Cardiovascular System

1. Unit 10 Cardiovascular System

2. Structure and Function • Three parts: • Heart • Blood vessels • Blood • Function = transports oxygen, nutrients, cell wastes, hormones, etc., distributes body heat

3. Anatomy of the Heart • Approximately the size of a fist, hollow, cone-shaped • Inside the bony thorax between the lungs • Pointed apex is angled toward left hip, rests on the diaphragm at the same level as the fifth intercostal space • Broader base points towards right shoulder blade, beneath second rib

4. Anatomy of the Heart

5. Anatomy of the Heart • Enclosed by a double sac of serous membrane = pericardium • The thin epicardiumhugs the external surface of the heart and is part of the heart wall • Myocardium = thick middle layer made of thick bundles of cardiac muscles twisted into ring-like arrangements, this is the layer that actually contracts • Endocardium = thin inner layer, lubricated sheet of endothelium, continuous with the linings of the blood vessels leaving and entering the heart, allows blood to flow more smoothly • Pericarditis = inflammation of the pericardium, causes pericardial layers to stick to each other, forming painful adhesions that interfere with heart movements

6. Anatomy of the Heart

7. Anatomy of the Heart • Four chambers • Atria = top chambers, receive blood • Right atrium = receives from body, deoxygenated blood • Left atrium = receives from lungs, oxygenated blood • Ventricles = bottom chambers, pump blood out of heart • Left ventricle = pumps to body, oxygenated blood • Right ventricle = pumps to lungs, deoxygenated blood • Interventricular and interatrial septum = divides heart longitudinally

8. Anatomy of the Heart

9. Major Heart Vessels • Vena cava = brings blood from body to right atrium • Superior vena cava = blood from above the heart • Inferior vena cava = blood from below the heart • Pulmonary veins = bring blood from lungs to left atrium • Aorta = large artery that carries blood from left ventricle to rest of body • Pulmonary arteries = carry blood from right ventricle to lungs

10. Major Heart Vessels

11. Heart Valves • Allow blood to flow in only one direction: atria  ventricles  arteries • Atrioventricular valves (AV) = between atrial and ventricular chambers • Bicuspid valve= two cusps (flaps of endocardium), between left atrium and ventricle, also known as mitral valve • Tricuspid valve = three cusps, between right atrium and ventricle • Chordaetendineae– “heart strings,” anchor cusps to ventricles, help keep them closed • Semilunar valves = base of the two large arteries • Pulmonary semilunar valve = base of pulmonary artery • Aortic semilunar valve = base of aorta

12. Heart Valves

13. How does the heart beat? • Double pump – right side = pulmonary (lungs), left side = systemic (rest of body) • Both atria contract together and both ventricles contract together

14. How does the heart beat? • Cardiac cycle = start of one heart beat to the initiation of the next • Heart usually beats ~75 times per minute • Cardiac cycle usually lasts ~0.8 seconds • Systole = heart contraction • Diastole = heart relaxation • Three main phases of cardiac cycle: • 1. Mid-to-late diastole • 2. Ventricular systole • 3. Early diastole

15. How does the heart beat? • 1. Mid-to-late diastole: • Heart in complete relaxation  pressure in heart is low, blood is flowing passively into the atria • Semilunar valves are closed • AV valves are open • The atria contract and force the blood into the ventricles • 2. Ventricular systole: • The pressure building in the ventricles closes the AV valves, then opens the semilunar valves • Blood rushes out of ventricles into arteries • Atria are relaxed during this phase and starting to fill up with blood again • 3. Early diastole: • Ventricles relax and semilunar valves close to prevent backflow  ventricles are completely closed chambers, pressure drops • When the pressure drops low enough, the AV valves open

16. How does the heart beat? • Cardiac muscles can contract spontaneously, even if all nervous connections are severed. • Different rhythms in different areas of the heart  atria = 60 beats/minute, ventricles = 20-40 beats/minute  needs unifying control • Two main systems: intrinsic conduction system (nodal system) and autonomic nervous system • Autonomic nervous system acts like “brakes” or “gas pedal”  decrease or increase heart rate

