Cell biology - Endothelial Cells
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Questions and Answers

Veins have ______ walls and large lumens.

thinner

Capillaries are made up of a ______ cell layer.

single

Fenestrated capillaries are common in the small ______.

intestine

The primary function of pericytes is to stabilize the capillary ______.

<p>structure</p> Signup and view all the answers

PDGF acts as a ______ that induces movement in nearby cells.

<p>chemokine</p> Signup and view all the answers

Angiopoietin-1 (Ang-1) binds to______ receptors on endothelial cells.

<p>Tie-2</p> Signup and view all the answers

Continuous capillaries are characterized by a complete endothelial lining with ______ junctions.

<p>tight</p> Signup and view all the answers

Sinusoid capillaries have large openings that allow blood cells to ______ into the blood supply.

<p>enter</p> Signup and view all the answers

Angiogenesis is the growth of new blood vessels from the existing ______.

<p>vasculature</p> Signup and view all the answers

Vasculogenesis is the process of de novo blood vessel formation by ______.

<p>endothelial cells</p> Signup and view all the answers

The pulmonary circulation results in deoxygenated blood leaving the heart and travelling to the ______.

<p>lungs</p> Signup and view all the answers

The systemic circulation is where oxygenated blood leaves the heart and travels through ______ around the body.

<p>arteries</p> Signup and view all the answers

Blood vessels also help to remove ______ from tissues to the lungs.

<p>CO2</p> Signup and view all the answers

In embryonic development, tissues are maintained by ______ of gases, nutrients and metabolites.

<p>diffusion</p> Signup and view all the answers

The cardiovascular network is the first organ system to develop in the ______.

<p>embryo</p> Signup and view all the answers

Pathological conditions like tumor angiogenesis impact normal ______ processes in the body.

<p>physiological</p> Signup and view all the answers

Endothelial cells are derived from ______ stem cells.

<p>angioblast</p> Signup and view all the answers

Endothelial cells are simple, ______ epithelia.

<p>squamous</p> Signup and view all the answers

The exchange of materials occurs across the capillary ______.

<p>endothelium</p> Signup and view all the answers

Endothelial cells produce ______ gas to help dilate blood vessels.

<p>NO</p> Signup and view all the answers

Fluid filtration occurs in structures such as the ______ of the kidney.

<p>glomerulus</p> Signup and view all the answers

Veins can develop ______ due to weakness in their walls and valves.

<p>varicose veins</p> Signup and view all the answers

The thickest layer of arteries is the ______ muscle layer.

<p>smooth</p> Signup and view all the answers

Endothelial cells act as a semi-permeable barrier between plasma and ______.

<p>tissue</p> Signup and view all the answers

Oxidised LDL contributes to endothelial cell ______.

<p>injury</p> Signup and view all the answers

The migration of monocytes and lymphocytes occurs into the ______ interna.

<p>tunica</p> Signup and view all the answers

Monocytes convert into ______ when they migrate into the tissue.

<p>macrophages</p> Signup and view all the answers

Foam cells and platelets encourage the migration and proliferation of smooth muscle cells to the ______.

<p>intima</p> Signup and view all the answers

A protective fibrous cap normally forms between the fatty deposits and the artery ______.

<p>lining</p> Signup and view all the answers

Ruptures of the fibrous cap expose thrombogenic material, such as ______.

<p>collagen</p> Signup and view all the answers

Plaques can block the blood vessel entirely or move into the ______ and block smaller vessels.

<p>bloodstream</p> Signup and view all the answers

If it is a myocardial infarction, the results can be ______.

<p>fatal</p> Signup and view all the answers

Endothelial cells (ECs) line all blood ______.

<p>vessels</p> Signup and view all the answers

Endothelial cells are activated by the presence of ______, released by cells in low oxygen environments.

<p>VEGF</p> Signup and view all the answers

The transition from the prevascular to the vascular phase is referred to as the 'angiogenic ______'.

<p>switch</p> Signup and view all the answers

Perivascular cells such as ______ stabilize capillaries.

<p>pericytes</p> Signup and view all the answers

Angiogenesis occurs by two processes; sprouting angiogenesis and ______.

<p>intussusception</p> Signup and view all the answers

Lack of oxygen and nutrients prevents the growth of tumors in excess of ______ mm in diameter.

<p>1-2</p> Signup and view all the answers

EC tip cells migrate towards the increasing ______ concentration gradient.

