Anatomy and Histology Flashcards
What’s the difference between pericardium and pleura?
Define the two layers of the pericardium
- Pericardium is not attached to the rib cage (pleura is)
- Visceral pericardium = epicardium = serous layer covering the fat/coronary vessels
- Parietal pericardium
- Has two laters (unlike parietal pleura):
- Fibrous pericardium (outer fibrous layer)
- Inner serous layer
- Has two laters (unlike parietal pleura):
Cardiac tamponade
Describes the condition of when the sinus space between parietal and visceral pericardium is too large, causing compression of heart and restriction of filling with blood
- Can be caused by effusion in pericardial sac
- Can affect heart rhythm
Describes the heart’s anatomical position
- Between ribs 2-6, from sternal angle to xiphoid process
- Tocuhes right middle lobe and lingula of left upper lobe
- Apex points anteriorly and to the left
- RV is anterior
- RA and LV are left and right margins (respectively)
- LA is posterior and anchored by pulmonary veins
Where do you place the stethoscope to hear valvular sounds?
Describe the right atrium
- Auricle (ear-like appendage)
- Pectinate muscle and smooth posterior wall separated by crista terminalis
- Fossa ovalis
- Coronary sinus opening
Crista terminalis
- Thick portion of heart muscle that contains pacemaker tissue and SA node
Describe the right ventricle
- Conus arteriosus - smooth wall that tapers into pulmonary semilunar valve
- Membraneous and muscular interventricular septum
- Trabeculae carnae
- Papillary muscles
- Septomarginal trabeculae (Ex. Moderator Band)
Describe the left atrium
- Similar to right atrium: Auricel, pectinate muscles
- Usually receives two left and two right pulmonary veins
Describe the left ventricle
- Thick walled (3x thicker than RV)
- Aortic vestibule (conus arteriosus equivalent) tapers to aortic valve
- Membraneous and muscular interventricular septum
- Trabeculae carnase
- Papillary muscles
- Septomarginal trabeculae (Ex. moderator band)
AV valves
- Tricuspid and Mitral (Bicuspid)
- Papillary muscles + chordae tendinae
- Close during S1, ventricular systole
Semilunar valves
- Pulmonary and Aortic
- Close during S2, ventricular diastole
Myocardium arrangement in ventricular walls and how does this relate to its function (contraction, pressures, and flow)?
- Muscle layers arranged in spiral fashion
- Contraction proceeds from the apex upwards, squeezing blood toward AV valves
- Attaches to fibrous skeleton surrounding and interconnecting the heart valves providing support
- Insulates/separates atrial and ventricular electrical activity
Left vs right coronary artery branches and supply
- LCA
- LAD (anterior interventricular), circumflex, and left marginal branches
- Most of LA and LV, anterior part of RV, anterior 2/3 of IV septum, and AV bundle branches in the septum
- RCA
- Posterior interventricular, marginal branch, and right artrial “nodal” branch
- Most of RA and RV, posterior part of LV, posterior 1/3 of IV septum, and SA/AV nodes (majority population)
Coronary sinus
- Collection vein where all the coronary veins converge
- Drains directly into the RA
Pathway of the Conduction System
- SA node –> 2 atrial internodal pathways –> AV node –> AV bundle (of His), L+R bundle (septal) branches –> Purkinje fibers up ventricular walls
Specify neurons that innervate the heart
- Sympathetic
- Stellate ganglion
- Cardiopulm splanchnic nerves –> lower cervical and upper thoracic levels of sympathetic trunk –> cardiac plexus
- Parasympathetic
- Vagus nerve (ACh = postsynaptic parasympathetic neurotransmitter that slows HR via vagus nerve) –> links with postsynapctic sympathetics and visceral sensory fibers to cardiac plexus
- Visceral sensory
- Cardiopulm splanchnic nerves –> sympathetic trunk –> dorsal root –> spinal cord
- Angina and referred pain (via T1)
Azygos system
- System of veins that receives blood from the intercostal veins
- Left posterior intercostal veins drain into the hemiazygos veins that pass over vertebral bodies to join the azygos vein.
- Azygos vein arches over the root of the right lung to empty all intercostal blood into the superior vena cava
What are examples in the circulation of resistances in series?
- Renal circulation (Kidneys)
- Glomerular and peritubular are the two capillary beds in series
- Portal circulation (Liver)
- Splenic to hepatic
- Mesenteric (intestines) to hepatic
Which organ gets dual circulation and from where?
- Lungs
- Pulmonary circulation and bronchial circulation
What’s the main vessel that provides systemic vasacular resistance?
