9.4 - Embryonic Development Issues

Question 1

Anencephaly

Answer 1

Cause
- congenital neural tube defect caused by incomplete brain and skull development
- folic acid deficiency

Patho
- failure of the neuropore to close
Results in:
- incomplete brain and skull formation
- exposed neural tissue
- absence of cerebral hemispheres

Changes
- absent cerebral hemispheres
- meningocel: meninges can protrude through skull

Significance
- still birth, early death

Prevention
- folic acid supplementation

Question 2

Spina Bifida

Answer 2

Cause
- incomplete closure of spinal column
- folic acid deficiency

Patho
- failure of posterior neuropore to close
- exposed spinal cord

Changes
1) SB Occulta - Mild
- associated symptoms: hair tuft
- defect is covered by skin

2) SB Cystica - Severe
- visible cyst on back
- Meningocele: cysts contains meninges or spinal fluid
- Myelomeningocele: cysts contains meninges and neural tissue (can cause paralysis)

Significance
- neurological impairment
- Myelomeningocele can cause paralysis, sensory loss

Prevention
- Folic acid supplementation

Question 3

Cleft Lip and Palate

Answer 3

Cause
- failure of fusion of facial structures
- folic acid deficiency

Patho
- failure of maxillary and medial nasal processes to fuse (gap in upper lip)
- failure of maxilla and nasal septum palatine process (gap in roof of mouth)

Changes
Cleft Lip
1) Incomplete - small gap
2) Complete - gap extends through nostril (affects nasal function)

Cleft Palate
1) Incomplete - partial separation of hard and soft palate
2) Complete - separation affects nasal cavity

Significance
- speech and language difficulty
- feeding difficulty
- teeth alignment problems

Treatment: surgery

Question 4

Tetralogy of Fallot

Answer 4

Cause
- genetics (gene mutations)
- environmental risk factors: child bearer diabetes, infection

Patho
1) Pulmonary Stenosis
- narrowed R ventricle outflow tract = restricted flow to lungs = ↓ oxygenation

2) Ventricular Septal Defect
- hole bw ventricles mixes oxygenated and deoxygenated blood

3) Overriding Aorta
- aorta receives mixed blood = deoxygenated blood enters circulation

4) Right Ventricular Hypertrophy
- increased workload from narrowed pulmonary artery = thickened R ventricle

Changes
- narrowed pulmonary artery (pulmonary stenosis)
- hole in ventricle (VSD)
- overiding aorta
- right ventricular hypertrophy

Significance
- cyanosis - low oxygen = blue discolouration
- tet spells (periods of worsened cyanosis)
- murmur: due to turbulent blood flow in pulmonary stenosis or VSD

Long-term Risk
- R sided heart failure
- arrhythmias

Question 5

Renal Agenesis (Potter Syndrome)

Answer 5

Cause
- genetic mutations
- trisomy 13 and 18

Patho
- failure of ureteric bud to interact with metanephric blastema during kidney development
- ureteric bud fails to form (which halts nephron formation)

Changes
1) Oligohydramnious: bc lack of urine production

2) Pulmonary hypoplasia
- fetus breath amniotic fluid; low amniotic fluid = impaired breathing

Significance
- bilateral RA = fatal
- unilaterl RA = increases risk of hypertension, kidney disease

Question 6

Omphalocele

Answer 6

Cause
- trisomy 13,18,21
- child bearer obesity

Patho
- normally, intestine extend into umbilical cord, and return back to abdomen
- incomplete return to the abdominal cavity = protrusion of organs

Changes
- membrane covered sac containing abdominal organs
Mild: small intestine involvement
Severe: liver and other organs
- sac is located at base of umbilical cord (bottom of stomach)

Risks
- infection and injury to exposed organs
- breathing difficulty to accommodate organs after they are repositioned in abdominal cavity

Treatment: surgery (gradually repositions organs)

Question 7

Gastroschisis

Answer 7

Cause
- unknown

Patho
- occlusion of R umbilical vein = ischemia = necrosis of abdominal wall
- intestines protrude into amniotic cavity
- exposure to amniotic fluid causes inflammation

Changes
- no protective sac: intestine is exposed to amniotic fluid = inflammation and thickened intestinal walls
- instestinal damage causes bowel dysfunction after birth

Significance
- Peel: thickened intestine can impair digestion/reabsorption

Question 8

Hydrops Fetallis

Answer 8

Patho
- fluid builds up in tissues and cavities
- RH - childbearer develops antibodies that attack fetal RBC;s
- bc RBC’s are destroyed, it causes = anemia
- heart tries to compensate = heart failure
- increased cap permeability makes fluid leak into cavities

Changes
- edema, pleural effusion, ascites, pericardial effusion
- severe hemolysis (destruction of RBC’s)

Prevention
- administer Rh immunoglobulin to prevent Rh incompatibility
- blood transfusions for fetal anemia