1. Venous system. Veins of systemic and pulmonary circulation

2. BLOOD VESSELS

3. Major Systemic Veins

4. 4

5. Major Systemic Veins
Superior Vena Cava
Inferior Vena Cava

8. Major Systemic Veins Lower Limb Dorsal venous arch Dorsalis pedis vein
Great saphenous vein
Dorsalis pedis vein ↓
Anterior tibial vein
Popliteal vein
Femoral vein
External iliac vein
Common iliac vein
Inferior vena cava
Small saphenous vein
Plantar Arch ↓
plantar veins
Posterior tibial vein
Fibular
(peroneal) vein

9. BLOOD VESSELS
Arterioles
Veinules

10. COMPARISON OF ARTERIES, CAPILLARIES, & VEINS
Arteries & Arterioles
Capillaries
Veinules & Veins
Tunica Media
Tunica Intima
*Arteries carry blood to smaller arterioles which in turn lead to capillaries. *
Capillaries carry blood to veinules * which lead to veins which carry the blood back to the right atrium.
* The tunica adventitia or tunica externa is the outermost covering of arteries, arterioles, veinules and veins. It is primarily composed of connective tissue which protects, supports and anchors the vessels to adjacent structures. Loosely woven collagen fibers are the primary components of the tunica adventitia along with nerve fibers, lymphatic vessels and elastic fibers.
* The tunica media is the middle layer of arteries, arterioles, veinules and veins. It is primarily made up of smooth muscle cells arranged in a circular fashion around those vessels along with some elastin. The primary function of the tunica media is vasoconstriction and vasodilation to regulate blood pressure and maintain the continuous circulation of blood.
* The tunica intima or tunica interna is primarily made of simple squamous epithelial cells which line the lumen of all blood vessels. It provides a smooth surface to reduce friction. Since capillaries lack the tunica media and tunica adventitia, they are much more permeable than other blood vessels. Thus it is only through the walls of capillaries that diffusion of O2 and nutrients from the blood * into the cells and tissues as well as the diffusion of wastes from the cells and tissues into the blood occurs. *
(Blood)
Tunica Adventitia

11. CAPILLARY BEDS
Sphincters regulate the flow of blood into capillaries thus affecting the perfusion of capillaries & the amount of diffusion which occurs between the blood and the tissues.*

12. BLOOD PRESSURE

13. VENOUS PUMP

14. VENOUS PUMP
1. Valves - formed from folds of tunica intima prevent backflow of blood in veinules & veins.
2. Function like semilunar valves forcing blood to flow against gravity toward the heart.
Blood pressure is highest in the arteries and drops off gradually as the blood flows through the circulatory system. By the time the blood has passed through the capillaries, the pressure has decreases to 20 mm Hg or less and continues to drop. This low pressure is insufficient to allow the blood to move against gravity to return to the heart. The venous pump in veinules and veins makes up for the lack of pressure.
* The valves forming the venous pump are formed from folds in the tunica intima. * They act as one-way valves, only allowing the blood to move toward the heart. * The force to move the blood from valve to valve toward the heart is provided by skeletal muscles which press against the walls of veinules and veins as they contract forcing the blood through the next valve toward the heart. * When skeletal muscles relax, the distal valves close to prevent blood flow away from the heart. *

15. VENOUS PUMP
3. Skeletal muscles pressing against walls of veins provide force to move blood from one valve through the next toward the heart.
4. Skeletal muscles pressing against walls of veins provide force to move blood from one valve through the next toward the heart.

16. VARICOSE VEINS
1. Veins that are stretched, dilated & overfilled with blood due to incompetent valves
2. Contributing causes:
Weak valves or veins - (heredity)
Excessive weight
Excessive standing, straining
Inadequate exercise
Increased intra-pelvic pressure - pregnancy, constipation
Varicose veins * have been stretched, dilated or overfilled to the extent that the valves of the venous pump are not able to close properly to prevent the backflow of blood. Thus blood pools in the extremities further aggravating the situation. * Things that may contribute to the formation of varicose veins include:
* weak valves or veins due to heredity,
* excessive weight,
* standing for long periods of time with little movement and straining,
* inadequate exercise,
* increased intra-pelvic pressure due to pregnancy, constipation, etc. *

