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Anatomy Exam 2 Objectives

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ANATOMY OBJECTIVES LEC 16: ORGANIZATION OF THE THORAX, ABDOMEN, & PELVIS - Describe the basic architecture of the trunk and trunk wall o Thin musculoskeletal shell enclosing large space o Subdivisions lined by serous membranes/sacs (ie. Parietal pleura/pericardium/peritoneum) o Each sac invaginated (indented) by organ o Viscus = indenting organ that gainsa visceral covering o Lumen of the sac (parietal/visceral sac that organ has indented) becomes a potential space (pleural/pericardial/peritoneal cavity) o Cavity contains fluid to separate invaginated organ with its visceral innervation, blood supply, and lymphatic drainage from the cavity wall and its somatic innervation, blood supply, and lymphatic drainage o Trunk st  Limits: superior thoracic aperture 1T , 1 ribs, upper border of manubrium sterni) to inferior pelvic aperture; includes bony pelvis and perineum; separated from thigh anteriorly by inguinal ligament line  Supported by vertebral column (attached to ribs above and hip bones below) and erector spinae • Scalene muscles – suspend ribs 1 and 2 from cervical vertebrae • Sternocleidomastoid – raises manubium against mastoid process • Trapezius – suspends pectoral girdle (scapular spine, acromion, and clavical) from cervical vertebrae and base of skull  Subdivisions: thoracic and abdominopelvic regions separated by respiratory diaphragm • Thoracic cavity – opens into root of neck via thoracic inlet (superior thoracic aperture) o Subdivided into right hemithorax and left hemithorax by mediastinum (mediastinum contains fibrous pericardial sac that is tough, inelastic and fused to upper surface of diaphragm • Abdominopelvic cavity – clsed below by conical pelvic diaphragm • Respiratory diaphragm – divides the two cavities; central tendon, peripheral zone of striated skeletal muscle attached to xiphoid process, costal margin, and upper lumbar vertebrae o Posterior origin = arcuate ligaments (3 of them; fascial thickenings) o Rises upward in a dome o Pierced in midline by openings for inferior vena cav8 (T vertebral level), esopha10s (T vetebral level), and aorta12T vertebral level) - Describe the fascial and musculoaponeurotic layers of the trunk wall, the orientation of muscle fibers in each layer, and the orientation of blood vessels and nerves in relation to that of the muscle fibers o Origin from a layer of somatic mesoderm and cells of thoracic and lumbar somites o Wall has series of bands that are each innervated by the VPR of given spinal nerve o Vertical structures are along ventral midline (sternum above, rectus abdominis below); lateral to lumbar vertebrae o Lateral circumferential sheet = 3 layers of skeletal muscle each enclosed in deep fascia; concentric musculotendinous layers  Outer layer – muscle fibers = downward and forward direction (external intercostals, external abdominal oblique)  Middle layer – muscle fibers = upward and forward (internal intercostals, internal abdominal oblique)  Inner layer – muscle fibers = horizontal (transverses thoracis, transversus abdominis)  Linea alba – fusion of the aponeuroses of the three layers o Aponeuroses  Below the arcuate line – all 3 aponeuroses and fascia pass in front of rectus abdominis  Above arcuate line – internal oblique aponeurosis (middle layer) splits to enclose rectus ; external oblique is anterior to internal oblique; transversus dominus is posterior  Tendinous inscriptions – three intertendons that subdivide rectus abdominis muscle and anchor it anteriorly o Layers in inguinal region  External oblique fascia prolonged as external spermatic fascia  Internal oblique fascia prolonged as cremasteric layer of muscle and fascia  Transversus abdominis fascia (fascia transversalis) prolonged as internal spermatic fascia o Ribs – 24 total (12 per side)  True ribs = 1-7  False ribs = 8-10  Floating ribs = 11-12 1  Costal margin = inferior border of rib cage; dividing line beween thorax and abdomen; composed of ribs 7- 10 cartilage  11 intercostal spaces o Sternum = manubrium (T an3 T ) +4body (T -T f5si9n of 4 segments) + xiphoid process; ventral midline  Jugular (suprasternal) notch = upper border of manubrium  Manubriosternal angle of Louis = lower border of manubrium o Umbilicus – L 3L 4n young adults (not kids and elderly) o Orientation of blood vessels – anastomoses consisting of posterior and anterior longitudinal channels linked by circumferential segmental arteries o Fascial layers  Superficial fascia – blends with underlying deep fascia/periosteum • Camper’s fascia = fatty layer over anterior lower abdominal wall • Scarpa’s layer = membranous layer of thin fibroelastic tissue on inner side of Camper’s; potential space between Scarpa’s and deep fascia  Deep investing fascia – encloses each layer of trunk; bound to ribs; fascial planes associated with external and internal obliques and transversus abdominis are prolonged outward into scrotum as spermatic cord and testis coverings  Fasciae of the abdominopelvic cavity – inner surfaces fo walls, roof, floor; aka endoabdominal-endopelvic parietal fascia attached to iliac crest, body of pubis, etc; different names based on location • Inferior diaphragmatic fascia – on lower respiratory diaphragm • Transversalis fascia – anterolateral abdominal wall against transversus abdominis • Iliac fascia – on iliacus • Psoas fascia – on psuas major • Quadratus fascia – on quadratus lumborum • Obturator fascia – on obturator internus • Superior fascia of the pelvic diaphragm – on upper lavatory ani and coccygeus • Visceral fascia – between lining fascia and peritneum; aka extraperitoneal CT on anterior ab wall (little fat) and retroperitneal CT on post ab wall (lots of fat), visceral pelvic fascia (fatty) on upper pelvic diaphragm o CT plane in which organs are embedded o BV, lymphatic drainage, and innervation pathway o Parietal and visceral fasciae blended on under surface of respiratory diaphragm and upper surface of pelvic floor  Fascia of thoracic cavity – continuous layer of parietal endothracic fascia on hemithroacic cavities; sternocostal portion on inside; diaphragmatic portion (superior diaphragmatic fascia on upper surface of diaphragm; mediastinal portion – forms pericardial sac • Visceral fascia only at core of mediastinum to support trachea, esophagus, thoracic duct and great vessels o Innervation  General somatic via VPR of spinal nerves  Trunk wall derived from hypomeric regions of somites  Segmental origin due to narrow striped pattern of innervation that start posteriorly and sweep down and forward to ventral midline  Nerves run in neurovascular plane between middle and inner wall layers  Each VPR has GSE and GSA fibers  GSA fibers leave VPR via 2 branches: lateral cutaneous branch (muscle and deep fascia in mid-axillary line) and anterior cutaneous branch (lateral to sternum or through anterior reectus sheet)  GVE postganglionic sympathetic fibers to vascular smooth muscle, sweat glands, arrector pili muscles • T1VPR  2 branches: small 1 intercostals nerve and continues as lower trunk of the brachial plexus • T2-T6VPR  intercostals nerves in 2 -6 spaces; lateral cutaneous branch of 2 intercostals nerve  becomes intercostobrachial nerve across axilla to arm • T7-T11PR (thoracoabdominal nerves)  respective intercostals spaces  continue down and forward to supply ab wall and rectus abdominis  umbilicus supplied by 10 thoracic nerve th • T12PR (subcostal nerve below 1th rib)  parallel route as 11 intercostals nerve • L1VPR  body wall and skin strip going to pubic symphysis via iliohypogastric branch 2 • L 2L 3PR  quadratus lumborum  then enters lumbar plexus; quadratus lumborum gets fibers from sbcostal and 1 lumbar nerves - Describe the arterial supply and venous drainage of the trunk wall, including anastomotic pathways o Posterior longitudinal system – descending aorta (thoracic and abdominal parts) + common iliac arteries + internal iliac arteries and ilolumbar branches o Anterior longitudinal system – subclavian and external iliac artery branches  Subclavian  internal thoracic (internal mammary) artery (per side)  musculophrenic artery and superior epigastric artery  these 2 branches of the internal thoracic anastomose with external iliac artery (branch of inferior epigastric) in the region of the rectus abdominis o Circumferential segmental vessels – link posterior and anterior longitudinal systems  Arise from aorta: posterior intercostals arteries (3-11), subcostal artery, upper 4 lumbar arteries • Costocervical branch of subclavian – supplies posterior arteries th • Internal iliac iliolumbar branch – supplies 5 lumbar artery • Posterior intercostals and anterior intercostals branches of internal thoracic or musculophrenic arteries anastomose • Subcostal and lumbar arteries anastomoes with superior-inferior epigastric arteries in rectus sheath • All 5 lumbar arteries linked by iliolumbar branch of internal iliac and anastomose with deep circumflex iliac branch of external iliac artery o Collateral circulation  Can expand to bypass narrowing (congenital coarctation) or developing aortic obstruction  Can then carry enough blood to supply LE, GI tract, kidneys o Venous drainage  Parallel with arteries  Posteriorly – segmental drainage into ladder-like azygos system fed below by vertically oriented ascending lumbar veins  Azygos vein (right of midline along vertebal bodies)  superior vena cava  Hemiazygos (below) and accessory hemiazygos (above) veins (left of midline)  discontinuous and cross midline to join azygos vein st  1 posterior intercostals vein drains directly into brachiocephalic vein per side  Collateral circulation • Bypass obstruction of inferior vena cava • Vessels of longitudinal anastomosis between superficial inferior epigastric and lateral thoracic veins can expand, become varicose and can be seen under skin - Describe the basic superficial and deep lymphatic drainage patterns of the trunk wall o Deep lymphatic vessels – drain musculoaponeurotic layers of trunk and retrace arterial supply to regional node groups  Vessels following inferior epigastric arteries  end in external iliac nodes  Vessels following sup epigastric, musculophrenic, anterior intercostals arteries  end in internal thoracic node  Vessels following lumbar and subcostal arteries  end in internal iliac and common inilac and lateral aortic nodes  Vessels following post intercostals arteries  end in post intercostals nodes o Drainage from nodes in right intercostals spaces 1-6 and along right internal thoracic artery  right lymphatic duct o All other regional groups  thoracic duct (on left) o Superficial lymphatic vessels – drain skin and underlying superficial fascia  Trunk quadrants: right and left, above umbilicus and below midline • Lower quadrants  drain first to superficial inguinal nodes  then via external iliac, common iliac, lateral aortic nodes drain to  thoracic duct (on the left) • Upper quadrants  posterior and ant axillary nodes  then drain via central, apical axillary nodes into  subclavian lymph trunks  thoracic duct (left) or right lymphatic duct (right) - Describe the major spaces enclosed within the trunk wall o Pericardium – encloses the heart o Pleura (2) – enclose the lungs o Peritoneum – potential space between visceral and parietal peritoneums o Thoracic cavity o Abdominal cavity - Distinguish the thoracic cavity from the pleural and pericardial cavities and the 3 abdominal cavity from the peritoneal cavity o Thoracic cavity vs. pleural and pericardial cavities  Thoracic cavity – contains heart, lungs, great vessels, esophagus, trachea, Bronchi, thymus, paired vagus nerves, paired sympathetic chains, thoracic duct  Pleural cavities (2) – holds lungs  Pericardial cavity – holds heart o Abdominal cavity vs. peritoneal cavity  Abdominal cavity – holds the bulk of the viscera below thoracic cavity • Stomach, liver, GB, spleen, pancreas, urinary bladder, intestines  Peritoneal cavity – potential space between parietal and visceral peritoneums - Describe a serous membrane and distinguish between “parietal” and “visceral” o Serous membrane – mesothelium + subserous connective tissue o Parietal – forms walls (parietes) of body cavity o Visceral – applied to organs (viscera) confined by cavities  Mesenteries – sheet-like extensions of visceral serous membranes; ligaments linking organ to another or to body wall at parietovisceral reflections (the actual “mesentery” links small intestine to posterior abdominal wall) o Reflections – changes in basic contours of serous membranes; 2 types  Parietal – serous membrane reflected from one parietal surface onto another (ie. Costodiagragmatic reflection – line along which parietal pleura passes from inner surface of rib cage to upper surface of diaphragm)  Parietovisceral – serous membrane passes from wall of body cavity onto surface of organ lying in confines of cavity (ie. Parietovisceral reflection – line along which pleura passes from medial wall of pleural cavity onto lung surface) • All BV, nerves, lymphatics passing to/from an organ lie within embrace of the appropriate parietovisceral reflection(s) - Explain how an organ may be confined by a body cavity and yet not lie “within” it (example used in lecture: pleural cavity and lung) o Lung confined by pleural cavity but lies within thoracic cavity o Heart confined by pericardial cavity but lies within thoracic cavity - Explain the anatomical, functional, and clinical significance of parieto-visceral reflections of the serous membranes (example used in lecture: the pleura) o Parietovisceral – serous membrane passes from wall of body cavity onto surface of organ lying in confines of cavity (ie. Parietovisceral reflection – line along which pleura passes from medial wall of pleural cavity onto lung surface) o All BV, nerves, lymphatics passing to/from an organ lie within embrace of the appropriate parietovisceral reflection(s) - Explain what is mean by the term “mesentery” o Mesenteries – sheet-like extensions of visceral serous membranes; ligaments linking organ to another or to body wall at parietovisceral reflections o The actual “mesentery” links small intestine to posterior abdominal wall - Describe the boundaries of the inguinal canal and compare the contents of the canal in the male and the female o Boundaries  Between internal and external rings  Entrances – deep ring (lateral) and superficial ring (medial)  Floor – medial half of inguinal ligament, lateral crus of superficial inguinal ring  Anterior wall – internal oblique (laterally) and external oblique (medially)  Posterior wall – transversalis fascia (laterally) and conjoint tendon (medially)  Roof – arching free border of conjoint tendon o Male contents  Spermatic cord  Genital branch of genitofemoral nerve (1 -2 ) – innervates cremaster and scrotal skin  Ilioinguinal nerve (1 ) – plane between external and internal obliques running below spermatic cord; emerges from superficial inguinal ring to supply skin over upper and medial thigh  Cremaster reflex = ilioninguinal nerve + genitofemoral nerve  light stroke of upper inner thigh  reflex contraction of cremaster muscle  elevation of testis • Sensory stimulation via ilioninguinal nerve and/or femoral branch of genitofemoral nerve • Muscle stimulation via genital branch of genitofemoral nerve 4 o Female contents  Round ligament of uterus  Ilioinguinal nerve - Explain the difference between direct and indirect inguinal hernias o Direct inguinal hernias  External inguinal ring in front of Hesselbach’s triangle  Posterior reinforcement of abdominal wall = transversalis fascia and conjoint tendon  Cause – increased intra-abdominal pressure forces intestine in peritoneal covering through the inguinal triangle and into external ring  Located/leave ab cavity