CVR anatomy 🫁💓 Flashcards

Question

What is the clinical relevance of injury to the vagus nerve

Answer 1

Dysfunctional swallowing and speech (hoarseness of the voice

Answer 2

weakness or paralysis of the ipsilateral SCM and trapezius

Answer 3

Weakness or paralysis of the ipsilateral tongue

Answer 4

Muscular tube Part of the respiratory and GI systems Three parts > nasopharynx, oropharynx, laryngopharynx Formed by constrictor muscles Swallowed fluid and food prevented from entering the larynx by the epiglottis > diverted into the oesophagus instead

Answer 5

Cartilaginous skeleton Extrinsic muscles Intrinsic muscles

Answer 6

Move the individual cartilages and the vocal cords Innervated by the vagus nerve (most via the recurrent laryngeal branch)

Answer 7

Cartilaginous skeleton - paired and unpaired cartilages – some are palpable Connected by small joints, ligaments and muscles

Answer 8

Move the larynx as a whole ‘unit’ with speech and swallowing Suprahyoid and infrahyoid muscles Vocal ligaments within the thyroid cartilage

Answer 9

Produces thyroid hormone Two lobes lie either side of the larynx Lobes connected across the midline by the isthmus Supplied by branches of the external carotid and the subclavian arteries Recurrent laryngeal nerves lie close by – can be injured by removal of the thyroid

Answer 10

The sternum lies anteriorly in the midline of the thoracic cage. It is composed of three parts. Manubrium body Xiphoid process

Answer 11

The manubrium is the superior part of the sternum: ● the superior border has a notch in it – the suprasternal (jugular) notch. ● laterally, it articulates with the clavicle (collarbone) at the sternoclavicular joint, and with the first rib. ● inferiorly, it articulates with the body of the sternum at the manubriosternal joint, also known as the sternal angle (or the ‘angle of Louis’).

Answer 12

The body is inferior to the manubrium: ● it articulates with ribs 2 – 7. ● the second rib articulates with the sternum at the sternal angle (i.e. with the inferior part of the manubrium and the superior part of the body). ● inferiorly, it articulates with the xiphoid process.

Answer 13

The xiphoid process (or xiphisternum) is inferior to the body: ● it is small and variable in shape. ● the seventh rib articulates with the inferior part of the body of the sternum and the superior part of the xiphoid process.

Answer 14

* The anterior parts of the ribs are composed of costal cartilage. * The ribs articulate with their costal cartilages at costochondral joints.. * The ribs articulate posteriorly with the thoracic vertebrae at costovertebral joints. * Adjacent ribs are connected to each other by intercostal muscles, which lie in the intercostal spaces.

Answer 15

Ribs 11 and 12 don't have costal cartilages and therefore don't articulate with the sternum

Answer 16

Ribs 8-10 Their costal cartilages don't individually articulate with the sternum but rather they join together and connect to the 7th costal cartilage which does articulate with the sternum

Answer 17

The costal cartilages of ribs 1 - 7 articulate directly with the sternum at sternocostal joints – they are ‘true’ ribs.

Answer 18

* The costal cartilages of ribs 7 - 10 form it Palpable

Answer 19

Look similar * Ribs 3 - 9 are typical ribs. They have a head, neck, tubercle, and body (shaft).

Answer 20

Look different from other ribs Ribs 1 - 2 and 10 - 12 are atypical, for various reasons. For example, ribs 1, 11 and 12 are much shorter than typical ribs.

Answer 21

Twelve thoracic vertebrae (T1 - T12) lie posteriorly in the midline of the thoracic cage. The spinous processes of the thoracic vertebrae are palpable in the midline of the back. The thoracic vertebrae articulate with the posterior parts of the ribs at costovertebral joints. Typically the head of the rib articulates with the vertebral body and the tubercle of the rib articulates with the transverse process of the vertebra.

Answer 22

The manubrium, the first ribs and the first thoracic vertebra form the boundary of the superior thoracic aperture – the ‘passageway’ through which structures pass between the neck and the thorax.

Answer 23

● The ribs provide one coordinate (e.g. is the patient’s pain at the level of rib 2 or rib 8?). The second rib lies at the level of the sternal angle. From here we can count ribs and intercostal spaces. ● A series of imaginary vertical lines provide a second coordinate.

Answer 24

● Midsternal line ● Midclavicular line ● Anterior axillary line ● Mid-axillary line ● Posterior axillary line ● Scapular line ● Midvertebral line

Answer 25

The skin of the thoracic wall is innervated by spinal nerves T1 – T12 . Sensation from the skin of the thoracic wall (touch, pain, temperature) reaches our conscious perception via somatic sensory fibres in the spinal nerves

Answer 26

A dermatome is an area of skin innervated by a single spinal nerve. Each pair of thoracic spinal nerves supplies a ‘strip’ of skin around the chest wall.

Answer 27

Somatic motor fibres in spinal nerves T1 -12 innervate the skeletal muscles of the thoracic wall and sympathetic fibres innervate sweat glands and the smooth muscle of blood vessels and hair follicles in the skin (arrector pili).

Answer 28

The breasts (mammary glands) are superficial to the muscles of the chest wall. In females, the breasts are well developed but in males, they are rudimentary. The female breast grows during puberty and pregnancy. Breast tissue extends towards the anterior axilla (armpit) – this part of the breast is the axillary tail.

Answer 29

● Fat - variable amounts. ● Glandular / secretory tissue arranged in lobules. ● Ducts which converge on the nipple. The areola is the region of pigmented skin that surrounds the nipple. ● Connective tissue and ligaments. ● Blood vessels and lymphatics.

Answer 30

The breast is primarily supplied by branches from the: ● internal thoracic artery (which arises from the subclavian artery) ● axillary artery. Venous blood returns to the axillary and internal thoracic veins.

Answer 31

The internal thoracic artery courses deep to the lateral edge of the sternum. It gives rise to anterior intercostal arteries that supply the breast and the intercostal spaces .

Answer 32

The breast is supplied with somatic nerves and sympathetic fibres via the intercostal nerves. Somatic sensory fibres innervate the skin of the breast. Sympathetic fibres innervate smooth muscle in the blood vessel walls and nipple.

Answer 33

Intercostal muscles lie in the intercostal spaces between the ribs. Within each intercostal space, there are three layers of muscles: * External intercostal is most superficial. * Internal intercostal lies deep to the external intercostal. * Innermost intercostal lies deep to the internal intercostal.

Answer 34

Most lymph from the breast drains to lymph nodes in the axilla. However, because axillary nodes communicate with other groups of lymph nodes in the thorax, the patterns of lymph drainage are complex. There are five groups of lymph nodes in the axilla: central, pectoral, humeral, subscapular, and apical. ● They drain the breast, upper limb, chest wall, scapular region, and the abdominal wall. ● The apical nodes (in the apex of the axilla) receive lymph from all other lymph nodes in the axilla. Because they drain most of the lymph from the breast, the axillary lymph nodes are often involved in the spread of breast cancer.

Answer 35

There are five groups of lymph nodes in the axilla: central, pectoral, humeral, subscapular, and apical. ● They drain the breast, upper limb, chest wall, scapular region, and the abdominal wall.

Answer 36

The apical nodes (in the apex of the axilla) receive lymph from all other lymph nodes in the axilla. Because they drain most of the lymph from the breast, the axillary lymph nodes are often involved in the spread of breast cancer.

Answer 37

Pectoralis major is the most superficial muscle of the anterior chest wall. It attaches to the upper humerus, the clavicle and the upper six ribs.

Answer 38

● Pectoralis minor is a smaller muscle that lies deep to pectoralis major. It attaches to the scapula (shoulder blade) and ribs 3-5.

Answer 39

Is a superficial muscle that sweeps around the lateral aspect of the thoracic cage. It attaches to the scapula and the upper eight ribs.

Answer 40

Respiratory distress

Answer 41

Rib fractures result from blunt trauma to the chest wall (falls, traffic accidents, assault). They are painful and the pain is typically worse on inspiration. If there is concern about multiple rib fractures or a pneumothorax a chest X-ray or CT scan may be required to assess the extent of the injury. Isolated rib fractures are treated conservatively (i.e. left to heal on their own) but patients need adequate pain relief. Multiple rib fractures are more serious (and complex to manage), as they can lead to dysfunctional movements of the chest wall and inadequate ventilation.

Answer 42

Patients with shingles present with a red, painful, and itchy rash, typically over the chest or abdomen on one side of the body only. The rash typically appears in a strip-like distribution, as it affects dermatomes. Shingles affects people who have previously had chickenpox. After an infection with chickenpox, the virus lays dormant in the dorsal root ganglion. When reactivated, it causes a rash and pain in the dermatome associated with the affected spinal nerve.

Answer 43

Because most lymph from the breast drains to the axillary lymph nodes, breast malignancy typically metastasizes (spreads) to these nodes first. A malignant axillary node may be palpable as a lump in the armpit and noticed before a mass in the breast itself. If a breast mass is confirmed as malignant, the axillary lymph nodes are biopsied to assess if malignancy has metastasized to them. If so, they are removed as part of a patient’s treatment. Because the axillary nodes drain lymph from the upper limb, their removal can lead to fluid accumulation and swelling in the affected upper limb, a condition called lymphoedema.

Answer 44

* three layers of intercostal muscles and their associated membranes * an intercostal neurovascular bundle, comprising an intercostal nerve, an intercostal artery, and an intercostal vein.

Answer 45

The muscles in the intercostal spaces attach to the rib above and rib below. There are three layers of muscles in the intercostal spaces. Their fibres run in different directions to each other and hence act on the ribs in different ways.

Answer 46

External intercostal is most superficial. Its fibres are orientated antero-inferiorly. * Contraction pulls the ribs superiorly, hence is it most active in inspiration. * In the anterior part of the intercostal space, the muscle becomes membranous and forms the external intercostal membrane.

Answer 47

Internal intercostal lies deep to the external intercostal. Its fibres run perpendicular to those of the external intercostal, running in a postero-inferior direction. * Contraction pulls the ribs inferiorly, hence is it most active in expiration. * The internal intercostal becomes membranous in the posterior part of the intercostal space and forms the internal intercostal membrane.

Answer 48

The innermost intercostal lies in the posterior part of the intercostal space deep to the internal intercostal. Its fibres are orientated in the same direction as those of the internal intercostal.

