Cardiovascular System Chapter 1: The Double Circulation

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Questions and Answers

What is the term used to describe the muscular ridges in the anterior wall of the right atrium?

Sinus venarum

Crista terminalis

Fossa ovalis

Musculi pectinati (correct)

What is the embryological origin of the posterior part of the atrial wall?

Same as the anterior part

Not specified in the content

Unknown

Different from the anterior part (correct)

What is the function of the coronary sinus?

Drains the upper part of the body

Drains the lungs

Drains the lower part of the body

Drains the heart itself (correct)

What is the remnant of the foramen ovale of the fetus?

Fossa ovalis Signup and view all the answers

What is the name of the node located at the upper end of the crista terminalis?

Sinu-atrial node Signup and view all the answers

What is the name of the vertical ridge that runs from the superior vena cava to the inferior vena cava?

Crista terminalis Signup and view all the answers

How many openings are there into the right atrium?

3 Signup and view all the answers

What is the shape of the musculi pectinati similar to?

A comb Signup and view all the answers

What is the primary function of the left side of the heart?

Pumping oxygenated blood to the various systems of the body Signup and view all the answers

What is the main artery that leaves the left side of the heart?

Aorta Signup and view all the answers

What is the characteristic of the blood carried by the aorta?

Oxygenated blood Signup and view all the answers

What is the main difference between the circulation in the fetus and the adult?

The direction of blood flow Signup and view all the answers

What is the learning outcome for this part of the lecture?

Give an account of the double circulation in the adult Signup and view all the answers

What is the division of the heart?

Into right and left sides Signup and view all the answers

What is the purpose of the double circulation in the adult?

To pump blood to the entire body Signup and view all the answers

What is the characteristic of the blood pumped by the right side of the heart?

Oxygen-poor blood Signup and view all the answers

What is the main characteristic of the left atrium internally?

It is entirely smooth-walled, except for the auricle Signup and view all the answers

What is the consequence of unequal division of the developing outflow tracts?

Tetralogy of Fallot Signup and view all the answers

How many cusps does the mitral valve have?

Two Signup and view all the answers

What is the difference between the left ventricle and the right ventricle?

The left ventricle is larger and has thicker walls Signup and view all the answers

What is the outlet of the left ventricle?

Aorta Signup and view all the answers

What is the characteristic of the auricle?

It is the only remnant of the original atrial chamber in the embryo Signup and view all the answers

What is the result of the endothelium of the pulmonary veins invading the left atrium during development?

The auricle is formed Signup and view all the answers

How many papillary muscles are typically present in the left ventricle?

Two Signup and view all the answers

What is the main function of the papillary muscles and chordae tendineae in the heart?

To prevent the cusps of the atrioventricular valve from blowing upwards into the atria during ventricular contraction Signup and view all the answers

What is the name of the bundle that passes from the interventricular septum to the anterior papillary muscle?

Moderator band (or septomarginal bundle) Signup and view all the answers

What is the term for the region of the septal wall close to the outflow tracts of the heart?

All of the above Signup and view all the answers

What is the most common type of atrial septal defect?

Probe patency Signup and view all the answers

What is the term for a hole in the heart that occurs in the muscular portion of the septum?

Ventricular septal defect (VSD) Signup and view all the answers

What is the term for a funnel-shaped region that directs blood out of the right ventricle via the pulmonary valve?

Infundibulum Signup and view all the answers

What is the term for a malformation of the aorta and pulmonary trunk that is often associated with a persistent interventricular foramen?

Tetralogy of Fallot Signup and view all the answers

What is the term for the complete absence of the inter-atrial septum?

Common atrium syndrome Signup and view all the answers

What percentage of blood enters the left atrium via the pressure gradient route?

80% Signup and view all the answers

What triggers the closure of both the foramen ovale and ductus arteriosus?

The first breath taken by the newborn Signup and view all the answers

What is the term used to describe the foramen ovale after birth?