medial to inferior epigastric vessels o Indirect inguinal hernias  Connection between abdomen and scrotum remains open = persistent processus vaginalis (PPV)  Intestinal loops herniate into sac by PPV  descend through deep ring, inguinal canal, and superficial ring into scrotum  causes congenital/indirect hernia  Hernia leaves ab cavity lateral to inferior epigastric vessels  More common in males than females LEC 17: DEVELOPMENT OF THE BODY CAVITIES & LUNGS - Understand how the intraembryonic coelom is formed and the changes it undergoes as the embryo grows and folds o Appears in the 3 week o Gastrulation converts 2-layer embryo into 3-layer embryo (3 germ layers) o Intraembryonic mesoderm on both sides of the notochord differentiate into three columns (med to lat): paraxial, intermediate, and lateral column  Paraxial column – divided into somites (segments) – devpt of skeletal elements, skeletal muscles, dermis  Lateral column – spaces within column unite to form intraembryonic coelom (extends cranially and caudally) o Intraembryonic coelom (IC) develops into pericardial, pleural, and peritoneal cavities (weeks 5-7) o Folding embryo converts IC into closed cavity  Lateral plate mesoderm splits into intraembryonic somatopleuric mesoderm (parietal mesothelium) and intraembryonic splanchnopleuric mesoderm (visceral mesothelium)  Cavities formed on both sides of embryonic disc are first open to amniotic cavity but eventually close and join to form IC cavity - Understand how the intraembryonic coelom is subdivided into the pericardial, pleural and peritoneal cavities o Peritoneal cavity  Cephalocaudal and lateral folding of embryo leads to septum transversum (mesoderm block) developing cranial to cardiogenic area descending to mid-ventral region superior to yolk sac  Septum transversum separates thoracic and ab cavities  Septum transversum now partially separates intraembryonic coelomic cavity into superior primitive pericardial cavity (contains heart) and inferior peritoneal cavity (becomes abdominal and pelvic cavities)  Septum transversum attached to lateral and ventral ab wall leaves 2 pericardiaoperitoneal canals between primitive pericardial and inferior peritoneal cavities  Phrenic nerves elongate as septum transversum moves caudally (C3-C5 fibers join to become phreni nerve)  Septum transversum myoblasts mostly yield diaphragm muscles so these are innervated by C3-C5 o Pericardial cavity & Pleural cavities th  Pericardial sac formed by pleuropericardial folds in 5 week  Folds meet and fuse at end of 5 week at midline  subdivision of primitive pericardial cavity into ventral definitive pericardial cavity and left and right pleural cavities  Roots of pleuropericardial folds fold towards ventral midline, fuse, and surround developing heart as pericardial sac  Pericardial sac = fibrous pericardium (body wall mesenchyme) sandwiched between 2 layers of somatopleuric mesoderm • Serous pericardium = outer layer on pericardial cavity side • Mediastinal pleura = outer layer on pleural cavity side  Phrenic nerves run through sac within fibrous pericardium  Pleuroperitoneal membranes seal off pleural cavities and peritoneal cavity from each other  Pericardioperitoneal canals = spaces for lungs  Lung buds (respiratory diverticulum) appear at day 22 5 o Lung development was not included as an objective: see page 17 of syllabus - Describe the development of the diaphragm and how it affects the subdivision of the intraembryonic coelom o Myoblasts from septum transversum invade pleuroperitoneal membranes and form most diaphragm muscles o Phrenic nerves accompany myoblasts o Septum transversum part that is devoid of muscle gives rise to central tendon of diaphragm o Diaphragm = composite of 4 embryonic structures  Septum transversum – central tendon of diaphragm  Pleuroperitoneal membranes  Mesoderm of body wall (dorsal and lateral) - muscle  Esophageal mesenchyme – forms right and left crura of diaphragm o Innervation = phrenic nerve and by 7 -12at periphery 3C ,4C 5 C keep the diaphragm alive) o Development completed by week 7 end - Understand the developmental anomalies encountered in this region including omphalocele, gastroschisis, and congenital diaphragmatic hernia o Congenital diaphragmatic hernia(CDH)  1/2000 biths  80% of anomalies on left side (said 90% during lecture)  Incomplete union of pleuroperitoneal membrane and septum transversum and failure of muscular tissue to invade from lateral body wall to pleuroperitoneal membrane  Abdominal organs (stomach and intestines) enter thoracic cavity via opening  causes pressure on lung --. Produces pulmonary hypoplasia o Omphalocele  Lack of union of body folds at umbilicus  Due to lack of return of midgut from physiological herniation of gut o Gastroschisis  Opening located lateral to umbilicus  Elevated levels of alpha-feto protein in amniotic fluid  Ab contents come out of ab cavity directly into amniotic fluid without any peritoneal covering  This part of gut can be damaged by the contact with amniotic fluid o Esophageal hiatal hernia  Due to shortness of esophagus  Upper part of stomach may remain in thorax o Parasternal hernia  Due to lack of muscular tissue devpt in part of diphragm  Produces gap between sternal and costal region o Cleft sternum (ectopic heart)  Due to defect in ventral wall of thorax and abdomen caused by failure of head and lateral folds to unite o Respiratory distress syndrome  Affects 2% of newborns and premature infants  Lungs don’t inflate due to lack of surfactant - Explain what polyhydramnios and oligohydramnios mean, how they both arise, and what these findings indicate about the development of the embryo/fetus o Polyhdramnios – too much amniotic fluid (> 1L) that can arise from esophageal atresia  Findings indicate that fluid can’t be degraded quickly because esophagus may be closed off o Oligohydramnios – too little amniotic fluid that can arise from renal agenesis or obstructive uropathy  Findings indicate that kidneys are not working because fluid is not being urinated out so volume remains low LEC 18: THORAX, LUNGS & PLEURA - Understand the anatomical relationships of the pleura and lungs o Parietal pleura – lines pleural cavity underneath endothoracic fascia (underlies ribs, innermost intercostals muscles, transverse thoracic muscle) o Visceral pleura – lines lungs o Left and right pleural cavities are independent of each other o Mediastinum separates pleural cavities and is subdivided into 4 regions - Understand the pleural spaces and recesses, including the potential spaces, which can become actual spaces o Pleural recesses – regions of parietal pleura next to other parietal pleura where lung fails to fill pleural cavity 6 (pleural cavities are larger than ung volumes)  During inspiration, lung expands into but never completely fills recesses  Left and right costodiaphragmatic recesses – parts of pleural cavity between costal pleura and diaphragmatic pleura; blunting – presence of pleural fluid accumulation  Costomediastinal recess – part of the left pleural cavity between mediastinal pleura and costal pleura • Insignificant on right side • Insert needle into pericardial cavity or heart next to recess to avoid pneumothorax risk o Intrathoracic cavity – potential space between pleural layers  Pneumo/hemo/hydrothorax result from introduction o air/blood/fluid respectively  Pleural fluid – lubrication between parietal and visceral pleura to allow visceral to slide over parietal; keeps lung inflated o Potential spaces – costodiaphragmatic and costomediastinal recesses b/c parietal pleura is apposed to parietal pleura - Know the blood supply, innervation, and lymphatic drainage of the lungs and pleura o Blood supply  Pleura • Visceral = bronchial: left (aorta); right (variable) • Parietal = same as thoracic wall: posterior intercostals, anterior intercostals, internal thoracic, subcostals • Pulmonary veins for both visceral and