Answer 49

fascia lies deep to the innermost intercostal and superficial to the parietal pleura, which surrounds the lung

Answer 50

The neurovascular bundle in each intercostal space lies in the plane between the internal and innermost intercostal muscle. It supplies the intercostal muscles, the overlying skin, and the underlying parietal pleura

Answer 51

The neurovascular bundle for each intercostal space lies along the inferior border of the rib superior to the space. It lies in a shallow costal groove on the deep surface of the rib. In medical procedures that involve piercing the intercostal space (such as placing a chest drain), the incision is made in the middle to lower part of the intercostal space, to avoid the intercostal vessels and nerve. Smaller collateral branches run in the same tissue plane, but in the lower part of the intercostal space

Answer 52

* Anterior and posterior intercostal arteries supply the anterior and posterior parts of the intercostal space, respectively. * The anterior intercostal arteries are branches of the internal thoracic artery (a branch of the subclavian artery). * The posterior intercostal arteries are branches from the descending aorta in the posterior thorax.

Answer 53

* Anterior intercostal veins drain into the internal thoracic vein and posterior intercostal veins drain into the azygos system of veins

Answer 54

The intercostal nerves are somatic and contain motor and sensory fibres. They innervate the intercostal muscles, the skin of the chest wall and the parietal pleura. Intercostal nerves also carry sympathetic fibres.

Answer 55

Two layers of membranes - the pleurae - cover the lungs and the structures passing into and out of the lungs (the pulmonary blood vessels and the main bronchi). * The parietal pleura lines the inside of the thorax. * The visceral pleura covers the surface of the lungs and extends into the fissures. A very thin pleural cavity (or space) lies between the parietal and visceral pleura.

Answer 56

The parietal pleura is visible with the naked eye, but the visceral pleura is not. The two layers of pleura are continuous with each other. The pleural cells produce a small amount of pleural fluid, which fills the pleural cavity. The pleura and pleural fluid are integral to the mechanics of breathing.

Answer 57

* The cervical pleura covers the apex of the lung. * The costal pleura lies adjacent to the ribs. * The mediastinal pleura lies adjacent to the heart. * The diaphragmatic pleura lies adjacent to the diaphragm.

Answer 58

The costodiaphragmatic recess is a ‘gutter’ around the periphery of the diaphragm, where the costal pleura becomes continuous with the diaphragmatic pleura. A smaller costomediastinal recess lies at the junction of the costal and mediastinal pleura. These are potential spaces that the lungs expand into during deep inspiration

Answer 59

The parietal pleura is innervated by the intercostal nerves that innervate the overlying skin of the chest wall. Somatic sensory fibres in these nerves carry sensation to our consciousness. Injury to the parietal pleura (e.g. tearing by a fractured rib) is typically very painful.

Answer 60

* The visceral pleura is innervated by autonomic sensory nerves (visceral afferents). Sensation from visceral afferents usually does not reach our conscious perception.

Answer 61

● The right lung has three lobes – a superior (upper), middle, and inferior (lower) lobe. ● The left lung has two lobes – a superior and inferior lobe. An anterior extension of the superior lobe – the lingula (Latin for ‘small tongue’) – extends over the heart.

Answer 62

* Both lungs have an oblique fissure. In the left lung, it separates the superior and inferior lobes. In the right lung, it separates the superior and middle lobes from the inferior lobe. * The right lung has a horizontal fissure. It separates the superior lobe from the middle lobe.

Answer 63

* Costal surface - adjacent to the ribs. * Mediastinal surface - adjacent to the heart. * Diaphragmatic surface - the inferior surface of the lung

Answer 64

* Anterior border - sharp and tapered. * Posterior border – thick and rounded. * Inferior border - sharp and tapered.

Answer 65

The surfaces of the lungs bear indentations (impressions) created by adjacent structures. Rib markings are seen on the costal surfaces of both lungs. Indentations created by the left ventricle and the descending aorta are seen on the mediastinal surface of the left lung and indentations made by the superior vena cava and azygos vein are seen on the mediastinal surface of the right lung.

Answer 66

The root of each lung lies between the heart and the lung and comprises the pulmonary artery, pulmonary veins, and main bronchus. Pleura encloses the root of the lung like a sleeve.

Answer 67

The hilum of the lung (plural = hila) is the region on the mediastinal surface of the lung where the pulmonary artery, pulmonary veins and main bronchus enter and exit the lung. The positions of the pulmonary artery and main bronchus relative to each other at the hilum is slightly different between the right and left lungs.

Answer 68

* At the hilum of the right lung, the pulmonary artery lies anterior to the main bronchus. * At the hilum of the left lung, the pulmonary artery lies superior to the main bronchus.

Answer 69

At both the right and left hila, the two pulmonary veins are usually the most anterior and inferior vessels.

Answer 70

The trachea bifurcates into the left and right main bronchi at the level of the sternal angle. Internally, the point of bifurcation is marked by a ridge of cartilage called the carina. The right main bronchus is shorter, wider and descends more vertically than the left main bronchus thus a foreign body entering the trachea is more likely to enter the right main bronchus than the left.

Answer 71

branching system of tubes that conduct air into and out of the lungs.

Answer 72

Each main (primary) bronchus divides into lobar (secondary) bronchi; three in the right lung and two in the left lung (i.e. one lobar bronchus for each lobe).

Answer 73

Each lobar bronchus divides to give rise to segmental (tertiary) bronchi. There are approximately ten segmental bronchi in each lung.

Answer 74

Each segmental bronchus supplies a functionally independent region of the lung called a bronchopulmonary segment; there are ten segments in each lung. Because they are supplied by their own segmental bronchus and blood vessels, a segment may be resected (surgically removed) without affecting the rest of the lung.

Answer 75

Segmental bronchi within each bronchopulmonary segment continue to divide into bronchioles. Bronchioles become smaller with each division. The very smallest bronchioles conduct air to and from the alveoli - the site of gas exchange within the lung.

Answer 76

Autonomic nervous system

Answer 77

The pulmonary arteries carry deoxygenated blood to the lungs. Bronchial arteries from the descending aorta also supply the lungs.

Answer 78

The pulmonary veins return oxygenated blood to the heart from the lungs. Bronchial veins return blood to the azygos system of veins

Answer 79

Autonomic nerves innervate the lungs. * Parasympathetic fibres stimulate: * constriction of bronchial smooth muscle (bronchoconstriction) * secretion from the glands of the bronchial tree. * Sympathetic fibres: * stimulate relaxation of bronchial smooth muscle (bronchodilation) * inhibit secretion from the glands.

Answer 80

Visceral afferents (visceral sensory fibres) accompany the sympathetic and parasympathetic nerves and relay sensory information from the lungs and visceral pleura to the CNS, but these sensations do not usually reach our conscious perception. Remember that somatic sensory fibres carried in the intercostal nerves innervate the parietal pleura.

Answer 81

Lymph from the lungs ultimately drains into the venous system via the thoracic duct or right lymphatic duct.

Answer 82

We can auscultate the lungs by placing a stethoscope over the chest wall. When we listen to healthy lungs, we hear air moving into and out of the lungs with inspiration and expiration. We may hear abnormal sounds, like wheeze or ‘crackles’, or we may not hear any sounds. Pathology can affect just one lobe of a lung, so when we examine the lungs, we must auscultate each lobe separately. To do this, we need to know where each lobe lies relative to the chest wall.

Answer 83

The surface markings of the inferior borders of the lungs and the inferior extent of the parietal pleura are different as the parietal pleura extends more inferiorly than the inferior border of the lung. The space between them is the costodiaphragmatic recess.

Answer 84

The apex of each lung projects into the lower neck, just superior to the medial end of the clavicle.

Answer 85

The inferior border of the lungs lies at the level of the: * 6th rib anteriorly (midclavicular line) * 8th rib laterally (midaxillary line) * 10th rib posteriorly (at the vertebral column).

Answer 86

The parietal pleura extends to the: * 8th rib anteriorly (midclavicular line) * 10th rib laterally (midaxillary line) * 12th rib posteriorly (at the vertebral column).

Answer 87

The oblique fissure of both the left and right lungs extends from the 4th rib posteriorly to the 6th costal cartilage anteriorly; the fissure runs deep to the 5th rib. The horizontal fissure of the right lung extends anteriorly from the 4th costal cartilage and intersects the oblique fissure.

Answer 88

The diaphragm is a broad, thin, domed sheet of skeletal muscle. * It separates the thoracic and abdominal cavities from each other. * Its superior (thoracic) surface is adjacent to the parietal pleura. * Openings (apertures) in the diaphragm allow the passage of structures between the thorax and abdomen (e.g. the aorta, inferior vena cava, and oesophagus). * Its function is integral to the mechanics of breathing (ventilation).

Answer 89

The diaphragm is attached to the xiphoid process, costal margin (and to the tips of the 11th and 12th ribs) and the lumbar vertebrae. The central part of the diaphragm is not muscular, but fibrous - the central tendon.

Answer 90

* When the diaphragm contracts during inspiration, the muscle fibres of the right and left domes are pulled towards their peripheral attachments, and the domes flatten. This increases the intrathoracic volume for the lungs to expand. * During expiration, the diaphragm relaxes and domes superiorly. This decreases the intrathoracic volume and drives expiration of air from the lungs.

Answer 91

The right and left phrenic nerves innervate the right and left sides of the diaphragm, respectively. They are somatic nerves, formed in the neck by fibres from the C3, C4 and C5 spinal nerves, and hence contain motor and sensory fibres.

Answer 92

The mechanics of breathing (breathing is also called ventilation) are complex. The basic principles are: * Muscles move the thoracic cage and change the dimensions of the thoracic cavity. * The dimensions of the thoracic cavity determine intrathoracic volume. * Changes in intrathoracic volume alter intrathoracic pressure. * Pressure changes inside the thorax drive inspiration and expiration. * Different muscles are involved in normal, vigorous, and forced ventilation.

Answer 93

During ventilation, the dimensions of the thoracic cavity change in three planes: * Vertically - due to the contraction and relaxation of the diaphragm. * Laterally - due to contraction of the intercostal muscles which move the ribs. * Antero-posteriorly (AP) – due to movement of the sternum secondary to movement of the ribs.

Answer 94

The pleural fluid creates surface tension between the parietal pleura lining the thoracic cavity and the visceral pleura on the surface of the lung. Surface tension keeps the lung and thoracic wall ‘together’, so when the thoracic cavity changes volume, the lung changes volume with it. Surface tension between the two pleural membranes keeps them in contact with each other and prevents the lung from ‘collapsing’ away from the thoracic wall.