- Arterioles
Layers of blood vessels (in to out)
- Tunica intima (endothelium)
- Internal elastic tissue
- Tunica media (smooth muscle)
- External eleastic tissue
- Tunica adventitia (fibrous connective tissue)
How do the parametes of length, radius, and viscosity affect resistance?
- Length directly proportional to resistance
- Radius indirectly proportional to resistance
- Viscosity directly proportional to resistance
Reynolds number
(Equation and Application)
N = p (density) * d (diameter) * v (velocity) / n (viscosity)
- Threshold separating laminar flow from turbulent flow = 2000 (unitless)
What is shear and how does it apply?
- Lateral stress on fluid as consequence of traveling at different velocities
- Greatest at wall of blood vessels and if shear stress is too high it can result in hemolytic anemia (rupturing of RBCs)
Poiseuille’s Law
R = (8 * n * l) / (pi * r^4)
- n = viscosity
- l = length
- r = radius
Resistance: Parallel vs Series
- Series is sum
- Parallel is reciprocal sum of reciprocals
Define compliance
- Change in volume that results from change in pressure
(Veins are most compliant vessels in body)
Pulse Pressure
Difference between SBP and DBP
Mean Arterial Pressure
- Mean pressure across cardiac cycle
- MAP = DBP + PP/3
BP Equation
- BP = CO x Total Peripheral Resistance
Cardiac Output Equation
- CO = HR * SV (Stroke volume)
What is stroke volume
Difference between EDV and ESV
Why do pressures in the aorta/arteries never drop significantly?
There’s still blood remaining during diastole, distending the aorta/artery when the next systole comes around
Elastic Artery (Ex. Aorta)
- >10mm diameter
- Tunica intima: Endothelium with connective tissue plus smooth muscle cells and thin internal elastic membrane
- Tunica media: Thick with alternating layers of smooth muscle cells and fenestrated elastic lamellae
- Tunica adventitia: Thin layer of connective tissue containing fibroblasts, macrophages, and vasa vasorum
Muscular Artery
- 2-10mm in diameter
- Tunica intima: Endothelial cells with thin prominent internal elastic membrane
- Tunica media: Smooth muscle layer (with very small amount of collagen and elastin)
- Tunica adventitia: thick, mostly collagen and elastin
What is the vasa vasorum?
Tiny network of vessels that deliver blood to the larger vessels
Large Vein
- Thin tunica intima and tunica media
- Thick tunica adventitia with prominent longitudinal bundles of smooth muscle in the adventitia
Small/Medium Vein
- Thin tunica intima and tunica media w/ many layers of circular smooth muscle + collagen + elastin fibers
- Thick tunica adventitia w/ elastic fibers and often bundles of longitudinal muscle at the interface between media and adventitia
- 5 - Venule: Larger but thinner walled, and smoother contour to the lumen
- 6 - Arteriole: Smaller but thicker walled (more smooth muscle layers surrounding endothelium)
Muscular Artery
Different types of capillaries
- Continuous
- Muscle, BBB, fat
- Fenestrated
- Endocrine organs and sites of extensive passage of fluid and metabolites (GI, gall bladder, kidney)
- Sinusoid (Discontinuous)
- Typically larger in diameter
- Areas w/ great degree of leakiness (Liver, spleen, and BM)
How does capillary endothelium impact permeability?
- Capillaries don’t have multiple layers (Tunica media or adventitia) and primarily consists of endothelial cells that are elongated along with their nuclei in the direction of blood flow
- Usually surrounded by pericytes
Pros and Cons of Echocardiogram
- Pros: Versatile, portable, inexpensive, no radiation. Useful for:
- Chamber size and function
- Valvular structure and function
- Aortic/Pulmonary artery diameter and pressure
- Cons: Imaging limitations include:
- Can’t acquire overall anatomical structure, low image quality and resolution, can’t be used for assessing coronary artery function
Pros and Cons of CMR
- Pros: Higher res, no radiation. Useful for:
- Cardiac and great vessel anatomy
- Ventricular size and function
- Myocardial scarring and viability
- Cons: Less available and more expensive
- Just okay at assessing coronary artery structure, valve structure and function, and diastolic function
Pros and Cons of CMT (Cardiac computed tomography)
- Pros: High res. Useful for:
- Cardiac and great vessel anatomy
- Ventricular size and function
- Coronary artery calcification
- Coronary artery anatomy and severity of atherosclerotic obstruction
- Cons: Relatively high radiation burden
- Not that great at valvular structure and function, or diastolic function
Parameters (w/ equations) to measure ventricular systolic function?
