CARDIOVASCULAR SYSTEM
CARDIAC SYSTEM
TWO TYPES OF CIRCULATION Systemic system delivers blood to ALL body cells and carries away waste. The red blood cells use hemoglobin to carry oxygen to the cells Pulmonary system eliminates CO 2 and oxygenates blood. In the lungs, the red blood cells are oxygenated and CO 2 is released, which we then exhale.
LOCATION OF THE HEART Mediastinum the location of the heart in the chest cavity, behind the sternum, between the lungs and in front of the back bone, between the 2 nd and 5 th intercostal space.
EXTERNAL STRUCTURE OF THE HEART Pericardium encloses the heart like a sac, it has two layers Fibrous pericardium protects the heart and anchors it to the surrounding structures. Serous pericardium a slippery, two part layer that lines the interior of the fibrous and then folds and covers the external heart. The pericardial cavity contains serous fluid to lubricate the surface of the heart to reduce friction and allow the heart to beat easier.
THREE LAYERS OF THE HEART WALL Epicardium outer layer, reduces friction Myocardium middle layer, mostly cardiac muscle Epicardium thin inner layer of heart wall that is continuous with blood vessels.
ANATOMY OF THE HEART The left ventricle is larger, it extends to a point that is called the Apex. The heart muscles need blood. They receive blood though the external arteries. These arteries branch off of the aorta and bring oxygenated blood to the heart wall. The veins dump the deoxygenated blood back into the left atrium.
ANATOMY OF THE HEART The heart has two atria, which are the upper chambers. They receive blood from veins, that are returning from the distal extremities to the heart. The heart also has two ventricles which receive blood from the atria, that blood is then pumped through arteries. The interventricular/interatrial septum splits the left and right sides of the heart. The RIGHT ventricle pumps blood through the pulmonary system and the LEFT ventricle pumps blood through the systemic system.
THE VALVES There are four valves in the heart One between each atrium and ventricle (2 total) Atrioventricular valves Left AV mitral/bicuspid valve Right AV tricuspid valve One between each ventricle and artery (2 total) Semilunar valves Right pulmonary valve Left aortic valve Anchored by the chordae tendonae to the heart wall
PATH OF BLOOD FLOW Left ventricle aortic valve aorta systemic circulation Superior and inferior vena cava right atrium tricuspid valve right ventricle pulmonary valve pulmonary trunk lungs pulmonary veins left atrium bicuspid valve left ventricle
HEART RHYTHMS Two rhythms one from the autonomic nervous system, the nerves that branch to the heart act like brakes and a gas pedal, accelerating and decelerating the heart rate. The other rhythm is the intrinsic conduction system which sets the basic rhythms. Produced from a special tissue only found in the heart, it acts like a cross between muscle and nervous tissue.
INTRINSIC CONDUCTION (NODAL) SYSTEM Causes heart depolarization in one direction, from atria to ventricles. Two nodes: Sinoatrial (SA) node - pacemaker located in the RIGHT atrium. Produces the first contraction at the atria when it signals the AV node. Atrioventricular (AV) node junction of atria and ventricles, delays contraction in the ventricles to allow the atria to finish contracting. Other components: Atrioventricular bundle (Bundle of His) Purkinje fibers branches from the bundle of His and is located in the interventricular septum. They run from the apex toward the atria.
CARDIAC CYCLE The atria and ventricles cycle between systole and diastole. Systole contraction (depolarization) of the atrium or ventricle Diastole relaxation (repolarization) of atrium or ventricle. Cardiac cycle is one complete heart beat, atrial contraction and relaxation paired with ventricular contraction and relaxation. An atria cannot be contracted at the same time as a ventricle. The atria will depolarize, and as it repolarizes the ventricle will contract.
HEART SOUNDS During the cardiac cycle there are distinct sounds that are made by the heart while beating Lub closing of the AV valves at beginning of systole. Dupp closing of pulmonary and aortic valves Any sounds outside of these can indicate other problems Regurgitation backflow of blood through a valve. Stenosis moves forward through an incompletely open valve.
ELECTROCARDIOGRAMS Electrocardiograms are machines that measure the electrical activity of the heart. The recording is called an electrocardiograph, and this can alert a physician of potential issues in the cardiac cycle. Three major peaks: P wave depolarization of atria QRS complex depolarization of ventricles T wave - repolarization of ventricles
ABNORMAL ECG READINGS Bradycardia is a heartbeat that is too slow, the ECG will show an inverted T wave. This means that the ventricular repolarization is affected and it is taking longer to beat. Tachycardia is a rapid heart beat, this presents on an ECG as a short pause between T and P waves.
