Heather's Anatomy Notes Flashcards
The embryonic heart begins as a straight tube with one-way blood flow. What are the input and output ends of this tube?
Sinus venosus is the input end of the heart tube
Truncus arteriosus is the output end of the heart tube The heart initially develops outside the body, and folds in order to fit into the thoracic cavity
Subdivision of the embryonic heart tube produces chambers. Which septa create the chambers?
Septum primum subdivides the atria, leaving an open portion (osmium premium)
Septum secundum then covers the foramen primum, leaving an opposing open portion (foramen ovale)
Septum primum becomes a flap covering foramen ovale, with a second opening in it (foramen secundum), which fuses shut after birth
The interventricular septum grows outward to divide the ventricles and has both muscular and membranous components
How does ventricular septal defect occur?
Ventricular septal defect: the membranous portion of the ventricular septum is often incomplete; these are the most common type of congenital anomalies of the heart. Causes pulmonary hypertension, because SV decreases, causing imbalance
How does atrial septal defect occur?
Incomplete closure of the foramen ovale after birth is the most common problem leading to an atrial septal defect; can cause enlargement of the right atrium, because blood from the LA flows back into the RA
Where do the great vessels of the heart (and most circulation of the head) arise from?
Great vessels of the heart arise from the embryonic pharyngeal arches
What is the ductus arteriosus, and what embryonic structure does it arise from?
The ductus arteriosus is one of the left-right shunts in the heart during fetal circulation; it arises from the sixth pharyngeal arch artery
Where do the large veins around the heart come from?
The large veins around the heart develop through remodeling of the cardinal veins
Clinical Correlation: Variants in the Great Vessels
Most variation in the pattern of the great vessels is asymptomatic
Some variants, such as double aortic arches, have serious clinical consequences including compression of the esophagus and trachea
List the 5 shunts and additional circulatory structures that exist in fetal circulation, and what they become in adult circulation
- Foramen ovale –> fossa ovalis
- Umbilical vein (intra-abdominal part) –> ligamentum teres
- Ductus venosus –> ligamentum venosum
- Umbilical arteries and abdominal ligaments –> medial umbilical ligaments, superior vesical artery (supplies bladder)
- Ductus arteriosus –> ligamentum arteriosum
Failure of the fetal circulation to remodel results in adult presence of some fetal elements, which may or may not have clinical consequences
What are the functional compartments of the thorax?
And the subdivisions of the mediastinum?
Mediastinum:
- Heart
- Trachea
- Great vessels
- Esophagus
Pulmonary cavities:
- Lungs
The mediastinum can be further divided into superior, inferior, anterior, middle, and posterior compartments.
The heart and great vessels lie in the middle mediastinum
The heart and pericardial cavity are lined by a membrane called the pericardium. What are the layers of this membrane?
- Fibrous pericardium; continuous with the central tendon of the diaphragm and forming the external inelastic layer
- Parietal serous pericardium; lines the fibrous pericardium
- Visceral serous pericardium; continuous with the parietal pericardium, but lying directly on the heart
- Pericardial cavity is the space between the two layers of the serous pericardium
Clinical Correlation: Cardiac Tamponade
Heart compression occurs when the pericardial cavity fills with fluid, because the fluid is not compressible.
Perforating wounds, as well as blood leakage following an MI, result in hemopericardium - blood in the pericardial cavity
The sudden increase in fluid results in increased pressure in teh pericardial cavity, and reduction of heart volume. Decreases SV and cardiac output.
Three layers of the walls of the heart
Endocardium: innermost endothelial layer
Myocardium: middle layer consisting of helical cardiac smooth muscle
Epicardium: outermost layer, equivalent to the visceral serous pericardium
What are the different thicknesses of the atria and ventricles of the heart?
RA: 1-2 mm thick, low pressure
LA: 1-2 mm thick, low pressure
RV: 5-10 mm thick, low pressure
LV: 15-30 mm thick, high pressure
Clinical Correlation: Ventricular hypertrophy
What conditions lead to hypertrophy of the LV?
Conditions in which the heart has to work harder to overcome resistance in the circulation lead to hypertrophy of the ventricles:
- Aortic stenosis
- Systemic HTN
- Pulmonary valve stenosis
- Pulmonary arterial hypertension (COPD, altitude, etc)
What are the 3 functions of the fibrous skeleton of the heart?
- Supports the valves of the heart
- Insulates the atria from the ventricles
- Provides an anchor point for the muscle fibers
What are the auricles of the heart?
The auricles are muscular sacs that increase the capacity of the atria
What are the great vessels of the heart?
The aortic arch, pulmonary trunk, and pulmonary arteries and veins
The superior and inferios vena cava
How does blood get into and out of the right atrium?
Blood enters the RA through the superior/inferior vena cava, and the coronary sinus.
Blood exits the RA through the right AV valve (tricuspid valve)
How does blood leave the right ventricle?
And where does that blood go?
Blood leaves the RV through the pulmonary semi-lunar valve, and the pulmonary trunk.
This blood goes to the lungs via pulmonary circulation.
How does blood get into and out of the left atrium?
Blood enters the LA through the 4 pulmonary veins
Blood leaves the LA through the left AV valve (mitral valve, bicuspid valve)
How does blood leave the left ventricle?
And where does that blood go?
Blood leaves the LV throught the aortic semi-lunar valve, and the aortic arch
This blood leaves through the aorta, and goes out into systemic circulation to supply blood to the entire body
Clinical Correlation: Heart murmur
What is a heart murmur?
What can cause a murmur?
A heart murmur is the sound caused by rapid or turbulent blood flow across the valves in the heart. It may be heard on systole or diastole, and in different positions on the thorax.
Types of murmurs:
Stenosis: narrowing of valves or vessels
Atrial or ventricular septal defects
May be benign, especially if found in a younger person.
What two arteries are the first branches off the ascending aorta?
And which one is the dominant one?
The RCA and LCA are the first branches off the aorta, and whichever one gives rise to the posterior interventricular (descending) branch is the dominant branch
RCA dominance is more common, occuring in 67% of people
What are the branches that come off of the right coronary artery?
And what areas does the RCA supply?
The RCA gives off, in order:
- Sinoatrial nodal branch
- Atrioventricular nodal branch
- Posterior interventricular branch
- Interventricular septal branch
The RCA typically supplies the RA, most of the RV, diaphragmatic surface of the LV, posterior third of the interventricular septum, the SA node, and the AV node.