<p>VEGF</p> Signup and view all the answers

Monoclonal antibodies such as Bevacizumab block tumor cell-derived ______, impairing the development of new vessels.

<p>VEGF-A</p> Signup and view all the answers

Effective inhibition of tumor angiogenesis might arrest or halt tumor ______ but would not eradicate the tumor.

<p>progression</p> Signup and view all the answers

Atherosclerosis is a multistep process ranging from endothelial ______ to plaque development.

<p>dysfunction</p> Signup and view all the answers

Cholesterol is carried around the body by low density ______ (LDLs).

<p>lipoproteins</p> Signup and view all the answers

When endothelial cells engulf LDL, they oxidize it to a product called ______ LDL.

<p>oxidized</p> Signup and view all the answers

LDLs are usually taken out of circulation by the ______.

<p>liver</p> Signup and view all the answers

Angiogenesis is the formation of new blood vessels from the pre-existing ______.

<p>vasculature</p> Signup and view all the answers

Hypoxia, or lack of oxygen, causes cells to produce ______, which is a key factor in promoting angiogenesis.

<p>VEGF</p> Signup and view all the answers

When O2 is scarce, unmodified HIF1α migrates to the ______ where it promotes the expression of VEGF.

<p>nucleus</p> Signup and view all the answers

Intussusceptive angiogenesis involves the ______ of an existing blood vessel into two.

<p>splitting</p> Signup and view all the answers

The ability of an enzyme called prolyl hydroxylase-2 (PHD2) to add an O2 molecule to proline amino acids in ______ is essential for sensing oxygen levels.

<p>HIF1α</p> Signup and view all the answers

Endothelial cells line the inner surface of ______.

<p>blood vessels</p> Signup and view all the answers

Pathological conditions like tumour angiogenesis can significantly affect normal ______ processes in the body.

<p>vascular</p> Signup and view all the answers

In embryonic development, a vascular system is required to transfer ______ and nutrients effectively.

<p>gases</p> Signup and view all the answers

Vasculogenesis refers to the formation of blood vessels by ______ cells.

<p>endothelial</p> Signup and view all the answers

Atherosclerosis is a multifaceted process that starts with endothelial ______.

<p>dysfunction</p> Signup and view all the answers

Capillaries have a ______ cell layer that allows for efficient material exchange.

<p>single</p> Signup and view all the answers

Continuous capillaries are characterized by a complete endothelial lining with tight ______.

<p>junctions</p> Signup and view all the answers

Fenestrated capillaries are commonly found in the small ______ and kidneys.

<p>intestine</p> Signup and view all the answers

The primary function of ______ is to stabilize the capillary structure.

<p>pericytes</p> Signup and view all the answers

Platelet-derived growth factor (PDGF) acts as a ______ that induces movement in nearby cells.

<p>chemokine</p> Signup and view all the answers

Sinusoid capillaries allow blood cells to enter the blood supply through their large ______.

<p>openings</p> Signup and view all the answers

Pericytes are localized primarily at ______-endothelial junctions.

<p>endothelial</p> Signup and view all the answers

Angiopoietin-1 (Ang-1) binds to Tie-2 ______ on endothelial cells.

<p>receptors</p> Signup and view all the answers

Endothelial cells form a barrier between the blood and the ______ wall.

<p>vessel</p> Signup and view all the answers

The smooth muscle surrounding blood vessels can dilate due to the production of ______ gas by endothelial cells.

<p>NO</p> Signup and view all the answers

The primary role of endothelial cells includes fluid ______ in structures like the glomerulus of the kidney.

<p>filtration</p> Signup and view all the answers

Arteries have ______ walls and small lumens compared to veins.

<p>thick</p> Signup and view all the answers

Neutrophil recruitment in endothelial cells is facilitated by the expression of ______.

<p>P-selectin</p> Signup and view all the answers

The internal elastic layer is found in larger ______.

<p>arteries</p> Signup and view all the answers

Blood vessels transport ______ around the body, including hormones and nutrients.

<p>nutrients</p> Signup and view all the answers

Endothelial cells allow small metabolites to pass through by ______ and filtration.

<p>diffusion</p> Signup and view all the answers

The principal angiogenic ligand is ______.

<p>VEGFA</p> Signup and view all the answers

The key to lumen formation is ______ repulsion.

<p>electrostatic</p> Signup and view all the answers

Angiopoietin-2 (Ang2) interferes with Ang1-Tie2 ______.

