Circulatory System

1. Main components: heart, blood vessels, and blood
2. Heart
• muscular organ that pumps blood through by repeated contractions
• cardiac means "related to the heart" 
• made up of mostly cardiac muscle tissue
• found in the left to middle of the chest
• largest part slightly to the left
• left ventricle is stronger
• left lung smaller because heart takes up space
3. Blood flow through the heart
• two different loops
• left side loop and right side loop
• right side
• collects deoxygenated blood from body and pimps it into lungs
• releases carbon dioxide and picks up oxygen
• left side
• carries oxygenated blood back from lungs
• through the heart, then through the rest of the body
4. Heart has four chambers
• two upper atria
• thin-walled blood collection chambers
• pump blood into ventricles
• two lower ventricles
• heart chambers that pump blood into the body
• right side of heart
• deoxygenated blood enters right atrium
• blood enters right ventricle and pumps blood through pulmonary arteries and into the lungs
• carbon dioxide is released and oxygen picked up
• pulmonary veins bring oxygenated blood back to heart and into left atrium
• blood moves to left ventricle, which pumps it into the body through the aorta
• lower ventricles are thicker and stronger than upper atria
• muscle wall surrounding left ventricle is stronger than muscle wall around right ventricle
1. left ventricle needs to exert enough force to pump blood throughout whole body
2. right ventricle only needs enough force to pump blood to the lungs
5. Valves
• maintains flow of blood by opening and closing in one direction only
• blood can only move forward through the heart, and prevented from flowing backwards by valves
• unidirectional flow
• atrioventricular (AV) valves make sure blood flows from atria to ventricles
• on right side of heart: tricuspid valve
• left side: mitral/bicuspid valve
• semilunar (SL) valves prevent blood flowing back from arteries into ventricles
• right side: pulmonary valve because it leads to pulmonary arteries
• left side: called aortic valve because it leads to aorta
6. Heartbeat
• meshwork of cardiac muscles
• interconnected by gap junctions
• allows electric stimulation to spread quickly
• self-exciting muscle
• contrast to skeletal muscle, which needs nervous stimulation to contract
• heart rate can be changed by nervous or hormonal signals
7. Control of heartbeat
• sinoatrial node (SA node) "cardiac pacemaker" 
• upper wall of right atrium
• responsible for wave of electrical stimulation by creating action potential
• causes cardiac cells to contract
• contraction reaches atrioventricular node (AV node) 
• lower right atrium
• conducts electrical impulse that comes from SAT node to ventricles
• impulse is delayed, so allows ventricles to fill with blood before ventricles contract
• heartbeat controlled by nerve messages from autonomic nervous system
• Bundle of His
• collection of heart muscle cells
• specialized for electrical conduction that transmits electrical impulses from AV node
• branches into Purkinje fibers
1. specialized cardiac muscles
2. conduct action potential
3. causes ventricles to contract in controlled way
8. Heartbeat: two parts
• systole: contraction of heart chambers, driving blood out of chambers
• distole: when heart relaxes after contraction
• all four chambers undergo systole and distole so blood would keep moving
• when chambers are referred to, usually talking about ventricles
9. Heart sounds
• lub-dub, lub-dub
• heart valve shutting down causes those heart sounds/heartbeat
• valve closes when pressure falls below aorta and pulmonary artery pressure
10. Blood vessels
• transport blood throughout body
• arteries: large, muscular vessels that carry blood away from the heart
• arteriole: small diameter blood vessel that branches from an artery and leads to capillaries
• veins: carry blood toward heart, especially low-oxygen blood from tissues
• venule: small vessel that allows deoxygenated blood to return from capillaries to veins
• capillaries: smallest of body's blood vessels, important for interchange of gases and other substances between blood and body cells
• structure: 
• endothelium: thin layer of cells that creates smooth inner lining
• endothelium tissue is specialized endothelium
• lines entire circulatory system, and has layer of smooth muscle, well developed in arteries
