Cardiovascular system The Cardiovascular System n A closed

Cardiovascular system

The Cardiovascular System n. A closed system of the heart and blood vessels – The heart pumps blood – Blood vessels allow blood to circulate to all parts of the body n The function of the cardiovascular system is to deliver oxygen and nutrients and to remove carbon dioxide and other waste products

The Heart n Location – Thorax between the lungs in the inferior mediastinum n Orientation – Pointed apex directed toward left hip – Base points toward right shoulder n About the size of your fist

The Heart Figure 11. 1 a–b

The Heart Figure 11. 1 c

Superior vena cava Right Pulmonary artery Right pulmonary vein aorta Left Pulmonary artery Left pulmonary vein Left atrium Right atrium Pulmonary valve Tricuspid valve Chordae tendineae Right ventricle Inferior vena cava Bicuspid valve Aortic valve Left ventricle Interventricular septum

Sup vena cava right pulmonary artery Right pulmonary veins Aortic arch Left pulmonary artery Left pulmonary Veins (P. V) Left atrium Right atrium Inf vena cava Right ventricle Left ventricle

The Heart: Heart Wall Figure 11. 2 b

The Heart: Coverings n Pericardium—a double-walled sac – Fibrous pericardium is loose and superficial – Serous membrane is deep to the fibrous pericardium and composed of two layers – Serous fluid fills the space between the layers of pericardium

The Heart: Heart Wall n Three layers – Epicardium § Outside layer § This layer is the visceral pericardium § Connective tissue layer – Myocardium § Middle layer § Mostly cardiac muscle – Endocardium § Inner layer – Endothelium

The Heart: Heart Wall Figure 11. 2 b

The Heart: Heart Wall Figure 11. 2 c

The Heart: Chambers n Right and left side act as separate pumps n Four chambers – Atria § Receiving chambers – Right atrium – Left atrium – Ventricles § Discharging chambers – Right ventricle – Left ventricle

The Heart: Chambers Figure 11. 2 c

Differences in Right and Left Ventricles Figure 11. 4

The Heart: Septa n Interventricular septum – Separates the two ventricles n Interatrial septum – Separates the two atria

The Heart: Chambers Figure 11. 2 c

The Heart: Valves n Allow blood to flow in only one direction to prevent backflow n Four valves – Atrioventricular (AV) valves—between atria and ventricles § Bicuspid (mitral) valve (left side of heart) § Tricuspid valve (right side of heart) – Semilunar valves—between ventricle and artery § Pulmonary semilunar valve § Aortic semilunar valve

The Heart: Valves Figure 11. 2 c

The Heart: Valves n AV valves – Anchored in place by chordae tendineae (“heart strings”) – Open during heart relaxation and closed during ventricular contraction n Semilunar valves – Closed during heart relaxation but open during ventricular contraction n Notice these valves operate opposite of one another to force a one-way path of blood through the heart

Operation of the AV valves Blood returning to the atria, puts pressure against AV valves; the AV valves are forced open AV valves open Ventricles (a) Figure 11. 5 a, step 1

Operation of the AV valves Blood returning to the atria, puts pressure against AV valves; the AV valves are forced open As the ventricles fill, AV valve flaps hang limply into ventricles AV valves open Ventricles (a) Figure 11. 5 a, step 2

Operation of the AV valves Blood returning to the atria, puts pressure against AV valves; the AV valves are forced open As the ventricles fill, AV valve flaps hang limply into ventricles Atria contract, forcing additional blood into ventricles AV valves open Ventricles (a) Figure 11. 5 a, step 3

Ventricles contract, forcing blood against AV valve flaps (a) Figure 11. 5 a, step 4

Ventricles contract, forcing blood against AV valve flaps AV valves close (a) AV valves closed Figure 11. 5 a, step 5

Ventricles contract, forcing blood against AV valve flaps AV valves close Chordae tendineae tighten, preventing valve flaps from everting into atria (a) AV valves closed Figure 11. 5 a, step 6