<p>stability</p> Signup and view all the answers

Step 1 in angiogenesis is endothelial cell ______.

<p>activation</p> Signup and view all the answers

Nitric oxide causes ______ and increased permeability.

<p>vasodilation</p> Signup and view all the answers

Anastomosis is the formation of an interconnected ______ space.

<p>luminal</p> Signup and view all the answers

VEGF stimulates the production of ______ by cells.

<p>nitric oxide</p> Signup and view all the answers

The three receptors for VEGF are VEGFR1, VEGFR2, and ______.

<p>VEGFR3</p> Signup and view all the answers

Drugs like Bevacizumab block tumor cell-derived ______, impairing the development of new vessels.

<p>VEGF-A</p> Signup and view all the answers

Atherosclerosis can lead to thrombus formation and ______ events.

<p>cardiovascular</p> Signup and view all the answers

Oxidized LDL is formed when endothelial cells ______ LDL.

<p>engulf</p> Signup and view all the answers

The lack of oxygen and nutrients typically prevents the growth of tumors larger than ______ mm in diameter.

<p>1-2</p> Signup and view all the answers

Monoclonal antibodies are used to target VEGF receptors and ______ isoforms.

<p>VEGF</p> Signup and view all the answers

The effective inhibition of tumor angiogenesis might halt tumor progression but not completely ______ the tumor.

<p>eradicate</p> Signup and view all the answers

Low density lipoproteins (LDLs) can cause injury to ______ cells.

<p>endothelial</p> Signup and view all the answers

What is the primary function of vascular endothelial growth factor (VEGF) during hypoxia?

<p>Stimulates angiogenesis</p> Signup and view all the answers

Which process describes the splitting of an existing blood vessel into two?

<p>Intussusceptive angiogenesis</p> Signup and view all the answers

What happens to HIF1α when oxygen levels are sufficient?

<p>It becomes hydroxylated and degraded</p> Signup and view all the answers

What condition is characterized by a restriction in blood supply to tissues, leading to a lack of oxygen?

<p>Ischemia</p> Signup and view all the answers

What role does prolyl hydroxylase-2 (PHD2) play in oxygen sensing in cells?

<p>It enhances HIF1α degradation</p> Signup and view all the answers

What is the primary purpose of monoclonal antibodies like Bevacizumab in cancer treatment?

<p>To block tumor cell-derived VEGF-A, leading to tumor starvation</p> Signup and view all the answers

Which of the following aspects does not contribute to tumor growth beyond 1-2 mm in diameter?

<p>Cellular oxygen deficiency</p> Signup and view all the answers

What is a potential side effect associated with therapies targeting tumor angiogenesis?

<p>Increased risk of heart disease</p> Signup and view all the answers

Which component is not directly involved in the process of atherosclerosis development?

<p>Tumor-derived factors</p> Signup and view all the answers

When endothelial cells engulf LDL, what is the primary transformation that occurs?

<p>LDL undergoes oxidation to form oxidized LDL</p> Signup and view all the answers

What role does the angiogenic switch play in tumor physiology?

<p>Initiates the growth of new blood vessels</p> Signup and view all the answers

What is a key limitation of using angiogenesis inhibitors in cancer therapy?

<p>They do not completely eliminate the tumor</p> Signup and view all the answers

What is a likely result if the endothelial layer is severely affected by oxidized LDL?

<p>Increased risk of thrombus formation</p> Signup and view all the answers

What structural characteristic distinguishes continuous capillaries from fenestrated capillaries?

<p>Complete endothelial lining with tight junctions</p> Signup and view all the answers

What role do pericytes play in the vascular system?

<p>They stabilize capillary structures</p> Signup and view all the answers

In which structure are sinusoid capillaries primarily found?

<p>Bone marrow</p> Signup and view all the answers

What is the primary function of platelet-derived growth factor (PDGF)?

<p>Induce movement in nearby cells</p> Signup and view all the answers

What is the primary function of a smooth muscle layer in blood vessels?

<p>Regulate blood vessel diameter</p> Signup and view all the answers

What is the significance of angiopoietin-1 (Ang-1) in vascular biology?

<p>It binds to Tie-2 receptors on endothelial cells.</p> Signup and view all the answers

Which type of capillaries has no elastic layers and is primarily a site of nutrient absorption?

<p>Fenestrated</p> Signup and view all the answers

What role do mural cells (perivascular cells) play in the vascular system?

