Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Embryology > Chapter 8: Twins > Flashcards

Chapter 8: Twins Flashcards

1
Q

Twins

A

Giving birth to more than one baby.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Types of twins

A
  1. Dizygotic (fraternal) twins.
  2. Monozygotic (identical) twins.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Dizygotic (fraternal) twins cause

A

Formation of two zygotes by simultaneous ovulation of two oocytes and fertilization by two sperms.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Dizygotic (fraternal) twins incidence

A
  1. Commonest type.
  2. Represents 0.7-1.1% of the total births.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Dizygotic (fraternal) twins features

A
  1. Each embryo implants separately.
  2. Each embryo develops its own amnion, chorion, and placenta.
  3. Offspring are not identical in shape and may be of some or different sex.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Monozygotic (identical) twins cause

A

Splitting of fertilized ovum at variable stages of development.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Monozygotic (identical) twins incidence

A

0.3-0.4% of total births.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Monozygotic (identical) twins features

A
  1. Offspring are identical in shape and sex.
  2. Fetal membranes are variable according to the stage at which splitting occurs.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Stages at which splitting occurs:

A
  1. Splitting of morula.
  2. Splitting of inner cell mass of early blastocyst.
  3. Splitting of the embryonic disc of late blastocyst.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Splitting of morula

A
  1. Morula divides into two morulae which develop into two separate blastocysts.
  2. Each embryo has its own amnion, chorion, and placenta.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Splitting of inner mass of early blastocyst

A
  1. Single blastocyst which has 2 inner cell masses.
  2. Both embryos have common chorion and placenta.
  3. Each embryo has its own amnion.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Splitting of embryonic disc of the late blastocyst

A
  1. Single blastocyst which has 2 embryonic discs.
  2. Both embryos have a common amnion, chorion, and placenta.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Siamese (fused) twins

A

Occurs due to incomplete split of the embryonic disc.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Siamese (fused) twins sites of fusion

A
  1. Craniopagus: head.
  2. Thoracopagus: thorax.
  3. Pygopagus: pelvis.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Success of surgical separation of Siamese twins depends on?

A
  1. Site of fusion.
  2. Organs in common between the twins.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Twin defects

A

Twins may suffer from:
1. Increased incidence of prematurity.
2. Low birth weight.
3. High mortality rate.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Birth defects

A

Structural and/or functional disorders present at birth. They are caused by environmental or genetic factors acting independently or together.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Risky gestational period

A
  1. Embryonic period: most sensitive time (3rd to 8th week).
  2. Fetal period: risk for gross structural defects are decreased, but organ systems may still be affected (9th week to full term).
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Factors responsible for birth defects

A
  1. Environmental factors (teratogens).
  2. Chromosomal abnormalities.
    - Unknown etiology.
    - Multifactorial inheritance.
    - Mutant genes.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Environment factors (teratogens)

A

The effects of teratogens varies according to:
1. Developmental stage at the time of exposure.
2. Dose and duration of exposure of the tertogen.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Teratogens factors

A
  1. Infectious agents.
  2. Radiations.
  3. Drugs and chemicals.
  4. Maternal causes.
  5. Paternal causes.
22
Q

Infectious agents

A
  1. Viruses.
  2. Bacteria.
  3. Parasites.
23
Q

Viruses

A
  1. German measles.
  2. Cytomegalovirus.
  3. Herpes simplex.
  4. Varicella.
  5. HIV (AIDS).
24
Q

Bacteria

A

Syphilis

25
Q

Parasites

A

Toxoplasma

26
Q

Radiation

A

Ionizing radiation: X-ray and gamma rays.

27
Q

Why does radiation has teratogenic effects?

A
  1. They kill rapidly proliferating cells.
  2. They lead to genetic alteration of germ cells with subsequent fetal movements.
28
Q

Drugs and chemicals

A
  1. Most drugs, especially in the first 3 months.
  2. Alcohol and nicotine.
29
Q

Maternal causes

A
  1. The incidence of congenital malformations is 3-4 times higher in the offspring of a diabetic mother.
  2. Iodine deficiency in maternal diet leads to baby cretinism.
  3. Obese mother gives birth to babies with neurological defects.
  4. Pregnant mothers above 40 years old have the higher possibility to give birth to a child suffering from Down syndrome.
  5. Mothers with cyanotic heart disease and those living high altitude may give birth to small sized infants with no gross congenital anomalies.
  6. Hyperthermia (increased body temperature) either caused secondary to bacterial infections or externally as exposure to hot sun or sauna systems affect neurulation leading to anencephaly or spina bifida.
30
Q

Paternal causes

A
  1. Exposure to chemicals and radiation can cause mutation in male germ cells.
  2. Advanced age may lead to chromosomal defects in male gametes with subsequent anomalies in the offspring. Eg. Down syndrome.
31
Q

Chromosomal abnormalities

A
  1. Numerical.
  2. Structural.
32
Q

Numerical chromosomal abnormalities

A

The offspring has abnormal chromosomal number. It could be autosomal or in sex chromosomes.
It is divided into:
1. Autosomal.
2. Sex chromosomes.

