LO 12/13/14 Flashcards
Describe the structure and position of the heart
- Triangular-shaped organ
- Fist-sized
- Hollow; 4 chambers
- Located in mediastinum
- Two thirds lies to the left of the body’s midline; one third to the right
- Apex lies on diaphragm
- Lies between the sternum and the thoracic vertebrae
- Positioning makes CPR possible
Describe the atrium/atria
- Two upper chambers
- Right and left ‘receiving’ chambers (low pressure) – blood from body returns to atriums via veins
- Smaller and thinner-walled than ventricles
Describe the ventricles
- Two lower chambers
- Right and left ‘discharging’ chambers
- Blood leaves the heart through the ventricles via arteries
Describe the myocardium
- cardiac muscle tissue that makes up wall of each heart chamber
- Atrial septum divides atria
- Ventricular septum divides ventricles
Describe the endocardium
- thin layer of very smooth tissue lining each heart chamber
- Endocarditis = inflammation of endocardium; can promote formation of blood clots
Describe the pericardium
- Covering ‘sac’
- Two-layered fibrous sac with a lubricated space between the two layers to allow them to slide against each other without friction as heart beats
- Inner layer = visceral pericardium, or epicardium. Completely covers heart
- Outer layer = parietal pericardium. Loose sac around heart
- Pericarditis = painful inflammation of pericardium
________ is the contraction of the heart, while ________ is the relaxation of the heart
- Systole
- Diastole
Provide the general direction of blood flow in the heart
Atria receive blood 🡪 atria contract 🡪
blood forced into ventricles 🡪
ventricles fill 🡪 blood forced out of heart
Direction of blood is controlled by valves
Venous blood 🡪
RA (thru sup. & inf. vena cavae) 🡪
tricuspid AV valve into RV 🡪
thru pulmonary SL valve 🡪
pulmonary artery 🡪
lungs 🡪 pulmonary veins 🡪
LA 🡪
bicuspid/mitral AV valve 🡪
LV 🡪
aortic SL valve 🡪
aorta 🡪
arterial blood distributed throughout body
What are 4 valves in the heart that prevent the back flow of blood?
- 2 atrioventricular valves (AV valves)
- 2 semilunar valves (SL valves)
Describe the atrioventricular valves (AV valves)
- Separate atria from ventricles
- Tricuspid valve: on right side of heart
- Bicuspid or mitral valve: on left side of heart
- Chordae tendinae attach AV valves to wall of heart
Describe the semilunar valves (SL valves)
- Pulmonary SL valve - Between right ventricle and pulmonary artery
- Aortic SL valve - Between left ventricle and aorta
Describe the lub dup sounds in each heartbeat cycle
- First (lub) sound (longest): caused by the vibration & sudden closure of AV valves during contraction of the ventricles
- Second (dup) sound: caused by the closure of the semilunar valves during relaxation of the ventricles
How does the heart act as 2 different pumps?
- RA and RV perform different functions from the LA and LV
- With each heart beat, the LA and RA contract simultaneously to fill the LV and RV with blood = atrial systole
- Next, the LV and RV contract simultaneously = ventricular systole
Describe coronary circulation (blood supply to the heart)
- Constantly working cardiac muscle (myocardium) needs a constant supply of oxygen and nutrient rich blood
- The blood that supplies oxygen and nutrients to the myocardium, flows through the right and left coronary arteries (very first branches of the aorta)
- Blockage of blood flow through the coronary arteries is called myocardial infarction (MI), or heart attack
Describe angina pectoris
Chest pain caused by inadequate oxygen to the heart
Describe coronary bypass surgery
Veins from other parts of the body are used to bypass blockages in coronary arteries
Describe the cardiac cycle
- Heartbeat is regular and rhythmic—each complete beat is called a cardiac cycle
- Each cycle (beat) is approx. 0.8 sec long
- Average = 72 beats/minute, normal 60-100 bpm
- Each cycle is subdivided into systole (contraction phase/lub) and diastole (relaxation phase/dup)
The _________ is the amount of blood that one ventricle ejects with each beat
Stroke volume
The _________ is the amount of blood that one ventricle ejects each minute (ave = 5L at rest)
Cardiac output
What 5 specialized structures embedded in the wall of the heart help generate strong impulses and conduct them to the various regions of the heart wall?
