Cardiac Structure and Function Flashcards
Right heart
- Pumps blood through lungs (pulmonary circulation)
- Uses unoxygenated blood
- Seperated from the left by the interatrial septum and interventricular septum
Left heart
Pumps blood through the systemic circulation
-Oxygenated blood
Circulatory system
-Right atrium-Tricuspid -RV-pulmonic valve-Pulmonary artery-lungs-arteries-arterioles-capillaries-venules-veins-back to 4 pulmonary veins (oxygenated)-LA-mitral valve-LV-aortic valve-Aorta-arteries of each organ-arterioles of each organ-capillaries of each organ-(unoxygenated)-venules of each organ-veins of each organ-vena cava
Heart wall
- 3 Layers (pericardium, myocardium, endocardium)
- Visceral and parietal layer are seperated by pericardial space that contains 10-30mL of fluid-area of cardiac tamponade
Pericardium
- Double walled membranous sac that encloses the heart
- Prevents displacement of the heart during gravitational acceleration and deceleration (can live without)
- Physical barrier that protects the heart against infection and inflammation
- Contains pain receptors and mechanoreceptors that can elicit reflex changes in BP and HR
Myocardium
-composed of cardiac muscle and anchored to the heart fibrous skeleton. Thickness varies from one chamber to the next, related to the amount of resistance it must overcome
Endocardium
internal lining of myocardium. It’s continuous w/ the endothelium that lines all of the arteries, veins, and capillaries of the body
RV
- Shaped like cresent triangle
- Overcome pressure of 15 mm Hg (mean PAP)
LV
- Larger than RV
- overcome pressure of 92 mm Hg (MAP)
Atrioventricular valves
- Tricuspid and bicuspid (mitral valves)
- Flows from low pressure to high
- Guarded by flaps of tissues called leaflets or cusps that’re attached to the papillary muscles by chordae tendinae
Semiulnar valves
- Pulmonic valve
- Aortic valve
- Opens when intraventricular pressure exceeds the aortic and pulmonary pressure
Papillary muscles
-extensions of the myocardium that pulls the cusps together and downward at the onset of ventricular contraction preventing them from backflowing into the atria
Phases of the cardiac cycle
- Atrial systole
- Ventricular systole
- Ventricular ejection (semiulnar valves open)
- Ventricular relaxation (closure of aortic valves)
- Ventricular filling (opening of mitral valves)
Diastole
-Myocardium relaxes and the chambers fill with blood
Systole
-Myocardium contracts forcing blood out of the ventricles
Cardiac metabolism
-Blood w/in the heart chambers doesn’t supply O2 or nutrients to the cells of the heart
Coronary vessels
- Right coronary artery (conus, right marginal branch, posterior descending)
- Left coronary artery
- Left main goes into the LAD (Left anterior descending artery, circumflex artery)
Coronary vessels cont
- Collateral arteries: connections between the branches of the same artery between the left and right
- They are important for ischemia-to provide nutrients if narrowing in one of the major arteries occurs
- Diabetes also creates smaller arteries-Difficult CABG cases
Conduction system
SA (sinoatrial node)-pacemaker of the heart. At the junction of the right atrium and SVC 60-100 bpm
- Atroventricular node (AV): 40-60bpm
- Bundle of HIS
- Right and left bundle branches
- Purkinje fibers 30-40 bpm
Electrocardiogram
- Pwave: atrial depolarization
- PR interval: time from the onset of atrial activation to the onset of ventricular activation
- QRS complex-sum of all ventricular depolarization
- ST interval: ventricular myocardium depolarized
- QT interval: Electrical systole of the ventricles
- Q-depolarization of the intraventricular septum
- R-depolarization of the main mass of the ventriculars
- S-depolarization of the purkinje fibers (base of the heart)
Adrenergic receptors
govern automatic (sympathetic) regulation of the HR, contractile force, and dilation or constriction of coronary arteries. -These specific receptors in the myocardium and coronary vessels determines the effects of neurotransmitters norepinephrine and epinephrine
B1 + epinephrine
-Impact rate and strength (mostly in the heart)
B2 + epinephrine
- Dilation of arterioles.
- are on the coronary arterioles and cause coronary dilation when stimulated by epinephrine this opposes alpha 1 plus norepinephrne vasoconstriction.