Operation of the semilunar valves Aorta Pulmonary trunk As ventricles contract and intraventricular pressure rises, blood is pushed up against semilunar valves, forcing them open Semilunar valve open (b) Figure 11. 5 b, step 1

Operation of the semilunar valves Aorta Pulmonary trunk As ventricles contract and intraventricular pressure rises, blood is pushed up against semilunar valves, forcing them open Semilunar valve open (b) As ventricles relax, and intraventricular pressure falls, blood flows back from arteries, filling the leaflets of semilunar valves and forcing them to close Semilunar valve closed Figure 11. 5 b, step 2

Systemic and Pulmonary Circulations n Systemic circulation – Blood flows from the left side of the heart through the body tissues and back to the right side of the heart n Pulmonary circulation – Blood flows from the right side of the heart to the lungs and back to the left side of the heart

Systemic and Pulmonary Circulations Figure 11. 3

The Heart: Associated Great Vessels n Arteries – Aorta § Leaves left ventricle – Pulmonary arteries § Leave right ventricle

The Heart: Associated Great Vessels n Veins – Superior and inferior venae cavae § Enter right atrium – Pulmonary veins (four) § Enter left atrium

The Heart: Associated Great Vessels Figure 11. 2 c

Blood Flow Through the Heart n Superior and inferior venae cavae dump blood into the right atrium n From right atrium, through the tricuspid valve, blood travels to the right ventricle n From the right ventricle, blood leaves the heart as it passes through the pulmonary semilunar valve into the pulmonary trunk n Pulmonary trunk splits into right and left pulmonary arteries that carry blood to the lungs

Blood Flow Through the Heart n Oxygen is picked up and carbon dioxide is dropped off by blood in the lungs n Oxygen-rich blood returns to the heart through the four pulmonary veins n Blood enters the left atrium and travels through the bicuspid valve into the left ventricle n From the left ventricle, blood leaves the heart via the aortic semilunar valve and aorta

Systemic and Pulmonary Circulations Figure 11. 3

Coronary Circulation n Blood in the heart chambers does not nourish the myocardium n The heart has its own nourishing circulatory system consisting of – Coronary arteries—branch from the aorta to supply the heart muscle with oxygenated blood – Cardiac veins—drain the myocardium of blood – Coronary sinus—a large vein on the posterior of the heart, receives blood from cardiac veins n Blood empties into the right atrium via the coronary sinus

The Heart: Conduction System n Intrinsic conduction system (nodal system) – Heart muscle cells contract, without nerve impulses, in a regular, continuous way

The Heart: Conduction System n Special tissue sets the pace § Sinoatrial node = SA node (“pacemaker”), is in the right atrium § Atrioventricular node = AV node, is at the junction of the atria and ventricles § Atrioventricular bundle = AV bundle (bundle of His), is in the interventricular septum § Bundle branches are in the interventricular septum § Purkinje fibers spread within the ventricle wall muscles

Heart Contractions Figure 11. 6

Heart Contractions n Contraction is initiated by the sinoatrial node (SA node) n Sequential stimulation occurs at other autorhythmic cells n Force cardiac muscle depolarization in one direction—from atria to ventricles

Heart Contractions n Once SA node starts the heartbeat – Impulse spreads to the AV node – Then the atria contract n At the AV node, the impulse passes through the AV bundle, bundle branches, and Purkinje fibers n Blood is ejected from the ventricles to the aorta and pulmonary trunk as the ventricles contract

Heart Contractions Figure 11. 6

Heart Contractions n Tachycardia—rapid heart rate over 100 beats per minute n Bradycardia—slow heart rate less than 60 beats per minutes

The Heart: Cardiac Cycle n Cardiac cycle — events of one complete heart beat n Atria contract simultaneously n Atria relax, then ventricles contract n Systole = contraction n Diastole = relaxation

The Heart: Cardiac Output n Cardiac output (CO) – Amount of blood pumped by each side (ventricle) of the heart in one minute n Stroke volume (SV) – Volume of blood pumped by each ventricle in one contraction (each heartbeat) – Usually remains relatively constant – About 70 m. L of blood is pumped out of the left ventricle with each heartbeat n Heart rate (HR) – Typically 75 beats per minute. Ave is 60 -80

