embryology Flashcards
when is the pre-embryonic period
concpetion-week 2
when is the embryonic period
week 2-week 8
what are the stages f the pre-embryonic period
Fertilization, formation of morula and blastocyst, blastocyst implantation
when is the foetal period
week 8- birth
what are the stages of the embryonic period
Germ layer development, placenta development, body systems develop from trilaminar germ layers
what are the stages of the foeatal period
Growth and visceral development, musculoskeletal system is functional
what happens during fertilisation
- Male spermatozoon enters the female oocyte (ovum)
- the nuclei fuse forming a pronuclei
what is a blastomere
when a fertilised oocyte splits into two cells of equal sizes
what is a morula
when a blastomere divides 3 more times into 16 cells
what is a blastocyst
morula reorganise to form a cavity, known as the blastocyst cavity (blastocoel). From this point, the morula is known as the blastocyst
what are the 2 parts of a blastocyst
trophoblast
embyroblast
what is a trophoblast
Outer cell mass (trophoblast)– contacts with the endometrium of the uterus to facilitate implantation and the formation of the placenta.
what is an embryoblast
Inner cell mass (embryoblast) – responsible for the formation of the embryo itself.
what are the overall stages of the pre-embryonic period
- unfertalised oocyte
- fertilised oocyte
- two cell stage- blastomere
- continual mitosis
- morula
- blastocyst
- embryo hatches
- blastocyst rotates and impplants into the endometrium
when does the bilaminar disc form
week 2
how does the bilaminar disc form
- the trophoblast and embryoblast divide
- The trophoblast divides into the syncytiotrophoblast and cytotrophoblast.
- The embryoblast divides into the epiblast and hypoblast, forming a two-layered structure; the bilaminar disk.
where does the aminiotic cavity form from
epiblast
when does the trilaminar disc form
week 3
how does the trilaminar disk form
when the bilaminar disk undergoes gastrulation
what controls gastrulation
the primitive streak
what is the primitive streak
a groove in the midline of the epiblast
when does the primitive streak form
week 3
where is the primitive node
the cranial end of the primitive streak
what is in the primitive node
the primitive pit
what happens during gastrulation
Cells of the epiblast layer break off and migrate toward the primitive pit and form 3 new germ layers
what are the 3 layers of the trilaminar disk
endoderm
mesoderm
ectoderm
how is the endoderm formed
formed by epiblast cells that migrate through the primitive pit and displace the hypoblast cells.
how is the mesoderm formed?
formed by epiblast cells that migrate through the primitive pit and lie between the epiblast layer and the newly created endoderm.
how is the ectoderm formed
by epiblast cells that remain in position
when does the mesoderm differentiate
day 20
what does the paraxial mesoderm form
- forms dermatome which makes dermis layer of skin
- forms myotome which makes muscles
- forms sclerotome which makes bones and cartilage
what does the intermediate mesoderm form
urogenital organs and adrenal cortex and reproductive organs
what does the lateral plate mesoderm form?
- forms parietal mesoderm- parietal plura- soft tissues of arms and legs
- visceral mesoderm- visceral plura- muscle walls of gut heart and circularitory system
- intraembryonic coelom- thoracic and abdominal cavities
what happens during week 4 fo embryo development
folding of the embryo
what happens during the longitudinal folding of the embryo
Enlargement cranial end(vesicles of braindevelopment)
what happens during the lateral folding of the mebryo
somite development
what happens during the lateral folding of the embryo
somite development
what happens during the lateral folding of the embryo
somite development
what body systems develop from the endoderm?
epithelium
alimentary tract
parenchymal cells
mucosa of bladder, lungs
when does neuralation occur
day 20
what happens during neuralation
the lateral edges of the neural plate rise to form neural folds
the neural folds move towards each other and meet in the midline forming the neural tube
the mesoderm differentiates into the notochord which is a plate of cartilage
this stimulates neuralation which causes the ectoderm to thicken
this forms the central and peripheral nervous system
what is the notochord
a grove within the mesoderm which stimulates neurlation
what body systems form from the mesoderm
Notochord
Musculoskeletal system
Muscular layer of stomach, intestine etc
Circulatory system
what body systems form from the ectoderm
Notochord
Musculoskeletal system
Muscular layer of stomach, intestine etc
Circulatory system
