Cardio Flashcards
Major borders and surfaces of the heart
Right border = RA
Left border = LA and LV
Inferior border = RV and some LV
RV forms most of the anterior surface of the heart
What do the two appendages look like?
Right atrial appendage is like snoopy’s nose, left is longer and skinnier like south america
Relative position of pulmonary artery and aorta
Pulmonary artery is anterior to aorta, to left shoulder,
Ascending aorta is posterior to PA, to right shoulder
Angle between the two is 60-90 degrees
Right coronary artery (where does it come from, where does it lie, what does it give rise to)
Right coronary artery arises from right sinus of Valsalva (aortic sinus)
Courses between RA and RV in atrioventricular groove
Gives rise to RA branch, acute marginal (feed RV) and usually the posterior interventricular artery
Left coronary artery (where does it come from, and what does it divide into
Left coronary artery arises from left sinus of Valsalva
Has a short segment (left main) then divides into circumflex and left anterior descending artery
Circumflex (where, and what does it give rise to)
In left atrioventricular groove
Gives rise to obtuse marginal branches that feed lateral LV wall
Left anterior descending artery (what does it do and where does it arise from)
Feeds septum and LV free wall
Gives rise to diagonals and septal branches
Where do the majority of the cardiac veins drain to? Where is it?
The coronary sinus (great cardiac vein) in posterior AV groove
Right atrium
Smooth and trabeculated walls separated by crista terminalis
Superior and inferior vena cava drain into smooth walled portion of RA
Fossa Ovalis is formed from downward migration of septum secundum and upward migration of septum primum
Associated with tricuspid valve
Upper chamber
2 mm thick
Conducts blood from systemic to RV
Coronary sinus empties here
Epicardium rich in ganglia
Myocytes smaller than ventricles
Electron dense granules store atrial naturietic peptide
What two things does the LA not have that the RA does?
No crista terminals or pectinate muscles
Right ventricle
L shaped (croissant) Thin walled Highly trabeculated Pumps through pulmonary valve At apex of heart Anterior most structure Inflow portion, apex, outflow portion (infundibulum or conus) Myocardium 5 mm thick Membranous septum contains conduction system Low pressure (25-30mmHg)
Left Ventricle
Cone shaped (donut) Thick walled No trabeculations Pumps through aortic valve high pressure Inflow/septal/outflow portions 15 mm thick Conducts blood from LV to aorta
What 5 things do the AV valves depend on for proper function?
Hinge lines Valve tissue Chordae Papillary muscles Ventricular wall function
Semilunar valves
Aortic and pulmonary
3 leaflets
Suspended from the pulmonary trunk and aortic root
Scalloped (commissures/hinge lines)
Competency dependent on attachments and elastic/collagenous nature of the leaftet tissue as well as the dimensions of the root and trunk
No chordae!
Relative amounts and cell numbers of endothelial cells and cardiomyocytes
Myocytes: 25% of total cell number, 90% of cell volume
Endothelial cells: 75% cell number, negligible volume
What is the pericardium? What is it made of?
Fibrous sac surrounding the heart Reflections from great vessels and veins Serous component over surface of heart Fibrous joins serous at reflections. Collagen rich, inelastic!
Beck’s triad
Hypotension, muffled heart sounds, distended jugular veins
Signs associated with acute cardiac tamponade.
50cc of straw coloured fluid is normal, but sudden increase to 250cc causes tamponade
Pericarditis
Really thick pericardium, calcifies and restricts the heart even without fluid
Fibrous skeleton
Base of the heart, dense collagenous tissue with elastin
Makes up AV valve rings and aortic annulus, extends to pulmonary trunk via conal ligament – point of attachment for valve leaflets and myocardium
Separates the atrial and ventricular chambers, separates the right and left ventricles (membranous septum)
AV conduction bundle embedded
Provides rigidity to prevent dilation of valves
Why is electrical isolation important between atria and ventricles?
