(cid:142)(cid:3) Surgeons who become HIV positive for any reason need pro- fessional advice on their limitations and modification of their presence in operative surge ry. Chapter 3 45 f3 Anatomy for surgeons F. Di Franco and G. R. McLatchie The female breast 46 The endocrine system 48 The respirato ry system 52 The abdominal wall 58 The digestive system 64 The appendix 72 The rectum 74 Th e anal canal 76 The liver 78 The gall bladder and bile ducts 82 The pancreas 84 The genitou rinary system 86 CHAPTER 3 Anatomy for surgeons 46 The female breast Breasts are bilateral skin appendages that vary individually in size and shape. Embryology The breast arises from the mammary ridges that derive from the ectoderm. Surface markings The breast is contained within the superficial fascia. It rests on the pec toralis major extending: (cid:142)(cid:3) Superiorly to the 2nd rib. (cid:142)(cid:3) Infer iorly to 6th rib. (cid:142)(cid:3) Medially to the sternum. (cid:142)(cid:3) Laterally to m id axillary line. The axillary tail is an extension of breast tissue into the axilla. Structural features The breast is composed of lobules. Within each lobule, glandular tissue is placed centrally whereas adipose tissue tends to be more laterally. The glands form a d uctal system terminating in 15 \200\22320 lactiferous ducts radiat- ing towards the nipple. Each lobe is separated by fibrous septa, a colla- genous membrane that supports the glandu lar structure. The fibrous septa, along with the ligament of Cooper, form the suspensory me cha- nism of the breast by their attachment to the ribs and the skin. Blood supply Arterial (cid:142)(cid:3) Axillary artery via lateral thoracic and acromiothor acic branches. (cid:142)(cid:3) Internal mammary artery via its perforating branches. Venou s (cid:142)(cid:3) Venous plexus underneath the areola that drains towards the axillary vei n. (cid:142)(cid:3) Veins draining towards the internal mammary vein. Lymphatic drainage (cid:142)(cid:3) The lymphatics of the nipple drain along the surface of the breast underneath the skin. (cid:142)(cid:3) The lymphatics from the medial aspect of the breast drain towards the nodes of the internal mammary territory. (cid:142)(cid:3) Most of the lymphatics of the breast drain toward the axilla. The majority of the lymph nodes are located in the territory of the axillary vein. Nerve supply It arises from the anterior and lateral branches of the 4th, 5th, and 6th thor acic nerves. Practical hint The status of the axillary lymph nodes is crucial in management of breast ca ncer because: (cid:142)(cid:3) It is a prognostic factor. (cid:142)(cid:3) It determines th e need for adjuvant treatment. THE FEMALE BREAST1 47 Fascia superficialis \200\224 superficial layer Retromammary space Pectoralis minor Suspensory ligament Glandular tissue Pectoralis major Lobules of fat Intercostal muscles Fascia superficialis \200\224 deep layer Axillary tail of the breast Nipple UI = Upper internal quadrant UE = Upper external quadrant LI = Lower internal quadrant LE = Lower external quadrant UI UE LI LE Areola Fig. 3.1 The female breast CHAPTER 3 Anatomy for surgeons 48 The endocrine system The thyroid gland This gland is highly vascular, enclosed in a fibrous capsule and bound by a sheath of pretracheal fascia to the larynx so it moves up and down during swallowing. Structure (cid:142)(cid:3) Right and left lobes \200\224pear-shaped, they lie at the sides of the larynx and trachea. (cid:142)(cid:3) An isthmus \200\224connects the right and left lobe at the level of the second, third, and fourth tracheal rings. (cid:142)(cid:3) A pyramidal lobe \200\224often projects upwards from the isthmus. Relation s (cid:142)(cid:3) Superficial: Sternothyroid, sternohyoid, omohyoid and their nerves from the ansa hypoglossi. These are overlapped below by the sterno- mastoid. (cid:142)(cid:3) Medial: Cricoid cartilage, thyroid cartilage, inferior constrictor above and recurrent laryngeal nerve. (cid:142)(cid:3) Posterior: Carotid sheath, inferior thyroid artery, prevertebral muscles. Blood supply (cid:142)(cid:3) Arterial Superior thyroid artery. This is the first branch of the external carotid. It passes to the upper pole under the infrahyoid muscles close to th e ex- ternal branch of the superior laryngeal nerve. Damage to the nerve leads to loss of t imbre of the voice, which becomes monotone. The superior pedicle should therefore be tied c lose to its origin. Inferior thyroid artery. It arises from the thyrocervical trunk, a bran ch of the subclavian artery. It ascends to the carotid sheath and enters the posterior part of the gland. The inferior pedicle should be tied well out to avoid recurrent laryngeal ne rve damage. (cid:142)(cid:3) Venous Superior thyroid vein emerges from the upper pole and d rains into the internal jugular vein. Middle thyroid vein from the lower part of the latera l border of the lobes crosses the common carotid and drains