Vascular System Histology Flashcards
Cardiovascular system is divided into:
systemic and peripheral circulation and pulmonary circulation
vasculogenesis is what?
development of blood vessels from the coalescence of hemangioblasts
Where do hemangioblasts arise from?
BLOOD ISLANDS
All major vessels form via
vasculogenesis
Angiogenesis is
vessel formation via branches arising from existing vessels
When in development does vasculogenesis begin?
Week 3
Where does vasculogenesis begin?
XE splanchnic mesoderm surrounding the yok sac
Where does vasculogenesis spread into after the XE splanchnic mesodern?
lateral plater mesoderm
Where do blood islands form first?
the yolk sac
What derm layer do blood islands come from?
Mesoderm
Blood islands form what what two cell lines
Vascular precursor cells (angioblasts) and hematopoietic stem cells
FGFR is what?
fetal growth factor – receptor
What binds to FGFR?
FGF2
FGF2 promotes what?
hemangioblast development
VEGF acts via how many blood island receptors? What are they?
- VEGF-R1 and VEGF-R2
VEGF-R1 is located in what cells and causes what?
peripheral cells; produce angioblasts which ultimately become the endothelium of blood vessels
VEGF-R2 is located in what cells and causes what?
central cells; produces hematopoietic stem cells
Named three major signaling pathways involved in angiogenesis
1) VEGF-VEGF receptor pathway
2) Notch receptor pathway
3) Tie receptor-angiopoietin (Ang) pathway
WHen does VEGF regulate formation of addtional vasculature via angiogenesis?
Following formation of vascular bed
What does Angiopoietin 1 (ANG1) do?
interacts with endothelial cell receptor TIE2
What does Angiopoietin 1 (ANG1) recruit during interaction with TIE2?
periendothelial cells to smooth muscle cells in large vessels to organize mature blood vessels
VEGF, Platelet-derived growth factor (PDGF) and TGF-β do what?
Regulate maturation and remodeling of vasculature
Notch receptor pathway is induced by what?
VEGF
Notch receptor pathway specifies what to develop?
Arteries via expression of ephriB2 ligand
What gene controls vein development?
EPHB4 gene
What gene controls lymphatic vessel differentiation?
PROX1
What is the aorta-gonad-mesonephros region (AGM) and what do they eventually colonize?
AGM is location of where fetal hematopoietic stem cells arise. AGM eventually colonize the liver (2-7 months of development)
After development month 7, where does hematopoiesis move from and to?
Hematopoiesis moves from liver to the bone marrow
Tumors promote what?
Angiogenesis
What is the heart at most basic level?
A folded endothelial tube with thickened wall acting as a pump
The heart has what three layers?
endocardium, myocardium and epicardium
Endocardium is:
endothelial lining and subendothelial connective tissue
Myocardium is:
functional syncytium of striated cardiac muscle fibers forming three types of cardiac muscle
Epicardium is:
visceral layer of the pericardium, low-friction surface lined by mesothelium in contact with the parietal pericardial space
Cardiac cell types:
contractile, myoendocrine, nodal
contractile cells do what?
contract to move blood
myoendocrine cells do what?
produce atrial natriuretic factor that stimulates diuresis and excretion of sodium in urine by increasing glomerular filtration rate and reduces blood volume
nodal cells do what?
regulates contraction of the heart at the sinoatrial node & atrioventricular node
Arteries are organized into what three major layers?
Tunica intima (inner most layer), tunica media, tunica externa/adventitia (outer most layer)
Arteries are categorized into what three major types?
large elastic (conducting) arteries, medium muscular arteries and small arteries and arterioles
large elastic (conducting) arteries do what?
Receive blood from the heart under high pressure and keep blood circulating continuously while the heart is pumping intermittently
large elastic (conducting) arteries have tunica media that is what kind of French window?
Fenestrated = hole
Examples of large elastic arteries:
aorta and largest branches: brachiocephalic, common carotid, subclavian and common iliac arteries
What doe medium muscular arteries do?
Allow selective distribution of blood to different organs in response to functional needs (3 mm diameter).
The tunica media of medium muscular artiers has reduced or increased elastic components?
Reduced
The tunica media of medium muscular artiers has reduced or increased smooth muscle fibers?
Increased
Examples of medium muscular arteries:
Radial, tibial, popliteal, axillary, splenic, mesenteric and intercostal arteries
Arterioles/Resistance vessels do what?
Are the resistance vessels and are the major determinants of systemic blood pressure. Final branches of arterial system. Regulate distribution of blood to different capillary bed by vasoconstriction/dilation
Arterioles have what type of smooth muscle?
