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BIOL 1030 – TOPIC 20 LECTURE NOTES
Topic 20: Circulatory System (Ch. 42)
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circulation required for all animals that are more than a few cells thick so that cells can get oxygen and nutrients and get rid of
wastes
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two main types of circulatory systems, open and closed
A. open systems
1.
no distinction between circulating fluid and extracellular fluid of body (lymph)
2.
hemolymph is the circulating fluid
3.
less efficient for transport (little pressure, slower)
4.
may still have heart(s) for pumping and some vessels
5.
examples: arthropods, mollusks
B. closed systems
1.
circulating fluid (blood) distinct from lymph
2.
at least one heart always present
3.
blood vessels – tubular network for blood flow from heart of body and back
4.
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arteries carry blood away from heart
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veins return blood to heart
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capillaries between arteries and veins are the thinnest vessel and allow exchanges with body tissues
lymph system - when blood reaches capillaries, liquid seeps out of blood, most is mopped up, but much remains behind
and needs to be mopped up or an edema (swelling) will form, lymph vessels return liquid to blood
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vertebrate circulatory systems functions
A. transportation of gasses, nutrients, wastes
B. regulation of temperature
C. transportation of hormones
D. protection (immune defense; blood clotting)
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blood plasma
A. metabolites, wastes and hormones including carbon dioxide
B. ions - mostly sodium, chloride, and bicarbonate, lower total ion concentration than sea water
C. proteins - albumin, globulins (carry lipids and steroid hormones and fibrinogen) serum = fluid after fibrinogen clots out
D. formed elements – blood cells
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BIOL 1030 – TOPIC 20 LECTURE NOTES
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blood cells
A. erythrocytes - red blood cells
1.
5 million/cm3
2.
45% of blood (hematocrit)
3.
mammals - anucleate, donut shaped cell that carries hemoglobin
4.
live 120 days before replacement in humans
5.
formed in bone marrow
B. leukocytes - white blood cells
1.
1% of cells in blood
2.
larger, nucleated, can migrate out of capillaries
3.
no hemoglobin
4.
granular leukocyte - neutrophils (most common), eosinophils, and basophils
5.
nongranular leukocytes - monocytes and lymphocytes (T and B cells involved in immune response)
6.
neutrophils accumulate at injury and then joined by monocytes that change into macrophages
7.
phagocytosis by neutrophils and macrophages eliminate disease-causing organisms
C. platelets
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1.
megakaryocytes in marrow break off bits of their cytoplasm to form platelets, which are actually cell fragments, not cells
2.
accumulate at wound and form a plug by sticking to each other and tissues
3.
plug reinforced by fibrin (formed by fibrinogen in complex chain of events)
blood vessels
A. structure - endothelium then elastic fibers then smooth muscle layer then connective tissue (except capillaries)
B. arteries
1.
large ones - very elastic to absorb force of heart
2.
small ones (arterioles) - more muscular - to control blood flow (vasoconstriction and vasodilation)
C. capillaries
1.
only endothelial lining (one-cell thick)
2.
about one red blood cell wide
3.
all exchange occurs here
4.
little blood pressure after exit
D. veins and venules (smaller veins, just after capillaries)
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BIOL 1030 – TOPIC 20 LECTURE NOTES
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less muscular than arteries
2.
blood pressure greatly reduced in venous system - possibility for retrograde (back) flow
3.
valves - present in ascending veins to halt retrograde flow
4.
descending veins - no valves, gravity helps
5.
skeletal muscles help move blood - contract leg muscles to avoid fainting, which is typically caused by blood pooling in
the legs
6.
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varicose veins - veins expanded too much and no longer work
the mammal heart
A. 4 chambers
B. right side - atrium receives blood from body, pumps to ventricle, which pumps to lungs
C. left side - atrium receives blood from lungs, pumps to ventricle, which pumps to body
D. atria both pump at the same time, then after about 100 ms delay both ventricles pump; both sides must pump the same
volume, but the left pumps at greater pressure because it is going through greater resistance
E. valves prevent backflow
F.
sinoatrial node (SA node) - pacemaker - starts impulse at atria and sends impulse to atrioventricular (AV) node
G. AV node shunts impulse to the apex (bottom) of the heart through Purkinje fibers - modified cardiac muscle cells that look
like neurons (unique to mammals)
H. shunted impulse squeezes the heart from the bottom up - more efficient just like squeezing the toothpaste from the bottom of
the tube is more efficient
I. heart rate increases under exercise to get enough oxygen to muscles
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