• connective tissue around smooth muscle (made mostly of collagen) 
1. contains nerves that supply smooth muscular layer
2. ones surrounding larger vessels contain capillaries to bring nutrients to tissue
• capillaries made up of single layer of endothelium and small amount of connective tissue
11. Arteries and arterioles (in more detail) 
• carries blood away from heart
• three major layers
• inner endothelium layer
• middle layer of smooth muscle
• outer layer of connective tissue (stretchy) 
• elastic quality allows them to carry pressurized blood from heart to body
• aorta is largest artery in body
• receives blood from left ventricle of heart through aortic valve
• branches into arteries and arterioles
• arterioles
• have thin muscular walls, one or two layers of smooth muscle
• primary site of vascular resistance
1. resistance to flow
2. blood must overcome this for it to be pumped through circulatory system
12. Veins and venuoles
• returns deoxygenated blood to heart
• most veins have one way flaps (valves) 
• prevents blood from flowing backwards and pooling in our limbs due to gravity
• venule structure
• inner endothelium, middle layer of muscle and elastic tissue, and outer layer of fibrous connective tissue
• middle layer is poorly developed, so venules have thinner walls than arterioles
13. Capillaries
• smallest blood vessels (5-10 μm in diameter) 
• connects arterioles and venules
• important for exchange of oxygen, carbon dioxide, and others
• made of only a single layer of endothelium cells
• molecules (water, oxygen, etc) can pass through by diffusion
• waste products can diffuse back into blood and be carried away
• blood cells need to pass through single file
14. Roles of blood vessels
• not involved in regulating transport of blood
• vasodilation
• blood vessels in body become wider due to relaxation of smooth muscle in vessel wall
• reduces blood pressure
• nitric dioxide is a vasodilator
• vasoconstriction
• constricting of blood vessels
• contracts smooth muscle in vessel wall
• controlled by some hormones and neurotransmitters
1. vasocontrictors
• permeability
• important for release of nutrients to the tissue
• allows certain molecules and ions to pass through by diffusion
• permeability increases during an immune response
1. allows white blood cells and other substances to get to the site of injury
• oxygen is most critical nutrient being transported
1. hemoglobin has 95-100% oxygen
15. Blood pressure
• refers to the force exerted by circulating blood on walls of blood vessels
• usually means arterial pressure, the pressure in large arteries
• results from force that is applied to blood by contracting heart
• systolic arterial pressure is peak pressure in arteries
• arterial pressure measured by sphygmomanometer
• height of column of mercury indicated pressure of circulating blood
• even though modern machines don't use mercury anymore, the measurement is still in mmHg
• range
• systolic: less that 120 mmHg
• diastolic: less than 80 mmHg
• usually written as systolic/diastolic mmHg
• people who have systolic pressure around 115 mmHg instead of 120 mmHg have less health problems
• hypertension is a condition when a person's blood pressure is chronically high
• 140/90 or higher
16. Arterioles and blood pressure
• arterioles have greatest influence on local blood flow and overall blood pressure
• pulmonary and systemic circulations
• double circulatory system of blood flow refers to pulmonary circulation and systemic circulation in mammals
• pulmonary circulation
• carries oxygen-poor (deoxygenated) blood away from heart to lungs, and returns oxygenated blood back to heart
• leaves right ventricle through pulmonary arteries (only arteries that carry deoxygenated blood) 
• in lungs, red blood cells release carbon dioxide and pick up oxygen during respiration
• oxygenated blood leaves through pulmonary veins, and return it to the left side of the heart, completely pulmonary cycle
• oxygenated blood distributed to rest of body through systemic circulation
• systemic circulation
• portion of cardiovascular system that carries oxygenated blood away from heart and returns deoxygenated blood back to heart
• oxygenated blood from lungs leaves left ventricle from aorta, and distributed to the organs and tissues
• deoxygenated blood then collected by venules and returns to the right heart, completing the cycle. 
