1. Vascular Histology Flashcards

1
Q
Overview of Blood Vessels’ Histology
 Classification according to:
• Vessel wall structure and composition:
• \_\_\_\_.
• Individual \_\_\_\_.
• Lumen diameter.
• \_\_\_\_.

Aorta: highly muscular, rich in SM and elastin > operates at a very high ____ regime; just downstream of the heart, the high pressure is due to the pumping of heart

Vena cava: large lumen that houses large volume of blood > operates in a low ____ environment, and they serve as ____ for large volumes of blood (arteries do not have that function)

Capillaries: involved in shunting of blood from arteriole to vein, and exchange substances, fluids and gases

A

thickness
layer (tunica) thickness
working pressure

blood pressure

blood pressure
resorvoirs

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2
Q

General Structure of the BV

  • Tunica Intima:
  • ____
  • +/- Connective Tissue
  • +/- Internal Elastic Lamina
  • Tunica Media:
  • ____
  • Collagen Fibers
  • Elastic Laminae
  • Tunica Adventitia:
  • ____
  • Vasa vasorum

Every BV shows this general structure:
Lumen: tunica intima, the cells lining that are in contact with fluid = endothelium (____); may find a CT or internal elastic lamina below (depending on the vessel)

Next: tunica media, presence of SM > secrete an ECM rich in elastic lamina (contractile) and in collagen (resistance)

Outside: tunica adventitia, mostly made of CT (some SM, but not as much as TM), and the presence of ____ (BV that vascularizes a BV)

A

endothelium
smooth muscle cells (SMCs)
connective tissue

simple squamous

vasa vasorum

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3
Q
Endothelial Biology
 Endothelium: simple squamous epithelium. 
• Biological functions:
• Modulation of smooth muscle activity:
• SM relaxing factors: e.g. \_\_\_\_.
• SM contraction factors: e.g. \_\_\_\_.

• Prevention of blood clotting:
• Secretion of ____: inhibits platelet binding to
the endothelium.

  • Initiation of blood clotting cascade:
  • Secretion of ____: trigger of common pathway of blood coagulation.
  • Regulation of traffic of inflammatory cells:
  • ____ trans-endothelial migration.
A

NO
endothelin 1

prostacyclin

tissue factor

selectin-mediated

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4
Q

Arteries: Structure

Within the lumen > RBC and some WBC are interspersed > indication of ____

Underneath the endothelium and BL there may be a ____ of CT and an ____ (not present all the time)

Difference between artery and vein: ____; here it is a deeply stained layer due to high levels of SM cells (making a dense ECM composed of elastin and collagen) resulting in a very muscular layer (veins are the opposite)

Tunica adventitia > ____

If artery is thick enough, in adventitia you will see the ____; when the BV becomes so large > how do you provide the SMC with metabolites/glucose > in adventitia there is going to be innervation of BV (everything is exchanged at the level of the vaso vasorum [adventitia], not at the lumen)

A

BV

subendothelial layer
internal elastic lamina

tunica media

loose CT

vaso vasorum

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5
Q

Veins: Structure and Function

The lumen may be wide, but the individual layers are ____ (opposite of artery)

Subendothelial layer only in ____; no internal elastic lamina in most examples

In many veins > valves (projections of ____ into the lumen of the vein) > prevent the backflow of blood (important because it is a low pressure environment); ____ do not have valves

TM is much ____ than arteries, the orientation of SMC is not as ____

TA (also much thinner) > loose CT > ____ present in larger veins

A

thinner
larger veins

endothelium of TI
large veins

thinner
regular

vaso vasorum

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6
Q

Classification of the Blood Vessels

• Elastic Arteries (____ mm diameter):
• ____ vessels from the heart: Receive blood
under pressure.
• Aorta, pulmonary artery, carotid, subclavian.

  • Muscular Arteries (Large ____ mm; small ____ mm):
  • Selective ____ to different organs.
  • Renal, hepatic, superior and inferior mesenteric.

• Small Arteries and Arterioles (____ μm):
• ____ vessels: regulate systemic blood pressure
and blood flow through capillaries.

