Heart (histo) Flashcards
Describe systemic circulation
Oxygenated blood leaves the heart to other tissues via arteries; Nutrient exchange occurs at the capillaries; Deoxygenated blood returns to the heart via veins
Describe the pulmonary circulation
Deoxygenated blood is pumped from the heart to the lungs via the pulmonary artery; oxygenated blood is pumped from the lungs to the heart via the pulmonary veins
Describe the Tunica Intima; what type of cells does it have?
It’s the innermost layer of the blood vessel; it contains a SINGLE layer of squamous epithelial cells (endothelium)
Describe the Tunica Media; what type of cells does it contain?
It is the middle layer of the blood vessel wall;
Depending on the vessel type: either circumferentially arranged smooth muscle cells or elastic lamellae; Smooth muscle cells produce the extracellular molecules of the t.media
Describe the tunica adventitia; what type of cells does it contain?
Outermost connective tissue; it consists of longitudinally arranged collagen and elastic fibers, smooth muscle cells and fibroblasts;
It may contain vasa vasorum and nervi vascularis
Where is the heart located? what surround it?
heart is located in the middle mediastinum and is surrounded by the pericardial sac
What are the layers of the pericardial sac?
- fibrous pericardium (external fibrous layer)
2. serous pericardium (parietal + visceral layers)
Describe the fibrous pericardium layer of the pericardial sac: what type of tissue is it made up of?
a dense fibroelastic CT that blends in with surrounding loose CT
Describe the parietal layer of the serous pericardium (of the pericardial sac): what type of tissue is it made up of? where is it located?
loose CT + layer of squamous epithelium (mesothelium); located between the fibrous layer and visceral layer of the pericardium
Describe the Visceral layer of the serous pericardium: what type of tissue is it made up of? where is it located?
made of loose CT + layer of squamous epithelium (mesothelium); located directly adjacent to the heart muscle layer;
called “epicardium”
where do the parietal and visceral layers of the serous pericardium meet?
at the reflexion at the base of the heart, forming a sac
where is the paricardial cavity located?
between the parietal and visceral layers of the serous pericardium
is the pericardial cavity an actual or potential space?
potential space
what is the function of the thin film of fluid found in the pericardial cavity?
to help lubricate the heart and to prevent friction during beating
what is pericarditis? what does it cause? what can it result in?
it is an inflammation of the pericardium that can cause friction between the layers and restrict beating of the heart;
it can result in pericardial effusion
what is pericardial effusion?
an abnormal collection of fluid in the pericardial cavity that interferes with the normal heart contraction and decreases the ability of the heart to effectively pump blood
Describe the path of blood flow in the heart (starting with systemic venous return)
- Deoxygenated blood returns from the body tissue via the IVC and SVC and enters the right atrium
- Deoxy blood passes through the tricuspid (right AV) valve from the right atrium to the right ventricle
- Deoxy blood pumped through the pulmonary semilunar valve to the pulmonary artery to the lungs for oxygenation
- Oxy blood leaves the lungs via the pulmonary veins and enter the left atrium
- oxy blood passes through the mitral (bicuspid, left AV) valve to the left ventricle
- Oxy blood pumped through the aortic semilunar valve to the aorta and aortic tree for systemic circulation via the arteries
- nutrient exchange occurs at the capillaries and then deoxy blood returned via veins and cycle repeats
what separates the atria?
intratrial septum
what separates the ventricles?
intraventricular septum
what separates the two atria and ventricles?
cardiac skeleton
What is the cardia skeleton? what type of tissue is it made of?
it is the central supporting structure of the heart to which some of the cardiac muscle fibers are attached and with which the valves are supported;
composed of dense Irregular CT
What is the function of the annuli fibrosi?
surrounds each of the four cardiac valves to stabilize them; the core of the valve cusps (leaflets) arise from the CT
what is the function of the Trigona fibrosi? what are they made of?
triangular islands of CT that serve to strengthen the annuli fibrosi
what is the Septum Membranaceum?
an extension of the cardiac skeleton into the interventricular septum
What are the functions of the cardiac skeleton?
