Blood Vessels

Types of Blood Vessels Arteries - vessels that transport blood away from the heart Veins - return blood back to the heart Capillaries - microscopic blood vessels that allow exchanges between blood and tissues

Structure of a blood vessel Tunica externa (adventitia) - outermost layer made of loose connective tissue. Serves to anchor, protect and prevent overstretching Tunica media - middle layer composed of smooth muscle; functions in dilation and constriction of blood vessels Tunica interna(intima) - innermost layer made of endothelium (s.squamous epithelium)

Blood flow through tissues From the heart blood flows into Aorta Arteries Arterioles Capillaries Venules Veins Superior/ Inferior Vena Cava Back to the heart

Arteries Elastic (conducting) arteries Larger arteries Muscular ( distributing) arteries Medium arterties Arterioles Tiny , tiny arteries Metarteriole

Capillaries Microscopic vessels that connect arterioles and venules Walls consist of a single layer of simple squamous epithelial cells that allow the exchange of gases Precapillary sphincters regulate blood flow Continuous/Fenestrated capillaries

Veins Venules merge to form veins Have 3 distinct layers; thinner walled than arteries due to thin tunica interna and media Large lumens and posses valves Varicose veins Blood reservoir

Systemic Circulation The aorta and its major branches Arterial supply to neck and head Arterial supply to upper extremities Arterial supply to thorax Arterial supply to abdomen Arterial supply to pelvic region and lower extremities

Systemic Veins Venous drainage of the head and neck Major tributaries of the inferior vena cava Venous drainage of the upper extremities Venous drainage of the lower extremities

Hepatic Portal System Routes blood from the stomach, spleen, pancreas, small and large intestines to the liver Blood from these structures all drain into the hepatic portal vein, then into the liver Blood is returned to the inferior vena cava via the hepatic vein

Fetal Circulation Placenta - site where exchange of materials between fetus and mother occur Umbilical arteries (2) - carry fetal blood high in CO2 / low in O2 to the placenta Umbilical vein - returns oxygenated blood from the placenta to the fetus

Fetal Circulation Ductus venosus - allows blood to bypass the liver Foramen ovale - opening in interatrial septum allowing blood to bypass the lungs Blood flows from r.atrium ->l.atrium Ductus arteriosus - vessel connecting pulmonary artery to the aorta

A. Great Vessels 1. superior vena cava 2. inferior vena cava 3. pulmonary veins 4. pulmonary trunk (p. artery, p. aorta) 5. systemic aorta

Branches of systemic aorta 1. from ascending aorta, right and left coronary artery 2. from aortic arch, brachiocephalic artery a. right subclavian artery (1) r. axillary artery (a) r. brachial artery 1. r. ulnar artery 2. r. radial artery

Branches of systemic aorta 3. superficial and deep palmar arches (anastomoses) (b) deep brachial artery (c) posterior circumflex (2) r. vertebral artery

Branches of systemic aorta b. right common carotid artery (a) r. external carotid artery (b) r. internal carotid artery c. (cat, not human) left common carotid artery (a) l. external carotid artery (b) l. internal carotid artery

Branches of systemic aorta 3. from aortic arch (human, not cat), left common carotid artery a. l. external carotid artery b. l. internal carotid artery

Branches of systemic aorta 4. from aortic arch, left subclavian artery (cat and human) a. l. axillary artery (1) l. brachial artery (a) l. ulnar artery (b) l. radial artery (c) superficial and deep palmar arches (anastomoses)

Branches of systemic aorta (2) deep brachial artery (3) posterior circumflex b. l. vertebral artery 5. from descending thoracic aorta a. paired bronchial arteries b. paired intercostal arteries

Branches of systemic aorta 6. from abdominal aorta a. celiac trunk (1) splenic artery (2) l. gastric artery (3) hepatic artery

Branches of systemic aorta b. superior mesenteric artery c. paired renal arteries d. paired gonadal arteries e. paired lumbar arteries f. inferior mesenteric artery

Branches of systemic aorta g. right and left common iliac arteries (1) internal iliacs (2) external iliacs->femorals-> popliteal->tibial->dorsalis pedis-> plantar arches

C. Major veins A. coronary circulation: coronary sinus B. pulmonary circulation: pulmonary veins C. hepatic portal circulation: hepatic portal vein drains 1. inferior mesenteric which drains splenic vein 2. superior mesenteric vein

D. Cranial Circulation: cranial venous sinuses

E. Systemic Circulation: 1. superior vena cava drains a. azygos system b. right and left brachiocephalic veins c. internal jugular and subclavian vein d. external jugular and axillary e. cephalic vein (superficial) and brachial vein (deep) which drains radial, ulnar, median cubital and basilic veins

2. inferior vena cava drains. a. hepatic vein. b. phrenic vein. c 2. inferior vena cava drains a. hepatic vein b. phrenic vein c. paired renal veins d. paired gonadal veins

e. paired common iliac veins which drain e. paired common iliac veins which drain (1) paired internal iliac veins (2) paired external iliac veins which drain (a) femoral veins which drain 1. popliteal veins which drain a peroneal vein b anterior and posterior tibial veins (b) great saphenous veins

Capillary Exchange

Mechanisms of Exchange Diffusion - major method used to exchange substances such as O2, CO2, glucose, and amino acids Vesicular transport - endocytosis and exocytosis of lipid-insoluble molecules Bulk flow - involves filtration and reabsorption

Arteries Veins Pressures promoting filtration Blood hydrostatic pressure*** Interstitial fluid osmotic pressure Pressures promoting reabsorption Blood colloid osmotic pressure*** Interstitial fluid hydrostatic pressure

Physiology of Circulation

Important Terms Blood Flow Blood pressure Resistance

Blood Flow Blood flow - is the amount of blood flowing through a tissue in a given period of time Velocity of blood flow is inversely related to the diameter of the blood vessel Blood flows most slowly in areas of greatest width

Blood Pressure Force that the blood exerts against the walls of a blood vessels Factors affecting BP include cardiac output, blood volume, viscosity, resistance, and the elasticity of the arteries

Cardiac Output CO=Stroke volume X Heart Rate Any factor that increases SV or HR will increase blood pressure

Peripheral Resistance Resistance to blood flow due to the force of friction between vessel wall and blood Resistance affected by blood viscosity, vessel length and vessel radius

Sources affecting Resistance Blood viscosity- how thick or thin the blood is. Measured by hematocrit. Vessel length- longer the vessel, the greater the resistance, the greater the BP Vessel radius- smaller the vessel the greater the resistance

Blood Volume  Blood volume ,  Blood pressure Blood volume & blood pressure monitored by the cardiovascular center in the medulla (ANS), baroreceptors and chemoreceptors and by hormonal regulation

Hormonal Regulation of Blood Pressure Renin- angiotensin pathway Angiotensin II - powerful vasoconstrictor thus raising resistance Stimulates secretion of aldosterone from the adrenal gland promoting sodium retention ADH - antidiuretic hormone from the pituitary causing the kidneys to reabsorb more water

Hormone lowering BP ANP - atrial natriutic peptide released by atrial cells promoting the loss of salt and water in the urine , thus  blood volume and causing vasodilation which then  blood pressure PTH - parathyroid hormone causes vasodilation

Endothelin = potent vasoconstrictor responds to low blood flow NO (nitrous oxide) = powerful vasodilator; balances endothelin and dilates vessels in response to high blood flow.

Normal Blood Pressure Newborn = 90/55 mm Hg Adults = 120/80 mm Hg Old Age = 150/90 Systolic Pressure = peak pressure during systole Diastolic pressure = lowest pressure during diastole (filling of ventricles)