FOUND-SOM-embryology Flashcards
what event occurs on week 1 day 1?
fertilisation
what events occurs on week one day 3?
morula (16 cell embryo)
what event occurs on week 1 day 4?
blastocyst formation/ entrance into uterine cavity
what event occur week 1 day 5?
embryo attaches to uterine wall beginning implantation
when does the differentiation of trophoblast into cytotrophoblast and syncyttiotrophoblast take place?
week 1-2
what week does the embryo complete implantation?
week 2
which days does the formation of the bilaminar disk occur?
days 7/8
week 2
when does gastrulation (formation of trilaminar disk) occur?
week 3
days 13-17
when does neurulation occur?
week 3 (finished by end of week)
what 2 events occur during week 4?
- primordial heart starts pumping blood
- limb buds appear
which 2 events occur during week 6?
- embryo shows spontaneous movement
- embryo heart can be seen with ultrasound
what is capacitation and when does it occur?
- a conditioning process sperm undergoes 7hrs before fertilisation
- involves removal of cholesterol, glycoproteins and proteins from plasma membrane around acrosomal region of sperm
- sperm penetrates corona radiata
describe the acrosome reaction?
- occurs as sperm approaches zona pellucida ( around ovum)
- enzyme acrosin is released to perforate ZP and digest proteoglycan which make up ZP
- plasma mem of sperm and ovum fuse so sperm’s genetic info is released into ovum
what remaines outside the ovum during the fusion of ovum and sperm?
mitochondria of sperm and everything else of sperm remains outside of ovum
describe the cortical reaction.
- cortical granules undergo exocytosis due to release of Ca2+ and granules further digest ZP
- ZP hardens
what does the cortical reaction prevent?
polyspermy
Where does fertilisation usually occur?
in ampulla of fallopian tube
what happens in fertilisation?
- secondary oocyte completes 2nd meiotic division
- haploid sperm + haploid secondary oocyte merge into single diploid nucleus (zygote)
how does the zygote cleave into morula?
- cleavage=rapid mitotic cell division of zygote creating individual blastomeres
- after 72hrs of repeated division-cluster of 16 called a morula
- ZP remains intact-does not increase in size
what is a blastocyst?
once the cell reaches 32-cell stage
what does the blastocyst reorganise into?
- trophoblast-outer layer, will develop into large part of the placenta
- embryoblast-inner cell mass, develop into embryo
- blastocoele-fluid filed compartment. forms the primitive yolk sac. created in the process captivation as the trophoblasts secrete fluid into the morula forming the blastocoele on day 5
what day does the Zona pellucida begin to disintegrate and what is this process called?
day 5
embryo hatching
what events occur during implantation?
- blastocyst attaches to endometrial epithelium wall
- trophoblast will adhere and secrete digestive enzymes and growth factors against endometrial surface
- trophoblast proliferates and gives rise to 2 layers
which 2 layers does the trophoblast give rise to during implantation?
1-cytotrophoblast-inner layer-forms villi
2-syncytiotrophoblast-outer layer that erodes maternal tissues
- secreted hCG
- maternal blood flows into lacunae form by syncytiotrophoblasts
which day does the embryo differentiate into hypoblast and epiblast and what does it form?
day 8
forms Bi-laminar disc
what does the blastocoel develop into and when?
yolk sac
day 9-10
where is the bi-laminar disc positioned?
between amniotic cavity and yolk sac
what is the process of gastrulation?
process where bi-laminar disc become tri-laminar disc with 3 germ layers
days 13-17
how is the primitive streak formed?
epiblasts begin to migrate inward (invaginate) forming a primitive streak
what are the tri-laminar layers and which bi-laminar layers do they form from?
(3 germ layers)
- cells replacing the hypoblast form the—–> embryonic endoderm
- cells between the epiblast and endoderm (former hypoblasts) form the —>embryonic mesoderm
- cells remaining in the epiblast form the embryonic ectoderm
what are the germ layer derivatives of the ectoderm?
- skin
- nails
- hair
- CNS (brain and spinal cord)
what are the germ layer derivatives of the mesoderm?
- musculoskeletal system
- cardiovascular system
- excretory system
- reproductive system
what are the 7 germ layer derivatives of the endoderm?
- GI tract
- lungs
- liver
- pancreas
- bladder
- thyroid/ parathyroid glands
- thymus
describe the formation of notochordal process.
