BLOOD SUPPLY AND NERVE SUPPLY OF VEINS
The larger veins , like arteries are supplied with nutrient vessels called Vasa vasorum. But in veins , the vessels may penetrate up to the intima, probably because of the low venous pressure and the low oxygen tension. Nerves are also distributed to the veins in the same manner as to the arteries, but are fewer in number.
Factors promoting venous return
1. Skeletal Muscle Pump
A major mechanism promoting venous return during normal locomotory activity (e.g., walking, running) is the muscle pump system.
2. Respiratory Activity(Abdominothoracic or Respiratory Pump) Respiratory activity influences venous return to the heart. Briefly, increasing the rate and depth of respiration promotes venous return and therefore enhances cardiac output.
3. Muscle contraction. : Rhythmical contraction of limb muscles occurs during normal locomotory activity (walking, running, swimming) promotes venous return by the muscle
pump mechanism. Muscle contractions becomes more effective within light sleeve of deep fascia in the lower limbs.
Thus calf muscles (soleus) are known as peripheral heart thus the muscle pumps are important factors in venous return.
4.Gravity: helps venous return in the upper part of body.
5.Vena cava compression. An increase in the resistance of the vena cava, occurs when the thoracic vena cava becomes compressed during a Valsalva maneuver or during late pregnancy thus decreases venous return
CAPILLARIES Capillaries are the smallest blood vessels. They serve to distribute oxygenated blood from arteries to the tissues of the body and to feed deoxygenated blood from the tissues back into the veins Capillus + hair are network of microscopic endothelial tubes Interposed between arterioles and venules
These are fine branching blood vessels that form a network between the arterioles and venules
Size of capillaries Capillaries are too small that red blood cells can only travel through them in single file. Capillaries measure in size from about 5-10 microns in diameter. The aCapillary walls are thin and are composed of - Single layer of endothelial cells - Basal lamina of glycoprotien -Capillary layer of connective tissue cells and fibres.
PHYSIOLOGY OF PERIPHERAL VASCULAR SYSTEM
• Blood vessels do not actively engaged in the transport of blood but arteries and veins to a degree can regulate their inner diameter by contraction of the muscular layer. • blood flow to downstream organs and is determined by the autonomic nervous system. Vasodilation and vasoconstriction are also used antagonistically as methods of thermoregulation. • Oxygen( bound to hemoglobin in red blood cells) is the most critical nutrient carried by the blood in all arteries apart from the pulmonary artery, hemoglobin is highly saturated (95-100% ) with oxygen . In all veins apart from the pulmonary vein, the hemoglobin is desaturated at about 74%.
• The blood pressurein blood vessel is traditionally expressed in millimeters of Mercury ( 1mmhg – 133 PA ). In the arterial system , this is usually around 120mmhg systolic and 80mmhg diastolic in contrast pressure in the Venus system are constant and rarely exceed 10 mm hg. • Vasoconstriction is the constriction of blood vessels by contracting the vascular smooth muscle in the vessel wall. It is regulated by vasoconstrictors these includes paracrine factors e.g prostaglandins, a numbers of hormones (e.g vasopressin and angiotensin) and neurotransmitters (e.g epinephrine) from the nervous system. • Vasodilation is a similar process mediated by antagonistically acting mediators . The most prominent vasodilator is nitric oxide. • Permeability of the endothelium is pivotal in the release of nutrients to the tissue. It is also increased in inflammation in response to histamine, prostaglandins and interleukins which leads to most of the symptoms of inflammation (swelling , redness and warmth).
THE ARTERIAL SYSTEM
Arteries are elastic, muscular, tubular extensions of heart that carry O2 reach blood at high pressures to all parts of the body. Pressures may vary according to the type of organ supplied and distance from the heart. The distal vessel tends to be more muscular to propel the blood to outermost regions of the body. Because of contractile nature of the vessels, the arterial system operates without assistance of valves. The artery branch off into arterial which further divide into capillaries.
THE VENOUS SYSTEM
The veins which receive deoxygenated blood are structured similarly to the arteries. Because of inability to contract , vein relies on a system of valves that assist the return of blood to the heart. The valves are formed from tunica intima layer and are designed to allow only one way flow of blood. The valves of venous system are more common in lower limbs where the forces of gravity are greatest The venous system has divisions that are unique to the lower extremity. They are classified as
1) superficial veins
2) Perforating veins
3) Deep veins.
THE LYMPHATIC SYSTEM It includes extensive network of capillaries, collecting vessels, lymph node and lymph organs such as tonsils, spleen, and thymus. The lymphatics also serve as an immunological system of peripheral antigens and circulating leucocytes.
SCREENING
Screenings should be performed on individuals who complain of leg pain and have diminished pulses in their legs, all smokers as part of their regular physical exam, any male over the age of 65 who has a history of smoking and anyone who has a family history of PVD.
Screenings for PVD can be performed in the office by doing an ankle brachial index (ABI ) test which uses blood pressure cuff to measure blood flow in the legs. Sometimes pateint may be asked to walk on a treadmill until they begin to have leg pain, and then the ABI is re-measured. If the ABI is abnormal an ultrasound of the arteries may be performed to help determine the location and extent of blockage.
CLASSIFICATION
1. ARTERIAL DISEASE
2. VENOUS DISEASE
Atherosclerosis. -DVT -Burgers disease -Varicose veins -Raynaud’s disease. -CVI
ATHEROSCLEROSIS
It is also known as atherosclerotic cardiovascular disease. It is the most common occlusive arterial disease. It is a disease of the arteries characterized by the deposition of fatty material on their inner walls.
