circulatory system

Right atrium:

Receives

deoxygenated blood from the

superior vena cava and

inferior vena cava

Superior vena cava:

Collects

deoxygenated blood from the

chest, arms, head, and neck

Inferior vena cava:

Collects

deoxygenated blood from the abdomen, pelvis, and lower limbs

Right atrioventricular (AV) valve (tricuspid valve):

Allows

blood to pass from the right atrium to the right ventricle

right ventricle

pumps

deoxygenated blood into the

pulmonary artery

Pulmonary artery:

Carries deoxygenated blood to the lungs

Pulmonary semilunar valve:

Allows blood to pass from the

right ventricle into the pulmonary artery

Right ventricular contraction:

Tricuspid valve closes and the

pulmonary semilunar valve

opens

Allows for ventricular

emptying without

backflow into the atrium

Right ventricular relaxation:

Tricuspid valve opens and the pulmonary semilunar valve closes

Allows for ventricular filling from the atrium only without

backflow from the pulmonary artery

Left atrium:

Receives

oxygenated blood from the

pulmonary vein

Pulmonary vein:

Carries

oxygenated blood from the

lungs to the heart

Left atrioventricular (AV)

valve (bicuspid or mitral

valve):

Allows oxygenated blood to flow from the left atrium to the left

ventricle

Left ventricle:

Pumps oxygenated blood into the

aorta

• Most muscular chamber

of the heart

● Contraction will generate

more pressure than that

of the right ventricle

Aorta:

Directs oxygenated blood from the heart into the

systemic circulation

Pulmonary circulation:

Transports deoxygenated blood from the heart to the

lungs via the pulmonary artery and oxygenated blood from the lungs back to

the heart via the pulmonary veins

Pulmonary circulation:

Right atrium tricuspid valve right ventricle

pulmonary semilunar valve pulmonary artery lungs pulmonary vein left atrium

Systemic circulation:

Transports oxygenated blood from the heart to the

body via the aorta and deoxygenated blood from the body to the heart via the

superior and inferior vena cava

Systemic circulation:

Left atrium: bicuspid/mitral valve left ventricle

aortic semilunar valve aorta body superior and inferior vena cava right atrium

Cardiac Rhythm

The heart contracts and relaxes in a rhythmic pattern in order to ensure the most

efficient transfer of blood

● Proper relaxation of a heart chamber allows

for maximal filling

● Proper contraction after filling allows for

maximal ejection of blood

Cardiomyocytes:

Heart muscle cells

Cardiac Cycle requires…

The cardiac cycle requires an electrical current to begin

at an autonomous pacemaker and travel through the

heart, stimulating muscle contraction along the way

Sinoatrial (SA) node:

The pacemaker of the heart

● Located in the upper wall of the right atrium

● Possesses the greatest automaticity; most likely to reach

threshold and initiate an action potential

● Simultaneously stimulates contraction of the right and left atria

● Transmits the electrical signal to the AV node

Atrioventricular (AV) node:

Briefly delays the electrical current coming from the SA node

Delay allows the ventricles time to fill before

the signal to contract is sent to the ventricles

● Located in the lower wall of the right atrium

● Passes electrical signal to the Bundle of His

Bundle of His:

Passes the signal from the AV node

to the bundle left and right bundle branches

Purkinje fibers:

Receive electrical signal from the

bundle branches and stimulate ventricular contraction

Intercalated disks:

Cell junctions between cardiomyocytes

● Provide physical connection as well as electrical connection (gap junctions)

● Gap junctions allow the contraction signal to be propagated in a coordinated,

rhythmic fashion

Systole:

Ventricular ejection phase

● The ventricles contract, increasing

the pressure within the chambers

until it is enough to push open the

semilunar valves

● Blood enters the pulmonary

and systemic arteries

● Arterial blood pressure is at its highest during systole

● The artery with the highest pressure during systole is the aorta

diastole

ventricular filling phase

relaxes, allowing a maximal

amount of blood to fill each

chamber from the atria

● Arterial blood pressure is at its

lowest point during diastole

Cardiac output:

The volume of blood being

pumped by the heart per minute

Heart rate:

How fast the heart beats

(beats/minute)

Stroke volume:

The volume ejected per single beat

● Calculated by subtracting end systolic volume from end

diastolic volume

Blood vessels:

Transport blood to and from

the heart

● Help to form a closed circulatory system

with the heart

Arteries:

Transport blood away from the heart

● Pressure is highest in the arteries due to the hydrostatic

pressure of the heart

● Carry oxygenated blood in the systemic circulation

● Carry deoxygenated blood in the pulmonary circulation

Arterioles:

Branches off of arteries with

smaller diameters than their parent arteries

● The greatest drop in blood pressure is

when going from arteries to arterioles

Capillaires:

One-cell-thick branches off of

arterioles, connecting the arterial and venous circulations

● Exchange gases and nutrients by diffusion

● Body tissues: collect waste and CO2

, deposit O2

and nutrients

● Lungs: deposit CO2

, collect O2

Venules:

Intermittent vessel that transports

blood from the capillaries to the veins

Veins:

Transport blood toward the heart

● Venous circulation holds more blood than

the arterial circulation and veins have

lower pressure than arteries

● Veins have valves (pocket or venous valves) to prevent

back flow in the low pressure system

● Contraction of the surrounding skeletal muscles is used

to generate the pressure necessary to push blood through

the veins

Blood plasma:

Fluid component of blood

● Composed of water, proteins,

nutrients, hormones, and other

water soluble substances

● Makes up most of the blood by

volume (~55% of blood volume)

white blood cells (leukocytes)

Cells of the immune system that

defend against infection ● The most common white

blood cell is the neutrophil

● White blood cells travel to

the site of infection through

the blood and enter the

infected tissue to mount a

response against the

invading pathogens

Platelets (thrombocytes):

Anucleate, cytoplasmic cell fragments responsible for

clotting

Megakaryocytes:

Large, platelet precursor cells that are bone marrow residents

Platelets

Release clotting factors that help to turn

fibrinogen into fibrin, which creates a net to

stop bleeding

Vitamin K:

Necessary cofactor for several

clotting factors; deficiency can lead to

bleeding disorder

● Considered immune cells, functioning in

innate immunity

● Together, leukocytes and thrombocytes make

up less than 1% of blood volume

Red blood cells (erythrocytes):

Responsible for transporting gases via hemoglobin

proteins, making up ~45% of blood volume

● Transport O2

from the lungs to the tissues and CO2

from the tissues to the

lungs

Mature red blood cells are anucleate in order to maximize the amount of space

available for carrying hemoglobin and oxygen, making them flexible

● Biconcave disk morphology

Blood clotting:

A protective mechanism meant to repair damage to blood

vessels and prevent extensive bleeding

● Tears in the blood vessels initiate the blood clotting cascade which

helps to “plug” the tear, sealing it off and preventing further leakage

● Blood clotting cascade as a positive feedback mechanism:

● Damaged tissues signal for platelet accumulation

● Each platelet then signals for the attraction and activation

of other platelets

Tissue damage:

A tear occurs in the blood

vessel wall, exposing structural collagen

Platelet activation:

Exposed collagen initiates

platelet adhesion and activation

Platelet plug:

Accumulation of aggregated platelets that initially plug

the tear

Release of clotting factors:

Activated

platelets release clotting factors that convert

prothrombin (inactive form) into thrombin

(active form)

Clot formation:

Activated thrombin converts

fibrinogen (inactive form) into fibrin (active

form)

Activated fibrin strands polymerize together, forming the

hemostatic plug

● Hemostatic plug: Blood clot made of fibrin meshwork and

attached platelets

RBC antigens

Red blood cells (erythrocytes) have antigens on their surface that determine their type

RBC antigens: Sugar and protein

identity marking molecules on cells

Type A:

RBCs have the A antigen

Type B:

RBCs have the B antigen

Type AB:

RBCs have both the A and B antigens

Type O:

RBCs have neither the A or B antigens

Agglutination:

Clumping together of red

blood cells and red blood cell antibodies

Rhesus factor:

Additional red blood cell surface marker

● Two phenotypes: Rh (+) and Rh (-)

● Rh (+) donors cannot give blood to Rh (-) recipients because

the foreign Rh antigens will promote an immune response

in the receiving

Universal donors:

o-

Universal acceptors:

ab+

Placenta:

Source of fetal nutrients from the

mother, delivered via the umbilical cord

Barrier for gas and nutrient exchange

Umbilical cord:

Houses the umbilical vein and

umbilical artery

Umbilical vein:

Carries oxygenated blood from the placenta to

the fetal heart

Umbilical artery:

Carries deoxygenated blood from the fetal

heart back to the placenta

Removes wastes and CO2

from the fetal circulation

Fetal Circulatory Shunts

Fetal lungs and liver are nonfunctional

and filled with fluid

● Fetal circulatory shunts are present to

compensate

Ductus venosus:

A duct connecting the

umbilical vein to the inferior vena cava

● Blood passing through this duct will

bypass the nonfunctional liver

Foramen ovale:

A hole connecting the

right and left atria

● Blood is allowed to flow from the

right atrium into the left atrium

● The right ventricle wants to pump

blood to the lungs, but the fetal

lungs are nonfunctional

● Blood passing through this duct

bypasses the pulmonary circulation

Ductus arteriosus:

A duct that connects

the pulmonary artery to the aorta

● Some blood is inevitably pumped by

the right ventricle into the

pulmonary artery

● Ductus arteriosus allows this blood

to still bypass the pulmonary

circulation

Fetal Circulatory Shunts

Fetal circulatory shunts are no longer

need at birth as lungs and liver become

functional

● The umbilical cord dries up and falls off

(or is removed surgically at birth)

● Closure of the ductus venosus, ductus

arteriosus, and foramen ovale

● Enable proper blood circulation to the lungs and liver

Erythroblastosis Fetalis

Circulation | Biology ● A disorder initiated by a Rh (-)

mother carrying a Rh (+) fetus,

which then becomes problematic

upon a second pregnancy with

another Rh (+) fetus

● Fetal Rh (+) blood enters the

maternal circulation during labor

Circulation | Biology ● The mother will develop anti-Rh

antibodies, but they will not harm

the first child

● During a second pregnancy with

another Rh (+) fetus, maternal

anti-Rh antibodies will attack the

fetal RBCs ● Antibodies are small enough

to cross the placenta

Lymphatic system:

A subsystem of the

circulatory system that

● Regulates fluid levels and

● Produces immune cells

● System components:

● Lymph nodes, lymph vessels, adenoids

(lymphatic tissue), spleen, thymus

Thymus:

Major immune center within the

lymphatic system

● Location of T cell lymphocyte maturation

Spleen:

Site of blood filtration within the

lymphatic system

● Filters blood for pathogens and recycles

old red blood cells

Hydrostatic and Oncotic Pressure

Pressure inside and outside of

capillaries will determines direction of

fluid flow

Hydrostatic pressure:

Pushes fluid

out of the blood vessels (arterial end)

and into the interstitial space

Pressure exerted by vessel fluid

Oncotic pressure:

Brings fluid back

into the capillary (venous end)

Type of osmotic pressure

Proteins on one side of a

membrane pull water across to that

side

● Protein concentrations are higher

in the blood than in the interstitium

● Blood protein oncotic pressure

pulls fluid back into capillaries

● Not all fluid is reabsorbed from the

interstitial space

lymph

consists of remaining fluid

in the interstitial space, bacteria,

fats, and proteins

Lymphatic capillaries:

Collect the lymph out of the interstitial space ● Merge to form larger vessels

that travel to the heart

lymph nodes

centers for the Lymph traveling to the heart is

filtered through lymph nodes

Lymphatic Vessels

Lymphatic vessels have no pressure, similar to veins

● Valves are also present to prevent backflow

● Lymph propulsion relies on:

● Contraction of surrounding skeletal muscle

● Contraction of smooth muscle

● Lymph propulsion is ultimately achieved via peristalsis

Lymph Volume

Relative solute concentrations on either side of a

membrane are determining factors of lymph volume

● Example:

● If there is a high protein concentration in the

blood relative to the interstitial space, then a large

amount of fluid will re-enter the blood vessel

● Only a small fluid volume will remain for lymph

● Therefore, increased blood solute concentration

decreases lymph volume by reducing leftover

interstitial fluid

Mature red blood cells, also known as erythrocytes lack…

lack a nucleus and most other organelles. The lack of organelles increases the room available for erythrocytes to store and transport hemoglobin and oxygen.

Viruses are not living cells and therefore rely on the cells they infect in order to replicate themselves. Because viruses depend on the use of host cell machinery to replicate, erythrocytes are invulnerable to viral infection.

Adipocytes

are a type of cell that stores lipids. They are predominantly found in adipose (fat) tissue and do not flow freely in the blood.

Lipids are transported in the blood within lipoproteins, which are complexes of lipids and proteins that solubilize the lipids. This allows them to move through the aqueous environment of the bloodstream. 

coronary arteries

Oxygenated blood is delivered to the heart via the coronary arteries. 

lymphatic system

The lymphatic system is not directly connected to the heart and, as a result, lacks a central pump to facilitate fluid movement. Instead, surrounding contracting skeletal muscles drive the movement of lymph through lymphatic vessels, which are similar to veins.

How does CO₂ predominately travel through the blood?

bicarbonate ion

ductus venosus

• shunt between the umbilical vein and the inferior vena cava

• bypasses the undeveloped liver

foramen ovale

• shunt between the right atrium to the left atrium

• bypasses the undeveloped lungs

ductus arterosius

shunt between the right and left atrium

bypasses the undeveloped liver