Because the walls of the veins are thinner and less rigid than arteries, veins can hold more blood. Almost 70 percent of the total blood volume is in the veins at any given time.
Why blood is collected from veins and not arteries?
Vein: Transverse Cross Section. Located throughout the body, veins return deoxygenated blood to the heart. Veins have valves to prevent backflow of blood and larger lumens (internal spaces) than arteries.
Why do veins carry blood to the heart?
The arteries (red) carry oxygen and nutrients away from your heart, to your body’s tissues. The veins (blue) take oxygen-poor blood back to the heart. Arteries begin with the aorta, the large artery leaving the heart. They carry oxygen-rich blood away from the heart to all of the body’s tissues.
What happens if we take blood from artery?
Collecting blood from an artery typically hurts more than drawing it from a vein. Arteries are deeper than veins, and there are sensitive nerves nearby. You also may feel lightheaded, faint, dizzy, or nauseated while your blood is drawn.
Which vein is suitable for blood collection?
The median cubital and cephalic veins are preferred for blood sampling, but other arm and hand veins may be used. The cephalic vein is located on the lateral (radial) side of the arm, and the basilic vein is located on the medial (ulnar) side.
Do veins carry blood away from the heart?
The circulatory system is made up of blood vessels that carry blood away from and towards the heart. Arteries carry blood away from the heart and veins carry blood back to the heart.
Do all arteries carry oxygen-rich blood?
Most arteries carry oxygenated blood, and most veins carry deoxygenated blood; the pulmonary arteries and veins are the exceptions to this rule.
Which blood vessels carry blood to the heart?
Veins. Veins carry blood toward the heart. After blood passes through the capillaries, it enters the smallest veins, called venules. From the venules, it flows into progressively larger and larger veins until it reaches the heart.
What is the normal range for blood gases?
The following are normal ranges for results of a blood gas test: pH: 7.35–7.45. partial pressure of oxygen (PaO2): 80–100 millimeters of mercury (mmHg) partial pressure of carbon dioxide: 35–45 mmHg.
Which artery is the largest?
The largest artery is the aorta, the main high-pressure pipeline connected to the heart’s left ventricle. The aorta branches into a network of smaller arteries that extend throughout the body.
What are the 3 main veins to draw blood?
The antecubital area of the arm is usually the first choice for routine venipuncture. This area contains the three vessels primarily used by the phlebotomist to obtain venous blood specimens: the median cubital, the cephalic and the basilic veins.
What is the difference between capillary blood and venous blood?
It is well known that capillary blood has higher hemoglobin (Hb) and hematocrit (Hct) values than venous blood. … In each group, venous platelet counts were significantly higher than the corresponding capillary values.
Which sites should you avoid for venipuncture?
Certain areas are to be avoided when choosing a site: Extensive scars from burns and surgery – it is difficult to puncture the scar tissue and obtain a specimen. The upper extremity on the side of a previous mastectomy – test results may be affected because of lymphedema. Hematoma – may cause erroneous test results.