organs/structures
organs |
heart, blood vessels, blood |
structures |
layers of heart - pericardium, epicardium, myocardium, endocardium |
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valves |
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chambers |
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major vessels |
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major cell types of blood |
thickness of cardiac walls
myocardium of left ventricle is thicker than right - to do with demands of pumping blood away from heart. |
arteries & veins
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have: three major layers: the tunica interna (featuring the endothelium); tunica media (featuring circular smooth muscle & elastic fibers); and tunica externa (featuring elastic & collagen fibers).
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elastic arteries large arteries with more elastic fibres & less smooth muscle, are able to receive blood under pressure & propel it onward, also called conducting arteries as they conduct blood from the heart to medium sized muscular arteries
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muscular arteries medium-sized arteries with more muscle than elastic fibres in tunica media, capable of greater vasoconstriction & vasodilation to adjust rate of flow - walls are relatively thick, called distributing arteries as they direct blood flow
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aorta divisions
1. ascending aorta
2. arch of aorta
3. thoracic aorta
4. abdominal aorta |
regulation of heart rate
nervous control from cardiovascular centre in medulla: sympathetic impulses increase heart rate & force of contraction, parasympathetic impulses decrease heart rate, baroreceptors (pressure receptors) detect change in BP & send info to cardiovascular centre (located in arch of aorta & carotid sinuses).
heart rate is also affected by hormones:
- adrenaline, noradrenaline, thyroid hormones
- ions NA+, K+, Ca2+
- age, gender, physical fitness & temperature |
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cell types
heart |
blood vessels |
blood |
pericardium |
endothelium |
leukocytes; WBCs |
epicardium |
myocardium - cardiac monocytes |
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valves |
conducting nerve bundles (SA/AV Nodes) |
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pericardium |
venules
- small veins collecting blood from capillaries
- tunica media contains only a few smooth muscle cells & scattered fibroblasts - very porous endothelium allows for escape of many phagocytic WBCs
- venules that approach size of veins more closely resemble structure of vein |
arterioles
- small arteries delivering blood to capillaries - tunica media containing few layers of muscle
- metarterioles form branches into capillary bed - to bypass capillary bed, precapillary sphincters close & blood flows out of bed in throughfare channel, vasomotion is intermittent contraction & relaxation of sphincters that allow filling of capillary bed 5-10 times/minute. |
veins of systemic circulation
- drain blood from entire body & return it to right side of heart
- deep veins parallel the arteries in the region
- superficial veins are found just beneath the skin
- all venous blood drains to either superior or inferior vena cava or coronary sinus |
circulatory routes
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systemic left side heart to body & back to heart
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hepatic portal capillaries of GI tracts to capillaries in liver
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pulmonary right side heart to lungs & back to heart
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foetal fetal heart through umbilical cord to placenta & back
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physiological functions
heart |
pumps over 1 million gallons / year, over 60 000 miles of blood vessels |
vessels |
retain & circulate blood, help regulate pulse pressure |
blood |
erythrocytes - distribute oxygen from & CO2 to lungs |
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leukocytes - circulating immune cells to combat infection |
cardiac muscle histology
- branching, intercalated discs with gap junctions, involuntary, striated, single central nucleus per cell.
- desmosomes between myocytes allow depolarisation of adjacent fibers.
- Striations are created by the organisation of myofilaments, actin & myosin |
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electrocardiogram - ECG or EKG
ECG - action potentials of all active cells can be detected & recorded
- P wave = atrial depolarization
- P to Q = conduction time from atrial to ventricular excitation
- QRS complex = ventricular depolarization
- T wave = ventricular repolarization
- Q-T = time for ventricular depolarization & repolarisation to occur
- S-T segment = ventricular fibres depolarised (plateau phase of AP)
electrical conductance
1. SA-Node (in right atrium)
2. AV-Node
3. AV-Node (bundle of His)
4. right & left bundle branches
5. Purkinje fibres |
valves & blood circulation
- valves open & close in response to pressure changes as hear contracts & relaxes.
- dense connective tissue rings surround the valves of the heart, fuse & merge with the interventricular septum.
- support for heart valves, insertion point for cardiac muscle bundles, electrical insulator between atria & ventricles. |
capillaries
found near every cell but more extensive in highly active tissue (muscles, liver, kidneys & brain)
entire capillary bed fills with blood when tissue is active lacking in epithelia of: cornea & lens of eye & cartilage
walls are composed of only one layer of endothelium cells & basement membrane |
layers of heart wall
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pericardium dense irregular connective tissue
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epicardium visceral layer of serous pericardium
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myocardium cardiac muscle layer
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endocardium chamber lining & valves, smooth lubricating layer
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