Lecture 27 - Cardiovascular system: the heart

Question 1

Name and describe the location of the subdivisions within the thoracic cavity

Answer 1

o Pleural cavity
Between layers of pleura around a lung
o Pericardial cavity
Between layers of pericardium around the heart
o Media sternum
Central portion: contains heart, thymus, oesophagus, trachea and great vessels

Question 2

Understand the size, position and orientation of the heart within the mediastinum

Answer 2

o Heart is in pericardial sac
o Mediastinum is centrally located region extending from sternum to vertebral column, from first rib to diaphragm and between the lungs
o Extends obliquely from 12-14cm from second rib to 5th intercostal spaces
o Rests on superior surface of the diaphragm
o Anterior to the vertebral column and posterior to sternum
o 2/3 lies left of the midsternal line, apex projects to the left
o Lungs flank heart laterally and partially obscure it

Question 3

Describe the coverings of the heart

Answer 3

o Outer layer
 The hear is enclosed in the pericardium (double-walled sac)
 Superficial part of the sac is fibrous pericardium
o Inner layer
 Deep to fibrous pericardium is serous pericardium

Question 4

Identify and describe the anatomical features of the heart (atria, ventricles, AV valves, SL valves) and relate this to their function

Answer 4

o About the size of a fist
o 250-350 grams
o Anterior surface
 Right ventricle, right atrium, left ventricle
o Posterior surface
 Left atrium, left ventricle, proximal components of great veins

Question 5

Relate the structure and function of the heart valves to systole and diastole

Answer 5

o Diastole
 Mitral valve open
 Tricuspid valve open
 Aortic valve closed
 Pulmonary valve closed
o Systole
 Opposite

Question 6

Describe the components of the cardiac conduction system and the activation sequence

Answer 6

o Initiates and coordinates contraction of atria and ventricles to pump blood
o Consists of 4 basic components of nodes and networks:
 Sinu-atrial node (SA node)
 Atrioventricular node (AV node)
 Atrioventricular bundle (Bundle of His)
* Gives off left and right branches
 Subendocardial plexus (Purkinje fibres – left & right)