Atherosclerosis is a condition where the arteries become narrowed and hardened due to a buildup of plaque around the artery wall. These plaques are made up of cholesterol, fatty substance, cellular waste products , fibrin and calcium.
Factors promoting venous return
1. Skeletal Muscle Pump
A major mechanism promoting venous return during normal locomotory activity (e.g., walking, running) is the muscle pump system.
2. Respiratory Activity(Abdominothoracic or Respiratory Pump) Respiratory activity influences venous return to the heart. Briefly, increasing the rate and depth of respiration promotes venous return and therefore enhances cardiac output.
3. Muscle contraction. : Rhythmical contraction of limb muscles occurs during normal locomotory activity (walking, running, swimming) promotes venous return by the muscle
pump mechanism. Muscle contractions becomes more effective within light sleeve of deep fascia in the lower limbs.
Thus calf muscles (soleus) are known as peripheral heart thus the muscle pumps are important factors in venous return.
4.Gravity: helps venous return in the upper part of body.
5.Vena cava compression. An increase in the resistance of the vena cava, occurs when the thoracic vena cava becomes compressed during a Valsalva maneuver or during late pregnancy thus decreases venous return
CAPILLARIES Capillaries are the smallest blood vessels. They serve to distribute oxygenated blood from arteries to the tissues of the body and to feed deoxygenated blood from the tissues back into the veins Capillus + hair are network of microscopic endothelial tubes Interposed between arterioles and venules
These are fine branching blood vessels that form a network between the arterioles and venules
Size of capillaries Capillaries are too small that red blood cells can only travel through them in single file. Capillaries measure in size from about 5-10 microns in diameter. The aCapillary walls are thin and are composed of - Single layer of endothelial cells - Basal lamina of glycoprotien -Capillary layer of connective tissue cells and fibres.
PHYSIOLOGY OF PERIPHERAL VASCULAR SYSTEM
• Blood vessels do not actively engaged in the transport of blood but arteries and veins to a degree can regulate their inner diameter by contraction of the muscular layer. • blood flow to downstream organs and is determined by the autonomic nervous system. Vasodilation and vasoconstriction are also used antagonistically as methods of thermoregulation. • Oxygen( bound to hemoglobin in red blood cells) is the most critical nutrient carried by the blood in all arteries apart from the pulmonary artery, hemoglobin is highly saturated (95-100% ) with oxygen . In all veins apart from the pulmonary vein, the hemoglobin is desaturated at about 74%.
• The blood pressurein blood vessel is traditionally expressed in millimeters of Mercury ( 1mmhg – 133 PA ). In the arterial system , this is usually around 120mmhg systolic and 80mmhg diastolic in contrast pressure in the Venus system are constant and rarely exceed 10 mm hg. • Vasoconstriction is the constriction of blood vessels by contracting the vascular smooth muscle in the vessel wall. It is regulated by vasoconstrictors these includes paracrine factors e.g prostaglandins, a numbers of hormones (e.g vasopressin and angiotensin) and neurotransmitters (e.g epinephrine) from the nervous system. • Vasodilation is a similar process mediated by antagonistically acting mediators . The most prominent vasodilator is nitric oxide. • Permeability of the endothelium is pivotal in the release of nutrients to the tissue. It is also increased in inflammation in response to histamine, prostaglandins and interleukins which leads to most of the symptoms of inflammation (swelling , redness and warmth).
THE ARTERIAL SYSTEM
Arteries are elastic, muscular, tubular extensions of heart that carry O2 reach blood at high pressures to all parts of the body. Pressures may vary according to the type of organ supplied and distance from the heart. The distal vessel tends to be more muscular to propel the blood to outermost regions of the body. Because of contractile nature of the vessels, the arterial system operates without assistance of valves. The artery branch off into arterial which further divide into capillaries.
THE VENOUS SYSTEM
The veins which receive deoxygenated blood are structured similarly to the arteries. Because of inability to contract , vein relies on a system of valves that assist the return of blood to the heart. The valves are formed from tunica intima layer and are designed to allow only one way flow of blood. The valves of venous system are more common in lower limbs where the forces of gravity are greatest The venous system has divisions that are unique to the lower extremity. They are classified as
1) superficial veins
2) Perforating veins
3) Deep veins.
THE LYMPHATIC SYSTEM It includes extensive network of capillaries, collecting vessels, lymph node and lymph organs such as tonsils, spleen, and thymus. The lymphatics also serve as an immunological system of peripheral antigens and circulating leucocytes.
SCREENING
Screenings should be performed on individuals who complain of leg pain and have diminished pulses in their legs, all smokers as part of their regular physical exam, any male over the age of 65 who has a history of smoking and anyone who has a family history of PVD.
Screenings for PVD can be performed in the office by doing an ankle brachial index (ABI ) test which uses blood pressure cuff to measure blood flow in the legs. Sometimes pateint may be asked to walk on a treadmill until they begin to have leg pain, and then the ABI is re-measured. If the ABI is abnormal an ultrasound of the arteries may be performed to help determine the location and extent of blockage.
CLASSIFICATION
1. ARTERIAL DISEASE
2. VENOUS DISEASE
Atherosclerosis. -DVT -Burgers disease -Varicose veins -Raynaud’s disease. -CVI
ATHEROSCLEROSIS
It is also known as atherosclerotic cardiovascular disease. It is the most common occlusive arterial disease. It is a disease of the arteries characterized by the deposition of fatty material on their inner walls.
Atherosclerosis is a condition where the arteries become narrowed and hardened due to a buildup of plaque around the artery wall. These plaques are made up of cholesterol, fatty substance, cellular waste products , fibrin and calcium.
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