Embryology 2 Flashcards
What are the 2 methods that blood vessels develop by?
Vaculogenesis and angiogenesis
What is vasculogenesis?
New formation of a primitive vascular network
What is angiogenesis?
Growth of new vessels from pre-existing blood vessels
What is an extension of truncus arteriosus of primtive heart tube called?
Aortic sac
What are the first arteries to appear in the embryo
Right and left primitive aortae
What does each primitive aorta have?
A ventral part (Ventral aorta) and a dorsal part (Dorsal aorta)
What fuses to form the aortic sac?
The 2 endothelial tubes fuse and then 2 ventral aortae partially fuse to form this
What do aortic branches arise from?
Aortic sac
When do pharyngeal arches develop?
During 4th and 5th week
What is the name for the arches that receive their own nerve and artery?
Pharyngeal arteries
What do pharangeal arteries communicate with?
Aortic branches. These are now called aortic arches
What do the 6 aortic arches communicate with?
Dorsal aortae
What are the stages of the development of pharangeal arch arteries and aortic branches and their communication?
Pharyngeal arches (future neck) develop during 4th and 5th week
Each arch receives its own nerve & artery = pharyngeal arteries
Pharyngeal arteries communicate with aortic branches; these now called aortic arches
6 aortic arches are formed thus on each side, all in communication with the dorsal aortae
What are aortic arches?
Six pairs of aortic arches usually develop from aortic branches and pharyngeal arch arteries
All are not present at the same time
They all terminate in the dorsal aorta
Label this
What are the fate of arch 1 and 2?
Disappear early, remenant of the 1st aortic arch forms part of the maxillary artery
What is the fate of arch 3?
The 3rd aortic arch constitutes the commencement of the internal carotid a., and is therefore named the carotid arch
What is the fate of right arch 4?
Right subclavian artery
What happens to the left 4th arch?
Forms distal part of the aortic arch
What happens to the 5th aortic arch
Either never forms or forms incompletely and then regresses
What is the fate of proximal part of right arch 6?
Proximal part of the right pulmonary artery
What happens to the left 6th arch?
Gives off the left pulmonary a. and forms the ductus arteriosus; within 1–3 months, the ductus is obliterated and becomes the ligamentum arteriosum
What do most defects of great arteries result from?
Persistence of aortic arches that normally should regress or regression of arches that normally shouldn’t
What happens in the abberant subclavian artery?
Regression of the right aortic arch 4 and the right dorsal aorta
The right subclavian artery sometimes has an abnormal origin on the left side
To supply blood to the right arm, this forces the right subclavian artery to cross the midline behind the trachea and oesophagus
May constrict these organs, although usually with no clinical symptoms.
What is the double aortic arch?
Occurs with the non-regression of the right aortic arch
Forming a vascular ring around the trachea and oesophagus
Usually causes difficulty in breathing and swallowing
What is the patent ductus arteriosus?
More frequent in females
Common anomaly associated with maternal rubella infection - early pregnancy
What are causes of patent ductus arteriosus
Failure of muscular wall to contract
Respiratory distress syndrome (Low O2)
Lack of surfactant in the lungs
Define patent ductus arteriosus
A condition wherein the ductus arteriosus fails to close after birth.
Early symptoms are uncommon, but in the first year of life include increased ‘work of breathing’ and poor weight gain
An uncorrected PDA may lead to congestive heart failure with increasing age.
What is coarctation of the aorta?
A congenital condition wherein the aorta is narrow
Usually in the area where the ductus arteriosus (ligamentum arteriosum after regression) inserts
What does the word coarctation mean?
Narrowing
Where are coarctations in the aorta most common?
Aortic arch
What are the different positions of coarctations of the aorta?
Proximal to ductus (preductal) arteriosus or distal (postductal)
Where does most cases of coarctation occur?
Opposite the ductus arteriosus
What are the main causes of coarctation of the aorta?
Incorporation of muscle tissue of DA into arch of aorta (during development). When DA contracts after birth, part of the arch also constricts
Genetic/environmental factors
Where the the vitelline vein come from?
Yolk sac
Where does the umbilical vein come from?
Placenta
Where does the cardinal vein come from?
Rest of the body
What us the vitelline arteries represented as in adults?
Represented by arteries to the foregut, midgut & hindgut
What is the fate of umbilical arteries before birth?
Paired branches of the dorsal aorta to placenta
What happens to the umbilical arteries after birth?
Proximal portion persists as internal iliac and superior vesical branches to urinary bladder
What does vitelline vein carry blood from and to?
Yolk sac to sinus venosus
What does the umbilical vein carry blood from and to?
Originate from placenta carrying oxygenated blood to the embryo
Where does the cardinal vein carry blood from and to?
Drains the body of the embryo
What are the fates of the cardinal veins?
Main venous drainage system of the embryo
Proximal portion persists as internal iliac and superior vesical branches to urinary bladder
What are the different venous system abnormalities?
Double inferior vena cava: At the lumbar level arising from the persistence of the left sacrocardianl vein
Abscent inferior vena cava: The lower half of the body is drained by the aygos vein which enters the superior vena cava. The hepatic vein enters the heart at the site of the inferior vena cava
Abscence of inferior vena cava
Describe the development of the lymphatic system?
Develops at the end of sixth week around main veins
Six primary lymph sacs develops at the end of embryonic period
Lymphatic vessels will join the lymph sacs later
What is the foetal circulation like before birth?
Aorta to descending aorta
to abdominal aorta to common iliac artery
to umbilical arteries to placenta
to umbilical vein
What are the different foetal circulation shunts
Ductus venosus
Oval formamen
Ductus arteriosus
What is the ductus venosus?
Shunts left umbilical vein blood flow directly to IVC
Allows oxygenated blood from the placenta to bypass the liver
What is the oval foramen?
Allows blood to enter the left atrium from the right atrium
Allows blood to bypass the lungs
What is the ductus arteriosus?
Allows blood that still escapes to the right ventricle to bypass the lungs
What does the ductus venosus become?
Ligamentum venosum of the liver
What does the oval foramen become?
Closes after birth by tissue proliferation and adhesion of septal structure
Forms the fossa ovalis
What does the ductus arteriosus form?
Obliterates to form ligamentum arteriosum
What do the umbilial arteries form?
Ligamentous- medial umbilical ligaments
What are the different types of IVC?
Left SVC or double SVC
