L10 Blood And Lymphatic Vessels

Front 1

What is the function of the blood circulatory system?

Back 1

• Deliver O2 and nutrients to tissues

• Remove CO2 and other waste products fromtissues.

• Transport cells of the immune system

• Distribute chemical messengers (e.g. hormones)

• Temperature Regulation

Front 2

What is the function of The Lymphatic System?

Back 2

• Drain extracellular fluid (lymph) from the tissues,to the blood circulatory system

• Immunological screening via passage through thelymph nodes

Front 3

What does the blood circulatory system consist of?

Back 3

1. Heart

2. Arteries

3. Capillaries

4. Veins

Front 4

Which are the vessels?

Back 4

2. Arteries3. Capillaries4. Veins

Front 5

What is the common basic structure of the blood vessels?

Back 5

1. Tunica Intima

2. Tunica Media

3. Tunica Adventitia

Front 6

What makes up the wall of the typical blood vessel?

Back 6

Three separate concentric layers, ortunics, make up the wall of thetypical blood vessel

Front 7

What is the innermost layer of the blood vessel?

Back 7

The innermostlayer, the tunica intima, iscomposed of a single layer offlattened, squamous endothelial cells,which line the lumen of the vessel,and the underlying subendothelialconnective tissue.

Front 8

What is the intermediate layer of the bloood vessel?

Back 8

The intermediatelayer, the tunica media, is composedmostly of smooth muscle cellsoriented concentrically around thelumen.

Front 9

What is the outermost layer of the blood vessel?

Back 9

The outermost layer, thetunica adventitia, is composedmainly of fibroelastic connectivetissue whose fibers are arrangedlongitudinally

Front 10

What do the endothelial cells of the tunica intima line?

Back 10

A layer of endothelial cells lining the vessel’s inner surfaceincluding the basal lamina.

Front 11

What do larger vessels contain in their tunica intima?

Back 11

In larger vessels, a subendothelial layer of looseconnective tissue that may contain a few smooth musclecells which tend to be organised longitudinally

Front 12

Where does the internal elastic lamina of the tunica intima lie?

Back 12

An internal elastic lamina lies beneath the subendotheliallayer which is well developed in muscular arteries.

Front 13

What does the endothelium do?

Back 13

• Actively involved in mediating the exchange of small moleculesbetween the interstitial fluid and blood plasma and restrict thetransport of macromolecules.

• Assists the migration of lymphoid cells to and from tissues.

• Clotting regulation

• Vasodilation

Front 14

What is the endothelium?

Back 14

It is a specialised epithelium which secretes specific substances

Front 15

Prostacyclin is a factor secreted by the endothelium. What are it's activities?

Back 15

Vasodilatation, inhibits platelet aggregation

Front 16

What are the activities of Nitric oxide?

Back 16

Vasodilatation, inhibits platelet adhesion &aggregation

Front 17

What are the activities of the factor Tissue plasminogen activator?

Back 17

Regulates fibrinolysis

Front 18

What are the activities of Thrombomodulin?

Back 18

Anticoagulant activity

Front 19

What are the activities of Thromboplastin?

Back 19

Promotes blood coagulation

Front 20

What does Platelet activating factor do?

Back 20

Activation of platelets

Front 21

What does Von Willebrand factor do?

Back 21

Promotes platelet adhesion and activation ofblood coagulation

Front 22

What is the tunica media composed of?

Back 22

• Concentric layers of helically arranged smooth muscle cells

• Variable amounts of elastin and proteoglycans (dependingon the vessel size).

• In arteries the media is separated from the intima by aninternal elastic lamina and from the adventitia by an externallamina.

Front 23

What is the tunica adventitia composed of?

Back 23

• Longitudinally orientated (type 1) collagen and elasticfibres.

• The adventitia gradually becomes continuous with theenveloping connective tissue of the organ through which thevessel is running. The adventitia is often the most prominentcoat in veins.

Front 24

How is blood pressure related to vascular anatomy?

Back 24

Front 25

What are arteries specially adapted to be like?

Back 25

Specially adapted structure to withstand the high pressure towhich they are subjected.

Front 26

what are the large elastic arteries?

Back 26

Large Elastic Arteries: the Aorta and major branches

Front 27

Which type of artery as the thickest tunic intima?

