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Y2 LCRS 1 - RDA > Embryology > Flashcards

Embryology Flashcards

1
Q

What are the 4 cellular processes involved in embryological development?

A
  1. Proliferation
  2. Differentiation
  3. Reorganisation
  4. Apoptosis
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2
Q

What are the key developmental events that occur in the first 2 months of pregnancy?

A

Weeks of Embryonic development = +2 = gestation ages

NOTE:

  • At the end of the embryonic period in week 8 about 90% of the adult anatomical structures have formed
  • Face, urinary, reproductive system and lung cont to develop beyond week 8
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3
Q

How is the notochord formed?

A
  • Week 3: mesodermal cell ingress through the primitive streak to form a notochord
  • The primitive pit extends to form a notochordal canal
  • Floor fuses with underlying endoderm
  • Notochordal cells proliferate and infold to form the notochord
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4
Q

How is the neural tube formed?

A

Neurulation:

  • The developing notochord induces the overlying ectoderm to thicken and form the neural plate
  • The plate elevates to form neural folds which fuse ober the neural groove to form the neural tube
  • Neural tube closes by week 4 (day 22)
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5
Q

What happens when the neural tube fails to close properly?

A

Anecephaly = failure of rostral fusion

Spina bifida = failure of caudal fusion

  • Spinal bifida occulta = small internal defect marked by a patch of hair/ dimples overlying defect
  • Meningocele = membrane bulged out → contains CSF but not neural tissue
  • Myelomeningocele = neural tissue has bulged out → severe defect → derangement of function
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6
Q

How is spina bifida prevented?

A

Folic acid deficiency causes this

  • Folic acid BEFORE pregnancy and in first trimester
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7
Q

How does the face develop?

A

2 halves of face develop separately

  • Nasal pits begin where the eyes will end up at and the eyes develop on the lateral sides of head
  • Eyes + nose begin on linear lvel
  • Between wk5 and 10 PF, nose + eyes migrate centrally via:-
    • Tissue btwn nasal pits apoptose = cleft formation
    • Instead of new cell proliferation to fill up cleft, existing cells migrate centrally and pulls along with it the eyes + nose
  • Process continues until 2 halves of face fuse
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8
Q

How may a cleft palate/lip arise?

A
  • Grooves formed in midline
  • Masses of tissue migrate from lateral side of face in towards midline to fill in these grooves
  • Failure to fill these grooves leads to cleft palate/lip
  • Upper lip consists of 2 grooves –> asymmetric defect -
  • Cleft palate =malfusion of palate (roof of mouth)
  • Cleft lip = malfusion of the upper lip ONLY!!
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9
Q

How does the urinary system develop?

A

Development of the urinary organs starts at the urogenital ridge (mesoderm)

Nephretic duct develops and joins with the nephrogenic cords > successive phases of kidney development

  • Pronephros ismost immature form
  • Mesonephros, an intermediate phase
  • Metanephros is most developed > metanephric mesoderm > definitive adult kidney (wk 5)

Week 6-8: start down by ureters + ascend towards adrenal glands

  • Ureters extend + retain kidney bladder connections
  • In contrast the kidenys form new connections with the developing arterial system as they move so renal arteries breakdown and reform
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10
Q

When do the kidneys ascend?

A

Week 6-9 PF

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11
Q

What happens as the kidneys ascend? (X)

A
  • Need to rise up to lumbar region
  • Don’t drag BVs with them
  • Send out new and more cranial branches
  • Caudal branches regress
  • Mesonephros degenerates
  • Gonads descend
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12
Q

What complications can occur during renal development?

A
  1. Pelvic kidney (doesn’t ascend to below adrenal gland)
  2. Horseshoe kidney - fusion of separately developing kidneys below inferior mesenteric artery - also X descend
  3. Retention of extra artery (isn’t broken down) - may obstruct ureter –> enlargement renal pelvis
  4. Renal agenesis (bilateral = Potter’s syndrome due to low amniotic fluid the ureteric buds don’t grow)
  5. Abnormal ureter/shaped kidneys
  6. Bladder exstrophy - problem w/cloaca - abdominal wall fails to cover bladder - abnormal distance btwn scrotum + penis
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13
Q

What layer of cells does the bladder develop from? (X)

A

Mostly endoderm Trigone is mesodermal (mesonephric duct) - Trigone signals filling of bladder

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14
Q

How does the heart develop?

