Cardiovascular and Peripheral Vascular System
Anatomy and Physiology Review – Cardiovascular and Peripheral Vascular System
Peripheral Vascular System
Arterial
Arteries are responsible for transporting blood away from the heart to the rest of the body tissues. Arteries contain three concentric layers of tissue: the intima, the media, and the adventitia. The intima is the innermost layer; it is here that atherosclerotic plaque formation begins. The media comprises smooth muscle cells with elastic properties to accommodate blood pressure and flow. The adventitia is the outermost layer of the artery, consisting of connective tissue (Bickley, 2021; Thompson, 2018).
Arterial pulses are palpable throughout the body :
Venous
The heart’s pumping action propels blood out of the heart via the arterial system by moving from an area of high pressure to low pressure. Both arteries and veins have the same three distinct tissue layers: the intima, media, and adventitia. Unlike arteries, veins are thin-walled and stretchy; as a result, they can hold up to two-thirds of circulating blood flow in the human body.
Veins from the arms, upper trunk, and head and neck drain into the superior vena cava, veins from the abdominal wall, liver, lower trunk, and legs drain into the inferior vena cava. Veins of the lower extremities include deep, superficial, and perforating veins. Due to their weaker wall structure leg veins are susceptible to irregular dilatation, compression, ulceration, and invasion by tumours (Bickley, 2021, chp. 17).
The venous system returns blood to the heart and must, therefore, have a higher pressure gradient than the heart’s atria. Two factors allow venous pressure to remain higher than the pressure in the atria.
- During diastole, the pressure in the atria is very low as the atria are relaxed
- Two physiologic pumps (skeletal muscle and respiratory pumps) counteract gravity and help the lower pressured veins propel blood back to the heart with the help of skeletal muscle contraction and pressure changes in the thorax.
-
- The blood is compressed, and the pressure is increased near a vein by the contraction of the skeletal muscles. As a result, blood is pushed closer to the heart, where venous pressure is lower. When we exhale, pressure in the thorax is reduced to lower than that of the abdominal veins, causing blood to flow along its pressure gradient from veins outside the thorax into the thoracic region, where pressure is now lower, which promotes the return of blood from the thoracic veins to the atria. As the thoracic cavity’s air pressure rises during exhalation, pressure in the thoracic veins also rises, accelerating blood flow into the heart (Bickley, 2021; Thompson, 2018).
Lymphatics
The lymphatic system is a vascular network that drains lymph fluid from body tissues and returns it to venous circulation for eventual return to the heart. Different body parts drain lymphatic fluid into ducts that drain into the right and left subclavian vein