Heart and Mediastinum Flashcards
What makes up the superior boundary of the mediastinum?
Thoracic inlet
What is the inferior boundary of the mediastinum?
Diaphragm
What makes up the anterior boundary of the mediastinum?
Sternum and costal cartilages
What makes up the posterior boundary of the mediastinum?
Thoracic vertebrae
What makes up the lateral boundary of the mediastinum?
Pleura
What divides the mediastinum into superior and inferior parts?
Horizontal line from the manubriosternal joint to the T4/T5 Intervertebral joint
What is the inferior Mediastinum divided into?
Anterior, middle, and posterior
What are the contents of the superior mediastinum?
Great vessels of the heart Thoracic duct (left) Part of the azygos system R&L vagus nerves (recurrent laryngeal nerves) Pulmonary Esophageal and cardiac autonomic nerve plexuses Thymus Parts of trachea and esophagus
What are the contents of the Inferior Anterior mediastinum?
Fat, lymph tissue, vessels, and in small children the thymus may extend into this region
What are the contents of the inferior middle mediastinum?
The heart and it’s pericardial tissues
What are the contents of the inferior posterior mediastinum?
Thoracic aorta esophagus pulmonary arteries & veins Azygos system Thoracic Duct Sympathetic trunk & thoracic splanchnic nerves
Which brachiocephalic vein is longer?
Left
Describe the thoracic sympathetic trunk
Bilateral; continuous with cervical and lumbar parts of sympathetic trunk
Paravertebral ganglia along its course
Lateral to the vertebral bodies
Describe thoracic splanchnic nerves
Bilateral; emerge from thoracic sympathetic trunks
Greater, lesser, least
All three are part of the abdomnopelvic splanchnic nerves and provide sympathetic innervation to viscera inferior to the diaphragm
All are PREsynaptic fibers that will synapse with prevertebral ganglia in abdomen
What are areas of constriction?
Arch of aorta, left main bronchus, and diaphragm.
These are where swallowed foreign objects are most likely to lodge and where a stricture may develop
What is the center of the cardiovascular system?
The heart
What does the heart connect to to transport blood between the heart and other body tissues?
Blood vessels
What are arteries?
Vessels that carry blood away from the heart
What are veins?
Vessels that carry blood back to the heart
What type of blood do arteries carry?
Blood high in oxygen except the pulmonary arteries
What type of blood do veins carry?
Blood in low oxygen except pulmonary veins
What are the great vessels?
The arteries and veins entering and leaving the heart
What does the structure of the heart ensure?
Ensures the unidirectional flow of blood through both the heart and the blood vessels
What is backflow of blood prevented by?
Valves within the heart
What does the heart act like?
Acts like two independent, side-by-side pumps that work independently but at the same rate
What does the right heart pump do?
Directs blood to the lungs for gas exchange
What does the left heart pump do?
Directs blood to body tissues for nutrient delivery
How is blood pressure developed?
Through alternate cycles of heart wall contraction and relaxation
How much blood pressure is essential to push blood through blood vessels to the body tissues for nutrient and waste exchange?
Minimum blood pressure
What is the base of the heart?
Left atrium primarily
Thinking about pulmonary circulation, the “systemic” pathway of this circuit involves which parts of the heart?
Left atrium and pulmonary veins: the start of the systemic circulation that has oxygenated blood that will go to the body
What does the pulmonary circuit consists of?
The chambers on the right side of the heart (right atrium and ventricle) as well as the pulmonary arteries and veins
What is the main function of the pulmonary circuit?
Convey blood to the lungs via pulmonary arteries to reduce carbon dioxide and replenish oxygen levels in the blood before returning to the heart in pulmonary veins
When does blood first enter the systemic circuit?
When blood returns to the left side of the heart
What does the systemic circuit consists of?
Chambers on the left side of the heart along with all the other named blood vessels
What is the main function of the systemic circuit?
Carries blood to all the peripheral organs and tissues of the body
What is the largest systemic artery in the body?
The aorta
Where does gas exchange occur?
Capillaries
Where do most veins merge and drain into?
The superior and inferior vena cavae
Thinking about position of the heart in the mediastinum, which of the following heart structures is located more posteriorly, and makes up most of what is called the "base" of the heart? A. Right atrium B. Right ventricle C. Left atrium D. Left ventricle
C. Left atrium
What is the approximate size of a heart?
The relatively small, conical organ is approximately the size of a person’s clenched fist and weighs about 250 to 350 grams
What is the heart’s position in the body?
Left of the body midline posterior to the sternum in the middle mediastinum
Rotated such that its right side or border is located more anteriorly, while its left side or border is located more posteriorly
Where is the superior part of the heart relative to the ribs?
At the third ribs
Where is the apex of the heart relative to the ribs?
At the six ribs
Where is the aortic arch relative to the ribs?
At the manubriosternal joint
What is the base of the heart?
The posterosuperior surface of the heart, formed primarily by the left atrium
What borders the base of the heart?