Answer 95

If the surface tension is ‘broken’ (e.g. by a penetrating injury of the chest that punctures the parietal pleura and introduces air into the pleural cavity - pneumothorax) then ventilation may become dysfunctional.

Answer 96

In inspiration: * The diaphragm and external intercostal muscles contract, increasing the intrathoracic volume (the external intercostals pull the ribs superiorly and laterally, and the ribs pull the sternum superiorly and anteriorly, increasing the AP and lateral dimensions of the thoracic cavity). * The lungs expand (increase in volume) with the thoracic wall (due to surface tension). * The pressure in the lungs decreases below atmospheric pressure and air is drawn into the lungs.

Answer 97

The diaphragm and external intercostal muscles relax, decreasing the intrathoracic volume (the internal intercostals pull the ribs inferiorly, and the ribs pull the sternum inferiorly and posteriorly, decreasing the AP and lateral dimensions of the thoracic cavity). * The lungs recoil (decrease in volume). * The pressure in the lungs increases above atmospheric pressure and air is expelled from the lungs.

Answer 98

* In normal, quiet breathing, inspiration is active and is mainly driven by movement of the diaphragm, but expiration is passive. * In vigorous breathing (e.g. exercise) the intercostal muscles become important. Active expiration uses the internal intercostal muscles. * In very vigorous or forced breathing (e.g. in an exacerbation of asthma or COPD, or in strenuous exercise) the accessory muscles of breathing (sternocleidomastoid, pectoralis major and minor, serratus anterior) contribute to movement of the ribs and aid ventilation. The anterior abdominal wall muscles contribute to forced expiration.

Answer 99

The pleura can become inflamed or injured (e.g. torn by a fractured rib). Pleuritic chest pain is typically sharp, well localised (i.e. the patient can pinpoint it on the chest wall), and worse on inspiration. The pain is felt from the parietal pleura only.

Answer 100

A pneumothorax is the presence of air in the pleural cavity. It is usually caused by trauma (e.g. a fractured rib tearing the parietal pleura) but can happen spontaneously (tear in the visceral pleura). If air keeps entering the pleural cavity but cannot escape, a tension pneumothorax develops, in which a rapidly increasing volume of air progressively compresses the lung, heart, great vessels and the opposite lung over to the contralateral side of the thorax. This is rapidly fatal without immediate intervention. Patients with a tension pneumothorax present with severe respiratory distress.

Answer 101

Haemothorax describes a collection of blood in the pleural cavity and occurs secondary to trauma when blood vessels are torn or cut.

Answer 102

Pleural effusion describes the presence of excess fluid in the pleural cavity. It is not a diagnosis - the fluid could be pus from infection, blood, or fluid related to malignancy. A chest drain is used to remove air and / or fluid from the pleural space. The surface anatomy of the heart and lungs must be considered to ensure the tip of the drainage tube does not injure them. An incision is made in the lower part of the chosen intercostal space, to avoid the neurovascular bundle, which lies in the costal groove of the rib superior to the space.

Answer 103

Lung cancer is one of the most common types of cancer seen in the UK. Lung cancer may be primary (i.e. cancer of the lung tissue or bronchi) or secondary (i.e. cancer from elsewhere that has metastasized to the lungs). Both primary and secondary cancer of the lung is common. Mesothelioma is a malignancy of the pleura.

Answer 104

Pulmonary embolism is a blood clot in the pulmonary circulation. The clot usually forms in the deep veins in one of the legs and is carried in the venous circulation back to the right side of the heart and into the pulmonary trunk. A very large clot lodging in the pulmonary trunk or in one of the pulmonary arteries causes severe respiratory distress and may be rapidly fatal. Smaller clots that occlude smaller pulmonary vessels may cause infarction of the part of the lung they supply.

Answer 105

Patients commonly present with breathlessness or shortness of breath (dyspnoea). The use of the accessory muscles of respiration is a sign of respiratory distress. Patients in respiratory distress will often ‘fix’ their upper limbs steady (e.g. by holding onto the side of the bed or chair), which allows the upper limb muscles that attach to the chest wall (pectoralis major, pectoralis minor and serratus anterior) to move the ribs and aid ventilation.

Answer 106

Injury to the phrenic nerve, the C3-5 spinal nerves or the C3-5 spinal cord segments on one side may paralyse the ipsilateral side of the diaphragm, but in a healthy person, this may not cause symptoms. Patients with bilateral paralysis of the diaphragm require ventilatory support.

Answer 107

The mediastinum is the part of the thoracic cavity that lies between the lungs. The mediastinum contains all the thoracic viscera apart from the lungs. The mediastinum extends from the: * superior thoracic aperture superiorly to the diaphragm inferiorly * sternum anteriorly to the thoracic vertebrae posteriorly

Answer 108

* The heart and pericardium (the fibrous sac around the heart) * The great vessels that enter and leave the heart * The veins that drain the chest wall * The trachea and main bronchi * The oesophagus * Nerves (somatic and autonomic) * Lymphatics * The thymus gland

Answer 109

The ‘line’ between these compartments runs from the sternal angle anteriorly to the T4/T5 junction posteriorly.

Answer 110

lies between the posterior aspect of the sternum and the anterior aspect of the pericardial sac. It is a narrow space that contains the thymus gland in children and its remnant in adults.

Answer 111

Contains the heart inside the pericardial sac, the pulmonary trunk, and the ascending aorta.

Answer 112

Lies between the posterior aspect of the pericardial sac and the vertebrae.

Answer 113

* arch of the aorta and its three branches * superior vena cava and its tributaries - the left and right brachiocephalic veins * trachea * oesophagus * phrenic nerves (left and right) and vagus nerves (left and right) * thoracic duct * thymus gland

Answer 114

* The ascending aorta is the short, first part. It gives rise to the coronary arteries, which supply the myocardium. * The arch of the aorta curves posteriorly. It lies in the superior mediastinum. * The descending (thoracic) aorta descends through the posterior mediastinum and into the abdomen posterior to the diaphragm.

Answer 115

* First, the brachiocephalic trunk. It bifurcates into the right common carotid artery which supplies the right side of the head and neck, including the brain, and the right subclavian artery which supplies the right upper limb. * Second, the left common carotid artery, which supplies the left side of the head, neck, and brain. * Third, the left subclavian artery, which supplies the left upper limb.

Answer 116

The arch of the aorta contains the aortic bodies where chemoreceptors are located. These receptors constantly monitor arterial oxygen and carbon dioxide. This visceral sensory information travels back to the CNS along the path of the vagus nerve and results in reflex responses that regulate ventilation.

Answer 117

The ligamentum arteriosum is a fibrous, cord-like connection between the pulmonary trunk and the arch of the aorta. It is the remnant of the ductus arteriosus, a foetal circulatory shunt. In the foetus, gas exchange occurs at the placenta, not in the lungs. The ductus arteriosus diverts most of the blood entering the pulmonary trunk directly to the aortic arch (only a small amount of blood circulates through the foetal lungs; enough for them to develop). When a baby starts to use their lungs at birth, the ductus arteriosus closes, and blood in the pulmonary trunk enters the lungs.

Answer 118

* The superior vena cava (SVC) returns blood to the heart from the head, neck, and upper limbs. The SVC and its tributaries lie in the superior mediastinum. * The SVC is formed by the union of the left and right brachiocephalic veins (brachium = arm; cephalic = head).

Answer 119

Each brachiocephalic vein (left and right) is formed by the union of the internal jugular vein (which drains the head and neck) and the subclavian vein (which drains the upper limb).

Answer 120

The inferior vena cava (IVC) returns blood to the heart from all regions inferior to the diaphragm (abdomen, pelvis, and lower limbs). The thoracic part of the IVC is very short – it enters the right atrium as soon as it enters the thorax through the diaphragm.

Answer 121

The trachea conducts air to and from the left and right main bronchi. It is semi-rigid due to C-shaped, incomplete rings of cartilage in its walls. * It extends from the larynx in the midline of the neck into the superior mediastinum and is palpable just superior to the suprasternal notch. * It terminates at the level of the sternal angle (and junction between the T4 and T5 vertebrae) by bifurcating into the left and right main bronchi.

Answer 122

The oesophagus is a muscular tube that extends from the pharynx in the midline of the neck to the stomach. ‘Waves’ of contractions of smooth muscle in the oesophageal wall move swallowed food and fluid distally (peristalsis). In the superior mediastinum, the oesophagus lies in the midline of the thorax, posterior to the trachea. It descends into the posterior mediastinum.

Answer 123

The left and right phrenic nerves, formed by fibres from the C3, C4 and C5 spinal nerves, innervate the diaphragm. They are somatic nerves and contain motor and sensory fibres. They descend through the neck and enter the thorax through the superior thoracic aperture. They course over the pericardium and pierce the diaphragm.

Answer 124

The left and right vagus nerves (CN X) arise from the brainstem and contain somatic sensory, somatic motor and parasympathetic fibres. They innervate structures of the thorax and abdomen, in addition to the head and neck. * They descend through the neck alongside the internal carotid artery and internal jugular vein and enter the thorax via the superior thoracic aperture. * They each give rise to a recurrent laryngeal nerve (RLN), which ascend back up into the neck to innervate the muscles of the larynx. Descend into the thorax posterior to the root of the lung * They contribute parasympathetic fibres to the heart, lungs, and oesophagus. * They traverse the diaphragm and convey parasympathetic fibres to most of the abdominal viscera.

Answer 125

The left recurrent laryngeal nerve loops under the arch of the aorta before ascending back up the left side of the neck (alongside the trachea) to the larynx.

Answer 126

The right recurrent laryngeal nerve descends anterior to the right subclavian artery and then loops under the inferior border of the artery before ascending back up the right side of the neck (between the trachea and oesophagus) to the larynx.

Answer 127

The thoracic duct is a major channel for lymphatic drainage from most regions of the body. It ascends through the posterior mediastinum and into the superior mediastinum, where it empties into the venous system at the union of the left internal jugular vein and left subclavian vein.

Answer 128

Thymus Gland The thymus is a lymphoid organ. It lies anteriorly in the superior mediastinum. It is important in children, but atrophies with age, eventually becoming fatty

Answer 129

The pericardium is a tough, fibrous sac that encloses the heart like a loose-fitting bag; it is loose to allow for the movement of the heart within it. The pericardium is composed of two layers. * a tough, outer fibrous layer that is attached superiorly to the great vessels and inferiorly to the central tendon of the diaphragm. * a thin, inner serous layer which has two parts: the parietal layer lines the inner aspect of the fibrous pericardium, and the visceral layer covers the surface of the heart. The two layers are continuous with each other.