-mesodermal cells from primitive node migrate toward the rostral end (head end) of the embryo and form a hollow tube of cells in the midline-notochordal process
how is the notochord formed?
the notochordal process cells will proliferate and detach from the endoderm to from a solid chord of cells-notochord
what does the paraxial mesoderm differentiate into?
skeleton and muscles
what does the intermediate mesoderm differentiate into?
gonads and kidneys
what does the lateral plate mesoderm differentiate into?
heart and blood vessels
what does the extraembryonic mesoderm differentiate into?
chorion
what does the neural tube give rise to?
CNS
what is neurulation?
neural tube formation
what is the first step of neurulation?
1- neuroectoderm tissues differentiate from ectoderm an thicken into neural plate
-neural plate border separates the ectoderm from the neural plate
how is the neural crest formed in the second step of neurulation?
2-the neural plate bends dorsally, with 2 ends eventually joining at the neural plate borders which are now referred to as the neural crest
what is the 3rd step of neurulation?
3-the closure of the neural tube disconnects the neural crest from the epidermis
-neural crest cells differentiate to form most of the peripheral nervous system
what happens to the notochord and mesoderm in the final step of neurulation and what do they form?
4-the notochord degenerates and only persists as the nucleus pulposus of the intervertebral discs
-other mesoderm cells differentiate into the somites, precursors of the axial skeleton and skeletal muscle
where are the pharyngeal arches formed?
within cranial region due to growth of mesenchymal tissue
what are pharyngeal arches separated by?
pharyngeal clefts
how many pharyngeal arches are there?
6
however the 5th regresses soon after froming
what are the 2 types of pharyngeal arch 1 and what cranial nerve are they innervated by?
- maxillary
- mandibular
-trigeminal nerve (V)
what are the muscle derivatives of the PA1 (maxillary)?
- superior oblique
- abducens
- oculomotor muscles
what are the muscle derivatives of the PA1 (mandibular)?
- muscles of mastication
- tensor tympanis
- digastric (anterior abdomen)
what are the muscles derivatives of PA2 (hyoid)?
- muscles of facial expression
- digastric (posterior abdomen)
- styloid
which cranial nerve is PA2 innervated by?
facial nerve
which cranial nerve is PA3 innervated by?
glossopharyngeal nerve
which cranial nerve are PA4 and PA6 innervated by?
laryngeal branches of vagus nerve
what are the muscle derivatives of PA3?
Stylopharyngeas
what are the muscle derivatives of PA4 and PA6?
striated muscles of oesophagus
what are the skeletal derivatives of PA1? (maxillary)
maxillary, palatine, jugal
trabecular cranii
what are the skeletal derivatives of PA1 (mandibular)?
incus. ant. lig. of malleus
palatoquadrate
meckel’s cartilage
what are the skeletal derivatives of PA2?
stapes
hyoid bone
reichert’s cartilage
what are the skeletal derivatives of PA3?
horns of hyoid
thyroid cartilage
what are the skeletal derivatives of PA4 and PA6?
cricoid cartilage
which germ layer gives rise to the lining of the digestive tract?
endoderm
on what day does implantation occur?
day 6
which 2 processes must occur before fertilisation can happen?
- capacitation of sperm
- acrosome reaction of sperm
what is the zona pellucida?
-expresses specific receptor proteins which bind to proteins expressed in heads of spermatozoa-triggers acrosome reaction
what does the formation of the primitive streak in gastrulation do?
defines the body axis of the embryo
- cranial end (head)/ caudal end (tail)
- left/ right
at which end does the neural plate of thickened cells form in neurulation and which way does it grow?
- forms at cranial end
- grow in cranial to caudal direction
what occurs as a result of embryo folding?
major body plan is established as the 3 germ layers continue to differentiate
what is embryonic folding in 2 planes simultaneously a result of?
differing rates of growth of the embryonic structures
what are 3 parts the gut tube is divided into?
- foregut
- midgut
- hindgut
give a summary of the events that occur in week 2 of development
- implantation of blastocyst is completed
- bilaminar embryonic disc is formed-composed of hypoblast and epiblast
- a number of extraembryonic structures also formed
give examples of the extraembryonic structures formed during the 2nd week of development
- amniotic cavity
- aminon
- umbilical vesicle (yolk sac)
- connecting stalk
- chorion sac