into the internal jugular vein. Inferior thyroid vein from the isthmus or lower medial lobe passes along the front of the trachea to the left innominate vein. Lymphatic drainage To the middle and lower deep jugular, pretracheal, and mediastinal nodes . Recurrent laryngeal nerve Arises from the vagus and runs upwards in the tracheo-oesophageal groove behind or in front of the inferior thyroid arteries. It supplies all the intrinsic muscles of the larynx. Damage or division causes paralysis of the vocal cords on that side. THE ENDOCRINE SYSTEM1 49 (a) Thyrohyoid Hyoid bone Fibromuscuiar cord connecting isthmus of the (levator glandulae thyroidiae) Sternohyoid Thyroid cartilage Omohyoid Sternothyroid Thyroid gland Thyroid cartilage (b) Superior thyroid vein Superior thyroid artery Common carotid artery Internal jugular vein Pyramidal lobe Cricothyroid cartilage+ muscle Middle thyroid vein Thyroid gland Recurrent laryngeal nerve Inferior thyroid vein (c) Superior Thyroid cartilage laryngeal nerve Superior parathyroid Thyroid gland Inferior thyroid artery Inferior parathyroid Ligament of Berry Recurrent laryngeal nerve Fig. 3.2. Structure of the thyroid gland. a) The infrahyoid muscles related to the thyroid. The sternohyoid muscle has been removed on the right-hand side. From Textbook of Anatomy, (ed. A. W. Rogers), 1992. Reproduced with permission from Churchill Livingstone CHAPTER 3 Anatomy for surgeons 50 Parathyroid glands These paired reddish-brown glands, each about the size of a small pea, l ie behind the upper and lower aspects of the thyroid lobes. They are derived from the third (lower gland) and fourth pharyngeal (upper gland) pouches and lie within the pretracheal f ascia often within the thyroid itself. Occasionally there may be more than four. (cid:142)( cid:3) Superior glands. Each is fairly constant in position, lying behind the upper third o f the lobe inside the pretracheal fascia lateral to the trachea. Occasionally each may be m ore anterior and liable to injury during subtotal thyroidectomy. (cid:142)(cid:3) Inferior glands. Their position is more variable. They are usually found b ehind the lower part of each lobe either above or below the inferior thyroid artery as it e nters the substance of the gland. Unusual positions include retro-oesophageal, either in the neck or posterior mediastinum or the anterior mediastinum in relation to the thymus gland. Adrenal glands The right and left adrenal glands are intrabdominal. They lie above or media l to each kidney. Their total weight is 10g. Structure (cid:142)(cid:3) Adrenal cortex (cid:142)(cid:3) Zona glomerulosa, outer layer, produces aldosterone. (cid:142)(cid:3) Zona fasciculata, middle layer, produces cortisol. (cid:142)(cid:3) Zona reticularis, inner lay er, produces sex hormones. (cid:142)(cid:3) Adrenal medulla. (cid:142)(cid:3) Secretes catecholamines \200\224adrenaline and noradrenaline Relations (cid:142)(cid:3) Right adrenal gland (cid:142)(cid:3) Anteriorly \200\224bare area of the liver. (cid:142)(cid:3) Posteriorly \200\224diaphragm. (cid:142)(cid:3) Medially \200\224inferior vena cava. (cid:142)(cid:3) I nferiorly \200\224right kidney. (cid:142)(cid:3) Left adrenal gland (cid:142)(cid:3) Anteriorly \200\224splenic artery, pancreas and peritoneum of lesser sac. (cid:142)(cid:3) Posteriorly \200\224diaphragm (left crus). (cid:142)(cid:3) Laterally \200 \224left kidney. Blood supply (cid:142)(cid:3) Arterial (cid:142)(cid:3) Superior adrenal arteries (from inferior phrenic artery on each side) (cid :142)(cid:3) Middle adrenal arteries (from the aorta) (cid:142)(cid:3) Inferior adrenal art eries (from the renal artery) (cid:142)(cid:3) Venous drainage (cid:142)(cid:3) This is represented by a central vein (cid:142)(cid:3) The right adrenal v ein drains into the inferior vena cava (cid:142)(cid:3) The left adrenal vein drains into t he left renal vein Practical hint The right adrenal vein is very short. This may make surgery of the right adr enal more difficult. This page intentionally left blank CHAPTER 3 Anatomy for surgeons 52 The respiratory system The trachea The trachea is a fibroelastic organ composed by 15 \200 \22320 U-shaped carti- laginous rings. It is approximately 11cm long. The trachea commences at the lower aspect of the cricoid cartilage and terminates at the level of the sternal an gle where it bifurcates into the right and left main bronchi. The point where the trachea b ifurcates is also known as carina. Relations (cid:142)(cid:3) Anteriorly (cid:142)(cid:3) Neck \200\224isthmus of thyroid gland, inferior thyroid veins, sternohyoid , sternothyroid. (cid:142)(cid:3) Thorax \200\224brachiocephalic and left common carotid artery, left brachiocephalic vein. (cid:142)(cid:3) Posteriorly (cid:142)(cid:3) Neck and thorax: esophagus and recurrent laryngeal nerves. (cid:142)(cid:3) Laterally (cid:142)(cid:3) Neck \200\224lobes of thyroid gland, carotid sheath. (cid:142)(cid:3) Thor