17. How does the heart beat? • Intrinsic conduction system is built into the heart tissue – found nowhere else in the body • Causes heart depolarization from atria to ventricles • Enforces rate of ~75 beats per minute • Path of signal: • Sinoatrial (SA) node – right atrium  “pacemaker” • Atrioventricular (AV) node – junction of atria and ventricles • Atrioventricular (AV) bundle (bundle of His) – junction of atria and ventricles • Right and left bundle branches – to right and left of bundle of His • Purkinje fibers – spread throughout ventricle muscle walls

18. Warm up video questions – Copy on your own paper • 1. What is the new craze sweeping the nation? • 2. “Out through your ______, in through your ________.” • 3. What are two signs that you’re “not circulating right?” (These are mentioned at different times in the video). • 4. What are the four parts of the heart mentioned in the song? • 5. What does circulation take to your cells? • 6. What does circulation get rid of for your cells? • 7. What jobs do red and white blood cells have? • http://www.youtube.com/watch?v=5tTkxYeNF9Q

19. Electrocardiogram (ECG) • Traces the flow of electric current through the heart • 3 waves: • P wave – small, signals depolarization of atria before they contract • QRS complex – the “peak,” symbolizes depolarization of ventricles before they contract, repolarization of atria is generally hidden by this complex • T wave – repolarization of ventricles

20. Electrocardiogram (ECG)

21. Blood Vessels • Blood circulates through the body in a closed transport system  “vascular system” • Leaves the heart in large arteries • Moves to smaller arteries  arterioles  capillary beds • Capillary beds drain into venules  small veins  veins leading to heart • Arteries, arterioles, veins, and venules = transporting blood • Capillaries = where the exchange between tissue cells and blood occur

22. Blood Vessels

23. Blood Vessels • Blood vessels (except for capillaries) have three coats, or tunics • Tunica interna– Lines the interior of the vessels, thin layer of endothelium resting on loose layer of connective tissue, cells fit close together to make slippery surface that decreases friction as blood flows through • Tunica media – bulky middle coat, smooth muscle and elastic tissue, controlled by sympathetic nervous system, changes diameter of blood vessels and therefore, blood pressure • Tunica externa – outermost layer, fibrous connective tissue, supports and protects vessels

24. Blood Vessels

25. Blood Vessels • Arteries tend to have thicker walls than veins • Some larger arteries even have elastic laminae, complete sheets of elastic tissue within their tunica media • Arteries must be able to expand as blood is forced into them and relax when it leaves during diastole  walls must be strong and stretchy to handle continuous changes in pressure • Veins have thinner walls and have much lower pressure • Sometimes have to work against gravity • Lumens are larger than those in arteries • Valves to prevent backflow of blood • Skeletal muscles help “milk” blood back to heart • Inhaling also causes a drop in pressure that causes the big veins near the heart to expand and fill

26. Blood Vessels • Capillary walls are just one cell layer thick  easier to make exchanges between blood and tissue cells • Capillary beds = interweaving networks of tiny capillary vessels • Microcirculation – flow of blood from arteriole  capillary bed  venule • Two parts to capillary bed: • Vascular shunt – vessel that connects to arteriole and venule at opposite ends of bed • True capillaries – actual exchange vessels, 10-100 per bed

27. Blood Vessels • Capillaries form such an intricate network so that no substance has to diffuse very far to enter or leave a cell • Space between tissue cells and capillaries is filled with interstitial fluid • Substances move according to their concentration gradients  high to low • Can take one of four “routes:” • 1. Diffuse directly across plasma membrane if they are lipid soluble (ex. Respiratory gases) • 2. Endocytosis or exocytosis – moving within vesicles • 3. Fluid can flow through intercellular clefts (gaps between cells) • 4. Small solutes and fluids can move through fenestrated capillaries, which are usually found where absorption or filtration is a priority (ex. Intestine, kidneys) • Only substances that cannot pass through these “routes” will remain in capillaries (ex. Proteins, blood cells)

28. Important arteries • Ascending aorta • Aortic arch • Thoracic aorta • Abdominal aorta • Right and left common iliac arteries • Brachiocephalic artery • Right and left subclavian arteries • Right and left common carotid arteries

