Vascular Histo

Question 1

Tunica Intima

Answer 1

1) Endothelium, single layer of squamous epithelial cells
2) Basal Lamina, (Of the endothelial cells) Thin EC layer: collagen, proteoglycans, glycoproteins
3) Subendothelial layer, (Consisting of Loose CT) internal elastic membrane (Sheet-like layer of fenestrated elastic material w/in arteries and arterioles

Question 2

Tunica Media

Answer 2

Circumferentially arranged layers of smooth muscle

Relatively thick in arteries

Extends from the internal elastic membranes to the external elastic membrane–Layer of elastin that separates the tunica media and adventitia

Varying amount of elastin, reticular fibers and proteoglycans

Question 3

Tunica Adventitia

Answer 3

Longiticinally arranged collagenous tissue w/few elastic fibers

Will merge with the loose CT surrounding the vessels

Ranges from relatively thin (arterials systems) to quite thick (Venules/veins)

Question 4

Vasa Vasorum

Answer 4

Vessels of the tunica adventitia of large arteries and veins –Arterioles, capillaries and venules, supply blood to the vascular walls themselves

Question 5

Nevi Vasorum (Vascularis)

Answer 5

ANS input that controls contraction of vascular smooth muscle

Question 6

Large (elastic) Arteries

Answer 6

Largest vessels of the arterial system

Elastin formes concentric sheets/lamellae between muscles cell layers

No fibroblasts

Smooth miscles synthesizes collagen, elastin, ground substance of ECM

Strong pressure of blood pulsating during systole expands the arterial wall

Lumen size reduces pressure and allows strong blood flow to continue during diastole

Question 7

Medium (Muscular) Arteries

Answer 7

More smooth muscles and less elastin than elastic ateries

Prominent internal elastic membrane becomes apparent

Recognizable external elastic membrane is present

Smooth muscle cells are arranged in a spiral fashio, produce ECm

Relatively thick tunica adventitia, about the same thickness as tunica media

Question 8

Small Arteries and Arterioles

Answer 8

Distinguished by number of smooth muscle layers in tunica media

Small arteries have up to eight layers, will also have an internal elastic membrane

Arterioles have 1-2 layers and internal elastic membrane may or may not be present

• Slow regulators for capillary beds
• Sympathetic innervation to tunica media causes vasoconstriction
• Parasympathetic innervation to tunic media causes vasodilation

Question 9

Capillaries

Answer 9

Smallest of all blood vessels that form capillary beds

• Site of metabolic exchange
• Diameter often smaller than RBC

Question 10

Pericytes

Answer 10

Perivascular contractile cells with branching cytoplasmic processes

• Enclosed with basal lamina continuous with that of the endothelium
• Controlled by nitric oxide
• Promote stability of capillaries and postcapillary venules

Question 11

Endothelial Cells

Answer 11

Single layer of endothelial cells form innermost aspect of tunic intima

Connected via cell-cell junctions, number of junctions will alter permeability

Support the basement membrane and produce collagen

Metabolically involved in blood coagulation and thrombosis, local vasodilation/constriction

Question 12

Metarterioles

Answer 12

First brand off of arteriole supplying tissues

Question 13

Precapillary sphincters

Answer 13

Regulate blood flow thru true capillaries

Contracted sphincters with shunt blood

Prevents exchange with true capillaries

Question 14

True capillaries

Answer 14

Branch from metarterioles, lack smooth muscle

Pericytes may be present

Question 15

Thoroughfare channel

Answer 15

Distal end of metarteriole

lacks smooth muscle

Connects to a postcapillary venule

Question 16

Venules

Answer 16

Receive blood from capillaries and have a diameter as small as 0.1 mm

Sub-classified as postcapillary and muscular venules

Question 17

Small veins

Answer 17

Less than 1 mm in diameter, are continuous with muscular venules

Have all three tunics
Tunica media is 2-3 layers
Have thicker tunica adventitia

Question 18

Medium Veins

Answer 18

Have a diameter of as much as 10 mm, represents most of the named veins

Travel with muscular arteries
Thicker tunic media and adventitia
Wall is often folded around large lumen
contain valves

Question 19

Large veins

Answer 19

Have a diameter greater than 10 mm
Superior and inferior vena cava, hepatic portal vein

Tunica adventitia: thickest layer of the vessel wall, contain collagen and elastic fibers and fibroblasts, contains longitudinal smooth muscle cells

Tunica Media is thin with circumferentialy arranged smooth muscle cells, collagen fibers, and some fibroblasts

Tunica intima is thin and blends with tunica media

Question 20

Tunics in veins

Answer 20

Tunics are not as distinct or well defined, large and medium veins have all three layers

Tunica intima may contain valves, semilunar flaps consisting of a thin CT core covered by endothelial cells

Question 21

Postcapillary venules

Answer 21

Drain capillaries, true tunica media

Question 22

Muscular venules

Answer 22

have 1-2 layers of smooth muscle in tunica media

Thin tunica adventitia

Question 23

Lymphatic Vessels

Answer 23

Circulate lymph thru most parts of the body

Serve as adjuncts to the blood vessels

Lymphatic vessels are unidirectional. conveying fluid only from tissues

Lymphatic vessels collect lymph and return it to venous supply

Question 24

Lymphatic capillaries

Answer 24

Closed ended tubes found among capillary beds

Collecting lymphatic vessels

Overlapping endothelial cells form 1 way valves for collecting lymph

Incomplete basal lamina increases permeability, openings between the endothelial cells are held in place by anchoring filaments

join to form lymphatic vessels

Question 25

Tunics is lymphatic vessels

Answer 25

Have all vascular tunics and possess valves

Walls increase in thickness as vessels increases in size

Continuous tight junctions to prevent leakage

Afferent vs efferent lymphatic vessels

Question 26

Lymphatics path

Answer 26

Lymphatic capillaries
Lymphatic vessels 
Lymphatic trunks
Right lymphatic duct
Thoracic duct 
Brachiocephalic V