embryology

Question 1

what does cranial refer to?

Answer 1

relating to the skull/ cranium

Question 2

what area does caudal refer to?

Answer 2

tail end

Question 3

what area does ventral refer to?

Answer 3

underside / abdominal

Question 4

what area does dorsal refer to?

Answer 4

upperside/back

Question 5

what are the 2 methods to date a pregnancy?

Answer 5

fertilisation age

menstrual age

Question 6

how does fertilisation age date pregnancy?

Answer 6

it splits it into 3 stages:

1. early development (ED) - cell devision and pre-embryonic
2. embryonic (E) - organgenesis period
3. foetal period - F

Question 7

how does menstrual age date pregnancy?

Answer 7

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

Question 8

what 2 main areas that cause congenital malformations?

Answer 8

genetic and environment

Question 9

what are environmental factors that cause congenital malformations called and give examples

Answer 9

teratogens

• infections
• chemicals
• physical (radiation)
• maternal disease (diabetes)
• deficiency of folic acid

Question 10

when is the foetus most vulnerable ?

Answer 10

highest risk during the embryonic period - week 5 peak

Question 11

what are the most common infectious agents that cause birth defects - TORCH

Answer 11

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

Question 12

what is taxoplasmosis?

Answer 12

toxoplasmosis = parasite found in cat faeces and uncooked/ raw meat
can cause inflammation of retina, hearing loss, enlarged spleen, hydrocephaly and microcephaly

Question 13

what is rubella?

Answer 13

Rubella = infection passses over placenta in first 3 months of pregnancy leading to cloudy cornea, intellectual disability, microcephaly and heart defects

Question 14

what is cytomegalovirus?

Answer 14

virus that crosses placenta
infection via bodily fluids, usually asymptomatic.
can cause:
-enlarged spleen
-mineral deposits on the brain
-microcephaly
-psychomotor retardation

Question 15

what is herpes virus?

Answer 15

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

Question 16

what are the effects of thalidomide on feotus?

Answer 16

causes shortened/absent limbs when used to treat morning sickness
now used to treat leprosy and HIV

Question 17

what are the effects of alcohol on feotus?

Answer 17

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

Question 18

describe capacitation

Answer 18

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

Question 19

describe the acrosome reaction

Answer 19

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

Question 20

describe the zona reaction

Answer 20

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

Question 21

describe the formation of the morula

Answer 21

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

Question 22

describe the components of the morula

Answer 22

the inner cell mass makes the embryo - embryoblasts

the outer cell mass forms the support structures (placenta) - trophoblasts

Question 23

describe the transformation of the blastocyst from the morula

Answer 23

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

Question 24

what is cleavage?

Answer 24

special form of mitosis where the cells get smaller gradually in size

Question 25

describe baslocyst hatching and the initiation of implantation into the endometrium of the uterus

Answer 25

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.

Question 26

describe the differentiation of the trophoblast into syncytiotrophoblast and cytotrophoblast

Answer 26

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

Question 27

describe the differentiation of the embryoblast into epiblasts and hypoblast

Answer 27

embroyblast differentiates into epiblast (on inside) and hypoblast cells (on top) forming bilaminar disc

Question 28

what does the trophoblast differentiate into?

Answer 28

syncytiotrophoblasts and cytotrophoblasts

Question 29

what dpes the embryoblast differentiate into?

Answer 29

epiblast and hypoblast

Question 30

what is the importance of the epiblast and hypoblast in establishing the dorsal/ventral exis of the embryo?

Answer 30

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

Question 31

describe the full implantation of the blasocyst

Answer 31

syncytiotrophoblasts are the outer layer of the embryo and secrete enzymes which digest the embryos way into the uterine lining

Question 32

describe the formation of the amnionic cavity

Answer 32

small fluid filled cavity forms between the epiblast and the cytotrophoblast

Question 33

describe the formation of the yolk sac

Answer 33

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.

Question 34

describe the production of human gonadotrophin and its importance in pregnancy testing

Answer 34

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

Question 35

what is the name for the type of pregnancy where the embryo implants in abnormal sites

Answer 35

ectopic preganacy

Question 36

why can embryo implant into abdominal site?

Answer 36

the gap between the ovary and frimbrae allows fertilised egg to go through

Question 37

uterine tube implantation can cause ...

Answer 37

haemmorage as the embryo grows as it can rupture the uterine tube may have to have uterine tube removed along with foetus

Question 38

what can occur as a result of abdominal pregnancy?

Answer 38

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

Question 39

what is placenta privia

Answer 39

when implantation occurs near the cervix and can cause severe bleeding in late pregnancy

Question 40

describe the formation of a hydatidiform mole

Answer 40

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

Question 41

explain the process of gastrulation

Answer 41

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

Question 42

what does gastrulation do?

Answer 42

transform bilaminar embryonic disc into a trilaminar disc

Question 43

what are the derivatives of the ectoderm

Answer 43

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

Question 44

what are the derivatives of the mesoderm?

Answer 44

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

Question 45

what are the derivatives of the endoderm

Answer 45

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

Question 46

how is the notochord formed?

Answer 46

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

Question 47

describe the role of the notochord in inducing neurulation

Answer 47

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

Question 48

describe the role of the notochord in inducing the formation of the vertebrae

Answer 48

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

Question 49

what are the two uses of the notochrod?

Answer 49

to intiate the formation of the vertebrae and neurulation - forming the neural tube

Question 50

what are the consequences of abnormal formation of vertebrae?

Answer 50

spina bifida

Question 51

what are the 3 main types of spina bifida?

Answer 51

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

Question 52

describe the process of neurulation and the formation of the neural tube

Answer 52

the overlying ectoderm to thicken and form the neural plate (induction)

Question 53

describe the consequences of abnormal neurulation and neural tube defects

Answer 53

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

Question 54

how can neural tube defects be prevented?

Answer 54

by ensuring mother has enough folic acid before and during pregnancy

Question 55

what is the origin of neural crest cells?

Answer 55

the come from cells at the lateral edge that separate the neural tube

Question 56

what are the derivatives of the neural crest cells?

Answer 56

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

Question 57

describe the consequences of neural crest development

Answer 57

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

Question 58

describe ventral wall defects

Answer 58

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

Question 59

what are some common causes of infertility in women?

Answer 59

``` endocrine disorders uterine or uterine tube abnormalities endometriosis anti-sperm antibodies ageing cancer treatment ```

Question 60

what are some common causes of infertility in men?

Answer 60

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

Question 61

what are 5 articifcal reprodcutive technologies t?

Answer 61

``` intrauterine insemination (IUI) in vitro feritilsation (IVF) and embryo transfer intracytoplasmic sperm injection (ICSI) gamete intrafallopian transfer (GIFT) zygote intrafallopian transfer (ZIFT) ```