Cardiovascular system I and II Flashcards
What occurs day 18 in front of the neural plate and oropharyngeal membrane?
Paired strands of endothelial cells called ANGIOBLASTIC CORDS appear
How does the endocardial tube form?
After day 18 (the appearance of angioblastic cords), the cords soon canalize to form Paired endocardial heart tubes which quickly fuse to form a single endocardial tube
When do the earliest heartbeats occur?
Early wk 4
What is cardiac jelly and where is it found?
It is a gelatinous acellular connective tissue matrix which separates the endocardium and myocardium in the endocardial heart tube
What is the direction of blood flow in the endocardial heart tube?
Sinous venosus>atrium>ventricle>bulbus cordis>truncus arteriosus>aortic sac & arches
Inferior to superior: SV A V BC T A
Mneumonic: All Teeth (on) {CuteBaby} Vampires Are {Very Small} [blood flow would be backwards]
How does the endocardial tube fold?
The growth of the tube produces a looping to the right. The ventricle, bulbus cordis, and truncus arteriosis come anterior,
while the sinus venosus and atrium lie posterior
Which gene is the master key gene for heart development and what other genes regulate it?
NKX2.5; BMP 2 and BMP4 along w/ the inhibition of WNT will cause expression of this master gene.
NOTE: TBX5, a transcription factor, plays a role in septation (so any septation defects will probably have this gene involved in some way)
How do the heart chambers begin to form at the end of the 4th wk?
Endocardial cushions composed of cardiac jelly grow towards each other (via mesenchymal cell invasion), fuse, and form right and left atrioventricular canals. They separate mainly the ventricles form the atrium
What does the Msx-1 gene do?
When expressed, It transforms endothelial cells in the atrioventricular region into mesenchymal cells that invade the cardiac jelly causing endocardial cushion growth.
Describe how the atria are separated
- The septum primum grows antero-inferiorly, dec. size of foramen primum (foramen b/w atria).
- B4 complete division of atrium happns, postero-superior portion of septum primum degenerates forming a foramen secundum.
- Septum secundum devlops in the right atrium to the right of the septum primum, grows postero-inferiorly, and covers foramen secundum but doesn’t seal, creating the foramen ovale.
- Complete closure of foramen ovale happens at 3 months (after birth)
What becomes of the embryonic atria and the small left sinus in the adult heart?
The embryonic atria become auricular appendages in the adult heart on both rt&lft sides;
The left sinus becomes the coronary sinus
Describe how the ventricles are separated
- The primitive interventricular septum grows superiorly from the future apex towards the endocardial cushions but doesn’t reach them, leaving an InterVentricular (IV) foramen that persists until wk 7.
- The Bulbus Cordis and Truncus Arteriosis partition into the pulmonary trunk and ascending aorta, and their ridges develop from the walls of the bulbus and truncus, and undergo a 180o spiral course. The spiraling ridges fuse w/ each other to form an aorticopulmonary septum.
- The aorticopulmonary septum fuses w/ the endocardial cushions and primitive IV septum to complete ventricle partitioning.
What acts as the interim pacemaker of the heart before the sinus venosus takes over?
The primitive atrium
How do the SA and AV nodes develop?
In wk 5, the SA node develops in the wall of the Sinus Venosus, but is later incorporated into the wall of the right atrium, at its junciton with the superior vena cava;
The AV node and bundle are derived from cells in the wall of the sinus venosus and the AV, canal, with their final position being at the base of the atrial septum
What is the most distal portion of the truncus arteriosus and what arises from this?
The aortic sac; the six paired arches arise from this and terminate in the dorsal aortas
What are the adult derivatives of the 6 aortic arches?
1st arch: Portions of maxillary & extrnal carotid a.’s
2nd: Stapedial a.
3rd: Common carotid and portions of internal carotid a.’s
4th: Aortic arch on LEFT, Proximal subclavian a. on RIGHT
5th: Never truly present in human
6th: Portions of right and left pulmonary a.’s, and ductus arteriosus on LEFT
Due to the differences b/w right and left side development of the aortic arches, where do the recurrent laryngeal n.’s loop?
Right n. loops high under the right subclavian a.;
Left n. loops lower under the aortic arch, later to the ductus arteriosus
What are the 3 major systems of veins in a developing embryo, and from where do they arise?
- Vitelline system: from yolk sac
- Umbilical system: from placenta
- Cardinal system: from head, neck, body wall, and limbs of embryo itself
Describe the pathway of the vitelline veins in a 26-day old embryo
Arising from the yolk sac, enterying embryo via yolk stalk, the veins pass thru the septum transversum to empty into the sinus venosus.
What are the adult derivatives of the vitelline veins?
- Portal system of veins (right)
- Hepatic sinusoids & hepatic veins (right)
- Portion of inferior vena cava (IVC) (right)
NOTE: The left vitelline vein degenerates so that’s why these structures all say (right)
The umbilical veins drain into the ___.
At what wk does the right vein degenerate?
Sinus venosus; wk 8
During fetal life, where does the left umbilical vein carry blood?
It carries oxygenated blood and empties into the ductus venosus, which then empties into the IVC.
Thus blood processed in the placenta bypasses the liver thru the ductus venosus, which in adult livers is the ligamentum venosum.
What are the 5 kinds of cardinal veins?
Anterior, common, posterior, subcardinal, and supracardinal.
Where are the cardinal veins located relative to each other?
Anterior and posterior drain cranial and caudal portions of embry respectivly, and are united to each other by the common cardinal vein.
The sub and supracardinal veins replace and supplement the posterior cardinal veins.
What are the adult derivatives of the cardinal veins?
Anterior: SVC, jugular and brachiocephalic veins,
Posterior, sub, and supracardinal: portions of IVC, azygous, hemiazygous, and intercostal veins
What are the 4 sources the IVC is derived from?
- Infrarenal: right supracardinal
- Renal: Sub and supracardinal anastomosis
- Suprarenal: right subcardinal
Hepatic: right vitelline
Describe these anomalies of the vena cavae:
- Double SVC
- Left SVC
- Double IVC
- Left anterior and common cardinal veins persists
- Left anterior and common cardinal veins persist while right anterior and common cardinal veins degenerate
- The left supracardinal vein persists
There are 6 primary lymphatic sacs by wk 8, what are their names and their adult derivatives?
- Paired jugular lymph sacs: cervical and axillary lymph node grps
- Paired iliac lymph sacs: inguinal and iliac lymph node grps
- Single retroperitoneal lymph sac: aortic and preaortic lymph node grps
- Single cisterna chyli: cisterna chyli.
What are the 2 major lymph ducts of the adult and their embryonic derivations?
- Right lymphatic duct: from cranial portion of the right duct
- Thoracic duct: from caudal portion of right duct, the anastomosis, and cranial portion of the left duct
What is cystic hygroma?
Persisten lymphatic sac or failure of lymph vessels to connect
What are the 4 major events that happen to the baby at birth with its first breaths?
- Umbilical vein and ductus venosus close to become the ligamentum teres and ligamentum venosum respectively
- Foramen ovale closes functionally and forever at 3 months
- Ductus arteriosus begins to close and becomes the ligamentum arteriosum, but is fully closed at 3 mo
- Umbilical a.’s close superior to urinary bladder