  • Capillaries (____ μm):
  • ____ vessels.
• Venules (\_\_\_\_ μm):
• Migration of \_\_\_\_ to tissues
.
• Small, Medium, and Large (\_\_\_\_ mm) Veins:
• \_\_\_\_ or \_\_\_\_ vessels.
A

10-25 mm
conducting

2-10
0.1-2
distribution

10-100
resistance

5-10
exchange

50-100
WBCs

0.1-30
capacitance
reservoir

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7
Q

General Structure of the Elastic (Conducting) Arteries I

• Aorta, pulmonary artery, carotid, subclavian.

• Tunica Intima - Thin
• Endothelium – \_\_\_\_.
• Subendothelium – \_\_\_\_.
• Internal Elastic Lamina (IEL) – a.k.a. elastica
interna, densely-packed \_\_\_\_.
  • Tunica Media - Thick:
  • ____ with elastic laminae (or lamellae).
  • External Elastic Lamina (EEL) – a.k.a. elastica externa, densely-packed ____.

• Tunica Adventitia - Thin
• Connective Tissue.
• ____ – vascular plexuses within the
vessel wall.

Undergo cycles of ____ due to the fact that the heart is pumping blood a v high pressures

Reason why they’re rich in SM and EF > to cope with the changes in BP; if they were not ____ > the vessel would rupture

By absorbing energy from cycles of pumping > they ____ out the pressure; closer to heart you see ____ cycles, and the farther you travel the cycles ____ due to the absorption of energy by the elastic fibers (act as shock absorbers)

Majority of thickness: ____

A

endothelial cells
CT
elastic laminae

concentric SMCs
elastic laminae

vasa vasorum

pumping

elastic

smooth
larger
shrink

tunica media

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8
Q

General Structure of the Elastic (Conducting) Arteries II

Endothelial cells > subendothelial layer > internal elastic lamina > TM: SMC, largest component, organized in a ____ manner, between layers of SMC > ____ (organized in circumferential manner) > mostly involved with ____ of the vessel > external elastic lamina (similar to IEL, but more densely packed) > TA: loose CT > presence of ____, in additions to ____

A
circumferential
elastic lamina
expansion
fibroblasts
BV
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9
Q

General Structure of the Elastic (Conducting) Arteries II

  • Tunica Intima - Thin
  • Endothelium – epithelial cells.
  • Subendothelium – CT.
  • Internal Elastic Lamina (IEL) – elastin.

Can distinguish the ____ between the ____ (SECT, presence of fibroblasts)

Separating intima from media: IEL, doesn’t look very different from the ____ (fiber, but lamellae bc they look like sheaths that CF-organized) found in the TM

A

endothelial cells
connective tissue

elastic lamina

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10
Q

General Structure of the Elastic (Conducting) Arteries III

  • Tunica Intima - Thin
  • Tunica Media - Thick:
  • Concentric ____.
  • Concentric ____.
  • Interspersed collagen fibers.
  • ↑ ____ (and ↓ ____) in vessels with smaller diameter.
  • ____ External elastic lamina (EEL) – distinct boundary between ____ and ____ in smaller vessels.
  • Tunica Adventitia - Thin
A
SMCs
elastic laminae
SM
elastic laminae
\+/-
tunica media
tunica externa
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11
Q

General Structure of the Elastic (Conducting) Arteries IV

• Tunica Adventitia – Thin:
• CT that gradually merge with ____.
• ____ (“vessels of the vessel”) – small arteries and veins that that form
____.
• ____ (“nerves of the
vasculature”) – autonomic nerve endings.
• ____ vessels.

____ may be surrounding the BV, nerves and lymphatics

A
surrounding tissues' CT
vaso vasorum
capillary plexuses
nervic vascularis
lymphatic
adipose
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12
Q

General Structure of the Muscular (Distributing) Arteries I

• Examples: brachial, femoral, radial.
• Selective distribution and blood flow
regulation to different organs.

• Tunica Intima:
• Endothelium.
• +/- Subendothelium.
• Internal Elastic Lamina – often showing
folding (“\_\_\_\_”) due to contraction of
the TM.
• Tunica Media:
• Lower abundance of \_\_\_\_. 
• Higher abundance of \_\_\_\_.
• External Elastic Lamina – present in
larger vessels.
• Tunica Adventitia:
• Equal thickness to \_\_\_\_ (or thicker). 
• Vasa vasorum, nervi vascularis.