parietal  Lungs • Arterial systems (2) o Pulmonary system – right ventricle of heart  pulmonary trunk  L pulm artery (anterior to arch of descending aorta; connected to arch by ligamentum arteriosum; crosses left main stem bronchus and superior of left bronchus: and R pulm artery (crosses right main stem bronchus and lies superior to right bronchus) o Nonrespiratory system – bronchial arteries (oxy); both L and R arise from descending aorta at level of tracheal bifurcation (T -T ) 4 5 • Venous system: bronchial and pulmonary veins o Pulmonary – left and right superior and inferior pulm veins enter left atrium separately; variations common (3-5 openings into left atrium) o Nonrespiratory – bronchial veins o Innervation  Pleura • Visceral – none (therefore insensitive to pain) • Parietal – intercostals and phrenic nerves (irritation = referred pain along intercostals nerve and root of neck and shoulder)  Lung • Thoracoabdominal nerve • Sympathetic from chain – L and R symp Chains provide fibers to ant and posterior Pulmonary plexuses on ant and post Aspects of main stem bronchi; symp GVE are needed to see this picture. Mediate vasoconstriction in pulm vascular Bed and secretomotor activity in bronchial glands • Parasympathetic from vagus nerve – L and R vagi pass off to main stem bronchi and Give off to ant and post pulm plexuses; GVE from vagus innervate bronchial Smooth muscle (excessive stimulation = asthmatic syndrome); GVA respiratory reflex afferents • GVA and GVE  Regulation of respiration = stretch reflexes • Stretch receptors in lungs innervated by vagus nerve neurons o Lung stretched  GVA inhibit respiratory center of brainstem (end-inspiratory reflex) o Similar GVA end-expiratory reflex • Glossopharyngeal (CN IX) and vagus (CN X) nerves innervate carotid and aortic bodies and sinuses respectively which monotor changes in oxygen and hemodynamic pressure respectively 7 o Lymphatic drainage  Pulmonary lymph nodes – associated with lobar bronchi; drain from alveolar regions  Hilar/bronchopulmonary nodes – at root of lung; receive lymph from pulmonary nodes  Tracheobronchial nodes – along main stem bronchi  Bronchomediastinal/tracheal nodes – unite with parasternal nodes and drain into subclavian veins  Metastatic spread of lung carcinoma = clinical correlation – if lymph node is blocked, backup through lymph connections to contralateral lung or celiac nodes in epigastric region of abdomen - Confidently describe the three dimensional relationships within the thorax o R lung (3 lobes) and L lung (2 lobes)  Apex in cupula at base of neck  Root of lung on mediastinum  Structures entering/leaving hilus = primary bronchus, pulm artery and veins, bronchial lymphatics, hilar lymph nodes  Pulmonary ligament – maintains visceral/parietal connection along mediastinum o Trachea  In superior mediastinum  C shaped cartilage  Bifurcates into main stem bronchi at carina (septum) behind sternal angle at T 5 o Primary bronchi  Posterior in hilus behind pulmonary arter (ntermediate0 and pulmonary vein (ant) • R main stem – wider, shorter, more vertical; most probable resting place for large aspirated aspects • L main stem – narrower, longer, more horizontal b/c heart is towards left - Be able to describe the mechanics of respiration and the movements of the thoracic cage and muscles involved o Ventilation = breathing / Respiration = alveolar gaseous exchange  Moves gases through airways with decreasing diameters (airway = conducting and respiratory portions)  Conduction – trachea, bronchi as far as terminal bronchiole; air at end of inspiration in end of conductive portion doesn’t exchange gases with blood  Respiratory – respiratory bronchioles, alveolar ducts, alveolar sacs and alveoli  Negative pressure in lungs keeps them inflated o Reduction of vital capacity (flail chest, diaphragmatic paralysis, pneumothorax, pleural effusion, loss of intrinsic elasticity) or obstruction of airway (mucus, asthma, neoplasm) reduces ventilation; results in dyspnea or produces cyanosis o Gaseous exchange – in respiratory portion (alveoli surrounded by capillaries  Alveolar respiration – exchange of gases across blood-air barrier that occurs due to differences in partial pressures between venous blood and alveolar air  Ox blood in pulmonary veins reaches same pressure as alveolar air  CO e2cretion and O a2sorption may be reduced when blood-air barrier is blocked as in alveolar-capillary block  Gas diffusion across alveolar membrane due to memb thickness, surface area, pressure differentials  Pulmonary fibrosis, pulmonary edema, hyaline membrane disease – increase effective thickness of diffusion pathway  poor oxygenation o Movements of thoracic cage  Expiration – passive; no diaphragm contraction  Inspiration – active; diaphragm pulls down post contraction; works with sternocleidomastoid and intercostals muscles LEC 19: HEART & MEDIASTINUM - Identify the boundaries and divisions of the mediastinum and the contents of, and anatomical relationships within each portion o Middle mediastinum  Boundaries • Left and right pleural cavities 8 • Diaphragm • Anterior and posterior coverings of fibrous pericardium • Superior boundary of the left and right pulmonary arteries  Contents • Roots of lungs • Ascending aorta • Pericardial cavity and heart • Pulmonary trunk and left and right pulmonary arteries • Left and right superior and inferior pulmonary veins • Superior and inferior venae cavae • Arch of the ayzgos vein • Left and right phrenic nerves • Lymph nodes o Superior mediastinum  Contents • Thymus gland • Vascular structures running to and from heart o Veins = anterior/towards the right o Arteries = located behind the veins/towards the left o Brachiocepahlic veins  superior vena cava o Ascending aorta and aortic arch of which branches include:  Left and right coronary arteries  Right brachiocephalic artery  R common carotid & R subclavian  Left common carotid artery  Left subclavian artery o Posterior mediastinum  Boundaries • Mediastinal pleura on either side • Diaphragm below • Lies behind pericardial sac • Superiorly continuous with superior mediastinum  Contents • Descending aorta whose branches include: o Ligamentum arteriosum o Intercostal arteries – anastomose with internal thoracic arteries o Bronchial arteries o Esophageal branches • Esophagus • Thoracic duct – posterior to left subclavian vein • Venous drainage o Azygos vein (Receives R posterior itnercostal veins, R bronchial veins, hemiazygos vein)  superior vena cava at 4 o Accessory hemiazygos and hemiazygos veins • Thoracic sympathetic trunk • Vagus nerve - Discuss the layers of the pericardium and their clinical significance o Fibrous pericardium (layer 1)  Outer layer of tough connective tissue  Attached to central tendon of diaphragm and to sternal periosteum  Prevents acute overdistension of heart but will stretch with time for chronic heart enlargement (congestive heart failure)  Continuous with adventitia of aorta, upper pulmonary trunk, sup/inf venae cavae, pulmonary veins o Serous pericardium (layer 2)  2 parts • Parietal serous pericardium – lines pericardial cavity 9 • Visceral serous pericardium (epicardium) – covers the great vessels and heart surface  Pericardial fluid – allows frictionless beating of heart o Sinuses  Oblique – in pericardial cavity posterior to heart; dead-end surrounded by pulmonary veins  Transverse – behind ascending aorta and pulmonary track; can pass ligature through transverse sinus and around aorta and pulmonary trunk to control hemorrhage - Describe the anatomical position of the heart and its major vessels o Position  Pericardial sac covered with visceral pericardium  Transverse diameter < half the diameter of the chest o Boundaries  1/3 of heart R of the midline; 2/3 to the left  R (acute) border delineates superior vena cava, R atrium, and inferior vena cava  Inferior border is delineated by the R ventricle  Apex = tip of L ventricle  