Development of the Heart


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Development of the Heart

  2. 2. Index Index Initial concepts 1 2 The Human development 3 Normal development of the heart 4 Pathology in the heart development 5 Persistent Truncus Arteriosus (PTA) Dextro Transposition of the great arteries (d-TGA) 9 10 Levo- transposition of the great arterie( L-TGA ) 11 Teatralogy of fallot 13 Probe patency of the foramen ovale ( PFO ) 14 Premature Closure of the Foramen Oval 15 Common atrium ( cortrilocularebiventriculare ) 16 Tricuspid atresia 17 Persistent Common AV Canal 18 Elbstein’s anomaly 19 1
  3. 3. Initial concepts Fertilization: a process by which the male and female merge and forms a zygote. Is required capacitation and acrosomal reactions The human life is divided into developmental process by which the body passes though. Basically we may divide it into 2 parts: 1. Intrauterine life: is all process of development of the body after the Zygoteformation until start the extra uterine life. In others words, is a set of developmental process that the human being pass within the uterus. It may be divided into three parts: Conceptus: This occurs when the male and female gametes are uniting, and forms the Zygote. It takes at least 21 days. Embryonic period: isthe perfect product of conception from implantation of the gametes until the 8th week of development. Fetal Period: Is a process that leads with growth and differentiation of tissues and organs that began to develop in the embryonic period. It takes from 9th until the birth. 2. Extra uterine life: is all process of development of the body after intrauterine life, which is characterized by Neonatal (from birth until 4 weeks ), Infancy ( 1st year of life ), Childhood ( from 1 year of life till 12 to 13 year old ), Adolescence (from 12 to 13 until 17 ), adult hood ( from 18 to 21 until 25 ), middle age, old age and consequently the death. The Human development in the intrauterine life is accompanied and marked into a chronologic time in weeks. A normal human being takes 38 weeks or 266 daysto develop fully. If the birth be less than 37th week we use to say that is apreterm birth. All weeks together may be divided into three parts or trimesters, which each one have 12.6 weeks. Critical Period: all weeks are very important because they covers important development of a different organ or even a set of organs, but the 1st trimester takes special attention because the embryo may be more affected, the heart critical period, normally starts at 3th week and finish at the 6th week. The sensitive weeks are marked by the strong action of chemical products, mechanic shocks on the embryo. It starts from 3th week till 8th(this text was adapted from USMLE : Falcon Online –Anatomy review). 2
  4. 4. The human development Embryology: Is a the science which search study the embryo and it development. Embryogenesis: Is the process by which the embryo is formed develops, until it develops into a fetus. The human embryology of the human beings may be divided into the following parts: 1. Zygote: After the fecundation the first cell of a future human being will be formed, this cell is named zygote that is the initial cell which is formed by means of sexual reproduction. It got 46 chromosomes, 23 from the father ( spermatozoid) and 23 from the mother (ovule). It contains a full complement of genetic material and develops into the embryo. It takes place from the 1st day until the 3th day. 2. Cleavage: the zygote pass through several mitotic divisions, which leads directly with a increase of cell number, they are big in size cell, but according to the cell divisions it starts to decrease in size. It takes 1 week of intrauterine life. In humans the cleavage is hotoblastic, in other words, complete. 3
  5. 5. 3. Morula: is the first state of embryonic development after the zygote begins to divide to form a sphere with 64 cells. The name Morula mean mulberry. 4. Blastula: this stage is characterized by the formation of a central cavity filed with fluid named Blastocoel and a inner wall named Blastoderm. 5. Gastrulation: During gastrulation, cell movements result in a massive reorganization of the embryo from a simple spherical ball of cells, the blastula, into a multi-layered organism. During gastrulation, many of the cells at or near the surface of the embryo move to a new, more interior location. It have three layers: Endoderm:the most internal germ layer, forms the lining of the gut and other internal organs. Ectoderm: the most exterior germ layer, forms skin, brain, the nervous system, and other external tissues. Mesoderm: the middle germ layer, forms muscle, the skeletal system, and the circulatory ( This part was adapted from l) Invagination: a sheet of cells (called an epithelial sheet) bends inward. 6. Neurulation: in all vertebrates results in the formation of the neural tube, which gives rise to both the spinal cord and the brain. Neural crest cells also created during neurulation. Neural crest cells migrate away from the neural tube and give rise to a variety of cell types, including pigment cells and neurons. It begins with the formation of a neural plate, a thickening of the ectoderm caused when cuboidal epithelial cells become columnar. Changes in cell shape and cell adhesion cause the edges of the plate fold and rise, meeting in the midline to form a tube. The cells at the tips of the neural folds come to lie between the neural tube and the overlying epidermis. These cells 4
