94. Embryology Flashcards
how many stages in embryology
23 Carnegie stages based on morphological characteristics
developmental periods are how long
9 months / 38-40 weeks / 3 trimesters
how long is conceptus embryo
0-3 weeks
embryonic period is how long
3-8 weeks
foetal period is how long
9-40 weeks
what is teratology
The study of abnormal development (terato=abnormal)
what are teratogens
Teratogen is an agent that the mother is exposed to that can cause abnormalities.
name the 5 types of teratogens
- physical
- chemical
- nutritional
- hormonal
- infection
when is teratogen risk highest
first 8 weeks - embryonic period
what kinds of things are types of teratology
deformation
malformation
disruption
describe malformation
Complete absence or partial absence of a structure or alterations in its normal configuration
Can be caused by environmental factors and/or genetic factors
E.g. poldactyl
describe Disruption
Morphological alterations of already formed structures and are caused by destructive processes
E.g. amniotic band syndrome
describe deformation
Abnormal form due to mechanical factors over a prolonged period
E.g. clubfoot (equinovarus foot)
Phases of Embryogenesis
Gametogenesis,
Fertilization
Cleavage
Gastrulation
Morphogenesis
Organogenesis
how many chromosomes in diploid cell
46
what is gametogenesis
- formation of a gamete form a primordial cell
what is a gamete
a cell like an ovum or sperm with a complement of 23 chromosomes aka half of a somatic cell
gamete is haploid/diploid?
haploid
what kind of division do haploid cells go through
Consisting of mitosis and meiosis
what is the formation of male gametes called
spermatogenesis
how long is the process of spermatogenesis and how much sperm is produced per day?
when does spermatogenesis begin and when does it end
64-74 days
300 million per day
Begins at puberty and continues throughout life
name the 3 phases and order of spermatogenesis
Spermatogonial Phase
Spermatocyte Phase
Spermatid Phase
what is the process called of the formation of female gametes
Oogenesis
when does Oogenesis start and when does it end
starts - development
ends- menopause
fertilisation is
the union of gametes/ fusion of spem and oocyte/
formation of zygote
describe a zygote
diploid
single cell embryo
sex determination (46xx/46xy)
cleavage is the period of
rapid mitotic cell division with no increase in size
cleavage causes the formation of what then what
Morula (16+ cells) then Blastocyst
End of second week a ….. is formed
bilaminar disc
Start of third week there is…..
gastrulation (trilaminar)
what is gastrulation
The process that establishes all three germ layers
Ectoderm
Mesoderm
Endoderm
Body folding days
cranial and lateral - day 22
caudal - day 23
what is the name for formation of organs and organ systems
organogenesis
foetal period where most growth and weight gain is
Mainly grows in length during 2nd trimester
Most weight is added in 3rd trimester
name the Primary Developmental Processes
Cell Division
Increase in number of cells
Influence shape and growth
Differentiation
Change in appearance/structure
Adoption of new functions (specialization)
Cell Attachment
Physical/functional linkages between cells
Formation of tissues
Apoptosis
Programmed cell death
Creates spaces and cavities
Induction
Ability of one cell type to cause another to differentiate
Directly or at a distance
Cell migration
Movement from one location to another
Secondary Developmental Processes
Axis formation/ Polarity
- Cell will understand its position
Folding/ Rotation
- Entire embryo or structures within it
Increases /Decreases in mass or dimension
-Compaction
- Expansion: hypertrophy/hyperplasia
