Cardiovascular System Blood Vessels

Anatomy of Blood Vessels Arteries carry blood from the heart to the tissues Arteries carry blood from the heart to the tissues

Anatomy of Blood Vessels Arterioles are small arteries that connect to capillaries Arterioles are small arteries that connect to capillaries

Anatomy of Blood Vessels Capillaries are the site of substance exchange between the blood and body tissues Capillaries are the site of substance exchange between the blood and body tissues

Anatomy of Blood Vessels Venules connect capillaries to larger veins Venules connect capillaries to larger veins

Anatomy of Blood Vessels Veins convey blood from the tissues back to the heart. Veins convey blood from the tissues back to the heart.

Arteries 1. Tunica interna (intima) – innermost 2. Tunica media – middle layer 3. Tunica externa – outer layer

Tunica Intima Composed of; Composed of; 1. simple squamous epithelium (endothelium) 2. Internal elastic membrane

Tunica Media Rich in smooth muscle and elastic fibers Rich in smooth muscle and elastic fibers

Tunica Media Maintains elasticity and contractility Maintains elasticity and contractility

Tunica Externa Rich in elastic and collagen fibers Rich in elastic and collagen fibers

Functional Properties of Arteries 1. Elasticity 2. Contractility

Elasticity Due to the elastic tissue in the tunica intima and media Due to the elastic tissue in the tunica intima and media

Elasticity Allows arteries to accept blood under great pressure from the contraction of the ventricles Allows arteries to accept blood under great pressure from the contraction of the ventricles

Contractility Due to the smooth muscle in the tunica media Due to the smooth muscle in the tunica media

Contractility Allows arteries to increase or decrease lumen size Allows arteries to increase or decrease lumen size

Contractility Sympathetic stimulation of alpha 1 receptors on cutaneous arteries causes vasoconstriction Sympathetic stimulation of alpha 1 receptors on cutaneous arteries causes vasoconstriction

Contractility Sympathetic stimulation of beta 2 receptors on arteries supplying skeletal muscle causes vasodilation Sympathetic stimulation of beta 2 receptors on arteries supplying skeletal muscle causes vasodilation

Elastic Arteries Elastic Arteries – Large arteries with more elastic fibers and less smooth muscle Elastic Arteries – Large arteries with more elastic fibers and less smooth muscle

Elastic Arteries Example: aorta, sublcavian, and pulmonary arteries Example: aorta, sublcavian, and pulmonary arteries

Elastic Arteries Also called conducting arteries because they conduct blood from the heart to medium sized arteries Also called conducting arteries because they conduct blood from the heart to medium sized arteries

Muscular or distributing arteries Medium sized and have a large amount of smooth muscle and distribute blood to various parts of the body Medium sized and have a large amount of smooth muscle and distribute blood to various parts of the body

Muscular or distributing arteries Examples: brachial, femoral, and popliteal arteries Examples: brachial, femoral, and popliteal arteries

Arterioles Very small arteries that deliver blood to capillaries Very small arteries that deliver blood to capillaries

Capillaries Connect arterioles and venules Connect arterioles and venules

Capillaries Microcirculation – flow of blood through the capillaries Microcirculation – flow of blood through the capillaries

Capillaries Capillaries are found near almost every cell in the body Capillaries are found near almost every cell in the body

Capillaries Function – Permit the exchange of nutrients and wastes between the blood and tissue cells Function – Permit the exchange of nutrients and wastes between the blood and tissue cells

Capillaries Composed of a single layer of cells (endothelium) and a basement membrane Composed of a single layer of cells (endothelium) and a basement membrane

Capillaries Two types; Two types; 1. Continuous 2. Fenestrated

Capillaries Continuous – composed of endothelial cells that form a continuous tube that contains gaps between cells called intercellular clefts Continuous – composed of endothelial cells that form a continuous tube that contains gaps between cells called intercellular clefts

Capillaries Fenestrated capillaries – plasma membrane contains small pores Fenestrated capillaries – plasma membrane contains small pores

Capillaries Materials can cross the blood capillary walls in four ways Materials can cross the blood capillary walls in four ways

Capillaries Four Ways; 1. Intercellular clefts 2. Trancytosis using pinocytic vesicles 3. Diffusion 4. Fenestrations

Intercellular clefts Open in response to histamine (released during inflamation) making capillaries more leaky Open in response to histamine (released during inflamation) making capillaries more leaky

Intercellular clefts This allows fluid and wbc, and antibodies to go from the bloodstream to the site of infection This allows fluid and wbc, and antibodies to go from the bloodstream to the site of infection

Pinocytosis Large fats cross via pinocytosis Large fats cross via pinocytosis

Diffusion Water, CO2, and O2 cross capillaries by diffusion Water, CO2, and O2 cross capillaries by diffusion

