Embryo Block #2 Exam

Which aortic arch is formed as a result of cranial folding of the embryo?

*1st* aortic arch (forms maxillary artery)

Which aortic arch gives rise to the common carotid arteries?

*3rd* aortic arch

If the fetus were successfully diagnosed with pre-ductal coarctation of the aorta using an echocardiogram, what would a physician likely do to keep the fetus asymptomatic until surgery was appropriate?

*Prostaglandin E* is used to keep the ductus arteriosus patent until surgery can be performed.

In the fetus, there is higher pressure on the right side of the heart than on the left side. What events of birth cause this to reverse (left side now having higher pressure than right)?

1. Cutting the umbilical cord decreases venous return to the right atrium, lowering pressure to that chamber. 2. Filling the lungs with air causes an increase in blood flow through them. This lowers the resistance of pulmonary blood from the right side of the heart, effectively lowering pressure on that side. 3. Increase pulmonary venous return increases the pressure on the left side of the heart.

Aortic arch derivatives

1st arch is MAXimal: Maxillary artery 2nd arch: stapedial arteries 3rd arch: C is 3rd letter, Common Carotid arteries 4th left: aortic arch 4th right: proximal part of subclavian 5th: nothing! 6th both: proximal part of pulmonary arteries 6th left: ductus arteriosus

The initial formation of the ureters and kidneys:

A single ureteric bud sprouts from each mesonephric duct. This bud embeds itself into a collection of mesenchyme called a metanephric blastema. The bud then branches inside the blastema. The ureteric bud will develop into the ureter, while the metanephric blastema will develop into the kidney.

Testicular Hydrocele

As the testes descent, they carry along a portion of the parietal peritoneum, which is called the tunica vaginalis. This is filled with a small amount of fluid. However, abnormally large amounts of fluid can accumulate in this space...this is called a testicular hydrocele.

Tricuspid atresia

Complete closure of the valve between the right atrium and right ventricle (tricuspid valve)

Tetrology of Fallot

Congenital heart defect with 4 components: D: defect (ventricular septum) R: right ventricular hypertrophy O: overriding aorta P: pulmonary stenosis

Typically, a patient with double superior vena cava will be asymptomatic. However, a variation of this anomaly results in cyanosis. What is the nature of this variation?

If the anomalous vein (LSVC) drains into the left atrium; causes deoxygenated blood to be sent through the systemic circuit

Typically, a patient with double superior vena cava (persistent left superior vena cava) will be asymptomatic. However, a variation of this anomaly results in cyanosis. What is the nature of this variation?

If the anomalous vein drains into the left atrium

Transposition of the Great Vessels

If the truncoconal septum forms, but does not spiral, the result is transposition of the great vessels. In this condition, the aorta is connected to the right ventricle, and the pulmonary trunk is connected to the left ventricle.

Describe developmental basis of bifid ureter:

If the ureteric bud branches before it reaches the metanephric blastema, there will be two ureters draining a single kidney that join before they reach the bladder. This is a bifid ureter.

Double aortic arch

Most common symptomatic vascular ring, makes anterior indentation on trachea and posterior on esophagus

Persistent Truncus Arteriosus (PTA)

Persistent truncus arteriosus occurs when no truncoconal septum develops. This anomaly is characterized by incompletely separated ventricles that pump blood out a single outflow tract.

Tetralogy of Fallot

Tetralogy of Fallot results when the ventricular portion of the truncoconal septum forms to the right of the muscular ventricular septum. The result is a set of four interrelated anomalies: overriding aorta, pulmonary stenosis, ventricular septal defect, and right ventricular hypertrophy.

Describe the developmental basis for formation of a urachal fistula (connection from bladder to outside world):

The allantois projects from the cranial end of the bladder and into the umbilical cord. Normally, the lumen of the allantois is obliterated during development. If it remains, the bladder is connected to the outside world via this urachal fistula. Urine will leak from the bladder out the umbilical region through this fistula.

Atrial septum development

The atrial septum is really two opposed partitions. Each partition, or septum, has an opening in it. The *septum primum*, when completely formed, has an opening at the superior end of the atria. This partition is thin and membranous. To the right of the septum primum is the muscular *septum secundum*, which has an opening that is more inferiorly placed. In the fetus, there is higher pressure in the right atrium than the left atrium. Blood forces its way through the *foramen ovale* (the opening in the septum secundum), pushes the thin septum primum to the left, and exits into the left atrium. In the newborn, the pressure differential shifts, so that blood pressure is higher in the left atrium than in the right atrium. This pressure pushes the septum primum against the septum secundum. The two openings are not overlapping, so that blood cannot flow through these openings in this direction.

If a double aortic arch is surgically repaired, what signs/symptoms may persist and why?

The esophagus has the ability to return to its present shape. Therefore, the swallowing difficulties will disappear shortly after surgery. However, the trachea doesn't return to its patent shape as easily; therefore, after surgery, patients may still have respiratory difficulties.

For transposition of the great vessels, describe the "quick fix" procedure used to keep the newborn alive until more permanent measures can be taken:

The physician may perform a balloon atrial septostomy. This procedure involves tearing a hole in the atrial septum of the newborn, effectively creating an atrial septal defect that would allow the mixing of blood necessary to keep a newborn with transposition of the great vessels alive.

Some patients with 46 chromosomes, including XY sex chromosomes, fail to develop male gonads. Assuming that their SRY gene is normal, provide two possible explanations for this phenomenon:

They may have a mutation in one of their SOX9 genes. In order to develop testes, two functional copies of SOX 9 are necessary (even in the presence of a normal SRY gene). Another alternative is that they have duplication of the DAX-1 gene on their X chromosome. Expression of two or more copies of DAX-1 will inhibit the action of the SRY gene.