Answer 130

The narrow space between the two layers of serous pericardium is the pericardial cavity. It contains a small amount of pericardial fluid that lubricates the serous membranes and allows them to slide over each other with movements of the heart. The left and right phrenic nerves give rise to sensory branches that innervate the fibrous pericardium.

Answer 131

The heart is shaped roughly like a pyramid lying on one of its sides. The ‘point’ of the pyramid is the apex, which projects to the left of the sternum towards the left lung.

Answer 132

* base – it ‘faces’ posteriorly, so is also called the posterior surface. * inferior surface – it lies on the central tendon of the diaphragm, so is also called the diaphragmatic surface. * anterior surface – it ‘faces’ the sternum and ribs, so is also called the sternocostal surface. * The left and right sides of the heart ‘face’ the lungs and are referred to as the pulmonary surfaces.

Answer 133

* Base / posterior surface = left atrium, part of the right atrium * Inferior / diaphragmatic surface = left ventricle, part of the right ventricle * Anterior / sternocostal surface = right ventricle * Left pulmonary surface = left ventricle * Right pulmonary surface = right atrium

Answer 134

The apex is formed by the left ventricle. It lies at the left 5th intercostal space in the midclavicular line and the apex beat is palpable here.

Answer 135

The heart is also described in terms of its ‘edges’, or borders. These are particularly important for clinical examination of the heart and for interpreting chest X-rays. The borders of the heart correspond to specific parts of the heart, which are: * Right border = right atrium * Left border = left ventricle * Inferior border = right ventricle and part of the left ventricle.

Answer 136

Right border = lies lateral to the right sternal edge, from the right 3rd costal cartilage to the right 6th costal cartilage.

Answer 137

Left border = extends from the left 2nd intercostal space to the left 5th intercostal space in the midclavicular line (i.e. the apex).

Answer 138

Superior border = lies along the line connecting the superior extents of the right and left borders (i.e. from the right 3rd costal cartilage to the left 2nd intercostal space).

Answer 139

Inferior border = lies along the line connecting the inferior end of the right border with the apex (mostly formed by the right ventricle).

Answer 140

The auricles (auricular appendages) are outpouchings from the walls of the right and left atria. They are named because of their ear-like appearance.

Answer 141

PDA is a type of congenital cardiac anomaly. The ductus arteriosus usually closes immediately after birth. In some infants, the ductus arteriosus does not close and remains open (patent). After birth, the pressure in the aorta exceeds the pressure in the pulmonary trunk, hence blood flows through a patent ductus arteriosus from the aorta into the pulmonary trunk. Over time, increased flow through the pulmonary vessels can lead to pulmonary hypertension (high pressure in the vessels of the lungs) which strains the right side of the heart.

Answer 142

Cancer at the apex of the lung may involve the recurrent laryngeal nerve, which supplies most of the muscles of the larynx. Nerve injury results in weakness or paralysis of the ipsilateral intrinsic laryngeal muscles, which move the larynx and the vocal cords (we will look at the larynx in detail in sessions 7 and 8). Hoarseness results as the patient can no longer fully adduct their vocal cords.

Answer 143

The pericardial space allows the heart to move within the pericardial sac with each contraction. Pericardial effusion is an increase in fluid volume in the pericardial space. Pericardial effusion may result from inflammation of the pericardium (a condition called pericarditis) or an accumulation of blood (due to trauma). Rapid fluid accumulation in the pericardial space (e.g. blood due to a stab wound) can be rapidly fatal because the fibrous pericardium cannot stretch and so the heart is compressed and unable to fill properly - a condition called cardiac tamponade.

Answer 144

Grooves on the external surface of the heart that contain the major coronary arteries

Answer 145

The right coronary artery and its branches supply parts of the conducting system of the heart, the right atrium, right ventricle, part of the left ventricle, and part of the interventricular septum.

Answer 146

The main branches of the right coronary artery and the territories they supply are as follows. * Branches to the sinoatrial node and atrioventricular node supply these major components of the electrical conducting system of the heart. * The right marginal artery supplies the inferior border of the heart. * The posterior interventricular artery (PIV) is the continuation of the right coronary artery on the inferior (diaphragmatic) surface of the heart. It runs in the posterior interventricular sulcus and supplies both ventricles.

Answer 147

The left coronary artery and its branches supply parts of the conducting system of the heart, the left atrium, most of the left ventricle, part of the right ventricle, and part of the interventricular septum. The LCA only runs a short course before it divides into two large terminal branches. This short segment of the left coronary artery is the left main stem (‘LMS’). The two terminal branches of the left coronary artery are the: * Anterior interventricular artery (or the left anterior descending; ‘LAD’). * Circumflex artery (abbreviated to ‘Cx’).

Answer 148

The main branches of the left coronary artery and the territories they supply are as follows. * The anterior interventricular artery (LAD) runs in the anterior interventricular sulcus towards the apex. It supplies both ventricles. * One or two diagonal branches arise from the LAD. * The circumflex artery runs around the heart onto the inferior / diaphragmatic surface. It supplies the left atrium, part of the right ventricle and the left ventricle. * The left marginal artery arises from the circumflex and supplies the left ventricle.

Answer 149

The posterior interventricular artery, which supplies a significant portion of the left ventricle, may arise from the right or left coronary artery. The origin of the posterior interventricular artery determines if an individual has a right dominant or a left dominant coronary circulation. * Most people have a right dominant circulation; the PIV arises from the right coronary. In these people, both the right and left coronary arteries supply the left ventricle. * In those with a left-dominant circulation, the PIV arises from the circumflex artery; the left coronary artery supplies the entire left ventricle.

Answer 150

This is important in clinical practice. In someone with a right-dominant circulation, occlusion of the left main stem would impair blood flow to part of, but not the entire left ventricle. In someone with a left-dominant coronary circulation, blockage of the left main stem occludes blood flow to the entire left ventricle.

Answer 151

From the right atrium, blood flows into the right ventricle via the right atrioventricular valve, also called the tricuspid valve. The flow of blood is mostly passive, but the right atrium does contract to empty fully

Answer 152

* interatrial septum which separates it from the left atrium * fossa ovalis – a depression in the interatrial septum. It is the remnant of the foetal foramen ovale. In the foetus the foramen ovale shunts oxygenated blood from the right atrium to the left atrium, hence bypassing the lungs. * crista terminalis – a muscular ridge that separates the smooth-walled posterior part of the atrium from the anterior part, which has a ridged, muscular wall. The ridges are pectinate muscles and extend into the right auricle. The parts of the right atrium on either side of the crista have different embryological origins.

Answer 153

The right ventricle pumps the deoxygenated blood that it receives from the right atrium into the pulmonary trunk, which bifurcates into a left and right pulmonary artery. The pulmonary valve at the entrance of the pulmonary trunk prevents backflow of blood into the right ventricle. As contraction of the right ventricle propels blood into the pulmonary trunk, the wall of the right ventricle is thicker than that of the right atrium

Answer 154

* interventricular septum which separates it from the left ventricle * trabeculae carneae – muscular ridges on the internal wall * papillary muscles – modified regions of trabeculae carneae, which project into the lumen of the ventricle * chordae tendineae – fibrous cords which connect the tips of the papillary muscles to the tricuspid valve * moderator band – a modified region of the trabeculae carneae which connects the interventricular septum to one of the papillary muscles.

Answer 155

The left atrium receives oxygenated blood from the lungs via the pulmonary veins (two from each lung). Like the right atrium, it has a thinner wall compared to the ventricles and internally has a smooth-walled posterior part and an anterior part bearing pectinate muscles. Again, this reflects the left atrium’s development from two different embryological structures. From the left atrium, blood flows into the left ventricle via the left atrioventricular valve, also called the mitral valve. The flow of blood is mostly passive, but the left atrium does contract to empty fully.

Answer 156

The left ventricle pumps the oxygenated blood that it receives from the left atrium into the aorta. The first branches from the aorta are the coronary arteries. The aortic valve at the entrance to the aorta prevents backflow of blood into the left ventricle. Because contraction of the left ventricle propels blood into the systemic circulation, the wall of the left ventricle is thicker than that of the right ventricle

Answer 157

* trabeculae carneae * papillary muscles; two in the left ventricle * chordae tendineae that connect the tips of the papillary muscles to the mitral valve

Answer 158

When the ventricles contract (ventricular systole), pressure rises inside the ventricles. This rise in pressure has the potential to force blood back into the atria. The tricuspid and mitral valves close during ventricular contraction and prevent regurgitation of blood back into the atria, ensuring that blood can only flow out the ventricles via the great vessels (the pulmonary trunk and aorta).

Answer 159

The papillary muscles and chordae tendineae are crucial for normal functioning of the atrioventricular valves. These structures do not close the valves, but instead allow the closed valves to resist the pressure generated inside the ventricles during contraction and prevent them from being forced open.

Answer 160

As pressure rises in the ventricles, the valve cusps, which project into the ventricle, start to close passively. When the ventricles contract, the papillary muscles also contract. The papillary muscles tense the cords, which in turn ‘pull’ on the valve cusps and prevent them everting into the atria.

Answer 161

The aortic and pulmonary valves are called semilunar valves, as their cusps are semi-circular (half-moon) shaped. They prevent the backflow of blood from the aorta and pulmonary trunk into the left and right ventricles, respectively, that would otherwise occur at the end of ventricular contraction.

Answer 162

Each semilunar valve has three semi-circular cusps. Each cusp is attached to the inner wall of the vessel, with a free edge that projects into the vessel lumen. Each cusp forms a pocket, or sinus, between its free edge and the vessel wall. When blood is forcefully propelled from the ventricles during ventricular systole, the valve cusps are ‘flattened’ onto the vessel wall and blood flows through the valve unimpeded. At the end of ventricular systole, pressure in the ventricles drops. Once pressure in the ventricle is less than that in the vessel (aorta or pulmonary trunk), blood in the vessel starts to flow back towards the heart. As it flows back, blood is immediately ‘caught’ in the valve cusps. The sinuses rapidly fill with blood and the cusps balloon out into the lumen. The free edges of the three valve cusps contact each other in the lumen and close the valve orifice.

Answer 163

We can auscultate the heart by placing a stethoscope over the chest wall. The sounds we hear are the sounds of the heart valves closing. Healthy heart valves have a typical ‘lub-dub’ sound. If the valves are abnormal or dysfunctional, we hear abnormal sounds, called murmurs. As blood flows through each valve, the sound of the valve closing is transmitted in the direction of blood flow. Therefore we listen to the heart sounds in the regions where sound is transmitted, rather than directly over the valve.

