Embryology

what comes off the uterus and describe the ovary

- pair of uterine horns

- fingerlike projections come off the fallopian tube which flop over the over and help collect eggs released by ovary

ovullation

- ovary has growing follicles mature and get bigger

- eventually the follicle ruptures and the secondary oocyte is released and captured by fimbriae of the infandibulum of the uterine tube

- it goes into the distil end of the uterine tube

ampulla

means little bottle

female egg

about 85000x bigger then male sperm

fertilisation

- sperm reaches egg

- acrosome (on tip of sperm) prod. enzymes that break down a small portion of the wall of the 2ndry oocyte

- sperm gets in and theres a biochemical change --> the wall then seals itself

- sperm fuses with female pro nucleus and creates male pro nucleus

corona radiata and zona polucida

corona radiata = outside long finger like

zona polucida = made of glycoproteins

inside of these id the cell with standard genetic spindle arrangement

step once male pro nucleus forms

- spindle arrangement forms and first division --> 2 separate cells form --> rapid ell division --> clump of around 16 cells called morular --> continued divison forms blastocyst

balstocyst

- clumping of cells

blastocyst cavity

clump of cells

2 layers

- trophoblast - sends processes into wall of uterus - connects with uterus

- inner layer embryo blast

week 1

1. pre ovulation follicle

2. ovulation

3. track through ampula 4. fertilised by sperm

5. DNA replication

6. spindle formation

7. 2 cells

8. 3 days = morula

9. 4 days = big morula

10. 5-6 days = blastocyst fuses with endometrium

ectopic pregnancy

implantation of the fertilized egg in any site other than the normal uterine location

- ovarian pregancy - stays within ovary

- intrabdomanl - outside the whole uterine structures

- isthmus or ampula pregnancy called an ampullary or infamdibular

- instastitial - in the wrong layers

-cerviacle - too far down

clinical ectopic pregnancy case WITH bleed out

unwell pregnant lady

- pain in shoulder when lying down due to free blood in abdominal cavity tracking up the 2 parabolic gutters hit the diaphragm

- C345 nerves that innervate the diaphragm also inervate top of shoulder --> referred pain suggests blood is irritating diaphragm - free blood

week 2

1. bilaminar disc is embedded within substance of endometrium

2. openiing is filled with fibrin plug

3. blood vessels bring in nutrients

4. 2 layers of trophoblast area = cyncitiotropopblast and cytotropoblast

5. innercell mass =composed of epiblast and hypoblast

6. epiblast becomes hollow with amniotic cavity --> this grows

7. developmental patterning happens

epiblast and hyperblast locations

epiblast - found of amniotic cavity side

hypoblast - found on yolk sack side

amniotic cavity

only exist in 3 types of animals - mammals, birds and reptiles

- these 3 groups = amniotes

cuadal end and cranial end

caudal = primitive streak

cranial = buco pharyngeal membrane - will be the primative opening into the mouth

- these 2 grow and merge

week 3

1. primitive streak and buco pharyngeal membrane merge

2. lots of cellular activity down primitive streak - mesoderm cells move between epiblast and hyper blast gap

3. rod - notochord -develops under epiblast becoming ectoderm

4. mesoderm cells become mesolayer

4. endoblast becomes endoderm

6. notochord becomes backbone and vertebrae

7. heart tube forms with blood flow from caudal to cranial

ectoderm

- outermost layer

- gives rise to skin

- CNS and PNS

- eyes and internal ear

mesoderm

- middle layer

- bones, connective tissue, skeletal muscle

- eurogenital system

- cardiovascular system

endoderm

- innermost layer

- gut

-all associated derived tissue e.g. liver, pancreas and lungs

nuerulation

formation of our central nervous axis

- neural plate folds inwards and creates a tube

- adjacent neural material folds a tube at the top and this becomes the primitive brain

- amniotic cavity and primitive yolk sac

- amniotic cavity becomes bigger and will eventually surround the embryo

invagination

happens along the primitive streak creating a long groove

- layers of he ectoderm come together and eventually fuse and form a tube

- forms notochord

- tube made of ectoderm becomes spinal chord

- at crest is neural crest cells

neural crest

only found in backboned of animals - vertebrae

- starts in the middle and then closes up either end

antirior nueral pore closes in 24 days

posterior nerual pore closes at 28 days

failure of posterior neural pore closing

leads to spina bifida

failure of anterior neural pore to close

- anencephaly = open brain and lack of skull vault

- still born baby

Prosencephalon

forebrain

- the bit that buldges out and folds forming telencephalon

- the bit that doesnt buldge out is the diencephalon --> becomes the rest of the forebrain

mesencephalon

midbrain

- this bends

- disitil to prosencephalon

rhombencephalon

hindbrain

- this bends and becomes the 4th ventricle

- at base of brain joins to the primitive spinal chord

bilaminar disc in development

becomes trilaminer disc

head region development

- develop series of cardiogenic cells in cardiogenic area

cardiogeneic mesoderm

comes from the lateral plate mestoderm

- u get blood islands

- hemangioma blasts = create blood - create the endo cardial heart tube

- myoblast = create cardio muscle

angiogenic cell clusters

these coelese and form a right and left endocardial tube

- they fuse

- blood comes in the caudal end, goes through the tube and passes out through the cranial end