Left (obtuse) border is formed by the L ventricle o Surface structures  Coronary (arioventricular) sulcus • Encircles heart • Divides atria from the ventricles • Contains (all are embedded in fat): o Circumflex branch of L coronary artery o R coronary artery o Coronary sinus o Small cardiac vein  Anterior interventricular sulcus • Marks location of interventricular – separates ventricles • Contains: o Anterior interventricular artery (LAD – left anterior descending; branch of L coronary artery) o Great cardiac vein - Identify the prominent structures of the heart: blood vessels, chambers, and valves o Blood vessels  Arterial circulation • L and R coronary arteries supply myocardium and epicardium (visceral pericardium) • R coronary artery o R aortic sinus  R coronary artery  coronary sulcus o Branches  Nodal branch  R atrium & SA node  R marginal branch  part of R ventricle  Posterior interventricular (IV) (descending) branch  posterior third of interventricular septum • L coronary artery o L aortic sinus  L coronary a.  ant interventricular & circumflex arteries o Branches  Ant IV (descending) artery  ant IV sulcus  ant aspects of L and R ventricles  Circumflex a.  in coronary sulcus toward left border and around base of heart • Circulation variations o Right dominant – R coronary artery = origination of posterior IV branch o Left dominant – L coronary artery = origination of posterior IV branch • Anastomoses – few; most are true end arteries  Venous circulation • Coronary sinus (receives most of venous return from epi and myocardium and lies in coronary sulcus)  R atrium (betw inf vena cava opening and right AV valve0 o Tributaries  Great cardiac vein – in ant IV groove; accompanies ant IV artery 10  Middle cardiac vein – in post IV groove; accompanies post IV artery  Small cardiac vein – in coronary sulcus R of opening of coronary sinus; accompanies R coronary artery and marginal branch • Least cardiac (thebesian) veins – in heart walls o Drain endocardium and innermost myocardium o Empty into atria with fewer draining into ventricles o Chambers  R atrium (thinnest walls) • Receives sup vena cava, inf vena cava (incompetent in the adult) – in fetus, brings oxy blood through foramen ovale into left atrium, and coronary sinus • Pectinate muscles on wall • Right auricular appendage – muscular walls; potential site for thombus formation – can yield pulmonary embolism • Empties into R ventricle via R AV/tricuspid valve • Fossa ovalis – remnant of fetal foramen ovale; in interatrial septum  R ventricle • Muscular walls with trabeculae carneae and papillary muscles • Blood enters via tricuspid/AV valve o 3 valve cusps: ant, post, septal – each tethered via chordae tendinae that in turn attach to papillary muscles o tricuspid valve prevents regurgitation of blood back into R atrium during ventricular systole (contraction) • interventricular septum – muscular with small membranous upper portion (site of ventricular septal defect – VSDs) TIFF (LZW) decompressor are needed to see this picture. VSD – result in left to right shunt due to pressure differential; if pulmonary stenosis present, R to L shunt yielding cyanosis and “blue baby syndrome”; principal factor in tetralogy of Fallot • Pulmonary semilunar valve – 3 semilunar cusps (left, right, anterior); prevents blood in pulm trunk from going back to R ventricle during ventricular diastole (relaxation)  L atrium (thick walls) b/c of effort needed during atrial systole to overcome elasticity of very thick left ventricular walls • Receives blood from 2 pulm veins on either end (sometimes 3 on right and 1 on left) • Contains fossa ovalis (on septal wall) – remnant of embryonic foramen ovale • AV mitral/bicuspid valve enters into L vesicle  L ventricle (thickest wall – 3 times as thick as R ventricle) to overcome vascular resistance of systemic vascular bed • Left AV (bicuspid/mitral) valve – blood from L atrium to L ventricle; has ant and post cusps tethered via chordae tendinae • Outflow o Aortic semilunar valve – 3 cusps (right, left, post) – prevents blood from leaving aorta and entering ventricle during ventricular diastole • Ascending aorta at level of aortic valve o Aortic sinuses – aortic wall depressions behind valve cusps; accommodate volume of open valve leaflets to reduce turbulent flow during ejection o Provide origins of coronary arteries o Elastic to accommodate ejected blood volume and maintain diastolic pressure - Discuss some clinical issues, from your understanding of the gross anatomy of the heart o Ischemia – obstruction in coronary artery o Angina pectoris – pain associated is referred to precordium, epigastrium, shoulder left arm o Coronary perfusion – blood flows through coronary circulation of the left ventricle only during diastole because left ventricular systolic pressure and L ventricular transmural pressure are > or = to aortic systolic pressure o Mitral valve insufficiency – transmission of L ventricular systolic pressure to L atrium and pulm vascular bed causes R heart failure o Mitral stenosis – manifests on auscultation as late diastolic murmur - Confidently place a stethoscope on the chest to listen to various heart sounds (valvular defectQuickTime™ and ave but see in syllabus) are needed to see this picture. o A = aortic semilunar valve sounds 11 nd  Project to right of sternum over 2 intercostals space  Heard in neck over carotid artery o P = pulmonary semilunar valve sounds nd  Project to left of sternum over 2 intercostals space  Murmur by ductus arteriosus heard lateral to this point o T = tricuspid valve sounds  Project to midline th  Left side of sternum at 5 intercostals space o M = mitral valve sounds  Projects to apex of heart at 5 intercostals space below left nipple - Understand the innervation of the heart o ANS controls heart rate and ejection volume o Parasympathetic  Vagus nerve – send fibers over heart surface and to nodal areas  Slows heart rate and reduces stroke volume o Sympathetic  Postganglionic sympathetic nerves run from upper symp chain ganglia to heart  Symp fibers end in vicinity of SA and AV nodes and ventricular muscle  Accelerates heart rate and increases stroke volume - Discuss how the fetal cardiovascular system differs from the adult and the changes that take place postnatally o Ligamentum arteriosum = remnant of embryonic ductus arteriosis and is branch of descending aorta o Fossa ovalis = remnant of embryonic foramen ovale; contained on septal wall of left atrium - Outline the flow of lymph fluid from various structures in the thorax o Lymph from body below diaphragm returns to systemic circulation via thoracic duct (flow rate = 2-4 L of chyle/day) o In abdomen – duct originates in cisterna chili (12 T between crura of diaphragm and post to aorta0 o In thorax – duct behind esophagus; right of aorta o In superior mediastinum – arches over left pleura and post to L subclavian vein where it enters at angle formed by juncture of vein with L internal jugular vein o Chylothorax – when chyle from ruptured/severed thoracic duct drains into R or L pleural cavity - Discuss the autonomic nervous innervation of the thorax structures o Sympathetic = 2 motor neurons: myelinated preganglionic (presynaptic) neuron and unmyelinated postganglionic (postsynaptic) neuron  Preganglionic fibers – from spinal cord to symp chain of ganglia • Cell bodies pf presynaptic symp neurons – T1– L2; neurons associated with heart are between 1 and T 5 • White rami communicantes – provide path for myelinated presynaptic symp neurons between spinal nerves and corresponding thoracic symp ganglion  Postganglionic fibers – from chain of symp ganglia to target organ • Cell bodies of post gang symp neurons – located in 3 cervical ganglia and upper 5 thoracic ganglia • Cervical cardiac nerves – contain unmyelinated postsynaptic neurons; in neck to cardiac and pulmonary plexus to reach target tissue • Gray rami commicantes – have