Cardiovascular System 1 PDF - UNIC MD-6

Cardiovascular System 1 UNIC MD-6 Anatomy Station Guide (Student Version) Week 2 Session Outline This practical session will focus on the contents of the thorax, the structure of the heart, the normal blood flow through the heart, and the...

Cardiovascular System 1 UNIC MD-6 Anatomy Station Guide (Student Version) Week 2 Session Outline This practical session will focus on the contents of the thorax, the structure of the heart, the normal blood flow through the heart, and the great vessels. Specific Learning Outcomes (after the session, students should be able to identify the following) Identify the underlying anatomy of the main thoracic and abdominal organs, using superficial physical landmarks and surface lines. Identify the different tissues of the body layers and the major viscera of the thoracic, abdominal and pelvic cavities. Use appropriate anatomical terminology to describe the relationships between the major viscera and parts of the body. Identify the four chambers of the heart and the surfaces of the heart (anterior, posterior, base etc.). Describe the normal flow of blood through the heart. Identify the branches of the arch of the aorta (brachiocephalic artery, left common carotid artery, left subclavian artery) and the structures they supply. Identify the branches of the descending thoracic aorta (paired posterior intercostal, bronchial, oesophageal, mediastinal arteries) and the structures they supply. Describe the major relations of the ascending, arch, and descending thoracic aorta. Describe he common variations of the branches of the arch of the aorta and their clinical significance. Identify the azygos, hemiazygos and accessory hemiazygos veins and describe the communications of the azygos system with the caval system of veins. Describe the function of the azygos venous system. Describe the relationship of the ligamentum arteriosum to the left vagus nerve, including the outline of innervation of mediastinum. Describe the location of the oesophageal and pulmonary plexuses and superficial and deep cardiac plexuses. Locate the major vascular anatomy within cadaveric specimens. Suggested Readings: Moore KL, Agur AMR, Dalley AF. 2011. Essential Clinical Anatomy. 4th Edition. Pages: 65-70, 84-92 Netter F.H. Atlas of Human Anatomy. 2003. 3rd Edition. Plates: 190-221. Station 1: Thoracic Vasculature and Innervation Task - Identify the following blood vessels: Superior vena cava Inferior vena cava Pulmonary trunk Right and left pulmonary veins Ascending aorta - Aortic sinuses are dilations of the ascending aorta just superior to the aortic valve. Task - Identify the following aortic sinuses: - Posterior sinus- Gives rise to the Left coronary artery. - Anterior sinus- Gives rise to the Right coronary artery. - Non-coronary sinus- Does not give rise to any arteries *Practical implications - aneurysm of the ascending aorta Discussion with demonstrator: - The ascending aorta wall is not reinforced by the fibrous pericardium. Patients often complain of chest pain (often severe) that radiates to the back. Arch of the aorta Task - Identify its branches: o Brachiocephalic artery o Left common carotid artery o Left subclavian artery - Which regions of the body do these branches supply? *Practical implications: variations in branches of the arch of the aorta. Discussion: - Occasionally the left common carotid originates from the brachiocephalic trunk; in other individuals a brachiocephalic trunk fails to form, or the left vertebral artery originates from the arch of the aorta. More rarely an anomalous right subclavian artery may run behind the oesophagus compressing it and causing dysphagia. *Are any of these variations and anomalies present in your cadaver? Descending thoracic aorta - This begins from the arch of the aorta at about T4-T5. - Identify the aorta coursing into the posterior mediastinum and passing through the aortic hiatus of the diaphragm at T12. Task - Identify its branches (some are too small to see on the specimen): Bronchial,Oesophageal, Pericardial,Mediastinal, Posterior intercostals (9 pairs), Subcostal and Superior phrenic arteries Azygos system - The azygos, hemiazygos, and accessory hemiazygos veins drain the posterior thoracic and abdominal walls and join the superior vena cava above the right lung root. Task - Identify these structures on your cadaver. *Practical implications: azygos system variations - In some people an accessory azygos vein parallels the main azygos vein on the right side while other people have no hemiazygos system of veins. - A clinically important, although uncommon variation, is when the azygos system receives all the blood from the IVC, except that from the liver. In such people, the azygos system drains most of the body below the diaphragm (except that from gut). - If (somewhat rarely) an obstruction of the SVC occurs superior to the entrance of the azygos vein, blood can drain inferiorly into the veins of the abdominal wall and return to the right atrium through the IVC and azygos system of veins. Thoracic (lymph) duct - The thoracic duct begins in the abdomen arising from the cisterna chyli. It drains lymph from the abdomen, pelvis, left thorax, head and neck, upper and both lower limbs. - It empties into the junction of the left internal jugular and left subclavian veins. Task - Try to identify the thoracic duct between the oesophagus and thoracic aorta. *Practical implications: Laceration of Thoracic duct - Because the thoracic duct is thin-walled and may be colourless, it may not be easily identified. Consequently it is vulnerable to inadvertent injury during investigative and/or surgical procedures in the posterior mediastinum. Laceration of the thoracic duct allows chyle to escape into the thoracic cavity. Innervation Task - Identify the following nerves: Right phrenic