11.21 B Flashcards
What kind of epithelium lines blood vessels?
simple squamous
White blood cells typically exit the vascular system at what point?
in the post-capillary venules
Elastic arteries are also known as what?
larger arteries
Muscular arteries are also known as what?
medium-sized arteries
Where in the vascular system does hydrostatic pressure drop the most?
in the arterioles
The innermost of the three layers of arterial walls is called what?
tunica intima
The outermost of the three layers of arterial walls is called what?
tunica externa or tunica adventitia
The middle layer of arterial walls is called what?
tunica media
Describe the tunica intima.
- the endothelial lining as well as the subendothelial basement membrane
- loose connective tissue
- a dense layer of elastic fibers
The dense layer of elastic fibers in the tunica intima is called what?
the internal elastic lamina
Describe the tunica media.
concentric layers of smooth muscle, collagen fibers, and discontinuous elastic sheaths
The discontinuous elastic sheaths that help constitute the tunica media are called what?
the external elastic lamina
Describe the tunica externa.
connective tissue with it’s own vascular supply and innervations
What are vasa vasorum?
blood vessels supplying the tunica externa of larger vessels
What are nervi vasorum?
nerves that innervate the tunica externa of large blood vessels
What are conducting arteries?
large (aka elastic) arteries that conduct blood from the heart
What are distributing arteries?
medium-sized arteries that allow selective distribution of blood to different organs in response to functional needs
What feature of the vascular system ensures continuous blood flow despite intermittent pumping of the heart?
the elastic recoil of large arteries during diastole
When do large arteries recoil?
during diastole
How does the histology of elastic arteries compare to those of muscular arteries?
muscular arteries often have a more prominent internal elastic lamina as well as fewer elastic sheaths and more smooth muscle fibers
What are resistance vessels?
arteries that regulate the distribution of blood to different capillary beds by vasoconstriction and vasodilation
What type of blood vessel is a major determinant of overall systemic blood pressure?
arterioles
How thick is the tunica media of arterioles?
they typically have 2-5 concentric layers of vascular smooth muscle
Why do veins tend to appear more irregularly shaped than arteries?
because they have less smooth muscle and elastic tissue because they aren’t under the hydrostatic force generated by the heart
What are the three types of capillaries?
continuous, fenestrated, and discontinuous
Where are continuous capillaries found?
muscle, brain, thymus, and lung
Where are fenestrated capillaries found?
sites of fluid transport like intestine and kidney
Where are discontinuous capillaries found?
sites of macromolecule exchange like liver, spleen, and bone marrow
Which types of capillaries have an intact basement membrane?
continuous and fenestrated
What are caveolae?
vesicles that transport substances through the cytoplasm of endothelial cells lining capillaries
What are sinusoids?
the gaps found in discontinuous capillaries
Caveolae are coated with what protein?
caveolin
What are pericytes involved in?
- tight junction formation
- vesicle trafficking in endothelial cells
- regulation of blood flow
- angiogenesis
Loss of pericytes in the CNS result in what?
loss of the blood brain barrier and neurodegenerative disorders
What types of blood vessels tend to be lined by pericytes?
arterioles and venules
How do the tunica of veins compare to those of equal sized arteries?
- no distinct internal elastic lamina in veins
- tunica media of veins are typically thinner
What is prostacyclin?
a compound produced by endothelial cells to limit adhesion of platelets to the cells, preventing clotting
How do endothelial cells modulate smooth muscle activity?
by producing nitric oxide (a muscle relaxant) and endothelin 1 (a muscle contractor)
What is endothelin 1?
a muscle contractor produced by endothelial cells to regulate smooth muscle activity
What is Tissue Factor?
a compound that initiates blood clotting
What are some active roles of endothelial cells?
- modulate smooth muscle activity
- produce prostacyclin
- trigger blood coagulation
- traffic inflammatory cells
- control vascular cell growth
How does oxidative stress result in atherosclerosis?
it causes endothelial dysfunction and thus reduced NO availability, which leads to lipid deposition, vasoconstriction, platelet aggregation, luekocyte adhesion, etc.
What are some risk factors for atherosclerosis?
smoking, diabetes, aging, obesity, dyslipidemia, hypertension
What is atheroscelerosis?
deposition of fatty material in the wall of the vessel to form a lesion
Atheroscelerosis typically involves what sorts of blood vessels?
large arteries
Atheromas are responsible for what health issues?
MI, cerebral infarction or stoke, and gangrene
Atheromas in the peripheral vasculature can lead to what problem?
gangrene
How do cells and macromolecules enter lymphatic capillaries?
muscular contractions open spaces between lymphatic endothelial cells which lack tight junctions
What is vasculogenesis?
creation of a new vascular network
What is angiogenesis?
sprouting of new vasculature from an existing network
What is VEGF?
vascular endothelial growth factor, required for vasculogenesis and angiogenesis
What are angiopoietins?
compounds required for vasculogenesis and angiogenesis
What is the main regulator of hypoxia-induced angiogenesis and vasculogenesis?
HIF-1
What is HIF-1?
a transcription factor that regulates hypoxia-induced angiogenesis
What are the target genes of HIF-1?
EPO, VEGF, IGF2, and GLUT
HIF-1 binds what element of DNA?
the hypoxia response element, HRE
