Middle Mediastinum and Heart

Question 0

How does the mediastinum extend (what are the borders of the mediastinum)?

Answer 0

Anterior-posterior from sternum to the vertebral bodies.

Superior-Inferior from the superior thoracic aperture to the diaphragm.

Question 1

Define Mediastinum

Answer 1

is a broad central partition that separates the two pleural cavities.

Question 2

What divides the mediastinum into superior and inferior components?

Answer 2

A transverse plane from sternal angle (junction b/n manubrium and body of the sternum) to the intervertebral disc between thoracic vertebrae IV and V

Question 3

What are the subdivisions of the inferior mediastinum?

Answer 3

Anterior
Middle
Posterior Regions

Question 4

Where is the anterior mediastinum located?

Answer 4

Anterior to pericardial sac and posterior to sternum

Question 5

What are the structure present in the anterior medistinum?

Answer 5

Thumus (is the major structure, but it involutes with age).
Fat
Connective Tissue
Lymph Nodes
Branches of the internal thoracic vessels
Sternopericardial ligaments

Question 6

What does the middle mediastinum contain?

Answer 6

It is centrally located and contains:

1) pericardium
2) heart
3) origin/termination of the great vessels: ascending aorta, pulmonary arteries, pulmonary veins, superior vena cava, inferior vena cava
4) phrenic nerves

Question 7

What is the pericardium? It is divided into ________ and _______

Answer 7

a sac surrounding the heart and roots of the great vessels. It has both
1) Fibrous Pericardium and 2) Serous Pericardium.

Question 8

_________tough CT that defines the boundaries of the middle medistinum. It is cone-shaped bag attached to the diaphragm at its base and continuous with the adventitia of the great vessels at its apex.

Answer 8

Fibrous Pericardium

Question 9

What is the course of the phrenic nerve and what does it innervate?

Answer 9

originate in the neck (C3-C5) travel b/n the lung (anterior to the root of the lung) and heart,pass through the fibrous pericardium, head to the diaphragm accompanied by pericardiacophrenic vessels. Sensory innervation to the fibrous pericardium, diaphragmatic peritoneum, mediastinal pleura. Motor innervation to diaphragm.

Question 10

The serous pericardium is divided into ________ and _______

Answer 10

Parietal: lines inner surface of pericardium
Visceral: adheres to the heart and forms its outer covering (epicardium)
Both layers are continuous at the roots of the great vessels. Otherwise, form the Pericardial Cavity b/n the 2 layers.

Question 11

What is an oblique pericardial sinus?

Answer 11

reflection of serous pericardium onto pulmonary veins. In general, these areas of continuity b/n 2 layers of serous pericardium around the great blood vessels create reflections of the serous pericardium

Question 12

What separates the atria from the ventricles? What separates left ventricle from right?

Answer 12

• Coronary sulcus

- Posterior Interventricular Sulcus and Anterior Interventricular Sulcus

Question 13

Where does blood enter the right atrium?

Answer 13

Superior vena cava
Inferior vena cava
Coronary sinus (returns venous blood from the walls of the heart itself)

Question 14

What is a cristae terminalis?

Answer 14

a smooth muscular ridge dividing the right atrium into a smooth muscle (developed earlier during embryology) and pectinate muscles.

Question 15

T/F Posterior to the cristae terminalis is pectinate muscles.

Answer 15

F. Posterior to cristae terminalis is a smooth walled portion of the atrium.

Question 16

What are pectinate muscles?

Answer 16

ridge shaped muscles anterior to the crista terminalis.

Question 17

What is the function of the foramen ovale in the fetus? What replaces it in the adult human?

Answer 17

allow blood to flow from the right to left atrium in the fetus bypassing the lungs which are non-functional. The fossa ovalis replaces it.

Question 18

Where does blood enter the right ventricle from?

Answer 18

from the right atrium (during atrial contraction) via the atrioventricular valves (tricuspid valves)

Question 19

The free margins of the three cusps of the tricuspid valve are attached to:

Answer 19

chordae tendinae which arise from tips of the papillary muscles.

Question 20

What are the function of papillary muscles?

Answer 20

Contraction of the papillary mm prevent cusps from prolapsing into the right atrium when the valves are close during ventricle contraction.

Question 21

What is the outflow of blood from the right ventricle?

Answer 21

the outflow tract is the conus arteriosus (infundibulum). At its apex the opening into the pulmonary trunk is closed by the pulmonary valve.

Question 22

In physiological orientation of the heart, what surface does the left atrium makeup?

Answer 22

Most of the base or posterior surface of the heart

Question 23

How many pulmonary veins are present? What is their function?

Answer 23

4, take oxygenated blood into the left atrium.

Question 24

T/F There is crista terminalis in the left atrium.

Answer 24

F. Similar to right atrium, left atrium has posterior portion of smooth muscles and anterior portion of pectinate muscles. But no crista terminalis separating them.

Question 25

What is the valve of foramen ovale?

Answer 25

In adults it is a thin depression in the interatrial septum which in development prevented backflow of blood from the left to the right atrium.

Question 26

What surfaces of the heart does the left ventricle contribute to?

Answer 26

anterior, diaphragmatic, and left pulmonary surfaces of the heart

Question 27

Where does blood enter the left ventricle from and where to does blood exit from the left ventricle?

Answer 27

Left atrioventricular orifice and exists via and otuflow tract called aortic vestibule.

Question 28

The rough, ridge like muscles in the walls of the left and right ventricles are:

Answer 28

Trabeculae carneae

Question 29

How are mitral valves connected to the papillary muscles?

Answer 29

The chordae tendinae connect the two cusps of mitral valve to the anterior and posterior papillary muscles.

Question 30

What are the 3 papillary muscle in the right atrium?

Answer 30

anterior papillary mm posterior papillary mm septal papillary mm

Question 31

T/F The cusps of the aortic valve are named posterior, right and left cusp.

Answer 31

T. Since the aorta in general is posterior to the pulmonary artery. The cusps of the pulmonary artery are anterior, right and left cusp.

Question 32

What are the cusps of the mitral valve and tricuspid valve respectively?

Answer 32

Mitral valve: anterior and posterior cusp | Tricuspid: anterior , posterior, and septal cusp

Question 33

Compare and contrast the pulmonary valve and aortic valve?

Answer 33

In both, the cusps form a pocket-like sinus and after ventricular contraction the recoil of blood fills the pulmonary and aortic sinuses and forces the cusps closed preventing back flow of blood from either filling the right or left ventricle. However, in the aortic valve when blood recoils after ventricular contraction and fills the aortic sinuses, the blood is forced into the coronary arteries (right and left) since these vessels originate from the right and left aortic sinuses.