA)?
Enriched blood in LA mixes with a small amount of blood returning from lungs
This is part of the fetal circulation where oxygenated blood is prepared for systemic circulation.
What is the final destination of enriched blood from the left ventricle (LV)?
Enriched blood enters AO (aorta)
The aorta distributes oxygen-rich blood to the brain and upper body.
Fill in the blank: The pathway of enriched blood is placenta enriched blood → umbilical vein → _______.
portal system
This is the first step in the fetal circulation process.
True or False: The ductus venosus allows most of the enriched blood to be processed by the liver.
False
The ductus venosus bypasses the liver for the majority of the enriched blood.
What is the pathway of depleted blood in fetal circulation?
Depleted blood travels from SVC to RA
In the right atrium (RA), how does depleted blood mix?
Depleted blood from SVC mixes with a small amount of enriched blood from IVC
What is the next step after the right atrium (RA) in fetal circulation?
Blood flows to the right ventricle (RV) and then to the pulmonary artery (PA)
What happens to a small amount of blood in the pulmonary artery (PA)?
It goes to the lungs and returns to the left atrium (LA) via pulmonary veins (PV)
What is the fate of the majority of blood in the pulmonary artery (PA)?
It goes to the ductus arteriosus (DA) and then to the aorta (AO)
How does depleted blood mix in the aorta (AO)?
Depleted blood from the DA mixes with enriched blood from the proximal AO
What arteries are supplied by the abdominal aorta after mixing?
Abdominal aorta, common iliac arteries, internal iliac arteries
What do the internal iliac arteries give rise to?
They give rise to 2 umbilical arteries
Where do the umbilical arteries carry blood to?
They carry blood to the placenta
What happens to O2 and CO2 levels when placental blood flow is interrupted?
O2 level decreases and CO2 level increases
What occurs during the newborn’s first breath?
Lungs fill with air instead of fluid and body experiences higher levels of O2
What effect does increased pulmonary blood flow have on the left atrium?
Increases blood returning to LA and LAP increases
What anatomical structure closes due to increased left atrial pressure?
Foramen ovale (FO)
How quickly does the ductus arteriosus (DA) close after birth?
Almost immediately after birth
What causes the ductus arteriosus to close?
Muscular contraction (ligamentum arteriosum)
What happens to the umbilical arteries shortly after birth?
They close due to smooth muscle contraction
What is the timeline for the complete obliteration of the umbilical arteries?
2-3 months
What follows the closure of the umbilical arteries?
Closure of the umbilical vein and ductus venosus (ligamentum venosum)
What is the purpose of the delay in the closure of the umbilical vein and ductus venosus?
Allows time for any remaining blood in placenta to reach newborn before umbilical cord is cut
EKG Ch. 1
Where is the heart located?
Lies in the mediastinum between the lungs, about two thirds to the left of the midline of the sternum
What is the size of an adult heart compared to?
Roughly the size of the owner’s fist
What are the surfaces of the heart?
- Anterior surface
- Inferior surface (diaphragmatic)
- Base
- Apex
What is the innermost layer of the heart called?
Endocardium
What are the three layers of the heart wall?
- Epicardium
- Myocardium
- Endocardium
What are the four chambers of the heart?
- Right atrium
- Left atrium
- Right ventricle
- Left ventricle
What is the function of the heart skeleton?
Provides secure attachments for heart valves and myocardium
What are the two types of heart valves?
- Atrioventricular (AV) valves
- Semilunar (SL) valves
What are the names of the atrioventricular valves?
- Tricuspid valve
- Mitral (bicuspid) valve
What is the function of the semilunar valves?
Prevent backflow of blood from the aorta and pulmonary arteries into the ventricles
What does acute coronary syndrome refer to?
Conditions caused by abruptly reduced coronary artery blood flow
What are the primary branches of the right coronary artery (RCA)?
- Right atrium
- Right ventricle
- Inferior surface of the left ventricle
- Posterior surface of the left ventricle
- Sinoatrial (SA) node
- AV bundle
What does the left main coronary artery supply?
- Left anterior descending artery (LAD)
- Circumflex artery (Cx)
What is angina pectoris?
Chest discomfort caused by myocardial ischemia
What neurotransmitters are involved in sympathetic stimulation?
- Norepinephrine
- Epinephrine
What is the primary neurotransmitter in parasympathetic stimulation?
Acetylcholine
What do baroreceptors detect?
Changes in blood pressure
What is a positive chronotropic effect?
An increase in heart rate
What is systole?
Period during which the chamber is contracting and blood is being ejected
What is diastole?
Period of relaxation during which the chamber is filling
What does ejection fraction measure?
Percentage of blood pumped out of a ventricle with each contraction
What factors determine cardiac output?
- Heart rate (HR)
- Myocardial contractility
- Preload
- Afterload
- Stroke volume
Fill in the blank: Preload is the force exerted by the walls of the ventricles at the end of _______.
diastole
What are the signs and symptoms of decreased cardiac output?
- Acute drop in blood pressure
- Acute changes in mental status
- Cold, clammy skin
- Color changes in the skin and mucous membranes
- Crackles (rales)
- Dyspnea
- Dysrhythmias
- Fatigue
- Orthopnea
- Restlessness
What is the heart classified as?
Hollow muscular organ
Where does the heart lie in the body?
In the space between the lungs (mediastinum) in the chest
Approximately how much of the heart lies to the left of the midline of the sternum?
About two thirds
What anatomical structures are located behind the heart?
Sternum and diaphragm
Between which ribs does the heart primarily lie?
Between the second through the sixth ribs
Fill in the blank: The heart sits behind the _______.
[sternum]
True or False: The entire heart lies to the left of the midline of the sternum.
False
What is the remaining third of the heart’s location in relation to the sternum?
Lies to the right of the sternum
What is the approximate size of an adult heart?
About the size of the owner’s fist
What factors influence heart size and weight?