Fenestrations Allow small molecules such as water and electrolytes to get into the urine Allow small molecules such as water and electrolytes to get into the urine

Fenestrations Prevent large proteins and red cells from getting into the urine Prevent large proteins and red cells from getting into the urine

Sinusoids Discontinuous capillaries Discontinuous capillaries

Sinusoids Present in the liver Present in the liver

Sinusoids Allow large molecules such as protein and bilirubin to get from the bloodstream into hepatocytes Allow large molecules such as protein and bilirubin to get from the bloodstream into hepatocytes

Venules They are small vessels that are formed from the union of several capillaries They are small vessels that are formed from the union of several capillaries

Venules Merges to form veins Merges to form veins

Venules Drain blood from capillaries into veins Drain blood from capillaries into veins

Veins Contain 60% of our blood volume Contain 60% of our blood volume

Veins Consist of the same three tunics as arteries Consist of the same three tunics as arteries

Veins Have a thinner tunica intima and media Have a thinner tunica intima and media

Veins Thicker tunica externa Thicker tunica externa

Veins Thinner walled than arteries due to less elastic tissue and smooth muscle Thinner walled than arteries due to less elastic tissue and smooth muscle

Veins Low pressure systems Low pressure systems

Veins Contain valves to prevent backflow Contain valves to prevent backflow

Veins Squeezing of the veins by muscles and inspiration promote venous return Squeezing of the veins by muscles and inspiration promote venous return

Venous Return The volume of blood returning back to the heart from the systemic veins The volume of blood returning back to the heart from the systemic veins

Veins Vascular sinuses – veins with very thin walls with no smooth muscle to alter their diameter Vascular sinuses – veins with very thin walls with no smooth muscle to alter their diameter Example: Coronary sinus Example: Coronary sinus

Anastomoses Union of the branches of two or more arteries supplying the same region Union of the branches of two or more arteries supplying the same region

Anastomoses Provide alternate routes for blood to reach a tissue or organ Provide alternate routes for blood to reach a tissue or organ

Anastomoses Collateral circulation is the alternate flow of blood to a body part through an anastomosis Collateral circulation is the alternate flow of blood to a body part through an anastomosis

Anastomoses What is the importance of arteries that anastomose? What is the importance of arteries that anastomose?

Anastomoses Occlusion of an end artery interrupts the blood supply to a whole segment of an organ, producing necrosis of that segment Occlusion of an end artery interrupts the blood supply to a whole segment of an organ, producing necrosis of that segment

Blood Pressure Pressure exerted on the walls of a blood vessel Pressure exerted on the walls of a blood vessel

Blood Pressure In a clinical sense, it refers to pressure in arteries In a clinical sense, it refers to pressure in arteries

Blood Pressure BP=CO X TPR BP=CO X TPR

Blood Pressure Systolic and Diastolic fluctuations in the pressure are only seen in the arteries and arterioles Systolic and Diastolic fluctuations in the pressure are only seen in the arteries and arterioles

Systolic Pressure Peak pressure in the arteries with each cardiac cycle during ventricular contraction Peak pressure in the arteries with each cardiac cycle during ventricular contraction

Systolic Pressure Due to the stroke volume being ejected into the aorta Due to the stroke volume being ejected into the aorta

Diastolic Pressure Lowest pressure in the arteries with each cardiac cycle Lowest pressure in the arteries with each cardiac cycle

Diastolic Pressure Force of blood recorded during ventricular relaxation Force of blood recorded during ventricular relaxation

Blood Pressure Young adult male = 120/80 mm Hg (8-10 mm Hg less in a young adult female) Young adult male = 120/80 mm Hg (8-10 mm Hg less in a young adult female)

Resistance Depends on three variables; Depends on three variables; 1. Blood viscosity 2. Vessel length 3. Blood Vessel Radius

Blood Viscosity Increased viscosity increases resistance Increased viscosity increases resistance

Vessel length Increased length increases resistance Increased length increases resistance

Blood Vessel Radius Increased radius decreases resistance Increased radius decreases resistance

Systemic vascular resistance Total peripheral resistance (TPR) Total peripheral resistance (TPR)

Systemic vascular resistance All of the vascular resistance offered by systemic blood vessels All of the vascular resistance offered by systemic blood vessels

Mean Arterial Pressure MAP = Diastolic Pressure X 1/3(systolic pressure – diastolic pressure) MAP = Diastolic Pressure X 1/3(systolic pressure – diastolic pressure)

Mean Arterial Pressure MAP = CO X TPR MAP = CO X TPR

Mean Arterial Pressure Factors that increase BP Factors that increase BP increase SV increase SV increase HR increase HR constrict the blood vessels (increases resistance) constrict the blood vessels (increases resistance)