ABNORMAL ECG READINGS Bradycardia is a heartbeat that is too slow, the ECG will show an inverted T wave. This means that the ventricular repolarization is affected and it is taking longer to beat. Tachycardia is a rapid heart beat, this presents on an ECG as a short pause between T and P waves.
ABNORMAL ECG READINGS Heart blocks blockage of the electrical pathway, can change in severity depending on the blockage. First degree slowed movement through the AV node Second degree slowed, might skip a beat, irregular pattern Third degree - no signal sent from atria to ventricles
VASCULAR SYSTEM
BLOOD VESSELS Blood leaves the heart in arteries and returns through veins. Arteries à Arterioles à Capillary beds à Venules à Veins Arteries and veins are made up of three layers called tunics.
TUNICS Tunica interna lines the lumen of the vessels, it is a thin layer of epithelium resting on a basement membrane Tunica media middle layer, thick layer made of mostly smooth muscle and elastic fibers. This layer is different in arteries and veins. Arteries have elastic lamina added to this layer, which helps in vasodilation. Tunica Externa (adventitia) the outermost layer, made of mostly fibrous connective tissue, it supports and protects the vessels.
STRUCTURAL DIFFERENCES OF ARTERIES AND VEINS Arteries are thick and elastic, they withstand intense pressure while the heart is beating. They must expand and contract in response to the pressure. Veins are thinner, and have very low pressure because of the distance to the heart. Blood has to flow against gravity, so veins have valves to keep blood from flowing back down. Our muscles are used to help move the blood along the veins by putting pressure on them and then releasing.
CAPILLARIES Capillaries are one cell thick, this allow for blood to exchange gases with tissues and vice versa. A capillary bed contains two types of vessels, vascular shunts and true capillaries. Vascular shunts vessels that connect the terminal arteriole and post-capillary venule directly. True capillaries are called exchange vessels. There can be anywhere from 10 100 per bed, they branch from the terminal arteriole end to the post-capillary venules. Precapillary sphincters are smooth muscle cuffs that surround the root of each true capillary. It acts as a valve to regulate blood flow.
MAJOR ARTERIES: AORTIC ARCH Ascending aorta - Before reaching the arch there are two coronary arteries that branch off the ascending aorta and supply the heart muscle with oxygenated blood. The aortic arch has three branches Brachiocephalic artery (trunk) supplies head and right arm Splits into the right subclavian (arm) and right common carotid Left common carotid supplies the left side of the head Splits into the L. internal carotid and L. external carotid Left subclavian artery supplies the left arm Branches into the vertebral artery (supplies the brain) and continues into the arm. In the arm it becomes the axillary artery. The axillary artery becomes the brachial artery (supplies arm), which splits at the elbow into the radial and ulnar arteries.
MAJOR ARTERIES: THORACIC AORTA The thoracic aorta supplies blood to arteries in the chest cavity. It has four branches: The intercostal arteries supply the muscles of the thorax wall. The bronchial arteries supply the lungs. The esophageal arteries supply the esophagus. The phrenic arteries supply the diaphragm.
MAJOR ARTERIES: THE ABDOMINAL AORTA The abdominal aorta supplies most of the major organs. It has several branches, they are: Celiac trunk splits into three branches L. gastric artery stomach Splenic artery spleen Common hepatic artery liver Superior mesenteric artery supplies most of the small intestines and the first part of the large intestine. Renal arteries kidneys Gonadal arteries gonads (ovaries/testes) Inferior mesenteric artery large intestine Common iliac artery pelvis
MAJOR ARTERIES: LOWER EXTREMITIES The common iliac artery continues through the pelvis, it splits into the internal and external iliac artery. Internal iliac supplies pelvic organs (bladder, rectum, etc) External iliac continues into the leg and becomes the femoral artery Femoral artery branches into the deep and superficial femoral. The deep supplies the thigh and branches at the knee. The popliteal artery supplies the knee. Branches into anterior and posterior arteries that supply the foot. Dorsalis pedis terminal artery in the foot.