• re-oxygenated through pulmonary circulation
• coronary circulation
• heart's own blood supply
• heart muscle tissue is so thick that it needs blood vessels to deliver oxygen and nutrients deep within it
• vessels that deliver oxygen rich blood are cardiac veins
• portal venous system
• capillary be drains into another capillary bed through veins
• uncommon because capillary beds usually drain to heart
• considered venous because blood vessels that join the two capillary beds are either veins or venules
17. Lymphatic system
• complex network of lymph nodes, lymph ducts, lymphatic tissues, lymph capillaries, and lymph vessels throughout the whole body
• conduit for fluid called lymph
• also called secondary circulatory system
• three functions
• removal of excess fluid from body tissue
• absorption of fats (fatty acids or lipids) and transport of fats to cardiovascular system
• production of certain white blood cells, which help in immune response
• lymph: blood plasma that leaks from capillaries of cardiovascular system
• fills space between individual cells of tissue
• becomes part of interstitial fluid
• plasma forced out of capillaries and forced back in because of hydrostatic pressure
• increases volume of interstitial fluid when outside of blood capillaries
• most interstitial fluid returned to capillaries by osmosis
• excess fluid collected by lymphatic system into lymph capillaries
• processed by lymph nodes before going back to circulatory system
• within lymphatic system, fluid called lymph and same composition as original interstitial fluid
• fatty acids transportation
• also known as fats or lipids
• transported through cardiovascular system differently than other nutrients
• absorbed by cells in villi in small intestine
• forms a complex with protein molecules
• lipo-proteins called chylomicrons
• transported via lymphatic system and eventually gets processed by liver
18. Lymph nodes
• filters or traps for foreign particles and contain white blood cells
• human lymph noes
• bean-shaped
• few millimeters to 1-2 cm
• white blood cells located in honeycomb of lymph nodes
• microorganisms and tissue debris are removed from lymph in lymph nodes
• swell and feel sore when the body is infected because of increased production of white blood cells
• spleen and tonsils are large lymphoid organs
• serve similar functions to lymph nodes
• spleen filters blood cells rather than bacteria or viruses 
19. Lymphatic circulation
• not closed and has no central pump
• lymph movement occurs slowly because of peristalsis, valves, and squeezing action of skeletal muscles
• move in one direction only
• valves in lymph vessels
• movement depends on movement of skeletal muscles to squeeze the lymph through, especially near joints
• lymph transported to larger lymphatic vessels that drain into circulatory system at right and left subclavian veins
20. Homeostasis Imbalance of Lymphatic System
• disease: elephantiasis
• infection of lymphatic vessels cause thickening of skin and enlargement of underlying tissues
• commonly caused by infection of parasitic roundworms
• lymphedema causes abnormal swelling mostly in arms and legs
• occurs if lymphatic system is damaged or underdeveloped
• lymphoma (lymphatic cancer): cancer of lymphatic system
• cells divide too rapidly and grow without order or control
• lymphoma can start almost anywhere
21. Homeostasis Imbalance of Cardiovascular System
• cardiovascular disease (CVD) usually refers to diseases related to atherosclerosis
• inflammatory response in walls of arteries that causes swelling and buildup of plague
• plague is made of cell debris, cholesterol, fatty acids, calcium, and fibrous connective tissue that build up around an area of inflammation
• plague grows and stiffens, which narrows the arteries and reduces the flow of blood
22. Atherosclerosis
• begins in later childhood
• usually found in most major arteries
• causes: high-fat diet, high cholesterol, smoking, obesity,  and diabetes
• becomes a threat to health when plague buildup interferes with blood circulation in heart or brain
• blockage in heart can lead to heart attack
• blockage in brain can lead to stroke
23. Coronary heart disease
• result of buildup of plague within walls of coronary arteries
• most individuals have no symptoms until a heart attack happens
• symptom includes chest pain (angina pectoralis) happens during times of stress or physical exertion
• pain means heart muscle fibers need more than they are getting
• heart attack (myocardial in farction) occurs when buildup and blockage of a coronary artery by plague blocks the blood supply to a part of the heart
• also caused by small piece of plague that breaks away when a larger piece of plague breaks apart
• small piece called embolus can get stuck in a coronary blood vessel, causing embolism
• cardiac muscle cells that are deprived of oxygen for more than five minutes will die, and cannot be replaced
• coronary heart disease is leading cause of death in adults in the U.S. 
24. Stroke
• loss of brain function due to stoppage of blood to the brain
• can be caused by blood clot (thrombosis), free-floating object (embolism) or bleeding (hemorrhage) 
• risk factors
• advanced age
• high blood pressure
• previous stroke
• high cholesterol
• cigarette smoking
• reduction of blood pressure is important for reducing the risk of a stroke
25. Preventing cardiovascular diseases
• non-controllable risk factors
• age: older people are more likely to develop cardiovascular disease
• gender: men under 64 are more likely to die of CHD than women, but gender difference declines with age
• genetics: family history of cardiovascular disease increases risk
• controllable risk factors
• tobacco smoking: give up smoking
• diabetes: causes metabolism changes, which are risk factors
• high cholesterol levels: "bad cholesterol" high levels are a significant risk factor
• obesity: fat around the torso increases risk significantly
• high blood pressure: hypertension can cause atherosclerosis
• lack of physical activity: aerobic activity helps keeps the heart healthy
• poor eating habits: nutrient poor food can lead to high cholesterol and weight gain
26. Congenital heart defect
• problem with structure of heart, present at birth
• most common type of major birth defect
• most defects obstruct blood flow in the heart or vessels, or cause blood to flow in an abnormal pattern through the heart
• treatment includes medicine, surgery, and other medicinal procedures
• some mild defects may be repaired by body over time