May or may not be presence of a ____

IEL > folding due to it being quite dense, and there is no pressure acting on elastin and it has such a powerful recoil that it recoils the entire vessel and it becomes smooth/scalloped (doesn’t happen in aorta bc TM is so ____ it prevents scalloping)

Higher abundance of SMC compared to elastic lamina within the TM

TA > may be as thick as the TM, or it may be thicker > still contains ____

A
scalloped
elastic laminae
SM bundles
TM
subendothelium
dense
innervation
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13
Q

General Structure of the Muscular (Distributing) Arteries II

Smaller muscular arteries:
Tunica intima almost exclusively
____.
Lower number of layers of ____ in the TM.
Internal and external elastic laminae less ____.

Presence of ____ in a longitudinal manner

A

endothelium
SMCs
prominent
vaso vasorum

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14
Q

Small Arteries and Arterioles I

• Resistance vessels:
• Regulation of ____: SMC
contraction → ____ → ____
blood flow.

  • Tunica Intima:
  • Endothelium
  • No ____.
  • May show ____.
  • Tunica Media:
  • ____ of SMCs circumferentially disposed.
  • No ____.
  • Tunica Adventitia – ____.
  • Collagen and isolated elastic fibers.

Presence of ____; striated muscle

A

peripheral blood pressure
peripheral resistance
lower

subendothelium
IEL

1-2 layers of SMCs
EEL

thin

adipocytes

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15
Q

Small Arteries and Arterioles II

  • Tunica Intima:
  • Endothelium
  • No ____.
  • May show IEL.
  • Tunica Media:
  • ____ of SMCs circumferentially disposed
  • No____.
  • Tunica Adventitia – thin.
  • Collagen and isolated elastic fibers.

Can use size of ____ to gauge how big the vessel is

A

subendothelium
1-2 layers
EEL
RBC

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16
Q

Microcirculation: Capillary Beds
• Exchange vessels:
• Capillary network surface area: ____ m2.
• Gas exchange: ____ to tissues, ____ removal.
• Metabolite exchange.
• ____ permeability.

  • Microvascular bed:
  • Terminal ____.
  • Capillary bed:
  • ____ channels (large capillaries) – continuous blood flow.
  • ____ capillaries (small) – intermittent blood flow.
  • Postcapillary ____.
A

6000
O2
CO2
selective

arteriole
preferential or thoroughfare
true
venules

17
Q

Microcirculation: Capillary Beds

Left panel: ____ supplies the blood (small arteries) which branch into capillaries > diameter of the lumen shrinks and a complicated network > exponential increase in ____ that is available for exchange

True capillaries can be controlled in ____ of blood (modulated, controllable and the flow may be intermittent)

On the other side of the bed > ____ (no SMC [???]) > how blood exits the capillary bed

Within the capillary bed > ____ channel: a arteriole/capillary that bypasses the bed > continuous flow of blood from arterial side to the venous side; and a ____: controlling blood flow through the capillary bed

A

terminal arteriole
SA

volume

post-capillary venule

thoroughfare
metarteriole

18
Q

Microcirculation: Capillaries

• Exchange vessels.
• Extremely small lumen (5-10 μm; ~
diameter ____) and thin wall (____ μm).
• Endothelium surrounded by a ____, ____*, and CT.

  • Pericytes: ____ cells that wrap around small arterioles, venules and capillaries

Diameter of RBC almost occupies the entire lumen of the capillary (usually have the size diameter as the size of a RBC); travel ____, exchange substances (like oxygen from RBC)

Surrounding the endothelium: no TM or TA; outside of the BM you see pericytes and maybe some CT

A

RBC
0.5
basement membrane
pericytes

SM-like contractile

slowly

19
Q

Microcirculation: capillaries

Continuous capillary > endothelium/BL are ____
Fenestrated capillary > endothelium is ____ and BL is ____
Discontinuous capillary > endothelium/BL are ____

  • For all types, recall that endothelium is a ____ epithelium.
A

continuous
discontinuous
continuous
discontinuous

simple, squamous

20
Q

Capillary Types: 1. Continuous

  • Complete endothelium.
  • Continuous basal lamina.
  • ____:
  • Similar to SMCs and contribute to contraction of the capillary.
  • Found in muscle, brain, thymus, bone, ____.