- Separates the atrial musculature from the ventricular musculature
- Functions as sites of origin (points of insertion) of cardiac muscle
- Localizes and stabilizes valves
- Limits the diameter of valves
- Prevents spread of electrical impulses except via the conducting system
what are the 3 layers of the heart wall?
- epicardium (visceral pericardium)
- myocardium
- endocardium
Which layer of the heart wall is the external layer?
epicardium
what layer of the blood vessel is the epicardium analogous to?
tunica adventitia
what type of tissue/cells does the epicardium contain?
- a layer of simple squamous epithelium called mesothelium with its associated basal lamina
- CT = subepicardium: fat, collagen fibers, elastic fibers, arteries, veins, and nerves
- epicardium is the region where fat is stored in the heart; the coronary artery, cardiac veins and nerves that supply the heart are located in the CT and typically surrounded by fat
what is the middle layer of the heart wall? what does it contain?
myocardium; contains the cardiac muscle cells
what layer of the blood vessels is the myocardium analogous to?
tunica media
Describe cardiac muscle cells
one or two nuclei, packed with myofibrils and large mitochondria and connect to each other via extensive intercalated discs
what do intercalated discs consist of?
- Fasica adherens
- Desmosomes
- Gap junctions
What is the function of fascia adherens? how do they perform this function?
connect 2 cardia muscle cells via a junction binding to actin thin filaments in each cell
what is the function of desmosomes? how do they perform their function?
connect two cells via desmin and vimentin intermediate filaments
what are gap junctions?
provide for ionic communication and coupling
How does the atrial myocardium differ from the ventricular myocardium?
atrial myocardium is thinner
how is the myocardium of the left ventricle different from the myocardium of the right ventricle?
myocardium of the left ventricle is 3x thicker (has to pump blood to the entire body)
How does the morphology of atrial myocardial cells compare to that of the ventricular myocardial cells?
atrial myocardial cells are smaller and have less elaborate t-tubule system; they have MORE gap junctions
What is the relationship between atrial cardiac muscle cells and atrial natriuretic factor (ANF)
atrial cardiac muscle cells produce, store, and secrete ANF (a polypeptide)
where is ANF stored?
in electron dense granules in the atrial cardiac muscle cells
where is ANF released?
released into surrounding capillaries of the atrium
where are receptors for ANF found?
cells in the adrenal cortex, kidney, and vascular smooth muscle
what is the function of ANF?
stimulates the kidney to excrete sodium in the urine and functions in regulating fluid balance, electrolyte balance (sodium levels), and blood pressure
Does ANF cause and increase or decrease in arterial blood pressure?
decrease
How are the muscles arranged in the ventricular wall?
in a complex spiral and helical pattern (trabeculae carnea)
what are papillary muscles?
fingerlike muscular projections from the ventricular wall into the lumen of the ventricle
How are the muscles arranged in the atrial wall?
into pectinate musculature = innermost bundles of muscle fibers are arranged as a latticework that gives a ridged appearance
what is the internal layer of the heart wall?
endocardium
what does the endocardium line?
cardiac valves, papillary muscles, and the inner walls of the atria and ventricles
what layer of the blood vessels is the endocardium analogous to?
tunica intima
what type of tissue/cells makes up the endocardium?
- endothelium (simple squamous epithelium) + basal lamina
2. CT: contains fibroblasts, collagen fibers, elastic fibers, some smooth muscles
what is the deeper layer of the endocardium CT called? what does it connect to?
subendocardial layer; connects to the myocardium
What is the function of the impulse conduction system of the heart
initiate and conduct electrochemical impulses resulting in the coordinated contraction and relaxation of the heart
What controls the cardiac contraction?
autonomic nervous system; NOT stimuli of the nervous system
What happens to the heart if it is: 1. simulated by sympathetic nerves? 2. stimulated by parasympathetic nerves?
sympathetic = accelerates heart rate parasympathetic = slows heart rate
where is the conduction impulse of the heart initated?
in the SA node
Describe the conduction system of the heart (pathway)
- impulse is initiated in the SA node (near the SVC in the right atrium)
- impulse travels though the atrial muscle, resulting in atrial contraction
- impulse conducted to the AV node via internodal fibers
- impulse is delayed at the AV node to allow the ventricles to fill with blood
- impulse passes quickly through Bundle of His, left and right bundle branches and then to the purkinje fibers
- impulse is delivered to a subset of ventricular cardiac muscles that when stimulated conduct the impulse to other ventricular cardiac muscle cells via gap junctions (results in ventricular contraction)
how fast is the impulse passed in the purkinje fibers?