Answer 164

* Aortic = 2nd intercostal space, just to the right of the sternum. * Pulmonary = 2nd intercostal space, just to the left of the sternum. * Tricuspid = 5th intercostal space, just to the left of the sternum. * Mitral = 5th intercostal space, left midclavicular line

Answer 165

* Cells in the sinoatrial (SA) node spontaneously generate electrical impulses; it is the ‘pacemaker’ of the heart. It is located at the superior end of the crista terminalis. * The SA node generates impulses at a rate of approximately 70 per minute. * Impulses from the SA node stimulate contraction of the atria.

Answer 166

Impulses are conducted to the atrioventricular (AV) node, located at the inferior end of the interatrial septum.

Answer 167

From the AV node, conducting fibres form the atrioventricular bundle (Bundle of His).

Answer 168

* The atrioventricular bundle divides into two groups of fibres - the right and left bundle branches.

Answer 169

The left and right bundle branches give rise to Purkinje fibres that enter the myocardium of the left and right ventricles, respectively, and stimulate contraction.

Answer 170

* The SA node is supplied by the RCA in approximately 60% of people and by the LCA in approximately 40% of people. * The AV node is usually supplied by the posterior interventricular artery. In most people, the PIV arises from the RCA. * In most people, the LCA supplies the Bundle of His. Occlusion of either coronary artery can therefore result in conduction abnormalities, in addition to myocardial ischaemia.

Answer 171

* Sympathetic stimulation increases the heart rate and force of contraction. * Parasympathetic stimulation slows the heart rate and force of contraction.

Answer 172

Visceral afferent fibres convey sensory information from the heart back to the CNS. Usually, this sensory information doesn’t reach our conscious perception. However, if the myocardium is ischaemic, this visceral sensory information is relayed back to our conscious perception and may be perceived as pain, burning, tightness or pressure in the chest. Typically, the pain cannot be pinpointed, but is felt generally in the chest, the left side of the neck and / or the left arm. This is called referred pain.

Answer 173

This is the death of a region of myocardium secondary to occlusion (blockage) of the coronary vessel that supplies it. Most commonly, it is caused by atherosclerosis within the coronary arteries. A fatty plaque in a coronary artery may grow until it narrows the vessel lumen (stenosis) and severely restricts blood flowing through it. A fatty plaque may shear from the vessel wall, causing a clot to form in the lumen, which occludes blood flow.

Answer 174

Patient foramen ovale (PFO) arises when the foramen ovale fails to close after birth. The foramen ovale ‘functionally’ closes shortly after birth and anatomically closes by the time and infant is about one year old. A PFO allows blood to move from the left to the right atrium. Openings can also occur in the interventricular septum.

Answer 175

Ventricular septal defects (VSDs) allow blood to flow from the left to the right ventricle. The severity of these defects largely depends on the size of the opening between the chambers.

Answer 176

The AV and semilunar valves may become narrowed (stenosis) or incompetent. Incompetent valves allow regurgitation of blood back into the preceding chamber. Both result in turbulent blood flow that produce murmurs on auscultation. Some valve problems are clinically insignificant, whilst others are severe. Valve dysfunction may be congenital (i.e. the patient is born with it) or acquired. For example, an AV valve may become dysfunctional if a myocardial infarct involves the associated papillary muscles.

Answer 177

Cardiomyopathies are diseases of myocardium, and most are inherited. There are different types – some cause the myocardium to thin, whereas others result in the myocardium becoming thick and stiff. This affects the heart’s ability to pump efficiently and can lead to heart failure. Unfortunately, some cardiomyopathies have no obvious symptoms and are a cause of sudden cardiac death in otherwise healthy, young people.

Answer 178

There are many different types of conducting system abnormalities with varied causes. Myocardial infarction can cause conduction disturbances if the vessels that supply the conducting system are affected. Sometimes patients may have no symptoms and the abnormality is picked up on ECG. Some conducting system abnormalities are life-threatening, but can be managed if they are detected, for example, by fitting a pacemaker or an internal cardiac defibrillator (ICD).

Answer 179

Heart failure occurs when the heart does not pump efficiently. There are many possible causes, including dysfunction of one or more of the heart valves, or an ability of the myocardium to contract properly (e.g. due to damage by myocardial infarction or cardiomyopathy). Signs and symptoms of heart failure include tiredness, shortness of breath and leg swelling.

Answer 180

Cardiac arrest is the cessation of cardiac contraction. Sometimes there is still detectable electrical activity, but the heart does not contract in response. Myocardial infarction and conducting system abnormalities are two causes of cardiac arrest, but there are many more.

Answer 181

* Posterior intercostal arteries which supply the intercostal spaces * Bronchial arteries which supply the lungs * Oesophageal branches which supply the oesophagus * Pericardial branches which supply the pericardium * Phrenic branches which supply the diaphragm.

Answer 182

The azygos system of veins arises in the abdomen at the level of L1 / L2 and traverses the diaphragm to enter the posterior mediastinum. It drains blood from the posterior thoracic wall and returns it to the superior vena cava. The azygos veins lie on the bodies of the thoracic vertebrae. The azygos system receives blood from the posterior intercostal veins, oesophageal veins, and bronchial veins.

Answer 183

* an azygos vein on the right side of the vertebral bodies * a smaller (shorter) hemiazygos vein on the left side of the vertebral bodies * one or more veins connecting the above veins to each other.

Answer 184

In the posterior mediastinum, the oesophagus lies to the right of the aorta. It is supplied by oesophageal arteries from the descending aorta. Oesophageal veins return venous blood to the azygos system. The smooth muscle in the wall of the oesophagus is under autonomic control. We will look at the innervation of the oesophagus later in this session. The oesophagus passes through the oesophageal hiatus in the diaphragm at the level of T10. The most distal part of the oesophagus lies inferior to the diaphragm.

Answer 185

The thoracic duct returns most of the body’s lymph to the venous system. It lies between the azygos vein and the aorta.

Answer 186

* Lymph from the lower limbs, pelvis and abdomen flows towards the cisterna chyli, a sac-like swelling that gives rise to the thoracic duct, which ascends into the thorax. * In the thorax, the duct receives lymph from the intercostal spaces and lymph nodes. * The duct ascends into the neck, receiving lymph from the left side of the head and neck and the left upper limb. * It terminates by opening into the venous system at the junction between the left internal jugular vein and the left subclavian vein.

Answer 187

The right side of the head and neck and the right upper limb are drained by lymphatic ducts that enter the venous system at the junction of the right internal jugular and right subclavian veins.

Answer 188

The trunks lie on the posterior thoracic wall, either side of the vertebral column and posterior to the parietal pleura. They are thin, longitudinal fibre tracts regularly interspersed with ganglia (singular = ganglion). Remember that a ganglion is a collection of cell bodies outside the CNS. The ganglia in the sympathetic trunks are sometimes referred to as ‘paravertebral ganglia’ as they lie alongside the vertebral column. The trunks extend from the skull base to the coccyx.

Answer 189

The cell bodies of preganglionic sympathetic neurons lie in the thoracic and upper lumbar spinal cord segments (T1 – L2/3). Because sympathetic fibres are visceral motor fibres, they leave the spinal cord from its ventral aspect and enter spinal nerves T1 – L2/3 along with somatic motor nerves, whose cell bodies lie in the ventral grey horn.

Answer 190

* Preganglionic sympathetic fibres exit the spinal cord in spinal nerves T1 - L2/3. * Almost immediately, they separate from the spinal nerves and enter the sympathetic trunk via a short communicating / connecting branch (white ramus communicans). * Once in the sympathetic trunk, the preganglionic axon does one of the following: 1. synapses in the ganglion at its level of entry (see Figure 1) 2. ascends or descends in the trunk before synapsing in a ganglion (see Figure 2) 3. travels through a ganglion (and the trunk) without synapsing (see Figure 3).

Answer 191

* enter spinal nerves via a communicating branch (grey ramus communicans). Through this arrangement, sympathetic fibres enter all 31 pairs of spinal nerves * form visceral nerves that convey sympathetic fibres to the head * form visceral nerves that convey sympathetic fibres to the thoracic viscera (cardiopulmonary splanchnic nerves).

Answer 192

. A preganglionic axon enters the sympathetic trunk and synapses in a ganglion at its level of entry.

Answer 193

A preganglionic axon enters the sympathetic trunk, ascends, and synapses in a ganglion superior to its level of entry.

Answer 194

The sympathetic preganglionic axons travel through the sympathetic trunk without synapsing. These fibres exit the trunk and form the abdominopelvic splanchnic nerves.

Answer 195

* Greater splanchnic nerve (sympathetic preganglionic fibres originating from T5-T9 segments of the spinal cord) * Lesser splanchnic nerve (from T10-11) * Least splanchnic nerve (from T12) * Lumbar splanchnic nerves (from L1–L2)

Answer 196

The greater, lesser, and least splanchnic nerves are formed in the posterior mediastinum and traverse the diaphragm to enter the abdomen. The preganglionic sympathetic fibres in these splanchnic nerves do ultimately synapse with second neurons in prevertebral ganglia that lie close to major blood vessels in the abdomen. After synapsing, the postganglionic fibres innervate abdominal viscera - we will come back to these in the Gastrointestinal Anatomy block.

Answer 197

With the parietal pleura removed from the posterior thoracic wall, we see the posterior intercostal spaces. The posterior intercostal space contains: * intercostal muscles * a posterior intercostal artery (a branch of the thoracic aorta) * a posterior intercostal vein (which drains to the azygos system) * a posterior intercostal nerve

Answer 198

The thoracic viscera are innervated by both sympathetic and parasympathetic fibres that have coordinated, but generally opposing actions. * The cardiopulmonary splanchnic nerves convey postganglionic sympathetic fibres to the thoracic viscera. * The vagus nerves convey parasympathetic fibres to the thoracic viscera.

Answer 199

These sympathetic and parasympathetic fibres form autonomic plexuses around the thoracic viscera. The word plexus comes from the Latin for braid or plait and is not specific to nerves but also describes networks of veins and arteries. The autonomic nerve plexuses look like delicate, fine meshes or webs. In the thorax we find the: * cardiac plexus * pulmonary plexus * oesophageal plexus

Answer 200

The cardiac plexus innervates the sinoatrial node of the heart. Sympathetic fibres increase the heart rate and force of contraction, whilst parasympathetic fibres decrease the heart rate and force of contraction.

