B4.020 Cell Biology and Histology of the Vascular System

Question 1

what type of epithelial cells make up the vascular epithelium?

Answer 1

simple squamous cell apithelim

Question 2

major vessels of the cardiovascular system

Answer 2

large (elastic artery)
medium (muscular artery)
small artery (arteriole)
capillary
venule
medium and large veins

Question 3

discuss variations in BP between arterial and venous systems

Answer 3

heart bumps blood in a pulsatile fashion
higher pressure during systole, lower during diastole
arterial pressure pushes blood into capillaries and venous return system and then BP falls dramatically

Question 4

layers of artery walls

Answer 4

1. tunica intima (innermost)
2. tunica media (middle)
3. tunic externa/adventitia (outermost)

Question 5

what is internal elastic lamina made up of

Answer 5

discontinuous elastic fibers

Question 6

what is vasa vasorum

Answer 6

small blood vessels to nourish the outer layers of a thick blood vessel ( only present in the largest vessels)

Question 7

tunica intima

Answer 7

lining of endothelial cells, subendothelial basement membrane and loose connective tissue, dense layer of elastic fibers (internal elastic fibers)

Question 8

tunica media

Answer 8

concentric layers of smooth muscle, collagen fibers, discontinuous plates of elastic sheaths (external elastic lamina)

Question 9

tunica externa (adventitia)

Answer 9

connective tissue

Question 10

relate the structure and function of the large elastic arteries

Answer 10

have many elastic lamellae in the media
receive blood from heart under high pressure
walls distend during systole and recoil during diastole thereby sustaining a continuous blood flow despite intermittent pumping of the heart

Question 11

what are distributing arteries?

Answer 11

medium sized muscular arteries

allow selective distribution of blood to different organs in response to functional needs

Question 12

how do medium sized arteries differ from larger arteries?

Answer 12

medium sized have prominent internal elastic lamina
fewer elastic sheaths in intima, but more prevalent smooth muscle
external elastic lamina commonly seen

Question 13

what are resistance vessels?

Answer 13

arterioles
regulate the distribution of blood to different capillary beds by vasoconstriction and vasodilation
major determinants of systemic BP

Question 14

discuss the smooth muscle components of arterioles

Answer 14

2-4 concentric layers in tunica media

Question 15

discuss the structure of capillaries

Answer 15

consist only of endothelial cells and their basement membranes
small membranes (5-10 um)
permit the passage of one RBC at a time

Question 16

what are the 3 types of capillaries

Answer 16

continuous
fenestrated
discontinuous

Question 17

continuous capillary

Answer 17

contain pericytes (modified smooth muscle cells) between endothelium and basement membrane

Question 18

fenestrated capillary

Answer 18

pores or fenestrae in endothelium

Question 19

discontinuous capillary

Answer 19

overt gaps between endothelial cells

discontinuous basal lamina

Question 20

where are continuous capillaries found

Answer 20

places where exchange between circulation and tissue is tightly regulated
skeletal muscle, brain, thymus, lungs

Question 21

where are fenestrated capillaries found

Answer 21

sites of fluid transport: intestine, kidney

Question 22

where are discontinuous capillaries found

Answer 22

liver, spleen, bone marrow

where blood cells can pass readily through

Question 23

what makes up plasma

Answer 23

90% water
10% dissolved solutes
small amt blood gases (CO2 and O2)

Question 24

what makes up dissolved solutes?

Answer 24

9. 1% organic substances

0. 9% inorganic substances (various electrolytes)

Question 25

what makes up organic substances?

Answer 25

7.1% plasma proteins (albumin, globulin, fibrinogen) | 2% other (lipids, enzymes, hormones, nutrients, waste)

Question 26

what is the function of albumin

Answer 26

most abundant plasma protein | maintains oncotic pressure

Question 27

how are large proteins that are too big for diffusion able to exit the bloodstream?

Answer 27

plasmalemmal vesicles in continuous capillaries | neutrally charged allowing for transcytosis of anionic proteins

Question 28

what is caveolin

Answer 28

a coating on transport vesicles cytoplasmic surface (caveolae)

Question 29

what are pericytes?

Answer 29

contractile cells surrounding some capillaries and post capillary venules thought to regulate blood flow in capillaries, pericytes also allow endothelial cells to multiply and form branches (angiogenesis)

Question 30

how can pericytes lead to fibrosis?

Answer 30

in areas of chronic cell injury, they dedifferentiate into myofibroblast-like cells which overproduce ECM and lead to fibrosis

Question 31

what do fenestrae diaphragms do?

Answer 31

open and close like an optical lens to regulate permeability | without them, fenestrae are always open

Question 32

where is the preferred site of leukocyte egress from blood

Answer 32

veins

Question 33

how do leukocytes move across the vessel walls?

Answer 33

disruption of endothelial junctional complexes migration between cells through subendothelial basement membrane (diapedesis or extravasation)

Question 34

how do arteries and veins structure differ?

Answer 34

both have 3 tunics distinction between media and adventitia often unclear and a distinct internal lamina is usually absent in veins media is thinner than that found in arteries of same diameter veins have valves to prevent reflux

Question 35

what are some critical functions of the endothelium

Answer 35

set vascular tone vessel growth blood clotting inflammation

Question 36

what is prostacyclin

Answer 36

produced by endothelial cells to prevent adhesion of platelets and intravascular clot formation

Question 37

how do endothelial cells trigger coagulation?

Answer 37

release TF to stimulate the clotting cascade

Question 38

what is the result of oxidative stress on endothelium?

Answer 38

endothelial dysfunction and reduced NO bioavailability - leukocytes adhesion and inflammation - lipid deposition - vascular SM cell proliferation - vasoconstriction - platelet aggregation and thrombosis

Question 39

ultimate outcome of oxidative stress on vessels

Answer 39

progression of atherosclerosis and cardiovascular disease

Question 40

the formation of an atheroma

Answer 40

1. a damage of the endothelium of an artery is followed by extracellular space infiltration of LDL in the tunica intima 2. lipids are taken up by macrophages in the intima and fibroblasts of the subendothelial space proliferate 3. macrophages release lipids and macrophage derived cytokines stimulate the production of collagen by proliferating SM cells 4. ulceration of atheroma provides a surface for thrombosis

Question 41

what is the function of lymphatics

Answer 41

muscle contractions open up spaces between lymphatic endothelial cells to permit entrance of leukocytes, albumin, other proteins, and tissue fluid

Question 42

what are lymph nodes

Answer 42

distributed along lymphatic vessels to filter the lymph | sites of formation of immune responses

Question 43

Anchoring filaments

Answer 43

attach endothelial cells of lymphatic capillaries to the surrounding connective tissue to prevent lumen from collapsing

Question 44

where does interstitial fluid end up?

Answer 44

most reabsorbed into venous end of the capillary | 1/10th enters the lymphatic capillaries (particularly large proteins)

Question 45

vasculogenesis vs. angiogenesis

Answer 45

vasculogenesis- creating a new vascular network angiogenesis- sprouting from an existing network both require VEGF, ang1, and ang2 to induce vessel formation

Question 46

how does hypoxia mediate vessel growth?

Answer 46

hypoxia causes upregulation of HIF-1 by binding to promoter elements of genes

Question 47

what does HIF-1 do?

Answer 47

``` upregulate 90 target genes: EPO VEGF IGF2- inhibition of apoptosis GLUT- metabolic adaptation -first 2 increase oxygen delivery and second 2 help with oxygen deprivation survival ```