embryology Flashcards
what does cranial refer to?
relating to the skull/ cranium
what area does caudal refer to?
tail end
what area does ventral refer to?
underside / abdominal
what area does dorsal refer to?
upperside/back
what are the 2 methods to date a pregnancy?
fertilisation age
menstrual age
how does fertilisation age date pregnancy?
it splits it into 3 stages:
- early development (ED) - cell devision and pre-embryonic
- embryonic (E) - organgenesis period
- foetal period - F
how does menstrual age date pregnancy?
dates pregnancy from the womans last menstrual period. splits it into 3 equal trimesters and lasts 2 weeks longer than fertilisation age to account for ovulation
what 2 main areas that cause congenital malformations?
genetic and environment
what are environmental factors that cause congenital malformations called and give examples
teratogens
- infections
- chemicals
- physical (radiation)
- maternal disease (diabetes)
- deficiency of folic acid
when is the foetus most vulnerable ?
highest risk during the embryonic period - week 5 peak
what are the most common infectious agents that cause birth defects - TORCH
toxoplasmosis
other organisms = i ncluding a range of viruses such as parovirus, HIV, Epstein-barr, herpes and 8, varicella, syphilis and enterovirus
Rubella
cytomegalovirus
Herpes
what is taxoplasmosis?
toxoplasmosis = parasite found in cat faeces and uncooked/ raw meat
can cause inflammation of retina, hearing loss, enlarged spleen, hydrocephaly and microcephaly
what is rubella?
Rubella = infection passses over placenta in first 3 months of pregnancy leading to cloudy cornea, intellectual disability, microcephaly and heart defects
what is cytomegalovirus?
virus that crosses placenta infection via bodily fluids, usually asymptomatic. can cause: -enlarged spleen -mineral deposits on the brain -microcephaly -psychomotor retardation
what is herpes virus?
herpes simplex - passsed on during birth
varicella zoster virus - chickenpox most dangerous 13-20 weeks or just before birth to 2 days postpartum
can cause: -segmental skinloss/scarring -limb gypoplasia/paresis -microcephaly visual defects
what are the effects of thalidomide on feotus?
causes shortened/absent limbs when used to treat morning sickness
now used to treat leprosy and HIV
what are the effects of alcohol on feotus?
foetal alcohol syndrom;
- clear relationship between alcohol consumption and congenital malformation
- small eye opening, smooth philtrum and thin upper lip
- prenatal and postnatal growth retardation
- intellectual disability
- impaired motor ability and coordination
describe capacitation
the functional maturation of spermatozoon. it allows the acrosome reaction to occur.
the physiological changes that confer the sperm the ability to fertilise
1. enzymes produced by the endometrium (edacpacitation factors) act on the sperm cleaving surface glycoproteins and increasing membrane calcium permeability
2. causes an increase in cAMP and results in hyper mobility of sperm and destabilisation of the membrane surrounding the acrosome at the head of the sperm- so it can fuse with the oocyte - exposed parts to bind with zona pellucida
describe the acrosome reaction
capacitated sperm pass through the corona radiate (cells around the egg).
the acrosome releases sperm that allows sperm to penetrate the zona pellucida.
sperm penetration initiates the zona/cortical reaction
describe the zona reaction
the modifatio of the zona pellucida in response to fertilisation.
cortical granules shut down the zygote preventing polyspermy.
firstly the zona pellucida hardens, so no more sperm can enter then the sperm receptors in the zona pellucida are destroyed so any sperm that havent bound to the zona pellucida no longer can bind. therefore the zona pellucida becomes inpentrable and DNA from the male makes its way into the oocyte
describe the formation of the morula
when a zygote (singular fertilised egg cell) divides, this is called cleavage.
when it divides, the number of cells increases, but the overall size does not and the cells are still in the zona pellucida.
when it divides to 16-32 cells, it is the morula
currently in the fallopian tube
this is day 4 post fertilisaiton
describe the components of the morula
the inner cell mass makes the embryo - embryoblasts
the outer cell mass forms the support structures (placenta) - trophoblasts
describe the transformation of the blastocyst from the morula
uterine fluid enters intracellular spaces of the morula through the zona pellucida.
