Heart Flashcards
What muscle is the primary component of the myocardium?
cardiac muscle
What does the myocardium form? What is it composed of?
- composed of cardiac muscle
- forms the middle layer of the heart wall
How are cardiac muscle fibers arranged in the middle layer of the heart wall?
spiral pattern
What is the function of cardiac muscle cells? What do they produce? State an example.
produce hormones (eg. atrial natriuretic peptide) –> regulate blood pressure and electrolyte balance
What is the function of the hormones released by cardiac muscle cells? State their process of working.
hormones (eg. atrial natriuretic peptide) are released by cardiac muscle cells into cardiac capillaries.
influence blood pressure and electrolyte balance.
Where is myocardium thickest?
left ventricle
Where is myocardium thinnest?
atria
What are the three layers of the heart?
- epicardium
- myocardium
- endocardium
What is the endocardium? What is it continuous with?
- the inner layer of the heart
- continuous with the tunica interna of the blood vessels that enter and exit the 4 heart chambers
What is the endocardium composed of?
lining of endothelium supported by:
- inner dense subendothelial layers of connective tissue
- outer loose subendothelial layers of connective tissue
Where is the endocardium thicker?
Endocardium of the atria is thicker than the endocardium of the ventricles.
What is “endocardium” of the heart similar to in other organs?
tunica mucosa
What is “myocardium” of the heart similar to in other organs?
tunica muscularis
What is “epicardium” of the heart similar to in other organs?
serosa
Why do we have specific names for the layers of the heart?
the heart is a special organ, therefore it has its own names.
What does the endocardium have?
“tunica mucosa”
1) epithelium: called “endothelium”- simple squamous epithelium lining all circulatory system organs.
What is the epithelium covering all circulatory system organs?
endothelium- simple squamous epithelium
What is located beneath the endothelium?
2 layers of connective tissue:
1) dense irregular connective tissue (like “lamina propria”
2) loose connective tissue
What is cardiac muscle tissue composed of?
cardiac muscle cells!
- cylindrical shaped cells
- centered nucleus
- intercallated disks (integrations between adjacent cells= high proportion of cell junctions= hold cells tightly bound)
CELLS NOT FIBERS!
Why can one NOT call cardiac muscle cells “fibers”?
“fibers” are features of skeletal muscle tissue, not cardiac!
skeletal muscle tissue:
- very long cells=fibers
- border nucleus
cardiac muscle tissue:
- cylinder shaped cell
- centered nucleus
- intercallated discs (integrations between adjacent cells= high proportion of cell junctions= hold cells tightly bound)
What system do cardiac muscle cells work as?
endocrine system cells
(they secrete hormones to regulate blood pressure)
What is the final layer of the heart?
- dense connective tissue
- pericardium (epithelial covering)
What is the pericardium?
an epithelial lining of the heart (surrounding the dense connective tissue)
What does the pericardial cavity seperate?
the parietal and visceral layers of the pericardium
What does the pericardial cavity contain?
small quantity of pericardial fluid
What are the different layers of the pericardium?
- visceral serous layer
- parietal serous layer
- fibrous layer
What is the epicardium?
the visceral serous pericardium
What is the visceral serous pericardium?
- the outer layer of the heart wall
- continuous with the parietal serous pericardium at the base of the heart
Where is the visceral serous pericardium continuous with the parietal serous pericardium?
- at the base of the heart
- on the inner surface of the pericardial sac
State the position of the visceral and parietal serous pericardium layers.
visceral- ‘connected to’ the heart center
parietal- ‘connected’ to the heart outer layer, after the cavity
What is the fibrous pericardium composed of?
dense connective tissue
State the composition and position of the fibrous pericardium.
- dense connective tissue layer
- lies beneath the mesothelial cells of the parietal serous pericardium
How many layers does the pericardium have? What are they? What are they based on?
3 layers (1 fibrous and 2 serous):
fibrous layer- dense irregular connective tissue
parietal serous layer- serosa: mesothelial cells (simple quamous epithelium)
- attached to the fibrous layer
visceral serous layer- serosa: mesothelial cells (simple squamous epithelium)
- attached to the heart itself, also known as ‘epicardium’
What makes up the pericardial sac?
fibrous pericardial layer and parietal serous pericardial layer
What is the “epicardium”? (another name)
another name for the visceral serous layer of the heart
What are the two names of the outside section of the heart organ itself?