- Intercalated disks
- Sinoatrial node (SA node)
- Atrioventricular node (AV node)
- AV bundle (bundle of His)
- Purkinje fibres
Describe Intercalated disks
Special electrical ‘connections’ between cardiac muscle fibers allowing cardiac muscle to contract as a whole, at about the same time
Describe the Sinoatrial (SA) node
- the pacemaker – where impulse starts
- located in the wall of the RA near the opening of the superior vena cava
Describe the AV (atrioventricular) node
located in the RA along the lower part of the interatrial septum
Describe the AV bundle (bundle of His)
located in the septum of the ventricle
Describe the Purkinje fibers
located in the walls of the ventricles
Describe electrocardiograms (ECGs)
- The electrical impulses of the heart’s conduction system can be recorded and is called an electrocardiogram, or ECG
- A normal ECG has three deflections or waves called the P wave, the QRS complex, and the T wave
- P wave: Associated with depolarization (triggers contraction) of the atria
- QRS complex: Associated with depolarization of the ventricles
- T wave: Associated with repolarization (just before relaxation phase) of the ventricles
- No visible recording of repolarization of atria (overshadowed by large QRS complex)
- Damage to heart muscle/CVD will change ECG
List the types of blood vessels
- Arteries
- Veins
- Capillaries
Describe arteries
- Carry blood away from the heart
- Aorta is largest one 🡪 arteries 🡪 arterioles
Describe veins
- Carry blood toward the heart
- Superior and inferior vena cava are the largest ones 🡪 venules 🡪 veins 🡪 vena cava
Describe capillaries
- Microscopic blood vessels
- Site of gas and nutrient exchange between blood & tissue fluid around cells (capillary beds)
- Connect arterioles and venules
Describe the layers of arteries
- Tunica intima (inner layer) - Single layer of squamous epithelial cells (endothelium – lines entire surface of circulatory system)
- Tunica media (middle layer) - Smooth muscle with a thin layer of elastic tissue; Thicker in arteries than veins (to withstand systole); Important in BP regulation (smooth muscle – ANS)
- Tunica adventitia/externa (outer layer) - Thin layer of elastic tissue; Reinforces wall of vessel to withstand pressure
Describe the layers of veins
- Tunica intima (inner layer) - Contain one-way valves to prevent backflow of blood (not found in arteries)
- Tunica media (middle layer) - Smooth muscle with a thin layer of elastic tissue; Thinner in veins than arteries (lower blood pressure in veins)
- Tunica adventitia/externa (outer layer) - Heavy layer in many veins to prevent collapse of the blood vessel from injury due to its superficial location in the body to the skin
Describe the layers of capillaries (connect venules and arterioles)
- Only layer is the tunica intima
- Extremely thin
- Flat epithelial cells
- Allows substances to quickly pass through wall
Describe the function of Arteries/arterioles
- move blood from heart to capillaries
- distribution of nutrients, gases, etc., with movement of blood under high pressure
- assist in maintaining the arterial blood pressure by constricting/dilating
Describe the function of Veins/venules
- collect blood from capillaries for return to the heart
- low-pressure vessels, so can act as reservoirs - e.g. can expand to hold a larger amount of blood
Describe the function of Capillaries
Serve as exchange vessels for nutrients, wastes, and fluids for every body cell
What are the 4 types of circulation?
- Systemic Circulation
- Pulmonary Circulation
- Hepatic Portal Circulation
- Fetal Circulation
Describe Systemic Circulation
- Carries blood throughout body
LV
Aorta
Smaller arteries
Arterioles
Capillaries
Venules
Veins
Venae cavae
RA
Describe Pulmonary Circulation
- Carries blood to/from lungs
- Arteries deliver deoxygenated blood to lungs for gas exchange
RV
Pulmonary arteries
Pulmonary arterioles
Lungs (capillaries)
Pulmonary venules
Pulmonary veins
LA
Describe Hepatic Portal Circulation
- Unique blood route through the liver
- Blood from veins from spleen, stomach, pancreas, gallbladder and intestines does not go directly into inferior vena cava
- Blood gets sent to the liver via hepatic portal vein
- Blood passes through liver before re-entering regular venous return to heart via hepatic veins that drain into inferior vena cava
- Venous blood (that would normally be sent back to the heart) is sent through a second capillary bed in the liver before returning to ‘normal’ pathway of blood returning to heart
- hepatic portal vein exists between two capillary beds - one capillary bed is in the digestive organ; one capillary bed is in the liver
What does hepatic circulation assist with?