<p>Induce vascular quiescence</p> Signup and view all the answers

What is the primary function of endothelial cells in the circulatory system?

<p>Act as a semi-permeable barrier between plasma and tissues.</p> Signup and view all the answers

Which of the following properties are characteristic of arteries?

<p>Thick walls and small lumens.</p> Signup and view all the answers

How do endothelial cells contribute to fluid filtration?

<p>In locations like the glomerulus of the kidney.</p> Signup and view all the answers

Which gas do endothelial cells produce that influences blood vessel dilation?

<p>Nitric oxide</p> Signup and view all the answers

What condition results from a weakness in vein walls and valves?

<p>Varicose veins</p> Signup and view all the answers

What type of epithelial cells are endothelial cells classified as?

<p>Simple squamous epithelium</p> Signup and view all the answers

In terms of blood flow, which statement about arteries and veins is true?

<p>Arteries carry oxygen-rich blood away from the heart.</p> Signup and view all the answers

What role do endothelial cells play in hormone trafficking?

<p>They facilitate the transfer of hormones through pores or transcytosis.</p> Signup and view all the answers

What is the first step in angiogenesis?

<p>Endothelial cell activation</p> Signup and view all the answers

Which VEGF receptor is primarily associated with angiogenic signaling?

<p>VEGFR2</p> Signup and view all the answers

What role do proteases play in the angiogenic process?

<p>Degrade the extracellular matrix</p> Signup and view all the answers

Which of these molecules is involved in creating fenestrations in the endothelium?

<p>VEGFA</p> Signup and view all the answers

What is the function of electrostatic repulsion in the process of tubulogenesis?

<p>To help create vessel lumens</p> Signup and view all the answers

During angiogenesis, what causes pericytes to detach from endothelial cells?

<p>Loss of Ang1-Tie2 signaling</p> Signup and view all the answers

Which process involves the fusion of two endothelial cell sprouts?

<p>Vessel fusion</p> Signup and view all the answers

What is the result of increased permeability in the context of angiogenesis?

<p>Facilitated nutrient exchange</p> Signup and view all the answers

What role does oxidised LDL play in the process of endothelial injury?

<p>It contributes to endothelial cell injury.</p> Signup and view all the answers

What happens to monocytes after they invade the sub-endothelial space?

<p>They become macrophages and ingest lipids.</p> Signup and view all the answers

What is the likely consequence of a rupture in the protective fibrous cap of plaque?

<p>Exposition of thrombogenic material leading to thrombosis.</p> Signup and view all the answers

Which cells are primarily responsible for the ingestion of lipids and potentially leading to foam cell formation?

<p>Macrophages</p> Signup and view all the answers

What can be a direct effect of low-density lipoproteins (LDLs) blocking the blood vessel?

<p>Ischemia leading to potential cell infarction.</p> Signup and view all the answers

What indicates the transition of monocytes into macrophages upon entering the tunica interna?

<p>Their capability to ingest excess fat.</p> Signup and view all the answers

What is one effect of circulating monocytes invading the sub-endothelial space regarding inflammation?

<p>They initiate an inflammatory response.</p> Signup and view all the answers

Why can a myocardial infarction be fatal rapidly following blockage?

<p>Oxygen supply is crucial for cell survival, and delay can lead to death.</p> Signup and view all the answers

What unique function do endothelial cells serve in the circulatory system?

<p>They act as a semi-permeable barrier between plasma and tissue.</p> Signup and view all the answers

Which characteristic is NOT typical of arteries?

<p>Thin smooth muscle layer</p> Signup and view all the answers

What does the production of nitric oxide (NO) by endothelial cells primarily cause?

<p>Dilation of blood vessels</p> Signup and view all the answers

What is NOT a mechanism by which endothelial cells facilitate hormone trafficking?

<p>Active transport against gradients</p> Signup and view all the answers

Which structure is critically involved in the filtration process within the kidney?

<p>Capillary endothelial cells</p> Signup and view all the answers

Which of the following describes the composition of the outer layer of an artery?

<p>Connective tissue</p> Signup and view all the answers

What condition is often associated with a weakness of vein walls and valves?

<p>Varicose veins</p> Signup and view all the answers

What mechanism allows endothelial cells to stabilize the formation of new blood vessels?

<p>The direct attachment of pericytes to blood vessels</p> Signup and view all the answers

Endothelial cells contribute to neutrophil recruitment through the expression of which molecule?