- the midpart fuses and the lateral parts seperate --> forms primitive heart tube

truncus arterious

where the 2 arteries come out of the gut tube

- trunk of artery

- gives proximal artery, aorta and pulmonary artery

- gives off aortic arch arteies by 5 weeks

bulbus cordis

proximal to truncus arterious

- bulb of heart

- creates the outflow tract

primitive venticle

middle

- creates LEFT ventricle

primative atria

caudal to primitive ventricle

- creates L and R atria

sinus venosus

2 big veins that bring blood from body into primitive heart tube

- create smooth part of R atrium and coronary sinus

blood flow order

- veins drain blood from sinus venosus through primitive atria

- then through primitive ventircle into the bulbos cordis and out through truncus arterious

heart formation between days 23-28

- hearts limited in length by pericardium

- tube begins to fold within the pericardium

- it lengthens and begins to curve towards the right

- primitive ventricles expand

- artia next expands

- left then right ventricle forms

35 days of heart

heart starts to resemble normal heart

- 2 sinus vinosa is pumping in deoxygenated blood from the rest of the body to the mums umbilical chord

- sinus venosus is making the smooth part of the right atrium and coronary sinus

Cristae terminalis

right atrium seem goes round in coronal plate

Pectinate msucles

found in front

sinus venarum

smooth posterior wall of the right atrium

how are the 2 chambers connected

atrioventricular canal

route of blood through week 5-6 heart

in through sinus venous through the atrioventricular valves, does a loop then out through primitive aortic branches

bulbous cordis later development

- loops to the right - dexrtral looping

- conotructus - in front anterior

- right ventricle - posterior side

- primitive atrium gets displaced dorsally

- ventricles expant and conotruncus becomes 2 buldges, truncus anteriosis and conus cordis is ALL apart of the bulbous cordis

- the future L adn R ventricle and outflow tract forms

septum transversum

primitive diaphragm

- heart sits in the centre of primitive diaphragm

conus cordis ridge

twisting septum

- creates aortic outflow on one side and on the other side is the pulmonary trunk outflow

- develops within truncus arteriosus

- atriovetricular orephis eventually closes

endocardial cushions

form about 28 days

- 2 swellings of mesenchymal tissue appear from walls of the canal

- the endocardial cushions grow and fuse together to divide canal into right and left

middle of primitive heart

endocardial cushion creates right and left artioventricular canal

septum primum

wall that comes down as a crescent and ostium primum forms between tip of septum primum and endocarial cushion

ostium secundum

small space in middle of septum primum that begins to seperate right and left atria

septum primum fuses with endocardial cushion

we now have inter atrial sseptum wall with ostium secundum

- right and left atrai are not yet fully seperated

where is the septum secundum found

pathway of blood

right atrium

- this secondary wall goes down and covers ostium secundum

- opening forms on the right for passage way of blood from right opening and pushes lower part of septum primum away, past the ostium secundem into the left atrium --> valve from right to left atrium --> foreamen ovale

foetal circulation

oxygenated nutrient rich blood comes from mum via placenta, in through umbilical vein

umbilical vein passageway

passes through liver, in through what will be inferior vena cava into right atrium, goes throuh foramen ovale into left atrium

ductus venous

shunts blood from umbilical vein to inferior vena cava

- bypassing the liver

foramen ovale

shunts blood from RA to LA

- bypassing pulmonary circulation

- only about 10% of all blood goes into the right ventricle bc:

blood air barier in walls of alviolus in the adult lung is REALLY delicate - the feotal lungs would be torn apart - but abit goes in so oxygen allows it to mature

ductus arteriosus

shunts blood from pulmnary trunk to ascending aorta

- bypassing lungs

3 bypassing points

ductus venosus - in developing liver

foramen ovale between left and right atria

ductus venosus between pulmonary trunk and underside of aorta

after birth theres tissue and biological changes

- describe these changes in ductus venosus

ductus venousus becomes ligementum arteriosum which then becomes the ligamentum teres hepatis

- finds termination on inside of what would become the belly buttton

foramen ovale change

closes bc of increased pressure in LA compared to RA to form fossa ovalis

- happens at birth

ductus arteriosus change

fibroses to form ligamentum arteriosum

patent foramen ovale

foramen ovale which doesnt close to form a fossa ovalis

- in around 25% of ppl a probe can be passed from one atrium to another

- defect is usually small and not significant

atrial septal defects

- incidence rate = 7:10,000 births

- females 2x more affected then males

- septum primum and septum secundem defects

- mixed blood reduces overall oxygen load

- increased pulmonary arterial pressure - RV tries to compensate by its wall getting thicker (RVH)

- increased pulmonary hyper tension

pulmonary hyper tension

increased blood pressure in the lungs --> bad bc it pushes fluid from the capillaries into the alviolum

right ventricular hypertrophy

wall gets pathologically thicker

ventricular separation

- end of 4th week a muscular IVS develops from floor of primordial ventricle

- grows cranially towards membranous IVS which develops from endocardial cushions

- membranous part grows caurderly and muscular part grows cranially to meet in the middle and form the IVS - intrular ventricular septum

ventricular septal defect

- most comon cardiac defect - 25% of congenital heart defects

- many small VSD close spontaneously

- about 90% of VSD are in membranous septum and 10% in muscular septum

gut tube development foregut

stomach, 1st part of duodenum, liver, panreas and spleen

- comes from coeliac trunk

gut tube development midgut

caudal duodenum, small and large intestine up to splenic flexure

- superior mesenteric artery

gut tube development hindgut

splenic flexure, descending, singmoid colon, rectum,. upper anal canal

- comes from inferior mesenteric artery

describe midgut development

- rapid elongation and begins to herniate out the abdominal cavity into the umbilical cord

- it then rotates twice, increases in size and the gut tube moves back into the abdominal cavity

- 12 week it resembles the adult version