Structural Characteristics of veins
- -Thin walled
- -3 layers- intima, media, adventitia – thinner media than arteries
- -Venules smallest
- -Valves are an extension of the intimal layer
- -Bicuspid for unidirectional flow
carry blood from the superficial system to the deep system
Posterior Arch Vein
has 3 ankle perforators and plays a major role in the development of venous stasis ulcers
Intracranial and Lower extremity
venous sinuses: intracranial
spaces between the duramater and periosteum that drain the blood into the IJV- internal jugular vein
venous sinuses: Lower extremity
dilated channels in soleal and gastrocnemius muscles à drain into the PTV-posterior tibial veins and peroneals veins… major part of the calf pump muscle
empty the lateral leg
PTVs posterior tibial veins
empties posterior leg
ATVs anterior tibials veins
empties anterior leg
formed from the anterior tibial veins and the tibeoperoneal trunk
popliteal vein becomes the femoral vein when it passes through the adductor hiatus
CFV common femoral vein
formed from the joining of the SFV-superficial femoral vein and the PFV- profundal femoris vein
EIV- external iliac vein
becomes EIV external iliac after passing the inguinal ligament
CIV- common iliac vein
formed from the joining of the external iliac and the internal iliac vein
inferior vena cava
formed by the joining of both common iliac veins and at the level of L4-L5 empties into the right atrium
SSV- small saphenous vein or LSV lesser saphenous vein
ascends the back of the calf
GSV- great saphenous vein
longest vein in the body originates on the dorsum of the foot and travels medially to the saphenofemoral junction at the level of the common femoral vein
empties the lateral hand and forearm
empties the medial forearm
formed from the confluence of the radial and ulnar veins
formed from the confluence of the brachial and basilic vein
formed from the confluence of the axillary vein and cephalic vein
formed from the confluence of the subclavian and Internal jugular (brachiocephalic veins)
SVC-superior vena cava
formed by the confluence of the right and left innominate veins and dumps into the right atrium
empties the medial aspect of the arm
empties the lateral aspect of the arm
Venous Valve Anatomy
- -Critical role in maintaining proper direction of venous flow
- -The number of valves varies according to genetics.
- -Pressure changes control opening & closing of valves.
- -Specialized valves, called an Ostial valves
Veins without valves
- Soleal sinuses
- EIV external iliac vein (25% have valves)
- CIV common iliac vein
- IIV internal iliac vein
- Innominate veins
- SVC - superior vena cava
- IVC (*can occur)
Veins with Valves
- -GSV great saphenous 12 (most below the knee)
- -SSV superficial saphenous vein 6-12
- -Perforators - each contains a valve
- -PTV -ATV-Pero 7-12
- -Pop and Fem 1-3 each
- -CFV 1
- Jugular 1
*Variable # in upper veins
Two kinds of pressure exerted on the venous walls
- Intraluminal pressure
- Interstitial pressure
The difference between intraluminal and interstitial pressures is called the
transmural pressure relates to
to the volume of the blood that is within the vein at any given time, and as such, the cross-sectional shape of the vein will give you clues as to how much relative pressure there is.
The greater the intraluminal pressure
the greater the volume of flow, and therefore the larger and more circular the venous cross-sectional appearance will be.
The lower the intraluminal pressure
the lower the volume of flow will be, and the resulting appearance will become more elliptical or “dumbbell” shaped.
The ability of the veins to accommodate relatively large changes in volume is termed
The high degree of compliance that veins exhibit (unlike arteries),
has a strong influence on venous resistance.
When the volume of flow is high, there is a corresponding high intraluminal pressure.
When this occurs, the cross-sectional area of the vein will be fully distended (circular).
When there is low intraluminal pressure and a correspondingly low volume of flow (which is the “natural state” of the vein
because the veins are seldom completely full of blood); the shape of the vein is elliptical (or dumbbell).
Hydrostatic pressure =
weight of the column of blood extending from the heart to the level where the pressure is being measured.
In an individual who is supine, the hydrostatic pressure is approximately equal to
In a standing position, the hydrostatic pressure measured at the ankles is approximately
If an extremity is raised above the level of the heart hydrostatic pressure
At rest the veins are reservoirs for blood. During physical activity
the blood is propelled toward the heart.
The calf muscle pump acts as the power source that overcomes the forces of gravity & propels the blood toward the heart
As the calf muscle pumps & the venous blood is pushed forward, proximal valves are forced open & distal valves close.
In normal venous systems, the contraction of the calf muscles force the blood toward the heart; and the relaxation of the calf muscles allows
the blood to move from the superficial veins into the deep venous system
Venous valves keep the blood from moving
When valves are incompetent, flow will be both antegrade and retrograde.
What happens during muscle RELAXATION
When the calf or leg muscles relax, a potential “space” is created in the deep venous system. This physiologic process reduces pressure in the peripheral venous system, and permits the blood to flow from the superficial veins into the deep system by way of the perforators.
Respiratory activity significantly
affects venous flow in a recumbent or supine person
the diaphragm to descend or lower. Intrathoracic pressure will increase while intraabdominal pressure decreases; resulting in an increase of the inflow of blood from the arm and head veins, and cessation of the blood flow coming in the lower extremity veins
Expiration causes the
opposite to occur: Intrathoracic pressure will decrease, leading to an increase in venous flow from the lower extremities and a cessation of flow from the upper extremities.
In the portal vein of an adult there is almost
no variation of flow with respiration
During the Valsalva maneuver
As patient performs the Valsalva maneuver, all venous return stops. This causes a decrease in the volume of blood going back to the heart, which results in the loss of the spontaneous common for moral venous waveform
CONTRAINDICATIONS TO PERFORMING THE VALSALVA MANEUVER
- -Severe coronary artery disease
- -Acute myocardial infarction
- -Moderate to severe hypovolemia (decreased blood volume)
Defining the Valsalva Maneuver
- 1.Patient draws in a deep breath & holds it, & then bears down as if having a bowel movement.
- 2.Causes a significant elevation of both the intrathoracic and intra-abdominal pressures; thus eliminating the pressure gradient between the thoracic cavity and the peripheral venous circulation. è No gradient = no flow.
- 3.If all venous waveform signal is lost (i.e. venous flow is halted) & then the venous waveform signal is augmented/enhanced when the patient releases the deep breath…this is a normal response to the Valsalva maneuver & the valves are “competent”
If, when the patient bears down, the venous waveform signal is augmented,
this is an abnormal response to the Valsalva maneuver, and flow reversal from incompetent valves is indicated.