ax \200\224on the right: vagus nerve, azygos vein and pleura \200\224on the left: aortic ar ch, left common carotid artery, left subclavian artery, left recurrent laryngeal nerve, ple ura. Blood supply It derives from the branches of the inferior thyroid arteries. The bronchi The bronchi arise at the bifurcation of the trachea. The right main bronchus is shorter and more vertical and has a greater diameter than the left one. It is 2.5cm long. Before entering the hilum of the lung, it divides into an upper lobe bronchus. After enteri ng the hilum, it gives off a middle lobe and lower lobe bronchus. The 5cm long left bronchu s divides into the bronchi to the upper and lower lobes just after entering the hilum of th e lung. The bronchial tree reduces in diameter and length with each successive division. The lungs The lungs are paired organs. They are conical in shape. (cid:142)(cid:3) Each lun g presents a: (cid:142)(cid:3) Apex, extending above the first rib (cid:142)(cid:3) Base, related to the diaphragm (cid:142)(cid:3) Parietal surface, related to the rib cage (cid:142)(cid:3) Media stinal surface, related to the pericardium. (cid:142)(cid:3) The right lung has three lobes: (cid:142)(cid:3) Superior (upper) lobe (ci d:142)(cid:3) Middle lobe (cid:142)(cid:3) Inferior lobe. The superior lobe is separated from the middle one by the horizontal fissure. The middle lo be is separated from the inferior one by the oblique fissure. THE RESPIRATORY SYSTEM1 53 Right main bronchus Left main bronchus Right upper lobe bronchus Left upper lobe bronchus Carina Right middle lobe bronchus Left lower lobe bronchus Apical segmental bronchus of lower lobe Right lowr lobe bronchus Fig. 3.3. The trachea and bronchi. From Textbook of Anatomy, (ed. A. W. Rogers), 1992. Repr oduced with permission from Churchill Livingstone Upper Upper Oblique fissure Transverse fissure Oblique fissure Lingula Cardiac notch Middle Lower Lower Base Base Fig. 3.4. The lungs and their lobes. From Applied Basic Science for Basic Surgical Training , (ed. A. T. Raftery), 2000. Reproduced with permission from Churchill Livingstone CHAPTER 3 Anatomy for surgeons 54 The left lung has two lobes (cid:142)(cid:3) Superior lobe (cid:142)(cid:3) Inferior lobe. The oblique fissure separates them. The deficiency of the superior lobe of the left lung is called cardiac notch. The lingula is the part of the left lung between the oblique fissure and the cardiac notch. It is the equiva- lent of the middle lobe of the right lung. Bronchopulmonary segments The lobar bronchi divide further to form the bronchopulmonary seg ments. There are ten segments per lung. A bronchopulmonary segment is composed of : (cid:14 2)(cid:3) A tertiary bronchus (cid:142)(cid:3) The portion of lung it ventilates (cid:142)( cid:3) An artery (cid:142)(cid:3) A vein There is no communication between segments. The br onchopulmonary segments represent the \200\230surgical units of the lung \200\231. Their i dentification allows excising one segment without interfering with the adjacent ones. Blood supply The pulmonary trunk, which arises from the right ventricle, divides into the r ight and left pulmonary arteries. The pleura The lungs are invaginated by a serous membrane called pleura. (cid:142)(cid:3) V isceral pleura: this is the part of the membrane that lines the lungs. (cid:142)(cid:3) Par ietal pleura: membrane that lines the mediastinum, diaphragm and inner aspect of the chest wall. The parietal pleural may be divided into: (cid:142)(cid:3) Cervical pleura, apex extending 2.5cm above the clavicle (cid:142)(cid:3) Costal pleura (cid:142)(cid:3) Mediastinal pleura (cid:142)(cid:3) Diaphragmatic pleura, descending below the medial aspect of the 12th rib. The potential space between the parietal and visceral pleura is called the pleural cavity. The projection of the heart on the left side makes the left pleural cavity smaller than th e right one. Nerve supply (cid:142)(cid:3) Visceral pleura: autonomic innervation from branches of the v agus nerve. (cid:142)(cid:3) Parietal pleura: somatic innervation from the intercostal nerves. (cid:142 )(cid:3) Diaphragmatic pleura: phrenic nerve. Practical hint (cid:142)(cid:3) The pleural c avity becomes a real space when the lung collapses. In this case the pleural cavity may contain air (pneumothorax) or blood (haemothorax). (cid:142)(cid:3) Central venous catheterisation (internal jugular vein/subclavian vein) or a stab wound above the level of the clavicle may damage the pleura (i.e. pneumothorax). THE RESPIRATORY SYSTEM1 55 (cid:142)(cid:3) The parietal pleural is sensitive to pain. Therefore the intercostal nerves may refer the pain to the abdomen, which explains abdominal pain as a possible sympt om of pleuritic and chest wall disease. The thoracic cage The thoracic cage is composed of the following structures: (cid:142)(cid: 3) Anteriorly: sternum and costal cartilages (cid:142)(cid:3) Laterally: 12 pairs