The lumen is completely lined by endothelial cells, and deposit a continuous BL

Found in organs where exchange of gases is ____, and muscles and other organs

Surrounding the capillary you have the ____ of the pericyte

A

pericytes
lung
active (lung)

cytoplasmic extension

21
Q

Capillary Types: 2. Fenestrated

  • ____ endothelium:
  • ____ (from Latin for “window”).
  • With or without ____.
  • ____ basal lamina.
  • Present in tissues with substantial ____ transport.
  • Intestines, endocrine glands, renal glomerulus, ____.

Two types of fenestrated capillaries > occluded with a diaphragm (act as a molecular sieve for ____) or those lacking a diaphragm

Intestine has fenestrations with diaphragms (____ allows the traffic of certain substances only)

A

discontinuous
fenestrations
diaphragms

continuous
fluid
kidney tubules

filtration

selectively

22
Q

Capillary Types: 3. Discontinuous (Sinusoid)

• Incomplete endothelium.
• Discontinuous basal lamina (maybe absent, e.g. ____).
• Found in tissues with a close spatial relationship
between the ____ and the ____; liver and
spleen.
• In spleen, endothelial cells are ____ and
protrude into the lumen; ____ can pass through the walls.

So large that it allows the travel of WBC, or in liver (allows passage of large molecules, no BL present)

A
liver
parenchyma
blood
elongated
RBCs
23
Q

Post-capillary Venules

• Small venules (up to ____ μm in diameter): • Surrounded by ____.

• Large venules (\_\_\_\_ μm in diameter): 
• Tunica Intima – Endothelium.
• \_\_\_\_ surround the endothelium.
• Tunica Media - \_\_\_\_ layers of
SMCs.
• Tunica Adventitia – thin or absent.

Less SMC than ____

• Preferred site of migration of ____ into tissues (____).

A

40-50
pericytes

50-100
pericytes
1-2 longitudinal

arterioles

blood cells
diapedesis

24
Q
Veins: Structure and Function
• Low \_\_\_\_, high \_\_\_\_ vessels.
• Compared with arteries:
• Thinner walls.
• Larger lumen.
• Less elastic.
  • Distinction between Tunica Media and Tunica Adventitia not always ____.
  • ____ contains fewer SMCs than arteries.
  • Unidirectional movement of blood back to the heart depends on:
  • Contraction of surrounding ____.
  • Valves (projections of the ____) that ensure one-way blood flow.

Contracts following skeletal muscle contraction (____, not SM)

A

pressure
capacitance

clear
tunica media
skeletal muscle
tunica intima

voluntary

25
Q

Small Veins

• Small Veins:
• Tunica Intima – endothelium with \_\_\_\_.
• Tunica Media – \_\_\_\_ SM bundles may or
may not form \_\_\_\_ layer.
• Tunica Adventitia – collagen fibers.

When contraction surrounding veins, and heart is creating a suction, the valves open; but once pressure stops, the valves will close > ensure unidirectional flow

Deeply stained in red are bundles of SM > the structure is not as ____ as the arteriole side > may not form a continuous layer

A

valves
long
continuous

organized

26
Q

Medium Veins

• Medium Veins:
• Tunica Intima – endothelium with \_\_\_\_.
• Tunica Media – \_\_\_\_ layers of SMCs in long
bundles separated by \_\_\_\_.
• Tunica Adventitia – collagen fibers.

More ____ than circumferential

Embedded entirely in adipose tissue

A

valves
2-4
fibroblasts
longitudinal

27
Q

Large Veins I

  • E.g. ____.
  • Tunica Intima:
  • Endothelium.
  • ____.
  • Tunica Media:
  • ____ compared to arteries of similar diameter: fewer elastic fibers.

• Tunica Adventitia:
• Usually the thickest ____: loose CT, thick
elastic fibers, ____ SM bundles.

Presence of a subendothelial CT; nothing separating the intima and media (no ____)

A

vena cava
subendothelial CT

thin

tunic
longitudinal

IEL

28
Q

Large Veins II

• E.g. vena cava.
• Tunica Intima:
• Endothelium.
• Subendothelial CT.
• Tunica Media:
• Thin compared to arteries of similar diameter: fewer elastic fibers.
• It may be poorly ____ (____ SMC layers), or ____.
• Tunica Adventitia:
• Usually the thickest tunic: loose CT,
thick elastic fibers, longitudinal SM bundles.

SM bundles are usually deposited in a ____ rather than a circumferential manner; most of the tissue is still ____ (deposited by fibroblasts)

A

developed
10
absent

longitudinal
loose CT