the inner cell mass becomes more compact forming the mebryoblasts
the outer cell mass flattens to form the trophoblats.
the cells of the blastocyst are called blastomeres
day 5 and moves into uterus
what is cleavage?
special form of mitosis where the cells get smaller gradually in size
describe baslocyst hatching and the initiation of implantation into the endometrium of the uterus
occurs around day 5-6, involves the blastocyst hatching out of the protective zona pellucida
this allows increased growth, access to uterine nutrient secretions and blastocyst adhesion to the uterine lining
the blastocyst then implants onto the endometrium.
describe the differentiation of the trophoblast into syncytiotrophoblast and cytotrophoblast
when trohpoblast comes into contact with the nedometrium
the inner layer of the trohpoblast which is external to the all of the blastocyst differentiates into cytotrophoblasts, through fusion or invasion lineage
syncytiotrophoblasts differentiate from cytotrophoblasts by fusion pathway
describe the differentiation of the embryoblast into epiblasts and hypoblast
embroyblast differentiates into epiblast (on inside) and hypoblast cells (on top) forming bilaminar disc
what does the trophoblast differentiate into?
syncytiotrophoblasts and cytotrophoblasts
what dpes the embryoblast differentiate into?
epiblast and hypoblast
what is the importance of the epiblast and hypoblast in establishing the dorsal/ventral exis of the embryo?
bilaminar disc formation is the first stage of organisation of the body plan. it establishes the dorsal/ventral axis of the embryo - epiblast being the dorsal side, implanting (back first) into the endometrium lining. hypoblast cells form the ventral surface
describe the full implantation of the blasocyst
syncytiotrophoblasts are the outer layer of the embryo and secrete enzymes which digest the embryos way into the uterine lining
describe the formation of the amnionic cavity
small fluid filled cavity forms between the epiblast and the cytotrophoblast
describe the formation of the yolk sac
the migration of hypoblast cells to encase the blastocyst cavity at day 9 this is completely implanted and covered with hypoblast cells, forming the primary yolk sac.
a second wave of hypoblast cells migrate to form a secondary (definitive) yolk sac which pushes cells away from the embryo.
describe the production of human gonadotrophin and its importance in pregnancy testing
syncytiotrophoblasts secrete HCG which helps to maintain endometrium and may play a role in maternal immunotolerance which is a good indicator of pregnancy, this can be detected in urine
what is the name for the type of pregnancy where the embryo implants in abnormal sites
ectopic preganacy
why can embryo implant into abdominal site?
the gap between the ovary and frimbrae allows fertilised egg to go through
uterine tube implantation can cause …
haemmorage as the embryo grows as it can rupture the uterine tube
may have to have uterine tube removed along with foetus
what can occur as a result of abdominal pregnancy?
lithopaedon, when abdominal pregnacy remain undiagnosed and the foetus dies due to lack of blood supply, it is too large to be reabsorbed so it calcifies instead to protect the mother from necrotic tissue of the foetus
what is placenta privia
when implantation occurs near the cervix and can cause severe bleeding in late pregnancy
describe the formation of a hydatidiform mole
development of the trophoblast without any embryonic tissue due to fertilisation of an empty egg lacking a nucleus
syncytiotrophoblasts will still produce HCG so gives positive pregnancy test
explain the process of gastrulation
gastrulation commences in week 3 with the formation of the primitive streak
epiblast cells move towards the primitive streak
these cells then detach from the epiblast and insert into the hypoblast to replace the hypoblast cells
successive migration leads to the formation of 3 germ layers
this forms the mesoderm which is the second germ layer and the ectoderm which is the 3rd germ layer
what does gastrulation do?
transform bilaminar embryonic disc into a trilaminar disc
what are the derivatives of the ectoderm
the ectoderm forms the epidermis of the skin and epidermal derivatives (hair, nails, sweat glands, mammory glands), nervous tissue and sense organs, pituitary gland , adrenal medulla, enamel of teeth and lens of eye
what are the derivatives of the mesoderm?