- Age
- Body weight and build
- Physical exercise frequency
- Heart disease
What percentage of a man’s body weight is the heart?
About 0.45%
What percentage of a woman’s body weight is the heart?
About 0.40%
True or False: Heart size and weight are the same for all individuals.
False
Fill in the blank: The heart’s weight is about _______ of a man’s body weight.
0.45%
Fill in the blank: The heart’s weight is about _______ of a woman’s body weight.
0.40%
Which factor does NOT influence heart size and weight?
Height
What lies behind the sternum and costal cartilages?
Anterior surface of the heart
The anterior surface is mostly formed by the right atrium and right ventricle.
Which area of the heart lies most directly behind the sternum?
Right ventricle
The right ventricle is positioned due to the heart’s slight tilt toward the left.
What is the inferior surface of the heart also called?
Diaphragmatic surface
This surface is primarily made up of the left ventricle.
What forms most of the heart’s inferior surface?
Left ventricle
The inferior surface includes the right and left ventricles and a small portion of the right atrium.
What separates the right and left ventricles on the inferior surface?
Groove containing the posterior interventricular vessels
This groove helps to delineate the two ventricles.
What does the base of the heart consist of?
Left atrium, small portion of the right atrium, proximal portions of the superior and inferior venae cavae, and pulmonary veins
The base is the upper portion of the heart.
What forms the apex of the heart?
Tip of the left ventricle
The apex is the lower portion of the heart.
At what anatomical level is the apex of the heart positioned?
Level of the left fifth intercostal space at the midclavicular line
This positioning is important for clinical examinations.
Fill in the blank: The anterior surfaces of the right and left ventricles are separated by the _______.
Left anterior descending artery
This artery plays a crucial role in supplying blood to the heart muscle.
What is the pericardium?
A double-walled sac that encloses the heart and helps protect it from trauma and infection
What are the two layers of the pericardium?
Fibrous parietal pericardium and serous pericardium
What is the tough outer layer of the pericardium called?
Fibrous parietal pericardium
What does the parietal pericardium do?
Forms the outer layer of the pericardial sac
What is the visceral pericardium also known as?
Epicardium
What is contained within the pericardial space?
Serous fluid
What is the typical volume of serous fluid in the pericardial space?
About 20 mL
What is the function of the serous fluid in the pericardial space?
Acts as a lubricant, preventing friction as the heart beats
What structures does the fibrous parietal pericardium anchor the heart to?
Sternum and diaphragm
Fill in the blank: The inner layer of the pericardium consists of _______ layers.
Two
True or False: The visceral pericardium attaches directly to the heart’s surface.
True
What separates the visceral and parietal layers of the serous pericardium?
Pericardial space
What color and consistency is the serous fluid in the pericardial space?
Pale yellow and transparent
What prevents excessive movement of the heart in the chest?
Anchoring by ligaments from the fibrous parietal pericardium
What is the innermost layer of the heart wall called?
Endocardium
The endocardium lines the heart’s inner chambers and is continuous with the innermost layer of vessels.
What are the three tissue layers of the heart wall?
- Endocardium
- Myocardium
- Epicardium
These layers work together to form the heart’s structure and function.
What is the primary function of the myocardium?
Responsible for pumping action
The myocardium consists of cardiac muscle fibers that enable the heart to pump blood.
What percentage of the total left ventricular mass does the myocardium make up?
About 30%
This indicates the significant volume of muscle tissue involved in heart function.
What separates the muscle fibers in the myocardium?
Connective tissues
These connective tissues contain a rich supply of capillaries and nerve fibers.
What is the outermost layer of the heart called?
Epicardium
The epicardium contains blood capillaries, lymph capillaries, nerve fibers, and fat.
What structures are found on the epicardial surface of the heart?
Main coronary arteries
These arteries supply the heart’s inner layers with oxygenated blood.
Fill in the blank: The innermost half of the myocardium is called the _______.
Subendocardial area
This area is crucial for the heart’s function and is part of the myocardium.
Fill in the blank: The outermost half of the myocardium is called the _______.
Subepicardial area
This area is also part of the myocardium and plays a role in heart function.
What is ischemia?
Decreased supply of oxygenated blood
Ischemia can affect parts of the body, including the heart, leading to serious conditions.
Which area of the heart is at the greatest risk of ischemia?
Subendocardial area
This area has a high oxygen demand and is fed by the coronary arteries’ most distal branches.
What type of muscle fibers form the walls of the heart?
Cardiac muscle fibers
Cardiac muscle fibers are unique and differ from other muscle types.
What structures are responsible for the contraction of cardiac muscle fibers?
Myofibrils
Myofibrils are packed closely together within muscle fibers.
What protein molecules are involved in producing muscle contractions?
- Myosin
- Actin
These proteins interact to facilitate muscle contraction.
What are intercalated disks?
Junctions that connect adjacent cardiac muscle fibers
They allow for coordinated contraction of the heart.
What function do gap junctions serve in cardiac muscle?
Allow electrical impulses to move rapidly between fibers
Gap junctions are essential for synchronized heart contractions.
What is the composition of cardiac muscle fibers?
- Mitochondria
- Myofibrils
- Sarcomeres
- Myofilaments
These components work together to enable contraction and energy production.
What inhibits myosin-actin interactions in cardiac muscle?
- Tropomyosin
- Troponin
These proteins play a regulatory role in muscle contraction.
What happens to cardiac muscle fibers when one fiber is stimulated?
All fibers become stimulated
This phenomenon is due to the syncytium function of cardiac muscle.
Fill in the blank: Cardiac muscle fibers are typically _______.
branched
This branching allows for the unique connectivity of cardiac muscle.
True or False: Cardiac muscle fibers can function independently of each other.
False
Cardiac muscle fibers function as a syncytium, requiring coordination.
What are the energy-producing parts of cardiac muscle cells?
Mitochondria
Mitochondria are crucial for ATP production in muscle cells.
How many chambers does the heart have?
Four chambers
The heart consists of two atria and two ventricles.
