Missing Notes: Unit Four Hello Class, I’m hoping to cover some of what’s here in class on Wednesday. See you soon, Julian

Regions within the Mediastinum Superior Anterior Posterior Middle

Lungs – External anatomy Each lung is conical and has a base and an apex. The costal surface contacts the ribs and the concave mediastinal surface faces the mediastinum. The mediastinal surface contains the hilum, where bronchi, blood vessels, nerves and lymphatic vessels connect with the lung.

Lungs Each lung has a cardiac impression (larger on the left). Each lung has an oblique fissure that divides the lung into superior and inferior lobes. The right lung also has a horizontal fissure and a middle lobe. The lingula of the left lung is homologous with the middle lobe of the right lung. Major vessels also make impressions, like the aortic impression of the left lung.

External Heart Anatomy Composed of four chambers: two smaller and superior atria and the two larger and inferior ventricles. An ear-shaped anterior extension of each atrium is its auricle. The atria and ventricles are separated from each other by a groove called the coronary sulcus The anterior interventricular sulcus and posterior interventricular sulcus are grooves between the ventricles and run from the coronary sulcus toward the heart’s apex. Internally, the interventricular septum follows this line.

Conducting System of the Heart The electrical impulse that initiates the heartbeat comes from a group of specialized cardiac muscle cells called the sinoatrial (SA) node. The SA node generates 70-80 impulses per minute under parasympathetic control.

Conducting System of the Heart Impulses from the SA node travel to the left atrium and the atrioventricular (AV) node located in the floor of the right atrium. Electrical impulses pass into the atrioventricular bundle (bundle of His) which extends into the interventricular septum and branches into left and right bundles. These bundles conduct the impulse to cells called Purkinje fibers that spread the impulse superiorly from the apex to all of the ventricular myocardium.

Conducting System of the Heart

Sequence of Heart Chamber Contractions SA node generates an impulse Both atria contract almost simultaneously (systole) while ventricles are relaxing (diastole) Impulse goes to AV node and then to the ventricles Ventricles contract (systole) while atria relax (diastole).

Innervation of the Heart The heart, like most internal organs, is innervated by the sympathetic and parasympathetic divisions of the autonomic nervous system. The anatomical components of both divisions make up the coronary plexus. Sympathetic innervation of the heart is supplied by fibers from the sympathetic trunks. This input increases the rate and force of heart contractions. Parasympathetic innervation is supplied by branches of the Vagus N (CN X) and decreases heart rate.

External Heart Anatomy

External Heart Anatomy

Right Atrium Three veins carry low-oxygen blood into the R atrium: Coronary sinus Superior vena cava Inferior vena cava The right atrioventricular valve separates the atrium from the ventricle. On the wall of the right atrium are myocardial features called pectinate muscles. These ‘muscles’ stop on a smooth band called the crista terminalis. The interatrial septum is the wall between the atria. The fossa ovalis is a remnant of a fetal opening here called the foramen ovale.

The Ventricles The interventricular septum forms a thick wall between the ventricles. The inner wall of the ventricles display myocardial features called trabeculae carneae. The cusps of the A/V valves are secured to the myocardium via papillary muscles and Chordae tendineae. In the right ventricle is the septomarginal trabecula (moderator band) which secures a large papillary muscle to the interventricular septum. The right ventricle has a smooth cone-shaped upper portion called the conus arteriosus which leads to the pulmonary semilunar valve.

Right Ventricle

Left Atrium This chamber receives high-oxygen blood from the lungs through the pulmonary veins. The left atrium is separated from the left ventricle by the left atrioventricular valve which is also referred to as the bicuspid or mitral valve.

The Thoracic Duct The thoracic duct is the largest lymphatic vessel Like all lymphatic vessels, it transports interstitial fluid (lymph) into the bloodstream. The thoracic duct collects lymph from ~3/4 of the body. The thoracic duct drains into the junction between the left subclavian and internal jugular veins.

5. Lymphatic Ducts