Basic Science CTVS - 62 anatomy and physiology

  1. Explain superficial veins of lower limb with relevant applied aspects. [TU 2073]

    Mention formation, course, and termination of great saphaneous vein and discuss in short its surgical importance. [TU 2061,64,68/5]

    Short note on course and extent of great saphenous vein. [TU 2055]

    Superficial Venous System?
    • Form a network that connects the superficial dorsal veins of the foot and deep plantar veins.
    • The dorsal venous arch, into which empty the dorsal metatarsal veins, is continuous with the great saphenous vein medially and the small saphenous vein laterally.

    • The great saphenous vein extends cephalad and travels over the medial aspect of the tibia and in parallel to the saphenous nerve.
    • The great saphenous vein travels within its own fascia, called the saphenous sheath.
    • The great saphenous vein terminates into the saphenofemoral junction, where it is joined by the confluence of the superficial circumflex iliac veins, the external pudendal veins, and the superficial epigastric veins. It then ascends in the superficial compartment and empties into the common femoral vein after entering the fossa ovalis.

    The small saphenous vein arises from the dorsal venous arch at the lateral aspect of the foot and ascends posterior to the lateral malleolus, rising cephalad in the midposterior calf. The small saphenous vein continues to ascend, penetrates the superficial fascia of the calf, and then terminates into the popliteal vein.

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  2. Why the veins of lower limb are prone to varicosity. [TU 2067/2]
    ?
  3. Clinical importance of great saphenous vein?
    • Pathology of the great saphenous vein
    • - Varicose veins
    • - Thrombophlebitis

    • Use in cardiovascular procedures
    • - The vein is often removed by cardiac surgeons and used for autotransplantation in coronary artery bypass operations.
    • - The great saphenous vein is the conduit of choice for vascular surgeons for doing peripheral arterial bypass operations because it has superior long-term patency compared to synthetic grafts (PTFE, PETE (Dacron)), human umbilical vein grafts or biosynthetic grafts.
    • - Removal of the saphenous vein will not hinder normal circulation in the leg. The blood that previously flowed through the saphenous vein will change its course of travel. This is known as collateral circulation.
    • - The saphenous nerve is a branch of the femoral nerve that runs with the great saphenous vein and can be damaged in surgery on the vein.

    • Use in emergency medicine - 
    • - When emergency resuscitation with fluids is necessary, and standard intravenous access cannot be achieved due to venous collapse, saphenous vein cut down may be necessary.
  4. Perforators of leg?
    Upto 100 perforators have been documented. Important perforators among them are 

    • Dodd's perforator at the inferior 1/3 of the thigh
    • Boyd's perforator at the knee level
    • Cockett's perforators at the inferior 2/3 of the leg (usually there are three: superior medium and inferior Cockett perforators).

    [@ CBD from below up]
  5. Explain origin, course and termination of thoracic duct. [TU 2065/12] 

    Short note on thoracic duct?
    The thoracic duct is the largest lymphatic vessel in the body. It extends from the upper part of the abdomen to the lower part of the neck, crossing the posterior and superior parts of the mediastinum. It is about 45 cm long. It has a beaded appearance because of the presence of many valves in its lumen

    • Course - 
    • The thoracic duct begins as a continuation of the upper end of the cisterna chyli near the lower border of the twelfth thoracic vertebra and enters the thorax through the aortic opening of the diaphragm. 
    • It then ascends through the posterior mediastinum crossing from the right side to the left at the level of the fifth thoracic vertebra. It then runs through the superior mediastinum along the edge of the oesophagus and reaches the neck.
    • In the neck, it arches laterally at the level of the transverse process of seventh cervical vertebra. Finally it descends in front of the first part of the left subclavian artery and ends by opening into the angle of junction between the left subclavian and left internal jugular veins.

    The thoracic duct receives lymph from, roughly, both halves of the body below the diaphragm and the left half above the diaphragm.

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  6. Describe briefly the arch of aorta. [TU 2054]

    Abnormal origin of aberrant right subclavian artery. [TU 2070]
    Arch of the aorta is the continuation of the ascending aorta. It is situated in the superior mediastinum behind the lower half of the manubrium sterni

    The most common embryologic abnormality of the aortic arch is aberrant right subclavian artery (ARSA), known clinically as arteria lusoria (AL)

    • Usually, three large arteries arise from the arch of the aorta: the brachiocephalic trunk (divided into the right common carotid artery and the right subclavian artery), the left common carotid artery, and the left subclavian artery.
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    • However, when aberrant right subclavian artery variant is present, the brachiocephalic trunk is absent and four large arteries arise from the arch of the aorta: the right common carotid artery, the left common carotid artery, the left subclavian artery, and the final one with the most distal left sided origin, the right subclavian artery, also called the arteria lusoria.  This vessel travels to the right arm, crossing the middle line of the body and usually passing behind the esophagus. If the artery compresses the esophagus, it may produce a condition called dysphagia lusoria. 
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    Clinical features - They are often asymptomatic, but around 10% of people may complain of tracheo-oesophageal symptoms, almost always as dysphagia termed dysphagia lusoria. 


