Embryology 1

Question 1

Ovulation and fertilization occur how many days after the first day of menstruation?

Answer 1

14 days

Question 2

How is a due date calculated?

Answer 2

adding 280 days (40 weeks) to the first day of the last menstrual period

Question 3

What is the difference between postconception age and postmenstrual age?

Answer 3

2 weeks

Question 4

What are the 9 major stages of development?

Answer 4

gametogenesis; fertilization; cleavage; gastrulation; neurulation; formation of body plan; organogenesis; prenatal organ maturation; postnatal maturation

Question 5

Define conceptus.

Answer 5

term that refers to all stages of the organism that derive from the zygote

Question 6

When does cleavage begin?

Answer 6

~24 hours after fertilization

Question 7

What is the major difference between the 16-cell stage and the 32-cell stage?

Answer 7

16-cell stage has trophoblast and embryoblast, but 32-cell stage results in formation of blastocytic cavity

Question 8

Gastrulation occurs in what week?

Answer 8

3

Question 9

What happens in gastrulation?

Answer 9

cells that form embryoblast proliferate and change position relative to each other, giving rise to 3 distinct layers: endoderm, mesoderm, ectoderm

Question 10

When are the three axes of the embryo established?

Answer 10

by the end of gastrulation

Question 11

What are the three axes of the embryo?

Answer 11

dorsal-ventral; cranial-caudal; medial-lateral

Question 12

Neurulation occurs in what week?

Answer 12

3 and 4

Question 13

What happens in neurulation?

Answer 13

process in which early CNS is developed

Question 14

Which germ layer is responsible for neurulation?

Answer 14

ectoderm — part of it specializes into neuroectoderm, which becomes, neural tube, which becomes brain + spinal cord

Question 15

What is another term for formation of the body plan?

Answer 15

embryonic folding

Question 16

When does embryonic folding occur?

Answer 16

week 4

Question 17

What happens in embryonic folding?

Answer 17

2D embryo folds and becomes cylindrical

Question 18

Organogenesis occurs in which weeks?

Answer 18

4-8

Question 19

Prenatal organ maturation occurs in which weeks?

Answer 19

9-38

Question 20

In what week does the heart start beating?

Answer 20

4

Question 21

When are digits defined?

Answer 21

week 6

Question 22

The stages of prenatal development are organized into what periods?

Answer 22

3 periods — pre-embryonic period; embryonic period; fetal period

Question 23

The pre-embryonic period includes what key events?

Answer 23

cleavage (weeks 1-2); implantation (week 2)

Question 24

The embryonic period includes what key events?

Answer 24

gastrulation (week 3); neurulation (weeks 3-4); embryonic folding (week 4); organogenesis (weeks 4-8)

Question 25

The fetal period includes what key events?

Answer 25

prenatal organ maturation (weeks 9-38)

Question 26

What is a synonym for the cranial pole?

Answer 26

rostral pole

Question 27

Describe the degree of potency up until the 16-cell stage.

Answer 27

totipotent

Question 28

Describe the degree of potency of the embryoblast.

Answer 28

pluripotent - can become any of the 3 germ layers

Question 29

What is the difference between paracrine and juxatacrine signaling?

Answer 29

juxtacrine signaling requires direct contact between the two cells in question

Question 30

What is teratology?

Answer 30

study of congenital abnormalities and abnormal formations

Question 31

What is the definition of a minor congenital anomaly?

Answer 31

benign (don't affect health or social life) and occur in less than 4% of people

Question 32

Define malformation.

Answer 32

morphologic defect of organ or large area of body caused by genetic/intrinsic factors

Question 33

Define disruption.

Answer 33

morphologic defect of organ or large area of body caused by external factors (teratogens)

Question 34

What are the 3 types of multiple anomalies?

Answer 34

sequence; syndrome; association

Question 35

Define sequence.

Answer 35

when single developmental defect results in chain of secondary or tertiary defects

Question 36

Define syndrome

Answer 36

recognized and well-characterized constellation of major and minor anomalies due to single underlying cause

Question 37

Define association.

Answer 37

group of anomalies that occur frequently together but don't have a unified underlying etiology

Question 38

Define aneuploidy.

Answer 38

deviation from normal number of chromosomes

Question 39

What is the common name for trisomy 21?

Answer 39

Down syndrome

Question 40

What is the common name for trisomy 18?

Answer 40

Edwards syndrome

Question 41

What is the common name for trisomy 13?

Answer 41

Patau syndrome

Question 42

Which of the trisomies is most lethal?

Answer 42

Patau syndrome — life expectancy 2-3 days

Question 43

What are the characteristics of 47 XXX? (3)

Answer 43

normal in appearance; usually fertile; 1/5 are mildly mentally deficient

Question 44

What are the characteristics of 47 XXY? (4)

Answer 44

Klinefelter syndrome — small testes; infertile; mental deficiency; tall with long lower limbs

Question 45

What are the characteristics of 47 XYY? (3)

Answer 45

normal in appearance; tall; aggressive