Mean Arterial Pressure Factors that decrease BP Factors that decrease BP Decrease CO Decrease CO Dilate the arteries Dilate the arteries

Cardiovascular Center A group of neurons in the medulla that regulate heart rate, contractility, and blood vessel diameter A group of neurons in the medulla that regulate heart rate, contractility, and blood vessel diameter

Cardiovascular Center CV receives input from higher brain regions and sensory receptors (baroreceptors and chemoreceptors) CV receives input from higher brain regions and sensory receptors (baroreceptors and chemoreceptors)

Cardiovascular Center Sympathetic impulses along cardioaccelerator nerves increase heart rate and contractility Sympathetic impulses along cardioaccelerator nerves increase heart rate and contractility

Cardiovascular Center Parasympathetic impulse along vagus nerves decrease heart rate Parasympathetic impulse along vagus nerves decrease heart rate

Cardiovascular Center The sympathetic division also continually sends impulses to smooth muscle in blood vessel walls via vasomoter nerves resulting in a moderate state of tonic vasoconstriction The sympathetic division also continually sends impulses to smooth muscle in blood vessel walls via vasomoter nerves resulting in a moderate state of tonic vasoconstriction

Neural Regulation of Blood Pressure Baroreceptors Baroreceptors Chemoreceptors Chemoreceptors

Baroreceptors Pressure-sensitive sensory neurons that monitor stretching of the walls of blood vessels Pressure-sensitive sensory neurons that monitor stretching of the walls of blood vessels

Baroreceptors If blood pressure falls, the baroreceptor reflexes; If blood pressure falls, the baroreceptor reflexes; accelerate heart rate accelerate heart rate increase force of contraction increase force of contraction promote vasoconstriction promote vasoconstriction

Baroreceptors If pressure increases above normal, the reflexes cause; If pressure increases above normal, the reflexes cause; decrease in sympathetic tone decrease in sympathetic tone increase in parasympathetic tone increase in parasympathetic tone

Hormonal Regulation Renin leads to the formation of angiotensin II Renin leads to the formation of angiotensin II

Hormonal Regulation Angiotensin II causes; Angiotensin II causes; 1. Vasoconstriction 2. Secretion of aldosterone, which leads to sodium and water retention

Hormonal Regulation Epinephrine and norepinephrine increase CO and cause vasoconstriction Epinephrine and norepinephrine increase CO and cause vasoconstriction

Hormonal Regulation ADH causes water retention and a little vasoconstriction ADH causes water retention and a little vasoconstriction

Hormonal Regulation Nitric oxide from the endothelial cells causes vasodilation Nitric oxide from the endothelial cells causes vasodilation

Hormonal Regulation Cortisol keep our arteries sensitive to vasoconstricting hormones Cortisol keep our arteries sensitive to vasoconstricting hormones

Shock Is an inadequate CO that results in failure of the CV system to deliver adequate amounts of O2 and nutrients to meet the metabolic needs of body cells Is an inadequate CO that results in failure of the CV system to deliver adequate amounts of O2 and nutrients to meet the metabolic needs of body cells

Shock Could result in; dysfunction of cellular membranes dysfunction of cellular membranes abnormal cellular metabolism abnormal cellular metabolism cellular death cellular death

Types of Shock 5 main types 5 main types

Hypovolemic Shock Due to decreased blood volume Due to decreased blood volume

Cardiogenic Shock Due to poor heart function Due to poor heart function

Vascular Shock Due to inappropriate vasodilation Due to inappropriate vasodilation

Obstructive Shock Due to obstruction of blood flow Due to obstruction of blood flow

Neurogenic shock Due to decreased sympathetic outflow Due to decreased sympathetic outflow

Homeostatic Response Activation of renin-angiotensin- aldosterone system Activation of renin-angiotensin- aldosterone system

Homeostatic Response Secretion of ADH Secretion of ADH

Homeostatic Response Activation of the sympathetic division of the ANS Activation of the sympathetic division of the ANS

Circulatory Routes Systemic Systemic Pulmonary Pulmonary Hepatic Portal Hepatic Portal Fetal Fetal

Hepatic Portal Circulation Collects blood from the veins of the pancreas, spleen, stomach, intestines and gallbladder and directs it into the hepatic portal vein of the liver before it returns to the heart Collects blood from the veins of the pancreas, spleen, stomach, intestines and gallbladder and directs it into the hepatic portal vein of the liver before it returns to the heart

Hepatic Portal Circulation Enables nutrient utilization and blood detoxification by the liver Enables nutrient utilization and blood detoxification by the liver