Blood Vessels II Flashcards
What type of intermediate filaments does an endothelial cell have?
Desmin and vimentin
What do endothelial cells secrete in their basal lamina?
- Type I, III, IV, V collagens
- Fibronectin and laminin
- Coagulants and anticoagulants
What is the average lifespan of an endothelial cell?
150-180 days
- relatively slow renewing
Is intact endothelium thrombogenic?
no0o
What do endothelial cells share their basal lamina with?
Pericytes
Is a pericyte’s nuclei heterochromatic or euchromatic?
Heterochromatic
What are the functions of pericytes?
- some capable of contraction to regulate blood flow
2. can be stem cells for endothelial and smooth muscle cells after injury
What are the most common type of capillaries?
Continuous capillaries
Where are continuous capillaries found?
- Muscle system
- nervous system
- connective tissue
- exocrine system
- pancreas
How would you describe continuous capillaries?
- endothelial cells are sealed by tight junctions
- permit the passage of small molecules
Where are fenestrated capillaries found?
- pancreas
- intestines
- endocrine glands
What is unique about the fenestrated capillaries found in the renal glomerulus?
-there is not a diaphragm
What are the size of a typical fenestrae?
60-80 nm
How would you describe fenestrated capillaries?
Continuous, but thin endothelium and basal lamina, covered by a diaphragm
-specialized for rapid exchange
Where are sinusoidal capillaries found?
-endocrine glands
Where are discontinuous sinusoids found?
- liver
- bone marrow
Where are venous sinusoids found?
- spleen
How would you describe a sinusoid?
- irregular blood channels that conform to the shape of the structure they line
- large gaps btwn endothelial cells permits enhanced exchange btwn blood and tissue
In which structure are the diaphragms larger, Discontinuous sinusoids or fenestrated capillaries?
discontinuous sinusoids
Small pores of capillaries:
- what are their size
- where are they found
- what do they allow to pass
- 9-10 nm
- occluding junctions (tight)
- water and small hydrophilic molecules
Large pores of capillaries:
- what are their size
- what occurs through them
- 50-70 nm
2. transcytosis by vesicles
Which are more numerous - veins or arteries?
veins - 70% of total volume
Which has more vasa vasorum and lymphatics - veins or arteries?
veins
which has more collagen and less elastic substance and smooth muscle - veins or arteries?
veins
In what size veins are valves in? what composes a valve?
small and medium veins
-infolding of intima with an elastic core
Describe a large vein:
- Intima
- Media
- Adventitia
- Intima
- Continuous Endothelium and basal lamina
- Subendothelial CT (no internal elastic lamina) - Media – frequently incomplete or absent
- CT, SM - Adventitia – largest, 95% of thickness
- SM in long bundles – defining feature
- Well developed vasa vasorum and lymphatic’s
Describe a medium and small vein:
- Intima
- Media
- Adventitia
- Intima
- Continuous endothelium and basal lamina
- Complete internal elastic laminae only found in veins of the leg
- some valves - Media – poorly developed except in the limbs
- CT fibers
- 2-3 layers circumferential SM - Adventitia – thickest tunic, no smooth muscle
Collagen layers with fibroblasts, lymphatic’s, vasa vasorum, elastic fibers
Describe a venule:
- Intima
- Media
- Adventitia
- Intima
- Endothelium - Media
- Sparse CT, few SM - Adventitia
- Some Collagen
How would you compare venules to arterioles?
- larger diameter
2. no smooth muscle
What are some functions of venules?
- allow exchange
- leukocyte emmigration
In response to what two subtances, can venules become leaky?
histamine and serotonin
What is the diameter of pericytic venules and what do they resemble?
- 10-50 microns
2. resemble large capillaries
what is the function of muscular venules?
-receive blood from pericytic venules and accompany arterioles
Describe the adventitia of muscular venules?
1-2 layers of smooth muscle and thin adventitia
What are portal systems?
- carry blood from one capillary to another
What are 3 examples of portal systems?
- hepatic portal vein btwn intestines and liver
- hypophyseal portal veins of the pituitary
- efferent arterioles of the renal cortex
What are arteriovenous anastomoses?
- direct cross connections btwn arterioles and venules
- allows bypass of a capillary bed
- smooth muscle cells form a sphincter which regulates blood flow
How would you describe lymphatic vessels?
- large lumens, thin walls, irregular shapes
- similar to veins but more irregular
- branch parallel to capillaries and veins
What is the basal lamina of lymphatic vessels like?
-discontinuous or absent
How are lymphatic vessels held open?
elastic anchoring filaments
Are RBCs found in lymphatics?
N0OO0O
