Periods Of Development

Question 0

Teratogen susceptibility in early development

Answer 0

0-2 weeks
Not sensitive usually
High rates of lethality may occur

Question 1

What are the three periods of development and their description

Answer 1

Early development-fertilization to beginning of 3rd week
Embryonic period-weeks 3-8
Fetal period-beginning of week 9 to birth

Question 2

Teratogen susceptibility in embryonic period

Answer 2

3-8 weeks
Periods of greatest sensitivity
Each organ will have a period of peak sensitivity

Question 3

Teratogen susceptibility in fetal period

Answer 3

9-38 weeks
Decreasing sensitivity
Period of functional maturation

Question 4

What is a congenital anomaly?

Answer 4

Abnormalities that are present at birth
Can be detected by ultrasound, readily visible at birth, detected inadvertently during life or not detected until after death (autopsy or gross lab)

Question 5

Which developmental period is the greatest risk for malformation

Answer 5

Embryonic development

Question 6

Crown-rump length CRL

Answer 6

Measure from the vertex of the head to the buttocks

Question 7

Early development includes:

Answer 7

Fertilization and implantation
Proliferation of cells and gastrulation
Formation of the placenta
Determination of the body axes

Question 8

Embryonic period includes:

Answer 8

All organs and specific body parts form

Most organ systems are highly susceptible to injury during this period

Question 9

Fetal period includes:

Answer 9

9 weeks to birth
Increase in length is uniform
Increase in weight is not uniform but greatest prior to birth
Tissue and organelles are less susceptible to injury
Brain, eyes, palate and teeth most susceptible to injury
External genitalia as well

Question 10

Four clinically significant types of congenital abnormalities

Answer 10

Malformations
Disruptions
Deformations
Dysplasia

Question 11

Define malformations

Answer 11

Occur during organogenesis in the embryonic period; result in abnormal structure
20% of infant deaths attributed to this congenital anomaly
Most originate in the embryonic period

Anatomical variations eg. Three headed biceps

Question 12

Define disruptions

Answer 12

Result from external influences that cause alterations of completely formed structures or organs

Question 13

Define deformations

Answer 13

Abnormal structure resulting from mechanical forces

Amniotic bands

Question 14

Define dysplasia

Answer 14

Abnormal organization of cells into tissue

Sacrococcygeal teratoma

Question 15

Causes of congenital anomalies

Answer 15

Genetic (Down’s syndrome.) 28%
Environmental agents (virus, ethanol) 3-4%
Multifactorial 20-25%
Unknown etiology 40-45%

Question 16

Agenesis

Answer 16

Absence of an organ

Question 17

Aplasia

Answer 17

Cells to form an organ never formed (migrating cells)

Question 18

Association

Answer 18

Anomalies occurring together without a determined cause

Question 19

Atresia

Answer 19

Absence of an opening or lumen (in the gastrointestinal tract)

Question 20

Hyperplasia

Answer 20

Overgrowth of an organ

Question 21

Hypoplasia

Answer 21

Underdevelopment of an organ

Question 22

Syndrome

Answer 22

A group of anomalies, occurring together with a common cause

Question 23

Teratogen

Answer 23

Substance affecting migration, proliferation, or interaction of cells; results in congenital abnormalities

Question 24

Thalidomide

Answer 24

Sedative drug produced congenital abnormalities, hands and feet develop on the torso, no arms or legs

Question 25

Teratology, dysmorphology

Answer 25

Study of birth defects, congenital anomalies and congenital malformations

Question 26

Minor anomalies

Answer 26

Occur in 15% of births, not detrimental to health 1 anomaly =3% chance of major malformation 2 anomalies =10% chance of major malformation 3 anomalies = 20% chance of major malformation

Question 27

Factors that determine capacity of teratogen to produce birth defect

Answer 27

Genotype of conceptus- way genotype interacts with environment Developmental stage at which time exposure occurs Dose and duration of exposure Teratogens acting in specific ways (mechanisms)

Question 28

Ability of a cell or be induced

Answer 28

Competence to respond

Question 29

Paracrine interactions

Answer 29

Signal diffuses short distance to induce a cell

Question 30

Juxtacrine interactions

Answer 30

Do not involve diffusable proteins | Protein on one cell interacts with the receptor on another cell

Question 31

Signal transduction pathways

Answer 31

Patterns of expression dictate where parts develop Determination of anterior vs posterior development Primordial germ cells signal surrounding body wall to differentiate into primitive sex cords Males- Sertoli cells Females- follicular cells