What are the two upper chambers of the heart called?
Right and left atria
The singular term for atria is atrium.
What are the two lower chambers of the heart called?
Right and left ventricles
What is the function of the atria?
To receive blood
What does the right atrium receive blood from?
Superior vena cava, inferior vena cava, coronary sinus
The superior vena cava carries blood from the head and upper extremities, while the inferior vena cava carries blood from the lower body.
What does the left atrium receive blood from?
Lungs via right and left pulmonary veins
Why do the atria have thin walls?
They encounter little resistance when pumping blood to the ventricles
What is the function of the right ventricle?
Pumps blood through the blood vessels of the lungs
What is the function of the left ventricle?
Pumps blood out to the body
Why do the ventricles have a thicker myocardial layer than the atria?
They must pump blood either to the lungs or to the rest of the body
What is an auricle in relation to the heart?
An earlike flap that protrudes from each atrium
Fill in the blank: The heart has two upper chambers called the right and left _______.
atria
True or False: The left atrium receives deoxygenated blood.
False
The left atrium receives freshly oxygenated blood from the lungs.
What is the primary function of the heart skeleton?
Provides secure attachments for heart valves
The skeleton of the heart encircles all four valves and supports their rims.
What does the heart skeleton provide for the myocardium?
Attachment
The outside of the rings of the heart skeleton provides for the attachment of the myocardium.
What structures do the partitions (septa) in the heart separate?
Atria from the ventricles
The heart skeleton helps form the partitions that separate these chambers.
How many rings of thick connective tissue make up the heart skeleton?
Four
These rings surround the bases of the pulmonary trunk, the aorta, and the heart valves.
The inside of the rings of the heart skeleton provides secure attachments for what?
Heart valves
This secure attachment is crucial for the proper function of the heart valves.
Fill in the blank: The skeleton of the heart encircles all four _______.
Valves
Each valve’s rim is supported by the fibrous structure of the heart skeleton.
True or False: The heart skeleton is made of muscle tissue.
False
The heart skeleton is composed of thick connective tissue, not muscle tissue.
How many valves are in the heart?
Four valves
What are the two types of atrioventricular (AV) valves in the heart?
Tricuspid valve, Mitral valve
What are the two types of semilunar (SL) valves in the heart?
Pulmonary valve, Aortic valve
What is the primary function of the heart valves?
Ensure blood flows in one direction through heart chambers
What do heart valves prevent?
Backflow of blood
True or False: The valves in the heart open and close randomly.
False
Fill in the blank: The heart valves assist in producing the _______ needed between the chambers.
Pressure gradient
What is the significance of the sequence in which the heart valves open and close?
It ensures a smooth flow of blood through the heart
List the two sets of valves in the heart.
- Atrioventricular (AV) valves
- Semilunar (SL) valves
What do Atrioventricular (AV) valves separate?
Atria from ventricles
What is the name of the AV valve that lies between the right atrium and the right ventricle?
Tricuspid valve
How many leaflets does the tricuspid valve have?
Three
What are chordae tendineae?
Thin strands of connective tissue
Where are chordae tendineae attached?
To the underside of the AV valves and to papillary muscles
What are papillary muscles?
Small mounds of myocardium projecting inward from the ventricular walls
What role do papillary muscles play in heart function?
They adjust tension on the chordae tendineae to prevent bulging into the atria
What is another name for the mitral valve?
Bicuspid valve
How many cusps does the mitral valve have?
Two
What is the function of the AV valves?
To open when a forward pressure gradient forces blood and to close when a backward pressure gradient occurs
What percentage of blood flows directly through the atria into the ventricles before atrial contraction?
80%
What is the term for the additional blood contributed by atrial contraction?
Atrial kick
What happens to the tricuspid and mitral valves during ventricular contraction?
They completely close when the pressure within the ventricles exceeds that of the atria
Fill in the blank: The mitral valve is named for its resemblance to a _______.
Miter
True or False: The AV valves require a significant amount of backflow to cause closure.
False
What happens to the pressure within the atrial chamber as it fills with blood?
It rises
What type of blood empties from the right atrium into the right ventricle?
Blood low in oxygen
What type of blood empties from the left atrium into the left ventricle?
Freshly oxygenated blood
What do the semilunar valves prevent?
Backflow of blood from the aorta and pulmonary arteries into the ventricles
Name the two types of semilunar valves.
- Pulmonic valve
- Aortic valve
What shape do the cusps of semilunar valves resemble?
Half moons
How many cusps do semilunar valves have?
Three
How do the openings of semilunar valves compare to atrioventricular (AV) valves?
Smaller
What is a key structural difference between semilunar valves and AV valves?
SL valves are not attached to chordae tendineae
When do the semilunar valves open?
When the ventricles contract
What type of blood flows through the pulmonic valve?
Blood low in oxygen
What happens to blood flow when the left ventricle contracts?
Freshly oxygenated blood flows through the aortic valve into the aorta
What triggers the closure of the semilunar valves?
Pressure in the pulmonary artery and aorta exceeds that of the ventricles
What causes heart sounds?
Vibrations in the heart’s tissues caused by the closing of the heart’s valves
What is the first heart sound known as?
S1
What reflects the start of ventricular contraction?
Closure of the tricuspid and mitral (AV) valves
Where is S1 heard loudest?
At the apex of the heart
What is the second heart sound known as?
S2
What reflects the start of ventricular relaxation?
Closure of the pulmonic and aortic (SL) valves
Where is S2 heard loudest?
At the base of the heart
What is a third heart sound called?
S3
What produces S3?
Ventricular filling
Is S3 considered normal in children and healthy young adults?
Yes
What is S3 generally associated with in individuals older than 40?
Heart failure
What is an S1–S2–S3 sequence called?
Ventricular gallop or gallop rhythm
How does the S1–S2–S3 sequence sound like?
Kentucky—Ken (S1)—tuck (S2)—y (S3)
What does coronary circulation consist of?
