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ANAT 261 > Blood vessels > Flashcards

Blood vessels Flashcards

1
Q

What are the 2 main parts of the circulatory system?

A

Heart → function = pumping the blood
Vasuclar system → afferent (arteries) and efferent (veins) blood vessels

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2
Q

What are lymphatic vessels?
How do they start?
What are some of their important features?

A

Lymphatics are an anastomotic network of vessels that start as blind capillaries which converge into larger lymphatic vessels and drain into large veins

Features:
- Removed and recycle tissue fluid (lymph)
- Begin as open-ended lymph “capillaries”
- Very thin endothelium, with no occluding junctions
- No basement membrane, or partial
- Small/large lymphatic vessels can have valves (folds of endothelium)
- Large lymphatics have smooth muscle cells in their walls

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3
Q

What is the lymph composed of?

A

Lymph is formed by plasma enriched with immunoglobulins and lymphocytes produced by the lymphatic organs

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4
Q

What are, in order, the different types of arteries and veins

A

Heart
Large veins // Large (elastic) arteries
Medium/small size veins (muscular veins) // Muscular arteries
Venules // Arterioles
Post capillary venules // metarterioles
Capillary network

*each level runs in parallel → can be seen in same plan of section side by side

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5
Q

What are the different parts of the muscular arteries and its characteristics?

A

Intimar:
- Endothelium (gap and tight junctions)
- Sub-endothelial layer (thin)
- IELM (internal Elastic Limiting Membrane)

Media:
- 4 - 10 layer of smoothe muscle cells + collagen type III (reticular fibers) + proteoglycans

Adventitia:
- Dense irregular CT sometimes with vasa vasorum

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6
Q

What are the different parts of the medium/small size veins and their characteristics?

A

Intima:
- Endothelium (gap and tight junctions)
- Sub-endothelial layer
- NO IELM

Media:
- Incomplete layer ~2 of smooth muscle cells (CT in between the cells)

Adventitia:
Dense irregular CT with oy without vasa vasorum

*collapsed shape

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7
Q

What stain does the ILEM have affinity with?

A

Acidophilic → interacts with eosin → bright pink

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8
Q

What are the different parts of the large elastic arteries and their characteristics?

A

Intima:
- Well developed
- Endothelium → endocytic vesicles, gap and tight junctions
- Sub-endotheliual layer → thin
- IELM → fenestrated, is the 1st layer of elastic membrane before the media

Media:
- Alternance of smooth muscle cell layers and elastic membrane layers
- Rich in collagent type III and chondroitin SO4 proteoglycans

Adventitia:
- Dense irregular connective tissue rich in elastic fibers and collagen type I
- Contains vasa vasorum

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9
Q

What are the different parts of the large veins and their characteristics?

A

Intima:
- Endothelium
- CT and diffuse small muscle cells

Media:
- 5 layer or less of smooth muscle cells (no elastic membrane in alternance)
- CT and collagen within the layers

Adventitia:
- Often thickest layer
- Dense irregular CT + vasa vasorum

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10
Q

What are the different parts of arterioles and their characteristics?

A

Intima:
- Endothelium (gap + tight junctions)
- Subendothelial (thin-absent)
- no IELM, small elastic fibers

Media:
- 1 - 2 layers of smooth muscle cells

Adventitia:
- Thin without vasa vasorum
- Composed of connective tissue fibers/fibrils + fibrocytes

*Diamter = 0.5mm or less
*regular round shape

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11
Q

What are the different parts of venules and their characteristics?

A

Intima:
- Endothelium (with gap and tight junctions)
- No IELM, no Sub-endothelium

Incomplete media
- Pericytes may be present

Thin Aventitia

*Collapsed appearance, irregular shape
0.2mm to 20 um

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12
Q

What are metarterioles and postcapillary venules?

A

A capillary network is found between metarterioles (branch point of capillaries) and postcapillary venules (merge point of capillaries)

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13
Q

Why do some venules appear white and some red? Some collapsed and some not?

A

It depends on the method of preparation of the tissue slice
Red → Fixation by immersion bc RBCs are still there (more round?)
White → Fixation by perfusion which removed the blood (more collapsed?)

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14
Q

What is the precappillary sphincter?

A

It is the site at which the arteriole banches into capillaries → smooth muscle cells form pre-capillar ysphincter to regulate blood flow in the capillary network
*where the metarterial is located

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15
Q

What are AV anastomosis?

A

Where are direct connections between arterioles and venules (pre → post capillaries)

When there is a leak in the capillaries, the metarteriole can contract to restrain circulation through the capillaries and blood can go direclty to the venules (capillary shunt) by AV anastomosis

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16
Q

What is the average diameter of a capillary?

A

7-8um diameter
just enough for RBC to pass (7umm diameter)

17
Q

What is the volume and flow of blood in the capillaries compared to the aorta?