of ribs a nd intercostal spaces (cid:142)(cid:3) Posteriorly: 12 thoracic vertebrae. The sternum This is formed by: (cid:142)(cid:3) Manubrium: it articulates with the clavicle , 1st cartilage and the upper part of the 2nd cartilage. (cid:142)(cid:3) Body: its lateral margins articulate with the rest of the 2nd rib and with the 3rd to 7th costal cartilage. (cid:142)(cid:3) Xiphoid process. The ribs The ribs 3 to 10 are \200\230typical ribs \200\231. They are composed of: (cid:14 2)(cid:3) Head: it is wedge-shaped with two articular facets to the correspond- ing vertebra and the vertebra above. (cid:142)(cid:3) Neck. (cid:142)(cid:3) Tubercle: with an articular part (to the transverse process of the corresponding vertebra) and non-articular part. (cid:142)(cid:3) Shaft: rounded; its anterior part is flattened. (cid:142)(cid:3) Costal gr oove: it is located on the lower surface of the shaft. The intercostal artery, vein and ner ve are contained in the groove. The 1st, 2nd, 11th, and 12th ribs are regarded as atypical. (cid:142)(cid:3) The 1st rib is the shortest and broadest with a single facet on the head. (cid:142)(cid:3) The 2nd rib ha s an irregular rough tuberosity for the serratus anterior muscle. (cid:142)(cid:3) The 11th and 12th ribs are known as \200\230floating ribs \200\231 becaus e their carti- lages do not articulate anteriorly. The ribs articulate as follows: (cid:142)(cid:3) Posteriorly: each rib articulates with the thoracic spine. (cid:142)(cid:3) Anteriorly: the superior seven costal cartilages articula te with the sternum; the cartilages from 8th to 10th articulate with cartilage above. The intercostal space An intercostal space is composed of three muscles: (cid:142)(cid:3) E xternal intercostal (cid:142)(cid:3) Internal intercostal (cid:142)(cid:3) Innermost interc ostals. A neurovascular bundle contained in the lower surface of the corre- sponding rib, r uns between the internal intercostal and innermost inter- costal muscles. It includes from above downwards: (cid:142)(cid:3) Vein (cid:142)(cid:3) Artery (cid:142)(cid:3) Nerve. CHAPTER 3 Anatomy for surgeons 56 Practical hints Counting ribs may be necessary to identify which rib is injured or if the r ibs are used as landmark for procedures such as chest drain insertion. The junction between the manubrium and the body of the sternum is felt like a transverse ridge on palpation. Th is is known as angle of Louis (ster- nal angle) and is opposite to the 2nd rib. Ribs are co unted from this point. THE RESPIRATORY SYSTEM1 57 Vein Artery Nerve External intercostal Innermost intercostal Internal intercostal Fig. 3.5 An Intercostal space. A needle passed into the chest immediately above a rib will avoid the neurovascular bundle. From Applied Basic Science for Basic Surgical Train- ing, ( ed. A. T. Raftery), 2000. Reproduced with permission from Churchill Livingstone CHAPTER 3 Anatomy for surgeons 58 The abdominal wall The anterior abdominal wall Fasciae (cid:142)(cid:3) Superficial: in the lower abdomen this is composed of a superficial fatty layer (Camper s fascia) and a deep f ibrous layer (Scarpa \200\231s fascia). The latter is attached to the deep fascia of the le g 2.5cm below the inguinal ligament. It also continues into the perineum (Colles fascia) a nd extends onto the penis and scrotum. (cid:142)(cid:3) Deep: a layer of areolar tissue over the muscles. Muscles Rectus abdominis and rectus sheath. These run longitudinally on each side of the midline. Origin: 5th, 6th, 7th costal cartilage. Insertion: pubic crest. There are also three tendinous insertions wh ich attach the anterior rectus sheath to the xiphisternum, umbilicus, and halfway between. The rectus sheath is mainly composed of the aponeurosis of the lateral abdominal muscles. T he composition of the rectus sheath varies at three levels as follow: 1) Above the level of the costal margin, the anterior rectus sheath is composed of the aponeurosis of the external oblique only. 2) From the costal margin to a point half way between the umbilicus, the external oblique a poneurosis and the anterior leaf of the internal oblique aponeurosis form the anterior rect us sheath. The posterior leaf of the internal oblique aponeurosis and the internal oblique aponeurosis composes the posterior rectus sheath. 