Circularly arranged smooth muscle
Arterioles are lined by what type of cell?
Squamous endothelial cells with smooth muscle in the wall
Microvascular bed of a tissue is:
capillaries, arterioles and post capillary venules
Where does microcirculation occur?
the microvascular bed
Capillary bed contains:
slightly larger capillaries (preferential/thoroughfare channels) and small capillaries (true capillaries)
How many capillaries are found in the capillary bed?
10-100 capillaries functioning together
Blood flow is _______ at thoroughfare channels
continuous
Blood flow is _______ at true capillaries
intermittent
What is the functional unit of the cardiovascular system?
Capillaries
Capillaries consist of what layers?
Tunica intima and endothelium only
What are the three types of capillaries?
continuous, fenestrated and sinusoid
continuous capillaries are:
lined w/ epithelium with tight junctions and basal lamina with pericytes. These capillaries keep RBCs IN.
fenestrated capillaries are:
have pores or fenestrae (GI & kidney). These allow some exchange.
sinusoid capillaries are:
discontinuous. Have an incomplete endothelial lining and basal lamina. Many gaps and holes between and within the endothelial cells (liver and spleen).
Where does the venous system start?
at end of capillary bed
Post capillary venules are preferred site of migration of what?
Blood cells INTO tissues via diapedesis
Vein have relatively ____ walls compared to arteries of same diameter
thin
Vein have _____ distensibility (compliant). Volume of blood within veins relative to volume of vein is _____.
high/large
What distinguishing structure do veins have and what does this structure do?
Veins have valves. Valves prevent blood reflux
Vasculitis is what?
inflammation of blood vessels
Vasculitis causes what?
thickening, weakening, narrowing and scaring of blood vessels
Three main medium sized blood vessel disorders are:
Buerger’s disease, Plyarteritis nodosa, Kawasaki’s disease
Buerger’s disease is:
chronic inflammatory infiltration of the arterial wall and thrombus in vascular lumen
Polyarteritis nodosa is:
Perivascular chronic inflammatory rxn, fibrinoid necrosis of the tunica intima predisposes to thrombosis, macrophages invade necrotic tunica intima resulting in breakdown of the internal elastic lamina.
Small vessel disorders:
wegener’s granuloma, churg-strauss syndrome, Henoch-schonlein pupura
Lymphatic capillaries are NOT found in what:
cartilage, bone, epithelia, CNS and placenta
What does the lymphatic system do?
conduct immune cells and lymph to lymph nodes, b. Remove excess fluid accumulated in interstitial spaces, c. Transport chylomicrons, lipid-containing particles, through lacteal lymphatic vessels inside the intestinal villi
What do lymphatic capillary walls lack?
Complete basal lamina. Endothelium only
List the two forms of lymphatic drainage
Intrinsic and Extrinsic
Intrinsic lymphatic drainage is:
Smooth muscle (Lymphangions ) of lymphatic wall contracts
Lymphangions behave as what?
automatic pump
Lymphatic vessel segments are separated by what?
valves
Extrinsic lymphatic drainage is:
External contraction of the surrounding muscles during exercise, arterial pulsations and compression of tissues forces move the lymph and cause pumping action.
edema is what?
accumulation of excess lymphatic fluid within the tissue space.
List three edema disorders:
Lymphedema, Filariasis/elephantiasis, chylous ascites/chylothorax
Lymphedema
caused by defect in transport of lymph due to abnormal vessel development or damaged lymphatics
Filariasis
parasitic infection of lymphatic vessels by Wuchereria bancrofti or Brugia malayi worms. Transmitted by mosquitos. Causes damage to lymphatic vessels with chronic lymphedema of legs and genitals. Tropical countries.
chylous ascites/chylothorax
accumulation of high fat containing fluid/chyle, in abdomen or thorax as a result of trauma, obstruction or abnormal development of lymphatic vessels.
What do endothelial cells produce?
vasoactive substances able to induce contraction and relaxation of smooth muscle vascular wall
Two vaso relaxation substrates:
Nitric oxide and Prostacyclin
Prostacyclin prevents what?
Platelet adhesion and clumping (no blood clots)
Endothelin 1 is what?
A very potent vasoconstrictor peptide
what is more permeable, venous end cells or arterial end cells?
Venous end cells
Atherosclerosis is a thickening and hardening of artery walls due to plaque build-up in what artery layer?
tunica intima
Atherosclerosis is not seen in _____?
Veins
Atherosclerosis causes what?
myocardial infarction, stroke and ischemic gangrene
Atherosclerosis is categorized as what kind of disease?
chronic inflammatory disease
Atherosclerosis correlates with serum levels of what?
cholesterol and low-density lipoprotein