dermis of the skin, epithelial (lining of blood vessels, lymph vessels, body cavities and joint caviities), muscle tissue, connective tissue, adrenal cortex, heart, kidney and ureters, internal reproductive organs and spleen
what are the derivatives of the endoderm
epithetlial (lining of respiratory tract, GI tract, lymphatic cavity, autiory tube, urinary bladder and urethra), liver, glalbladder, pancreas, thymus, thyroid gland, parathyroid glands, palatine tonsils
how is the notochord formed?
while the primitive streak is regressing, the primitive nodes form the notochordal process (hollow tube)
the notochordal process transiently fuses with the endoderm to form the flattened notochordal plate
the notochordal plate separates from the endoderm and fuses to form solid notochord
describe the role of the notochord in inducing neurulation
notochord initates neurulation by releasing signals that cause the overyling ectoderm to thicken and form the neural plate
the tube formed ends up becoming the brain and the spinal chord
describe the role of the notochord in inducing the formation of the vertebrae
the notochord initiates and organises the formation of the vertebrae from somites. the notochord induces differentiation of the somites into 3 parts - sclerotome (bone and cartilage), myotome (skeletal muscle) and dermatome (dermis)
the notochord then organises the sclerotome which srurounds the notochord to form the ventral body and surround the neural tube to form the vertebral arch
most og the notochord degenerates as bodies of vertebrae form. remnants perists as nucleus pulpous of invertebral discs
what are the two uses of the notochrod?
to intiate the formation of the vertebrae and neurulation - forming the neural tube
what are the consequences of abnormal formation of vertebrae?
spina bifida
what are the 3 main types of spina bifida?
spina bifida - spinal chord does not form properly. in spina bifida part of the neural tube does not form properly. - tuft of hair over defected point
meningocele - severe type of spinabifida where the protective membranes around the spinal cord (meninges) push out through the spine. the spinal cord usually develops normally so surgery can be done to remove the membranes without damaging the nerves
myelomeningocele - the most severe type of spina bifida, where the babys spinal canal remains open along several vertebrae in the back, allowing the spinal cord and protective membranes around it to push out and form a sac in the babys back
describe the process of neurulation and the formation of the neural tube
the overlying ectoderm to thicken and form the neural plate (induction)
describe the consequences of abnormal neurulation and neural tube defects
anecephaly - the forebrain does not form, affecting cognition, memory, speech, vision and hearing. a brain stem is present but it is usually exposed (has functioning heart, lungs and some reflexes)
rachsischisis - complete spina bifida where there s a cleft through the entire spinal column
how can neural tube defects be prevented?
by ensuring mother has enough folic acid before and during pregnancy
what is the origin of neural crest cells?
the come from cells at the lateral edge that separate the neural tube
what are the derivatives of the neural crest cells?
they disperse widely and differentiate into a variety of strcuture s thoughout the body
such as head connective and skeletal structures, nerves and pigment cells
describe the consequences of neural crest development
neurofibromatosis which is a genetic condition caused by a mutation in neurofibrin 1 (NF1) gene. this is a tumour surpressor gene that is switched off = benign tumours of nervous system, skin and cranial bones
describe ventral wall defects
ectopia cordis - lateral folds fail to fuse in thracic region, leaving the heart outside the body
gastrochisis - lateral folds fail to fuse in the abdominal region so intestines lie outside of the body walls, short time period to put into a septic bag so baby can grow space inside for intestinal contents
what are some common causes of infertility in women?
endocrine disorders uterine or uterine tube abnormalities endometriosis anti-sperm antibodies ageing cancer treatment
what are some common causes of infertility in men?
endocrine disorder
testicular abnormalities - decreased sperm o testosterone production
absence of vas deferends -cystic fibrosis
infection - mumps causes swelling of testes
anti sperm antibodies
obstruction of tract
varicocele (twisted and dilated veins around testicles = rasiign temperature and decreasing testicular function)
retrograde ejaculation (sperm released into bladder)
impotence
smoking
over weight
antibiotics
cancer treatment
what are 5 articifcal reprodcutive technologies t?
intrauterine insemination (IUI) in vitro feritilsation (IVF) and embryo transfer intracytoplasmic sperm injection (ICSI) gamete intrafallopian transfer (GIFT) zygote intrafallopian transfer (ZIFT)
