Exam 2 Flashcards
Stages of Embryonic Development
Pre-Embryonic
Embryonic
Fetal
Pre-Embryonic Stage (duration; key developments)
Duration: Conception - Week 3
Key Developments Zygote implants on uterine wall with 3 layers Endoderm Mesoderm Ectoderm
What does the endoderm of the zygote develop into
Respiratory system
Digestive system
Liver
Pancreas
What does the mesoderm of the zygote develop into
Skeleton Connective tissue Cartilage Muscles Circulatory system Lymph system Reproductive system Urinary system
What does the ectoderm of the zygote develop into
Brain
spinal cord
Nervous system
Outer body parts (hair, skin, nails)
Embryonic stage (duration, key developments)
Duration: Weeks 4-8
Developments
Rapid developments –> all basic organs are established by the end of this stage
** Most vulnerable period to any factor that may cause congenital anomalies ** (i.e. alcohol, tobacco)
Fetal stage (duration, key developments for each trimester)
Duration: Week 9-Birth
By 12 weeks gestation (end of T1)
- Some reflexes* present
- Fetal heartbeat can be heard by Doppler (between 10-12 weeks)
- Sex* is distinguishable by appearance
- Kidney* secretions begin
By 24 weeks gestation (end of T2)
- fetal heart tones*
- Lung surfactant* produced (but alveoli not yet formed)
- Liver & pancreas* functioning
- Sleep-wake patterns* established
- Eyelids open*
- Hair forms*
By 40 weeks gestation (end of T3/pregnancy)
- Lung alveoli are formed and considered mature
- testes descend
- subcutaneous fat is deposited
Steps of conception
- ovum (egg) released from ovary and travels down fallopian tube
- sperm meets the ovum at the outer most portion of the fallopian tube = fertilization
- when sperm penetrates ovum, pregancy begins and ovum becomes a zygote
Placenta (what is it, when it forms, functions)
The placenta is the interface/pass-through between the mom and fetus
Begins forming at end of 2nd week
Functions
- supplies nutrients and oxygen
- removes waste products from the fetus to be excreted by the mom
- protects baby from mom’s immune attacks
- produces hormones that mature into fetal organs
Placental hormones & functions
- hCG
- “pregnancy” hormone; the hormone tested for in urine pregnancy tests
- functions: produces progesterone to maintain the uterine lining rather than shedding it
- 2 tests: quantitative (results with amount of hCG to dtmn gestation) and qualitative (yes or no pregnant)
- hPL
- Manages mom and fetus metabolism
- Develops breasts for lactation
- Lowers mom’s insulin sensitivity to increase the number of nutrients available for the fetus
- Estrogen
- Develops breasts, uterus and external genitalia
- Stimulates myometrial contractions during labor
- Progesterone
- Maintains endometrial lining
- Decreases uterine contractility
- Stimulates mom’s metabolism and breast development
- Provides early fetal nourishment during conception phase
- Relaxin
- Maintains the pregnancy
- Softens the cervix before birth
Umbilical cord (development, formed from, functions, contents, size)
Develops with placenta ~end of 2nd week
Formed from amnion (innermost layer of embryo enclosure)
Function: lifeline between mom and embryo
Contents (AVA)
- 1 large vein
- 2 large arteries
- Wharton’s jelly within to prevent compression of blood vessels
Average size
- Length: 22-in
- Width: 1-in
Amniotic fluid (composition, functions)
Fluid surrounding baby in the uterus
Composition = mom’s blood + baby’s urine
- amount of amniotic fluid increases as pregnancy progresses
- ~1L at full term
Functions
- Helps maintain body temp for fetus
- Permits symmetric growth & development
- Cushions the fetus
- Prevents umbilical cord compression
- Promotes fetal movement to enhances musculoskeletal development
Fetal circulation (purpose) and fetal shunts
Fetal lungs are not fully developed so shunting the oxygenated blood from mom away from the lungs and directly to the systemic circulation helps to provide adequate oxygenation in utero
Ductus venosus
- Connects umbilical vein to fetus’ inferior vena cava
Ductus arteriosus
- Connects the fetus’ main pulmonary artery to the aorta
Foramen ovale
- An anatomic opening between the fetus’ right and left atrium
Human genome project (goal)
an international effort to map, sequence and determine the function of all human genes to allow for early detection of anomalies
Genome determines what?