4m/sec
what does an electrocardiogram (ECG) record?
a voltage trace recording of the conduction of electrical contraction impulses through the heart
where is the SA node located?
in the wall of the right atrium, close to the orifice of the SVC; often surrounds a branch of the coronary artery
How do SA nodal cells compare to cardiac muscle cells in shape, myofibril content, staining, and intercalated discs?
shape: spindle shape and smaller than normal cardiac muscle cells
myofibrils: fewer in number and less organized than normal cardiac muscle cells
stain: paler that normal cardiac muscle cells
intercalated discs: less well developed than normal cardiac muscle cells
what is considered the pacemaker of the heart?
SA node because it initiates the contraction of the heart
where does the impulse that is initiated by the SA node spread along? to?
spreads along tracts of the modified cardiac muscle fibers (internodal fibers) to the AV node
where is the AV node located?
in the floor of the right atrium just above the tricuspid valve
Describe the morphology of the AV node
appears as a mass of small, pale-staining cells isolated by CT (similar to SA node appearance) : roughly spindle shaped and in some areas form a reticular meshwork, intercalated discs connect the cells but they are poorly developed
where is the impulse delayed during the cardiac contraction cycle? why?
in the AV node to allow filling of the ventricles
where does the impulse pass from the AV node?
to the bundle of his
Where is the Bundle of His located?
Runs form the AV node in the right atrium into the interventricular septum by traversing the right fibrous trigone of the cardiac skeleton;
Runs along the margin of the septum membranaceum
where does the Bundle of His divide into the left and right bundle branches?
in the interventricular septum
How does the morphology of the cells in the Bundle of His compare to that of nodal cells?
larger, but have fewer myofibrils than typical cardiac muscle cells
where do bundle branches (of the bundle of his) terminate?
in the CT between the endocardium and myocardium of the right and left ventricles as Purkinje fibers aka the SUBENDOCARDIUM
where are purkinje fibers located?
in the subendocardial CT of ventricular endocardium
what is the function of Purkinje Fibers
transmit impulses to a subset of ventricular cardiac muscle cells at the endocardium/myocardium interface
How do purkinje fibers compare to normal cardiac cells
larger and more rounded cells and nuclei than normal cardiac cells
How do Purkinje cells stain? why?
pale-staining and vaculoated because they have lots of GLYCOGEN
Do purkinje fibers have myofibrils? T-tubule system? intercalated discs?
few myofibrils
NO T-Tubule system
connect via intercalated discs but not well developed
what is the function of the cardiac valves?
to control the direction of blood flow through the heart
Describe the valves of the hear
- Left AV (mitral, bicuspid) = 2 cusp
- Right AV (tricuspid) = 3 cusps
- Pulmonary semilunar = 3 cusps
- Aortic semilunar = 3 cusps
Where do cardiac valves extend from?
the annuli fibrosi of the cardiac skeleton
what type of tissue makes up the cardiac valves?
core of fibrous dense irregular connective tissue, the fibrosa continuous with annuli fibrosi
Is the endocardium associated the valves? if yes, how?
endocardium covers the free atrial and ventricular surfaces of the valves
How are the atrioventricular valves attached to the heart wall?
by chordae tendinae
what are the chordae tenidnae
fibrous cords of dense irregular CT that extend from the free edges of the valves to papillary muscles and thus connect the AV valves to the heart wall
what control the chordae teninae? what’s their function?
papillary muscle control the chordae tendinae
chordae tendinae function to prevent eversion of valve leaflefts.