  6. 6. become the neural crest cells. Both epidermis and neural plate are capable of giving rise toneural crest cells( This text was adapted from l). from Patricia Phelps Normal development of heart The heart starts to develop at 3th week and goes until 6th week, during intrauterine life. The heart of the human beings is about the size of the fist. As the body develops, the heart grows at the same rate as the fist. On this way, an infant's heart and fist are about the same size at birth. In human embryos the heart begins to beat at about 22-23 days, with blood flow beginning in the 4th week. The heart is therefore one of the earliest differentiating and functioning organs. 5
  7. 7. The heart begins very early in mesoderm within the trilaminar embryonic disc. In the begin the heart looks like a tube, In the upper part of this tube have two small tubes named arterial trunks, and in lower part another two tuber, which are thicker, named Venous channels, up in the bifurcation is the Atrium. The Cardiac tube grows rapidly in length and the embryonic ventricle takes form of a loop for the right of middle sternal line. According the time is passing by the ventricle follow the middle sternal line and grows and cover the Atrium and veins. The future left ventricle lies to the left of the intraventricular groove. The right ventricle communiques with Troncus Arteriosus. The four chambers of the heart is formed from the convoluted tube, by the development of the tree septa partitioning of the Atria, Ventricles and the trunks. Arteriosus. All this septa develops simultaneously. There is a big groove which separates the Atrium from Ventricle. At this stage, within the heart still do not posses the septum, that way it looks like a vagination, but according to time passed, the cell division inside of the heart creates a septa, the endocardial cushions extend and forms the Septum, which divides the chambers. From the intraventricular region occurs the proliferation of muscular septum that pass across the Common ventricle toward the base of the heart, this process also occurs at the Atrium toward the endocardium cushions( Atrioventricular cushions or endocardial cushions refers to a subset of cells in the primordial heart that play a vital role in proper heart septation ) and progressively constrict the foramen between the Atrial chambers, forming the Foramen Primum. At this moment another foramen arise, it is named Foramen Secundum (which provide uninterrupted blood from right Atrium to the Left) and the Foramen Primum is closed. In the left Atrium arise a muscular tissue, which extend like a curtain ( which works like a valve) on the Foramen Segundum, forming the foramen Ovale ( on this way the blood will flow only from the right Atrium to the left ) . 6
  8. 8. Originally the right and left ventricle share a common of flow channel, Truncus Arteriosus ( from it arise the Aortic arches). The bifurcation of the Truncus Arteriosus, represent two of the Aortic arches, the 4th Aortic archer, which forms the Aorta, and the 6th, which forms the pulmonary artery. From the up tube a piece of tissue came and twist (at 108 º) forming single spiral septum which goes toward the ventricles, is at this moment that the Atrium-ventricular foramen is obstructed by mass of endocardium tissue from the ventricular septum by the Endocardium cushions and Spiral Aortic septum, now is completed the heart chambers. The blood from the left ventricle goes to Aorta, in the right direction. The blood from the right ventricle goes to the Pulmonary artery, which pass near of the aorta turning posteriorly left side of the mediastinum. The blood from the Superior and Inferior Vena Cava goes to right Atrium and them do the right Ventricle, which are inject into the pulmonary artery ( flowing in the Ductus Arteriosus ) to the descending Aorta. The resistance to flow through the collapsed lungs is so great that only a small quantity of blood enters in the Pulmonary arteries. This blood which enters in the Pulmonary arteries back through the Pulmonary veins into the Left Atrium. The oxygenate blood from the placenta enters through a connection in the Inferior Vena Cana, and goes to the right Atrium through and pass through Foramen Ovale and enters into the left Atrium, there they are mixed and then goes from the Left Ventricle to the Aortic artery. When the birth occurs the supplement of blood from the Placenta is interrupt, in order to keep itself alive the infant must breathe to make the respiratory exchange in the lungs. When the lungs are filled with oxygen, the resistance of pulmonary flow is reduced. Oxygenate blood from the lungs goes to Systemic circulation. 7