The Heart: Cardiac Output = HR SV n CO = HR (75 beats/min) SV (70 m. L/beat) n CO = 5250 m. L/min n Starling’s law of the heart—the more the cardiac muscle is stretched, the stronger the contraction n Changing heart rate is the most common way to change cardiac output n CO

Heart sounds n Often describes as “lub dub”. n The first sound is the closing of the AV valves. n The second is the closing of the semilunar (aortic and pulmonary) valves. n Abnormal sounds are called MURMURS. This can indicate a valve sound.

Regulation of Heart Rate n Increased heart rate – Sympathetic nervous system § Crisis § Low blood pressure – Hormones § Epinephrine § Thyroxine – Exercise – Decreased blood volume

The Heart: Regulation of Heart Rate n Decreased heart rate – Parasympathetic nervous system – High blood pressure or blood volume – Decreased venous return

Cardiac Output Regulation Figure 11. 8

Blood Vessels: The Vascular System n Transport blood to the tissues and back – Carry blood away from the heart § Arteries § Arterioles – Exchanges between tissues and blood § Capillary beds – Return blood toward the heart § Venules § Veins

Blood Vessels: The Vascular System Figure 11. 9 a

Blood Vessels: Microscopic Anatomy n Three layers (tunics) – Tunic intima § Endothelium – Tunic media § Smooth muscle § Controlled by sympathetic nervous system – Tunic externa § Mostly fibrous connective tissue

Blood Vessels: The Vascular System Figure 11. 9 b

Differences Between Blood Vessels n Walls of arteries are thickest n Lumens of veins are larger n Larger veins have valves to prevent backflow n Skeletal muscle “milks” blood in veins toward the heart n Walls of capillaries are only one cell layer thick to allow for exchanges between blood and tissue

Blood Vessels: The Vascular System Figure 11. 9 a

Blood Vessels: The Vascular System Figure 11. 10

Capillary Beds n Capillary vessels beds consist of two types of – Vascular shunt—vessel directly connecting an arteriole to a venule – True capillaries—exchange vessels § Oxygen and nutrients cross to cells § Carbon dioxide and metabolic waste products cross into blood

Capillary Beds Figure 11. 11 a

Capillary Beds Figure 11. 11 b

Major Arteries of System Circulation n Aorta – Largest artery in the body – Leaves from the left ventricle of the heart – Regions § Ascending aorta—leaves the left ventricle § Aortic arch—arches to the left § Thoracic aorta—travels downward through the thorax § Abdominal aorta—passes through the diaphragm into the abdominopelvic cavity

Major Arteries of System Circulation n Arterial branches of the ascending aorta – Right and left coronary arteries serve the heart

The Heart

Major Arteries of Systemic Circulation n Arterial branches of the aortia arch (BCS) – Brachiocephalic trunk splits into the § Right common carotid artery § Right subclavian artery – Left common carotid artery splits into the § Left internal and external carotid arteries – Left subclavian artery branches into the § Vertebral artery § In the axilla, the subclavian artery becomes the axillary artery brachial artery radial and ulnar arteries

Major Arteries of Systemic Circulation n Arterial branches of the thoracic aorta – Intercostal arteries supply the muscles of the thorax wall – Other branches of the thoracic aorta supply the § Lungs (bronchial arteries) § Esophagus (esophageal arteries) § Diaphragm (phrenic arteries)

Major Arteries of Systemic Circulation n Arterial branches of the abdominal aorta – Celiac trunk is the first branch of the abdominal aorta. Three branches are § Left gastric artery (stomach) § Splenic artery (spleen) § Common hepatic artery (liver) – Superior mesenteric artery supplies most of the small intestine and first half of the large intestine

Major Arteries of Systemic Circulation n Arterial branches of the abdominal aorta – Left and right renal arteries (kidney) – Left and right gonadal arteries § Ovarian arteries in females serve the ovaries § Testicular arteries in males serve the testes – Lumbar arteries serve muscles of the abdomen and trunk

