Histo 2

Question 1

Tunica Intima

1. Endothelium
2. Basal Lamina
3. Subendothelial Layer

Answer 1

1. single layer of squamous epithelial cells
2. thin EC layer (collagen, proteoglycans, glycoproteins)
3. consists of loose areolar CT
   a. Links endo layers to others
   b. Internal Elastic Membrane: sheet like layer of fenestrated elastic material within arteries and arterioles

Question 2

Tunica Media

Answer 2

• layers of smooth m.
• extends from internal to external elastic membrane (layer of elastin that separates the tunica media and adventitia)
• varying amounts of elastin, reticular fibers, and proteoglycans

Question 3

What’s the thickest layer in the arteries? veins?

Answer 3

1. Tunica Media

3. Tunica Adventitia

Question 4

Tunica Adventitia

Answer 4

• longitudinally arranged collagenous tissue with few elastic fibers
• merges with loose CT surrounding the vessels (adheres to other structures like nerves

Question 5

What are/where do we find vasa vasorum and nervi vasorum?

Answer 5

1. Tunica Adventitia (large As and Vs); supply blood to the vascular walls to themselves
2. Tunica Adventitia; ANS input that controls contraction of vascular smooth m.

Question 6

Key features of Large Arteries

Answer 6

• elastin forms concentric sheets/lamellae between muscle layers (lamellae increase with age)
• NO fibroblasts
• smooth m synthesizes collagen, elastin, ground substance of ECM
• strong pressure of systole expands the arterial walls
• expanded lumen size reduces pressure, and allows strong blood flow to continue during diastole

Question 7

Key features of Medium Arteries

Answer 7

• more smooth m and less elastin
• smooth m is arranged in a spiral fashion, and produce ECM components
• thick tunica adventitia (about same size as tunica media)

*Prominent internal elastic membrane

Question 8

Key features of Small Arteries

Answer 8

• up to 8 layers of smooth muscle in tunica media

- internal elastic membrane

Question 9

Key features of Arterioles

Answer 9

• 1-2 layers of smooth muscle in tunica media
• may or may not have internal elastic membrane
• function as flow regulators for capillaries

Question 10

Key features of capillaries

Answer 10

• site of metabolic exchange

- diameter is often smaller than RBC

Question 11

What are/where do we find perictyes?

Answer 11

1. perivascular contractile cells with branching cytoplasmic processes (enclosed in BL, and continuous with endothelium)
2. Controlled by NO to promote stability of capillaries and post capillary venules

Question 12

What is the innermost aspect of the tunica media made of ?

Answer 12

single layer of endothelial cells

• connected via gap junctions
• support the basement membrane and produce collagen
• metabolically involved in blood coagulation and thrombosis (local vasoconstriction/dilation)

Question 13

What are the 3 types of capillaries?

Answer 13

1. Continuous
2. Fenestrated
3. Sinusodal

Question 14

How does molecular exchange occur in the three types of capillaries?

Answer 14

1. Continuous: diffusion or transcytosis
2. Fenestrated: limited by size
3. Sinusoidal: open exchange

Question 15

Where do we find the three types of capillaries?

Answer 15

1. Continuous: throughout body
2. Fenestrated: endocrine glands, sites of fluid/metabolism absorption (gallbladder, kidneys)
3. Sinusoidal: bone marrow, liver, spleen

Question 16

What are met arterioles?

Answer 16

first branch off of arteriole supplying tissues

Question 17

What are precapillary sphincters?

Answer 17

regulate blood flow through true capillaries (can be open or closed to allow/not allow blood flow)

Question 18

What are true capillaries?

Answer 18

branch from metarteriole, lack smooth m., may have pericytes

Question 19

What are thoroughfare channels?

Answer 19

distal end of metarteriole (no smooth m); connect to to post capillary venule

Question 20

What happens when precapillary sphincters contract?

Answer 20

• they shunt blood flow, and prevent exchange within true capillaries
• blood is forced to enter venous return more quickly

Question 21

Key features of venules

Answer 21

• receive blood from capillaries
• subclasses: post capillary (no true tunica media) and muscular venules (1-2 layers of smooth m., thin tunica adventitia)

Question 22

Key features of small veins

Answer 22

• continuous with muscular venules
• all three tunica layers
• tunica media is 2-3 layers, and have thicker tunica adventitia

Question 23

Key features of medium veins

Answer 23

• diameter of up to 10mm
• travel with muscular arteries
• thicker tunica media and adventitia
• contains valves

Question 24

Key features of large veins

Answer 24

• diameter of greater than 10mm
• tunica adventitia:
  a. the thickest layer
  b. contains collagen, elastic fibers, and fibroblasts
  c. contains longitudinal smooth m cells
• tunica media:
  a. thin with circumferentially arranged smooth m. cells, collagen fibers, and some fibroblasts
• tunica intima:
  a. thin
  b. blends with tunica media

Question 25

What tunica may contain valves?

Answer 25

intima

Question 26

Between arteries and veins: who has the larger lumen? thinner walls? commonly collapsed lumen?

Answer 26

1. vein
2. vein
3. vein

*hallmarks of the veins

Question 27

Key features of Lymphatic Vessels

Answer 27

• collect lymph, and return it to venous supply
• serve as adjuncts to the BVs
• unidirectional
• contain all three tunics and posses valves
• tight junctions to repent leakage

*hallmarks: extremely thin; no blood in the lumen

Question 28

Key features of Lymphatic Capillaries

Answer 28

• closed ended tubes found amount capillary beds
• have one way valve to collect lymph
• incomplete basal lamina to increase permeability

Question 29

What is the role of anchoring filaments in lymphatic capillaries?

Answer 29

hold opening between endothelial cells in place (collapse to prevent back flow)

Question 30

Lymph flow…

Answer 30

capillaries—>vessels–>trunks–>right lymphatic duct—>thoracic duct—>brachiocephalic v.