Histology Vessels

موضوع: Histology Vessels الخميس 01 أبريل 2010, 2:59 am

I. Structure of Blood Vessels Walls

[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة]

A. Three layers

1. Tunica intera

a. Inner most layer

b. Endothelium

i. Simple squamous

c. Some larger vessels have subendothelium

i. Loose connective tissue

ii. Basement membrane

2. Tunica media

a. Middle layer

b. Circularly arranged smooth muscle

c. Chemical and nervous control of degree of contraction

i. Sympathetic NS

d. Change in diameter

i. Vasoconstriction

ii. Vasodilation

3. Tunica externa

a. Made of collagen fibers

b. Function

i. Protection

ii. Reinforcement

iii. Anchor to surrounding tissue

c. Accessory tissues

i. Nerve fibers

ii. Lymphatic vessels

iii. Elastic network

iv. Tiny blood vessels within layer-vasa vasorum

II. Arterial System

A. Classification based on size and function

1. Elastic (conducting) arteries

a. Characteristics

i. Thick-walled

ii. Near heart

iii. Largest diameter

iv. More elastic

v. Large lumen

b. Properties

i. Dampen BP changes associated with heart contraction

ii. Passive accommodation results in smooth flow of blood

c. 1.0 - 2.5 cm

2. Muscular arteries-distributing arteries

a. Distal to elastic arteries

b. Deliver blood to specific organs

c. Thick media layer

i. More smooth muscle

d. 0.3 - 1.0 cm

3. Arterioles

a. Determine flow into capillary beds

b. Mostly smooth muscle

c. 10 µm - 0.3 cm

4. Capillaries

a. Smallest blood vessels

i. 8 - 10 µm

b. Tunica interna only

c. Exchange of materials

B. Types of capillary

1. Continuous

a. Uninterrupted endothelial cells

b. Incomplete tight junctions

i. Intercellular clefts

2. Fenestrated

a. Endothelial cells have oval pores

i. Fenestrations

b. Pores permit greater permeability

3. Sinusoidal

a. Modified, leaky capillaries

b. Large molecules can pass through

C. Capillary beds

[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة]

1. Capillaries act as networks-capillary beds

2. Microcirculation

a. Arteriole to venule

3. Parts of a capillary bed

a. Vascular shunt

i. Connects arteriole with venule

b. True capillaries

D. Sequence of blood movement through capillary bed

1. Terminal arteriole

2. ****teriole

a. True capillaries branch off

i. Pre-capillary sphincter controls blood flow into capillary

3. Thoroughfare channel

a. Capillaries rejoin

4. Post-capillary venule

III. Venous System

A. Types of vessels

1. Venules

a. 8 - 100 µm

b. Characteristics vary with size

i. Little muscle

ii. Thin externa

2. Veins

a. Formed from venules

b. Thinner walls and less muscle than arteries

c. Little muscle in media

i. Mostly elastin

d. Externa is thickest wall layer

B. Capacitance vessels

1. Veins act as reservoirs

a. Large lumens

b. Low blood pressure allows walls to thin

2. Venous valves

a. Prevent backflow

b. Folds of interna

the end
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