Major Arteries of Systemic Circulation n Arterial branches of the abdominal aorta – Inferior mesenteric artery serves the second half of the large intestine – Left and right common iliac arteries are the final branches of the aorta § Internal iliac arteries serve the pelvic organs § External iliac arteries enter the thigh femoral artery popliteal artery anterior and posterior tibial arteries

Figure 11. 12

Major Veins of Systemic Circulation n Superior and inferior vena cava enter the right atrium of the heart – Superior vena cava drains the head and arms – Inferior vena cava drains the lower body

The Heart Figure 11. 2 b

Major Veins of Systemic Circulation n Veins draining into the superior vena cava – Radial and ulnar veins brachial vein axillary vein – These veins drain the arms – Cephalic vein drains the lateral aspect of the arm and empties into the axillary vein – Basilic vein drains the medial aspect of the arm and empties into the brachial vein – Basilic and cephalic veins are jointed at the median cubital vein (elbow area)

Major Veins of Systemic Circulation n Veins draining into the superior vena cava – Subclavian vein receives § Venous blood from the arm via the axillary vein § Venous blood from skin and muscles via external jugular vein – Vertebral vein drains the posterior part of the head – Internal jugular vein drains the dural sinuses of the brain

Major Veins of Systemic Circulation n Veins draining into the superior vena cava – Left and right brachiocephalic veins receive venous blood from the § Subclavian veins § Vertebral veins § Internal jugular veins – Brachiocephalic veins join to form the superior vena cava right atrium of heart – Azygous vein drains the thorax

Major Veins of Systemic Circulation n Veins draining into the inferior vena cava – Anterior and posterior tibial veins and fibial veins drain the legs – Posterior tibial vein popliteal vein femoral vein external iliac vein – Great saphenous veins (longest veins of the body) receive superficial drainage of the legs – Each common iliac vein (left and right) is formed by the union of the internal and external iliac vein on its own side

Major Veins of Systemic Circulation n Veins draining into the inferior vena cava – Right gonadal vein drains the right ovary in females and right testicle in males – Left gonadal vein empties into the left renal vein – Left and right renal veins drain the kidneys – Hepatic portal vein drains the digestive organs and travels through the liver before it enters systemic circulation

Major Veins of Systemic Circulation n Veins draining into the inferior vena cava – Left and right hepatic veins drain the liver

Major Veins of Systemic Circulation Figure 11. 13

Arterial Supply of the Brain n Internal carotid arteries divide into – Anterior and middle cerebral arteries – These arteries supply most of the cerebrum n Vertebral arteries join once within the skull to form the basilar artery – Basilar artery serves the brain stem and cerebellum

Arterial Supply of the Brain n Posterior cerebral arteries form from the division of the basilar artery – These arteries supply the posterior cerebrum

Circle of Willis n Anterior and posterior blood supplies are united by small communicating arterial branches n Result—complete circle of connecting blood vessels called cerebral arterial circle or circle of Willis

Arterial Supply of the Brain Figure 11. 14

Fetal Circulation n Fetus receives exchanges of gases, nutrients, and wastes through the placenta n Umbilical cord contains three vessels – Umbilical vein—carries blood rich in nutrients and oxygen to the fetus – Umbilical arteries (2)—carry carbon dioxide and debris-laden blood from fetus to placenta

Fetal Circulation n Blood flow bypasses the liver through the ductus venosus and enters the inferior vena cava right atrium of heart n Blood flow bypasses the lungs – Blood entering right atrium is shunted directly into the left atrium through the foramen ovale – Ductus arteriosus connects the aorta and pulmonary trunk (becomes ligamentum arteriosum at birth)

Fetal Circulation Figure 11. 15

Hepatic Portal Circulation n Veins of hepatic portal circulation drain – Digestive organs – Spleen – Pancreas n Hepatic portal vein carries this blood to the liver n Liver helps maintain proper glucose, fat, and protein concentrations in blood