3) Below a point halfway between the umbilicus and pubic symphysis, all the aponeuroses pas s anteriorly forming the anterior rectus sheath. The arcuate line of Douglas marks the infe rior border of the posterior rectus sheath. Below this line there is transversalis fascia a nd peritoneum only. (cid:142)(cid:3) External oblique Origin: lower eight ribs. Insertion: linea alba, which re sults from the fusion of the rectus sheaths in the midline. (cid:142)(cid:3) Internal obliq ue Origin: lumbar fascia, anterior two thirds of the iliac crest, lateral two thirds of the inguinal ligament. Insertion: lower six costal cartilages, linea alba, pubic crest. (cid:1 42)(cid:3) Transversus abdominis Origin: lower six costal cartilages, lumbar fascia, anteri or two thirds of the iliac crest, lateral third of the inguinal ligament. Insertion: linea alba and pubic crest. Abdominal incisions: anatomy The structures encountered vary depending on the incision used . (cid:142)(cid:3) Midline Structures encountered: skin, subcutaneous fat, linea alba, extr aperito- neal fat, peritoneum. THE ABDOMINAL WALL1 59 Fig. 3.6 The formation of the rectus sheath. a) above the costal margin; b) above the arcua te line; c) below the arcuate line. From Applied Basic Science for Basic Surgical Training, (ed. A. T. Raftery), 2000. Reproduced with permission from Churchill Livingstone Internal oblique Rectus abdominis External oblique Fig. 3.7 Abdominal wall shows tendindus intersection attachments to anal rectus sheath. CHAPTER 3 Anatomy for surgeons 60 (cid:142)(cid:3) Subcostal (Kocher \200\231s incision) Structures encountered: skin, subcut aneous fat, anterior rectus sheath, rectus muscle, posterior rectus sheath, extraperitoneal fat, and peritoneum. (cid:142)(cid:3) Grid iron Structures encountered: skin, subcutaneous fat, Scarpa \200\231s fascia external oblique aponeurosis, internal oblique muscle, transv ersus abdominis muscle, extraperitoneal fat, peritoneum. (cid:142)(cid:3) Paramedian Struct ures encountered: skin, subcutaneous fat, anterior rectus sheath, rectus muscle, posterior rectus sheath. The posterior rectus sheath is a thick structure in its upper part. Below th e arcuate line of Douglas it is a thin structure, being composed of the transversalis fasci a only. The inguinal canal This is a passage about 4cm long in the anterior abdominal wall through which the spermatic cord or round ligament pass. It lies above the medial half of the ingui nal ligament and runs downwards, medially and forwards. It is a potential weak spot for the development of inguinal hernia. It is a series of three openings in the muscles of the anterior abdominal wall which are staggered so that no opening overlies another: (cid:142)(cid:3) Deep inguina l ring (the deepest opening): an aperture in the fascia trans- versalis. Its surface positi on is about 1.5cm above the mid inguinal point. (cid:142)(cid:3) Opening in the combined te ndons of transversus and internal oblique muscles (conjoint tendon): the spermatic cord or round ligament trav- erses this opening. (cid:142)(cid:3) Superficial inguinal ring: opening in the external oblique aponeurosis. De ep inguinal ring An indirect hernia enters the canal through this ring. It lies lateral to the inferior epigastric vessels. It transmits the round ligament of the uterus, its vessels , and nerve in females. In males the remainder of the processus vaginalis is vestigial supe riorly, the cremasteric vessels are medial, and the genital branch of the genitofemoral ner ve lies inferiorly. It transmits the spermatic cord and its contents. Superficial inguinal ring Is a triangular opening in the external oblique aponeurosis. Its medial and lateral sides are crura, the lateral of which is attached to the pubic tuber- cl e. The medial crus is attached to the pubic symphysis. Therefore when an indirect inguinal hernia emerges from the superficial ring it is above and medial to the pubic tubercle. Walls of the inguinal canal (cid:142)(cid:3) Anterior: aponeurosis of external oblique musc le (cid:142)(cid:3) Posterior: fascia transversalis and conjoint tendon (cid:142)(cid:3) Su perior: lower edge of internal oblique (cid:142)(cid:3) Inferior: inguinal ligament. THE ABDOMINAL WALL1 61 Fig. 3.8 Schematic diagram of the inguinal canal, and the coverings of the testis and sperm atic cord. From Textbook of anatomy, (ed. A. W. Rogers), 1992. Repro- duced with permission from Churchill Livingstone CHAPTER 3 Anatomy for surgeons 62 The femoral canal A femoral hernia passes through the femoral canal to reach the upper aspe ct of the thigh below the inguinal ligament. Features The femoral artery, vein, and canal a re all enclosed in the femoral sheath which is a continuation of the transversalis fascia a bove the inguinal liga- ment and that covering iliacus and psoas muscles below. The canal l ies on pectineus muscle between the femoral vein and the lacunar ligament. It provides spac e for the femoral vein to expand when venous return from the leg is increased. It is funnel -shaped, about 2cm long and with an upper opening, the femoral ring, which is 1.5 \200\2232 cm wide and opens into the abdomen. The femoral ring The ring contains: (cid:142)(cid:3) Fat \200\224the femoral septum (cid:14 2)(cid:3) A single lymph node (Cloquet \200\231s). Boundaries (cid:142)(cid:3) Anterior: in guinal ligament (cid:142)(cid:3) Posterior: pectineal line, pectineus, and its fascia (cid: 142)(cid:3) Medial: lacunar ligament (cid:142)(cid:3) Lateral: femoral vein The femoral can al opens below and lateral to the pubic tubercle. The site of