A

Week 3 - heart at midline - cardiogenic cells develop in U pattern outside embryo proper

Week 4 - heart tubes fuse

Day 23 - heart loops - atria loop posteriorly and to the right so they end up more cranial to ventricles

Day 28 - heart septation - spiralling occurs

Week 7 - outflow tracts divide

  • Vascular connections maintained, so major arteries connected to ventricles + veins to atria
  • Valves develop –> unidirectionally flow ensured
  • Foramen ovale between atria
  • Main artery from RV connected to aorta by ductus arteriosus
    • these holes divert blood away from the lungs to the rest of the body
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15
Q

How do cardiac abnormalities occur?

A
    • Problem w/heart looping day 23 = transposition of great arteries (aorta + PA swapped)
    • Problem with heart septation day 28 = ventricular septal defect - deoxygenated blood into LV, patent foramen ovale
    • Problem w/outflow tracts dividing wk 7 = pulmonary stenosis, truncus arteriosus
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16
Q

What is the Tetralogy of Fallot?

A

Type of congenital heart disease

  1. Pulmonary stenosis (thickened, narrow pulmonary outflow tract)
  2. Thickened RV wall
  3. Ventricular septal defect
  4. Aorta overides septal defect
17
Q

How do the lungs develop?

A
  1. Begins during 1st TM, not completed until after delivery
  2. Surfactant produced from 25 weeks PF + gradually increased during 3rd TM
  3. 5 stages of development (wks gestational age, since LMP)
    1. Week 0-6 = embryonic
    2. Week 6-16 = pseudoglandular
    3. Week 16-28 = canalicular
    4. Week 28-36 = saccular
    5. Week 36-birth = alveolar
18
Q

What happens in the embryonic stage of lung development?

A

0-6 weeks gestational age:

Laryngotracheal groove folds into tube

Tube divides into oesophagus + lung buds

Buds grow into pleural passages + divide into lobes

19
Q

What happens in the pseudoglandular stage of lung development?

A

6-16 weeks gestational age:

Trachiobronchial tree forms as branching tubules resemble exocrine gland

20
Q

What happens in the canalicular stage of lung development?

A

16-28 weeks gestational age:

Ascinar units form terminal bronchioles and divide into resp bronchioles

Capillaries approximate to potential air spaces but have little contact

Type 1 and 2 alveolar cells + surfactant starts being made

21
Q

What happens in the saccular stage of lung development?

A

28-36 weeks gestational age:

Barrier thins

Increased maturation of surfactant

22
Q

What happens in the alveolar stage of lung development?

A

36 weeks gestational age-birth:

Primitive alveoli mature

23
Q

Which cells make surfactant?

A

Type 2 alveolar cells

24
Q

What is the role of surfactant?

A

Reduces surface tension Produces constituent apoproteins

25
Q

What causes respiratory distress syndrome?

A

Low surfactant

26
Q

How can you increase surfactant production?

A

Injecting glucocorticoids

27
Q

Where do the gonads develop from?

A

Intermediate mesoderm within urogenital ridges

28
Q

Which strucutures give rise to the male and ffemale genital ducts respectively?

A
  1. Paired mesonephric ducts give rise to the Wolfian system in males
  2. Paired Paramesonephric ducts gives rise to the Mullerian system in females
29
Q

When do the genital ducts start to differentiate?

A

Week 7 PF

30
Q

What does male sex rely on?

A

Activity of SRY protein

31
Q

Why does the mesonephric duct break down in females?

A

Gives rise to testes

32
Q

What are the main developmental abnormalities of the reproductive system?

A

Female: - Congenital adrenal hyperplasia - mutation in CYP21A2

Male: - Androgen insensitivity syndrome - mutant androgen R - Result of inability to produce testosterone/anti-Mullerian hormone OR inability of target tissues to respond (Rs)

33
Q

What causes regression of the paramesonephric female ducts?

A

Testosterione ****Anti-mullerian hormone DHT

34
Q

How do the gonads and reproductive tract develop?

A
  • Gonads arise from intermediate mesoderm within urogenital ridges of embryo - Genital ducts arise from paired mesonephric + paramesonephric ducts - Mesonephric ducts give rise to MALE genital ducts (Wolffian system) - Paramesonephric ducts give rise to FEMALE genital ducts (Mullerian system) - Gonads and RTs are indifferent up until 7 weeks of development - Differentiation is influenced largely by presence or absence of SRY (on Y chromosome) - If SRY+, then development proceeds along male path - If SRY-, then development proceeds along female path

Y2 LCRS 1 - RDA (11 decks)

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