  9. 9. When the pressure on the left ventricle is biggerthan right the Foramen Ovale is closed.(Robert Rushmer, congenital malformation of the heart, part 1 ) Pathologies in the Heart Development The pathologies of heart (cardiac system) during the intrauterine life may be classified according to defects which follows each embryo development during heart embryogenesis (all the follow disease was adapted from ‘’Embryology fifth edition – Ronald W. Duded’’). Pathologies which are linked to Aorticpulmonary Septum: Persistent Truncus Arteriosus (PTA):It is a rare genetic disorder and teratogens (virus, metabolic imbalance, industrial or pharmacological agent ), which occurs when there is failure of fusion and descent of the spiral ridges of the truncus and conus that supposedly divide into aorta and pulmonic trunck respectively. When the spiral septum fails to completely descend, the aortic and pulmonic trunks are left undivided at their outflow. The truncus takes the place of the both ventricles. The persistent truncus is always accompanied by a membranous ventricular septal defect. 8
  10. 10. The classification of PAT was made in 1949 by Collett and Edwards, according to their classification, it may be classified by the pattern of the pulmonary arteries: Type I: truncus -> one pulmonary artery -> two lateral pulmonary arteries Type II: truncus -> two posterior/posterolateral pulmonary arteries Type III: truncus -> two lateral pulmonary arteries Clinic Picture is: Cyanosis presents at birth (due the mixture of the venous blood- the one which comes from periphery to the heart- and arterial blood- the one which goes from the heart to periphery ) Heart failure may occur within weeks Systolic ejection murmur is heard at the left sternal border Widened pulse pressure ( due the absence of the septum, the diastole are mixed in the both lower chambers ( ventricle) Bounding arterial pulses Loud second heart sound Biventricular hypertrophy Cardiomegaly Increased pulmonary vascularity Hypocalcemia (if associated with DiGeorge syndrome) On the X-ray, the heart looks big and the lungs fields look hazy indicating pulmonary over circulation. Treatment and Management: May be tried surgical repair: Early surgical correction is preferred. The VSD is closed so that the LV is connected to the truncus and the pulmonary arteries are detached from the truncus to be attached to the right ventricle via a conduit. If early surgical repair can not be done, banding of the pulmonary artery is performed to limit the blood flow to the lung and control CHF. 9
  11. 11. Dextro Transposition of the great arteries (d-TGA): Another rare congenital disease, in this case the infact have the 2 biggest blood vessels exchanged, The Aortic Artery carries blood poor in oxygen to periphery of the body, and the Pulmonary artery travel though it blood rich in oxygen. Without an adequate supply of oxygen-rich blood, the body may not work properly and the infanct faces serious complications or death without immediate treatment. The Diagnosis may be during pregnancy or soon after the baby is born. Clinical Picture cyanosis (in peripheral areas : around the mouth and lips, fingertips, and toes ) Pounding heart ( low volume of blood arrive in the peripheral arteries ) Problems breathing Pounding heart Weak pulse Ashen or bluish skin color Poor feeding Treatment There are two types of surgery to repair d-TGA: Arterial Switch Operation: This is the most common procedure and it is usually done in the first month of life. It restores usual blood flow through the heart and out to the rest of the body. During this surgery, the arteries are switched to their usual positions—the pulmonary artery arising from the right ventricle and the aorta from the left ventricle. The coronary arteries (small arteries that provide blood to the heart muscle) also must be moved and reattached to the aorta. 10