Back 27

Of all the types of arteries, the elastic arteries have thethickest intima with connective tissue displaying alongitudinal orientation and an internal elastic laminapresent

Front 28

How are the tunica media of elastic arteries adapted?

Back 28

In elastic arteries contains layers of concentrically arrangedelastic fibres. There are smooth muscle fibres between theelastin, along with proteoglycans. The elastin provides theresilience to smooth out the pressure wave.

Front 29

What is the adventitia of elastic arteries adapted to be like?

Back 29

Underdeveloped and contains elastic and collagen fibres.

Front 30

What makes up the elastic arteries?

Back 30

The aorta and its largest branches (brachiocephalic,common carotid, subclavian, common iliac)

Front 31

What do these elastic arterial vessels do?

Back 31

Conduct the blood away from the heart and distribute itto the medium sized arteries.

Front 32

How do they stabilize the high pressure flow of blood from the heart?

Back 32

They receive blood from the heart at high pressure butthis is intermittent and therefore they must stabilize theflow by extending during systole and recoiling duringdiastole.

Front 33

What is the problem overcome by the vasa vasorum?

Back 33

Internal layers of larger vessels are too thick to besustained by simple diffusion of nutrients from the blood.They therefore require blood vessels to run within theirvessel walls (vasa vasorum).

Front 34

How us the intima of elastic arteries different to those of elastic arteries?

Back 34

Intima: Thinner than elasticarteries .

Front 35

What is the structure of the tunica media of muscular arteries?

Back 35

Up to 40 layers ofsmooth muscle andsome elastin andproteoglycans arepresent. It isusually between1cm and 0.5cm indiameter

Front 36

What is the adventitia of the muscular arteries made up of?

Back 36

Collagen and elasticfibres present aswell as fibroblastsand fat cells.

Front 37

Describe the 3 layers of the arterioles

Back 37

IntimaThin: May not have aninternal elastic lamina.

Media: 1-5 layers of smoothmuscle cellsAdventitia: Very thin

Front 38

What are the functions of the arterioles?

Back 38

• Final branches of the arterialsystem

• Important regulators of blooddistribution to the capillaries.

Front 39

What does the small lumen of the arterioles allow?

Back 39

The small lumen allows thevessel to be closed to generateresistance to blood flow which isthe major determinant of bloodpressure.

Front 40

What are the capillaries and what are they adapted for?

Back 40

• Smallest vessels of the circulatory system.

• Specialised for diffusion of substances across their wall

Front 41

What do they lack structurally compared to the other vessels?

Back 41

Structurally, they lack the intimal, medial and adventitiallayers present in the rest of the circulatory system.

Front 42

What are the features of the capillaries?

Back 42

Thinnest walls of all the blood vessels, a low blood flow anda large surface area.

Front 43

What happens at the capillaries?

Back 43

They are the major site of gaseous exchange, permitting thetransfer of oxygen from blood to tissues and carbon dioxidefrom tissues to blood. Fluids containing large molecules passacross the capillary wall in both directions.

Front 44

What are the capillary pericytes?

Back 44

Pericytes are capillary support cells that are found wrappedaround the vessel in close contact with the basal lamina of thevessel.

Front 45

What are the capillaries composed of?

Back 45

Capillaries are composed of a single layer of endothelial cellsof mesenchymal origin rolled up in the form of a tube rangingin diameter from 7-9um and varying in length from 0.25 -1mm.

Front 46

What are the 4 types of capillaries?

Back 46

1. Continuous

2. Fenestrated with diaphragm

3. Fenestrated without diaphragm

4. Discontinuous

Front 47

What are the continuous capillaries?

Back 47

• Found in the brain, muscle, thymus, bone and lung.

• Transport substances through the cytoplasm by diffusionand and pinocytosis.

• Endothelial cells are held together by tight junctions and thebasal lamina is continuous.

Front 48

What are the fenestrated capillaries?

Back 48

• Endothelial cell has manyfenestrations with or withoutdiaphragms and a continuous basallamina.

• Present in tissues involved in fluidtransport (intestinal villi, choroidplexus and the glomerularcapillaries).

Front 49

What are the discontinuous capillaries?

Back 49

• Gaps are larger thanfenestrated capillaries andthe basal lamina isdiscontinuous.