MAJOR VEINS: SUPERIOR VENA CAVA Deep Radial and ulnar veins forearm; unites to form the brachial vein Brachial vein arm, empties into axillary vein Superficial Cephalic vein lateral arm, empties into axillary vein Basilic vein medial arm, empties into brachial Joins with the cephalic vein to form the median cubital vein (most used site for blood draw) Subclavian vein receives blood from the axillary vein and external jugular vein. External jugular skin and muscles of the head Vertebral vein posterior head Internal jugular vein dural sinuses Brachiocephalic vein receive drainage from vertebral, subclavian, and jugular and both right and left sides join to form the superior vena cava.
MAJOR VEINS: INFERIOR VENA CAVA Leg (Deep): Anterior and posterior tibial veins and the fibular vein drain the lower leg. The posterior tibial becomes the popliteal vein behind the knee. The popliteal vein becomes the femoral vein in the thigh. Leg (Superficial): Pelvis The great saphenous vein drains the superficial leg. It is the longest vein in the body. It begins in the dorsal venous arch of the foot. The femoral vein becomes the external iliac vein when it enters the pelvis. The common iliac vein is formed when the external and internal iliac veins unite. Abdomen The left and right gonadal veins drain the gonads. The left gonadal drains into the left renal vein, while the right drains into the inferior vena cava. The renal veins drain the kidneys The hepatic portal vein drains the digestive tract organs into the liver before returning into the systemic circulation. Hepatic veins drain the liver
SPECIAL CIRCULATION: BRAIN The brain is supplied by two sets of arteries, the internal carotid and vertebral arteries. The internal carotid splits into the anterior and middle cerebral arteries. The vertebral arteries join to form the basilar artery which supplies the brain stem and cerebellum. The basilar divides at the base of the cerebrum into the posterior cerebral arteries that supply the posterior cerebrum. The anterior and posterior blood supplies unite by small communicating branches. The result is called the circle of Willis or the cerebral arterial circle.
SPECIAL CIRCULATION: FETAL Umbilical cord: three blood vessels One umbilical vein and two arteries. Heart: Vein carries nutrient and oxygen rich blood to the fetus. Arteries take CO 2 and waste to the mother. Blood bypasses the liver on the way toward the heart from the veins, it travels through the ductus venosus to enter the inferior vena cava. Right atrium à left atrium through foramen ovale Right ventricle à aorta through ductus arteriosis After birth: Foramen ovale closes Ductus arteriosis becomes ligamentum arteriosum When the umbilical cord is cut, the circulatory pattern becomes like an adult.
SPECIAL CIRCULATION: HEPATIC PORTAL The veins of organs of the digestive system converge to form the hepatic portal vein, which enters the liver. The liver regulates the nutrient content of the blood so the blood has to take a trip through the liver after digestion. The liver is drained by the hepatic veins In normal circulation, arteries fill capillaries and veins drain them, in the hepatic portal the opposite is true. The veins feed the capillaries, which will feed to arteries. Major feeding vessels: Inferior and superior mesenteric veins Splenic vein L. gastric vein
VITAL SIGNS: PULSE Pulse is the alternating expansion and recoiling of an artery that occurs during the beat of the left ventricle. Normal pulse rate is between 70-76 bpm during rest. Maximum heart rate is calculated by subtracting your age from 220. Pulse rate can be influenced by activity, emotion, or posture. Cardiac output = HR X SV SV stroke volume the amount of blood moved per heart beat Finding a pulse: There are several places that a pulse can be palpated. The most common is in the radial and common carotid arteries. Blood loss: When there is blood loss, these points can also be used to stop or slow blood flow to the area below the pressure point. If pressure is applied.
VITAL SIGNS: BLOOD PRESSURE Blood pressure is the force exerted on the walls of the blood vessels. Arteries have the highest pressure, and veins have the lowest pressure. The pressure gradient flows from high to low. The pressure keeps blood moving in between heart beats Measuring blood pressure: Auscultatory method - uses a blood pressure cuff and stethoscope. Pressure is increased in the cuff until the sound of arterial blood flow ceases, then pressure is released. Systolic pressure pressure of the artery at the peak of ventricular contraction. Diastolic pressure pressure at relaxation of ventricles. Blood pressure is read systolic over diastolic, normal is 120 systolic and 80 diastolic, it would be written: 120/80.
BLOOD PRESSURE CONDITIONS High blood pressure (hypertension) can be caused by atherosclerosis, which reduces the size of the arteries, it can also be caused by other factors such as: diet, race, age, emotions, hormones. Low blood pressure (hypotension) it can be caused by physical conditioning, and old age. Peripheral resistance (PR) the amount of friction the blood runs into