  12. 12. Atrial Switch Operation: This procedure is less commonly performed. During this surgery, the arteries are left in place, but a tunnel (baffle) is created between the top chambers (atria) of the heart. This tunnel allows oxygen-poor blood to move from the right atrium to the left ventricle and out the pulmonary artery to the lungs. Returning oxygen-rich blood moves through the tunnel from the left atrium to the right ventricle and out the aorta to the body. Although this repair helps blood to go to the lungs and then out to the body, it also makes extra work for the right ventricle to pump blood to the entire body. Therefore, this repair can lead to difficulties later in life. Levo- transposition of the great artery( L-TGA ) :Is a acyanotic congenital heart defect, which correspond the flow of blood whiting the heart. It forms due an abnormal leftward looping of the primitive heart, which results in the morphologic Left ventricle that will be positioned to the right of the morphologic Right ventricle and to both atrioventricular and ventriculoarterial discordance . In a normal heart, theoxygenated blood is pumped from the Right Atrium into the Right Ventricle, then through the pulmonary artery to the lungs where it is oxygenated. The oxygen-rich blood then returns, via the Pulmonary Veins, to the left atrium from which it is pumped into the left ventricle, then through the aorta to the rest of the body, including the heart muscle itself. Clinical Picture The clinical picture may be divided into two groups, according to the infant conditions Simple l-TGA does not immediately produce any visually identifiable symptoms, but since each ventricle is intended to handle different blood pressures, the right ventricle may eventually hypertrophy due to increased pressure and produce symptoms such as dyspnea or fatigue. 11
  13. 13. Complex l-TGA may produce immediate or more quickly-developed symptoms, depending on the nature, degree and number of accompanying defect(s). If a right-to-left or bi-directional shunt is present, the list of symptoms may include mild cyanosis. The Diagnosis may be performed when the infant still is in theuterowith an ultrasound after 18 weeks gestation. However, many cases of simple l-TGA are "accidentally" diagnosed in adulthood, during diagnosis or treatment of other conditions. Treatment: In the Simple l-TGA has a very good prognosis, with many individuals being asymptomatic and not requiring surgical correction In a number of cases, the (technically challenging) "double switch operation" has been successfully performed to restore the normal blood flow through the ventricles. Teatralogy of fallot :Is a congenital heart defect which involve 3-4 anatomical abnormalities of the heart, that is way it got this name ( teatra is from Greek language, that means ‘’four’’).The heart malformations are: 1. Pulmonary Infundibular Stenosis: A narrowing of the Right Ventricular outflow tract. May occurs in the Pulmonary veins(infundibular pulmonic stenosis ) ou Pulmonary valve ( Valvular stenosis ). 2. Right Ventricular Hypertrophy: Occurs a change in the ventricle wall, it becomes thicker then usual, causing bloot-shaped appearance when takes X-ray picture from the chest. 12
  14. 14. 3. Ventricular septal Defect: Arise a hole between the two Ventricles. Is more accentuated at the upper part of the Septum. In some case is possible the margin of the Septum get a narrowing. 4. Overriding Aorta: In this case arise a bifurcation oih the Aortic valve, which is located at the upper part of the ventricular Septal and is connected with the both Ventricle. Clinical Picture: The clinical features of tetralogy of Fallot are directly related to the severity of the anatomic defects. Infants often display the following: Difficulty with feeding Failure to thrive Episodes of bluish pale skin during crying or feeding (ie, "Tet" spells) Exertional dyspnea, usually worsening with age RV predominance on palpation A bulging left hemithorax Aortic ejection click Squatting position (compensatory mechanism) Scoliosis (common) Retinal engorgement Hemoptysis The Diagnosis is possible through: Hemoglobin and hematocrit values are usually elevated in proportion to the degree of cyanosis. Patients with significant cyanosis have the following, in association with a tendency to bleed: Decreased clotting factors, Low platelet count, Diminished coagulation factors, Diminished total fibrinogen, Prolonged prothrombin and coagulation times. Imaging studies include the following: Echocardiography, Chest radiographs,Magnetic resonance imaging (MRI). 13
