The Thorax

Question 1

What is the Septum Primum

What is the Septum Secondum and its importance

Answer 1

Septum primum is a membrane in the heart formed in embryology that creates the foramen Ovale.
The septum secondum is a second membrane to the right of the foramen Ovale which acts as a one way valve allowing blood from right to left

Question 2

How does the Foramen Ovale

Answer 2

At birth, blood flow to the lungs increases the pressure in the left Atria, forcing the Septum Primum through the Foramen Ovale to close it.

Question 3

What does the Sinus Venosus Form in the Heart

Answer 3

The Superior and Inferior Vena Cava, and Four Pulmonary Veins

Question 4

How many pairs of arches are given off by the Truncus Arteriosus in cardiac embryology
What do each Pair Form

Answer 4

6 Pairs

Pairs 1,2 and V completely Vanish

3rd Arches create the common carotid arteries
4th Arches forms the Subclavian Arteries
6th Arches form the pulmonary arteries - and the connection to the Aorta called the Ductus Arteriosus (on the left)

Question 5

How do the Recurrent Laryngeal Nerves correlate to the aortic arches

Answer 5

Right Recurrent Laryngeal Nerve is hooked under the Subclavian Artery as 5th and 6th Arches Disappear on the Right.

Left Recurrent Laryngeal Nerve is hooked under the 6th Arch (Ligamentum Arteriosum - remnant of the Ductus Arteriosus)

Question 6

What is the Function of the Ductus Venosus

Answer 6

Enables blood from the placenta to bypass the foetal liver

Question 7

What defects can cause an Atrial Septal Defect

Answer 7

Ostium Primum
Ostium Secundum
Type depends on which septum failed to fuse

Question 8

What is the consequence of a patent ductus arteriosus

Answer 8

Increased left ventricular load

Increased pulmonary hypertension

Question 9

What is Eisenmenger’s Syndrome

Answer 9

Cyanosis secondary to right to left shunting through a PDA, ASD, VSD caused by increased pulmonary hypertension

Question 10

What are the causes of a right to left shunt

Answer 10

Tetralogy of Fallot

ASD, VSD, PDA in presence of pulmonary hypertension

Question 11

What are the four features of Fallot’s Tetralogy

Answer 11

VSD
Overriding Aorta
Right Ventricular Hypertrophy
Stenosed Pulmonary Trunk

Question 12

Describe these two congenital Hernias:

1. Bochdalek
2. Morgagni

Answer 12

1. Posterolateral hernia through the Foramen of Bochdalek (pleuroparietal membrane)
2. Hernia through the Foramen of Morgagni between the xiphoid and the costal margins

Question 13

What forms the Thoracic Cage

Answer 13

Vertebral Colum posteriorly
Sternum, costal cartilages anteriorly
Ribs Laterally

Question 14

Which