- homeostasis of blood glucose levels - liver cells store excess glucose as glycogen
- detoxification
Describe fetal circulation
- Refers to circulation before birth
- Modifications required for fetus to efficiently secure oxygen and nutrients from maternal blood instead of its own lungs and organs which aren’t fully developed or functional
- Unique structures of fetal circulation include - Placenta, Umbilical cord, ductus venosus, ductus arteriosus, foramen ovale
Describe the placenta
- Anchors fetus to uterus
- Site of exchange of oxygen, nutrients, and waste products between maternal and fetal blood
Describe the umbilical cord
- Connects fetus to placenta
- Contains 3 blood vessels - 2 small umbilical arteries that carry oxygen-poor blood from the developing fetus to the placenta; 1 larger umbilical vein that carries oxygen-rich blood from the placenta to the fetus
Describe the ductus venosus
- A continuation of the umbilical vein
- Shunts blood returning from the placenta to the fetus past the fetus’ immature liver into the inferior vena cava
Describe the ductus arteriosus
- Connects the aorta and pulmonary artery
- Allows most blood to bypass the fetus’ underdeveloped lungs
Describe the foramen ovale
- Shunts blood from the RA directly into the LA
- Allows most of the blood to bypass the fetus’ underdeveloped lungs
Describe blood pressure
- BP is the push or force of blood in the blood vessels
- Highest in arteries, lowest in veins
- Blood pressure gradient - causes blood to circulate, as liquids can flow only from areas of higher pressure to lower pressure
- No pressure gradient, no circulation, no life!
What are the main factors that influence blood pressure?
- Blood volume
- Strength of heart contractions
- Heart Rate
- Blood viscosity
- Resistance to Blood Flow
Describe blood volume
- the higher the volume, the higher the BP and vice versa
- diameter of arterioles (under ANS control) determines how much blood goes from arteries to arterioles
Describe the strength of heart contractions
- determines the volume of blood that goes into the blood vessels (recall the definition of stroke volume = the volume of blood pumped out each time the left ventricle contracts)
- stronger contraction 🡪 more blood is pumped out in to arteries and vice versa
Describe heart rate
- can affect BP depending on how stroke volume changes (e.g. when contractions occur faster, the ventricle may not have time to completely ‘refill’ with blood)
Describe blood viscosity
- the thicker blood is, the higher the BP will be and vice versa
- circumstances that may affect blood viscosity include - fluid moving into the blood from interstitial fluid in the case of a hemorrhage; transfusion of whole blood or plasma; polycythemia
Describe resistance to blood flow
- Any force that acts against the flow of blood = peripheral resistance, e.g. Blood viscosity
- Tension in the muscles of the blood vessel walls (if muscles are relaxed, resistance is low and vice-versa)
What states, demographic factors, disease states, etc can impact blood pressure?
- Strenuous exercise, stress 🡪 increased BP
- Fitness level
- Age, gender, race, weight
- Stress, emotions
- Hormones
- Diseases (e.g. diabetes, CVD)
- Tobacco, alcohol, caffeine and other drugs
Describe hypertension
- higher than normal blood pressure reading
- if BP is too high, it can cause the rupture of blood vessels
- ’silent killer’ – no symptoms
Describe hypotension
- lower than normal blood pressure
- if BP is too low, blood may stop flowing
Describe central venous pressure
- The venous blood pressure within the right atrium (close to zero!)
- Influences the pressure that exists in the large peripheral veins
- Strong heart beat 🡪 blood is entering and exiting the heart effectively 🡪 low central venous pressure
- Weak heart beat 🡪flow of blood into the right atrium will be slowed 🡪 increased/high central venous pressure
What are mechanisms that help keep venous blood moving through circulatory system 🡪 RA
- Continued beating of the heart
- Adequate BP in the arteries to push blood to and through the veins
- Semilunar valves in veins that ensure blood flow in one direction (towards the heart)
- Contraction of skeletal muscles – produces a ‘pumping’ action which squeezes veins
- Changing pressures in the chest cavity during breathing also produces a kind of ‘pumping’ action in the veins in the thorax
Define pulse
- alternate expansion and recoiling of an arterial vessel wall
- Provides info re: rate, strength and rhythm of heart beat
What are the 9 major pulse points?
- Superficial temporal artery
- Facial artery
- Carotid artery
- Axillary artery
- Brachial artery
- Radial artery
- Femoral artery
- Popliteal (posterior to patella)
- Dorsalis pedis
