Human Anatomy: Heart Location and Position

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Questions and Answers

What is the approximate weight of the heart in females?

250g (correct)

350g

200g

300g

Where is the heart located in relation to the midline of the body?

Exactly in the middle of the chest

One third to the left and two thirds to the right of the midline

Entirely to the left of the midline

One third to the right and two thirds to the left of the midline (correct)

What defines the upper border of the heart's surface anatomy?

A straight line joining specific costal cartilage points (correct)

An irregular shape formed by the pericardium

A curved line following the diaphragm

A diagonal line from the sternum to the spine

What is the position of the heart relative to the diaphragm?

It is located superior to the diaphragm Signup and view all the answers

What anatomical feature is described as the fibrous skeleton of the heart?

Dense connective tissue that provides structure Signup and view all the answers

What are the small veins that open into all four chambers of the heart called?

Venae cordis minimi Signup and view all the answers

What is the appearance of the muscular ridges called in the rough anterior part of the right ventricle?

Trabeculae carneae Signup and view all the answers

What is the correct name for the left atrioventricular valve?

Bicuspid valve Signup and view all the answers

Which structure represents the site of the embryonic septum primum?

Fossa ovalis Signup and view all the answers

Which part of the right ventricle is responsible for smooth outflow of blood towards the pulmonary trunk?

Smooth part/ Infundibulum Signup and view all the answers

What type of tissue strengthens the cusps of heart valves?

Fibrous tissue Signup and view all the answers

What separates the inflowing rough part and the outflowing smooth part of the right ventricle?

Supraventricular crest Signup and view all the answers

Where does most of the oxygen-rich blood from the placenta go before entering the right atrium?

Through the ductus venosus Signup and view all the answers

What happens to blood in the right atrium during fetal circulation?

It is guided toward the oval foramen. Signup and view all the answers

Which orifice in the right ventricle is guarded by the tricuspid valve?

Right atrioventricular orifice Signup and view all the answers

What is the function of the ductus arteriosus during fetal life?

To allow blood to flow from the pulmonary trunk into the descending aorta. Signup and view all the answers

What type of muscular ridges are known as septomarginal trabeculae in the inflowing part of the right ventricle?

Ridges Signup and view all the answers

What percentage of oxygen saturation is found in the umbilical arteries?

58% Signup and view all the answers

What signifies the free edge of the septum secondum?

Annulus fossa ovalis Signup and view all the answers

Which of the following structures plays a critical role in guiding placental blood to the left atrium?

Valve of the inferior vena cava Signup and view all the answers

Which valve is known to have three cusps?

Both B and C Signup and view all the answers

What primarily forms the apex of the heart?

Left ventricle Signup and view all the answers

Which surface of the heart is primarily formed by the left ventricle?

Left surface Signup and view all the answers

What feature is associated with the upper border of the heart?

Formed by the left atrium mainly Signup and view all the answers

The posterior interventricular groove is situated on which surface of the heart?

Inferior surface Signup and view all the answers

Which statement correctly describes the lower border of the heart?

Nearly horizontal and mainly by the right ventricle Signup and view all the answers

Where is the interatrial groove predominantly located?

Faintly visible posteriorly but hidden anteriorly Signup and view all the answers

What primarily forms the base of the heart?

Left atrium and part of right atrium Signup and view all the answers

What is the function of the sulcus terminalis in the right atrium?

Contains the sinoatrial (SA) node Signup and view all the answers

Which groove marks the separation of the apex from the inferior border of the heart?

Anterior interventricular groove Signup and view all the answers

Which structure is not part of the interior of the right atrium?

Pulmonary veins Signup and view all the answers

What is the function of the Eustachian valve?

To guide blood to the left atrium during embryonic life Signup and view all the answers

Which part of the right atrium contains musculi pectinati?

Rough anterior part Signup and view all the answers

What structure opens between the inferior venacava and the right atrioventricular orifice?

Coronary sinus Signup and view all the answers

Which part of the right atrium is referred to as the sinus venarum?

Smooth posterior part Signup and view all the answers

Study Notes

Location and Position of the Heart

The heart is a conical muscular organ located in the middle mediastinum within the pericardium.
The heart is situated superior to the diaphragm, left of the midline, anterior to the vertebral column, and posterior to the sternum.
The weight of the heart is approximately 300g in males and 250g in females.
The heart is about the size of a fist.

Position of the Heart

The heart is positioned obliquely behind the body of the sternum and adjacent costal cartilages.
One-third of the heart lies to the right, while two-thirds lie to the left of the median plane.

Surface Anatomy of the Heart

The upper border of the heart is marked by a straight line joining a point at the lower border of the second left costal cartilage and a point at the upper border of the third right costal cartilage.
The lower border of the heart is marked by a straight line joining a point at the lower border of the sixth right costal cartilage and the anterior interventricular groove.
The anterior interventricular groove is situated nearer to the left margin of the heart and separates the apex from the rest of the inferior border.
The posterior interventricular groove is found on the inferior surface of the heart.
The two interventricular grooves meet at the inferior border of the heart near the apex.

Grooves/Sulci of the Heart

The interatrial groove is faintly visible posteriorly while hidden by the aorta and pulmonary trunk anteriorly.

Apex of the Heart

The apex is formed entirely by the left ventricle.
It is directed downwards, forwards, and to the left.
It is situated in the left 5th intercostal space, 9cm lateral to the mid-sternal line, just medial to the midclavicular line.