17. VARICOSE VEINS
* The pictures show how varicose veins may appear. * They tend to occur most frequently in superficial veins where skeletal muscles do not completely surround the veins being affected. Because of the stagnation of blood in varicose veins, there is an increased risk of blood clot formation with the attendant risk of emboli. *

18. Major Systemic Veins Lower Limb Dorsal venous arch Great saphenous
Femoral
External iliac
Common iliac
Inferior vena cava
Dorsal venous arch
Great saphenous
Small saphenous
Dorsalis pedis
Anterior tibial
Popliteal
Femoral
External iliac
Common iliac
Inferior vena cava
Plantar arch
Plantar veins
Posterior tibial
Fibular
Anterior tibial
Popliteal
Femoral
External iliac
Common iliac
Inferior vena cava
Dorsal venous arch
Small saphenous
Popliteal
Femoral
External iliac
Common iliac
Inferior vena cava

20. Major Systemic Veins Abdomen I N F E R I O R V E N A C A V A
Hepatic veins
Hepatic veins
Left suprarenal vein
Right suprarenal vein
Renal vein
Left gonadal vein
Right gonadal vein
Lumbar veins
Lumbar veins

22. Major Systemic Veins Head and Neck Brachiocephalic vein
Occipital vein ↓
Posterior arcuate vein
External jugular vein
Vertebral
Facial
Superficial temporal vein
Subclavian vein
Brachiocephalic vein
Superior vena cava
Internal jugular vein

24. Major Systemic Veins Head and Neck Occipital vein
Posterior arcuate vein
External jugular vein
Subclavian vein
Brachiocephalic vein
Superior vena cava
Facial vein
Superficial temporal vein
Internal jugular vein
Brachiocephalic vein
Superior vena cava
Vertebral vein
Subclavian vein
Brachiocephalic vein
Superior vena cava

25. Major Systemic Veins Upper Limb Axillary ↓ Subclavian Brachiocephalic
Median antibrachial vein
Ulnar vein Radial vein
Basilic vein
Brachial vein
Cephalic
Axillary ↓
Subclavian
Brachiocephalic
Superior vena cava
Median cubital vein

26. Major Systemic Veins Upper Limb Ulnar vein Basilic vein Radial vein
Brachial vein
Axillary vein
Subclavian vein
Brachiocephalic vein
Superior vena cava
Basilic vein
Brachial vein
Axillary vein
Subclavian vein
Brachiocephalic vein
Superior vena cava
Cephalic vein
Axillary vein
Subclavian vein
Brachiocephalic vein
Superior vena cava

27. Posterior intercostal veins
Major Systemic Veins
Thorax
Azygos System
Posterior intercostal veins ↓
Ascending lumbar vein
Accessory hemiazygos veins
Hemiazygos vein
Azygos vein
Superior vena cava

28. Major Systemic Veins Thorax Azygos System Posterior intercostal veins
Ascending lumbar vein
Accessory hemiazygos veins
Azygos vein
Superior vena cava
Posterior intercostal veins
Ascending lumbar veins
Hemiazygos vein
Azygos vein
Superior vena cava

29. Major Systemic Veins Hepatic Portal System Veins from
Veins from distal large intestine ↓
Inferior mesenteric vein
Veins from spleen ↓
Splenic vein
Veins from small intestine,
ascending and transverse
colon ↓
Superior mesenteric vein
Veins from
digestive viscera, spleen, & pancreas ↓
Hepatic Portal vein
Liver
Hepatic veins
Inferior vena cava
Veins from
lesser curvature
of stomach ↓
Left gastric vein

30. Major Systemic Veins Hepatic Portal System
Veins from distal large intestine
Inferior mesenteric vein
Veins from digestive viscera, spleen and pancreas
Hepatic portal vein
Liver
Hepatic veins
Inferior vena cava
Veins from small intestine, ascending and transverse colon
Superior mesenteric vein
Veins from digestive viscera, spleen and pancreas
Hepatic portal vein
Liver
Hepatic veins
Inferior vena cava
Veins from spleen
Splenic vein
Veins from digestive viscera, spleen and pancreas
Hepatic portal vein
Liver
Hepatic veins
Inferior vena cava
Veins from lesser curvature of stomach
Left gastric vein
Liver
Hepatic veins
Inferior vena cava

31. Major Systemic Veins
Hepatic Portal System