Cardiovascular System Flashcards
Early Phases of the Embryo
Diffusion from fluid secreted by uterine gland
When Embryo increases in size and complexity
diffusion system of nutrition is insufficient. There is an urgent need for a circulatory system that can carry nutrients and oxygen to the tissues and remove carbon dioxide and other waste products of normal metabolism
Angiogenesis
Process of blood vessel development
Mesoderm –>
mesenchyme (pluripotent cells) -> angioblastic tissue (hemangioblasts)-> cardiovascular system
Cardiogenic Field
Horseshoe-shaped structure. Blood forming cavities in the visceral mesoderm -> coaslesce and form the primitive heart, blood vessels, and blood cells.
Cardiogenic Field –>
Endocardial tubes —> cardiac tube
Endocardial tubes
tubes first composed of only endothelial cells, make contact caudally with the developing venous system.
Cardiac Tube
caudal portion fuses and becomes surrounded by myoblasts to form the myocardium. Composed of bulbus cordis, ventricle and atrium
Loop Formation
In conjuction with a relatively complex division of the cardiac tube into four chambers, will result in the formation of the blood pumping organ necessary for the survival.
Aortic Arches
Series of 6 paired embryological vascular structures that give rise to the great arteries of neck and head. Defects in aortic arches = defects of the great arteries of the body
Primitive atrium divided into
left and right atria
Primitive ventricle divided into
left and right ventricles
Truncus arteriosus divided into
outflow tracts of aorta and pulmonary trunk
Heart Development step 1
the primary atrial septum formed and development of the interventricular septum begun
Heart Development step 2
Primary atrial septum has fused with the endocardial cushions, and a secondary foramen has been formed
Heart Development step 3
The secondary atrial septum formed and a passage (foramen ovale) between primary and secondary septa connects the right and left atria. Interventricular septum fused with endocardial cushions
Atrial Partitioning (1)
Ostium primum allows the initial passage of blood from the right to the left atrium as the primary atrial septum grows.
Atrial Partitioning (2)
When ostium primum closes, it is replaced by the ostium secundum. Blood is still able to pass from the RA to the LA
Atrial partitioning (3)
The secondary septum grows to the right of the primary septum and the primary septum serves as the valve for the foramen ovale in the secondary septum, preventing return of blood into the right atrium
Atrial Partitioning After Birth
Lungs will expand with first breaths which creates a sudden blood pressure drop in pulmonary circulation. This pushed the primary septum against the secondary one (physiological closure), These fuse and the foramen ovale becomes the fossa ovalis (anatomical closure)
Truncus arteriosus
gets divided into ascending aorta and pulmonary trunk by a sprial aortico-pulmonary septum. The spiral formation of the septum ensures that blood form the right ventricle flows into the pulmonary trunk and that the blood from the left ventricle flows into the ascending aorta.
Transposition of the great vessels
When the septum is straight, causes this transposition. Deoxygenated blood from the right ventricle flows into the ascending aorta and the highly oxygenated blood from the left ventricle flows into the pulmonary trunk. Incompatible with life
Fetal blood circulation
Designed for in utero aqueous environment so lungs get little blood. 3 shuts: Ductus venosus, Foramen ovale, and Ductus arteriosus (->ligamentum arteriosum). All must close soon after birth.
Placenta to umbilical vein to ductus venosus in liver to heart and foramen ovale to arch of aorta and ductus arteriosus to descending aorta to umbilical arteries.
Cardiovascular System functions
Maintenance of adequate blood flow (cardiac output)
Delivery of oxygen, nutrients, hormones, electrolytes, and water to peripheral tissues
Removal of carbon dioxide and other metabolic waste products
Maintenance of normal thermoregulation
Maintenance of normal glomerular filtration rate (GFR) and urine output
Microcirculation pattern
Artery -> Arteriole -> metarteriole -> capillaries -> venule -> vein
Heart Tunics
Endocardium, Myocardium, Epicardium
Pericardial sac
Epicardium + Pericardium. The epicardium is the visceral pericardium which touches the heart. Then there is the outer layer of parietal pericardium
Endocardium
Forms the inner lining and the valves. It is the equivalent to the tunica intima of BV. Endothelial cells on the inner most surface. Direct contact with blood and it important in hemostasis. There are 3 layers: endothelium, basal lamina, subendothelial connective tissue. Also contains part of the conductive system and purkinje fibers
Cardiac Skeleton
four dense bands of fibrous connective tissue encircle the base of the pulmonary trunk, aorta, and the AV valves. This provides structural support to the heart.
