LEC 23: Heart I (Vessels, Blood, Microstructure)- Part I - 09.03.14

Question 1

What are the 5 types of arteries and veins

Answer 1

Artery <—–> Large Vein

Muscular Artery <—–> Medium (muscular) Vein

Small (muscular) Artery <—–> Small (muscular) Vein

Arteriole <—–> Venule

Capillary <—–> Postcapillary Venule

Question 2

Walls of arteries and veins are composed of (3) concentric layers (tunics)

Answer 2

1. tunica intima (inner layer)
2. tunica media (middle layer)
3. tunica adventitia (outer layer)

NB: 3 tunics show different variations in different types of arteries/veins

Question 3

Common iliac artery (H&E)

Answer 3

A. Tunica intima

B. Tunica media

C. Tunica adventitia

Question 4

Describe the parts of the wall in this common iliac artery (H&E)

Answer 4

A. Tunica intima

• endothelium and its basement membrane
• subendoendothelial connective tissue

B. Internal elastic lamina

C. Tunia media

• elastic fibers
• collagen fibers
• ground substance
• smooth muscle cells

Question 5

Describe the parts of the wall in this common iliac artery (H&E)

Answer 5

A. Tunica media

B. External elastic lamina

C. Tunica adventitia

• loose connective tissue with collagen, some elastic fibers, fibroblasts
• vasa vasorum (vessels of the vessel); Nerves

Question 6

vasa vasorum

Answer 6

Latin, “vessels of the vessels”

network of small blood vessels that supply the walls of large blood vessels

Question 7

Name this structure, found in the tunica media

Answer 7

postganglionic sympathetic nerve for vasoconstriction of the vessel wall, mediated by smooth muscles in the tunica media

Question 8

Name the structure stained black in this slide of an elastic artery (resorcin fuchsin stain)

Answer 8

• elastic fibers are stained black
• sheets of fenestrated elastic membranes (laminae) = stacks of chicken wire

NB: elastic fibers are blurry pink under H&E stain

Question 9

laminae

Answer 9

fenestrated elastic membranes found in elastic arteries

Question 10

Describe what is shown in this slide of an elastic artery (e.g. aorta)

Answer 10

• 40-70 sheets of fenestrated elastic membranes (laminae)
• external and internal elastic lamina are not conspicuous
• Vasa vasorum; nerves

Question 11

Describe what is shown in this slide of a large vein (e.g. vena cava)

Answer 11

Tunica intima = internal elastic lamina

Tunica media = circular smooth muscle

Tunica adventitia = longitudinal smooth muscle (runs along vessel)

Vasa vasorum; nerves

Question 12

elastic arteries

Answer 12

• aorta and major branches are elastic arteries
• elastic tissue in wall allows vessels to become distended when blood surges into them during systole
• during diastole, elastic recoil of distended arteries forces more blood along the arterial vessels, thus maintaining arterial pressure in the vessels while heart is filling
• elastic arteries are physiologically conducting vessels

Question 13

systole

Answer 13

contraction of heart muscles

Question 14

diastole

Answer 14

relaxation of the heart muscle

Question 15

large veins

Answer 15

• venae cavae are large veins
• pressure in venous system = low
• pressure continues to drop as veins converge towards the heart
• walls of veins = thin, easily distensible, compliant
• compliance of veins allows them to act as reservoir for blood collected from other areas of vascular system
• physiologically, veins are reservoir vessels or compliance vessels

Question 16

Describe this slide

Answer 16

• typically occur together (nerve/artery/vein)
• artery is much more circular
• vein is collapsible

Question 17

Describe this slide of a muscular artery (Resorcin fuchsin stain for elastic fibers)

Answer 17

A. Internal elastic fibers (IEL)

B. Tunica media

C. External elastic fibers (EEL)

D. Tunica adventitia

Question 18

Describe this slide of a medium (muscular) vein (Resorcin fuchsin stain)

Answer 18

A. Tunica media

B. Tunica adventitia

NB: Tunica adventitia is much larger

Question 19

muscular arteries

Answer 19

• brachial, femoral, coronary arteries
• relatively large proportion of muscle in muscular arteries (allows for rapid distribution of blood to tissues)
• low resistance to flow of blood (allows for rapid distribution)
• repeated branching, muscular arteries diminish in caliber to form small muscular arteries
• small muscular arteries feed into arterioles
• muscular arteries = distributing arteries

Question 20

medium veins (muscular veins)

Answer 20

• companion veins of muscular arteries
• valves are present in muscular veins
• physiologically, medium veins are collecting vessels

Question 21

Describe this slide

Answer 21

• small (muscular) artery
  
  • tunica media = 3-10 smooth muscle layers
  • internal elastic lamina (IEL) is visible
• small (muscular) vein
  
  • few smooth muscle layers in wall

Question 22

Describe this slide

Answer 22

• arterioles
  
  • tunica media = 1-3 layers of smooth muscle
• venules
  
  • few smooth muscle in wall, flattened, irregular shape

NB: largest artery is NOT an arteriole but a smooth muscular artery (too many layers of smooth muscle!)

Question 23

Arterioles

Answer 23

• arteriolar diameter can be varied with great precision by contraction of the smooth muscle in response to sympathetic neural and non-neural stimuli
• contraction increases resistance to blood flow and the pressure in the muscular and elastic arteries rises
• physiologically, arterioles control systemic blood pressure and are called resistance vessels

Question 24

Microcirculation

Answer 24

Artery—arteriole—capillary bed—venule—vein

Question 25

Describe this slide (hint: microvasculature)

Answer 25

A. capillary * can only accomodate 1 red blood cell; (wall = endothelial cell) B. Arteriole C. Postcapillary venule * no smooth muscle present in postcapillary venule

Question 26

postcapillary venules

Answer 26

* 10-25um in diameter (3x as large as capillary) * endothelium is more perable than capilalry * preferred location for emigration of white blood cells from the blood circulation, especially during inflammation * postcapillary venules are **inflammation vessels** * pericytes replace smooth muscle cells in postcapillary venules

Question 27

diapedisis

Answer 27

the passage of blood cells through the intact walls of the capillaries, typically accompanying inflammation

Question 28

Describe this slide

Answer 28

* capillaries (longitudinal and transverse sections) * E = endothelial cell nuclei * Pericytes = occasionally embrace the capillary endothelial cells, may have a contractile function

Question 29

pericytes Shown: EM of a capillary and pericyte

Answer 29

* replace smooth muscle cells in postcapillary venules * outside capillaries or postcapillary venules * contractile proteins (actin, myosin, tropomyosin) * contraction serves to regulate blood flow through capillaries * can differetiate into smooth muscle and endothelial cells in response to injury or stimulation by growth factors

Question 30

capillaries

Answer 30

* major site of **gas/fluid/nutrient/metabolic waste products** exchange between blood and tissue * physiologically, capillaries are **metabolic exchange vessels**

Question 31

classification of capillaries

Answer 31

1. continuous 2. fenestrated 3. discontinuous (sinusoids)

Question 32

examples of continuous capillaries

Answer 32

* muscles * brain * lungs * bone

Question 33

examples of fenestrated capillaries

Answer 33

* intestines * endocrine glands * kidneys

Question 34

examples of discontinuous (sinusoids) capillaries

Answer 34

* liver * bone marrow * spleen

Question 35

What is noteable about the endothelium lining the sinusoid (discontinuous) capillary

Answer 35

* endothelium lining the sinusoid has fenestrae and lacks a basement membrane * allows for bidirectional flow