2 Special Circulations Pulmonary Circulation Right ventricle ↓ Pulmonary trunkRight and left pulmonary arteriesLobar arteries (2 left, 3 right)ArteriolesPulmonary capillariesDiffusionVenulesVeinsPulmonary veinsLeft atriumDoes not serve metabolic needs, permits gas exchange with alveoli only.Arteries are structurally like veins – low pressure.Systemic pressure = 120/80 ; pulmonary pressure = 24/8Functional blood supply for the lungs comes from the aorta and through the bronchial arteries.
3 Internal iliac arteries Special CirculationsFetal CirculationPlacenta↓Umbilical veinDuctus venosusInferior vena cavaRight atriumForamen ovaleLeft atriumLeft ventricleAortaBodyInternal iliac arteriesUmbilical arteriesLiverRight ventricle↓Pulmonary trunkDuctus arteriosusLower extremitiesUmbilical cord is made of the umbilical vein and two umbilical arteries. Vein carries nutrients and O2 to fetus. Arteries carry CO2 and wastes from fetus to placenta.
10 COMPARISON OF ARTERIES, CAPILLARIES, & VEINS Arteries & ArteriolesCapillariesVeinules & VeinsTunica MediaTunica 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 BEDSSphincters 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.*
14 VENOUS PUMP1. 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 PUMP3. 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 VEINS1. Veins that are stretched, dilated & overfilled with blood due to incompetent valves2. Contributing causes:Weak valves or veins - (heredity)Excessive weightExcessive standing, strainingInadequate exerciseIncreased intra-pelvic pressure - pregnancy, constipationVaricose 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 ARTERIES OF THE BODY One of the objectives for this unit requires you to identify from diagrams the major arteries and veins of the body. The specific arteries and veins which you will be required to identify are indicated in the objective. Each required artery will be indicated in these notes in bold print. We will review the arteries first.*
19 Brachiocephalic Aortic Arch Ascending Aorta Thoracic Aorta Abdominal AortaThe ascending aorta * is the specific name given to the aorta as it arises from the left ventricle. * It arches to the left forming the aortic arch from which several arteries branch off carrying blood to upper areas of the body . * The first artery that branches off of the aortic arch is called the brachiocephalic artery. * When the aortic arch turns downward behind the heart in the thoracic cavity, it may be referred to as the thoracic aorta. * Once it passes through the diaphragm, it may be referred to specifically as the abdominal aorta. It is common for the ascending aorta, aortic arch, thoracic aorta and the abdominal aorta to simply be referred to in a generic sense as the aorta. *
20 CeliacThe celiac artery (trunk) * is the first major artery to branch off of the abdominal aorta after passing through the diaphragm. The celiac trunk is very short and divides into arteries which carry blood to the liver (hepatic), the spleen (splenic) and to the stomach (gastric). *
21 This diagram shows some of the major arteries which branch off of the abdominal aorta. * As indicated previously, the celiac trunk is the first artery to branch off after the aorta passes through the diaphragm into the abdominal cavity. * The superior mesenteric artery is the second artery to branch off of the aorta. It carries blood to the upper colon and small intestines by running through the mesenteries. * The right and left renal arteries carry blood to each kidney from the aorta. * The inferior mesenteric artery branches off of the aorta to carry blood through the mesenteries to the lower parts of the colon and the small intestine. * Finally, the aorta ends as it divides into a right and a left common iliac artery. *
22 ARTERIES OF THE LEG External Iliac Internal Iliac Femoral Popliteal (behind knee)Anytime the term “common” is used as the name of an artery, you can anticipate that it will divide into an internal artery and an external artery with the same name. In this case, the common iliac artery on each side will divide into an external iliac artery * which carries blood into the leg and an internal iliac artery * which carries blood to the pelvic viscera and gluteal muscles.When the external iliac artery reaches the femur, its name changes to become the femoral artery. * The femoral artery runs along the medial side of the femur until it reaches the end of the femur and runs behind the knee. As it runs behind the knee, it is called the popliteal artery. * When the popliteal artery reaches the tibia, it divides. One branch runs along the posterior surface of the tibia. It is called the posterior tibial artery. * The branch which runs along the anterior surface of the tibia is called the anterior tibial artery. * *Anterior TibialPosterior Tibial (behind Tibia)
23 ARTERIES OF THE HEAD & NECK It was noted earlier that the branchiocephalic artery * was the first artery to branch off of the aortic arch. It quickly divides into a right subclavian artery * which carries blood under the clavicle into the right arm, and a right common carotid artery * which carries blood through the neck toward the head. As the right common carotid artery nears the head, it branches into the right external carotid artery * which carries blood to the superficial areas of the head, and a right internal carotid artery * which carries blood to the brain via the circle of Willis. A corresponding left common carotid artery, internal and external carotid arteries supply blood to the left side of the head and brain.An artery which branches off of the right subclavian artery and runs through the right transverse foramina of the cervical vertebrae toward the cranium is the right vertebral artery. * A corresponding left vertebral artery branches off of the left subclavian artery on the left side. The two vertebral arteries join inside the cranium to form a single artery, the basilar artery * which also supplies blood to the brain via the circle of Willis. *
34 Major Systemic Veins Hepatic Portal System Veins from Veins from distal large intestine↓Inferior mesenteric veinVeins from spleen↓Splenic veinVeins from small intestine,ascending and transversecolon↓Superior mesenteric veinVeins fromdigestive viscera, spleen, & pancreas↓Hepatic Portal veinLiverHepatic veinsInferior vena cavaVeins fromlesser curvatureof stomach↓Left gastric vein
35 Major Systemic Veins Hepatic Portal System Veins from distal large intestineInferior mesenteric veinVeins from digestive viscera, spleen and pancreasHepatic portal veinLiverHepatic veinsInferior vena cavaVeins from small intestine, ascending and transverse colonSuperior mesenteric veinVeins from digestive viscera, spleen and pancreasHepatic portal veinLiverHepatic veinsInferior vena cavaVeins from spleenSplenic veinVeins from digestive viscera, spleen and pancreasHepatic portal veinLiverHepatic veinsInferior vena cavaVeins from lesser curvature of stomachLeft gastric veinLiverHepatic veinsInferior vena cava
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