A

Volume of capillaries = 800 times larger than in aorta

Flow in capillaries = 0.3 mm/sec (VERY SLOW) → allows metabolic echange with tissues
Flow in aorta = 320 mm/sec

*Capllaries are like a lake within a flowing river

18
Q

What are 5 different functions of the capillaries?

A
  1. Exchange
  2. Nutrition
  3. Thermoregulation
  4. Blood pressure regulation
  5. Inflammation
19
Q

How do the metarterioles react in cold/hot temperatures?

A

Cold: Metarteriole relax → more blood flows through capillaries → more heat brought to the tissue to prevent freezing (ex: red cheeks)

Hot: Metarteriole relax → more blood flows through capillaries → heat dissipation

20
Q

What are the different type of capillaries?

A

Structural variations allow different levels of metabolic exchange
Permeable → Fenestrated vs Sinusoids
Impermeable/Continuous

*Impermeable and fenestrated look the same in a light microscope, need to see EM to find differences

21
Q

What is the structure of permeable sinusoid capillaries?

A

*ex: SPLEEN, Liver

  • Spindle shaped endothelial cells separated (no tight junctions between them, potentially gaps allowing passage of white and red blood cells)
  • Cells are maintained by network of reticular fibers (type III collagen, fibrocytes)
  • Larger irregular lumen
  • No Basement Membrane
22
Q

What are the common characteristics of fenestrated and impermeable capillaries?

A
  • Zonula Occludens (tight junctions) connect the endothelial cells
  • Both rest on a BM
  • Plasmalemmal / Pinocytic vesicles shuttle proteins from lumen → CT
  • Trans-endothelial channels (can open or close)
23
Q

What are the differences between fenestrated and impermeable capillaries?

A

Fenestrated capillaries have fenestrations within the endothelial cells, most them have diaphragms
*Albumin can pass through the fenestrations

24
Q

In which tissues are impermeable/continuous capillaries vs fenestrated capillaries found?

A

Impermeable/continuous capillaries → nervous tissue, skeletal, cardiac, smooth muscle, skin, lung, lymphatic organs

Fenestrated capillaries → Intestinal mucosa, pancreas, salivary glands, endocrine glands, renal glomerulus of kidney

25
Q

Which substances can go through which transport mechanisms from the lumen → CT of the capillaries ?

A
  1. Lipid soluble subtances (VitA) → diffuse freely through all capillaries
  2. Small water soluble molecules < 10Å and ions → trans-endothelial channels
  3. Molecules < 90Å → Pinocytic vesicles
  4. Molecules > 90Å → fenestrations
26
Q

How do the hydrostatic pressure and osmotic pressure vary from metarteriole to postcapillary venule in the capillaries?

A

Arterial end → High Hydrostatic pressure, Low Osmotic pressure → loss of H2O

Venous end → Low Hydrostatic pressue, High Osmotic pressure → recovery of H2O

*Net liquid loss in the CT → drained through the lymphatic vessels

27
Q

What are the characteristics of lymphatic vessels?

A
  • No RBC
  • Very thin endothelial cells → without occluding and gap junctions
  • No Basement Membrane
  • Endothelial cells anchored to the CT fibers (Type I and III collagen, elastic fibers in larger vessels)
  • Valves → folds of the wall projecting in the lumen
  • Large lymphatic vessels (ex: thoracic duct) have smooth muscle cells in their walls
28
Q

What are the 4 main functions of Endotheliums?

A

1) Permeability
2) Metabolic function
3) Production of Vasoactive substances
4) Anti-thrombigenic function → Thrombi form from a cascade of events that produce fibrin from blood fibrinogen → grows to complete obstruction of local flow → Emboli can detach and obstruct distant blood vessel

29
Q

How are Endothelium involved in metabolic functions?

A
  • Conversion of Angiotensin I → Angiotensin II
  • Inactivation of bradykinin (stimulator of smooth muscle contraction) and or serotonin, prostaglandins, norepinephrine, etc.
29
Q

Which vasoactive substances are produced by the endothelium?

A
  1. Endothelin (vasoconstrictive):
    - Binds to Endothelin receptor
    - Receptor converts PIP → IP3
    - Increase in intracellular Ca2+ in smooth muscle cells → Contraction
  2. Nitric Oxide (relaxing factor)
30
Q

How does blood clotting occur?

A

When damage to a blood vessel → platelets immediately adhere to cut edges → release chemicals that attract more platelets → platelet plug forms to stop external bleeding

Fibrin (Factor Ia) = fibrous, non-globular protein involved in blood clotting
Formed by action of protease thrombin on fibrinogen → polymerize into fibrin
Fibrin + platelets forms hemostatic plug/clot over wound site

31
Q

What is an atherosclerotic plaque?

A

Build up of fat in the artery wall → thins the lumen of the artery → can possibly rurpture the endothelium → exposes CT to protease thrombin → fibrin clot which blocks the blood vessel

32
Q

What is the Thoracic duct and its function?

A

It is a Large lyphatic vessel
Empties into venous system at the junction of jugular and subclavian veins

ANAT 261 (21 decks)

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