What is the traditional surgical treatment for a patient with an atrial septal defect? What more modern, less invasive, surgical procedure is used frequently today?

Traditionally, open-heart surgery places a patch over the defect. Tissue then overgrows the patch. Today, the patch can be put in place by catheter.

What defect will necessitate a patent (open) foramen ovale and/or persistent truncus arteriosus for immediate survival of the newborn?

Transposition of the great vessels

Bifid Ureter

Two ureters traveling from one kidney

What hormone effects the development of the paramesonephric ducts?

anti-müllerian hormone (expressed by males)

Newborns with trisomy 21 (Down's syndrome) are likely to have which heart anomaly?

atrioventricular septal defect

The superior and inferior endocardial cushions of the developing heart fuse together to form the septum intermedium. Which congenital cardiac anomaly results from improper fusion of these endocardial cushions?

atrioventricular septal defect

Which congenital cardiac anomaly results from improper fusion of the endocardial cushions?

atrioventricular septal defect

Early after its formation, the structure from question #2 will attach caudally to which structure?

cloaca (bladder)

Congenital Left to Right Shunt

clubbing of fingers and toes dyspnea (shortness of breath) right ventricular hypertrophy pulmonary edema pulmonary hypertension/Eisenmenger reaction growth failure/problems with feeding

Hypospadias

congenital abnormality in which the male urethral opening is on the undersurface of the penis, instead of at its tip

A primary heart tube that loops to the right instead of the left will result in a condition known as:

dextrocardia

During folding of the heart tube (not embryonic folding), which of the following directions does the atrium move?

dorsally and cranially

In females, what adult organs do these three structures develop into?

genital ridges - ovaries mesonephric ducts - nothing paramesonephric tubules - oviducts, uterus, superior vagina

The primordia of internal reproductive organs consist of the genital ridges, the mesonephric ducts, and the paramesonephric tubules. In males, what adult organs do these three structures develop into?

genital ridges - testes mesonephric ducts - vas deferens paramesonephric tubules - nothing

In females, what adult organs do these three structures develop into?

genital tubercle - clitoris urethral folds/urethral groove - labia minora/vestibule labioscrotal swellings - labia majora

The primordia of external reproductive organs consist of the genital tubercle, the urethral folds/urethral groove, the labioscrotal swellings. In males, what adult organs do these three structures develop into?

genital tubercle - penis urethral folds/urethral groove - urethral tract labioscrotal swellings - scrotum

Which anomaly, because of its nature, means that surgical procedures are palliative, and not completely corrective?

hypoplastic left heart

Phenotypes of a genetic female (46, XX) suffering from Congenital Adrenal Hyperplasia:

lack of testes (no SRY gene) development of uterus and uterine tubes (no MIH) male external genitalia (excess genitalia)

Double superior vena cava is the result of incomplete suppression of which embryonic vessel?

left anterior cardinal vein (become left superior vena cava)

Portions of the mesonephroi regress, while one structure of the mesonephric system remains (at least for some time). What is the name of the portion that remains?

mesonephric ducts

What is the primary defect in AIS?

mutation in testosterone receptors

During our discussion of the development of the intermediate mesoderm into structures of the urogenital system, you learned about three groups of tissues. In the order that they appear during development (and the order we discussed them), they are A. pronephroi B. mesonephroi C. metanephroi What structures in the newborn arise from the pronephroi?

none

Phenotypes of genetic male (46,XY) Androgen Insensitivity Syndrome

normal testosterone/ normal testes lack of uterus or uterine tubes (MIH present) inferior portion of vagina present female external genitalia female brain development *essentially a female, but with no uterus or uterine tubes and testes hidden in the abdomen

4th aortic arch

on left--> aortic arch on right--> proximal part of right subclavian artery

In newborns with pulmonary atresia, what other defect must be present in order for the infant to survive for any length of time after birth (without surgical intervention)?

patent ductus arteriosus (opening between aorta and pulmonary trunk, which allows blood coming from lungs to go to systemic circuit even though it can't get to left ventricle)

Which of the following defects is it impossible to make a prenatal diagnosis for, even with the most sophisticated visualization instruments?

persistent ductus arteriosus (opening b/w aorta and pulmonary trunk)

DiGeorge syndrome is associated with which heart anomaly?

persistent truncus arteriosus

Septum Intermedium

structure that divides the common atrioventricular canal into right and left atrioventricular canals

The fusion of which two structures forms the septum intermedium?

superior and inferior endocardial cushions

To correct transposition of the great vessels, a surgeon can switch the pulmonary artery and aorta. This will connect these vessels up with their appropriate ventricles. However, transposition of the great vessels typically results in anomalous positioning of other important structures. What anomalous structures complicate the arterial switch procedure?

the coronary vessels, which arise from the pulmonary trunk in patients with transposition of the great vessels (picture is normal heart)

Inguinal Hernia

the protrusion of a small loop of bowel through a weak place in the lower abdominal wall or groin (this weak area in the abdominal wall is creates as the testes descend)

What is the general goal of the Glenn and Fontan procedures?

to connect systemic venous return directly to the pulmonary arteries (useful for many difficult cardiac anomalies like tricuspid atresia, double inlet left ventricle, or hypoplastic left heart)

In females, an ectopic ureter will most likely drain into the:

vagina

In the ventricles, the truncoconal swelling is positioned:

ventrally (fusion of the two truncus swellings forms the septum between the aorta and pulmonary trunk)