Coronary arteries and veins
What does the right coronary artery supply?
Right atrium, ventricle, and posterior aspect of the left ventricle
What are the branches of the left coronary artery?
Left anterior descending and circumflex arteries
What is the function of the coronary arteries?
Supplying blood to the heart
How do the coronary arteries encircle the myocardium?
Like a crown, or corona
Where do the main coronary arteries lie?
On the outer (epicardial) surface of the heart
What are epicardial coronary arteries?
Coronary arteries that run on the surface of the heart
What do coronary arteries branch into?
Progressively smaller vessels, arterioles, and then capillaries
What supplies the subendocardium with blood?
Branches of the main coronary arteries
What are ‘feeder branches’ in coronary circulation?
Branches that penetrate the heart’s muscle mass
What characterizes the diameter of feeder branches?
Much narrower than main coronary arteries
What ensures the heart has an adequate blood supply?
Providing itself with a fresh supply of oxygenated blood
What are the two main vessels supplying oxygenated blood to the heart?
Right and left coronary arteries
True or False: The epicardium has a rich blood supply.
True
Fill in the blank: The coronary arteries are essential for supplying _______ to the heart.
blood
What are the first branches off the base of the aorta?
The right and left coronary arteries
These arteries are crucial for supplying blood to the heart muscle.
Where do the openings of the coronary arteries lie?
Just beyond the cusps of the aortic SL valve
This positioning is critical for effective blood flow during the cardiac cycle.
What happens to the coronary arteries during left ventricle contraction?
They are compressed, reducing blood flow to the tissues of the heart
This compression occurs during ventricular systole.
When do the coronary arteries fill with blood?
When the aortic valve is closed and the left ventricle is relaxed (diastole)
This phase allows for adequate perfusion of the heart muscle.
Name the three major epicardial coronary arteries.
The left anterior descending (LAD) artery, circumflex (Cx) artery, and right coronary artery (RCA)
Each of these arteries has specific areas of the heart that they supply.
What is the Right Coronary Artery (RCA)?
A major artery that supplies blood to the heart
Which structures are supplied by a branch of the RCA?
- Right atrium
- Right ventricle
- Inferior surface of the left ventricle in about 85% of individuals
- Posterior surface of the left ventricle in 85%
- Sinoatrial (SA) node in about 60%
- AV bundle in 85% to 90%
From where does the RCA originate?
The right side of the aorta
How does the RCA travel in relation to the heart?
Along the groove between the right atrium and the right ventricle
True or False: The RCA supplies the sinoatrial (SA) node in about 60% of individuals.
True
Fill in the blank: The RCA supplies the _______ surface of the left ventricle in about 85% of individuals.
inferior
What percentage of individuals does the RCA supply the posterior surface of the left ventricle?
85%
What percentage of individuals does the RCA supply the AV bundle?
85% to 90%
What is the first segment of the Left Coronary Artery (LCA) called?
The left main coronary artery
What does the Left Coronary Artery (LCA) supply?
Oxygenated blood
What are the two primary branches of the Left Coronary Artery (LCA)?
- Left anterior descending (LAD)
- Circumflex (Cx)
What is another name for the left anterior descending artery?
Anterior interventricular artery
Where does the Left Coronary Artery (LCA) originate?
From the aorta’s left side
What is the approximate diameter of the left main coronary artery?
About the diameter of a soda straw
How long is the left main coronary artery?
Less than 1 inch (2.5 cm) long
True or False: The left main coronary artery is larger than its primary branches.
True
Where does the Left Anterior Descending Artery (LAD) lie?
On the outer (i.e., epicardial) surface on the front of the heart
What is the significance of occlusion of the proximal LAD coronary artery?
Referred to as the ‘widow maker’ due to its association with sudden cardiac arrest when blocked
Along which groove does the LAD travel?
The anterior interventricular sulcus
What is the endpoint of the LAD in most patients?
Ends along the left ventricle’s inferior surface
In some patients, where does the LAD stop?
At or before the heart’s apex
What are the major branches of the LAD?
The septal and diagonal arteries
What areas does the LAD supply blood to? (List three)
- The anterior surface of the left ventricle
- Part of the lateral surface of the left ventricle
- The anterior two-thirds of the interventricular septum
What is the Circumflex Artery?
An artery that circles around the left side of the heart in a groove on the back of the heart called the coronary sulcus
It separates the left atrium from the left ventricle.
What structures does the Circumflex Artery supply blood to?
- The left atrium
- Part of the lateral surface of the left ventricle
- The inferior surface of the left ventricle in about 15% of individuals
- The posterior surface of the left ventricle in 15%
- The SA node in about 40%
- The AV bundle in 10% to 15%
These percentages indicate the variability in supply among different individuals.
The Circumflex Artery supplies blood to the SA node in what percentage of individuals?
About 40%
The SA node is crucial for heart rhythm regulation.
True or False: The Circumflex Artery supplies blood to the left atrium.
True
It is one of the key areas supplied by the Circumflex Artery.
Fill in the blank: The Circumflex Artery separates the left atrium from the left ventricle in a groove called the _______.
coronary sulcus
This groove is important for the positioning of the Circumflex Artery.
What part of the heart does the Circumflex Artery primarily circle around?
The left side of the heart
This positioning is crucial for its function.
What does acute coronary syndrome (ACS) refer to?
Distinct conditions caused by a similar sequence of pathologic events involving abruptly reduced coronary artery blood flow
This sequence results in conditions ranging from myocardial ischemia or injury to death of the heart muscle.
What is the usual cause of an acute coronary syndrome?
Rupture of an atherosclerotic plaque
Define arteriosclerosis.
Chronic disease of the arterial system characterized by abnormal thickening and hardening of vessel walls
What is atherosclerosis?
A form of arteriosclerosis characterized by thickening and hardening of vessel walls due to a buildup of fat-like deposits
What results from the buildup of fat-like deposits in arteries?
