Embryology Flashcards
embryonic period
characterised by spectacular growth and differentiation of tissues
fetal period
begins after all major organ systems are established and is characterised by growth and maintenance
gametogenesis
stage 1: production of sperm and ova
fertilisation of ovum
stage 2: sperm penetrates ovum and nuclear materials fuse
segmentation/ cleavage
stage 3: rapid division with little growth
gastrulation
stage 4: development of 3 germ layers
- ectoderm
- mesoderm
- endoderm
differentiation
stage 5: development of new cell types
histogenesis
stage 6: creation of cells typical of body tissues
organogenesis
stage 7: formation of recognisable organs
morphogenesis
stage 8: the moulding of the form and shape of the body
cell cycle
produce daughter cells by dividing its DNA and duplicating
G1 phase
metabolic changes prepare the cell for division.
-> at the restriction point- the cell is committed to division and moves to S phase
S phase
DNA synthesis replicated the genetic material
G2 phase
metabolic changes assemble the cytoplasmic materials necessary for mitosis and cytokinesis
M phase
mitosis- nuclear division followed by cell division (cytokinesis)
Mitosis
eukaryotic cell division- the same genetic material as parent produces 2 daughter cells
NOTE: essential for development of growth (tissue repair and cell replacement)
Prophase
centrosome duplicates itself to form 2 daughter centrosomes that migrate to opposite ends of the cell
Prometaphase
- chromosomes migrate to equatorial plane
- spindle fibres bind to kinetochore
- individual spindle fibres bind to a kinetochore structure on each side of the centromere
- chromosomes continue to condense
Metaphase
chromosomes align themselves along metaphase plate
Anaphase
- chromosomes divide
- chromosomes are pulled apart and move to opposite ends of the cell
- separated sister chromatids –> daughter cells
Telophase
- nuclear membrane reforms around chromosomes grouped at wither pole of the cell
- chromosomes uncoil
- spindle fibres disappear
Cytokinesis
- forms two new cells
1. in plants: cell plate forms
2. in animals: there is a constriction of the cytoplasm
Meiosis
produces haploid sex cells (gametes) from diploid cells
1st meiotic division
AKA: reduction division
reciprocal exchange of genetic material between non- sister chromatids
Prophase 1
homologous chromosomes of each pair mate and form TETRADS
Leptotene
(Prophase 1): chromosomes start to condense
zygotene
(Prophase 1): homologous chromosomes become closely associated (synapsis) to form pairs of chromosomes (bivalents) consisting of 4 chromatids (tetrads)
bivalents
pairs of chromosomes
tetrads
4 chromatids
Pachytene
(Prophase 1): crossing over between pairs of homologous chromosomes to form chiasmata
(singular. chiasma)
Diplotene
(Prophase 1): homologous chromosomes start to separate but remain attached by chiasmata
Diakinesis
(Prophase 1): homologous chromosomes continue to separate, and chiasmata move to the ends of the chromosomes
Metaphase 1
homologous pairs of chromosomes arranged as a double row along the metaphase plate
(genetic variation through random assortment)
Anaphase 1
homologous chromosomes in each bivalent are separated and moves to opposite poles
Telophase 1
homologous chromosomes in each bivalent are separated and moves to opposite poles
Interkinesis
separates the 1st meiotic division to the 2nd meiotic division
2nd Meiotic division
The chromosomes are halved - goes through Prophase 2, metaphase 2, anaphase 2, telophase 2, cytokinesis
Gametogenesis
consists of different successive stages of differentiation and maturation of the primordial germ cells into gametes
–> ova and sperm
Primordial Germ Cells
are from primitive ectoderm
- colonise the endoderm of the yolk sac (or umbilical) and the allantois
Gametes
a mature haploid (male or female) germ cell which is able to unite with another of the opposite sex –> forms a zygote.
Spermatogenesis
primordial germ cells undergo mitosis and produce gremlin stem cells.
NOTE: cells of mesoderm (genital ridge) form seminiferous cords in testes development
LEARN THE PROCESS OF SPERMATOGENESIS
Spermiogenesis
the metamorphosis of the spermatid to the spermatozoid
Spermatid
conventional cellular structure undergoes remodelling to acquire the morphology and functional capacity of the spermatozoid.
Spermiation
means the gradual migration of maturing sperm into the lumen of the seminiferous tubule
Oogenesis
development and maturation of the primordial germ cells in the ova
Oogonia
an immature female reproductive cell that gives rise to primary oocytes by mitosis
- undergoes repeated mitosis in the fatal ovary (ceases after birth)
Folliculogenesis
development and follicle maturation
Zona Pellucida
a prominent translucent acellular layer that is condensely formed by glycoproteins, secreted primarily by the oocyte
Antrum
Fluid- filled cavity
Granulosa cells
stratified layers of cuboidal cells
Ovulation
release of the ovum from the follicle
Oviduct
in vertebrates, other than mammals, the passageway from the ovaries of the body is called the oviduct
AKA: fallopian tube in mammals
- the eggs travel along the oviduct
- these eggs + sperm = zygote
NOTE: in birds= one side is favoured thus only one functional oviduct is found.
Fertilisation
process by which a sperm and egg fuse to form a zygote
- sperm penetrates corona radiata
- sperm attaches to sperm receptor to
Capacitation
a functional maturation of the spermatozoon
Polyspermy
an egg that’s been fertilised by more than one sperm
In Vitro Fertilisation
fertilisation outside the genital tract of the secondary oocytes with capacitated sperm - transfer to a recipient cycled mother
Cleavage
cell division while still enclosed in zona pellucida
- little or no growth in size
Morula
a ball of (10-64 cells)
Blastomere
each cell produced as a result of cleavage
TYPE OF SEGMENTATION
Very large yolk
in birds, fish and reptiles
- zygote prevents complete cleavage (mesoblastic cleavage- partial)
TYPE OF SEGMENTATION
Very little yolk
in mammals
- total (holoblastic) cleavage and the blastomeres are of similar size
TYPE OF SEGMENTATION
small amount of yolk
in amphibians
- yolk accumulation in vegetal pole retards mitosis and blastomeres have diff. sizes.
Dauber Layer
the trophectoderm that covers the inner cell mass
Hypoblast
(primitive ectoderm) will line the entire inner face of the embryonic disk then of the trophectoderm.
Gastrulation
the process by which the embryonic disc is converted into a trilaminar structure (ectoderm, mesoderm, endoderm) following the proliferation and migration of cells from the surface inward.
GASTRULATION
Ectoderm sheets will create…
epidermis and nervous
GASTRULATION
Mesoderm sheets will create…
Urogenital, circulatory and musculoskeletal
GASTRULATION
Endoderm sheets will create…
digestive and respiratory
blastulation
compaction of morula to form blastula before implantation
