Mediastinum Anatomy & Physiology PA 481 C Tony Serino, Ph.D. Biology Department Misericordia Univ.

Mediastinum Anterior Superior Middle Posterior Superior and anterior are continuous with each other; both may be referred to as the superior mediastinum

Superior Mediastinum Great Vessels of the Heart Aortic arch Transverse thoracic plane

Remnant of Ductus arteriosus Ligamentum arteriosum

Usual Aortic Arch Pattern 65% of all people RS BT LS LC RC

Aortic Arch Variations 27% one BT with both CC exiting 5% 1.2% two BT left vert. a.

SVC BC SVC Vagus Phrenic

Pulmonary Arteries and Veins

Trachea and Primary bronchi

Structure Order BC Aorta PA Trachea

Esophagus Function: Deglutition Two sphincters: upper and lower esophageal sphincters (lower is physiological only) Retropleural position (therefore, covered by adventitia) Mucosa: stratified squamous with many mucus glands (esophageal glands) Muscularis: changes from skeletal to smooth muscle

Esophagus Histology

Thymus Gland Bilobed organ that is largest in children, but begins to regress sharply at the onset of puberty (around age 11) It is the site of T-cell lymphocyte production and produces hormones (such as, thymosin) that modifies their physiology

General Circulatory System 1.Cardiovascular –Consists of a closed system of vessels which transport blood –Two circuits: Systemic and Pulmonary –Arteries move blood away from the heart –Veins move blood toward the heart

General Circulatory System 2.Lymphvascular – moves lymph –Consist of blind end tubes which collect interstitial fluid (now called lymph) and returns it to circulation –The lymph is cleaned before returned to the blood vessels

Heart Development

Fetal Circulation

Selected Heart Defects

Heart as a Dual Pump Cardiac muscle arranged as whorls that squeeze the blood Twin pumps: systemic and pulmonary Four chambers: 2 atria and 2 ventricles

Cardiac Muscle Cells

Cardiac Muscle Depolarization

Conductance of Ions during Depolarization

Heart: Location

Heart in Relation to other Organs

Layers of the Heart and Pericardium

Heart: Anterior View Transverse Pericardial sinus

Heart: Posterior View Oblique Pericardial sinus

Heart: Internal Anatomy

Differences in Ventricular Wall

Coronary Artery Schematic (LAD)

Most Common Coronary Arterial Pattern Fig Ant. Desc. a. (LAD) Post. Desc. a. R. Marginal a. L. Marginal a. Circumflex a.

Coronary Variation 15% LCA dominant Single CA Most people right dominant. Circumflex from right aortic sinus (4% have an accessory coronary artery) (note: which branch gives rise to posterior descending a.determines dominance)

Fig b

Fig c

Fig d

Coronary Vein Schematic

Coronary Veins Fig Coronary sinus Great Cardiac v. Small Cardiac v.Middle Cardiac v. Ant. Cardiac veins

Major Cardiac Valves

aortic valve (SL) AV (tricuspid) Heart Valves sinus Nodule (corpara aranti) cusps

Fig b

Diastole: Period of Ventricular Filling

Systole: Isovolumetric Contraction

Systole: Ventricular Ejection

Diastole: Isovolumetric Relaxation

Conduction System of Heart

Pacemaker Potential

ECG and electrical changes

Normal ECG

ECG Normal Sinus Rhythm Junctional Rhythm (AV node rhythm)

Second Degree Heart Block Ventricular Fibrillation (V-fib)

Heart Sounds “Lub-dub” Sound associated with valve closing producing turbulent blood flow

Cardiac Cycle

(ml/min)

Factors Affecting SV Stroke Volume (SV) = End Diastolic Volume – End Systolic Volume SV = EDV – ESV (ml/beat) EDV affected by: –Venous return which is dependent on venous tone, skeletal muscle pumps, etc. ESV –As the heart fills it is stretched which allows for better overlap of the contractile proteins which will affect the force of contraction and the ESV (Starling’s Law of the Heart) –Increasing the force of contraction at any EDV will decrease the ESV and increase the SV (sympathetic stimulation and epinephrine)

Sympathetic Stimulation Leads to increase HR Increases in Ca ++ release from SR, increase Ca ++ through membrane and increase myosin crossbridge cycling Increases force of contraction

Heart Rate Control Sinus Rhythm = normal SA node control Autonomic Activity –Sympathetic (thoracic trunk) = accelerator (induces tachycardia) –Parasympathetic (vagus n.)= brake (induces bradycardia) Hormones –epinephrine Drugs -caffeine, nicotine, atropine, etc.

Posterior Mediastinum Thoracic aorta Sympathetic trunk Vagus n. Azygous v. Trachea Esophagus Phrenic n. Intercostal a., v., & n. Hemiazygous v. Lung root Thoracic duct

Small Aortic Branches Bronchial a. Intercostals Coronary Esophageal

Azygous vein Hemiazygous v.

Nerves of Post. Mediastinum

Thoracic Duct