1. ARTERIES carry blood away from the heart towards other parts of the human body. Blood is pumped from the heartās ventricles into large arteries that branch into smaller arteries until the branching results in arterioles.
The arterial wall consists of 3 layers.
A. TUNICA INTIMA: The innermost layer is simple squamous epithelium surrounded by a connective tissue basement membrane with elastic fibers.
B. TUNICA MEDIA: The middle layer is mostly smooth muscle and is most often the thickest layer. It provides support and changes vessel diameter to regulate blood flow and pressure.
C. TUNICA ADVENTITIA: The outermost layer attaches the vessel to the surrounding tissue. This layer is connective tissue with elastic and collagenous fibers.
2. VEINS carry blood toward the heart. After blood passes through the capillaries, it enters the venules. From the venules, it flows into larger veins until it reaches the heart. The veinās wall has the same 3 layers as the arteries. However, there is less smooth muscle and connective tissue. This makes the walls of veins thinner and capable of holding more blood.
3. VENA CAVA: It is the largest vein that carries blood to the heart from other areas of the body. The vena cava has 2 parts: the superior and the inferior vena cava. The superior vena cava carries blood from the head, neck, arms, and chest. The inferior vena cava carries blood from the legs, feet, and organs in the abdomen and pelvis
In large veins such as the vena cava, the tunica adventitia may be the thickest layer.
1. ARTERIES carry blood away from the heart towards other parts of the human body. Blood is pumped from the heartās ventricles into large arteries that branch into smaller arteries until the branching results in arterioles.
The arterial wall consists of 3 layers.
A. TUNICA INTIMA: The innermost layer is simple squamous epithelium surrounded by a connective tissue basement membrane with elastic fibers.
B. TUNICA MEDIA: The middle layer is mostly smooth muscle and is most often the thickest layer. It provides support and changes vessel diameter to regulate blood flow and pressure.
C. TUNICA ADVENTITIA: The outermost layer attaches the vessel to the surrounding tissue. This layer is connective tissue with elastic and collagenous fibers.
2. VEINS carry blood toward the heart. After blood passes through the capillaries, it enters the venules. From the venules, it flows into larger veins until it reaches the heart. The veinās wall has the same 3 layers as the arteries. However, there is less smooth muscle and connective tissue. This makes the walls of veins thinner and capable of holding more blood.
3. VENA CAVA: It is the largest vein that carries blood to the heart from other areas of the body. The vena cava has 2 parts: the superior and the inferior vena cava. The superior vena cava carries blood from the head, neck, arms, and chest. The inferior vena cava carries blood from the legs, feet, and organs in the abdomen and pelvis
In large veins such as the vena cava, the tunica adventitia may be the thickest layer.
Sources of information:
https://training.seer.cancer.gov/anatomy/cardiovascular/blood/classification.html
https://www.cancer.gov/publications/dictionaries/cancer-terms/def/vena-cava
https://www.teleflex.com/en/usa/arrowUniversity/vascular/cvc/section2/2.html