Fibrous Trigon
Triangular mass of fibrous connective tissue. Connects the aortic a. ring and the L and R atrioventricular rings. This area undergoes osseous differentiion and forms the Os Cordis- primarily seen in cattle
Cardiomyocytes
Cross striated, central single nucleus. Intercalated disks with desmosomes and gap junctions. Lipofuscin, SR, many mitochondria.
Myocardium
LV myocardial thickness is 2-4 times thicker than the right in adults due to higher pressure on left side. Involuntary striated muscle arranges in sarcometes. Branched fibers connect via intercalated discs. Contain a large number of mitochondria.
Purkinje cells are modified cardiomyocyte that function in conduction.
Epicardium
Outer surface of the heart is the visceral pericardium. THe surface is covered by mesothelium (simple squamous epithelium) a thin layer of dense connective tissue and depending on location, a variably thick layer adipose tissue with blood vessels (coronary arteries and veins). Is contiguous with the endocardium at the level of the endocardial cushions
Tunics of Vessels
Tunica Intima, tunica media, tunica adventitia
Tunica Intima
Endothelium, internal elastic membrane, subendothelial connective tissue
Tunica media
Smooth muscle and elastic lamellae/fibers
Tunica adventitia
Collagen, may contain blood vessels, nerves, capillaries.
Vascular endothelium
Plays a role in hemostasis, modulates perfusion, role in inflammation
Elastic Artery
Aorta. All three tunics exist: tunica intima is endothelium and loos CT. Tunica media consists largely of repeating elastic lamellae. Tunica adventitia contains vaso vasorum
Vaso vasorum
to assist in supplying nutritional needs of thick tunica media
Muscular Arteries
Femoral Artery. Tunica media is primarily smooth muscle and is the thickest. Generally have a round appearance
Vascular smooth muscle
Smooth muscle cells are circumferentially arranged within the tunica media. This regulates diameter and tone. (vasodilation/vasoconstriction)
Arterioles
1-3 layers of smooth muscle cells. Greatest effect on BP. Nuclei bulge into the lumen and they have a round appearance. No internal elastic membrane in the smallest arterioles with one smooth muscle cell.
Metarteriole
Terminal vessel that has precapillary sphincters that can regulate flow to capillary bed
Capillaries
Thin walled tubules of mesenchymal origin. In a cross section they are made of only one endothelial cell rolled into the tube. Represent the site of exchange between blood and surrounding tissue. The diameter is 7-9 um.
Composed of simple squamous cells which roll to produce a tube
Capillary wall permeability
Permeable to O2, Co2, ions, H2O, glucose, amino acids, fatty acids, vitamins, hormones.
Impermeable to proteins and blood cells.
Pericytes
Mesenchymal-like cells that wrap around endothelium of capillaries and venules. They communicate with endothelial cells by physical contact and paracrine signaling.
Help maintain homeostatic and hemostatic functions in the brain and sustain BBB. Proliferate after injury and are stem cell source. Important in angiogenesis for new vessel formation.
Continuous Capillary
Most common. Found in muscle, brain, bone, lung. BBB, Blood-testis barrier.
Fenestrated Capillary
gaps 10-100 nm. In tissues with substantial fluid exchange. Choroid plexus, ciliary process, glomerular capillaries
Sinusoidal Capillary
Hepatic and splenic sinusoids. Large molecules can exit (RBCs in spleen). Lumen is enlarges and irregular (20-40 um). Lining endothelium is discontinuous and fenestrated. basal lamina may be absent.
Podocytes
Lining the Bowman’s Capsules (nephrons). Help prevent proteins and other large molecules from being filtered. Their foot processes (pedicels) extend and wrap around the capillaries of the glomerulus to form the filtration slits. The pedicels increase the area of the cells enabling efficient ultrafiltration
Venules
Postcapillary venules. Very “leaky” vessels. No smooth muscle. Leukocyte diapedsesis possible here. 5mm Hg pressure in vessel.
Veins
Large, wide lumen. Thin walls in comparasin to same size arteries. Valves present. Thin tunica media and adventitia is thickest. Large veins may have vasa vasorum. May be collapsed in histological sections.
Lymphatic vessels
Complementary to the CVS. Transport lymph throughout the lymphatic system. Valves are present. Freely anastomose with one another. Lines by endothelial cells and have thin layer of smooth muscle. Adventitia that bind the lymph vessels to the surrounding tissue.
Very thin wall, very low pressure, may contain valves. No RBS in lymph so it is clear.