appearance of a femoral herni a. A femoral hernia descends through the canal and usually hooks round the anterior margin of the femoral ring to come to lie over the inguinal ligament. Its coverings include fat (the femoral septum), lymph glands, the anterior wall of the femoral canal, cribriform fascia, s uperficial fascia, subcutaneous fat, and skin. THE ABDOMINAL WALL1 63 Femoral ring Lymph node Lacunar ligament Inguinal ligament Femoral artery and vein lliacus Covered with fascia lata Psoas Pectineus Fig. 3.9 The femoral canal CHAPTER 3 Anatomy for surgeons 64 The digestive system The esophagus The esophagus is a hollow viscus about 25cm long, which extends from the cricopharyngeal sphincter at the level of the 6th cervical vertebra to the cardia of the stomach. It comprises: (cid:142)(cid:3) Cervical esophagus: extending betwee n the level of the lower border of the cricoid cartilage and the jugular notch. (cid:142)(cid:3) Upper esophagus: extends from the level of the jugular notch to the level of the tracheal bifurcation. (cid:142)(cid:3) Middle esophagus: extends from the carina to the midpoint between the carina and the oesophago-gastric junction. (cid:142)(cid:3) Lower esophagus: this includes the lower thoracic esophagus and the hiatal segment of the esophagus (or abdominal esophagus). It passes through the lower part of the neck, superior, and posterior mediastinum and pierc es the diaphragm at the level of the 10th thoracic vertebra. The lowermost part lies below the level of the diaphragm. Layers (cid:142)(cid:3) Stratified squamous epithelium. A gastric-type mucosa may be presen t in the lower esophagus. (cid:142)(cid:3) Submucosa. (cid:142)(cid:3) Musculature: striated in the upper one third. Smooth muscle in lower two thirds. There is an external longitudinal layer and an internal circular layer. (cid:142)(cid:3) There is no serosa. Relations In the neck (cid:142)(cid:3) Trachea anterio rly, cervical vertebrae posteriorly (cid:142)(cid:3) Carotid artery and thyroid on the righ t and left (cid:142)(cid:3) Subclavian artery and thoracic duct on the left at the root of the neck. In the thorax (cid:142)(cid:3) Trachea, left bronchus, left atrium in front (cid: 142)(cid:3) Right and left pleura and lung (cid:142)(cid:3) Aorta mainly behind but on the left at first (cid:142)(cid:3) Vagus nerves. Blood supply (cid:142)(cid:3) Arterial: this i s through the inferior thyroid artery, the descending thoracic aorta and the left gastric artery. (cid:142)(cid:3) Venous drainage: this is through the inferior thyroid veins, the azygos vein and the left gastric vein. Nerve supply (cid:142)(cid:3) Extrinsic and intrinsic nerve plexuses from the vagus nerve ( parasym- pathetic). The vagus nerve is in close relationship with the esophagus throughout its lengt h. (cid:142)(cid:3) Sympathetic supply is from the sympathetic trunks. THE DIGESTIVE SYSTEM1 65 Fig. 3.10 The esophagus: anterior view. From Textbook of anatomy, (ed. A. W. Rogers), 1992. Reproduced with permission from Churchill Livingstone CHAPTER 3 Anatomy for surgeons 66 Sites of anatomical narrowing There are three sites of constriction. Measuring from the inc isor teeth they are at: (cid:142)(cid:3) 15cm: cricopharyngeal sphincter (cid:142)(cid:3) 2 5cm: aortic arch and bifurcation of the bronchi (cid:142)(cid:3) 40cm: diaphragmatic hiatus . Foreign bodies may become arrested at these levels. They are also the sites at which stri ctures (benign or malignant) are most common. Barrett \200\231s esophagus Refers to the replacement of the squamous epithelium by a colum nar- lined mucosa in the lower esophagus. This is usually secondary to gastro- oesophageal reflux. Its importance lies in the fact that it is associated with an increased risk of oes ophageal adenocarcinoma (up to 30 \200\22340 times that of the general population). The stomach The stomach extends from the esophagus to the duodenum. It lies in the upper le ft quadrant of the abdomen behind the lower ribs and ante- rior abdominal wall and is separ ated from the left lung and pleura by the dome of the diaphragm. It is described as pirifor m organ which includes: (cid:142)(cid:3) An anterior surface. (cid:142)(cid:3) A posterior surface. (cid:142)(cid:3) A greater curvature, which is convex. (cid:142)(cid:3) A lesser c urvature, which is concave. The esophagus enters the stomach on its right side about 2.5cm below its uppermost part. The stomach comprises: (cid:142)(cid:3) A cardiac orifice at the level of oesophageal opening. (cid:142)(cid:3) A fundus proximal to oesophageal orifice. (c id:142)(cid:3) A body from fundus to pyloric antrum. (cid:142)(cid:3) A pyloric antrum is t he dilated part after the incisura angularis. (cid:142)(cid:3) A pyloric canal is 2.5cm lon g. It passes from the antrum to the pyloric sphincter. (cid:142)(cid:3) The pylorus, which is continuous with the first part of the duodenum and has thickened muscle \200\224the pyloric