Decreased blood flow (ischemia)
What is angina pectoris?
Chest discomfort or other related symptoms caused by myocardial ischemia
What may result from a partial or intermittent blockage of a coronary artery?
No clinical symptoms, angina, heart attack (myocardial infarction), sudden death
True or False: Angina is a disease.
False
In which patients is angina most often observed?
Patients with coronary artery disease involving at least one coronary artery
What happens when myocardial ischemia or infarction is suspected?
Understanding coronary artery anatomy helps predict which coronary artery is blocked
What can prevent tissue death in cases of blocked coronary vessels?
Quickly restoring blood flow and oxygen to the injured area
What methods can restore blood flow in acute coronary syndrome?
Clot-busting drugs (fibrinolytics) or endovascular therapies
Fill in the blank: Angina occurs in persons with uncontrolled high blood pressure or _______.
[valvular heart disease]
What are the zones associated with a blocked coronary artery?
Zones of ischemia, injury, and infarction
What is myocardial infarction (MI)?
Heart attack
What are characteristic changes associated with the zones of ischemia, injury, and infarction?
Characteristic ECG changes
What do the coronary (cardiac) veins do?
They drain blood that has passed through the myocardial capillaries
Where does the coronary sinus lie?
In the groove (sulcus) that separates the atria from the ventricles
What is the largest vein that drains the heart?
The coronary sinus
Which veins drain into the coronary sinus?
- Great cardiac vein
- Middle cardiac vein
- Small cardiac vein
- A vein of the left atrium
- Left ventricle’s posterior vein
Into which chamber does the coronary sinus drain?
The right atrium
True or False: The anterior cardiac veins join the coronary sinus.
False
Where do the anterior cardiac veins empty?
Directly into the right atrium
What are the primary neurotransmitters involved in sympathetic stimulation?
Norepinephrine, epinephrine
These neurotransmitters are crucial for the body’s response during stress or emergencies.
What is the primary function of the sympathetic division?
To prepare the body for emergency or stressful situations
This preparation includes a variety of physiological changes to enhance survival.
What happens to the pupils during sympathetic stimulation?
Dilation of pupils
This allows more light to enter the eyes, improving vision in low light conditions.
What effect does sympathetic stimulation have on the bronchi?
Dilation of smooth muscles of bronchi
This improves oxygenation during stressful situations.
How does sympathetic stimulation affect heart rate?
Increased heart rate
This is part of the body’s response to prepare for physical activity.
What is the effect of sympathetic stimulation on blood pressure?
Increased blood pressure
This helps ensure adequate blood flow to vital organs.
What happens to cardiac output during sympathetic stimulation?
Increased cardiac output
This is essential for meeting the body’s heightened demands for oxygen and nutrients.
What is the effect on sweating during sympathetic stimulation?
Increased sweating
This helps regulate body temperature during stress.
What is mobilized to ensure an adequate supply of energy during sympathetic stimulation?
Stored energy such as glucose and fatty acids
This ensures that the brain and muscles have enough resources for heightened activity.
During sympathetic stimulation, where is blood shunted from?
From skin and blood vessels of internal organs
Blood is redirected to skeletal muscle to enhance physical performance.
Fill in the blank: Sympathetic stimulation results in ______ of smooth muscles of bronchi.
Dilation
This is crucial for improving oxygenation.
True or False: Sympathetic stimulation decreases heart rate.
False
Sympathetic stimulation increases heart rate to prepare the body for action.
What are the five main types of sympathetic receptors?
Alpha1, Alpha2, Beta1, Beta2, Beta3
Where are Alpha1 receptors located?
Eyes, blood vessels, bladder, male reproductive organs
What is the physiological action of stimulating Alpha1 receptors?
Constriction
Where are Alpha2 receptors found?
Digestive system, presynaptic nerve terminals in the peripheral nervous system
What happens when Alpha2 receptors are stimulated?
Decreased secretions, peristalsis, suppression of norepinephrine release
Where are Beta1 receptors located?
Heart, kidneys
What is the effect of stimulating Beta1 receptors in the heart?
Increased heart rate, contractility, irritability of cardiac cells
What does stimulation of Beta1 receptors in the kidneys promote?
Release of renin into the blood
What is the role of renin in the body?
Promotes the production of angiotensin, a potent vasoconstrictor
Where are Beta2 receptors found?
Bronchial smooth muscle, skeletal blood vessels, arterioles of the heart and lungs
What happens when Beta2 receptors are stimulated?
Dilation
Where are Beta3 receptors located?
Fat cells
What is the physiological action of stimulating Beta3 receptors?
Promotes the breakdown of fats and other lipids
What is the primary neurotransmitter involved in parasympathetic stimulation?
Acetylcholine
Acetylcholine (ACh) is released when parasympathetic nerves are stimulated.
What is the main effect of parasympathetic stimulation on the heart?
Slowing of heart rate
This effect is primarily due to the actions of acetylcholine on the heart.
Which nerve fibers supply the SA node, atrial muscle, and the heart’s AV bundle?
Parasympathetic (inhibitory) nerve fibers
These fibers are supplied by the vagus nerves.
What are the two main types of parasympathetic receptors?
- Nicotinic receptors
- Muscarinic receptors
Nicotinic receptors are located in skeletal muscle, while muscarinic receptors are found in smooth muscle.
What is the effect of parasympathetic stimulation on the SA node?
Slows the rate of discharge
This results in a decreased heart rate.
How does parasympathetic stimulation affect conduction through the AV node?
Slows conduction
This can lead to a delay in the electrical signals reaching the ventricles.
What effect does parasympathetic stimulation have on atrial contraction strength?
Decreases the strength of atrial contraction
This can affect the overall efficiency of the heart’s pumping action.
Fill in the blank: Atropine sulfate is used to _______ heart rate and AV conduction velocity.
increase
Atropine sulfate works by blocking the vagus nerve’s effects on the SA and AV nodes.
What is a possible effect of parasympathetic stimulation on ventricular contraction?