Electrical isolation is important so that the atria and ventricles keep separated
Muscle cells have gap junctions that can share action potentials but they stop at the fibrous skeleton
So the entire heart doesn’t contract at once
Bundle of His is the only electrical connection between A/V
Epicardium
Analogue of vascular adventitia
Serous pericardium
Contains coronary arteries and veins, fat, nerves, fibroblasts and macrophages
Myocardium
Analogue of vascular media
Contractile myocytes
Also collagen, blood vessels, and elastin
Bundles of cardiac muscle separated by fibrous bands
Endocardium
Analogue of vascular intima Endothelial cells and connective tissue Continuous with intima of vessels Anticoagulant surface Has 3 major components
3 major components of the endocardium
Endothelium (single layer of squamous endothelial cells held together by tight junctions, also has gap junctions for communication)
Continuous basal lamina
Subendocardium (layer of loose connective tissue – binds the endocardium to myocardium)
5 components of cardiac myocytes
Cell membrane (sarcolemma and T tubules) responsible for impulse conduction – form gap junctions between adjacent cells, intercalated disks join adjacent myocytes both mechanically and ionically, myocardium is a functional syncytium (electrically unified)
Sarcoplasmic reticulum: Ca2+ reservoir, release of Ca into cytosol as a result of action potential causes contraction
Contractile elements: action, myosin, troponin, and tropomyosin – contraction is the net effect of sliding actin and myosin toward to center of the sarcomere – increased stretch results in longer pull (Starling’s)
Mitochondria: energy generation through aerobic metabolism, heart muscle almost exclusively aerobic, mitochondria make up 23% of myocyte volume (2% in skeletal)
Nucleus: very large
Ventricular cardiac muscle
Forms complex layers of cells wound helically around the ventricular cavity
Atrial cardiac muscle
Muscles in outer myocardium form a helical pattern around the chambers (like ventricles) Atrial cells are smaller Less T tubules More gap junctions Conduct impulses faster Contract more rhythmically Have many granules
Left atrium
Receives blood from pulmonary veins and delivers to LV Smooth throughout Auricular appendage (South America)
Aortic valve
Located in aortic root
Commisures are high points and cusp nadirs the low points
Ring of suspension is annulus
Left/right/non leaflets
3 Layers of aortic valve
Fibrosa (collagen rich, extends to free edge and coapting surface, gives strength to tissue)
Spongiosa (proteoglycan and GAG rich, collagen and fibroblasts)
Ventricularis (LV side, elastin rich, acts as shock absorber, allows leaflets to stretch and coapt under pressure load and spring out of the way during ejection)
Pulmonary valve
Resides in pulmonary trunk, anterior and superior to aortic valve
Mitral valve
Regulates flow between LA and LV (only 2 leaflets)
Leaflets attach to the mitral annulus (junction of the left atrium and LV made by the cardiac skeleton)
Leaflet edges tethered by chordae tendinae attached to papillary muscles
Competency based on annular dimension, structural integrity of leaflets (pliable, elastic, strength), structural integrity of chordae, function and dimensions of ventricle
4 layers of the mitral valve
Fibrosa (collagen rich, extends to chordae and tips of papillary muscles)
Spongiosa (atrial side, GAG and proteoglycan rich)
Ventricularis (ventricular side, elastin rich and endothelialized)
Auricularis (EC layer on atrial side)
Tricuspid valve
Analogous histological structure
Lower pressure
Thinner leaflets, and chordae and papillary muscles
Tunica adventitia
Outermost layer
Mainly loose connective tissue with type 1 collagen and elastic fibers that anchor vessel
Thickest layer in veins
Contains vasa vasorum
Tunica media
Middle layer (most variable in size/structure)
Contains smooth muscle, collagen fibers, reticular fibers, and elastic tissue (more in arteries, less in veins)
Large layer in most arteries
Nitric oxide versus endothelin
Nitric oxide dilates coronary arteries, endothelin constricts them
Endothelium
Bound together by junctional complexes
Can be activated by cytokines to express cell adhesion molecules to allow WBC to stick
Secretions to maintain tone and prevent clotting
SA node
Initiates the heart beat Highest intrinsic heart rate Junction of SVC and RAA Has leakiest phase 4 60-100 bpm
4 mediators released from endothelial cells that are elaborate anticoagulant, antithrombotic, and fibriolytic molecules
Prostacyclins
Thrombomodulin
Heparans
Plasminogen activator
3 pro-thrombotic molecules
Von willebrands factor
Tissue factor
Plasminogen activator inhibitor
Agents each responsible for
- Vasoconstriction (3)
- Vasodilation (2)
- Endothelin, angiotensin converting enzyme, thromboxane
2. Nitric oxide, prostacylin
3 stimulators and 2 inhibitors of cell growth
Stimulators: 1. PDGF 2. FGF 3. VEGF Inhibitors: 1. Heparin 2. TGF beta
Large elastic arteries
Aorta, brachiocephalic, carotid, subclavian, iliac, pulmonary arteries and larger branches
Thick vessels, with cells and connective tissue organized in lamella
Too thick for oxygen diffusion, so need vasa vasorum
Elastin dominates in media, allowing for expansion in systole
Muscular arteries
Intima thinner than elastic arteries
Internal and external elastic lamina well defined
Media has fewer and finer elastin fibers, lamella is defined but occasionally discontinuous, VSMC major component (75% mass)
Adventitial thickness/strength is variable
Ex: coronaries, renal arteries, femorals and distributive arteries of lower extremities, axillaries and distributive arteries of upper extremity.