The pulmonary veins that enter the left atrium
What is the inferior, conical end of the heart?
Apex
Where does the apex project?
Slightly anteroinferiorly towards the left side of the body
The pericardium of the heart has three primary layers. If the pericardium of the heart is pierced by a needle, which of these primary layers would the needle first pass through? A. Visceral pericardium B. Pleural pericardium C. Parietal pericardium D. Fibrous pericardium E. Epicardium
D. Fibrous pericardium
What is the heart contained in?
A fibrous, serous sac held in place within the mediastinum by connective tissue that supports the great vessels’ external walls superior to the heart and the diaphragm inferior to it
What does the pericardium restrict?
Restricts heart movements so that it doesn’t bounce and move about in the thoracic cavity, and prevents the heart from overfilling with blood
What is the outer portion of the pericardium?
A tough, dense connective tissue layer called the fibrous pericardium that is attached to both the sternum and the diaphragm
What is the inner portion of the pericardium?
A thin, double-layered serous membrane called the serous pericardium.
What are the two layers of the inner portion of the pericardium?
Parietal layer and visceral layer
What are the three distinctive layers of the heart wall?
External epicardium, middle myocardium and internal endocardium
What is the outermost heart layer? What is it also known as?
Epicardium and is also known as the visceral layer of serous pericardium
As we age, what is deposited in the epicardium?
Fat-this layer becomes thicker and more fatty
What is the middle layer of the heart wall?
The myocardium that is composed chiefly of cardiac muscle tissue
Lies deep to the epicardium and superficial to the endocardium
What is the thickest of the three heart wall layers?
The myocardium
What are covered by a thin endothelium called the endocardium?
Internal surface of the heart and external surfaces of the heart valves
What is between the endocardium and myocardium?
Subendocardial layer, which is composed of areolar connective tissue
What are the four hollow chambers of the heart?
Two smaller atria and two larger ventricles
What are atria chambers?
thin-walled chambers that are located superiorly.
What are located anteriorly on each atrium?
A wrinkled, flaplike extension called an auricle
What exits the heart at the basal surface?
Two large arteries, the pulmonary trunk and the aorta
What does the pulmonary trunk carry blood to?
Carries blood from the right ventricle into the pulmonary circuit
What does the aorta carry blood to?
Carries blood from the left ventricle into the systemic circuit
What separates the atria from the ventricles externally?
A relatively deep coronary sulcus (or atrioventricular sulcus) that extends around the circumference of the heart
What are located between the left and right ventricles?
The anterior interventricular sulcus and the posterior interventricular sulcus
Where do the interventricular sulci extend?
Inferiorly from the coronary sulcus towards the heart apex
Which of the following heart structures is framework of dense collagen that anchors and provides support for the antrioventricular and semilunar valves of the heart? A. Chordae tendineae B. Papillary muscle C. Fibrous skeleton D. Fossa ovalis
C. Fibrous skeleton
What is between the atria and the ventricles, and is formed from dense irregular connective tissue?
Fibrous heart skeleton
What are the functions of fibrous heart skeleton?
- Separates the atria and ventricles
- Anchors heart valves by forming supportive rings at their attachment points
- Provides electrical insulation between atria and ventricles
What does insulation from the fibrous skeleton of the heart ensure?
Insulation ensures that muscle impulses are not spread randomly throughout the heart, and thus prevents all of the heart chambers from beating at the same time
What does the Fibrous skeleton of the heart provide?
Rigid framework for the attachment of cardiac muscle tissue
What do the four heart chambers play a role in?
The continuous process of blood circulation
What do valves permit?
The passage of blood in one direction and prevents its backflow
What three major vessels empty into the right atrium?
- Superior vena cava drains blood from the head, upper limbs, and superior regions of the trunk
- Inferior vena cava drains blood from the lower limbs and trunk
- Coronary sinus drains blood from the heart wall
What forms a wall between the right and left atria?
Interatrial septum
What is remnant in the interatrial septum?
The foramen ovali that is called fossa ovalis in the adult
What muscle does the right atrium have on the internal aspects of the wall?
The pectinate muscle
What separates the right atrium from the right ventricle?
The right AV valve
What is another name for the right atrioventricular valve?
Tricuspid valve - has three triangular flaps
When does the tricuspid valve close?
It is forced closed when the right ventricle begins to contract, preventing blood blackflow into the right atrium
What forms a wall between the right and left ventricles?
Interventricular septum
What does the internal wall surface of each ventricle have?
Two (Left) or Three (right) cone-shaped, muscular projections called papillary muscles,
What is the function of papillary muscles?
Anchors chordae tendineae.
What is the function of chordae tendineae?
Attach to the cusp of the right AV valve and prevent everting and flipping into the atrium when contracting
Where are trabeculae carneae?
Ventricles
The ligamentum arteriosum, a fetal remnant of the ductus arteriosis, is located where?
Between the pulmonary trunk and aorta
At the superior end of the pulmonary trunk, it narrows into a smooth-walled, conical region called the _______
Conus arteriosus
What marks the end of the right ventricle and the entrance into the pulmonary trunk?