• Found in tissues wherethere is a need for a closeassociation of blood and theparenchyma (e.g. liver andspleen).

Front 50

Where does the blood go after the capillaries?

Back 50

Blood from capillaries enters a system of venules (10-25µm)which initially are very similar to capillaries but have morepericytes.

Front 51

What do these post-capillary venules drain into?

Back 51

Post capillary venules drain into larger venules (20-50 µm)in which the pericyte layer becomes continuous andsurrounding collagen fibres appear

Front 52

What happens as the collecting vessels of the venous system become larger?

Back 52

As the collecting vessels becomes larger the pericytes arereplaced by smooth muscle and and an adventitia becomesidentifiable. These muscular venules (50-100 µm) drain intoveins.

Front 53

How do the veins vary?

Back 53

Veins vary in size from less than 1mm to 40mm in diameter.The lumen of veins is large but the walls are thin and usuallylook collapsed in histological sections. As with arteries theirstructure depends on size.

Front 54

What do smal veins look like?

Back 54

Small Veins (up to 1mm)There is a more clearly defined muscularcoat than muscular venules.

Front 55

What do medium veins look like?

Back 55

Medium Veins (1 to 10mm)There is evidence of a discontinuousinternal elastic membrane. The adventitiais well developed.

Front 56

What do large veins look like?

Back 56

Large Veins: The intima is well developed with collagenand elastic fibres. As is the adventitia.

Front 57

What are the valves of veins?

Back 57

Valves are projections into the lumen of the tunica intima. They are covered by endothelial cells and have a core of elastic fibres

Front 58

What is the venous blood flow driven by and what is the function of the valves?

Back 58

Venous blood flow is driven by a combination ofcontraction of the smooth muscle wall of the vesseland contraction of surrounding skeletal muscle.Valves are necessary to prevent backflow of blood.

Front 59

What causes varicose veins?

Back 59

Defective veinousvalves leads to thedevelopment ofvaricose veins whereblood pools within thevessel.

Front 60

How is the tunica media of veins characterised?

Back 60

The muscular tunica media of veins is thinner than that of arteries. Smooth muscle fibres have an irregular orientation, approximately circular

Front 61

How is the tunica adventitia of veins characterised?

Back 61

Loose connective tissue with few nerve fibres. In large vessels, vasa vasorum penetrate the tunica media

Front 62

What are the main differences between veins and arteries?

Back 62

• Veins have a highly distensible wall resulting inan irregularly shaped lumen histologically

• Walls are thinner in veins than in arteries

• Valves present in Veins

Front 63

Where do lymphatic capillaries orginate?

Back 63

• Lymphatic capillaries originate in tissue as thin blind-endedvessels consisting of a single layer of endothelium withoutfenestrations, junctional complexes or a basal lamina

Front 64

What do the lymphatics do?

Back 64

Lymphatics act as a drainage system removing surplus fluidfrom the tissue spaces

Front 65

Why are valves present in lymphatics?

Back 65

Like veins, valves are present to maintain flow in onedirection

Front 66

What allows antigen processing of the fluid in the lymphatic system?

Back 66

On its way to larger vessels the fluid passes through lymphnodes to allow antigen processing by the immune system

Front 67

What do the larger lymphatic vessels contain to pump the lymph into the main channels?

Back 67

The larger vessels have muscular walls and pump the lymphinto the main channels -the thoracic duct or the lymphaticduct from where it enters the blood vascular system

Front 68

What is Lacteal?

Back 68

Lacteal- lymphatics in the small intestine which aid in theabsorption of certain fats

Front 69

What is Chyle?

Back 69

Chyle- a milky fluid consisting of lymph and emulsified fats

Front 70

What surrounds the blood capillaries?

Back 70

Basal lamina

Front 71

What happens to the fluid and proteins in the interstitial space?

Back 71

Most of the fluid and proteins are reabsorbed back into the venous end of the capillary. About 1/10 of this fluid enters the lymphatic capillaries, in particular large proteins

Front 72

What do the anchoring filaments in the lymphatic vessels do?

Back 72

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

Front 73

What do the lymphatic capillaries look like histologically?

Back 73

Lymphatic capillaries have an irregular outline, a space endothelial cell lining lacking tight junctions, and no red blood cells in the lumen.