    • Associations
    • as can be expected from embryology, the right recurrent laryngeal nerve is usually non-recurrent (that is, enters the larynx directly)
    • - aneurysmal dilatation (aberrant subclavian arterial aneurysms) of the proximal portion of an aberrant right subclavian artery can occur, a pouch like aneurysmal dilatation is called a diverticulum of Kommerell
    • - if there is a retro-oesophageal course, it can get compressed between the oesophagus and the vertebra
    • - it can be associated with trisomy 21, trisomy 18 and other chromosomal defects
  7. Boundaries of mediastinum?
    • Superior - Thoracic outlet
    • Inferior - Diaphragm
    • Anterior - Sternum
    • Posterior - Thoracic vertebrae
    • Lateral - Lungs & pleurae
  8. Divisions of mediastinum?
    It is divided by a horizontal plane  extending from sternal angle to lower border of 4th thoracic vertebra into:

    • 1. Superior mediastinum (S): above the plane
    • 2. Inferior mediastinum: below the plane


    • Inferior mediastinum is subdivided into:
    • - Middle mediastinum (M):contains heart
    • - Anterior mediastinum (A):in front of heart
    • - Posterior mediastinum (P):behind hear

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  9. Explain posterior mediastinum and their boundaries, contents and relations. [TU 2070/5]
    • Boundaries
    • Superior - Horizontal plane
    • Inferior - Diaphragm
    • Anterior - Heart
    • Posterior - Thoracic vertebrae from T5 to T12
    • Lateral -  Lungs & pleurae

    • Contents -
    • 1 Descending aorta: posterior & to the left of esophagus
    • 2 Azygos vein: posterior & to the right of esophagus
    • 3 Thoracic duct: posterior to esophagus
    • 4 Esophagus
    • 5 Right & left Sympathetic trunks
    • 6 Vagus nerves: around esophagus
    • 7 Lymph nodes [@ DATES]
  10. Short note on azygose vein.  [TU 2055]
    The azygos venous system is located on either side of the vertebral column and drains the viscera within the mediastinum, as well as the back and thoracoabdominal walls. This system consists of the azygos vein and its two main tributaries: the hemiazygos vein and the accessory hemiazygos vein.

    Anatomical Course - The azygos vein usually originates from the posterior aspect of the inferior vena cava, at the level of the renal veins. It ascends within the posterior mediastinumto the level of T4 before it arches above the right pulmonary hilum. It drains into the superior vena cava just before it pierces the pericardium.

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  11. Development of heart tube: development of intra-atrial septum. Mention 4 common anomalies of heart and their clinical significance. [TU 2056]
    Heart development refers to the prenatal development of the human heart. This begins with the formation of two endocardial tubes which merge to form the tubular heart, also called the primitive heart tube, that loops and septates into the four chambers and paired arterial trunks that form the adult heart. The heart is the first functional organ in vertebrate embryos, and in the human, beats spontaneously by week 4 of development.

    The tubular heart quickly differentiates into the truncus arteriosus, bulbus cordis, primitive ventricle, primitive atrium, and the sinus venosus. The truncus arteriosus splits into the ascending aorta and pulmonary artery. The bulbus cordis forms part of the ventricles. The sinus venosus connects to the fetal circulation.

    The heart tube elongates on the right side, looping and becoming the first visual sign of left-right asymmetry of the body. Septa form within the atria and ventricles to separate the left and right sides of the heart


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  12. Development of inter-atrial septum and congenital anomalies associated with it. [TU 2062/2057/5]
    • Two atrial septa are formed, both of which contribute to the definitive atrial septum.  They are associated with two inter-atrial communications (ostia).
    •  
    • The septum primum begins to develop at 28 days. It is a thin, crescentic fold of endocardium that arises craniodorsally and grows down to the AV cushions, leaving an ostium primum below its free edge.  It fuses with the AV cushions at approx. 35 days, obliterating the ostium primum.

    The ostium secundum is an opening in the upper part of the septum primum. It forms at about 33 days i.e. before the ostium primum closes.  It forms by apoptosis (programmed cell death) as a number of  small perforations that coalesce.

    The septum secundum begins to develop at about 33 days. It is a thick muscular septum that arises to the right of the septum primum in the intersepto-valvular space (between the septum primum and the left venous valve of the SA opening).  It grows from the roof of the atrium but never reaches the AV cushion forming the  fossa ovalis.