Answer 201

The pulmonary plexus innervates the bronchi. Sympathetic stimulation relaxes the bronchi and parasympathetic stimulation constricts them.

Answer 202

The oesophageal plexus overlies the anterior surface of the oesophagus. Sympathetic fibres inhibit peristalsis and parasympathetic fibres stimulate peristalsis.

Answer 203

Visceral afferents relay sensory information from the thoracic viscera back to the CNS along the paths of the vagus and thoracic splanchnic nerves.

Answer 204

Patients with angina or myocardial infarction usually have pain (but beware – not always!) but they do not feel it coming from their heart. Cardiac pain is typically (but not always) felt in the central chest, left side of the neck and left arm. This is an example of referred pain, where pain from one part of the body is felt in another region.

Answer 205

Heart is innervated by sympathetic nerves from T1-T5 which is the same as the chest wall as well as visceral sensory nerves

Answer 206

Another example of referred pain is shoulder pain resulting from pathology of the diaphragm. Cervical spinal cord segments 3-5 contribute spinal nerve fibres to the phrenic nerve. Cord segments C3-5 also contribute to the nerves that innervate the skin of the neck and shoulder. The brain interprets pain coming from the diaphragm as coming from the shoulder region.

Answer 207

Dissection in this context refers to a longitudinal tear in the aortic wall that allows blood to collect between the intima and media. It can happen in the ascending aorta, arch, or descending aorta. It typically presents with sudden onset severe chest and / or back pain. Instead of flowing through the ‘true’ lumen of the aorta, blood collects in the ‘false’ lumen created by the tear.

Answer 208

Horner’s syndrome describes the presentation of three signs together: a small pupil (miosis), a drooping upper eyelid (ptosis) and lack of sweating (anhidrosis) on one side of the face. It is caused by an interruption to the sympathetic nerves that innervate the head. A cancer in the apex of the lung that invades the sympathetic chain can cause Horner’s syndrome on the ipsilateral side of the head.

Answer 209

A hiatus hernia occurs when the abdominal segment of the oesophagus (inferior to the diaphragm) and part of the stomach moves proximally through the oesophageal opening in the diaphragm and into the chest. Patients may experience symptoms such as heartburn and acid reflux.

Answer 210

The seven cervical vertebrae are small and articulate with each other at facet joints that are orientated obliquely. This allows for a good range of flexion and extension of the cervical spine, in comparison to the thoracic spine

Answer 211

The hyoid bone is a slender bone situated anteriorly in the upper neck, inferior to the mandible. It helps to keep the pharynx open and provides an attachment point for several muscles in the neck and of the tongue.

Answer 212

The larynx (‘voice box’) is composed of a ‘skeleton’ of small cartilages connected by membranes and small joints. It protects the airway. Muscles attach to the laryngeal cartilages and move them, in turn moving the vocal cords and allowing phonation. We will look at the larynx, its blood supply and innervation in the next session.

Answer 213

The neck is described in terms of the anterior and posterior triangles which are separated from each other by the sternocleidomastoid muscle. Sternocleidomastoid (SCM) is attached to the sternum, clavicle, and the mastoid process (part of the temporal bone). It can act unilaterally or bilaterally (i.e. both the left and right muscles act together). It is innervated by the accessory nerve (cranial nerve XI).

Answer 214

The boundaries of the anterior triangle are: * anteriorly: the midline of neck * posteriorly: the anterior border of sternocleidomastoid * superiorly: the lower border of the mandible

Answer 215

* the trachea and larynx * the thyroid gland, parathyroid glands, and the submandibular salivary gland * the suprahyoid muscles which connect the hyoid to the skull. They form the floor of the mouth and move the hyoid and larynx in speech and swallowing. * the infrahyoid muscles. Also called the ‘strap’ muscles, they connect the hyoid to the sternum and scapula. They move the hyoid and larynx in speech and swallowing. * the common carotid artery and its terminal branches (the external and internal carotid arteries) * branches of the external carotid artery to the head and neck * the internal jugular vein * branches of the facial nerve (CN VII), the glossopharyngeal nerve (CN IX), the vagus nerve (CN X), the accessory nerve (CN XI) and the hypoglossal nerve (CN XII). * the ansa cervicalis (fibres from C1-C3 which innervate the infrahyoid muscles).

Answer 216

* anteriorly: the posterior border of sternocleidomastoid * posteriorly: the anterior border of trapezius * inferiorly: the clavicle.

Answer 217

* muscles that move the head. We will not study these. * part of the subclavian artery and the subclavian vein * the external jugular vein which drains the scalp and face * the accessory nerve (CN XI) * the roots of the brachial plexus (spinal nerves that supply the upper limb) * the cervical plexus (fibres from C1-4) * the phrenic nerve.

Answer 218

These four paired muscles (mylohyoid, geniohyoid, stylohyoid and digastric) lie superior to the hyoid bone and form the floor of the mouth. When they contract, they raise the hyoid bone and larynx during speech and swallowing

Answer 219

These four paired ‘strap’ muscles lie inferior to the hyoid bone just lateral to the anterior midline of the neck. They draw the hyoid bone and larynx inferiorly during speech and swallowing.

Answer 220

* Sternohyoid and omohyoid lie superficially; they attach the hyoid to the sternum and scapula, respectively. * Sternothyroid and thyrohyoid lie deep; they attach the sternum to the thyroid cartilage and the thyroid cartilage to the hyoid, respectively.

Answer 221

The thyroid gland is composed of right and left lobes that lie just lateral to the lower larynx and upper trachea. Each lobe lies deep to the sternothyroid muscle. The two lobes are joined by the isthmus, which lies anterior to the trachea. The thyroid gland produces hormones which play an important role in the regulation of metabolic processes. The pituitary gland regulates hormone secretion from the thyroid gland.

Answer 222

The thyroid gland has a rich blood supply via the: * left and right superior thyroid arteries - branches of the external carotid arteries. * left and right inferior thyroid arteries - branches of the thyrocervical trunks (which in turn are branches of the subclavian artery). Some people have an additional thyroid ima artery. Superior, middle, and inferior thyroid veins drain the thyroid gland.

Answer 223

There are usually four parathyroid glands - right and left superior and inferior glands - located posterior to the thyroid gland. They produce parathyroid hormone which plays a role in calcium regulation. They are typically supplied by the inferior thyroid arteries.

Answer 224

The common carotid arteries ascend in the right and left sides of the neck, respectively. The pulsation of the internal carotid can be palpated immediately lateral to the larynx. The common carotid arteries bifurcate into external and internal carotid arteries.

Answer 225

The internal carotid artery does not give rise to any branches in the neck. It enters the cranium and supplies the brain.

Answer 226

The external carotid artery gives rise to several branches that supply the head and neck, including the pharynx, scalp, thyroid gland, tongue, and the face.

Answer 227

* At the point of bifurcation of the common carotid artery there is a small swelling - the carotid sinus. Baroreceptors here constantly monitor arterial blood pressure. This visceral sensory information is relayed back to the CNS via the glossopharyngeal nerve and results in reflex responses that regulate the blood pressure.

Answer 228

The subclavian artery gives rise to several vessels. A large branch, the thyrocervical trunk, gives rise to the inferior thyroid artery. The subclavian artery supplies the upper limb.

Answer 229

The internal jugular vein is a major vein in the neck, which drains blood from the brain and part of the face. * It unites with the subclavian vein, which returns blood from the upper limb, to form the brachiocephalic vein. * The right and left brachiocephalic veins unite to form the superior vena cava. The external jugular vein drains blood from the scalp and face. It joins the subclavian vein.

Answer 230

Number 7 supplies platysma in the neck.

Answer 231

Number 9 glossopharyngeal nerve (CN IX) supplies the: * pharynx (sensory innervation) * carotid sinus (visceral sensory fibres that return to the CNS via CN IX)

Answer 232

Number 10 vagus nerve (CN X) is vital for normal speech and swallowing. It supplies: * the muscles of the pharynx (motor innervation) * the larynx (motor and sensory innervation) In the neck, the vagus nerve runs between the internal jugular vein and the internal carotid artery (above its bifurcation) and between the internal jugular vein and common carotid artery (below its bifurcation). The three structures run together in a fascial sleeve called the carotid sheath.

Answer 233

Number 11 The accessory nerve (CN XI) supplies the sternocleidomastoid and trapezius muscles

Answer 234

Number 12 The hypoglossal nerve (CN XII) is motor to the muscles of the tongue. It does not supply any structures in the neck but travels through it. It lies lateral to the internal carotid artery and deep to the external jugular vein.

Answer 235

The phrenic nerve is formed by C3, C4 and C5 nerve fibres. It descends through the neck to enter the thorax. It innervates the diaphragm.

Answer 236

The head and neck are richly innervated with sympathetic nerves. The sympathetic trunk extends as far as the base of the skull. The associated sympathetic ganglia in the neck are the superior, middle, and inferior cervical ganglia. Postganglionic fibres from these ganglia innervate the head and neck.

Answer 237

Removal of the thyroid gland (e.g. for thyroid cancer) risks injury to the recurrent laryngeal nerves, which lie close to the inferior thyroid arteries. The nerve may be cut when the artery is ligated. Injury to the recurrent laryngeal nerve results in an inability to move the ipsilateral vocal cord and this affects the quality of the voice. Another risk of thyroidectomy is that the parathyroid glands may be removed, which disturbs calcium homeostasis. After thyroidectomy, patients must take hormone replacements.

Answer 238

Atheroma (fatty plaque) in a carotid artery narrows the lumen (stenosis) and impedes blood flow to the brain. If a plaque breaks up, fragments of the plaque and thrombus will be carried up into the cerebral arteries, causing a stroke which could be fatal or severely debilitating. To prevent this, atheroma can be surgically removed from the wall of the carotid artery in a procedure called a carotid endarterectomy. The procedure carries a risk of severe bleeding from the carotid artery and stroke.

Answer 239

Because the neck contains vital neurovascular structures located very closely to each other, penetrating injuries such as stab wounds often injure multiple structures. Such injuries are often fatal or cause severely debilitating injuries.

Answer 240

In patients who are very unwell and need fluid and drugs intravenously, a large line with multiple ports can be placed into a large central vein. The IJV is the vein of choice, as it is relatively easy to access and can be easily visualised with ultrasound.