29. Important Veins • Superior and inferior vena cava • Brachiocephalic vein • Internal and exterior jugular veins • Vertebral vein • Subclavian vein • Basilic vein • Cepalicvein • Hepatic portal vein • Hepatic veins • Renal veins • Internal, external, and common iliac veins • Great saphenous vein (longest in body) • Femoral vein • Fibular vein • Anterior and posterior tibial veins

30. Special Circulations – Brain • Need continuous blood supply to the brain • Two pairs of arteries: internal carotid arteries and vertebral arteries • Internal carotid arteries go through neck and temporal bone, then divides into anterior and middle cerebral arteries • Vertebral arteries go through base of neck then join inside the skull to form basilar artery, which serves the brain stem and cerebellum. It then divides again to form the posterior cerebral arteries. • Anterior and posterior blood supplies are connected by small communicating arterial branches  a complete circle of connecting blood vessels called the circle of Willis • Circle of Willis protects brain by providing more than one route for blood to reach the brain in case of clots or impaired blood flow

31. Special Circulations - Brain

32. Special Circulations – Hepatic Portal • Drains blood from digestive organs, spleen, and pancreas and delivers it to the liver through the hepatic portal vein • Liver processes the nutrients from food to help maintain the balance of glucose, fat, and protein concentrations in the blood  some get removed for storage • Liver is drained by hepatic veins  inferior vena cava • Unique because normally arteries  capillaries  veins, but in this case, veins feed the liver circulation

33. Special Circulations – Hepatic Portal

34. Special Circulations - Fetal • Nutrient, excretory, and gas exchanges all happen through placenta because lungs and digestive system are not yet functioning. • Nutrients and oxygen move from mother to baby while wastes move in the other direction. • Umbilical cord has three blood vessels: one umbilical vein and two umbilical arteries • Vein carries blood with nutrients and oxygen to baby while the arteries carry CO2 and other waste to the placenta • Blood flows mainly to the heart of the fetus, bypassing the immature liver through the ductusvenosus which enters the inferior vena cava

35. Special Circulations - Fetal • Since lungs aren’t being used, two shunts help bypass them • Blood entering right atrium goes straight to left atrium through foramen ovale • Blood that makes it to the right ventricle is pumped out pulmonary trunk to ductusarteriosus, where it is pumped back to the aorta. • At birth, the foramen ovale closes and the ductusarteriosus collapses and is converted to fibrous ligamentumarteriosum(connects aorta to pulmonary artery)

36. Special Circulations - Fetal

37. Physiology of Circulation • Pulse – rhythmic expansion and recoil of arteries resulting from heart beating  can be felt outside of body when an artery is close to the body surface • Pulse can be influenced by activity, postural changes, and emotions • Pressure points – points where pulse can be most easily felt; they are compressed to stop blood flow during hemorrhaging

38. Physiology of Circulation • Blood pressure = pressure blood exerts against inner walls of blood vessels • The force that keeps blood circulating continuously, even between heartbeats  blood moves from high to low pressure • Systolic pressure – pressure in the arteries at the peak of ventricle contraction • Diastolic pressure – pressure when ventricles are relaxing • Blood pressure is measured in millimeters of mercury (mm Hg) and with the systolic pressure over the diastolic pressure (ex. 120/80) • Hypertension = chronic high blood pressure (140/90 or higher)

39. Physiology of Circulation • Blood pressure is usually measured through the auscultatory method: • Blood flow is stopped through an inflated blood pressure cuff. • As the pressure in the cuff is slowly released, the examiner listens carefully for two signals. • The first signal is a soft tapping sound as blood starts to spurt through the artery  this is recorded as systolic pressure. • The second signal is when the tapping sound can no longer be heard  this point is recorded as diastolic pressure

40. Physiology of Circulation • Blood pressure is directly related to cardiac output and peripheral resistance (the amount of friction encountered by the blood as it flows through the vessels) • Factors that can affect blood pressure: • Age • Weight • Time of day • Exercise • Body position • Emotional state • Drugs • Kidneys • Temperature • Diet