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DAT - Biology > Chapter 18 - Developmental Biology > Flashcards

Chapter 18 - Developmental Biology Flashcards

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1
Q

What is embryology?

A

Study of the development of a unicellular zygote into a complete, multicellular organism

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2
Q

What occurs over the 9 months of pregnancy?

A

Unicellular human zygote undergoes cell division, cellular differentiation, and morphogenesis in preparation for life outside the uterus

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3
Q

What are the 2 early developmental stages?

A

Fertilization and cleavage

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4
Q

Describe fertilization:

  • Time period?
  • Where is occurs?
  • Twins?
A
  • Fertilized ovum within 12-24h after ovulation
  • Occurs in latereal, widest portion of oviduct
  • More than one fertilized egg result in twins
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5
Q

Describe cleavage:

  • What does it increase?
  • What does it result in?
  • First complete cleavage? Second? Third?
  • Types of embryonic cells?
A

Early embryonic development is characterized by a series of rapid mitosis decisions known as cleavage

  • Increases cell number without corresponding growth in cell protoplasm; also, increases surface-area-to-volume ratio which improves gas/nutrient exchange
  • Results in progressively smaller cells with increasing ratio of nuclei to cytoplasm
  • First complete cleavage of zygote occurs 32h after fertilization; second occurs 60h; third occurs 72h which is 8-celled and reaches the embryo
  • Cell division continues until morula is formed; blastulation begins when morula develops into blastocoel (blastula); implants on uterus
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6
Q

How does emergency contraception work?

A

Blocks implantation

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7
Q

What is an ectopic pregnancy?

A

Embryo implants elsewhere than the uterus

- Usually aborts

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8
Q

What occurs during gastrulation?

A

After week 2, the embryo is fully implanted in the uterus and the cell migrations transform single cell layer of blastula into 3-layered structure called a gastrula:

  • Ectoderm: Integumentary system (epidermis, hair, nails, mouth, anal canal)
  • Endoderm: Epithelial lining of respiratory and digestive tract, and liver, pancreas
  • Mesoderm: Musculoskeletal system, circulatory system, excretory system,. gonads, connective tissue, digestive/respiratory organs
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9
Q

What is neurulation? What develops? What does its inductive effect cause? What does it do once its formed?

A

At the end of gastrulation, regions of the germ layer develop into a nervous system (week three)

  • The notochord develops along longitudinal axis of embryo just under the dorsal layer of ectoderm
  • It has an inductive effect on overlying ectoderm causing it to bend inward to form a grove along the dorsal surface of the embryo; fuse and form a close tube that gives rise to the brain and spinal cord (CNS)
  • Once formed it detached from surface of ectoderm
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10
Q

What are neural crest cells?

A

Cells at the tip of each neural fold which migrate laterally and give rise to components of the peripheral nervous system
- Includes: Sensory ganglia, autonomic ganglia, adrenal medulla, and schwann cells

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11
Q

What happens if the neural tube does not close properly? What can decrease this chance of occurring?

A

Spina bifida

- Folic acid consumption during pregnancy

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12
Q

What are the three stages of development?

A

1) Organogenesis: Body organs form; cells differentiate and change physical shape to proliferate and migrate
2) Growth: Organs increase in size
3) Gametogenesis: Eggs develop in women and sperm develop in men = permits reproduction

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13
Q

How does the fetus receive oxygen? What is it called?

A

Through a specialized circulatory system from its mother which supplies oxygen and nutrients, and removes CO2 and waste
- Placenta and umbilical cord

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14
Q

What is the placenta and umbilical cord composed of and how does it form?

A

Outgrowths of 4 extra-embryonic membranes formed through development:

  • Amnion: Thin, tough membrane containing watery amnionic fluid; acts as shock absorber of external pressure during gestation and localized pressure from uterine contractions
  • Chorion: Placenta formation begins with chorion, a membrane that completely surrounds the amnion; assists in transfer of nutrients from mother to fetus
  • Allantois: Develops as an outpacing of gut; blood vessels of this portion enlarge and become umbilical vessels which connect fetus to developing placenta
  • Yolk sac: Site of early development of blood vessels, becomes associated with umbilical vessels
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15
Q

What is gestation? How long does it last?