Aorta as a secondary pump
Elastic artery, so it can expand with systole and become a pressure reservoir
Aorta
Arises from LV
Root gives rise to coronary arteries
Arch to head and upper extremity vessels (variants common), descending to paired intercostal arteries (role in coarctation)
Type A dissection
Ascending (40% mortality without surgery, 10% with operation)
Type B dissection
Descending (20% mortality, better than with surgery)
Axillary artery
Muscular artery in upper limb
Begins at lateral border of first rib to teres major
Multiple branches to shoulder and chest wall.
Brachial artery
Muscular artery in upper limb
Teres major to antecubital foss
Branches to elbow and adjacent forearm musculature
Radial and ulnar arteries supply forearm musculature, deep and superficial palmar arches supply hand and digits
Iliac artery (3 parts)
Common iliac: paired arteries arise at the terminus of the abdominal aorta
External iliac: common iliac branch that courses along psoas muscle anterior and inferior to the inguinal ligament
Internal iliac arteries: arise at sacroiliac joint: courses postero-inferior to external iliac giving rise to branches that supply the pelvic viscera and medial thigh
NAVL
Lateral to medial it goes nerve, artery, vein, lymph
Relative position of femoral artery
As external iliac crosses the inguinal ligament it becomes femoral artery
Midway between pubic tubercule and anterior superior iliac spine
Popliteal artery
As superficial femoral artery emerges into posterior knee, from adductor magnus muscle becomes popliteal artery
Gives 5 geniculate branches to knee, travels in interchondylar fossa, divides at popliteal muscle into anterior and posterior tibial artery
Anterior tibial artery
Popliteal artery as it emerges from popliteus muscle changes name to anterior tibial
Courses in anterior compartment of lower leg
Gives posterior tibial artery, dorsalis pedis in foot, supplies tibia and adjacent muscles
Posterior tibial artery
Arises near origin of anterior tibial artery and courses down behind the tibia in the posterolateral leg
Gives peroneal artery
Terminates behind the malleolus
Supplies tibia and adjacent muscles
Structure and function of arterioles
Arterioles (20-100 um diameter): provide blood flow regulation via medial smooth muscle contraction, regulates relative blood flow to capillary beds.
Intima is very thin, media is 1-6 layers of smooth muscle, adventitia comparable in thickness to media, merges with adjacent connective tissue
Provide majority of flow resistance
Capillary structure/function
Diameter of 8-30 um – collectively represent a huge cross sectional area in body
Endothelial cell lining but no media or elastin – myosin containing pericytes provide structural support
Allow rapid exchange of oxygen and nutrients via diffusion
Flow is very slow
Veins versus arteries
Veins: intima is narrow and lining is hard to see. Sparse elastin with only incomplete elastic lamina. Media is thinner than in arteries, and smooth muscle cells are less and less organized. Adventitia: only in the largest veins
Starling’s Law
With more venous return to the heart, the heart pumps more
Increased muscular stretch results in increased contraction
Operates at the level of the sarcomere
No change in arterial pressure or heart rate
Can over stretch
Autonomic Control
Heart has abundant symp and parasymp innervation
Sympathetic drive increases heart rate, strength of contraction, controls basal firing of sympathetic fibers, and is mediated by beta-adrenoreceptors
Parasympathetic tone can lead to bradycardia, and decreased force of contraction
Baroreceptor reflex
Stretch receptors widely distributed in vascular system (especially carotid sinus, aortic arch)
Stimulate CNS
Increased pressure results in inhibition of vasoconstrictor center and excitation of vagal center
With standing, opposite effect
Vasodilation of veins and arterioles
Decreased heart rate and contractility
Senses increased blood pressure, so it dilates veins and arterioles, as well as decreasing heart rate and contractility
What happens in exercise
20-fold flow difference between rest and exercise in skeletal muscle beds (vasodilation – arteriolar and EC regulated)
Increased return of blood (frank-starling)
Increases CNS activity results in vasoconstrictor center activation
Fight or flight response
Norepinephrine/epinephrine: results in humoral release and increased sympathetic tone. Humoral release has same effect as local sympathetic innervation (constricts VSM, increases HR and FVC)
3 types of capillaries
Continuous: complete EC lining
Fenestrated: EC gaps allowing macromolecular passage (ex: glomerulus)
Discontinuous: larger gaps in EC (ex: liver)
What sized veins do not have valves?
Large veins
What is dominance determined by?
Which artery gives rise to the posterior descending artery
If its the right coronary artery, right dominant
If its the circumflex, left dominant
If both, co dominant
7 Endothelial Cell functions
- Permeability barrier
- Antioagulant, antithrombotic, fibrinolytic
- Pro-thrombotic
- Synthesize matrix molecules
- Modulate blood flow
- Regulation of cell growth
- Regulation of inflammation and immunity