- Stroke Volume: SV = EDV - ESV
- Cardiac Output: CO = HR * SV
- Ejection Fraction: SV/EDV
Three Early embryonic vascular systems
- Intra-embryonic: Aorta and cardinal veins in embryo
- Placental: Umbilical arteries and veins to placenta
- Vitelline: Vessels to and from the yolk sac
Source of first embryonic blood cells
Yolk sac (specifically the wall)
What is the fate of the embryonic vitelline system of veins?
- It traverses the abdominal wall and forms the hepatic portal system and veins + intrahepatic inferior vena cava
What is the fate of the embryonic cardinal system of veins?
- Remains to form the veins above the heart (superior vena cava and L+R brachiocephalic veins)
What is the fate of the embryonic umbilical system of veins?
- Collapses from lack of blood
Order and fate of embryonic vein development
- Cardinal
- Anterior + Posterior → Common cardinal vein
- Anterior → Head/Upper extremities veins
- Posterior → Pelvic/Leg veins
- Subcardinal
- Middle inferior vena cava + renal and gonadal veins
- Supracardinal
- Azygos system and lower inferior vena cava
Embryonic Heart Development (prior to Day 28ish)
- Cardiogenic mesoderm from primitive streak
- L+R heart tubes merge into single tube (Day 22)
- Heart bends to the right to form 2 ventricles in sequence (Day 25)
- Sinus venosus → Atrium → AV canal → Ventricle → Bulbus cordis → Truncus arteriosus → Aortic sac
Embryonic Heart Development (from Day 28ish)
- Endocardial cushions (dorsal and ventral) divide blood flow into L+R (Day 28)
- Growth of Septum Primum (Day 28)
- Appearance of foramen secundum in septum primum and beginning of growth of septum secundum (Day 32)
- Growth of intraventricular septum (yet to fuse w/ endocardial cushions) and formation of the two inter-atrial septa
- Septum primum and then septum secundum
How do atrial septal defects typically occur?
- Foramen ovale and/or the foramen secundum are too large and overlap with each other
- Septum primum fails to fuse with the endocardial cushions
- Holes appear anywhere in the inter-atrial septum
Structure and function of the spiral septum
- AKA aortico-pulmonary septum
- Divides truncus arteriosus into the aorta and pulmonary trunk
- Grows obliquely to fuse with the IV septum and the endocardial cushions and completes ventricular division
Adult derivative of sinus venosus
- Left horn → Coronary sinus
- Right horn → Smooth posterior wall of RA
Adult derivative of bulbus cordis
- Conus arteriosus (smooth part of LV)
- Aortic vestibule (smooth part of RV)
Trace the flow of blood in the fetus with emphasis on the two shunts
- Placenta/umbilical cord → bypasses liver via ductus venosus, mixes with venous blood from lower half of the fetus (still highly oxygenated) at inferior vena cava → RA → RV OR foramen ovale → LA
- … RV (as mixed blood) → pulmonary trunk → (some goes to lungs but most goes to) DUCTUS ARTERIOSUS → arch of the aorta (after it’s already branched to upper extremities)…
Identify the changes that occur at birth to transform the system into the postnatal pattern
- Blood rushes into the lungs (pulmonary flow increases) and not so much into the aorta through the ductus arteriosus due to such low blood pressure in the lungs
- LA pressure increases with blood coming from pulm veins
- Foramen ovale closes
- Umbilical arteries get higher oxygenated blood, spasm and constrict – blood flow to placenta is greatly reduced
- Umbilical vein collapses
- Ductus arteriosus becomes ligamentum arteriosum (after a few weeks)
- Ductus venosus becomes the ligamentum venosum
Postnatal lungs acquiring too much blood indicates?
Septal defects
Postnatal lungs acquiring too little blood indicates?
Tetralogy of Fallot
Tetralogy of Fallot
- Faulty spiral (aortico-pulmonary) septum defect that leads to cascade of abnormalities:
- Pulmonary stenosis
- IV septal defect
- Overriding aorta
- RV hypertrophy
What’s more concerning, ventricular or atrial septal defects?
- Ventricular defects (and other high pressure chamber/vessel defects) are more serious than atrial defects that operate at lower pressures
Transposition of the Great Arteries
- Systemic and Pulmonary circulations in parallel not in series
- RV to aorta, LV to pulmonary trunk - indicates defect with spiral septum
- Huge IV septal defect can be beneficial in this case because it allows just enough mixing of the blood to keep neonate alive until surgical intervention
IV septal defects
Types and effects on cardiopulm system
- Membraneous - most common, hole high up on IV wall where IV septum fuses with endocardial cushion and spiral septum. Also the thinnest part and where blood is most dynamic
- Muscular - hole in muscular wall of IV septum
- With IV septal defects, lungs acquire higher volume and pressure overload which flow into the LA and affect the mitral valve → distention and blood backup → CHF