33
Q

Autosomal

A
  1. Trisomy 21 (Down syndrome or mongolism).
  2. Trisomy 13 15 17 18.
34
Q

Trisomy 21 (Down syndrome of mongolism)

A

Extra chromosome 21 so the chromosomal number is 45 + XX or XY.

35
Q

Trisomy 21 (Down syndrome of mongolism) cause

A

This occurs due to non disjunction of chromosomes 21 during the 1st meiotic division of the oocyte.

36
Q

Trisomy 21 (Down syndrome of mongolism) percent increase

A

The possibility of a child with Down syndrome increases with the increase in the age of the mother.

37
Q

Trisomy 21 (Down syndrome of mongolism) features

A

Specific facial features with mental retardation.

38
Q

Trisomy 13 15 17 18

A
  1. Less common.
  2. Infant suffers from many congenital anomalies and usually dies by the age of 2 months.
39
Q

Sex chromosomes

A
  1. Klinefelter syndrome.
  2. Turner’s syndrome.
40
Q

Klinefelter syndrome

A
  1. 44 + XXY.
  2. Due to non disjunction of X chromosomes during division of oocyte.
  3. Male child she suffers from gynecomastia and infertility.
41
Q

Turners syndrome

A
  1. 44 + X0.
  2. Due to non disjunction of sex chromosomes during division of either male or female gametes.
  3. A female child suffers from webbed neck and infertility due to agenesis of ovaries.
42
Q

Structural chromosomal abnormalities

A

They result from breaking of a chromosome due to exposure to viruses, radiations, or drugs.
Divided into:
1. Cri-du-chat syndrome.
2. Angelman syndrome.

43
Q

Cri-du-chat syndrome

A

Partial deletion of short arm of C5.
Symptoms:
2. Cat like cry.
3. Microcephaly.
3. Mental retardation.
4. Congenital heart disease.

44
Q

Angelman syndrome

A

Partial deletion of long arm of C15.
Symptoms:
1. Mental retardation.
2. Inability to speak.
3. Poor motor development.
4. Prolonged period of laughter.

45
Q

Prevention of birth defects

A
  1. Supplementation of salt or water supplied with iodine:
    - Mental retardation.
    - Bone deformities resulting from cretinism.
  2. Folate supplementation:
    - Lowers incidence of neural tube defects:
    * spina bifida.
    * anencephaly.
    - Reduces the risk for hyperthermia-induced abnormalities.
  3. Avoidance of alcohol and other drugs.
46
Q

Prenatal diagnosis of fetal malformations

A
  1. Ultrasonography examination.
  2. Maternal serum screening (level of alpha fetal-proteins).
  3. Amniocentesis (genetic analysis of sloughed fetal cells).
  4. Chorionic villus sampling (sample from placenta for genetic analysis).
47
Q

Fetal therapy

A
  1. Fetal transfusion.
  2. Fetal medical treatment.
  3. Fetal surgery.
  4. Stem cell therapy.
  5. Gene therapy.
48
Q

Fetal transfusion

A
  1. In case of fetal anemia produced by maternal antibodies.
  2. Blood transfusion to the fetus.
  3. Ultrasound to guide insertion of needle to umbilical cord vein.
  4. Directly into the fetus.
49
Q

Fetal surgery

A
  1. Open fetal surgery.
  2. Minimal fetoscopic surgery.
  3. Centers with well trained teams and only with no reasonable alternatives.
    - Repairing congenital diaphragmatic hernia.
    - Congenital heart diseases.
    - Neural tube defects.
50
Q

Stem cell therapy

A
  1. Because the fetus doesn’t develop any immunocompetence before the 14th week gestation, it may be possible to transplant tissues or cells before this time without rejection.
  2. Hematopoietic stem cells for treatment of immunodeficiency and hematologist diseases.
51
Q

Gene therapy

A

Experimental technique that uses genes to treat and prevent disease.
In the future, this technique may allow managing a disorder by:
1. Replacing mutant gene that causes disease with a healthy copy of the gene.
2. Inactivating a mutated gene that is functioning improperly.
3. Introducing a new gene into the body to help fight a disease.

Embryology (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions