Circulatory & Lymphatic Systems Flashcards
what is the purpose of the circulatory system?
distribute nutrients, transport oxygen and carbon dioxide, transport/remove metabolic wastes from tissues to excretory/kidney, transport hormones and provide feedback, maintain homeostasis of body temperature, hemostasis (blood clotting)
perfusion
the flow of blood through a tissue
ischemia
inadequate blood flow (i.e. no waste removal either)
hypoxia
reduced oxygen (i.e. blood can still remove waste)
heart
muscular pump that forces blood through a branching series of vessels to the lungs and the rest of the body
arteries
vessels that carry blood away from the heart at high pressure
veins
vessels that carry blood back toward the heart at low pressure
arterioles
increasingly smaller arteries, contain walls of smooth muscle that can constrict/dilate to control resistance and amount of blood flow into the capillaries of tissues
capillaries
very small vessels that are wide enough for only a single blood cell to pass, one endothelial cell layer, where exchange of material with tissues occur
venules
small veins where blood collects after exiting capillaries
endothelial cells
a thin inner lining found in all blood vessels, capillaries are formed from only a single layer of endothelial cells, have important roles in vascular function
what are some functions of endothelial cells?
vasodilation and vasoconstriction, inflammation (release of inflammatory chemicals from injured tissues stimulate endothelial cells to increase their expression of adhesion molecules), angiogenesis (formation of new blood vessels), thrombosis (blood clotting, undamaged endothelial cells secrete substances that inhibit the coagulation cascade)
pulmonary circulation
the flow of blood from the heart to the lungs and back to the heart
systemic circulation
the flow of blood from the heart to the rest of the body and back again
portal systems
circulatory systems that consist of two sets of capillaries, allow for direct transport between tissues without having to pass through the whole body
what are the two portal systems in the human body?
hepatic portal system (capillaries in intestines and liver for nutrient delivery) and hypothalamic-hypophysial portal system (capillaries in hypothalamus and pituitary for hormone delivery)
atria
chambers that collect blood
right atrium receives:
deoxygenated blood from the systemic circulation via the inferior and superior vena cava
ventricle
chambers that pump blood out of the heart at high pressure
coronary arteries
the very first branches from the aorta which supply blood to the wall of the heart
coronary veins
where deoxygenated blood from the heart collect, merges to the coronary sinus which drains directly into the right atrium
what are the two types of valves in the heart?
atrioventricular valves (tricuspid valve-right and bicuspid/mitral-left) and semilunar valves (pulmonary and aortic semilunar valves)
valves in veins prevent:
backflow and help to push the low pressure blood to the heart, contractions of skeletal muscle also helps to pressurize and push venous blood
diastole
ventricles relax and blood is able to flow into the atria, atria contract to push blood into ventricles, AV valves open, at the end ventricles contract and AV valves close (lub, S1)
systole
ventricles contract while ventricles relax and blood enters, semilunar valves open, at the end semilunar valves close because artery pressure is larger than ventricle pressure, (dub, S2)
heart rate/pulse
the number of times the diastole/systole cardiac cycle is repeated per minute
stroke volume (SV)
the amount of blood pumped with each systole
cardiac output (CO)
the total amount of blood pumped per minute, the product of stroke volume times heart rate
Frank-Starling mechanism
increase cardiac output by increasing the volume of blood entering the heart which stretches heart muscle and causes it to contract more forcefully
venous return
the return of blood to the heart by the venous cava
what are the two principal ways of increasing venous return?
increase the total volume of blood in the circulation (peeing less) or contraction of large veins can propel blood toward the heart (valves prevent backflow)
what is the difference between neurons and cardiac muscle cells?
cardiac muscle is a functional syncytium
syncytium
a tissue in which the cytoplasm of different cells can communicate via gap junctions which are found in intercalated disks (connections between cardiac and muscle cells) in the cardiac muscle, this is an example of an electrical synapse
cardiac conduction system
the action potential in the heart is transmitted from the atrial syncytium to the ventricular syncytium (which are two separate syncytia), transmission is delayed at the A-V node (located at the tricuspid valve, aka atrioventricular node)
fast sodium channels
involved in cardiac muscle action potential
slow calcium channels
involved in cardiac muscle action potential, stay open longer than do sodium channels and causes a plateau phase (phase 2)
T-tubules
involutions of the membrane of cardiac muscle cells to maximize entry of calcium from extracellular environment (sarcoplasmic reticulum also releases intercellular calcium) to cause contraction of actin-myosin fibres
contractility
strength of contraction of the heart
is the heart stimulated to contract by neuronal/hormonal influences?
NO, the sinoatrial node (SA node) at the outside of the top of the right atrium is the pacemaker of the heart, but neuronal/hormonal influences can change the rate and strength/contractility
outline the action potential of the SA node
phase 4 (slow inward sodium through leak channels contributes to unstable resting potential), once threshold reached, phase 0: depolarization (inward calcium through voltage gated channels, phase 3: repolarization (outward potassium through voltage gated channels)
how does the SA node transmit the action potential to the rest of the conduction cells in the heart?
by intercalated disks/gap junctions/electrical synapses
outline the action potential in a cardiac muscle cell
phase 0: depolarization (fast sodium voltage gated channels open, sodium influx)
phase 1: initial repolarization (sodium channels inactivate, potassium voltage gated channels open, potassium efflux)
phase 2: plateau (calcium voltage gated channels open and calcium influx results in equilibrium with potassium efflux from open potassium voltage gated channels)
phase 3: repolarization (calcium voltage gated channels close, potassium voltage gated channels still open, potassium efflux)
phase 4: resting potential (potassium channels close and resting membrane potential maintained by sodium/potassium ATPase and slow potassium leak channels)
internodal tract
special conduction pathway that allows for rapid transmission of action potential between the SA node and the AV node, faster transmission than rate of impulse travelling through the atria
at the AV node, the impulse is delayed slightly before passing to ventricles by what conduction pathway?
the AV bundle (bundles of His) which divides into right and left bundles branches, then into Purkinje fibers which allow the impulse the spread rapidly and evenly over both ventricles at the apex
what is the role of the ANS on the heart?
it regulates the rate of contraction
- parasympathetic nervous system contributes to vagus tone: continual inhibition of SA node depolarization (i.e. inhibits rapid automaticity)
- sympathetic nervous system directly innervates the heart and releases norepinephrine and epinephrine from medulla can also bind to receptors on cardiac muscle cell to stimulate heart rate and force of contraction
what are autonomic nervous system receptors regulating the heart?
in the aortic arch and carotid arteries (contain baroreceptors to monitor pressure)
hemodynamics
the study of blood flow
Ohm’s Law
summarizes relationship between pressure, output and resistance pressure gradient (change in pressure,mmHg)=Q (blood flow/cardiac output, L/min) * R (resistance)
what is the principal determinant of resistance?
the degree of constriction of arteriolar smooth muscle/precapillary sphincters/peripheral resistance
which portion of the nervous system controls the peripheral resistance?
the sympathetic nervous system which provides a basal level of pressure (adrenergic tone) by a constant level of norepinephrine released by postganglionic axons innervating precapillary sphincters, can also specifically divert blood away from one tissue to preferentially perfuse another tissue
systemic arterial pressure
force per unit area exerted by blood upon the walls of arteries, systolic pressure/diastolic pressure
systolic pressure
heard when systolic arterial pressure is higher than cuff pressure, the highest pressure that can occur in the circulatory system, attained as ventricles contract, between S1 and S2
diastolic pressure
when pulse can’t be heard, the lowest ARTERIAL pressure occurring at any time during the cardiac cycle, between S2 and next S1 as ventricles are filling with blood
what is the pressure at the vena cava?
approximately 0 mmHg
pulse pressure
the difference between systolic and diastolic pressures
what is used to measure blood pressure?
sphygmomanometer
local autoregulation
mechanism whereby certain metabolic wastes have a direct effect on arteriolar smooth muscle and causes to relax, this allows extra tissue perfusion and automatic vasodilation, the principal determinant of coronary blood flow
what are the components of blood (from least dense to most dense)
plasma (54%) - water, electrolytes, nutrients, hormones, wastes, plasma proteins, lipoproteins
leukocytes (1%) - white blood cells and platelets (formed elements)
hematocrit (45%) - formed elements
plasma
the liquid portion of blood
formed elements
the cellular elements of blood
what is the principal blood buffer?
bicarbonate
what are the plasma proteins?
albumin (essential for maintenance of oncotic pressure), immunoglobulins (antibodies), fibrinogen (blood clotting, hemostasis)
lipoproteins
large particles consisting of fat, cholesterol, and carrier proteins, functions to transport lipids in the bloodstream
urea
principal metabolic waste product, a breakdown product of amino acids, a carrier of excess nitrogen
what is the breakdown product of heme?
bilirubin
where do all formed elements of the blood develop from?
bone marrow stem cells
serum
plasma without fibrinogen
erythropoeitin
hormone made in the kidneys that stimulates RBC production in the bone marrow
what happens to aged RBC’s?
degraded by phagocytes in the spleen and liver
outline characteristics of RBC’s
a cell with no nucleus or organelles, uses ATP by performing glycolysis, 120 day lifetime, concave shape, contains hemoglobin
hemolytic disease of the newborn/erythroblastosis fatalis
Rh+ baby’s blood mixes with Rh- mother’s blood, if next baby is Rh+, mother’s blood will contain anti-Rh antibodies that can cross the placental barrier and clump or destroy baby’s RBC’s. treatment: injection of mother at the time of birth with anti-RH antibodies to prevent sensitization of mother to Rh
what are the six types of leukocytes?
monocytes: macrophage, lymphocytes: B cell, T cell, granulocytes: neutrophil, eosinophil, basophil
macrophage
phagocytose debris and microorganisms, amoeboid motility, chemotaxis
B cell
mature into plasma cell and produce antibodies
T cell
kill virus-infected cells, tumour cells, and reject tissue grafts, also controls immune response
neutrophil
phagocytose bacteria resulting in pus, amoeboid motility, chemotaxis
eosinophil
destroy parasites, allergic reactions
basophil
store and release histamine, allergic reactions
how are platelets formed?
fragmentation of megakaryocytes: large bone marrow cells
what is the function of platelets?
to form a platelet plug by aggregating at the site of damage to a blood vessel wall
fibrinogen is converted to:
fibrin (threadlike protein that forms a mesh to hold the platelet plug together) by thrombin which requires calcium for activation
how many molecules of oxygen can hemoglobin carry?
4, binds cooperatively
Bohr effect
factors including: decreased pH, increased partial pressure/concentration of CO2, increased temperature, stabilizes tense hemoglobin and reduces oxygen affinity (ie. oxygen is released and allowed to enter cell)
percent saturation
used to measure oxygen affinity, # of O2 molecules bound/# of O2 binding sites * 100%
how is carbon dioxide transported in the blood?
73% is converted to carbonic acid by carbonic anhydrase which exists in equilibrium with bicarbonate and protons, 20% sticks to hemoglobin (can be further stabilized by the Bohr effect), 7% dissolves (slightly water-soluble)
intercellular clefts
spaces between the endothelial cells that make up the capillary wall that facilitate exchange between blood and tissues, allows passage of nutrients, wastes, and white blood cells
how to gases enter capillaries
by simple diffusion
chylomicrons
a type of lipoprotein, i.e. lipid transport in the blood stream
how do fats in intestine enter bloodstream?
packaged into chylomicrons, enter lacteals (lymphatic vessels in intestinal wall), larger lymphatics, drains into vein in neck, enter liver and converted into another type of lipoprotein, carried to adipocytes for storage (i.e. completely bypasses hepatic portal vein)
lipemia
milky appearance of blood after a fatty meal
which two types of white blood cells can squeeze through intercellular clefts in the capillaries?
macrophages and neutrophils
what are two reasons that water tends to flow out of capillaries?
1) hydrostatic fluid pressure, high pressure causes water to squeeze out of capillaries
2) high osmolarity of tissues
oncotic pressure
albumin in plasma is too large and remains in plasma, provides osmotic pressure and draws most water back into capillaries
edema
swelling that is the result of water in the tissues
how do fluids, proteins, and white blood cells in the tissues return to the bloodstream?
by the lymphatic system
lymphatic system
one-way flow system which begins with tiny lymphatic capillaries that merge into larger lymphatic vessels (with valves) and further into large lymphatic ducts (with smooth muscle) and the thoracic duct (largest lymphatic duct) and ultimately empties into a large vein in the neck
what is the fluid in lymphatic vessels called?
lymph
lymph nodes
filters lymph, part of immune system and can initiate an immune response against foreign agents
