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Circulatory path of the blood

- blood pumped through aorta - branch into smaller arteries - branch into smaller arterioles - branch into smaller capillaries.

Blood from capillaries collected into venules - collect into larger veins - collect into superior and inferior vena cava - empties into right atrium

from right atrium - blood squeezed into right ventricle - which pumps blood through the pulmonary arteries to arterioles to capillaries of lungs - from capillaries of lung blood collects in pulmonary veins leading to heart - pulmonary veins empty into left atrium, which fills the left ventricle.
closed circulatory system
no openings for blood to leave the vessels.
the left ventricle contracts with the most force to propel the blood through the systemic circulation.
sinoatrial node (SA node)
the heart contractions are paced by a group of specialized cardiac muscle cells called the sinoatrial node (SA)

It spreads its contractions to surrounding cardiac muscles via electrical synapses made from gap junctions.

parasympathetic vagus nerve (PARASYMPATHETIC) innervates the SA node, slowing the contractions.

action potential from SA spreads around both aria and spreads to atrioventricular node (AV node) - slow to contract, creating a delay which allows the atria to finish their contraction.

From AV node, action potential moves down conductive fibers called bundle of His. (located in wall separating ventricles)

The action potential branhces out through the ventricular walls via conductive fibers called Purkinje fibers. -
vagus nerve
  • parasympathetic (rest & digest)
  • innervating heart and digestive system
  • slows rate of heart contractions and increases digestive activity in the intestines
Purkinje fibers
  • conductive fibers
  • from purkinje fibers, action potential is spread through gap junctions from one cardiac muscle to the next
  • in ventricles
  • allow for more unified and stronger contraction
  • elastic
  • greater blood pressure than veins
  • stretch as they are filled with blood
  • wrapped in smooth muscle (innervated by sympathetic nervous sys)
  • epinephrine is a powerful vasoconstrictor causing arteries to narrow
  • larger arteries have less smooth muscle per volume and are less affected by sympathetic innervation
  • small
  • wrapped by smooth muscle
  • can regular blood pressure or reroute blood by constriction and dilation
  • microscopic blood vessels
  • diameter approx single red blood cell
  • nutrient/gas exchange with any tissue (not vascular) takes place across capillary walls (not across arterioles or venules)
  • as blood flows into capillary - hydrostatic pressure > osmotic pressure and net fluid flow is out of capillary into interstitium
  • osmotic pressure constant
  • hydrostatic pressure drops from arteriole end to venule end --> net fluid flow into capillary
venules and veins
  • vein carries blood toward the heart
  • similar in structure to arterioles and arteries
  • act as reservoir for blood
  • to compensate for lower pressure, veins have valve system that prevents back flow of blood.
  • contraction of skeletal muscle helps blood move through veins, but major force is pumping of heart.
[!] dont confuse oxygenated blood wit definition of arteries. pulmonary arteries contain most deoxygenated blood in the body.
[!] blood pressure increases near the heart and decreases to its lowest in the capillaries.
[!] single artery is much bigger than capillary, so there are many capillaries. The total cross-sectional area of all capillaries is greater than cross sectional area of a single aorta.

Blood follows continuity equation (Q=Av) so velocity is greatest in the arteries where cross-sectional area is smallest, and velocity is lowest where cross-sectional area is greatest.
[!] althoug bernoulli's says that pressure is inversely proportional to cross-sectional area, this is not the case in blood vessels.

low pressure in arterioles, capillaries, venules, small veins, venae cavae (from systemic --> pulmonary) greatest blood pressure in aorta and drops until blood gets back into heart
cardiac action potential is spread from one cardiac muscle cell to the next via ion movement through gap junctions
  • skeletal muscle
  • innervated by phrenic nerve
  • upon contraction, expands chest cavity and creates negative gauge pressure
nasal cavity
  • filters, moistens, warms incoming air
  • coarse hair at front of cavity traps large dust particles
  • mucus secreted by goblet cells traps smaller dust particles
  • cilia moves mucus and dust back toward pharynx so it can be removed
pharynx (throat)
functions as passageway for food and air.
  • voice box
  • sits behind epiglottis (prevents food from entering trachea)
trachea (windpipe)
  • in front of esophagus
  • trachea splits into right and left bronchi before entering lungs
  • brochus branches to become bronchioles
  • bronchioes terminate in grape-like alveoli
  • from each alveolus, oxygen diffuses into capillary where it is picked up by red blood cells
  • carbon dioxide released from red blood cells into alveolus and expelled in inhalation
job of respiratory system
  • deliver oxygen to the blood and expel CO2
microtubules in respiratory track
  • microtubules are found in cilia, which are found in respiratory tract, fallopian tubes, and ependymal cells of spinal cord --> problem in microtubule production might result in a problem in breathing (or fertility or circulation of cerebrospinal fluid)
  • 98% of oxygen in the blood binds rapidly and reversible with protein hemoglobin inside erythrocytes forming oxyhemoglobin
  • 4 subunits with atom of iron where each of 4 iron atoms can bind with one O2 molecule
oxygen dissociation curve
  • as O2 pressure increases, O2 saturation of hemoglobin increases
  • oxygen dissociation curve shifted to right (lowering of hemoglobin's affinity for oxygen) by an increase in carbon dioxide pressure, hydrogen ion concentration, or temperature.

CO2 carried by blood in 3 forms
  • physical solution
  • bicarbonate ion*
  • carbamino compounds (combined with hemoglobin)
CO2 carried as bicarbonate. Bicarbonate ion formation governed by enzyme:
carbonic anhydrase (inside the red blood cell and not in the plasma)
carbon dioxide dissociation curve
  • greater pressure of CO2, greater blood content of CO2
  • increasing breathing rate expels CO2 and raising pH of blood (ex: during acidosis)
effect of nitrogen on body
  • nitrogen diffuses into the blood but doesnt react with chemicals in the blood
  • as pressure increases with depth, more nitrogen diffuses into the blood
  • as divers come back up, pressure decreases and gas volume increases.
lymphatic system
  • collects excess interstitial fluid and returns it to the blood. (can elicit immune response if necessary).
  • open system
  • connective tissue
  • regulates extracellular environment of body by transporting nutrients, waste products, hormones, and even heat.
important proteins contained in blood plasma
  • albumin (transport fatty acids and steroids, also regulate osmotic pressure of blood)
  • immunoglobulins (
  • clotting factors

most plasma proteins formed in liver. important function is to act as a source of amino acids for tissue protein replacement.
plasma in which clotting proteins fibrinogen has been removed.
  • (red blood cells) - like bags of hemoglobin
  • deliver oxygen and remove CO2
  • do not reproduce/no organelles
  • most worn out red blood cells burst and are destroyed in the spleen and the liver.
  • (white blood cells) - contain organelles
  • do not contain hemoglobin
  • protect body from foreign invaders
all blood cells differentiate from same type of precursor, a stem cell residing in bone marrow

granulocytes - white blood cells (part of innate immune response)
granular leukocytes (short life span) and agranulocytes (live a long time) because granular function nonspecifically whereas agranulocytes work against specific agents of infection (in case it returns)
  • small portions of membrane-bound cytoplasm torn from megakaryotes
  • like tiny cells w/o nucleus
  • contain actin and myosin, can make protaglandins and enzymes
involes many factors starting with platelets and includes plasma proteins prothrombin and fibrin to form blot clots.
leukocyte composition in the blood:
(from largest % - smallest)
  • neutrophils
  • lymphocytes
  • monocytes
  • eosinophils
  • basophils
innate immunity
  • skin
  • stomach acid/digestive enzymes
  • phagocytotic cells
  • chemicals in blood
injury to tissue results in inflammation,including:
  • dilation of blood vessels,
  • increased permeability of capillaries,
  • swelling of tissue cells, and
  • migration of granulocytes and macrophages to inflammed area.
2 types of acquired immunity:
1. humoral or B-cell immunity
2. cell-mediated or T-cell immunity
humoral/B-cell immunity
  • promoted by B lymphocytes
  • B lymphocytes mature and differentiate in bone marrow and liver
  • each B lymphocyte is capable of making a single type of antibody or immunoglobulin which is displayed on the membrane and recognizes an antigen
  • if a B lymphocyte antibody contacts a matching antigen the B lymphocyte, assisted by a helper T cell differentiates into plasma cells and memory B cells.
  • antibodies may cause antigenic substances to agglutinate or precipitate.
  • primary response: first time the immune system is exposed to an antigen
  • secondary response: re-infection, faster and more potent effect
  • humoral immunity is effect against bacteria, fungi, parasitic protozoans, viruses, blood toxins
Cell-mediated immunity/T-cell immunity
  • involves T-lymphocytes (mature in thymus)
  • have antibody-like protein at surface that recognizes antigens but never make free antibodies
  • T-lymphocytes not destroyed differentiate into helper T cells, memory T cells, suppressor T cells, and killer T cells.
  • effective against infected cells
helper T cells
assist in activating B lymphocytes as well as killer and suppressor T cells (cells attacked by HIV)
Memory T cells
similar function to memory B cells. play a negative feedback role in immune system.
Killer T cells
bind to antigen-carrying cell and release protein puncturing antigen-carrying cell

can attack many cells because they do not phagocytize their victims.
[!] spleen destroys old, worn out red blood cells
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