unmyelinated postsynaptic neurons that go from symp ganglia, rejoin corresponding spinal nerve, then bring symp innervation to dermatomes  Effects of symp innervation • Tachycardia (increased heart rate) • Increased strok volume (ejection fraction) • Coronary artery dilation • Piloerection, perspiration, dilation/constriction of peripheral vessels in dermatones o Parasympathetic = 1 myelianted pregang montor neuron and 1 unmyelinated postgang motor neuron  Pregang fibers: from brain to distal parasymp ganglia (close to target) – myelinated presynaptic axons form vagus nerve (CN X)  Post gang fibers – arise from small ganglia close to target; unmeylinated; run to tissue innervated  Effects • Decreased heart rate (bradycardia) • Decreased strok volume • Bronchoconstriction 12 • Increased bronchial secretion o Visceral afferents – mediate sensation from thoracic viscera; go along autonomic paths  Pain afferents follow symp paths • Pain afferents from heart – follow upper 4/5 thoracic cardiac nerves  reach symp chain • White rami communicantes – path for pain afferents between symp chain and T 1T 5pinal nerves; pain afferents go to 1 in order to reach spinal nerve since no white rami in cervical region • Cell bodies of visceral afferents – in dorsal root ganglia of spinal nerves o Reflex afferents – follow parasymp path  Afferents for respiratory and cardiac reflexes travel along vagus nerve - Understand “referred pain” from the heart o Painful stimuli by visceral afferent neurons  enter spinal cord at certain level  brain interprets them as originating from/referred to somatic dermatome at that same spinal level o Pain stimuli form heart  referred to 1 5T dermatomes (upper arm/ant thoracic wall to nipple) o No referred pain to cervical dermatomes b/c no whit erami in cervical region (exception: diaphragm which has cervical origin) - Describe the arterial supply and venous drainage of structures throughout the thoracic cavity o Arterial supply  Descending aorta  branches include: • Esophageal branches (mid esophagus) • Bronchial arteries (bronchial tree) • Intercostals arteries (thoracic wall and anastomoses with internal thoracic arteries) o Venous drainage  Venous drainage • Azygos vein (Receives R posterior intercostal veins, R bronchial veins, hemiazygos vein)  superior vena cava at T 4 • Accessory hemiazygos and hemiazygos veins LEC 20: DEVELOPMENT OF THE HEART & CARDIOVASCULAR SYSTEM - Describe the embryonic germ layer that gives rise to the primitive heart o Splanchnic lateral plate mesoderm – gives rise to heart, BV, lymph vessels o Neural crest cells – from ectoderm o Angioblasts – where mesenchyme is derived from; form endocardial heart tubes which hen fuse to form primordial heart tube (end of week 3)  heart tube position ventral to foregut, caudal to orpharyngeal membrane o Heart development  Mesenchymal cells (derived from primitive streak) move around prechorda plate to form cardiogenic mesoderm  Primitive streak (derived from epiblast of bilaminar disk) contains cardiac progenitor cells - Describe the formation of the bulboventricular loop and the fate of the five divisions of the primordial heart tube o Bulboventricular loop formation  Days 23-28  Heart tube becomes U-shaped loop due to differential growth  Atrium and sinus venosus (SV) – posterior to bulbus cordis and primitive ventricle PV)  Heart apex shifted to left side  Primordial blood flow (controlled by sinoatrial valve) – flows from SV  primitive atrium  PV  bulbis cordis  truncus arteriosus  Heat sac falls into pericardial sac as it forms into vulvoventricular loop  Heart beat = day 22 o 5 divisions of primordial heart tube  Truncus arteriosus  form spiral aortico-pulmonary septum • Continuous with aortic sac  Bulbus cordis  forms conus arteriosus (infandibulum) of right ventricle and aortic vestibule of left ventricle  Primitive ventricle  ventricle (?)  Primitive atrium  becomes rough wall of atrium  Sinus venosus  becomes smooth wall of atrium • Receives umbilic veins (from chorion), vitelline veins (from yolk sac), common cardinal veins 13 (from embryo) - Discuss the formation of the atrioventricular canals, partitioning and development of the atria and ventricles, and septation of the outflow tract o Atrioventricular canal formation  Week 4  Endocardial cushions develop on ventral and dorsal aspects of common atrioventricular canal  Tissue proliferation  Cushions grow toward one another  fuse during week 5  form 2 separate atrioventricular canals o Atria development  Atrial septation • Muscular part – devps via differential growth of muscular walls during chamber expansion • Fibrous part – originates from cushion tissue • Formation of 2 muscular septa: septum primum and septum secundum • Foramen primum closed by cushion tissue  foramen secundum develops within upper part of septum primum; overlapped by septum secundum • Blood passes from RL atrium via foramen ovale (opening in septum secundum); septum secundum and primum act as on-way valve  R atrium devpt • R horn of sinus venosus incorporated into wall fo R atrium and receives venae cavae • Sinus venosus becomes sinus venarum where it is continuous with wall of R atrium; sinus venarum = smooth R atrial wall • Rough wall derived from primitive atrium  this forms the auricle • Crista terminalis = separates smooth and rough wals of R atrium • L horn of sinus venosus – forms coronary sinus – drains blood from vessels that supply heart  L atrium • Dorsal part forms pulmonary veins • Primitive atrium forms auricle (rough wall) part of L atrium – contains pectinate muscles o Ventricle development  Interventricular septum • Week 5  neural crest cells form bulbar ridges (in bulbus cordis) and truncal ridges (in truncus arteriosus) • Week 6  Muscular ridge on floor of primitive ventricle forms primordial interventricular (IV) septum • Week 7  Bulbar ridges fuse with endocardial cuhions  form definitive IV septum: bulbar ridges form membranous portion of septum • Ventricular cavitation yields trabeculae carnae and papillary muscle formation • Proliferation of tissue into lumen of aorta and pulmonary trunk  semilunar valves o Septation of outflow tract (outflow tract = part of L or R ventricle through which blood passes to get to great vessels) • Neural crest cells migrate to begin formation of aorticopulmonary septum  form bulbar and truncal ridges in week 5  aorticopulmonary septum spirals before reaching interventricular septum  creates spiral outflow tract = pulmonary trunk + aorta - Discuss the development of the great vessels of the arterial and venous systems o Arterial system  Three major modifications of primitive vessels (aortic arches, paired dorsal aortae, intersegmental arteries) • Hypertrophy of some vessels • Addition of new vessels • Loss of some vessel segments  5 pairs of primitive vessels form in pharyngeal arches  connect paired cranial dorsal aortae to aortic sac (downstream end of primitive heart)  Aortic arches 1 + 2 regress  Aortic arches 3 + 4 contribute to adult aortic arch and large systemic arteries  Aortic arch 6 connects pulmonary artery to lungs  More specificially about aortic arches (according to lecture); 6 arches develop from aortic sac • 1 -3 pairs  arteries of head and neck • 4 pair  left = arch of aorta / right = R subclavian artery 14 th • 5 pair  degenerate • 6 pair  left = L pulmonary artery, ductus arteriosus / right = R pulmonary artery  At caudal end of fused dorsal aortae: vitelline and umbilical arteries develop  supply GI tracht and send blood to placenta o Venous system  Major veins derived from 3 sets of primitive vessels • Vitelline veins – carry blood back from developing GI tract; contribute to portal system and segment of inferior vena cava • Umbilical veins – carry blood from placenta through liver and eventually regress • Common cardinal system – carries blood from remainder of body; 2 main trunks: anterior and posterior cardinal veins • Embryo starts with separate R and L sets of veins • Venous return shifted to right via formation of anastomoses and loss of longitudinal venous systems on left  Greater variation in veins – most are asymptomatic - Discuss the differences between fetal and early postnatal circulation including shunts involved in fetal circulation, and the fate of the 3 major shunts involved in fetal circulation after birth o Shunts (to go around collapsed lungs)  Foramen ovale – shunt between R and L atria; in developing interatrial septum; shunt to systemic side  Ductus arteriosus – shunt between L pulmonary trunk and aorta; blood entering R ventricle goes into aorta via this duct; some blood goes through lungs and is returned to L atrium via pulmonary veins  Ductus venosus – shunt between umbilical vein and inferior vena cava o Fetal blood flow  Fetal blood gets O in placenta  returns to fetus via umbilical vein  half of blood bypasses liver via 2 ductus venosus  enters IVC directly  remaining blood from umbilical veins drains via portal veins and liver sinusoids  enters hepatic vein  joins bypassed blood in IVC  Blood enters IVC  goes to R atrium (nto as well oxygenated as umbilical vein b/c IVC has deoxy blood from lower extremities/abdomen/pelvis  blood is guided by IVC valve and enters L atrium through foramen ovale  FO valve on L side of septum  resistance to blood flow via collapsed lungs  makes systolic P in R atrium > than in L atrium  causes blood to flow through FO into L atrium  blood (well oxy) mixes with small deoxy amount tha is coming back via pulmonary veins from lungs  blood goes to L ventricle  ascending aorta  coronary, carotid, subclaviain arteries are first major arteries to get blood  oxy-rich blood directed towards heart, brain, head, neck, upper extremities  Small amount of blood is prevented from passing through FO to enter R ventricle: pulmonary vessel resisitance is high  main part of deoxy blood doesn’t pass through pulmonary arteries to lungs  diveretd from L pulmonary artery through ductus arteriosus into descending aorta  mixes with well-oxy blood in aortic arch  mixture occurs after coronary and carotid arteries have been gven off  most mixed blood in descending aorta goes to placenta for reoxygenation  remainder circulates through lower extremity o Postnatal circulation  Fate of fetal structures • Foramen ovale  fossa ovalis (between R and L atrium in septum) • Ductus arteriosis  ligamentum arteriosum • Ductus venosus  ligamentum venosum (in liver) • Umbilical vein  ligamentum teres (in liver) • Umbilical arteries  medial umbilical ligaments  Physical changes – cessation of placental flow and commencement of pulmonary respiration • Umbilical vein clamped  blood flow from IVC decreased  pressure of R side < pressure of L side (BP in IVC and R atrium have immediate fall) • Umbilical arteries clamped  pressure of systemic circulation increases: increase in pulmonary blood flow due to drop in pressure in R side of heart  increase in BP in L atrium • Amniotic fluid in bronchial tree expelled/suctioned  replaced by air  lungs inflate  decreased pressure of pulmonary trunk  Foramen ovale closes • Low R and high L pressure in atria  presses FO (septum primum) against atrial septum (septum secundum)  closure due to pressure differential  eventually fuses after several months to form 15 fossa ovalis • Closure reversible in first week weeks of life  cyanosis • 10-15% don’t have perfect closure  Ductus arteriosus closes • During first few days, may still exist to present murmur but is on its way to close • Bradykinin released from lungs during initial inflation  causes muscular contraction which controls initial closer of DA  amount of blood flowing into lungs and L atrium increases  complete closure at 1-3 months  becomes igamentum arteriosum  Umbilical arteries close • Smooth muscles in vessel walls contract  change in oxygen tension  leads to closure a few minutes after birth  actual obliteration of lumen takes 2-3 months  distal portions of arteries become medial umbilical ligaments  proximal parts remain open as superior vesicle arteries  Umbilical vein and ductus venosus close after umbilical arteries close • After obliteration L mbilical vein forms ligamentum teres hepatis in lower falciform ligament  ductus venosus (goes from ligamentum teres to IVC) obliterated  forms ligamentum venosum - Understand the clinical relevance of: atrial septal defects, ventricular septal defects, dextrocardia, persistent truncus arteriosus, transposition of the great vessels, tetralogy of Fallot, valvular defects, patent ductus arteriosus, and coarctation of the aorta (note: cyanosis = mixed blood) o Atrial septal defects  4 types that include patent (open) foramen ovale • Ostium secundum – septum primum is resorbed or defective septum secundum  result = patent foramen ovale; may not show up until middle adulthood via pulmonary hypertension; treat with surgery (not fatal) • Endocardial cushion defects – in 20% of people with Down’s Syndrome • Sinus venosus ASD – SV not incorporated properly in R atrium (abnormal absorption); very rare • Common atrium – septum secundum and primum do not develop  Defect in devpt of atrial septum  Patent FO present in 25% of cases  ASD may spontaneously close  Surgical correction o Ventricular septal defects  Most common defect: 12-15/10,000  Membranous type (most common) • Failure of devpt of membranous part of IV septum • Hypertension and/or cardiac failure during infancy  Muscular type • Excessive cavitation of muscular wall  Small defects – may be asymptomatic  Large defects – cyanosis or congestive heart failure  Infants have L to R shunting of blood and are acyanotic but R to L shunting eventually occurs and causes cyanosis as pulmonary congestion and R ventricular hypertrophy progress  Some due to improper septation of bulbus cordis – failure of conotruncal ridges to fuse  yields persistent truncus arteriosus; some don’t spiral or don’t equally divide, etc. o Dextrocardia (dextro = right)  Bulbus cordis and ventricle bend to L side rather than right  Displaces future apex to R side rather than L  Normally occurs with other cardiac anomalies: single ventricle, arterial transposition  Major problems if only this structure is reversed; if oeverything is reversed than asymptomatic for the most part  Situs inversus – visceral organs = mirror image of normal positions o Persistent truncus arteriosus  Abnormal devpt of aorticopulmonary septum (conotruncal ridges fail to form/fuse) and one vessel provides systemic, pulmonary, and coronary circulation  VSD defect also usually present and cyanosis is present at birth  Congestive heart failure within weeks if no repair  Surgical repair required to close VSD and to separate vessels 16 o Transposition of the great vessels  Aorta and pulmonary trunk reversed – aorticopulmonary septum didn’t spiral and/or defective neural crest cell migration  Aorta arises from R ventricle  systemic blood recirculates through body  Pulmonary trunk arises from L ventricle  pulmonary blood recirculates through lungs  Associated ASD and VSD allow exchange of pulmonary and systemic circulation – needed for survival  Surgery needed to improve blood moving (cyanosis) o Tetralogy of Fallot  Conotruncal ridges do not equally divide outflow tract lumen – results in pulmonary stenosis, overriding aorta, VSD  tetralogy of Fallot: • Pulmonary stenosis = narrowing of pulmonary trunk • Ventricular septal defect = bulbar ridges do not properly fuse • Overriding aorta • Hypertrophy of R ventricle = needs to pump harder  Most common CHD (congenital heart defect) resulting in cyanosis o Valvular defects  Result from improper bulbus cordis  Atresia of pulmonary semilunar valves • Causes R ventricular hypoplasia b/c blood won’t flow into R ventricle  causes open/patent FO b/c it is only outlet for systemic venous blood to get to systemic arterial side  DA also open b/c only route