Embryonic Development Issues

This set of flashcards covers vocabulary related to embryonic developmental issues, focusing on congenital defects and their biological underpinnings.

Anencephaly

A severe neural tube defect resulting from failure of the cranial neuropore to close.

1. Etiology

   • Multifactorial, significantly linked to low maternal levels of folic acid.

2. Structural Changes

   • Absence of the major portion of the brain, skullcap, and scalp.

3. Symptoms

   • Absence of consciousness.

   • Physical absence of the cranial vault.

   • Usually results in stillbirth or death within hours/days.

4. Treatment

   • No known cure; management is strictly palliative and supportive care.

Spina Bifida

A congenital defect where the spinal column fails to close properly.

1. Etiology
   • Failure of the caudal neural tube to close; risk factors include folic acid deficiency and certain medications (e.g., valproate).
2. Structural Changes
   • Incomplete fusion of vertebral arches; may involve herniation of meninges (meningocele) or meninges and spinal cord (myelomeningocele).
3. Symptoms
   • Lower limb paralysis.
   • Sensory loss and bladder/bowel dysfunction.
   • Hydrocephalus in many cases.
4. Treatment
   • Fetal surgery (in utero) or postnatal surgical closure.
   • Long-term physical and occupational therapy.

Cleft Lip

A common facial malformation caused by the failure of fusion of embryonic structures.

1. Etiology
   • Failure of the maxillary prominence to fuse with the medial nasal prominence.
2. Structural Changes
   • A visible split or opening in the upper lip that can extend into the nose.
3. Symptoms
   • Difficulty with suction during feeding.
   • Aesthetic concerns.
4. Treatment
   • Surgical repair (cheiloplasty), typically performed between $3$ to $6$ months of age.

Cleft Palate

A congenital opening in the roof of the mouth.

1. Etiology
   • Failure of the palantine shelves to fuse with each other or the primary palate.
2. Structural Changes
   • A fissure in the hard and/or soft palate, potentially connecting the oral and nasal cavities.
3. Symptoms
   • Severe feeding difficulties.
   • Frequent middle ear infections (otitis media).
   • Speech and language delays.
4. Treatment
   • Surgical reconstruction (palatoplasty) usually between $6$ to $12$ months of age.
   • Multidisciplinary care involving speech therapy.

Tetralogy of Fallot

A complex congenital heart condition characterized by four specific anatomical abnormalities pulmonary stenosis, ventricular septal defect, overriding aorta, right ventricular hypertrophy

1. Etiology

   • Anteroposterior deviation of the infundibular septum.

2. Structural Changes

   • Ventricular septal defect ($VSD$).

   • Pulmonary stenosis.

   • Overriding aorta.

   • Right ventricular hypertrophy.

3. Symptoms

   • Cyanosis ("Blue Baby" syndrome).

   • "Tet spells" (sudden drop in blood oxygen levels).

   • Fingernail clubbing.

4. Treatment

   • Surgical repair (intracardiac repair) to close the $VSD$ and relieve pulmonary obstruction.

Renal Agenesis

The absence of one or both kidneys at birth.

1. Etiology
   • Failure of the ureteric bud to develop or reach the metanephric blastema.
2. Structural Changes
   • Missing kidney tissue; Bilateral cases lead to Potter Sequence due to lack of amniotic fluid.
3. Symptoms
   • Unilateral: Often asymptomatic, found incidentally.
   • Bilateral: Severe oligohydramnios, pulmonary hypoplasia, and characteristic facial features.
4. Treatment
   • Unilateral: Monitoring of the remaining kidney.
   • Bilateral: Historically fatal; experimental dialysis and transplant are rare options.

Omphalocele

A midline abdominal wall defect where organs remain outside the body.

1. Etiology
   • Failure of the midgut to return to the abdominal cavity after physiological herniation during week $10$.
2. Structural Changes
   • Abdominal contents (intestines, liver) protrude through the umbilical ring, covered by a peritoneal sac.
3. Symptoms
   • Visible sac containing internal organs at the base of the umbilical cord.
4. Treatment
   • Surgical closure (staged or immediate depending on size).
   • Protection of the sac from rupture and infection.

Gastroschisis

An abdominal wall defect lateral to the umbilicus.

1. Etiology
   • Likely due to a vascular accident involving the omphalomesenteric artery or a structural weakness in the abdominal wall.
2. Structural Changes
   • Protrusion of bowel through a full-thickness defect, usually to the right of the umbilical cord; no covering sac.
3. Symptoms
   • Exposed, often inflamed intestines due to contact with amniotic fluid.
4. Treatment
   • Urgent surgical reduction and closure or use of a "silo" for gradual reduction.

Hydrops Fetalis

Excessive fluid accumulation in fetal tissues and serous cavities.

1. Etiology
   • Immune ($Rh$ isoimmunization) or Non-immune (cardiac failure, chromosomal abnormalities like Turner Syndrome, or alpha-thalassemia).
2. Structural Changes
   • Accumulation of fluid in at least two compartments (ascites, pleural effusion, pericardial effusion, or skin edema).
3. Symptoms
   • Severe generalized swelling (anasarca).
   • Heart failure and hepatosplenomegaly.
4. Treatment
   • Intrauterine blood transfusions for immune causes.
   • Treatment of maternal infections or fetal arrhythmias where applicable.