Cardiac Anatomy Flashcards
Mediastinum
Slightly shifted to the left and sits on top of the diaphragm
Divided into: anterior, superior, middle and posterior
Anterior mediastinum
Borders:
Anterior= sternum
Posterior= middle mediastinum
Contents:
Thymus, lymph nodes, internal thoracic vessels, thyroid tissue
Middle mediastinum
Contents:
Pericardium, heart, ascending aorta, SVC/IVC, brachiocephalic vessels, pulmonary vessels, trachea and main bronchi, phrenic nerve, vagus nerve, left recurrent laryngeal nerves
Superior mediastinum borders
Manubriosternal joint
Inferior edge of T4 body
Posterior mediastinum borders
Anterior: middle mediastinum
Posterior: anterior thoracic vertebral column
Posterior mediastinum contains
Oesophagus
Azygos and hemiazygos
Descending aorta
Endocardium
Innermost layer
Made of epithelial cell layer
Thin layer of fibrous connective tissue lined on its inner surface by a single flat layer of simple squamous endothelial cells
Lines the heart chambers and valves
Myocardium
Muscular middle layer
Cardiac myocytes:
Striated branching cells
Many mitochondria
Central nucleus
Intercalated discs- allow for contraction in syncytium
cells remain separate and do not form a syncytium
• Shorter refractory period than skeletal muscle
• Do not fatigue
• Secrete hormones
Intercalated discs
(pale areas between adjacent myocytes when stained with H&E)- specialised connections between myocytes which join them together to form long, branching chains.
-Connect actin filaments of adjacent myocytes
-contain: gap junctions (allows flow of ions to connect cells electrochemically), adhering junctions and desmosomes (connect cells by linking intermediate cytoskeleton filaments)
Lipofuscin
Yellow/brown pigment that accumulates in cardiac myocytes with increasing age
Endomysium
between myocytes loose fibrous connective tissue (endomysium)- may contain small number of lymphocytes
Atrial vs ventricular myocytes
• Large myocytes found in wall of left ventricle
• Atrial myocytes contain perinuclear neuroendocrine granules (atrial natriuretic peptide) located near the nuclei- hormone that is released when the cells are stretched excessively. This hormone increases the excretion of water and sodium and potassium ions by the kidney. It also inhibits renin secretion causing a lowering of blood pressure.
Epicardium
layer of fatty connective tissue- underlying adipose connective tissue, vessels and nerves
• between pericardium and myocardium
• Layer contains the coronary arteries
Pericardium
heart lies in a fibrous sack lined by a layer of mesothelial cells
• outermost layer of the heart
• Layer of squamous mesothelioma cells resting on thin layer of connective tissue
• Visceral pericardium - layer on outer surface of the heart. layer is reflected at the roots of the great vessels to become the parietal pericardium, the inner of the two layers of tissue that form the pericardial sack
• parietal pericardium- layer of cells on inner surface of fibrous sack containing the heart
Fibrous pericardium
Outer layer
Tough connective tissue which anchors the heart to the mediastinum
Serous pericardium
Simple squamous epithelial layer
Parietal pericardium- lines the fibrous pericardium and secretes fluid
Visceral pericardium- covers outer surface of the heart
How is blood pressure information transferred from Baroreceptors to the central nervous system
The carotid sinus conveys information about blood pressure via the IX cranial nerve (glossopharyngeal nerve) across a finite pressure range
Which nerve does the aortic arch Baroreceptors convert information about blood pressure across
Cranial nerve X (vagus nerve)
3 types of capillary
Continuous
Fenestrated
Sinusoidal
Blood vessels myogenic tone
Vascular smooth muscle is never fully relaxed
How much thinner is right ventricle than left ventricle walls
1/3
Cardiac muscle compared to skeletal muscle
Striated
Branched
Intercalated discs
Where are the greatest proportion of musculi pectinati found?
Right atrium
internal muscular ridges on the anterolateral surface of the chambers and they are only present in the area derived from the embryological true atrium.