A

Human pregnancy

  • 9 months
  • 266 days
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16
Q

How is gestation subdivided?

A

1) First Trimester
2) Second Trimester
3) Third Trimester

17
Q

Describe the first trimester:

  • What develops?
  • When does the heart beat?
  • What forms?
  • How long is the embryo at 5 weeks, 6 weeks, and at 3 months?
  • When does bone form?
  • Have most of the organs formed; what about the brain?
A
  • Major organs begin to develop
  • Heart beats at ~22 days
  • Eyes, gonads, limbs and liver start to form
  • 5 week embryo is 10mm long; 6 week embryo is 15mm long; 3 months fetus is 9cm long
  • Cartilaginous bone forms into bone at week 7
  • Most organs are formed at week 8 and the brain is fairly developed
18
Q

Describe the second trimester:

  • What does the fetus do?
  • Can it move?
  • Facial features?
  • Toes/fingers?
  • Length?
A
  • Grows a lot
  • The fetus can move
  • The fetus has facial features
  • Fingers and toes elongate
  • End of month 6, 30-36cm
19
Q

Describe the third trimester:

  • What development occurs here?
  • Antibodies?
  • Growth rate?
A
  • Rapid growth and further brain development
  • Antibodies are transported by highly selective active transport from mother to fetus
  • Growth rate slow and fetus is less active (less room to move)
20
Q

How is child birth accomplished?

A

Labour: A series of strong uterine contraction

21
Q

What are the 3 stages of labour?

A

1) First Stage: Cervix thins and dilates, and the amniotic sac ruptures, releasing its fluid contents; mild contractions
2) Second Stage: Rapid contractions resulting int he birth of the baby
3) Third/Final Stage: Uterus contracts to expel placenta and umbilical cord

22
Q

What are congenital disorders? How are they caused?

A
  • Birth defect that can present a wide variety of symptoms, even death
  • Errors during fetal development and/or often caused because of deleterious genes or problems with gestation environment
23
Q

What is a teratogen?

A

Chemical and biological agents that can cause disorders

- Ex. Alcohol, drugs, tobacco, bacteria, viruses

24
Q

What is a vertical transmission?

A

When a mother passes on an infection directly to her developing offspring during development or birth

25
Q

What are some environmental factors that can lead to birth defects?

A

Poor nutrition, radiation, physical trauma or restraint

26
Q

What is experimental embryology?

- What do scientists hope to do?

A

A field that aims to investigate effects and other factors on development
- Hope to identify risk factors for women who could become pregnant and treatments applicable throughout human life cycle

27
Q

How does seed formation occur?

A

Zygote divides mitotically to form mass of cells called an embryo

28
Q

What does a plant embryo consist of?

A

1) Epicotyl: Precursor to upper stem/leaves
2) Cotyledons: Seed leaves; dicots have 2, monocots have 1
3) Hypocotyl: Lower stem and root
4) Endosperm: Feeds embryo; in dicots it absorbs the endosperm
5) Seed Coat: Develops from the outer covering of the ovule; embryo and seed coat together comprise the seed

29
Q

How do seeds develop and disperse?

A

In most fruit, seeds develop in the ovary walls at the base of the flower and other pistil components

  • The fruit enables the seed to be carried/dispersed effectively by air, water, or animals
  • The seed is released from the ovary and may germinate under proper conditions (i.e. temperature, moisture, and oxygen)
30
Q

How do plants grow?

A

Growth in higher plants is restricted to embryonic cells called meristem cells

  • Undergo active cell reproduction
  • Gradually elongate and differentiate into cell types characteristic to the species
31
Q

What are the 2 types of meristem?

A

1) Apical: Tips of roots/stems; growth occurs in length

2) Lateral: Located between xylem/phloem; growth occurs in diameter
- Not active in monocots
- Dominant in dicots

DAT - Biology (16 decks)

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