Can cause a small decrease in the force of ventricular contraction
This is generally less pronounced than effects on the atria.
What are baroreceptors?
Specialized nerve tissue that detects changes in blood pressure
Found in the internal carotid arteries and the aortic arch.
Where are baroreceptors located?
In the internal carotid arteries and the aortic arch
These are critical areas for blood pressure regulation.
What do baroreceptors detect?
Changes in blood pressure
They act as sensors for the cardiovascular system.
What happens when baroreceptors are stimulated?
They cause a reflex response in the sympathetic or parasympathetic divisions of the autonomic nervous system
This response helps regulate blood pressure.
What is the sympathetic response when blood pressure decreases?
Constricting peripheral blood vessels, increasing heart rate, increasing force of myocardial contraction
This response is known as sympathetic or adrenergic response.
What is the parasympathetic response when blood pressure increases?
Decrease sympathetic stimulation and increase parasympathetic response
This response is known as parasympathetic or cholinergic response.
What is the term for the adjustment of baroreceptors to a new normal blood pressure?
They adjust to a new normal after a few days of exposure
This reflects the body’s ability to adapt to changes in blood pressure.
Fill in the blank: Baroreceptors are specialized nerve tissue found in the _______.
internal carotid arteries and aortic arch
True or False: Baroreceptors only respond to increased blood pressure.
False
Baroreceptors respond to both increases and decreases in blood pressure.
What are chemoreceptors?
Chemoreceptors are specialized cells that detect changes in the concentration of hydrogen ions (pH), oxygen, and carbon dioxide in the blood.
They play a crucial role in monitoring and regulating respiratory and cardiovascular functions.
Where are chemoreceptors located?
Chemoreceptors are located in the internal carotid arteries and the aortic arch.
These locations allow them to closely monitor blood composition as it is delivered to the brain and the rest of the body.
What changes do chemoreceptors respond to?
Chemoreceptors respond to changes in the concentration of:
* Hydrogen ions (pH)
* Oxygen
* Carbon dioxide
This detection is vital for maintaining homeostasis in the body.
What type of nervous system response can result from chemoreceptor activation?
The response can be sympathetic or parasympathetic.
These responses help regulate cardiovascular and respiratory functions based on the detected blood gas levels.
What does the term ‘Chronotropic Effect’ refer to?
A change in heart rate
The term is used in cardiology to describe how heart rate is influenced by various factors.
What is a positive chronotropic effect?
An increase in heart rate
This effect can be induced by factors such as sympathetic stimulation or certain medications.
What is a negative chronotropic effect?
A decrease in heart rate
This effect can occur due to parasympathetic stimulation or the use of specific drugs.
What does inotropic effect refer to?
A change in myocardial contractility
What is the result of a positive inotropic effect?
An increase in myocardial contractility
What is the result of a negative inotropic effect?
A decrease in myocardial contractility
vWhat does the term ‘Dromotropic Effect’ refer to?
A change in the speed of impulse conduction through the conduction system
What is the result of a positive dromotropic effect?
An increase in conduction velocity
What is the result of a negative dromotropic effect?
A decrease in conduction velocity
What does the pulmonary circulation route do?
Routes blood flow to and from the gas-exchange tissues of the lungs
It is responsible for oxygenating blood.
What does the systemic circulation route do?
Routes blood flow to and from the oxygen-consuming tissues of the body
It delivers oxygenated blood to organs.
What separates the right and left sides of the heart?
An internal wall of connective tissue called a septum
There are two types of septa: interatrial and interventricular.
What is the function of the interatrial septum?
Separates the right and left atria
It prevents mixing of oxygenated and deoxygenated blood.
What is the function of the interventricular septum?
Separates the right and left ventricles
It ensures that blood flows correctly through the heart.
How many functional pumps does the heart have?
Two functional pumps
The right atrium and ventricle form one pump; the left atrium and ventricle form the other.
What is the purpose of the right side of the heart?
Pumps unoxygenated blood from the body to the lungs
This process is part of pulmonary circulation.
What is the purpose of the left side of the heart?
Receives oxygenated blood from the lungs and pumps it to the body
This process is part of systemic circulation.
What vessels carry blood away from the heart?
Arteries, arterioles, and capillaries
These vessels distribute oxygenated blood to body tissues.
How is blood returned to the right side of the heart?
Through venules and veins
This process collects deoxygenated blood from the body.
What is the thickness of the left ventricle wall?
About 13 to 15 mm thick
This thickness allows it to generate high pressure to pump blood.
What is the thickness of the right ventricle wall?
About 3 to 5 mm thick
This thickness is sufficient for its lower pressure function.
True or False: The left ventricle is a low-pressure chamber.
False
The left ventricle is a high-pressure chamber.
Fill in the blank: The left ventricle must overcome a lot of _______ and resistance to pump blood.
Pressure
This is why its wall is thicker than the right ventricle.
What is the cardiac cycle?
A repetitive pumping process that includes all events associated with blood flow through the heart
The cardiac cycle consists of two phases for each heart chamber: systole and diastole.
Define systole.
Period during which the chamber is contracting and blood is being ejected
Define diastole.
Period of relaxation during which the chamber is filling
What happens during ventricular diastole?
The myocardium receives its fresh supply of oxygenated blood from the coronary arteries
What factors affect the cardiac cycle?
The cardiac muscle’s ability to contract and the condition of the heart’s conduction system
Abnormalities of the cardiac muscle, the valves, or the conduction system may affect the heart’s efficiency as a pump.
What occurs to the pressure in each chamber during the cardiac cycle?
Pressure rises in systole and falls in diastole
What is the role of the heart’s valves?
Ensure that blood flows in the proper direction
How does blood flow between heart chambers?
From higher to lower pressure
What determines the pressure relationships during the cardiac cycle?
The careful timing of contractions
What provides the necessary timing of events between atrial and ventricular systole?
The heart’s conduction system
What occurs during atrial diastole?