Answer 241

The walls of the pharynx are composed of an outer layer of circular muscle and an inner layer of longitudinal muscle. The external circular muscle layer is composed of three constrictor muscles - the superior, middle, and inferior constrictors - that overlap each other. They contract superior to inferior, so that swallowed food moves down the pharynx towards the oesophagus

Answer 242

During swallowing, food in the oral cavity is pushed into the oropharynx by the tongue. The soft palate rises and closes off the nasopharynx from the oropharynx. Food enters the laryngopharynx and constriction of the muscles of the pharyngeal wall move the food into the oesophagus. The epiglottis - one of the cartilages of the larynx - closes off the laryngeal inlet and prevents food or liquids from entering the larynx.

Answer 243

The pharynx is one continuous passageway composed of three parts: the nasopharynx, the oropharynx, and the laryngopharynx. * The nasopharynx is posterior to the nasal cavity. * The oropharynx is posterior to the oral cavity. * The laryngopharynx is posterior to the larynx (sometimes called the hypopharynx).

Answer 244

The tonsils are collections of lymphoid tissue in the upper parts of the pharynx

Answer 245

The roof of the nasopharynx

Answer 246

The tubal tonsil surrounds the opening of the auditory tube (which connects the nasopharynx to the middle ear)

Answer 247

The palatine tonsil lies next to the pharyngeal wall in the oropharynx

Answer 248

* The lingual tonsil is a collection of lymphoid tissue on the posterior aspect of the tongue.

Answer 249

The pharynx is innervated by sensory fibres from the glossopharyngeal nerve and motor fibres from the vagus nerve. Several nerves lie close to the posterior pharyngeal wall. * The cervical part of the sympathetic trunk and superior cervical ganglion. * Superior laryngeal nerve. This branch of the vagus nerve descends over the posterior aspect of the internal carotid artery. It passes between the inferior and middle constrictors of the pharynx to the larynx. * Hypoglossal nerve. This lies close to the vagus nerve. * Glossopharyngeal nerve. From the posterior aspect, it lies deep to the internal carotid artery.

Answer 250

The gag reflex protects the airway. It is mediated by the glossopharyngeal and vagus nerves. When the back of the mouth, posterior wall of the pharynx or the tonsils are stimulated, this sensation is carried to the CNS via the glossopharyngeal nerve. In response, the muscles of the soft palate and pharynx immediately contract (via motor fibres in the vagus nerve). This reflex does not occur in normal swallowing but does occur at any other time the posterior mouth or pharynx are touched (e.g. swabbing the tonsils).

Answer 251

If a stroke affects the regions of the brain involved in the control of swallowing, then patients may have swallowing difficulties. In normal swallowing, the vagus nerve coordinates contraction of the pharyngeal muscles and soft palate and conveys sensation from the larynx, whilst the glossopharyngeal nerve provides sensory innervation to the pharynx. If these pathways are interrupted, swallowing is dysfunctional, and loss of sensation impairs the cough reflex. Patients are at risk of ‘aspiration’ – swallowed liquid or food may pass into the lungs and cause infection.

Answer 252

The larynx is composed of nine cartilages. Three are unpaired, and three are paired. Membranes and very small joints connect the cartilages to each other. The three unpaired cartilages are the epiglottis, thyroid cartilage, and the cricoid cartilage. The three paired cartilages are much smaller than the unpaired cartilages. They are the arytenoids, the cuneiforms and the corniculate cartilages. The latter two pairs are very small, and we will not consider them further.

Answer 253

The thyroid cartilage is composed of two flat cartilages (laminae) that meet in the anterior midline to form the laryngeal prominence, or ‘Adam’s apple’, which is usually visible in males.

Answer 254

* Posteriorly, the laminae form extensions that project superiorly and inferiorly - the superior and inferior horns. * The superior horns attach to the hyoid bone. * The inferior horns articulate with the cricoid cartilage below.

Answer 255

The cricothyroid membrane connects the inferior border of the thyroid and superior border of the cricoid. This membrane is pierced to create an emergency airway.

Answer 256

The epiglottis is attached to the superior aspect of the thyroid cartilage, where the two thyroid laminae meet. During swallowing, the epiglottis covers the entrance to the larynx (the laryngeal inlet) and protects the airway from the entry of liquid or food.

Answer 257

The arytenoids sit on the superior surface of the cricoid cartilage. They articulate with the cricoid cartilage at small joints. Although small, the arytenoids are vital for phonation, as the vocal cords attach to them. Movements of the arytenoids move the vocal cords.

Answer 258

The epiglottis protects the larynx and airway from the entry of fluid or food. The internal aspect of the larynx is modified for phonation. Intrinsic muscles of the larynx move the laryngeal cartilages which in turn move the vocal cords that lie inside the larynx. Injury to the nerves that innervate the intrinsic laryngeal muscles therefore affect speech.

Answer 259

Within the larynx there are two pairs of folds that project into the cavity. These are the vestibular folds (false vocal cords) superiorly and the vocal folds (true vocal cords) inferiorly. * The vestibular folds are folds of mucous membrane that lie superior to the vocal folds. * A narrow space separates the vestibular and vocal folds. * The vocal folds are folds of mucous membrane that cover and protect the vocal ligaments – together they form the true vocal cords. * The space between the true vocal cords is the rima glottidis.

Answer 260

The vocal ligaments are attached anteriorly to the internal aspect of the laryngeal prominence and posteriorly to the arytenoid cartilages.

Answer 261

* Adduction of the true vocal cords closes the rima glottidis, whilst abduction of the folds opens it. * Phonation requires adduction of the cords and closure of the rima glottidis. * Abduction of the cords opens the rima glottidis: * to a small degree in whispering * partially in normal breathing * fully in forced breathing.

Answer 262

Extrinsic muscles - the suprahyoid and infrahyoid muscles. They do not move the individual cartilages, but rather move the larynx as one with speech and swallowing.

Answer 263

Intrinsic muscles - move the laryngeal cartilages which in turn move the vocal cords. Injury to the nerves that innervate the intrinsic laryngeal muscles therefore affect speech.

Answer 264

Left and right cricothyroid muscles anteriorly (between the thyroid and cricoid cartilages). Contraction of this muscle places tension on the vocal cords.

Answer 265

Left and right posterior cricoarytenoids on the posterior surface of the cricoid. Each is attached to the ipsilateral arytenoid. These muscles abduct the vocal cords and open the rima glottidis.

Answer 266

An unpaired muscle on the posterior aspect of the larynx which connects the two arytenoid cartilages. These muscles adduct the vocal folds and close the rima glottidis

Answer 267

* The superior laryngeal nerve innervates the cricothyroid muscle and is sensory to the larynx above the vocal folds. * The recurrent laryngeal nerve innervates all the intrinsic muscles except for the cricothyroid and is sensory to the larynx below the vocal folds.

Answer 268

* hyoid bone inferior to the mandible * thyroid cartilage in the midline of the neck (the ‘Adam’s apple’) * cricoid cartilage in the midline, inferior to the thyroid cartilage * first tracheal cartilage inferior to the cricoid cartilage * cricothyroid membrane between the thyroid cartilage and cricoid cartilage – this can be punctured to create an emergency airway * lobes of the thyroid gland either side of the upper trachea and inferior larynx * carotid pulse – best palpated just anterior to sternocleidomastoid at the level of the thyroid cartilage.

Answer 269

The recurrent laryngeal nerve lies close to the inferior thyroid artery, which is ligated during thyroidectomy. The nerve innervates all but one of the intrinsic muscles of the larynx. If it is injured, the intrinsic muscles of the ipsilateral side do not function and subsequently the vocal cords on the affected side cannot move. When the vocal cords on one side are unable to adduct, hoarseness of the voice results.

Answer 270

Malignancy of the larynx typically presents with a change in the quality of the voice, such as hoarseness. Visualisation of the larynx - laryngoscopy – is used to examine the larynx and vocal cords.

Answer 271

Endotracheal intubation is the passage of a semi-rigid tube into the trachea for ventilation. It is commonly performed when patients have a general anaesthetic for surgery, or when patients are sedated in intensive care. A laryngoscope is used to lift the tongue and epiglottis so that the vocal cords can be directly seen, and the tube is passed between them into the trachea. Correct placement into the trachea (rather than the oesophagus) is confirmed by a carbon dioxide reading on the anaesthetic machine (expired air from the patient) and auscultating both lungs to ensure the tube is in the trachea and not one of the bronchi.

Answer 272

If the airway is obstructed above the level of the cricoid cartilage (e.g. a foreign body is stuck at the vocal cords, or the vocal cords have become suddenly grossly swollen) an emergency airway that bypasses the upper airway can be created by piercing the cricothyroid membrane. This is a lifesaving but temporary measure, and a more secure airway is established as soon as possible.

Answer 273

● each other by a thin midline septum, formed of cartilage and bone. When the head is bisected, the septum is seen on one half only. ● the oral cavity inferiorly by the hard palate (the floor of the nasal cavity) ● the brain superiorly by bone (the roof of the nasal cavity)

Answer 274

The nasal cavity communicates with the nasopharynx posteriorly. The nasal cavity also communicates with the paranasal sinuses, which are cavities within the skull bones.

Answer 275

The midline nasal septum is formed of cartilage anteriorly and two thin plates of bone posteriorly. The perpendicular plate of the ethmoid bone forms the superior part of the posterior septum, and the vomer forms the inferior part of the posterior septum.

Answer 276

The lateral wall of the nasal cavity bears three projections of bone, the superior, middle, and inferior conchae (Latin = shell), or turbinates. ● The spaces inferior to them are the meatuses: the superior meatus lies inferior to the superior concha; the middle meatus lies inferior to the middle concha and the inferior meatus lies inferior to the inferior concha. ● As inspired air travels through the meatuses it is warmed, humidified, and filtered

Answer 277

The nasal cavity is separated from the cranium and the brain by the cribriform plate. The cribriform plate is a delicate section of bone that is perforated with tiny holes (like a sieve). Mucosa in the upper part of the nasal cavity contains olfactory receptors. The axons of these receptors form olfactory nerves which travel through these perforations to the brain.

Answer 278

The nasal cavity is supplied by several arteries, including branches of the maxillary artery, which is a terminal branch of the external carotid artery. An anastomotic network formed supplies the nasal septum and is often the site of bleeding in a nosebleed (epistaxis). The sensory innervation of the nose is via branches of the trigeminal nerve (CN V).

Answer 279

The paranasal sinuses are cavities within the skull bones and are named according to the bones within which they are located. ● Frontal sinuses lie within the anterior part of the frontal bone. ● Ethmoid air cells lie within the ethmoid bone (superior to the nasal cavity and medial to the orbits). ● Sphenoid sinuses lie within the sphenoid bone. ● Maxillary sinuses lie within the maxillae of the facial skeleton.

