Blood vessels and Lymphatics Flashcards

1
Q

What is the histology of blood vessels ?

A
3 layers: 
Tunica intima (endothelium + CT)
Tunica media (muscle + CT)
Tunia adventita (thick CT)
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2
Q

What is the histology of the Tunica intima ?

A
  • Specialised simple squamous = endolthelium
  • Deep to endothelium, BM which binds it to CT
  • Possible internal elastic membrane at boundary with tunica media in larger arteries
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3
Q

What are the secretions of the endothelium ?

A

Endothelins, constrict smooth muscle within walls of vessels to increase BP

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4
Q

What is the histology of the Tunica Media ?

A
  • Concentric layers of helically arranged smooth muscle cells with elastic fibres
  • Possible external elastic membrane at boundary with tunica adventitia in larger arteries.
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5
Q

Which is the thickest layer in arteries ? Why ?

A
Tunica media (much thicker in arteries than in veins). Because they need to push blood against P gradient. 
(May be tunica adventitia in some arteries.)
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6
Q

How do vasoconstriction and vasodilation take place ?

A

Vasoconstriction: contraction of circular muscle, reducing diameter of the lumen, decreasing blood flow and increase blood P

Vasodilation: relaxation of circular muscle etc.

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7
Q

What is the histology of the Tunica Adventitia ?

A

-Longitudinally oriented CT made of type 1 collagen fibres

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8
Q

What is the thickest layer in veins ?

A

Usually tunica adventitia

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9
Q

What is the normal path for blood flow ?

A

Large Elastic arteries - Medium Muscular arteries - Arterioles - Capillaries - Venules - Medium Veins - Large Veins - Heart

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10
Q

Why are elastic arteries elastic ? What is the role of elastic arteries ? How do they behave during systole and diastole ?

A

Because of elastic fibres in the tunica media.
Conducting.
They expand during systole
They recoil during diastole to help drive blood onwards

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11
Q

Why are muscular arteries muscular ?

What is their role ?

A

Due to thick layer of circular smooth muscle in tunica media.
They:
1. control distribution of blood to regions and organs
2. regulate blood flow by constriction and relaxation of walls

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12
Q

What happens to muscular arteries when there is an occlusion of an artery ? If there is a haemorrhage ?

A
They can accommodate a change in diameter: 
The diameter of collateral muscular arteries increases to carry blood to ischaemic area. 
They contract (diameter decreases) to prevent blood loss.
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13
Q

What are the main arteries of the upper part of the body ?

A

Arotic arch, left subclavian, brachiocephalic artery, right subclavian, right vertebral, left vertebral, right common carotid, left common carotid, right internal carotid, left internal carotid.

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14
Q

What are the main arteries of the upper limbs?

A

Subclavian, Axillary, Brachial, Ulnar, Radial

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15
Q

What is the first branch of the aorta ?

A

Coronary Arteries

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16
Q

What is arterial anaestemosis ?

Where in the body is it useful ?

A

Communication between blood vessels

Around joints and in the hand and fingers (ensures supply of blood in any position of the upper limb, even if flexing)

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17
Q

What are the anaestemoses of the hand called ?

A

Deep and superficial palmar arch (between radial and ulnar arteries)

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18
Q

What are the large arteries of the trunk ?

A

Aorta divided into ascending, descending aorta, and aortic arch.

  • Descending aorta yields thoracic and abdominal aorta
  • Abdominal aorta then divides into R and L common iliac arteries (deliver blood to lower limbs)
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19
Q

What are the lower limb arteries ?

A

Common iliac arteries divides into internal and external.
-Once the external iliac artery passes ligament in the thigh, becomes femoral artery (accompanied by femoral vein medially and femoral nerve laterally)

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20
Q

Why is the femoral artery clinically relevant ?

A

Because you might get arterial blood from it (although difficult because may injure femoral nerve)

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21
Q

What are arterioles ? Metarterioles ?

A

Arteries with less than 0.5 mm in diameter.

Arteries with same diameter as capillary but one layer of smooth muscle cells in walls to still distribute blood.

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22
Q

What is the histology of capillaries ?

A

Endothelial cells supporting on BM
NO smooth muscle cells
Pericytes enclosed in BM splits (contain myosin, actin and tropomyosin)

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23
Q

What is the function of capillaries ?

A
  • Allow exchange of O2, CO2, nutrients and hormones between cells or interstitial fluid and blood.
  • Some contractile function thanks to the pericytes
24
Q

Which processes take place to allow exchange in capillaries ?

A

Active Transport and Passive Transport (osmosis, diffusion, filtration, facilitated diffusion)

25
Q

What structure regulates blood flow through capillaries ?

A

Pre-capillary sphincter (contracts to block flow)

26
Q

Give an example of situation where pre-capillary sphincters would need to close.

A

High demand for blood in heart and brain so sphincters in limbs basically close (e.g. in ice cold water)

27
Q

What is the difference between fenestrated and continuous capillaries ? Where in the body would you find each type ?

A

Fenestrated capillaries have small pores.
Mainly continuous ones in our body.
In intestine, endocrine glands, kidneys, choroid plexus, fenestrated capillaries allows bigger molecules to enter or exit.

28
Q

What is the percentage of blood in the venous system at any one time ?

A

70%

29
Q

Histologically, what is the main difference between arteries and veins ?

A

Tunica media is much thinner with only a few smooth muscle cells.

30
Q

What is Diapedesis ?

A

Leukocytes passing through walls of venules and escaping into surrounding connective tissue.

31
Q

What is the function of valve leaflets ?