sphincter. Peritoneal folds The stomach is covered by peritoneum on each surface. These meet at the cu rvatures to form the lesser omentum above and the greater omen- tum below. The greater omen tum forms three ligaments: (cid:142)(cid:3) The gastrophrenic from the fundus to the diaphr agm (cid:142)(cid:3) The gastrosplenic to the spleen (cid:142)(cid:3) The gastrocolic to th e transverse colon. THE DIGESTIVE SYSTEM1 67 Fig. 3.11. The arterial supply of the stomach: anterior view. From Textbook of anatomy, (ed . A. W. Rogers), 1992. Reproduced with permission from Churchill Livingstone CHAPTER 3 Anatomy for surgeons 68 Relations (cid:142)(cid:3) Anterior: liver to the right, diaphragm to the left, anterior- a bdominal wall. (cid:142)(cid:3) Posterior: body of pancreas, part of left kidney, and left suprarenal, splenic artery and spleen. These form the \200\230bed \200\231 of the stomach. The transverse mesocolon passes from the lower border of the pancreas to the transverse co lon. Blood supply Arterial (cid:142)(cid:3) Left gastric from coeliac axis (cid:142)(cid:3) Righ t gastric from hepatic artery (cid:142)(cid:3) Gastroduodenal from hepatic artery (cid:142) (cid:3) Left gastroepiploic from splenic artery (cid:142)(cid:3) Short gastrics (several) f rom splenic artery (cid:142)(cid:3) Right gastroepiploic from the gastroduodenal artery. Ve nous drainage The blood drained from the stomach passes to the portal system. (cid:142)(cid :3) Right gastric vein, directly to portal vein (cid:142)(cid:3) Left gastric vein, directl y to portal vein (cid:142)(cid:3) Right gastro-epiploic vein, to portal vein via superior m esenteric vein (cid:142)(cid:3) Left gastro-epiploic vein, to portal vein via the splenic v ein (cid:142)(cid:3) Short gastric veins, to portal vein via the splenic vein. Nerve supply The fundus and body of the stomach receive their nerve supply from the proximal vagus. The antrum is innervated by the anterior and posterior nerves of Latarjet also from the vagus. Lymph drainage It is to the following lymph node stations: (cid:142)(cid:3) Cardiac (right and left) (cid:142)(cid:3) Greater and lesser curvature (cid:142)(cid:3) Suprapyloric and i nfrapyloric (cid:142)(cid:3) Left gastric artery, common hepatic artery, coeliac artery, sp lenic artery, middle colic artery (cid:142)(cid:3) Hilum of the spleen, posterior of the pancreas, root of the mesentery (cid :142)(cid:3) Para-aortic. The small intestine This comprises: (cid:142)(cid:3) Duodenum (cid:142)(cid:3) Jejunum (cid :142)(cid:3) Ileum. The duodenum is retroperitoneal and joins the jejunum at the duodeno- j ejunal flexure. The jejunum and ileum are both suspended from the posterior ab- dominal wall by a double fo ld of peritoneum containing the blood supply and venous drainage \200\224the mesentery. Its attachment is about 15cm long and it lies obliquely from the duodenojejunal flexure to the ileocaecal junction. The 20+feet (about 7m) of the small bowel attached to such a small ba se are therefore convoluted. THE DIGESTIVE SYSTEM1 69 As jejunum runs into ileum the features change. Although both have large surface areas inte rnally to aid absorption, the circular folds of mucous membrane decrease in number and size in the ileum and are almost completely absent in the lower ileum so the wall feels thinner . Throughout the small intestine aggregations of lymph follicles are present. These are mor e marked in the ileum and are called Peyer \200\231s patches. They occur on the anti-mesent eric border. Another difference is that mesen- teric fat is less abundant near the intestin al wall in the jejunum so that the vessels to the gut can be seen with mesenteric transpare nt windows between them. Blood supply (cid:142)(cid:3) Arterial: the superior mesenteric artery crosses the third pa rt of the duodenum to enter the root of the mesentery and pass downward towards the right i liac fossa. It gives off several jejunal and ileal arteries, which divide and reunite to su pply the small bowel. In doing so, they form a series of arterial arches and arcades. so on e or more of the main trunks may be ligated without affecting the blood supply. (cid:142)(cid:3) Venous: the veins drain the gut along the arterial pathways and empty into the superior mesenteric vein which joins the portal vein on its way to the liver. Practical hints (cid:142)(cid:3) The duodenojejunal flexure is a site which must always be carefully examined in patients with deceleration injuries because disruption can occur. (cid:142)(cid:3) The fact that the blood supply of the small bowel is organized in arches a nd arcade allows to ligate one of the main trunks without affecting the blood supply. This is done when constructing an ileal pouch for anas- tomosis to the rectum in patients with i nflammatory bowel disease and familial adenomatous polyposis (see Restorative proctocolecto my). The large bowel This is approximately 1.5m long. It comprises of: (cid:142)(cid:3) Appendix (cid:142)(cid:3) Caecum (cid:142)(cid:3) Ascending colon (cid:142)(cid:3) Hepatic flexure (cid:142)(cid:3) Transverse colon (cid:142)(cid:3) Splenic flexure (cid:142)(cid:3) Descend ing colon (cid:142)(cid:3) Sigmoid colon (cid:142)(cid:3) Rectum (cid:142)(cid:3) Anus. The lumen is wide in the caecum and ascending colon but gradually narrows towards the sigmoid colon. Structure It has a peritoneal coat complete over the caecum, appendix, transverse colon and sigmoid colon but incomplete elsewhere. There are small CHAPTER 3 Anatomy for surgeons 70 pouches of peritoneum filled with fat over all of the colon \200\224appendices epiploicae. The outer muscular coat is disposed in three longitudinal bands \200\224the taenia coli. Th ese converge upon the root of the appendix proximally. At the other end they become continu ous with the longitudinal layer of the rectum. They are shorter than the colon so its wall becomes puckered into sacculations \200\224colonic haustrations. Caecum The ileum terminates in a slit-like opening \200\224the ileocaecal valve. The blind- ending portion below this level is the caecum. It may lie free or be attached to the right iliac fossa by peritoneal folds. Relations (cid:142)(cid:3) Inferior: lateral half of ingui nal ligament (cid:142)(cid:3) Anterior: greater omentum, coils of ileum, anterior abdominal wall (cid:142)(cid:3) Posterior: iliacus and psoas. Colon The ascending and descending com ponents are partly retro-peritoneal. The transverse and sigmoid colon are suspended on mese nteries. Transverse colon The middle portion lies below the umbilicus. Superiorly lies the greater c urvature of the stomach, liver, and gall bladder. Posteriorly from right to left are the se cond part of the duodenum, the pancreas, loops of small bowel and the spleen. Anteriorly is the greater omentum. Descending colon This begins at the splenic flexure and ends at the beginning of the sigmoi d colon. Relations (cid:142)(cid:3) Anterior: jejunum, lower part of anterior abdominal wai l (cid:142)(cid:3) Posterior: left kidney, psoas, quadratus lumborum, iliacus Sigmoid colon This begins at the pelvic brim and ends at the level of the 3rd sacral ver- tebra. It is m obile and variable in length. It is related superiorly to loops of small bowel. Blood supply (cid:142)(cid:3) Caecum and appendix: from the superior mesenteric and ileocol ic arteries (cid:142)(cid:3) Ascending colon: from ileocolic and right colic arteries (cid:142)(cid:3) Transverse colon/flexures: from the right middle and left colic arteries (cid:142)(cid:3) D escending colon: left colic artery (cid:142)(cid:3) Sigmoid and upper rectum: left colic, s uperior rectal arteries. Lymphatic drainage This is along the arterial supply. Nodes are si tuated: (cid:142)(cid:3) On the bowel surface (cid:142)(cid:3) Between the layers of the me socolon (cid:142)(cid:3) Along the branches of the mesenteric arteries (cid:142)(cid:3) Alo ng the trunks of the main vessels. THE DIGESTIVE SYSTEM1 71 Marginal artery Superior mesenteric artery Middle colic artery Inferior mesenteric artery Left colic artery Right colic artery Sigmoid branches lleo-colic artery Superior rectal artery Appendix Fig. 3.12 The arterial blood supply of the large intestine. From Applied Basic Science for Basic Surgical Training, (ed. A. T. Raftery), 2000. Reproduced with permission from Churchi ll Livingstone CHAPTER 3 Anatomy for surgeons 72 The appendix Surface markings The vermiform (worm-like) appendix is an appendage of the cae cum lying in the right iliac fossa. When inflamed, maximum tenderness is classically felt o ver McBurney s point (one third of the way along a line drawn from the anterior superior il iac spine to the umbilicus). Features It is 8 \200\22310cm long and 6 \200\2238mm in girth. Its base is attached to the caecum at the point of convergence of the three taenia coli on the posteromedial wall (see McBurney s point, above) or responding to McBurney \200\231s point on the surface. It contains numerous aggregations of lymphoid tissue in its wall and has a small lumen. It is covered by peritoneum and has a well-formed mesoappendix derived from the posterior laye r of the mesentery of the lower ileum. It is in the mesoappendix that the appendicular vess els lie. Blood supply The appendicular artery is a branch of the posterior caecal from the ileocolic artery. It gives off 2 \200\2233 branches to the appendix during its course in the free cr escentic edge of the mesoappendix. Variations in position The appendix may be freely movable. Common variations in order of fr equency are: (cid:142)(cid:3) Retrocaecal (62%): sometimes extending to the right lobe of t he liver, or in the serous coat of the caecum (cid:142)(cid:3) Pelvic (34%): rectal examination may produce pain (cid:142)(cid:3) Paracae cal (2%) (cid:142)(cid:3) Preileal (1%) (cid:142)(cid:3) Retroileal (0.5%). This page intentionally left blank