<p>P-selectin</p> Signup and view all the answers

During the process of sprouting angiogenesis, what role do tip cells play?

<p>They respond to gradients of VEGF in hypoxic environments</p> Signup and view all the answers

What distinguishes intussusception from sprouting angiogenesis?

<p>Intussusception involves the splitting of existing vessels</p> Signup and view all the answers

Which process is directly initiated by the presence of VEGF?

<p>Activation of endothelial cells to undergo sprouting</p> Signup and view all the answers

Which factors must be present for endothelial cells to detach from the extracellular matrix?

<p>Digestion of the basement membrane and increased matrix ingress</p> Signup and view all the answers

Which cellular change occurs after monocytes invade the sub-endothelial space?

<p>They transform into macrophages.</p> Signup and view all the answers

What is the consequence of a rupture in the fibrous cap of plaque?

<p>It exposes thrombogenic material leading to thrombosis.</p> Signup and view all the answers

What happens to platelets in the presence of oxidised LDL?

<p>They encourage infiltration of smooth muscle cells.</p> Signup and view all the answers

Which condition can arise from the complete blockage of a blood vessel by plaque?

<p>Myocardial infarction or tissue death.</p> Signup and view all the answers

What primarily distinguishes angiogenesis from vasculogenesis?

<p>Angiogenesis is the process of forming new blood vessels from existing vessels.</p> Signup and view all the answers

Which statement accurately describes a role of endothelial cells in the circulatory system?

<p>Endothelial cells serve as a semi-permeable barrier between blood and surrounding tissues.</p> Signup and view all the answers

During the development of foam cells, what process do macrophages undergo?

<p>They ingest LDL particles and enlarge.</p> Signup and view all the answers

What results from the ingestion of lipids by smooth muscle cells in the intima?

<p>Development of atheromatous plaques.</p> Signup and view all the answers

In what way does hypoxia influence angiogenesis?

<p>Hypoxia promotes the secretion of factors like VEGF, which stimulate new blood vessel formation.</p> Signup and view all the answers

What is the primary function of the systemic circulation in the cardiovascular system?

<p>To transport oxygenated blood throughout the body.</p> Signup and view all the answers

What is a critical factor that determines the extent of injury during a myocardial infarction?

<p>The availability of oxygen to tissue.</p> Signup and view all the answers

What characterizes pathological conditions like tumor angiogenesis?

<p>Rapid growth of new blood vessels from dormant existing vasculature.</p> Signup and view all the answers

During embryonic development, what is the necessity for establishing a cardiovascular network?

<p>To ensure complex structures can obtain nutrients and oxygen efficiently.</p> Signup and view all the answers

What occurs during intussusceptive angiogenesis?

<p>An existing blood vessel splits into two through expansion.</p> Signup and view all the answers

Which process prevents tumors from growing larger than a specific size without the formation of new blood vessels?

<p>Oxygen diffusion limitation</p> Signup and view all the answers

Which of the following correctly describes the role of Angiopoietin-2 (Ang2) in vessel maturation?

<p>Mediates loss of endothelial integrity</p> Signup and view all the answers

Which of the following factors is primarily known as an angiogenic inhibitor?

<p>Endostatin</p> Signup and view all the answers

Which process is primarily responsible for tumor angiogenesis?

<p>Self-sufficiency in growth signals</p> Signup and view all the answers

What crucial role does VEGFA play in angiogenesis?

<p>Acts as a decoy receptor</p> Signup and view all the answers

Which of the following statements about placental growth factor (PIGF) is true?

<p>It belongs to the same family as VEGF.</p> Signup and view all the answers

Which of the following transformations is associated with sustained tumor growth through angiogenesis?

<p>Decreased apoptosis</p> Signup and view all the answers

The activation of which oncogenic process supports the transition from normal tissue to tumor development?

<p>Altered growth factor production</p> Signup and view all the answers

What is the primary effect of hypoxia on cells regarding angiogenesis?

<p>Stimulates the production of VEGF</p> Signup and view all the answers

What is the primary characteristic that differentiates fenestrated capillaries from continuous capillaries?

<p>Large openings allowing for higher permeability</p> Signup and view all the answers

What type of capillaries is primarily found in the kidneys, aiding in filtration processes?

<p>Sinusoid capillaries</p> Signup and view all the answers

Which function is directly associated with the PDGF (Platelet-derived growth factor)?