A

Preventing backflow by closing when BP proximal > BP distal

32
Q

What is a specificity of large arteries versus medium and smaller arteries ?
How does this specificity aid venous return ?

A

They have their own veins alongside them whilst medium and smaller arteries have venae comitantes around them (usually 2).
Pulsation of arteries aids venous return to the heart against gravity.

33
Q

What is atheroma ? What are associated risks ?

A

Plaques forming within arteries due to fatty deposit and scar tissue. May lead to the formation of thrombus (blood clot) and vascular occlusion.

34
Q

What are the lower limb veins ?

A

Deep veins- accompany limb arteries situated deeply. Tey are the venae comitantes (have same name as arteries).

Superficial veins- lie immediately under the skin (unique name). Great saphenous vein and small (shorter) saphenous vein

Perforating veins- connect deep and superficial veins. Have valves allowing flow from superficial to deep ONLY.

35
Q

What causes varicose veins ?

A

Incompetency of veins

36
Q

What factors aid venous return against gravity?

A

Valves, contraction of the muscle, arterial pulsation, negative intra-thoracic P (when we breath in)

37
Q

What are the upper limb veins ?

A

Deep veins

Superficial veins-
Cephalic veins
Basilic vein
Median cubital vein: connects cephalic and basilic vein

Perforating veins (but not as important as lower limbs since Pressure gradient is less)

38
Q

Why are superficial veins clinically relevant ?

A

They are frequently used for phlebotomy. Care must however be taken to avoid brachial artery and median nerve.

39
Q

List the large veins and the structures which drain into them.

A
  1. IVC- venous blood of lower limbs, pelvic organs, kidneys, abdominal wall drain into it.
  2. SVC- venous blood of head, neck and upper limbs drain into it.
  3. Azygos veins- venous blood of thoracic wall drain into it. Then drains into SVC
  4. Hepatic Portal veins- venous blood from components of GI tract, spleen and pancreas forms HPV, passes through liver. Then joins IVC.
40
Q

Which parts of the vessels themselves are supplied with blood ? How so ?

A

The walls of the vessels (especially the tunica media).

  • Larger vessels have their own vessels, vaso vasorum
  • Smaller vessels branch profusely in adventitia and outer part of media
41
Q

What are the components of the lymphatic system ?

A

Lymph vessels, lymph nodes, tonsils, thymus, spleen and intestinal wall

42
Q

What is the function of the lymphatic system ? How does it perform this ?

A

Helping veins remove the interstitial fluid (lymph) to prevent build up of it.

Lymph absorbed by lymph capillaries (thin walled endothelial tubes) —> Capillaries join and become lymph vessels —> Lymph in those vessels filtered by lymph nodes —> on L, thoracic duct drains lymph into vessels. On R, right lymphatic duct drain into vessel (disproportionate areas of drainage). On both sides, they empty at junction between internal jugular and sub-clavian veins.

43
Q

Where is the interstitial fluid located ?

A

Between the cells/organs and capillary bed

44
Q

Are veins and arteries related to different kinds of lymph nodes ?

A

Superficial lymph nodes related to veins

Deep lymph nodes related to arteries

45
Q

What structures does lymphatic drainage (and return to the veins) depend on ?

A

Adjacent muscle activity (since no pump) and valves to prevent backflow.

46
Q

List the superficial, palpable lymph node collection.

A

Inguinal, Auxillary, Cervical.

47
Q

What are the types of inguinal lymph nodes? Where are they located ? What do they drain ?

A
  1. Superficial Inguinal- In superficial fascia. Inferior to inguinal ligament in groin and alongside great saphenoid vein in groin. Drains into deep inguinal nodes
  2. Deep Inguinal- Alongside femoral vein.

Drain the lower limb and buttock, external genitalia, lower back, ab wall below umbilicus.

48
Q

Where is the Axillary lymph node collection located ? What does it drain ?

A

Lie scattered in fatty tissue packing the axilla. Related to the axillary vein and artery. Lateral to, deep to or medial to pectoralis minor.

Drain the upper limb, anterior and posterior thoracic walls, ab wall above umbilicus, breast.

49
Q

What are the types of cervical lymph nodes? Where are they located ? What do they drain ?

A
  1. Superficial cervical lymph nodes- under jaw; over parotid; behind ear; occipital
  2. Deep cervical lymph nodes- alongside internal jugular vein (jugulo-digastric; jugulo-omohyoid)

Drain the head and neck structures.

50
Q

Give an example of nodes from different node collections which communicate.

A

Yes. Inferior deep cervical nodes communicate with axillary and thoracic nodes (breast, lung).

51
Q

What is the largest lymph vessel in the body ? Where does it open ?

A

Thoracic duct. Opens at the junctions of left subclavian and internal jugular veins.

52
Q

What is forcing the water out of capillaries ? What is forcing it back in ?

A

Hydrostatic P at arterial end

Osmotic P at venous end

53
Q

What is lymphedema ?

A

Localised fluid retention

54
Q

What is the path for lymph return to the veinous circulation ?

A

Lymph —> Large veins in the neck —> on L, thoracic duct drains into vessels. On R, right lymphatic duct drain into vessels. On both sides, they empty at junction between internal jugular and sub-clavian veins.

55
Q

What are features of the lymph nodes allowing them to act as filterers ?

A

Contain T and beta lymphocytes which can recognize foreign antigens and starts immune response.

56
Q

How may lymph nodes be involved in the spread of cancer ?

A

Malignant cells become detached from primary tumour and be carried along lymph vessels until reach lymph node where may give rise to secondary tumour (metastasis)

57
Q

What structure gives rise to the thoracic duct ?

A

The cisterna chyli