  15. 15. Treatment: Surgery is the only effective treatment for tetralogy of Fallot. There are two types of surgery that may be performed, including intracardiac repair or a temporary procedure that uses a shunt. Most babies and children will have intracardiac repair. Intracardiac repair Tetralogy of Fallot treatment for most infarct involves a type of open-heart surgery called intracardiac repair. This surgery is typically performed during the first year of life. During this procedure, the surgeon places a patch over the ventricular septal defect to close the hole between the ventricles. Temporary surgery Occasionally babies need to undergo a temporary surgery before having intracardiac repair. If the infant was born prematurely ( during or before 37 week )) doctors will create a bypass between the aorta and pulmonary artery which increases blood flow to the lungs. (This text was adapted from Pathologies which are linked to Atrial Septum Probe patency of the foramen ovale( PFO ) : This pathology arise in the Foramen Ovale, which normally is closed after the birth by the pressure which the lungs makes at that part. Normally, the left atrial pressure keeps the foramen closed, but if right atrial pressures rise with pulmonary hypertension ,the foramen may open. Clinical Picture: History of stroke or transient ischemic event of undefined etiology Migraine or migrainlike symptoms - Whether symptoms are due to transient ischemic attacks or paradoxical embolism is not clear e_pfo/hic_Patent_Foramen_Ovale_PFO.aspx 14
  16. 16. Neurologic decompression sickness - Seen with PFO in a small percent of scuba divers Acutemyocardialinfarction Systemic embolism, such as renal infarction Fat embolism Paradoxical embolism caused by right atrial tumors that increase right atrial pressure Left-sided valve disease in carcinoid syndrome Treatment The usual care for a patient who has had a stroke is using of blood-thinning medications, such as aspirin or the prescription drugs warfarin (Coumadin) or clopidrogrel (Plavix). These drugs keep the blood cells from sticking together, reducing the risk of blood clot development that could lead to new TIAs or stroke. However, there are risks and inconveniences associated with the long-term use of blood-thinning medications including: Development of ulcers Internal bleeding Bleeding in the brain Blood in the urine Bleeding in the rectal tissue The need to avoid activities that could result in injury, which could trigger internal or external bleeding (This text was adapted from and px) Premature Closure of the Foramen Oval: Premature closure of the foramen ovale is a rare and deleterious condition that can occur as an isolated defect or in association with other congenital anomalies. Although a number of cases have been reported, early case reports often confused probe patency and premature closure. Several previous reports described edematous infants dying in cardiac failure and ascribed these findings in cardiac failure and Septum secundum,which had covered but nor sealed the foramen ovale. Infants with premature closure of the foramen ovale usually are cyanotic or shortly after birth, develop signs of congestive failure, and die in the first few days of life. Only five from 20 lived more than one day. Little attention has been paid in previous reports to an abnormality is observed in 15
  17. 17. the muscle of the left side of the heart associated with this lesion. _ovale_pfo/hic_Patent_Foramen_Ovale_PFO.aspx Common atrium ( cortrilocularebiventriculare ) : It forms a congenital heart defect that enables blood flow between two compartments of the heart called the left and rightatria. Normally, the right and left atria are separated by a septum called the interatrial septum. If this septum is defective or absent, then oxygen-rich blood can flow directly from the left side of the heart to mix with the oxygen-poor blood in the right side of the heart, or vice versa. Clinical Picture: The symptoms depend on the level of development of the septum. A person with no other heart defect, or a small defect (less than 5 millimeters) may not have symptoms, or the symptoms may not occur until middle age or later. Symptoms that do occur may begin at any time after birth through childhood, and can include: dyspnea Frequent respiratory infections in children Sensation of feeling the heart beat (palpitations) in adults Shortnessofbreath withactivity The diagnosis may be as a result of echocardiography. 16
  18. 18. Treatment ASD may not need treatment if there are few or no symptoms, or if the defect is small. Surgery to close the defect is recommended if the defect causes a large amount of shunting, the heart is swollen, or symptoms occur. A procedure has been developed to close the defect without surgery. The procedure involves placing an ASD closure device into the heart through tubes called catheters. The health care provider makes a tiny surgical cut in the groin, then inserts the catheters into a blood vessel and up into the heart. The closure device is then placed across the ASD and the defect is closed. Not all patients with atrial septal defects can have this procedure. Pathologies which are linked to Atrium-Ventricular Septum Tricuspid atresia: is the third most common form of cyanotic congenital heart disease it is a heart defect present at birth in which one of the valves (tricuspid valve) between two of the heart's chambers isn't formed. Instead, there is solid tissue between the chambers. It is caused by a insufficient amount of AV cushions cells, which results in a condition in which there is complete agenesis (refers to the failure of an organ to develop during embryonic growth and development due to the absence of primordial tissue) of the tricuspid valve, that is way there is no communication between the right atrium and right ventricle. If the infant is born with tricuspid atresia, blood can't flow through the heart and into the lungs to pick up oxygen as it normally would. The result is the lungs can't supply the rest of the infant body with the oxygen it needs. The infant with tricuspid atresia tire easily, are often short of breath andhave blue-tinged skin. 17
  19. 19. Generally it is accompanied by: Patent foramen ovale, Intravetricular septum defect, overdeveloped left ventricle, and underdeveloped right ventricle. (this text was removed from Embryology fifth edition – Ronald W. Duded ). Persistent Common AV Canal:is caused by failure of fusion of the dorsal and ventral AV cushions. It results in a condition in which the common AV canal is never partitioned into the right and left AV canals, so that a large hole can be found in the center of the heart. Consequently, the tricuspid and bicuspid valves are represented by one valve common to both sides of the heart. Two common hemodynamic abnormalities are found: 1. .Left-right shunting of the blood from the left atrium to the right atrium, causing an enlarged right atrium and right ventricle. 2. Mitral valve regurgitation, causing an enlarged left atrium and left ventricle. The Clinical Picture: Recurrentrespiratoryinfection Failuretothrive Dyspnea Orthopnea Congestiveheartfailure Cyanosiswithcrying Cyanosiswithstraining Mitral regurgitationmurmur Ventricular septal defectmurmur Arrhythmia Enlargedheart Pulmonaryarteryhypertension The diagnosis may be done by Heart Rate Monitors, Irregular Heartbeat Detection, Heart Electrocardiogram (ECG), Testing, Home Cholesterol Testing. on+Defects&lang=1 18
  20. 20. Treatment Normally may be done a surgurywhich involves closure of the atrial and ventricular septal defects and restoration of a competent left AV valve as far as is possible. Open surgical procedures require a heartlung machineand are done with a median sternotomy. Surgical mortality for uncomplicated ostiumprimum defects in experienced centers is 2%; for uncomplicated cases of complete atrioventricularcanal, 4% or less. Certain complications such as tetralogy of Fallot or highly unbalanced flow across the common AV valve can increase risk significantly. Elbstein’s anomaly:is caused by the failure of the posterior and septal leaflets of the tricuspid valve to attach normally to the annumlusfibrosus; instead they are displaced inferiorly into the right ventricle. It is divided into a larger, upper, ‘’atrialized’’ protion and a small, lower, functional portion. Due to the small, funcutionalprotion of the right ventricle, there is reduced amount of blood available to the pulmonary trunk. It is usually associated with an ASD and Maternal lithium exposure. Clinical Picture Symptoms range from mild to very severe. Often, symptoms develop soon after birth and include bluishcolored lips and nails due to low blood oxygen levels. In severe cases, the baby appears very sick and has trouble breathing. They are: Cough Failure to grow Fatigue Rapid breathing Shortness of breath Very fast heartbeat The diagnosis is made by: Chest x-ray, Magnetic resonance imaging (MRI) of the heart, Measurement of the electrical activity of the heart (EKG), Ultrasound of the heart (echocardiogram). 19
  21. 21. Treatment Treatment depends on the severity of the defect and the specific symptoms. Medical care may include: Medications to help with heart failure Oxygenandotherbreathingsupport Surgery to correct the valve may be needed for children who continue to worsen or who have more serious complications 20
  22. 22. Bibliography Embryology fifth edition – Ronald W. Duded ( BRS - Board review series ) – chapter 5; from page 37-47 USMLE : Falcon Online (Anatomy) – From this collection of videos was adapted to get the materials to formulate the ‘’Initial concepts’’ and another part of the scientific project. Histology lectures from KSMU(General ideas about organization of the scientific project) adapted Gastrulation and Neuralization) Rushmer, congenital malformation of the heart, part 1 ) ideas about the heart pathology) ideas about the scientific project) ideas about the scientific projectProbe patency of the foramen ovale -PFO) ideas about the scientific projectand Tetralogy of Fallot) px ideas about the scientific projectand Tetralogy of Fallot Atrial septal defect -ASD). 21