<p>Acting as a chemokine to induce cell movement</p> Signup and view all the answers

What structural feature of continuous capillaries aids their tight barrier function?

<p>Complete endothelial lining with tight junctions</p> Signup and view all the answers

Which component produced by pericytes is essential for stabilizing capillary structures?

<p>Angiopoietin-1 (Ang-1)</p> Signup and view all the answers

Which statement accurately describes the composition of mural cells?

<p>They are composed of pericytes and smooth muscle cells</p> Signup and view all the answers

What do the large openings in sinusoid capillaries allow for in the blood supply?

<p>Movement of larger blood cells and proteins</p> Signup and view all the answers

What is the process of sprouting angiogenesis?

<p>Activation of endothelial cells to form sprouts</p> Signup and view all the answers

Which factor primarily stimulates the production of VEGF?

<p>Hypoxia (lack of oxygen)</p> Signup and view all the answers

What occurs when oxygen levels are sufficient in relation to HIF1α?

<p>HIF1α is degraded by VHL</p> Signup and view all the answers

What is a characteristic of intussusceptive angiogenesis?

<p>Splitting of an existing blood vessel</p> Signup and view all the answers

Which role does prolyl hydroxylase-2 (PHD2) play in the process of angiogenesis?

<p>Senses oxygen levels in cells</p> Signup and view all the answers

What is one of the unique functions of endothelial cells?

<p>Fluid filtration in the kidney</p> Signup and view all the answers

What is a characteristic feature of arteries?

<p>Thick walls with small lumens</p> Signup and view all the answers

Which molecule do endothelial cells produce to help dilate blood vessels?

<p>Nitric oxide</p> Signup and view all the answers

What is the primary function of the endothelial cell layer?

<p>Facilitate exchange of materials</p> Signup and view all the answers

What condition describes the weakness of veins leading to their expansion?

<p>Varicose veins</p> Signup and view all the answers

Which structure acts as a transport network for hormones and the immune system?

<p>Circulatory system</p> Signup and view all the answers

What is the process by which endothelial cells aid in recruiting neutrophils?

<p>By expressing P-selectin</p> Signup and view all the answers

Which of the following best describes the endothelial cells?

<p>Simple, squamous epithelial cells</p> Signup and view all the answers

What is the principal angiogenic ligand in the process of angiogenesis?

<p>VEGFA</p> Signup and view all the answers

What causes the detachment of pericytes during the angiogenesis process?

<p>Loss of Ang1-Tie2 signaling</p> Signup and view all the answers

Which molecule is responsible for stimulating endothelial cell migration and increasing permeability?

<p>Nitric oxide</p> Signup and view all the answers

What is the first step in the process of angiogenesis?

<p>Endothelial cell activation</p> Signup and view all the answers

What role does CD34 play in lumen formation during angiogenesis?

<p>It helps to create electrostatic repulsion.</p> Signup and view all the answers

What is the process of anastomosis in angiogenesis?

<p>Merging of blood vessel sprouts</p> Signup and view all the answers

Which receptors are primarily associated with VEGF?

<p>VEGFR1 and VEGFR2</p> Signup and view all the answers

Which factor is critical for signaling and maintaining endothelial cell stability during angiogenesis?

<p>Angiopoietin-1</p> Signup and view all the answers

What is the 'angiogenic switch' associated with?

<p>Transition from prevascular to vascular phase</p> Signup and view all the answers

What effect does Bevacizumab have on tumor growth?

<p>It impairs the development of new blood vessels</p> Signup and view all the answers

What is a primary consequence of atherosclerosis?

<p>Thrombus formation and cardiovascular events</p> Signup and view all the answers

Which component do LDLs primarily transport in the body?

<p>Cholesterol</p> Signup and view all the answers

What does oxidized LDL contribute to within the vascular system?

<p>Injury to endothelial cells</p> Signup and view all the answers

Effective inhibition of tumor angiogenesis primarily prevents what?

<p>The development of new blood vessels</p> Signup and view all the answers

What is the role of monoclonal antibodies in tumor angiogenesis treatment?

<p>To specifically target and block VEGF and related pathways</p> Signup and view all the answers

What is the primary function of endothelial cells in blood vessels?

<p>To line the blood vessels</p> Signup and view all the answers

Which factor is primarily responsible for activating endothelial cells to sprout new blood vessels?