Answer 280

The paranasal sinuses communicate with the nasal cavity via small ducts / channels. ● The frontal sinus drains into the middle meatus. ● The sphenoid sinus drains into the spheno-ethmoidal recess. ● The ethmoid air cells drain into the superior and middle meatuses. ● The maxillary sinus drains into the middle meatus – the opening into the middle meatus lies superomedially, therefore it cannot drain feely when the head is upright.

Answer 281

The nasal cavity also receives the nasolacrimal duct which drains the fluid (‘tears’) that lubricate the anterior surface of the eye. The duct opens into the inferior meatus. When we cry, we get a runny nose because excess fluid runs down the nasolacrimal duct.

Answer 282

The nasal cavity also communicates with the middle ear. The middle ear is a small cavity within the temporal bone that is modified for hearing (it contains three tiny bones that transmit sound waves to the inner ear). ● The auditory tube (Eustachian tube) connects the middle ear to the nasopharynx. The opening of the auditory tube can be seen on the lateral wall of the nasopharynx, surrounded by a slight bulge, which is formed of tonsillar tissue. ● The auditory tube allows air to pass into the middle ear so that the pressure on either side of the tympanic membrane (eardrum), which lies between the middle and external ear, is equal. This is important for optimal conduction of soundwaves.

Answer 283

The hard palate is composed of the palatine processes of the maxillae and the horizontal plates of the palatine bones. The hard palate is functionally important because: ● it prevents food or fluid entering the nasal cavity. ● we push our tongue up against the hard palate during the first phase of swallowing, which forces food and fluid backwards into the oropharynx. ● we push our tongue up against the hard palate to articulate certain sounds. In some people the palate does not form properly during embryological development (a cleft palate), causing difficulty with eating, swallowing and speech if not repaired.

Answer 284

The soft palate lies posterior to the hard palate. A midline conical projection - the uvula - ‘hangs’ from the posterior border of the soft palate and can be seen at the back of the mouth. The soft palate is composed of several muscles, but you do not need to learn the names or attachments of the individual muscles. The key point to appreciate is that the muscles of the soft palate contract during swallowing which elevates the soft palate. The nasopharynx is closed off from the oral cavity, preventing reflux of food and fluid into the nasal cavity. The muscles of the soft palate are innervated by the vagus nerve.

Answer 285

Nosebleeds most commonly arise due to trauma, but they also occur spontaneously. They can usually be stopped by applying pressure, but sometimes bleeding can be profuse, especially if patients are taking anticoagulants (‘blood thinners’). If bleeding cannot be stemmed by applying pressure to the nose, the bleeding vessels can be cauterised, or a nasal tampon can be inserted into the nostril which compresses the blood vessels inside the nose.

Answer 286

The nasal bones or septum may be broken by blunt trauma. The nose may be deviated to one side as a result. Traumatic blows to the nose may fracture the cribriform plate and this must be considered in patients with nasal trauma.

Answer 287

This is inflammation or infection of the mucosa lining the paranasal sinuses. It is painful. Sinusitis affecting the maxillary sinuses is problematic as they do not drain freely, unless lying down on one side. Inflammation of the maxillary sinus may cause pain in the cheek, as the sensory nerve that supplies the cheek runs in the roof of the maxillary sinus.

Answer 288

Development of the palate is complex. If the bones of the hard palate do not develop properly or do not fuse in the midline, a cleft remains that allows communication between the nasal and oral cavities. A cleft palate is surgically repaired.

Answer 289

The oral cavity is bounded: ● superiorly by the hard and soft palate (the roof of the mouth) ● inferiorly by soft tissues and muscles (the floor of the mouth) ● laterally by the cheeks (which contain the buccinator muscle). The oral cavity is continuous posteriorly with the oropharynx. It contains the tongue, teeth and gums and the openings of the salivary ducts.

Answer 290

● Adults have 32 teeth – 16 embedded in the maxilla (upper jaw) and 16 embedded in the mandible (lower jaw). ● In the upper and lower jaws there are four incisors, two canines, four premolars and six molars. ● The teeth are composed of: ● an inner pulp which contains blood vessels and nerves ● dentin which surrounds the pulp ● an outer, hard coating of enamel.

Answer 291

Enamel and dentin can be eroded by bacteria or foodstuffs (e.g. sugar and acids). This can lead to decay, inflammation, and infection of the pulp, which is painful. Infection may spread to the bone, leading to abscess formation.

Answer 292

The tongue is essential for chewing, swallowing and speech. It bears papillae on its superior surface, some of which detect taste (‘taste buds’). The anterior part of the tongue lies in the oral cavity, and the posterior part (the root) extends into the oropharynx. The space between the posterior tongue and the anterior aspect of the epiglottis is the vallecula.

Answer 293

The hypoglossal nerve (CN XII)

Answer 294

Intrinsic muscles lie entirely within the tongue. They are paired bilaterally and fuse in the midline. They change the shape of the tongue.

Answer 295

Extrinsic muscles are attached to the tongue but originate from outside it (from the mandible and hyoid bone). They move the tongue.

Answer 296

● Taste in the anterior two thirds of the tongue is served by the facial nerve (CN VII). ● General sensation (touch, pain, temperature) in the anterior two thirds is served by the trigeminal nerve (CN V). ● Taste and general sensation in the posterior third are served by the glossopharyngeal nerve (CN IX).

Answer 297

● The oral cavity is supplied by the lingual, maxillary, and facial arteries, which are branches of the external carotid artery. ● Innervation of the oral cavity is complex. The muscles of the soft palate are innervated by the vagus nerve. The tongue is innervated by four cranial nerves (CNs V, VII, IX and XII) as described above.

Answer 298

tonsil lies in the roof and posterior wall of the nasopharynx (sometimes called the ‘adenoid’).

Answer 299

The tubal tonsil surrounds the opening of the auditory tube on the lateral wall of the nasopharynx.

Answer 300

The palatine tonsil lies on the lateral wall of the oropharynx. Usually referred to as ‘the tonsils’, they are visible on either side of the oropharynx when the mouth is open.

Answer 301

The lingual tonsil is a collection of lymphoid tissue in the posterior tongue.

Answer 302

Three pairs of salivary glands secrete saliva into the oral cavity: the parotid, submandibular and sublingual salivary glands. Glandular secretion is stimulated by parasympathetic fibres. In the practical session we will look for the parotid and submandibular glands.

Answer 303

The parotid gland is the largest of the three paired salivary glands and overlies the posterior part of the mandible. Saliva empties into the mouth via the parotid duct, which opens adjacent to the upper second molar tooth.

Answer 304

The parotid gland is closely related to the facial nerve. After the nerve exits the skull, it enters the deep surface of the parotid gland. Within the gland the facial nerve divides into five branches which emerge to innervate the muscles of facial expression. The parotid gland is also closely related to the external carotid artery. Secretion from the parotid gland is stimulated by parasympathetic fibres in the glossopharyngeal nerve.

Answer 305

The submandibular glands are smaller than the parotid glands. They lie inferior to the body of the mandible, just anterior to the angle. The submandibular duct opens into the floor of the mouth, under the tongue. Secretion of saliva is stimulated by parasympathetic fibres in the facial nerve.

Answer 306

The sublingual glands lie in the floor of the mouth. They open via several small ducts into the floor of the mouth. Secretion is stimulated by parasympathetic fibres in the facial nerve.

Answer 307

Injury to the left or right hypoglossal nerve results in atrophy (wasting) and weakness or paralysis of the ipsilateral tongue muscles. Because the muscles on the unaffected side continue to function, the tongue deviates to the affected (injured) side when the patient protrudes their tongue.

Answer 308

Cancer of the nasal cavity or sinuses is rare. Cancer can develop in structures associated with the mouth, including the oral mucosa, tonsils, tongue, and salivary glands. Mouth cancers may present as ulcers, lumps, or patches of discolouration on the oral mucosa.

Answer 309

Tonsillitis is inflammation of the tonsils - the palatine tonsils are commonly affected. The cause may be a viral or bacterial infection. The tonsils become enlarged, red and may be covered in pus which appears as white spots on the surface of the tonsils. Swallowing is very painful. Inflammation and enlargement of the pharyngeal tonsil (adenoid) is common in children. Enlargement may obstruct the nearby opening of the auditory tube, which can result in fluid accumulation in the middle ear and hearing impairment. Recurrent infection of the tonsils may be managed by tonsillectomy - surgical removal of the tonsils.

Answer 310

Asthma runs in families Children of asthmatic parents are at increased risk of asthma Asthma is not caused by a single mutation in one gene Transmission of the disease through generations does not follow simple Mendelian inheritance typical of classic monogenic diseases New genotyping technologies has made it possible to sequence the human genome for asthma-associated variants

Answer 311

Chronic genetic disease Multi-organ involvement In UK >10,000 people affected Median age of death improving Most common lethal autosomal recessive genetic disorder in Caucasians Static incidence with an increasing prevalence Affects 1 in 2500 live births

Answer 312

Defect in long arm of chromosome 7 coding for the cystic fibrosis transmembrane regulator (CFTR) protein (anion channel) >1600 mutations of CFTR gene identified 90% within a panel of 70 mutations F508del most common mutation causing CF

Answer 313

Transport protein on membrane of epithelial cells Abnormal CFTR protein leads to dysregulated epithelial fluid transport Doesn't move chloride ions causing sticky mucus to build up on the outside of the cell 80% Lung and gastrointestinal involvement 15% Lung alone

Answer 314

Bronchitis Bronchiectasis Fibrosis

Answer 315

Genetic profile and neonatal screening (day 5 IRT) Clinical symptoms – frequent infections, malabsorption, failure to thrive Abnormal salt / chloride exchange – raised skin salt Late diagnoses via infertility services – azoospermia or via gastroenterology team with recurrent pancreatitis / malabsorption 50% diagnosed @ 6 months 90% diagnosed @ 8 years of age

Answer 316

Blockage of exocrine ducts, early activation of pancreatic enzymes, and eventual auto-destruction of the exocrine pancreas Most patients require supplemental pancreatic enzymes

Answer 317

bulky stools can lead to intestinal blockage

Answer 318

Mucus retention, chronic infection, and inflammation that eventually destroy lung tissue There are multiple hypotheses regarding the pathogenesis of lung disease, each of which is supported by data in vitro and in vivo Lung disease is the most common cause of morbidity and mortality

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