- B2 are in the lungs
A1 + norepinephrine
-Vasoconstriction
A2 + norepinephrine
-Inhibits norepinephrine, allowing vasodilation
Myocardial cells
- Nearly identical to skeletal muscle cells
- Intercalated disks
- Actin, myosin, and the troponin-tropomyosin complex (trop T, I, and C)
- Myocardial metabolism
Preload
- CVP or R atrial pressure
- pressure generated in the ventricles at the end of diastole, depends on the amount of the blood in the ventricle which is directly related to blood in the atria
Afterload
- SVR
- Resistance to ejection of the blood from the ventricle. Afterload depends on pressure in the aorta
Ejection fraction
SV/EDV
EDV-ESV=Stroke volume (blood moved with each beat)
Baroreceptors (neural reflexes)
facilitates both pressure and HR (if BP decreases, HR increases)
Norepinephrine
increases HR and enhances myocardial contraction and constricts blood vessels
Epi
Increases myocardial contractility
hormones
- Thyroid hormones can increase cardiac output
- Some adenocortical hormones like hydrocortisone can potentiate the effects of catecholomines (thus stress dose steroids used in vasopressor refractory hypotension)
Bainbridge (neural reflexes)
-causes changes in HR w/ response to volume receptors in the atria that are innervated by the vagus nerves
Cardiac output
-Volume of blood flowing through either the systemic or pulmonary circuit in liters per minute
Myocardial contractility
- Stroke volume
- Inotropic agents
- O2 and carbon dioxide levels
Structure of blood vessels
-Lumen, tunica intima, tunica media, tunica externa (adventitia)
Tunica media
of arteries close to the heart contains a greater proportion of elastic fibers
Blood flow through veins
assisted by the contraction of skeletal muscles (muscle pump) and backflow in the lower body is prevented by one way valves particularly in the deep veins of the legs-DVT prophylaxis is important
Factors affecting blood flow
Arterial chemoreceptors-specialized areas w/in the medulla oblongata, aorta and carotid arteries that are sensitive to concentrations of O2, carbon dioxide, and hydrogen ions within the blood
- For example decrease arterial oxygen concentration or pH causes a reflexive increase in BP
- Increased CO2 causes decreased BP
Hormones affecting blood flow
-Epinephrine, norepinephrine, antidiuretic hormone, renin-angiotensin-aldosterone system, natriuetic peptides, adrenomedullin, insulin, and others
Lymphatic system
special vascular system that picks up excess fluid and returns it to the blood stream
-Tonsils, cervical lymph nodes, right lymphatic duct, red bone marrow, inguinal lymph nodes, spleen, thoracic duct, axillary lymph nodes, thymus gland, peyers patches in intestinal wall
Vasoconstrictor hormones
Epinephrine, norepinephrine, angiotensin 2, vasopressin
Vasodilator hormones
Natriuretic peptides
Norepinephrine
Released by adrenal medulla. Acts mainly as neurotransmitter. Increases HR, enhances contractility, and constricts blood vessels
Epinephrine
Dilated blood vessels of the liver, skeletal muscles, and increase in HR and contractility, and vasoconstriction
Thyroid hormone and growth hormones
Decrease in these can result in bradycardia, reduced CO and low BP. Thyroid hormone triiodothyronine cause increases in HR, contractility, and increased CO and decreased SVR
Vasopressin and aldosterone
Effect BP by increasing fluid reabsorption and blood volume
Lymphatic nodes, lymphatic pump, and lymphatic circulation
- plasma, interstitial fluid, and lymph are intimately connected
- when blood leaves the capillary it becomes interstitial fluid (or vice versa)
- Interstitial fluid also enter the lymphatic capillary and becomes lymph
- How body filters out waste and protects against pathogens
Lymph nodes
- lymph nodes are located along lymphatic vessels
- filter lymph traveling through vessels
- filtered several times
- several lymphatic vessels enter each lymph node (afferent lymphatic vessels)
- fewer lymphatic vessels exit the lymph node (efferent)
- filters more slowly through the lymph nodes b/c more afferent vessels-more filtered
Lymph
- Flow of lymph only goes in one direction, from vessels towards blood
- main lymphatic trunks (right lymphatic duct, thoracic duct)
- Right lymphatic duct drains from upper right quadrant of body
- Thoracic duct drains lymph from rest of the body
- as soon as it enter the blood-now plasma
Lymphatic pump
- skeletal muscle contraction help lymph flow-lymphatic pump
- lymphatic vessels have valves to prevent backflow
Lymphocytes
- Some mature in bone marrow and become B lymphocytes
- Some mature in thymus gland becoming T lymphocytes
- Other sites are spleen, appendix, tonsils, peyer patches in small intestine
Capillaries
site of oxygen, CO2, nutrient and waste exchange
arterioles
-smallest arteries connecting to capillaries
-
venules
tiny veins that connect capillaries to veins
Coronary arteries
- oxygenated blood enters the coronary arteries through openings w/in the semiulnar valves at the entrance to the aorta (diastole)
- deoxyganted blood from the coronary veins enters the right atrium through coronary sinus
Contraction process and cross bridges
- cross bridges between actin and myosin enable contraction to occur
- Ca and its interaction w/ the troponin complex facilitate the contraction process.
- W/ troponin release of Ca, myocardial relaxation begins
Layers of the vessels
- tunica media of arteries close to the heart contains a greater portion of elastic fibers b/c these arteries must distend and recoil during cardiac cycle
- distributing arteries farther from the heart contain more smooth muscle fibers b/c they must be able to constrict and dilate to control BP and volume