nerve - Travels lateral down the right brachiocephalic vein and superior vena cava. - Runs anterior to the root of the right lung, across the pericardium to the diaphragm. Left phrenic nerve - Descends along left side of left subclavian artery, crosses the left vagus nerve superficially as it approaches the aortic arch. Right vagus nerve - Lies to the right of the trachea. - Enters the thorax anterior to the beginning of right subclavian artery. - The right recurrent laryngeal nerve branches off to curve below the origin of the subclavian artery. - The right vagus contributes to pulmonary plexus (as it runs posterior to root of right lung; in most cases these nerves are too fine to see). - It then contributes to oesophageal plexus via the posterior vagal trunk. Left Vagus Nerve - Identify this nerve between common carotid and subclavian arteries. - This nerve runs posterior to root of the left lung where it contributes to the pulmonary plexus (usually too fine to see). - It then contributes to the oesophageal plexus via the anterior vagal trunk. - The left recurrent laryngeal nerve arises from medial side of left vagus nerve as it crosses (anterior to) the aortic arch. - It curves medially below the arch and posterior to ligamentum arteriosum (a band of fibrous tissue connecting the pulmonary bifurcation to the aortic arch). - It then travels superiorly into the lower neck within the tracheo-oesophageal groove. - Identify the right and left recurrent laryngeal nerves in the neck and thorax and be aware of the Oesophageal plexus (vagal branches that supply the oesophagus) Pulmonary plexus (vagal branches that with sympathetic fibres supply the bronchi) Cardiac plexus (vagal branches and fibres from the sympathetic trunks). These structures are hard to find because they are small but they are functionally important so be aware of their positions – see models *With the assistance of your demonstrator, identify the underlying anatomy of the main thoracic and abdominal organs, using superficial physical landmarks and surface lines. Station 2: Structure of the Heart Pericardial cavity Task - Identify the following: Transverse pericardial sinus *Practical implications: Surgical Significance of the Transverse Pericardial Sinus - The transverse pericardial sinus is important to vascular surgeons. - After the pericardial sac is opened anteriorly, a finger can be passed through the transverse pericardial sinus posterior to the aorta and pulmonary trunk. By passing a surgical clamp or placing a ligature around these vessels, inserting the tubes of a coronary bypass machine, and then tightening the ligature, surgeons can stop or divert the circulation of blood of these large arteries while performing cardiac surgery, such as coronary artery bypass grafting Oblique pericardial sinus Pericardial reflections connecting parietal and visceral pericardium - Note the continuity of the parietal and visceral serous pericardium around the roots of the great vessels and the extent to which the ascending aorta and pulmonary trunk are contained within the fibrous pericardium, covered by serous pericardium. Heart - Identify the position of the heart in the thorax. - Note the anatomical relations of the heart surfaces (apex, base, anterior, posterior). *Practical implications: Positional Abnormalities of the Heart - Because of abnormal folding of the embryonic heart, the position of the heart may be completely reversed so that the apex is directed to the right instead of the left (dextrocardia). Dextrocardia is frequently associated with mirror image positioning of the great vessels and the arch of the aorta. - When accompanied by situs inversus, the incidence of accompanying cardiac defects is low and the heart usually functions normally. - Isolated dextrocardia may be complicated by severe anomalies such as transposed great arteries. Task - Identify the following structures and note their surfaces (anterior, posterior, base etc): Right atrium and auricle - Identify the foramen ovale and fossa ovalis  Right ventricle Left atrium and auricle Left ventricle Right atrio-ventricular groove - What lies within it? Anterior inter-ventricular groove -What lies within it *Practical implications: Percussion of the Heart - Percussion allows size of the heart to be assessed - The classical percussion technique is to create vibration by tapping the chest with a finger while listening and feeling for differences in sound wave conduction. - Percussion is performed at the 3rd, 4th, and 5th intercostals spaces from the left anterior axillary line to the right anterior axillary line. - Normally the percussion note changes from resonance to dullness (because of the presence of the heart) approximately 6 cm to the left border of the sternum. Blood Flow through the Heart Task - Trace the blood flow through the heart as it passes through the following valves: Atrioventricular (tricuspid) Pulmonary Atrioventricular (mitral) Semilunar Right Coronary artery - It has 2 important branches: (right) marginal artery, posterior interventricular (descending) artery Left Coronary artery - It has 2 major branches: anterior interventricular artery and the Circumflex artery with its left marginal branch Station 3: Vascular Anatomy Head and Neck Identify the sternocleidomastoid muscle and the thyroid cartilage (Adam’s apple). Observe the common carotid artery between the lateral border of the thyroid cartilage and the medial border of the sternocleidomastoid. Note that the common carotid artery is accompanied by the internal jugular vein. Observe that the common carotid divides to form the internal and external carotid arteries. The internal carotid passes into the cranial cavity to supply the brain, and gives off no branches outside the cranial cavity. The external carotid gives off branches that supply structures in the neck and