Base of the Heart

The base, also known as the posterior surface, is mainly formed by the left atrium, with a small part of the right atrium.
The left atrium has openings for four pulmonary veins.
The right atrium receives the superior and inferior vena cava.

Borders of the Heart

The heart has an upper, lower, right, and left border.
The upper border, slightly oblique, is formed by both atria, primarily the left atrium.
The right border is more or less vertical and formed by the right atrium.
The lower border, nearly horizontal, is primarily formed by the right ventricle, with a small part near the apex formed by the left ventricle.
The left border, oblique and curved, is mainly formed by the left ventricle, with a partial contribution from the left auricle.

Surfaces of the Heart

The heart has an anterior/sternocostal, inferior/diaphragmatic, left, and posterior/base surface.
The anterior/sternocostal surface is primarily formed by the right atrium and right ventricle, with partial contributions from the left ventricle and left auricle.
The inferior/diaphragmatic surface rests on the central tendon of the diaphragm and is formed by the left ventricle on the left 2/3rd and the right ventricle on the right 1/3rd.
The left surface is predominantly formed by the left ventricle, with a small part near the upper end formed by the left auricle.

Right Atrium

The right atrium is the upper chamber of the heart.
It receives venous blood from the entire body through the superior and inferior vena cava.
It pumps venous blood into the right ventricle through the right atrioventricular or tricuspid opening.
External features include a right auricle formed by the upper end prolongation and the sulcus terminalis, a shallow vertical groove on the right border that extends from the SVC to the IVC.
The sulcus terminalis is produced by the crista terminalis, a muscular ridge in the interior.
The upper part of the sulcus terminalis contains the SA (sinu atrial) node, the pacemaker of the heart.

Tributaries/Inlets of the Right Atrium

The right atrium receives blood from the following:
- Superior vena cava
- Inferior vena cava
- Coronary sinus
- Anterior cardiac veins
- Venae cordis minimi (Thebesian veins)

Interior of Right Atrium

The interior of the right atrium is divided into three parts:
- Smooth posterior part (sinus venarum)
- Rough anterior part (pectinate part, including the auricle)
- Interatrial septum

Smooth Posterior Part

The smooth posterior part receives blood from the:
- Superior vena cava at the upper end
- Inferior vena cava at the lower end
  - The inferior vena cava opening is guarded by a valve (Eustachian valve).
  - During embryonic development, the Eustachian valve guides the inferior vena caval blood to the left atrium through the foramen ovale.
- Coronary sinus
  - This opening is located between the opening of the inferior vena cava and the right atrioventricular orifice.
  - The coronary sinus opening is guarded by the valve of the coronary sinus.
- Venae cordis minimi are small veins that open into all four chambers.

Rough Anterior Part

The rough anterior part is characterized by transverse muscular ridges called Musculi pectinati (resembling teeth of a comb).

Interatrial Septum

The interatrial septum has features like:
- Fossa ovalis: A shallow saucer-shaped depression in the lower part that represents the site of the embryonic septum primum.
- Annulus fossa ovalis/ limbus fossa ovalis: The margin of the fossa ovalis, representing the free edge of septum secundum.

Right Ventricle

The interior of the right ventricle is divided into two parts:
- Inflowing rough part: Contains muscular ridges called trabeculae carneae.
- Outflowing smooth part/ Infundibulum: The upper conical part of the right ventricle, giving rise to the pulmonary trunk.
These two parts are separated by a muscular ridge called the SUPRAVENTRICULAR CREST situated between the tricuspid (right atrioventricular orifice) and pulmonary orifice.
The right ventricle has two orifices:
- Right atrioventricular orifice: Guarded by the tricuspid valve.
- Pulmonary orifice: Guarded by the pulmonary valve.
The inflow rough part contains three types of trabeculae carneae or muscular ridges:
- Ridges (septomarginal trabeculae/ moderator band)
- Bridges
- A pair of semilunar valves
Important valvular notes:
- The right atrioventricular valve is called the tricuspid valve due to its three cusps.
- The left atrioventricular valve is called the bicuspid valve due to its two cusps.
- Semilunar valves include the aortic and pulmonary valves, both having 3 semilunar cusps.
- Cusps are folds of endocardium strengthened by fibrous tissues.

Fetal Circulation

Before birth, blood from the placenta, about 80% saturated with oxygen, returns to the fetus through the umbilical vein.
Most of the blood flows through the ductus venosus directly into the inferior vena cava, bypassing the liver.
A smaller amount enters the liver sinusoids and mixes with blood from the portal circulation.
The blood enters the right atrium, where it is guided towards the oval foramen by the valve of the inferior vena cava, and most of the blood passes directly into the left atrium.
In the left atrium, blood mixes with a small amount of desaturated blood returning from the lungs and enters the left ventricle and ascending aorta.
Desaturated blood from the superior vena cava flows through the right ventricle into the pulmonary trunk.
During fetal life due to high resistance in the pulmonary vessels, most of the blood passes through the ductus arteriosus directly into the descending aorta, mixing with blood from the proximal aorta.
Blood flows towards the placenta through two umbilical arteries.
The oxygen saturation in these arteries is approximately 58%.

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Description

This quiz covers the anatomical location and positioning of the heart within the mediastinum. It examines key features such as its size, weight, and surface anatomy. Test your understanding of where the heart is situated relative to other body structures.