for blood to get to lungs  Aortic valvular atresia • L ventricle hypoplastic  R ventricle carries workload during fetal life so hypertrophies  wide DA forms b/c only way for O 2rich blood from placenta to enter L systemic side  post-birth,2O blood enters R atrium via atrial septal defect and then into systemic circulation via open DA • Heart transplantation required • Senosis of aortic semilunar valves may occur, causing L ventricle to hypertrophy and cardiac failure to result if no treatment o Patent ductus arteriosus  Ductus arteriosus remains open connecting aorta with pulmonary trunk  1/3-1/2 aortic blood enters pulmonary artery b/c systemic pressure exceeds pulmonary pressure  Re-entry into lungs increases venous return to L atrium and ventricle o Coarctation of the aorta  Aortic lumen below L subclavian artery origin narrows due to abnormal thickening of aortic wall (prox or distal to ductus arteriosus)  Obstruction normally in descending aorta near DA  Post-ductal = asymptomatic  Pre-ductal = collateral circulation impaired b/c oxy-rich blood from placenta reaches LE via DA; after birth, DA stays open and only supplies venous blood from R ventricle to; venous blood from pulm trunk supplies lower extremity and causes cyanosis of LE  10% cases – congestive heart failure during infancy LEC 21: ANATOMY OF THE G.I. SYSTEM & ADNEXAE - NOTE: see clinical correlations in lecture (were not referred to in objectives) - List the organs derived from the foregut , midgut, and hindgut. Identify the blood vessels, lymphatics and nerves that supply them Foregut Midgut Hindgut Organs Derived Pharynx Distal duodenum Distal ½ of transverse colon Esophagus Jejunum Descending and sigmoid colon Stomach Ilieum Rectum Liver Cecum Upper anal canal Pancreas Appendix Spleen Ascending and proximal ½ of 1 part of duodenum transverse colon Arterial supply Celiac trunk & branches Superior mesenteric artery & Inferior mesenteric artery & (all off of anterior branches branches 17 descending aorta) Venous drainage Splenic vein Superior mesenteric vein Inferior mesenteric vein Lymphatic drainage Celiac nodes Superior mesenteric nodes Inferior mesenteric nodes Sympathetic Greater splanchnic nerve Lesser & least splanchnic Sacral splanchnic nerve innervation nerves Parasympathetic Vagus nerve Vagus nerve Pelvic splanchnic nerve innervation - Describe the digestive organs, their gross anatomical features and functions o Esophagus  Structure – skeletal and smooth muscle walls  Fxn – conduct food to stomach  Cardiac sphincter = thick ring of smooth muscle at lower end of esophagus; controls opening to stomach o Stomach  Structure – J-shaped • Lesser (superior border) and greater (inferior border) curvatures • 4 regions: cardia, fundus, body, pylrus • Stomach lining = temporary folds = rugae • Pyloric sphincter = controls discharge of stomach contents into duodenum o Small intestine  Structure • 3 parts: duodenum, jejunum, ileum o Duodenum has 4 parts  1 – next to pylorus; horizontal  2 – descending portion; curves around pancreas head  3 – horizontal; and passes inferior to pancreatic head  4 – ascending part; under inferior border of body of pancreas; extends to duodenojejunal junction  Proximal to jxn – tube bends anteriorly at duodenojejunal flexure  Ligament of Treitz (suspensory ligament of duodenum) – slip of muscle derived from diaphragm and fibromuscular tissue from duodnum; supports flexure; landmark for end of duodenum and start of ileum  Part 1 has mesentery; parts 2-4 are against the posterior abdominal wall during development and eventually covered with peritoneum on anterior surface (secondarily retroperitoneal) o Jejunum and Ileum  Suspended from posterior abdominal wall to mesentery that attaches to wall of root of mesentery  Extend from duodenojejunal junction to first part of large intestine • Blood supply – branches of superior mesenteric artery  vasa recta (straight vessels carrying blood to gut wall) o Jejunal vasa recta LONGER than ileal vasa recta  Fxn – digestion and absorption of nutrients o Large intestine  Structure • 7 parts: cecum, ascending colon, transverse, descending, sigmoid colon, rectum, anal canal o Cecum – blind-ended pouch; ileum enters cecum; no mesentery an ddisplaced from R iliac fossa o Ascending colon – ascends form R iliac fossa to hepatic/R colic flexure; secondarily retroperitoneal b/c mesentery fused with posterior parietal peritoneum o Transverse colon – crosses abdomen (R to L) and ends at splenic/L colic flexure o Descending colon – goes down L side of abdomen to L iliac fossa; secondarily retroperitoneal b/c mesentery fused with posterior parietal peritoneum o Sigmoid colon – extends to rectum in S-shape; has mesentery o Rectum – termina part of L. intestine; fixed and considered pelvic organ o Anal canal – termination of hindgut; fixed and considered pelvic organ • Distinguishing characteristics 18 o Haustra – sacculations of intestinal wall o Teniae coli – 3 longitudinal smooth muscle bands on outer wall o Appendices epiploica – small accumulations of fat that hang off of intestinal wall • Iliocecal valve – thickening of circular smooth muscle = jxn between ileum and cecum (pouch- like); prevents reflux more than it controls bowel passage • Vermiform appendix – extends from inferior part of cecum  Fxn – water absorption and propulsion of indigestible material towards anus for elimination o Liver (accessory organ)  Structure • 2 large lobes = R and L lobes (R larger) • 2 small lobes = quadrate and caudate = parts of the R lobe • heatogastric and hepatoduodenal ligaments • Peritoneal reflections = coronary ligaments, triangular ligaments, faciform ligament • Bare area – rests on diaphragm; no peritoneum  Fxn – endo and exocrine organ; erythropoetic organ; synth bile (R/L hepatic ducts  common hepatic duct); bile goes to gall bladder or duodenum  Biliary system = liver + hepatic ducts + gall bladder + cystic duct + common bile duct (union of hepatic and cystic ducts)  Bile duct enters 2 part of duodenum at major duodenal papilla (ampulla of VateR)  Sphincter of Oddi (circular smooth muscle in duodenal wall) = choledochal sphincter – controls bile flow; contracts when bile isn’t needed to keep bile in GB; if fat present in recently ingested meal, hormones stimulate GB to release bile o Pancreas (accessory organ) nd  Structure – head in curve of duodenum (2 part); tail in hilus of spleen  Fxn • Endocrine - islets of Langerhans produce insulin and glucagons  travel through vascular bed in gland • Exocrine cells produce digestive proenzymes  travel via pancreatic duct  empty into duodenum at major duodenal papilla o Spleen (lymphatic)  Structure – inferior to diaphragm on its L side near the L colic flexure, pancreas, stomach, and kidney • Imbedded between layers of mesentery that connect it to posterior wall via lienorenal ligament and stomach via gastrolienal ligament • Ligaments form L margin of omental bursa • Only hilus (where blood and LV enter/leave) is not covered by peritoneum  Fxn – RBC and WBC storage; destroys aged RBCs - Define the terms peritoneal cavity, visceral and parietal peritoneum, mesentery, peritoneal ligament and omentum o Peritoneal cavity = potential space inside the sac lined by peritoneum; filled with serous fluid o Visceral peritoneum = peritoneum lining organs o Parietal peritoneum = lines cavity o Mesentery = 2 layers of peritoneum fused together  Enclose vessels, nerves traveling to/from organs  Suspend organs from posterior abdominal wall  THE mesentery/mesentery proper = suspends jejunum and ileum  Named by organ they suspend o Peritoneal ligament = 2 layers of peritoneum fused together but more defined by attachments  Connect 2 organs or 1 to abdominal wall  Named for structures they connect o Omentum = fusion of 2 broad mesenteries (4 layers of peritoneum)  Greater omentum – hangs from greater curvature
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