Genome = a person’s genetic blueprint
Determines genotype and phenotype
Genotype
Genes inherited from parents
Phenotype
the observed outward characteristics of the genotype and its interactions with the environment
Genes (definition, makeup, function)
Genes = individual units of heredity of all traits
Made of long segments of DNA that occupy specific locations on a chromosome
Function to determine a particular characteristic of an organism
Karyotype
a pictorial analysis of the number, form and size of chromosomes
22 pairs of autosomes with 1 pair of sex chromosomes
Chromosomes are numbered from largest to smallest (1-22) with sex chromosomes designated by X and Y
XX = female, XY = male
Types of Mendelian/Monogenic Disorders
Autosomal dominant Autosomal recessive X-linked inheritance -- X-linked recessive -- X-linked dominant
Define the following Allele Phenotype Homozygous Heterozygous
Allele - any variations that exist for a gene
Phenotype - the outward characteristics of a gene
Homozygous - inherited genes from mom and dad are the same allele
Heterozygous - different alleles are inherited from parents and the dominant allele is the phenotype
Autosomal dominant disorders (define, chances of impacted offspring, common disorders)
A single gene in a heterozygous state produces the phenotype
If a normal mom and affected dad produce offspring…
- 50% chance unaffected offspring
- 50% chance of heterozygous offspring with disordered phenotype
Common disorders
- Huntington’s
- Polycystic Kidney Disease
Autosomal recessive disorders (define, chances of impacted offspring, common disorders)
2 copies of affected genes in a homozygous state are needed to cause the disorder
Both parents must be heterozygous carriers to produce affected children
If both parents are heterozygous carriers…
- 25% chance of a homozygous “normal” child
- 50% chance of heterozygous carriers
- 25% chance of heterozygous affected genotype –> disordered phenotype
Common disorders
- Cystic Fibrosis
- Phenylketonuria
- Tay-Sachs
- Sickle cell disease
X-Linked Recessive Disorders (define, chances of impacted offspring, common disorders)
Disorders are associated with an abnormal gene on the X chromosome
- Since males have only 1 X chromosome, they are more likely to be affected
– males do not pass along their X
chromosomes, these always come
from mom
- Since females have 2 X chromosomes, they can have hetero- or homozygous chromosomes –> similar to autosomal recessive inheritance
If mom is a carrier and dad has a normal X chromosome…
- 25% chance of normal male
- 25% chance of normal female
- 25% chance of carrier female
- 25% chance of affected male
Common disorders
- Hemophilia
- Color blindness
- DMD
X-linked dominance (define, chances of impacted offspring, Common disorders)
Rare disorders in which dad has an abnormal X OR mom has at least 1 abnormal X
If dad has affected X –> all females have the condition and NO MALES have the condition
If mom has affected X –> 50% chance female offspring have condition and 50% chance male offspring have condition
Common disorders
- Fragile X Syndrome
Genetic evaluation and counseling (when is it most effective to discuss; who may benefit most from it?)
Most ideal time to discuss genetic counseling is pre-conception
Those who may benefit most…
- Mom’s 35+ yo when baby is born
- Dads 50+ yo
- Incestual relationships
- Exposure to drugs, medications, radiations, chemicals, or infection
- Teratogen exposure or risk
- Concerns about genetic defects that occur frequently in ethnic or racial group (i.e. Black persons are more at risk for sickle cell anemia)
Alpha-fetoprotein test (description, indication and timing)
Description
- a prenatal test drawn from mom’s blood to evaluate plasma protein that is produced by the fetus and crosses from amniotic sac into mom’s blood)
Indications of increased levels
- Neural tube defects
- Turner syndrome
- Tetralogy of Fallot
- Multiple Gestation
Indications of decreased levels
- Down syndrome
- Trisomy 18
Timing
- Performed between 15-18 weeks gestation
Chorionic villus sampling (description, complications, indications and timing)
Description = INVASIVE
- a prenatal test in which a small tissue portion of the fetal side of the placenta is removed to test the fetal genetic makeup
Complications
- Riskier px d/t testing in utero
- Severe transverse limb defects
- Spontaneous pregnancy loss
Indications
- Fetal karyotyping
- detects …
- sickle cell anemia
- Phenylketonuria
- Down syndrome
- DMD
Timing
- performed between 10-12 weeks gestation
- Results available in < 1 week
Nursing Roles & Responsibilities during Genetic Counseling
- Take a family history
- Answer family questions and concerns
- Discuss costs, benefits and risks of using health insurance, and note potential risk of discrimination d/t genetic testing results
- Understand ethical, legal and social issues
- PRIVACY and CONFIDENTIALITY
- Monitor family’s emotional reactions
- Offer emotional support
- Referrals to support groups prn
Preconception care goals
- promote the health and well-being of a woman and her partner before pregnancy
- identify and modify biomedical, behavioral and social risks to a woman’s health or pregnancy outcome
- CDC guidelines (10)
1. each couple should be encouraged to have a reproductive life plan
2. increase public awareness of the importance of preconception health behaviors and care
3. provide preconception risk assessments and health promotion activities at all primary care visits for women of childbearing age
4. intervene and follow-up for families with identified risks
5. provide interconception care by offering additional interventions to women who have had a previous pregnancy with an adverse outcome
6. prepregnancy checkups for persons planning pregnancy
7. increase health insurance coverage for women and couples with low incomes
8. integrate preconception health into public health programs
9. increase EBP to improve preconception care
10. monitor improvements in preconception care
What are key components to address in preconception care
- Immunization status of mom
- Underlying medical conditions
- Reproductive health practices
- Sexuality and sexual practices
- Nutrition
- Lifestyle practices
- Psychosocial issues
- Medication and drug/alcohol use
- Support systems