Hepatic Portal Circulation n Major vessels of hepatic portal circulation – Inferior and superior mesenteric veins – Splenic vein – Left gastric vein

Hepatic Portal Circulation Figure 11. 16

Hepatic Portal Circulation Figure 11. 17

Pulse n Pulse – Pressure wave of blood n Monitored at “pressure points” in arteries where pulse is easily palpated n Pulse averages 70– 76 beats per minute at rest

Pulse Figure 11. 18

Blood Pressure n Measurements by health professionals are made on the pressure in large arteries – Systolic—pressure at the peak of ventricular contraction – Diastolic—pressure when ventricles relax – Write systolic pressure first and diastolic last (120/80 mm Hg) n Pressure in blood vessels decreases as distance from the heart increases

Comparison of Blood Pressures in Different Vessels Figure 11. 19

Measuring Arterial Blood Pressure Figure 11. 20 a

Measuring Arterial Blood Pressure Figure 11. 20 b

Measuring Arterial Blood Pressure Figure 11. 20 c

Measuring Arterial Blood Pressure Figure 11. 20 d

Blood Pressure: Effects of Factors n BP is blood pressure – BP is affected by age, weight, time of day, exercise, body position, emotional state n CO is the amount of blood pumped out of the left ventricle per minute n PR is peripheral resistance, or the amount of friction blood encounters as it flows through vessels – Narrowing of blood vessels and increased blood volume increases PR n BP = CO PR

Blood Pressure: Effects of Factors n Neural factors – Autonomic nervous system adjustments (sympathetic division) n Renal factors – Regulation by altering blood volume – Renin—hormonal control

Blood Pressure: Effects of Factors n Temperature – Heat has a vasodilating effect – Cold has a vasoconstricting effect n Chemicals – Various substances can cause increases or decreases n Diet

Factors Determining Blood Pressure Figure 11. 21

Variations in Blood Pressure n Normal human range is variable – Normal § 140– 110 mm Hg systolic § 80– 75 mm Hg diastolic – Hypotension § Low systolic (below 110 mm HG) § Often associated with illness – Hypertension § High systolic (above 140 mm HG) § Can be dangerous if it is chronic

Capillary Exchange n Substances exchanged due to concentration gradients – Oxygen and nutrients leave the blood – Carbon dioxide and other wastes leave the cells

Capillary Exchange: Mechanisms n Direct diffusion across plasma membranes n Endocytosis or exocytosis n Some capillaries have gaps (intercellular clefts) – Plasma membrane not joined by tight junctions n Fenestrations (pores) of some capillaries

Capillary Exchange: Mechanisms Figure 11. 22

Fluid Movements at Capillary Beds n Blood pressure forces fluid and solutes out of capillaries n Osmotic pressure draws fluid into capillaries n Blood pressure is higher than osmotic pressure at the arterial end of the capillary bed n Blood pressure is lower than osmotic pressure at the venous end of the capillary bed

Fluid Movements at Capillary Beds Figure 11. 23

Electrocardiogram (EKG or ECG) checks for problems with the heart’s electrical activity

Atrial tachycardia Ventricular tachycardia

Homeostatic imbalance Aneurysm: Blood filled sac in an arterial wall causing dilation and weakening of the wall

Varicose veins n Pooling of blood in the feet and legs. Valves malfunction causing twisting and dilation.

Pulmonary embolism Clot free floating n Gets caught in lungs n Life threatening n

Atherosclerosis Arterial walls thicken with fatty deposits or plaquing n Narrows the lumen n Risk factors include smoking Stress Lack of exercise Poor diet n