<p>VEGF (Vascular Endothelial Growth Factor)</p> Signup and view all the answers

What type of angiogenesis involves the formation of new vessels from pre-existing ones?

<p>Sprouting angiogenesis</p> Signup and view all the answers

Which cells are responsible for stabilizing capillaries?

<p>Pericytes</p> Signup and view all the answers

What happens to endothelial cells when they detach from pericytes during angiogenesis?

<p>They become tip cells and migrate</p> Signup and view all the answers

What role does Angiopoietin-2 (Ang2) play in vascular physiology?

<p>Antagonizes Ang1-Tie2 signaling and promotes loss of pericytes</p> Signup and view all the answers

Which factor primarily promotes angiogenesis under hypoxic conditions?

<p>VEGF</p> Signup and view all the answers

What is the consequence of sustained angiogenesis in tumors?

<p>Facilitation of limitless proliferation</p> Signup and view all the answers

Which of the following is considered an angiogenic inhibitor?

<p>Endostatin</p> Signup and view all the answers

Which characteristic is NOT part of the process of tumor angiogenesis?

<p>Sensitization to anti-growth signals</p> Signup and view all the answers

What is one of the angiogenic activators produced during pregnancy?

<p>Placental growth factor (PIGF)</p> Signup and view all the answers

Which transformation is part of the process by which tumors can invade surrounding tissues?

<p>Limitless cellular proliferation</p> Signup and view all the answers

What mechanism is involved in intussusceptive angiogenesis?

<p>Division of a pre-existing vessel into two</p> Signup and view all the answers

Study Notes

Endothelial Cells and Angiogenesis

  • Endothelial cells (ECs) are cells that line the inner surface of all blood vessels.
  • They are derived from angioblast precursor stem cells.
  • The major blood vessels are arteries, veins, and capillaries.
  • Perivascular cells, like pericytes, stabilize capillaries, while smooth muscle cells enhance the function of arteries and veins.
  • Angiogenesis is a complex process that involves two primary mechanisms: sprouting and intussusception. In the sprouting process, new blood vessels emerge as sprouts from existing vascular networks, typically driven by growth factors. Conversely, intussusception involves the division of established blood vessels, creating new lumens through the inward pinching of vessel walls.

Vascular Homeostasis

  • Activators:
    • Hypoxia: This condition arises when there is insufficient oxygen available to tissues, which can trigger adaptive responses in various cellular processes, including angiogenesis.
    • VEGF (Vascular Endothelial Growth Factor, especially VEGFA): VEGF is crucial for the formation of blood vessels, promoting the proliferation and survival of endothelial cells, and its expression is significantly upregulated under hypoxic conditions.
    • FGF-1 (Fibroblast Growth Factor-1): Recognized for its potent ability to stimulate endothelial cell proliferation, FGF-1 plays a significant role in promoting angiogenesis during tissue repair and regeneration.
    • Placental Growth Factor: This factor is predominantly expressed during pregnancy and is essential for the development of the placenta, as it facilitates the formation of the maternal-fetal blood supply and regulates angiogenesis.
    • Angiopoietin-2: This protein works in conjunction with VEGF to modulate blood vessel formation and stability, particularly during inflammation and tissue repair processes, where its expression may increase in response to various stimuli.
  • Inhibitors:
    • Soluble VEGF receptor-1, also known as sVEGFR-1, is a decoy receptor that can bind to vascular endothelial growth factor (VEGF), inhibiting its activity and thus preventing angiogenesis, which is crucial in tumor growth and metastasis.
    • Endostatin is a peptide derived from the cleavage of type XVIII collagen, and it possesses anti-angiogenic properties, effectively blocking endothelial cell proliferation and migration, which are essential steps in new blood vessel formation.
    • Angiostatin is a internally cleaved fragment of plasminogen that acts as a potent inhibitor of angiogenesis by interfering with endothelial cell metabolism and growth, thereby restricting the blood supply to tumors and limiting their growth potential.