face. Identify the arch of the aorta in the thoracic cavity and the three branches that come off it: the brachiocephalic trunk, left common carotid artery and left subclavian artery. Upper Limb Note that the short brachiocephalic trunk divides to form the right subclavian and right common carotid arteries. The subclavian artery emerges between the scalene muscles and crosses the first rib, at the lateral border of which it is called the axillary artery. Note that in an emergency the subclavian artery can be compressed against the first rib to arrest bleeding. Locate the subclavian artery in the posterior triangle of the neck (lateral to the sternocleidomastoid muscle). Identify the axillary artery within the axilla (abduct the upper limb to do this). Follow the axillary artery into the upper limb. At the inferior border of the teres major muscle it becomes known as the brachial artery. The brachial artery in the cubital fossa is often used for blood pressure measurements. *However, its branching pattern is variable. The median cubital vein, cephalic and basilic veins of the cubital fossa are a common place for venepuncture, so it is important to be aware of the (variable) anatomy of this region. Two commonly occurring patterns that are described, the ‘H-pattern’ and the ‘M-pattern’. Follow the brachial artery into the cubital fossa, where it divides to form the radial and ulnar arteries. Identify the radial artery and ulnar artery at the wrist. *Note how these arteries are related to the flexor tendons at the wrist. The vessels supplying the hand are described as three levels – superficial palmar, deep palmar and dorsal network. The terminology suggests that the vessels are symmetrical but they rarely are. Identify the common palmar digital arteries. It is important to recognise that the digital arteries are end arteries (local anaesthesia). The hand has both superficial and deep venous drainage. The deep venous drainage is provided by veins that accompany the arteries. Try to identify these on your specimens; they form venae comitantes and may be small. The dorsal venous network is the superficial network of veins that form on the dorsum of the hand and drains into the basilic and cephalic veins. It is much more prominent than the deep system but is quite variable, and like all superficial venous networks is collapsed in the cadaver. Examine these on the dorsum of the hands of members of your group to appreciate their variability. *The radial artery at the wrist is the commonest site at which to palpate the pulse and may also be used for taking arterial blood gas samples in patients with heart and lung disease. It can be easily compressed here against the flat anterior surface of the radius. Trace back the ulnar and radial arteries into the arm. Being ‘hidden’ under muscles mostly protects these arteries. If veins are still present on your cadaver, identify the cephalic vein (lateral) and the basilic vein (medial) [remember: a, b, c – aorta, basilic, cephalic]; and the median cubital vein in the cubital fossa.  Abdomen and Pelvis Identify the aorta running down approximately in the midline of the abdomen. Note that the aorta emerges through the aortic hiatus of the diaphragm at the level of T12 (i.e. at the level of the 12th thoracic vertebra). Identify the left and right common iliac arteries at the point of bifurcation of the aorta (at approximately the level of the umbilicus – L3/4). Follow the common iliac artery to the point where it bifurcates into the internal and external iliac arteries. Note that the iliac arteries are accompanied by the corresponding veins. Check if there is a swelling (aneurysm) of the abdominal aorta just above the bifurcation. AAA occurs most commonly in male smokers aged 65 – 75 years (approx 5% of Caucasian males), and can be a life-threatening condition. The internal iliac artery runs down into the pelvis where it supplies the pelvic organs. The external iliac artery continues down into the lower limb. It passes under the inguinal ligament, at which point it becomes known as the femoral artery. Lower limb Distinguish between the mid-inguinal point, and the mid-point of the inguinal ligament. Identify the femoral artery at the mid-inguinal point. Note how it is related to the nerve and vein that lie alongside the artery. Locate the midpoint of the inguinal ligament – what structure(s) lie at this point? Follow the femoral artery distally. Note that it passes through one of the muscles in the medial compartment of the thigh. Locate the great (long) saphenous vein running up the medial side of the lower limb. Note that it passes approximately one finger’s breadth in front of the medial malleolus, and terminates by draining into the femoral vein. In the popliteal fossa at the back of the knee, locate the popliteal artery and vein within the fossa. Note that the popliteal artery runs deep to the vein. Distal to the popliteal fossa the popliteal artery bifurcates to form the anterior tibial and posterior tibial arteries. Identify the short saphenous vein. Note that it commences close to the lateral malleolus of the ankle and drains into the popliteal vein. Locate the posterior tibial artery inferior to the medial malleolus. Try to locate dorsalis pedis (the continuation of the anterior tibial artery) on the dorsum of the foot, lateral to the tendon of extensor hallucis longus. Variability in the arteries of the foot may sometimes mean that a pulse cannot be located where expected. The region normally supplied by the absent artery is supplied instead by one of the other foot arteries Self-Directed Learning Station Identify and compare the different tissues of the body layers and the major viscera of the thoracic, abdominal and pelvic cavities. Task – examine the various tissues from the pictures provides, histology slides, and anatomic specimens.