- visceral layer part of the pericardium (whole)
- epicardium (organ only)
depending if one is looking at the organ itself or whole heart
What is fibrous pericardium made up of?
dense irregular connective tissue
What is serous pericardium made up of? What does it secrete?
serosa
- mesothelial cells
- simple squamous epithelium
- has connected tissue underneath
- produces serous secrete
Where is the serous secrete made by mesothelial cells of the serous layer secreted to? What is its function
pericardial cavity
- between the two serous walls (parietal and visceral layer)
- reduces friction (lubricates) created during heart contractions and relaxations
What is the epicardium? Another name? What does it cover? What is it composed of? What underlies it?
- ‘visceral pericardium’
- covers outer surface of the heart
- single layer of mesothelial cells
- underlying connective tissue
What is the subepicardial connective tissue? What does it contain?
contains:
- blood vessels
- nerves
- varying amount of fat
How does epicardium compare to typical serosa?
It has much more connective tissue beneath the mesothelial cells.
What is the name of the bundle of cardiac conduction fibers located in the heart?
atrioventricular bundle (bundle of His)
Where is the atrioventricular bundle located?
- extends from the atriovetricular node
- through the subendocardium
- divides into the right and left bundle branches
Where do the branches of the atrioventricular bundle ramify?
in the myocardium of the ventricles
What is another name used for cardiac conduction fibers?
Purkinje fibers
How do cardiac conduction fibers compare with cardiac myocytes?
cardiac conduction fibers are:
- wider
- shorter
(than cardiac myocytes)
What is the structure of cardiac conduction fibers?
- shorter than myocytes
- wider than myocytes
- have few myofibrils and myofillaments
- pale cytoplasm
- clear zone located centrally around the nucleus
What forms the pale cytoplasm in cardiac conduction fibers?
few myofibrils and myofilaments
What is the function of the ‘cardiac impulse conductive system’?
It makes nervous impulses which lead to heart contractions.
What is unique about the heart?
- it is not stimulated by the central nervous system
- it is myogenic
- autonomous system working on itself
- the impulse is not made on nervous tissue (neurons, neuroglia cells etc.)
- the impulse is based on myocytes
What is the entire cardiac impulse conduction system based on?
myocytes!
(not typical cardiac muscle cells. they are called ‘heart conductive myocytes’)
How do heart conductive myocytes compare to typical cardiac muscle cells?
heart conductive myocytes are:
- bigger
- paler (not as dark) (fewer myofibrils and myofillaments)
(than typical cardiac muscle cells)
appearance similar to adipocytes (size, colour, etc.)
Where is the conductive system positioned?
in the ENDOCARDIUM!
What is heart rate controlled by? Where is it located?
sinoatrial node located in the wall of the right atrium
Explain the action of the cardiac impulse conductive system.
wave of depolarization spreads from the sinoatrial node through the internodal connective pathway to the atrioventricular node
Where is the atrioventricular node located?
- the junction of the atria and the coronary sinus
- near the right atrioventricular valve
What is the cardiac skeleton?
- the base of the heart support
- where the major blood vessels enter and exit
What is the cardiac skeleton composed of?
dense irregular connective tissue
depends on the animal and age! (it can mineralize in older organisms)
What additional structures are usually present in the cardiac skeleton of dogs?
fibrocartilage
What additional structures are usually present in the cardiac skeleton of horses?
hyaline cartilage
What additional structures are usually present in the cardiac skeleton of ruminants?
bone
What are the functions of the cardiac skeleton?
- strongly attaches valves to the internal heart wall
- keeps heart valves open (disabling them from changing shape)
- stabilizes the entire heart structure
- prevents heart from malfunction (fatal)
- acts as an electrical insulator (prevents electrical impulses from spreading across the all chambers at the same time (fatal))
What type of component is the cardiac skeleton?
not stroma!!
heart is not a parenchymal organ! it is tubular!
What type of organ is the heart?
tubular organ!
NOT PARENCHYMAL!
