Module 2 Endothelial Cells Flashcards
Name three structural features of endothelial cells and briefly state how each contributes to their function.
✅ Answer:
Flat, cobblestone shape – minimizes resistance to blood flow.
Glycocalyx – regulates permeability, senses shear, sequesters molecules.
Tight junctions – maintain vascular integrity and barrier function.
What is the glycocalyx composed of, and how does it help prevent thrombosis?
✅ Answer:
Composed of proteoglycans with glycosaminoglycans (e.g., heparan sulfate, hyaluronan).
Heparan sulfate binds antithrombin III, inhibiting thrombin → reduces clot formation.
Describe the function of Weibel-Palade bodies and name two molecules they store.
✅ Answer: Weibel-Palade bodies are endothelial-specific storage granules.
They store:
von Willebrand Factor (vWF) – promotes platelet adhesion.
tPA – breaks down clots via fibrin degradation.
Differentiate between pinocytosis and caveolae-mediated endocytosis in endothelial cells.
✅ Answer:
Pinocytosis: nonspecific uptake of fluids and solutes.
Caveolae: specialized vesicles for selective transport (e.g., LDL, enzymes) using caveolin.
Name one mechanical and one biological function of the glycocalyx.
✅ Answer:
Mechanical: Senses shear → signals via transmembrane proteins to cytoskeleton.
Biological: Sequesters antithrombin on heparan sulfate → inhibits coagulation.
What is the function of Piezo1 in endothelial cells?
✅ Answer: Piezo1 is a mechanosensitive ion channel that mediates Ca²⁺ influx in response to shear or pressure, regulating:
Endothelial cell alignment,
Blood pressure,
Barrier integrity.
Outline the sequence of events in endothelial mechanotransduction via the PECAM-1/VE-Cadherin/VEGFR2 complex.
✅ Answer:
Shear stress alters PECAM-1 conformation.
Signal is transmitted via VE-Cadherin to VEGFR2.
VEGFR2 activates PI3K/Akt, leading to:
Antioxidant,
Anti-inflammatory,
Antithrombotic gene expression.
What are two types of endothelial cell-cell junctions, and which proteins are associated with them?
✅ Answer:
Tight junctions: Occludin, Claudin-5.
Adherens junctions: VE-Cadherin, Nectin.
How do selectins and integrins contribute to leukocyte transmigration during inflammation?
✅ Answer:
Selectins mediate tethering and rolling.
Integrins mediate firm adhesion and arrest, enabling leukocytes to enter tissues.
List two vasodilators and two vasoconstrictors secreted by endothelial cells.
✅ Answer:
Vasodilators: Nitric oxide (NO), Prostacyclin (PGI₂)
Vasoconstrictors: Endothelin-1, Thromboxane A2 (TXA2)
Name two ways the endothelium inhibits thrombosis.
✅ Answer:
NO and PGI₂ inhibit platelet activation.
Heparan sulfate binds antithrombin III, blocking thrombin.
List four factors that can cause endothelial dysfunction.
✅ Answer:
Oxidative stress (ROS)
High blood pressure (hypertension)
High glucose (diabetes)
Smoking/toxins
How does endothelial dysfunction lead to atherosclerosis?
✅ Answer:
Dysfunction disrupts barrier → lipids infiltrate the intima.
Promotes inflammation, adhesion of leukocytes, and clotting, leading to plaque formation.
Describe one biological and one mechanical mechanism by which the glycocalyx has a signalling role on endothelial cells.
✅ Model Answer (2 marks):
Mechanical: Shear stress deforms heparan sulfate → activates integrins → cytoskeletal rearrangement.
Biological: Heparan sulfate binds antithrombin III → inhibits thrombin → anticoagulant response.
Describe how endothelial cells regulate vascular tone through paracrine signalling.
✅ Model Answer:
ECs secrete NO, which diffuses to smooth muscle cells → activates cGMP → causes vasodilation. This is a paracrine mechanism regulating vessel diameter.