    The final atrial septum is formed from both septum primum and septum secundum:

    • 1. The muscular part of the atrial septum is derived from the septum secundum fused with the septum primum
    • 2. The ostium secundum is covered by the septum secundum
    • 3. The limbus fossae ovalis is the free border of the septum secundum
    • 4. The floor of the fossa ovalis is formed of septum primum - it is thin and membranous and forms the flap valve mechanism


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  13. Sources of development of diaphragm. [TU 2064,73/12]
    The diaphragm develops during weeks 4–12 of  embryogenesis. It is composed of four components: the transverse septum, pleuroperitoneal folds, esophageal mesentery, and muscular body wall. 

    The transverse septum, which is anterior, becomes the central tendon of the diaphragm . A defect in fusion of the transverse septum to the lateral body wall leads to an anterior (Morgagni) hernia. Morgagni hernias constitute fewer than 10% of congenital diaphragmatic hernias. The transverse septum fuses laterally with the muscular body wall and posteriorly with the esophageal mesentery and pleuroperitoneal folds.

    A posterior (Bochdalek) hernia likely represents a developmental defect of the pleuroperitoneal folds or failure of fusion of the folds and transverse septum with the intercostal muscles. Bochdalek hernias constitute 90% of congenital diaphragmatic hernias and are more common on the left side.
  14. Nerve supply of diaphragm with their applied surgical importance. [TU 2064,73/12]
    • Nerve supply 
    • - The diaphragm receives its nerve supply predominantly from the phrenic nerve (C3,4,5)
    • - The right phrenic nerve reaches the diaphragm just lateral to the inferior vena cava (IVC).
    • - The left phrenic nerve joins the diaphragm just lateral to the border of the heart, in a slightly more anterior plane than the right phrenic nerve. 


    • Clinical applications - 
    • 1. Diaphragmatic hernias - aquired or congenital 
    • 2. Paralysis of diaphragm
    • 3. Hiccups
  15. Mention origin, branches, and areas supplied by right coronary artery. [TU 2063/12]
    The right coronary artery (RCA) is an artery originating above the right cusp of the aortic valve. It travels down the right atrioventricular groove, towards the crux of the heart. It branches into the posterior descending artery and the right marginal artery. 

    In addition to supplying blood to the right ventricle (RV), the RCA supplies 25% to 35% of the left ventricle (LV).

    In 85% of patients (Right Dominant), the RCA gives off the posterior descending artery (PDA). In the other 15% of cases (Left Dominant), the PDA is given off by the left circumflex artery. The PDA supplies the inferior wall, ventricular septum, and the posteromedial papillary muscle.

    The RCA also supplies the SA nodal artery in 60% of patients. The other 40% of the time, the SA nodal artery is supplied by the left circumflex artery.
  16. Mention extent, branches and clinical importance of  Brachial artery. [TU 2066/6]
    Origin - The proximal brachial artery is the continuation of the axillary artery at the inferior border of teres major. After it emerges from the below teres major, it initially lies medial to the humerus where it is accompanied by the basilic vein and the median nerve. It sits medial to the biceps brachii muscle and anterior to the medial head of triceps.

    Branches - The profunda brachii is the first and main, branch of the brachial artery. It arises above the midpoint of the upper arm on the medial aspect of the vessel. However, as it courses posteriorly, is sweeps laterally and posteriorly to the humerus to sit lateral and posterior by the time it reaches the elbow.

    Distal to the profunda, the brachial artery gives off nutrient vessels to the humerus as is slowly courses more medially within the upper arm.

    As it approaches the elbow, it gives off two further named branches that are part of the arterial anastomosis at the elbow. These are the superior and inferior ulnar collateral arteries. Both of the ulnar collateral arteries arise from the medial surface of the brachial artery and course distally towards the medial aspect of the elbow. They give off smaller branches and anastomose with recurrent vessels that arise distal to the elbow joint.

    Termination - The brachial artery bifurcates to form the radial artery and ulnar artery in the cubital fossa at the level of the radial neck, below the bicipital aponeurosis. 

    Supply - The brachial artery supplies blood to the muscles of the upper arm by its branches and to the forearm and hand, by its continuation as the radial and ulnar arteries.
  17. Mention extent, branches and clinical importance of femoral artery. [TU 2066/6]
    Course - The femoral artery is the direct continuation of the external iliac artery of the abdomen, and is the great arterial trunk of the leg. It begins behind the inguinal ligament, at the mid-inguinal point, and it descends through the upper two-thirds of the thigh to the opening in the adductor magnus, through which it passes into the popliteal artery. The extent of the artery in the femoral triangle and in the subsartorial canal varies with the width of the sartorius, but usually the upper half is in the triangle and the lower half in the canal.

    • Branches
    • - superficial epigastric artery
    • - superficial circumflex iliac artery
    • - superficial external pudendal artery
    • - deep external pudendal artery
    • - terminal branches - profunda femoris and superficial femoral artery


    • Clinical significance - 
    • - Pulse 
    • - Peripheral arterial disease
Author
prem77
ID
330519
Card Set
Basic Science CTVS - 62 anatomy and physiology
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Anatomy and physiology
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