Balloon angioplasty

Major Risk Factors High blood pressure. Blood pressure is considered high if it stays at or above 140/90 mm. Hg over time. If you have diabetes or chronic kidney disease, high blood pressure is defined as 130/80 mm. Hg or higher. n Unhealthy blood cholesterol levels. This includes high LDL cholesterol (sometimes called "bad" cholesterol) and low HDL cholesterol (sometimes called "good" cholesterol n Smoking can damage and tighten blood vessels, raise cholesterol levels, and raise blood pressure. n Diabetes. With this disease, the body's blood sugar level is too high because the body doesn't make enough insulin or doesn't use its insulin properly. n

n n n n Overweight or obesity. The terms "overweight" and "obesity" refer to body weight that's greater than what is considered healthy for a certain height. Lack of physical activity. A lack of physical activity can worsen other risk factors for atherosclerosis, such as unhealthy blood cholesterol levels, high blood pressure, diabetes, and overweight and obesity. Unhealthy diet. An unhealthy diet can raise your risk for atherosclerosis. Foods that are high in saturated and trans fats, cholesterol, sodium (salt), and sugar can worsen other atherosclerosis risk factors. Older age. As you get older, your risk for atherosclerosis increases. Genetic or lifestyle factors cause plaque to build up in your arteries as you age. By the time you're middle-aged or older, enough plaque has built up to cause signs or symptoms. In men, the risk increases after age 45. In women, the risk increases after age 55. Family history of early heart disease. Your risk for atherosclerosis increases if your father or a brother was diagnosed with heart disease before 55 years of age, or if your mother or a sister was diagnosed with heart disease before 65 years of age. Although age and a family history of early heart disease are risk factors, it doesn't mean that you'll develop atherosclerosis if you have one or both. Controlling other risk factors often can lessen genetic influences and prevent atherosclerosis, even in older adults. Studies show that an increasing number of children and youth are at risk for atherosclerosis. This is due to a number of causes, including rising

Family history of early heart disease. Your risk for atherosclerosis increases if your father or a brother was diagnosed with heart disease before 55 years of age, or if your mother or a sister was diagnosed with heart disease before 65 years of age. n Although age and a family history of early heart disease are risk factors, it doesn't mean that you'll develop atherosclerosis if you have one or both. Controlling other risk factors often can lessen genetic influences and prevent atherosclerosis, even in older adults. n Studies show that an increasing number of children and youth are at risk for atherosclerosis. This is due to a number of causes, including n

Family history of early heart disease. Your risk for atherosclerosis increases if your father or a brother was diagnosed with heart disease before 55 years of age, or if your mother or a sister was diagnosed with heart disease before 65 years of age. n Although age and a family history of early heart disease are risk factors, it doesn't mean that you'll develop atherosclerosis if you have one or both. Controlling other risk factors often can lessen genetic influences and prevent atherosclerosis, even in older adults. n Studies show that an increasing number of children and youth are at risk for atherosclerosis. This is due to a number of causes, including rising childhood obesity rates. n

CHF n Pumping efficiency so poor that circulation is inadequate. n If it is on the right side, pulmonary edema occurs. n If it fails then peripheral edema occurs.

Angina pectoris n Chest pan or discomfort secondary to oxygen deprivation of the heart muscle. n People take nitroglycerine which dilates the blood vessels. n If it continues then M. I occurs.

Myocardial infarction Damage or death to myocardium due to oxygen being deprived n Warning sign is angina pectoris (pain in the chest) n

Stroke

Developmental Aspects of the Cardiovascular System n. A simple “tube heart” develops in the embryo and pumps by the fourth week n The heart becomes a four-chambered organ by the end of 7 th week n Few structural changes occur after the seventh week

Congenital defects n Account for about ½ of infant deaths n Environmental interferences like maternal infection and ingested drugs during the first trimester seem to be the major cause of problems. n Congenital defects include ductus arteriosus that does not close, septal openings and other structural abnormalities.

n Patent ductus arteriosus (PDA) is a congenital disorder in the heart wherein a neonate's ductus arteriosus fails to close after birth. Early symptoms are uncommon, but in the first year of life include increased work of breathing and poor weight gain.

Developmental Aspects of the Cardiovascular System n Aging problems associated with the cardiovascular system include – Venous valves weaken – Varicose veins – Progressive atherosclerosis – Loss of elasticity of vessels leads to hypertension – Coronary artery disease results from vessels filled with fatty, calcified deposits