Fossa ovalis Signup and view all the answers

What happens to the blood flow when the foramen ovale fails to close?

Oxygenated blood re-enters the pulmonary system Signup and view all the answers

Approximately what percentage of the population has probe patency?

20% Signup and view all the answers

What is the consequence of a patent ductus arteriosus?

Blood flows from the aorta to the pulmonary arteries Signup and view all the answers

What happens to the ductus arteriosus after birth?

It shrivels and fibroses to form the ligamentum arteriosum Signup and view all the answers

What is the term used to describe the condition where the foramen ovale fails to close?

Patent foramen ovale Signup and view all the answers

Study Notes

The Heart Chambers and the Double Circulation

The Systemic Circulation

The heart is divided into a right side and a left side.
The left side pumps blood to the various systems of the body, but not to the lungs.
The main artery to leave the left side of the heart is the aorta, which carries oxygenated blood.

Right Atrium

The right atrium has an earlobe or auricle that lies in front of the 1st part of the aorta.
The anterior wall of the right atrium is composed of muscular ridges called musculi pectinati.
These ridges arise from a vertical ridge called the crista terminalis.
The cristae terminalis has an important part of the electrical conducting system of the heart, the sinu-atrial node.
The wall behind the crista terminalis is smooth and is known as the sinus venarum.
There are three openings into the right atrium: SVC, IVC, and the coronary sinus.

Right Ventricle

The region of the septal wall close to the outflow tracts of the heart is smooth, and this reflects the membranous portion of the fetal heart septum.
In the adult, this is called the conus arteriosus or infundibulum.
The infundibulum serves to direct the blood out of the right ventricle via the pulmonary valve.
Ventricular septal defects (VSDs) can occur in this area if it fails to develop properly.

Atrial Septal Defects (ASD's)

ASD's can also occur and are fairly common, with approximately 20% of the population having a small patent foramen ovale called a probe patency.
More serious conditions include large deficiencies in the septum and hence a large patent foramen ovale.
Sometimes a complete absence of the inter-atrial septum is seen, which is called common atrium syndrome.

Tetralogy of Fallot

A persistent interventricular foramen is usually associated with a malformation of the aorta and pulmonary trunk.
One such condition is known as tetralogy of Fallot, which occurs when the developing outflow tracts divide unequally.
This condition is characterized by a narrow pulmonary trunk (called a pulmonary infundibular stenosis), a defect in the interventricular septum, an “over-riding” aorta, and a hypertrophied right ventricle.

Left Atrium

The left atrium receives the pulmonary veins, carrying oxygenated blood from the lungs.
It is entirely smooth-walled internally, except for the auricle.
The auricle is the only remnant of the original atrial chamber in the embryo.

Left Heart

The valve between the left atrium and the left ventricle is the mitral valve, which is a bicuspid valve.
The anatomical features of the left ventricle are similar to those of the right, except the left ventricle is larger and has thicker walls.
There is no moderator band in the left ventricle.
There are usually only two papillary muscles, and it lacks septal papillae that are a feature of the right ventricle.

Fetal Circulation

Blood is oxygenated in the placenta.
At birth, the lung beds open suddenly as the first breath is taken.
The pulmonary system pressure drops, and this triggers a closure of both the foramen ovale and ductus arteriosus.
The foramen ovale is then known as the fossa ovalis, and the ductus arteriosus shrivels and fibroses to form the ligamentum arteriosum.

Patent Fetal Circulation in Newborn

Occasionally, the foramen ovale fails to close, which is known as “patent foramen ovale” if large, or “probe patency” if small.
When this occurs, the pressure gradient is such that the systemic system is at a higher pressure than the pulmonary system, and blood flows from left to right.
This can cause oxygenated blood to re-enter the pulmonary system instead of being distributed to the body tissues that need it.

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Description

Learn about the double circulation and heart chambers in the cardiovascular system. This lecture covers the basics of the heart's structure and function.