The pulmonary semilunar valve
What does the pulmonary trunk divide shortly into?
Right and left pulmonary arteries
What is located within the walls of both ventricles immediately before the connection of the ventricle to the pulmonary trunk and aorta?
Semilunar valves
What are semilunar valves composed of?
Three thin, pocketlike semilunar cusps
How do semilunar valves open?
As blood is pumped into the arterial trunks, it pushes against the cusps, forcing the valves open
How is blood prevented from flowing back into the ventricles from the arterial trunk?
When ventricular contraction ceases, the blood first enters the pockets of the semilunar valves between the cusp and the chamber wall; this causes the cusps to “inflate” and meet at the artery center, effectively blocking blood backflow
The smooth posterior wall of the left atrium contains how many openings for oxygenated blood return?
Four pulmonary veins
The right atrium has pectinate muscle along its wall, does the left atrium have pectinate muscle?
It has some pectinate muscles along its anterior wall as well as an auricle
What separates the left atrium from the left ventricle?
The left AV valve
What is the left AV valve also called?
The bicuspid or mitral valve
True or false?
The left AV valve has different chordae tendineae than those of the right AV valve?
False
When does the left AV valve close?
It is forced closed when the left ventricle begins to contract; this prevents backflow
What is the largest of the four heart chambers?
The left ventricle
How much thicker is the wall of the left ventricle than the right ventricular wall?
three times thicker
Why does the left ventricle have thick walls?
It requires thick walls in order to generate enough pressure to force the oxygenated blood from the lungs into the aorta and then through the entire systemic circuit
Why does the right ventricle not need thick walls?
Because it only has to pump blood to the nearby lungs
Where is trabeculae carneae more prominent?
In the left ventricle
What helps support the left AV valve?
Two large papillary muscles attached to the chordae tendineae
What marks the end of the left ventricle and the entrance into the aorta at the superior end of the ventricular cavity?
The aortic semilunar valve
What is the heart innervated by?
The autonomic nervous system. Both sympathetic and parasympathetic components
Referred to as the cardiac or coronary plexus
What does sympathetic innervation going to do to the heart?
Increase the heart rate an the force of heart contractions
What does parasympathetic innervation do to the heart?
Decreases heart rate, but tends to have no effect on the force of contractions, except in special circumstances
What do left and right coronary arteries travel in?
The coronary sulcus (atrioventricular groove) of the heart
What are the only brances of the ascending aorta that go to supply the heart wall?
The left and right coronary arteries
Where are the openings for the left and right coronary arteries located?
Immediately superior to the aortic semilunar valve
What does the right coronary artery typically branch into? What do the branches supply?
The marginal artery-supplies the right border of the heart
Posterior interventricular artery-supplies both the left and right ventricles
What does the left coronary artery typically branch into?
What does it supply?
The anterior interventricular artery
- Also called the left anterior descending artery (LAD)
- Supplies the anterior surface of both ventricles and most of the interventricular septum
Circumflex artery
-Supplies the left atrium and ventricle
What can vary greatly among individuals?
Arterial pattern
What acts as the pacemaker of the heart?
The sinoatrial (SA) node
Where is the SA node located?
In the posterior wall of the right atrium, adjacent to the entrance of the superior vena cava
Where is the atrioventricular (AV) node located?
The floor of the right atrium between the right AV valve and the coronary sinus.
(Antriaventricular septa)
Cardiac impulse starts at the SA node and then travels where?
Travels to the AV node -> atrioventricular bundle (bundle of His)->purkinje fibers
The main tributary of the coronary sinus is the: A. Great cardiac vein B. Middle cardiac vein C. Great vein of Galen D. Small cardiac vein
A. Great cardiac vein
The right coronary artery typically branches into the: A. Marginal artery B. Anterior interventricular artery C. Lateral anterior descending artery D. Circumflex artery
A. Marginal artery
What three venous structures drain directly into the right atrium?
Superior vena cava, inferior vena cava and coronary sinus
What is cardiomyopathy?
A condition in which a ventricle has become enlarged, thickened and/or stiffened. As a result, the heart’s ability to pump is reduced.
What are the two types of cardiomyopathy?
Dilated: An enlarged, weakened left ventricle struggles to pump enough blood to meet the body’s need
Hypertrophic: Left ventricle cannot fully relax between heartbeats, resulting in less blood flow
What is coronary artery bypass?
When the internal mammary artery is used to supply the heart when there are sites of blockage due to cholesterol build-up
What other vessel can be used if there are sites of blockage to the heart?
The saphenous vein
What is angioplasty?
A procedure in which a catheter is inserted with a tiny balloon that presses the plaque blockage against the artery so that blood may flow more freely through a vessel. A stent is then inserted to keep the vessel pathway open and the blood flowing
What can cause an heart attack?
A blood clot and cholesterol plaque causes an obstruction of coronary artery supplying blood to the heart muscle and heart muscle dies.
