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Developmental Anatomy IP3 > DA3 - Principles of Teratology > Flashcards

DA3 - Principles of Teratology Flashcards

1
Q

Teratology

A

Study of abnormal development

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2
Q

Teratogenesis

A

Study of abnormal mechanisms of development

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3
Q

Teratogen

A

Any agent that induces defects during development (radiation, infectious agents, drugs, environmental chemicals)

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4
Q

Congenital abnormality

A

any structural, functional, metabolic and behavioral disorder present at birth

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5
Q

Synonyms of congentical abnormality:

A

Anomaly, malformation, maldevelopment, birth defect

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6
Q

Disruptions vs. Deformations

A

Disruption: alteration of formed structures from destructive processes

Deformations: due to mechanical forces

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7
Q

Congenital abnormality facts:

A
  • Caused by genetic or environment factors (usually a complex interaction of both)
  • Incidence: poorly reported in domestic animals (vs. humans)
  • Most are present at birth, others become obvious shortly after birth or later as the orgnaism matures
  • May be structural or functional (absence of an organ vs. absence or defective enzymes)
  • Show different degrees of severity
  • May affect any body structure (internal and external)
  • May occur as single or multiple conditions (syndrome)
  • Some are species-specific or breed-specific (teratogens)
  • some are gender specific
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8
Q

Syndrome

A

Multiple defects that have a specific common cause

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9
Q

Four maifestations of congenital anomalies

A
  • Death
  • Malformation
  • Growth retardation
  • Functional defect
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10
Q

Critical periods to abnormal development: Stage of development

A

Most critical determining factor

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11
Q

Critical periods to abnormal development: stage of pre-differentiation (Before organogenesis)

A

Effects

  • Lethal - due to cytotoxic effect on embryonic cells
  • None - embryonic cells are unresponsive
  • The all or none rule
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12
Q

Critical periods to abnormal development: stage of differentiation

A

The stage of maximum susceptibility for structural abnormalities

  • Effects - usually reflect upon a particular organ
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13
Q

Critical periods to abnormal development: stage of advanced morphogenesis

A

Susptibility declines as organogenesis advances

  • effects: mostly functional (often hereditary)
  • Some structures have more than one critical stage (palate)
  • General rule: the earlier the insult, the more severe the consequences (eg. notochord –> CNS)
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14
Q

Causes of abnormal development: Embryo genotype

A
  • Susceptibility to teratogens - depends upon ebryo genotype and its interaction with adverse environments (some teratogens have species-preference)
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15
Q

Causes of abnormal development: maternal conditions

A
  • Genotype, nutrition, metabolic/organic diseases, exposure to toxic compounds
  • Maternal supporting provisions can override zygote genotype
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16
Q

Abonrmal genes: mutations

A
  • Occur by substitution, insertion, or deletion of bases
  • Impact on animal - depends on the importance the the degree of alteration of final product
  • Their incidence - increases with inbreeding because inbreeding reduces genetic variance and increases transmission of deleterious genes
17
Q

Abnormal Chromosomes

A

Responsible for many defects and abortions

  • Involve both, sex and somatic chromosomes
  • Due to either abnormal number or abnormal structure
  • Incidence in domestic animals - rare (or unreported?)
  • Most are due to non-disjunction of chromosomes
  • In most cases embryo is spontaneously aborted
  • Phenotyping alterations - usually expressed as a syndrome
18
Q

Klinefelter Syndrome

A
  • Trisomy of sex chromosome - XXY karyotype
  • Clinical features are seen only in males, detected at puberty: phenotypic male, gonadal dysgenesis, infertility
    • Example: tortoise-shell (calico) male cat –> calico hair pattern is sex linked
  • Is reported in all species
  • Is the most common sex chromosome abnormality
19
Q

Turner’s Syndrome

A
  • Monosomy of sex chromosomes in female - XO karyotype
  • Clinical features: phenotypic female, gonadal dysgenesis, infertility
  • Reported in all species (most prevalent in pig, horse, cat)
  • YO karyotype = lethal
20
Q

Environmental Facotrs: Physical Factors

A
  • Potent teratogens in all species
  • Response: dose-dependent
  • Avoid exposure of pregantn animals to radiation!!!
21
Q

Environmental Facotrs: Chemical Factors

A
  • Many therapeutic drugs: potential teratogens and carcinogens
  • Effects depend on dosage and chemical structure
  • Use cytotoxic drugs cautiously in pregnant animals!!!
22
Q

Environmental Facotrs - Biological Factors

A

Biological Factors: Infectious agent

  • Some cross placenta infecting embryo (some are lethal)
  • Produce multiple defects especially in early developmental stages
  • Investigate the effects of live-vaccines given to pregnant animals!
23
Q

Environmental Factors - Plants

A
  • Many plants contain toxic and teratogenic compounds
  • Most commonly affected structure - appendicular skeleton
24
Q

Description of altered morphogenic event denotes ….

A

the way in which defective development departs from normal

25
Q

Classification: Developmental failure

A
  • Agenesis or aplasia
  • Causes: absence of primordial tissue or abnormal inductive tissue interaction
  • Example: acardia (heart), amelia (limbs), kidney agenesis
26
Q

Agenesis

A

Failure of development

27
Q

Amelia

A

Congenital absence of limbs

28
Q

Anencephaly

A

Congenital absence or reduction in size of cerebral hemispheres

29
Q

Aplasia

A

Incomplete or defective development of a tissue or organ

30
Q

Atresia

A

Congenital absence or closure of a normal body opening

31
Q

Classification: Developmental excess

A
  • In size (hyperplasia)
  • In number
32
Q

Classification: incomplete development

A
  • Hypoplasia
  • Cause: excessive vs. reduced cell proliferation
33
Q

Classification: Failure to Fuse

A
  • Cleft palate
  • Septal heart defects
  • Spina bifida
34
Q

Classification: Failure of Migration

A
  • Ectopia cordis
  • Cryptorchidism
35
Q

Classification: Persistence of embryonic structures (apoptosis and shaping of structures)

A
  • Atresia: absence of natural body opening or lack of patency of a tubular structure (atresia ani, gut atresia)
36
Q

Classification: duplication

A

Cojoined, paraiste twins

37
Q

Classification: organ malpositioning

A

Dextrocardia, situs inversus

Developmental Anatomy IP3 (6 decks)

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