Tumor Angiogenesis

  • Tumor angiogenesis is the tumor's ability to create new blood vessels.
  • This enables tumor expansion, local invasion, and dissemination.
  • Angiogenesis is one of six cellular transformations that lead to tumor malignancy.
  • Key factors in tumor angiogenesis include:
    • Self-sufficiency in growth signals (oncogene activation): This concept refers to the ability of cancer cells to generate their own signals that stimulate cell proliferation and survival. Usually, normal cells depend on external growth signals, but in oncogenically transformed cells, such as those with mutations in genes like Ras or Myc, growth signaling becomes autonomous, driving uncontrolled division.
    • Evasion of cell death signals (growth factor production): Cancer cells often evade apoptosis, the programmed cell death that typically serves as a safeguard against cancer. By upregulating the production of growth factors, these cells can create a microenvironment that favors their survival even in conditions that would normally trigger cell death.
    • Insensitivity to anti-growth signals (Rb mutations): The retinoblastoma protein (Rb) is a crucial regulator of the cell cycle. Mutations that inactivate Rb disrupt its ability to suppress progression through the cell cycle, allowing for continued proliferation in the absence of appropriate growth signals.
    • Limitless proliferation (telomerase function): Cancer cells often express the enzyme telomerase, which maintains the length of telomeres at the ends of chromosomes. This activity allows cells to bypass senescence and continue dividing perpetually, contributing to tumor growth.
    • Sustained angiogenesis (VEGF, FGF production): Tumors require a blood supply for nutrient and oxygen delivery. The sustained production of angiogenic factors such as Vascular Endothelial Growth Factor (VEGF) and Fibroblast Growth Factor (FGF) facilitates the formation of new blood vessels, enabling tumor expansion and metastasis.
    • Tissue invasion and metastasis (E-cadherin inactivation): Cancer cells can spread to other parts of the body through a process termed metastasis. Inactivation of E-cadherin, a protein that helps cells adhere to one another, promotes the detachment of tumor cells from the primary site, allowing them to invade surrounding tissues and metastasize to distant organs.

Blood Vessels: Properties and Types

  • Arteries: Thick walls, small lumens; larger arteries have an internal elastic layer; smooth muscle is the thickest layer; the outer layer is connective tissue, protecting and binding the artery.
  • Veins: Thinner walls, large lumens; no elastic layers, have valves; smooth muscle layer is thinner than the outer connective tissue layer.
  • Capillaries: Single cell-layer of endothelial cells, surrounded by a basement membrane.

Capillaries: Types

  • Continuous: Complete endothelial lining with tight junctions, allowing small metabolite diffusion and filtration.
  • Fenestrated: Common in the small intestine and kidneys; have pores (fenestrations) for more rapid absorption/filtration.
  • Sinusoid: Have large openings (sinuses) to allow larger molecules and blood cells to pass for functions such as hematopoiesis.

Endothelial Cell Function

  • Act as a semi-permeable barrier between plasma and tissue (fluid filtration, like in kidneys).
  • Blood vessel tone—produce nitric oxide (NO) to dilate smooth muscle.
  • Haemostasis—mechanism ending bleeding.
  • Recruit neutrophils (via P-selectin) and traffic hormones.

Endothelial Cell Types

  • Derived from angioblast stem cells.
  • Simple squamous epithelium lining blood and lymphatic vessels.
  • Simple epithelium allows small metabolites to pass by diffusion/filtration and secretes lubricating substances.

The Circulatory System

  • Pulmonary Circulation: Deoxygenated blood leaves the heart, travels to the lungs, gets oxygenated, and returns to the heart.
  • Systemic Circulation: Oxygenated blood leaves the heart, travels through arteries to the body, becomes deoxygenated, and returns to the heart through veins.

The Requirement for a Vascular System

  • In embryonic development, tissues are initially maintained by diffusion of gases, nutrients, and metabolites.
  • For complex structures, a way to transport gases and nutrients is needed.
  • The cardiovascular system is the first organ system to develop in an embryo.

Endothelial Cell Activation

  • Angiogenesis first step involves endothelial cell activation.
  • This process is crucial for tissue remodeling and repair, as proteases facilitate the degradation of the extracellular matrix, allowing for cell migration and new tissue formation. The breakdown of the matrix is essential not only for wound healing but also in various physiological and pathological processes, including cancer progression and inflammation.
  • Vascular endothelial growth factor (VEGF) is a key signaling protein involved in angiogenesis, the formation of new blood vessels. By promoting nitric oxide (NO) production, VEGF induces vasodilation, which leads to increased blood flow and enhanced permeability of blood vessels. This mechanism is vital for delivering nutrients and oxygen to tissues, particularly in response to injury or hypoxia.

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Test your knowledge on the human circulatory system with this quiz. You'll explore topics related to blood vessels, capillaries, and processes such as angiogenesis and vasculogenesis. Perfect for students studying biology or anatomy.

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