embryology Flashcards
what is the ampula of the fallopian tube
the area where the fertilisation occurs
what is cleavage
this is when the zygote undergoes proliferation from one cell to sixteen
what is the marula
the hollow ball of 16 + cells formed after cleavage. the cells surround the outer edge of the circle, leaving a cavity in the middle
what are the cells of the marula called
blastomeres
what is blastulation
the process of when the marula becomes the blastocyst
what is the structure of the blastocyst
an outer cell mass, and inner cell mass that is compacted to one side, and an empty cavity with fluid in it
what does the outer cell mass of the blastocyst become
the trophoblast
what does the inner cell mass of the blastocyst become
the embryoblast
what does the trophoblast differentiate to become
cytotrophoblast and syncitiotrophoblast
what does the cytotrophoblast and syncitiotrophoblast develop into
the placenta
how does the blastocyst enter the uterus and stay there
as cleavage is occuring, the structure slowly moves along the fallopian tube and then into the uterine canal, and with the use of integrins and selectins it is able to hook onto the endometrium
what is the cytotrophoblast
these are the well defined cell margins of the trophoblasts
what happens to the cytotrophoblast
it begins to proliferate and distintigrate the cell membrane of the blastocyst to form a fluid from the nuclei and cytoplasm of the cells.
what is the synctium
pool of fluid containing the nuclei and fused cytoplasm of the cytotrophoblast cells
what is the synctiotrophoblast
the protrusion from the blastocyst created by the cytotrophoblast that contains the nuclei and cytoplasm of the cells. no well defined cell borders
what does the syncitiotrophoblast release
hydrolytic enzymes into the uterine lining
what does the syncitiotrophoblast become confluent with
the maternal blood vessels, and this allows the embryo to receive nutrients and oxygen from the mother - this is the development of the placenta
what is produced by the syncitiotrophoblast to prevent the endometrial lining from shedding, which in turn allows the embryo to continue living
beta human chorionic gonadotropin
what does beta human chorionic gonadotropin do
stimulates the corpus luteum to produce progesterone
what happens if progesterone levels drop
the blood vessels of the uterine lining start spasming, and they then rupture. the cells in the lining become nectrotic and shed
what does shedding of the uterine lining cause
shedding of the embryo
what is the bilaminar disc
this is formed from the embryoblast, and composes of two layers sandwhiched together. the top layer is epiblast and the lower is hypoblast. above the epiblast is the amniotic cavity, and below the epiblast is the yolk sac
what is the function of the yolk sac
help with red blood cell production and provide nutrients
what is the prochordal plate
this is where the epiblast and hypoblast are connected, and provides orientation of the anatomy as it is located at the cranial aspect of the embryo
which aspect of the embryo is furthest from the prochordal plate
the caudal aspect
what is the caudal aspect of the embryo
the tail
what is the name of the membrane by the caudal aspect of the embryo and what does it develop into
the cloacal membrane which becomes the butthole
what is the name of the membrane by the cranial aspect of the embryo and what does it develop into
the buccopharyngeal membrane which develops into the mouth
what is the primitive streak
a thickening of the epiblast layer of the bilaminar disc
what is the primitive node
a knob like structure toward the top of the primitive streak
what happens to the primitve streak
the cells in the centre begin to die
what does the primitive streak become when the cells die
the primitive groove
what does the primitive node become when the centre cells die
the primitive pit
what does the primitive groove secrete
fibroblast growth factor 8,
what does FGF8 do
move laterally from the primitive groove to the epiblast cells and binds to the receptor to trigger intracellular process
what is the intracellular process triggered from the binding of FGF8 to FGF-R on the epiblast cells
SNAIL-1 is secreted
what is SNAIL-1
a protein that inhibits the formation of E-cadherins
what do E-cadherins do
they stick cells together
what does the secretion of SNAIL-1 mean
the cells are no longer stuck together and they can migrate
what is epithelial migration
the movement of the epiblast cells
where do the epiblast cells migrate to
they migrate toward the primitive streak, and move down to the hypoblast layer to replace it, forming the endoderm
what does the hypoblast become
the endoderm
what happens after the formation of the endoderm
more epiblast cells are stimulated to move through the primitive groove and down and then forward, which forms the mesoderm
what is the trilaminar disc
the product of the migration of epiblast cells to form the endoderm and mesoderm
what is the process called when the bilaminar disc becomes the trilaminar disc
gastrulation
what is gastrulation
the change from bilaminar disc to trilaminar disc
what happens following gastrulation
more growth factor is released and the cells migrate through the primitive pit to the prochordal plate to form the notochord
where in the trilaminer disc is there no mesoderm
the notochord
the cloacal plate
the prochordal plate
in which direction does the notochord go
cranially
what is the adult remnant of the notochord
the nucleus pulposus of invertebrate discs, found between the vertebrae
what does the notochord do
release growth factors and proteins to stimulate the ectodermal cells to proliferate and thicken
what does the thickening of the ectoderm result in
formation of the neural plate
what happens to the neural plate
the central portion forms a divot, which creates a groove known as the neural groove. the top of the groove curves inward creating neural folds, which eventually meet and fuse to form the neural tube which buds underneath the ectoderm to lie in between the mesoderm
why are neural folds important
they contain neural crest cells
where are neural crest cells found
surrounding the edge of the neural tube
describe the inital structure of the neural tube and what happens to it
either end has pores - anterior and posterior neural pores. they need follate to close, and should usually be closed between day 24 and 28.
