Developmental Biology Flashcards

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1
Q

Fertilization

A

in mammals, an egg can be fertilized within 24 hrs after ovulation

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2
Q

Cleavage

A
  • a series of rapid mitotic division
  • results in progressively smaller cells w/ an increasing ratio of nuclei to cytoplasm
  • increases the surface-area-to-volume ratio - improving gas to nutrient exchange
  • first complete cleavage of a zygote occurs approx 32 hours after fertilization
  • the second cleavage occurs 60 hrs and the third cleavage approx 72 hrs = 8 celled embryo reaches th uterus
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3
Q

Morula

A

a solid ball of embryonic cells

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4
Q

Blastulation

A
  • begins when the morula develops a fluid-filled cavity called the blastocell - after the 4th day becomes the blostula
  • the blastula is the stage of the embryo that implants in the uterus
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5
Q

Gastrulation

A
  • after week 2, the embryo is fully implanted in the uterus

- blastula becomes a 3-layered structure called gastula

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6
Q

Ectoderm

A

integumentary system, lens of the eye, the retina, and the nervous system

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7
Q

Endoderm

A

epithelial linings of the digestive and respiratory tracts

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8
Q

Mesoderm

A

musculoskeletal system, circulatory system, excretory system, gonads, connective tissue, and the portions of digestive and respiratory organs

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9
Q

Neurulation

A
  • at the end of gastrulation, regions of the germ layers begin to develop into a rudimentary nervous system - starts before week 3
  • the notochord develops into a closed tube, which gives rise to the brain and spinal cord (CNS)
  • the cells at the tip of each neural fold give rise to many components of the PNS - sensory ganglia, autonomic ganglia, adrenal medulla, and schwann cells
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10
Q

Organogenesis

A

body organs begin to form

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11
Q

Growth

A

organs increase in size

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12
Q

Gametogenesis

A

Eggs develop in women and sperm develop in men

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13
Q

Placental Development

A
  • the placenta and umbilical cord supply oxygen and nutrients to the fetus and removes carbon dioxide to metabolic wastes
  • the umbilical cord are outgrowth of the amnion, chorion, allontois, and yolk sac
  • the amnion contains the amniotic fluid that acts as a shock absorber of external pressure
  • placenta formation begins with the chorion, a membrane that surrounds the amnion that assists with the transfer of nutrients from the mother to the fetus
  • the allontois become the umbilical vessels which will connect the fetus to the developing placenta
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14
Q

Gestation

A

approx 9 months and subdivided into 3 trimesters

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15
Q

First Trimester

A

major organs begin to develop and heart beats ~ 22 days

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16
Q

Second Trimester

A

the fetus begins to move around the amniotic fluid

17
Q

Third Trimester

A

further brain development, fetus becomes less active and has less room to move around

18
Q

Birth and Maturation

A
  • labor can be divided into 3 distinct stages
  • first stage: the cervix thins and dilates and the amniotic sac ruptures, releasing its fluids
  • second stage: rapid contractions resulting in the birth of the baby
  • final stage: uterus contacts expelling the placenta and the umbilical cord
19
Q

Congenital Disorders

A

-birth defects can be caused by chemical and biological agents (teratogens)

20
Q

Epicotyl

A

percurser of the upper stem and leaves

21
Q

Cotylodons

A

Seed leaves

22
Q

Hypocotyl

A

the lower stem and room

23
Q

Endosperm

A

Feeds the embryo

24
Q

Seed Coat

A

develops from the outer covering of the ovule; the embryo and its seed coat together, comprise the seed