Blood enters the right atrium, right atrium fills and distends, tricuspid valve opens, right ventricle fills, left atrium receives blood from pulmonary veins, mitral valve opens, blood flows into the left ventricle
Atrial diastole is the phase when the heart’s atria fill with blood in preparation for contraction.
What is venous return?
The amount of blood flowing into the right heart from the systemic circulation
Venous return is crucial for maintaining cardiac output and ensuring the ventricles receive adequate blood volume.
What happens to the tricuspid valve during atrial diastole?
The tricuspid valve opens, allowing the right ventricle to fill
The tricuspid valve is located between the right atrium and right ventricle and opens in response to pressure changes.
What is the function of the mitral valve during atrial diastole?
The mitral valve opens as the left atrium fills, allowing blood to flow into the left ventricle
The mitral valve is crucial for preventing backflow of blood into the left atrium during ventricular contraction.
What is the atrial kick?
The contraction of the atria that forces additional blood into the ventricles
The atrial kick is important for ensuring the ventricles are completely filled with blood before they contract.
What percentage of ventricular filling occurs before atrial contraction?
80%
This indicates that most of the ventricular filling is passive, relying on blood flow from the atria.
What phase follows atrial systole?
Atrial diastole
Atrial diastole is the phase where the atria relax and fill with blood again.
Fill in the blank: The left atrium receives oxygenated blood from _______.
the four pulmonary veins
The pulmonary veins are responsible for returning oxygen-rich blood from the lungs to the heart.
True or False: The ventricles fill completely with blood during atrial systole.
True
Atrial systole ensures that the ventricles are filled to capacity before they contract.
What is ventricular systole?
Blood is propelled through the systemic and pulmonary circulation
It is the phase of the cardiac cycle when the ventricles contract.
What happens to the SL valves during ventricular systole?
They close
This closure prevents backflow of blood during ventricular contraction.
What occurs during ventricular diastole?
Ventricles begin to passively fill with blood
This phase follows the closure of the SL valves.
What initiates ventricular systole?
Atrial diastole begins
This indicates a sequence in the cardiac cycle.
What is the role of the tricuspid valve during right ventricular contraction?
It closes to prevent backflow of blood
This ensures unidirectional flow from the right ventricle to the pulmonary circulation.
What is the role of the mitral valve during left ventricular contraction?
It closes to prevent backflow of blood
This ensures that blood flows from the left ventricle into the aorta.
What happens to the heart after the SL valves close?
The heart begins a period of ventricular diastole
This marks the transition between contraction and relaxation phases.
What characterizes ventricular diastole?
The ventricles are relaxed and filling passively with blood
This phase prepares the heart for the next cycle.
What begins the cardiac cycle again after ventricular diastole?
Atrial systole and the completion of ventricular filling
This completes the cycle of heartbeats.
What occurs during atrial systole?
Atria contract, pushing blood through the open tricuspid and mitral valves into the ventricles. Semilunar valves are closed.
Atrial systole is the first phase of the cardiac cycle.
What happens at the beginning of ventricular systole?
Ventricles contract, increasing pressure within the ventricles. The tricuspid and mitral valves close, causing the first heart sound.
This phase marks the transition from atrial to ventricular contraction.
What is the significance of the period of rising pressure in the cardiac cycle?
Semilunar valves open when pressure in the ventricle exceeds that in the arteries. Blood spurts into the aorta and pulmonary arteries.
This phase allows for the ejection of blood from the heart.
What occurs at the beginning of ventricular diastole?
Pressure in the relaxing ventricles drops below that in the arteries. Semilunar valves snap shut, causing the second heart sound.
This phase indicates the end of ventricular contraction.
What happens during the period of falling pressure in the cardiac cycle?
Blood flows from veins into the relaxed atria. Tricuspid and mitral valves open when pressure in the ventricles falls below that in the atria.
This phase allows the heart to refill with blood.
What is blood pressure?
Force exerted by circulating blood volume on walls of arteries
What is the formula for calculating blood pressure?
BP = cardiac output (CO) × peripheral resistance (PR)
What does blood pressure reflect?
The mechanical activity of the heart
What is peripheral vascular resistance?
Resistance to the flow of blood determined by blood vessel diameter and tone of vascular musculature
What is the relationship between blood volume in arteries and arterial blood pressure?
The volume of blood in the arteries is directly related to arterial blood pressure
How does an increase in cardiac output (CO) affect blood pressure?
Typically results in an increase in blood pressure
How does an increase in peripheral resistance (PR) affect blood pressure?
Typically results in an increase in blood pressure
What happens to blood pressure if either cardiac output (CO) or peripheral resistance (PR) decreases?
Results in a decrease in blood pressure
What is meant by ‘tone’ in the context of vascular musculature?
The normal state of balanced tension in body tissues
True or False: Blood pressure is independent of peripheral resistance.
False
What is the relationship between arterial blood volume and blood pressure?
Arterial blood pressure is directly proportional to arterial blood volume
This means that as blood volume increases, blood pressure also increases.
How are cardiac output (CO) and peripheral resistance (PR) related to arterial blood volume?
Both CO and PR are directly proportional to arterial blood volume, but for opposite reasons
CO affects the blood entering the arteries, while PR affects the blood leaving the arteries.
What happens to arterial blood volume when cardiac output increases?
The amount of blood entering the arteries increases, which tends to increase the volume of blood in the arteries
This results in an increase in arterial blood pressure.
What effect does an increase in peripheral resistance have on arterial blood volume?
It decreases the amount of blood leaving the arteries, which tends to increase the amount of blood left in them
An increase in PR can also lead to an increase in arterial blood pressure.
If both cardiac output and peripheral resistance increase, what is the overall effect on arterial blood volume?
Both increases lead to an increase in arterial blood volume
This results in a subsequent increase in arterial blood pressure.
What is cardiac output?
Amount of blood pumped into the aorta each minute by the left ventricle
Cardiac output is an important measure of heart function and circulatory health.
What are the factors that determine cardiac output?
- HR (Heart Rate)
- Myocardial contractility
- Preload
- Afterload
These factors interact to influence the efficiency and effectiveness of the heart’s pumping action.
What is stroke volume?
Amount of blood ejected from the left ventricle with each heartbeat
Stroke volume is a critical component of cardiac output.
How is cardiac output calculated?
Cardiac output (CO) is defined as stroke volume (SV) multiplied by heart rate (HR)
This formula emphasizes the relationship between the volume of blood pumped per heartbeat and the frequency of those heartbeats.
What is the definition of Ejection Fraction?
The percentage of blood pumped out of a ventricle with each contraction
Ejection fraction is a key indicator of heart function.
What is Ejection Fraction used to measure?
Ventricular function
It helps assess how well the heart is pumping.
What is considered a normal range for Ejection Fraction?
Between 50% and 65%
Values outside this range may indicate health issues.
What constitutes impaired ventricular function in terms of Ejection Fraction?
Ejection fraction is less than 40%
This indicates significant heart dysfunction.
What is stroke volume?
The amount of blood pumped by the heart in one contraction.
Stroke volume is a key indicator of cardiac function.
What determines stroke volume?
Stroke volume is determined by:
* The degree of ventricular filling when the heart is relaxed (preload)
* The pressure against which the ventricle must pump (afterload)
* The myocardium’s contractile state (contracting or relaxing)
These factors collectively influence the efficiency of the heart’s pumping action.
Fill in the blank: Stroke volume is determined by the degree of ventricular filling when the heart is relaxed (_______).
preload
Fill in the blank: The pressure against which the ventricle must pump is known as _______.
afterload
True or False: Stroke volume is solely determined by preload.
False
Stroke volume is influenced by preload, afterload, and the contractile state of the myocardium.
What are the three main factors that influence stroke volume?
The three main factors are:
* Preload
* Afterload
* Myocardial contractility
Understanding these factors helps in assessing cardiac health.
What is preload?
The force exerted by the walls of the ventricles at the end of diastole.
Preload is also referred to as end-diastolic volume.
What influences preload?
The volume of blood returning to the heart (venous return).
Increased venous return raises preload, while decreased venous return lowers it.
According to the Frank-Starling law of the heart, what is the relationship between cardiac muscle stretch and contraction?
The greater the cardiac muscle stretch (within limits), the greater the resulting contraction.
This law explains how the heart adjusts its force of contraction based on the volume of blood filling the ventricles.
What happens to heart muscle fibers in response to increased preload?
Heart muscle fibers stretch in response to the increased volume before contracting.
This stretching allows the heart to eject the additional volume with increased force.
What is the effect of greater preload on stroke volume (SV)?
Greater preload leads to a greater force of ventricular contraction and increased stroke volume.
This results in increased cardiac output (CO).
Fill in the blank: Preload is also known as _______.
end-diastolic volume.
True or False: Less blood returning to the heart increases preload.
False.
Less blood returning decreases preload.
What is afterload?
The pressure or resistance against which the ventricles must pump to eject blood
What factors influence afterload?
- Arterial blood pressure
- Arterial distensibility
- Arterial resistance
True or False: Lower afterload makes it easier for the heart to eject blood.
True
What happens to the heart’s workload when afterload increases?
Increases the heart’s workload
Fill in the blank: Conditions that contribute to increased afterload include increased thickness of the blood (________) and high blood pressure.
viscosity
What is cardiac output?
The amount of blood pumped by the heart per minute
Cardiac output is influenced by heart rate and stroke volume.
What factors influence heart rate?
Multiple factors including autonomic nervous system activity, hormonal influences, and physical activity
These factors can increase or decrease heart rate.
What factors affect stroke volume?
Preload, afterload, and contractility
These factors determine the volume of blood ejected by the ventricles with each heartbeat.
How can cardiac output be increased?
By an increase in heart rate or stroke volume
Both mechanisms can enhance the volume of blood pumped by the heart.
What happens to the cardiac cycle when heart rate increases?
All phases of the cardiac cycle shorten
The most significant effect is on the relaxation phase.
What is the consequence of a shortened ventricular relaxation time?
Less time for ventricles to fill adequately with blood
This can lead to decreased blood flow and potential ischemia.
What are the effects of inadequate ventricular filling?
Reduced blood sent to coronary arteries and decreased cardiac output
This can lead to signs of myocardial ischemia.
True or False: An increase in heart rate always leads to an increase in cardiac output.
False
If the heart rate increases too much, it can lead to inadequate filling of the ventricles.
What is an acute drop in blood pressure a sign of?
Decreased cardiac output
Indicates a significant reduction in the heart’s ability to pump blood effectively.
Which symptom involves sudden changes in awareness or cognitive function?
Acute changes in mental status
Can manifest as confusion, disorientation, or decreased responsiveness.
What skin condition is associated with decreased cardiac output?
Cold, clammy skin
Results from poor circulation and reduced blood flow to the skin.
What color changes may occur in the skin and mucous membranes due to decreased cardiac output?
Color changes in the skin and mucous membranes
May include pallor or cyanosis.
What respiratory sound is indicative of decreased cardiac output?
Crackles (rales)
Often associated with fluid in the lungs.
What term describes difficulty in breathing that may occur with decreased cardiac output?
Dyspnea
Can result from fluid accumulation or decreased oxygenation.
What is a potential cardiac rhythm issue linked to decreased cardiac output?
Dysrhythmias
Irregular heartbeats that can further compromise cardiac function.
What symptom reflects a general lack of energy due to decreased cardiac output?
Fatigue
Can significantly affect a person’s daily activities.
What is the term for difficulty breathing while lying flat?
Orthopnea
Often indicates heart failure or severe respiratory issues.
What symptom may present as anxious behavior or agitation due to decreased cardiac output?
Restlessness
Can be a response to decreased oxygenation or perfusion.