what causes spinal bifida
improper closing of the neural pores
what acronym can be used to remember the derivisions of the the neural crest cells
CRESTCELL
what do the neural crest cells derive into
C - chromaffin
R - rostral tissues
E - enteric nervous system
S - satellite and schwann cells
T - nervous tissue
C - carotid bodies
E - endocardial cushions
L - ligh skin/dark skin ie melanocytes
L - leptomeninges
where are chromaffin cells found
the adrenal medulla
what are the rostral tissues
all the connective tissue, bone and muscle of the head and neck
what are the neural tissues formed from neural crest cells
spinal nerves and ganglia
what are carotid bodies important for
measuring concentration of oxygen and carbon dioxide
what are the leptomeninges of the brain
pia mater and arachnoid mater
what does the surface ectoderm become
epithelial tissue like epidermis, nails, hair, sweat glands, oral cavity and ear canal
what does the ectoderm become
- neural tube, neural crest cells, cranial nerve ganglia
- olfactory epithelium
- lens of the eye
- inner ear
what is the inner ear important for
hearing and balance
what is the lens of the eye important for
near and long vision by changing shape to refract the light differently
what is the olfactory epithelium
the epithelial lining of the roof of the nasal cavity
what acronym can be used to remember the derivisions of the ectoderm
ECTODERM
breakdown the ECTODERM acronym
E - epithelial tissue
C - central nervous system
T - the lens
O - olfactory epithelium and the lens
D - damn crest cells
E - eyes - the retina
R - anterior pituitary gland
M - melatonin from the pineal gland
what triggers the specialisation of the mesoderm
the notochord
what does the notochord release to trigger the specialisation of the mesoderm
growth factors and sonic the hedgehog hormone
what does the mesoderm specialise into
- paroxial mesoderm
- intermediate mesoderm
- lateral plate mesoderm
describe the development of the paroxial mesoderm
develops a cavity in the centre to form segments called somites, which form a cavity of their own called somatocoelie which extends to break the somites into the dermatomyotome and the sclerotome
what does the dermatomyotome develop into
the dermatome and the myotome
what does the dermatome do
it migrates and surrounds the neural tube to form the spinal meninges, dermis and subcutaneous tissue
what does the myotome do
makes skeletal muscle of the trunk, back and limbs
what does the sclerotome develop into
the vertebrae, intervertebral discs and the ribs
what does the intermediate mesoderm develop into
- renal system and ureters
- gonads
what does the lateral plate mesoderm divide into
somatic and splanchnic layers
what does the somatic lateral plate do
makes the parietal layer of the body cavities
what does the visceral lateral plate do
make the visceral layer of the body cavities
name the derivisions of the splanchnic layer of the lateral plate mesoderm
- adrenal cortex
- lymph nodes
- spleen
- smooth muscle of the GIT
- CVS
- myeloid stem cells
- lymphoid stem cells
- erthyroid stem cells
name the derivisions of the somatic layer of the lateral plate mesoderm
sternum
cartilage and bone of the limbs
what are the areas of the sternum
the menubrium
xyphoid process
body
what does the endoderm form
the gut tube, which is connected to the yolk sac and has three regions.
what are the regions of the gut tube
foregut midgut hindgut
what forms the gut tube
craniocaudal folding of the endoderm
which region of the gut tube is the cranial portion
the foregut
what do the endodermal cells of the gut tube collect and form
buds that form accessory organs to the GIT
what does the first bud of the gut tube form
respiratory tract
what does the second bud of the gut tube form
hepatic - liver and gall bladder
what does the third bud of the gut tube form
the pancreas
what does the foregut form
- pharynx
- oesophagus
- stomach
- first two parts of the duodenum
what does the midgut form
- the second two parts of the duodenum
- jujenum
- ileum
- caecum
- ascending colon
- proximal two thirds of the transverse colon
what does the pectinate line divide
the anal canal into ectoderm derived portion and endoderm derived portion
which section of the anal canal is derived from the ectoderm
the third below the pectinate line
what does the hindgut develop into
- distal third of the transverse colon
- descending colon
- sigmoid colon
- rectum and anal canal
what does the buccopharyngeal membrane of the trilaminar disc develop into
the primitive pharynx, which forms the pharyngeal apparatus
what forms from the pharyngeal apparatus
four pouches
what does the first pouch of the pharyngeal apparatus form
the middle ear and the eustachian tube
what does the second pouch of the pharyngeal apparatus form
the tonsils
what does the third and fourth pouch of the pharyngeal apparatus form
the superior and inferior parathyroid glands, and the parafollicular cells
what does the cloacal membrane of the trilaminar disc break down to form
the anal canal and the urethra
