Circulatory System

Overall components are blood, blood vessels, and heart

Overall function is to transport nutrients, gases, hormones, waste, immunity, and temperature regulation

Circulatory System

Ontogeny & PhylogenyFirst system to be functional in

developmentSimilar embryology in all vertebratesIndividual variation within species

Blood

Plasma (serum is plasma minus clotting factors)

Formed Elements = CellsErythrocytesRed Blood CellsHave hemoglobin pigment to carry oxygenNeed iron for hemoglobin synthesis

Blood

LeukocytesFunction in immunity, antibody productionPhagocytosis

Blood

PlateletsClotting of blood

Blood

Hemopoiesis = Formation of blood cellsSites in adult include liver, kidney, spleen

and red bone marrow depending on classBlood islands – located in wall of yolk sac

is earliest site of hemopoiesis in vertebratesHemocytoblast = stem cell

Heart

Develops early from splanchnic hypomereFunctional by 30 hours in chick (21 d

incubation)Functional by 4 weeks in humans (280 d

gestation)

Heart Wall

Endocardium – inner, smooth liningMyocardium – striated cardiac m.,

intercalated discsEpicardium – outermost layer

Heart

Parietal pericardium – part of pericardial sac that encloses the heart

Visceral pericardium = epicardiumPericardial cavity – between parietal &

visceral pericardium

Gill Breathing Fish Heart

Single circuit pump with 4 chambersSinus venosus – pacemaker (through

reptiles)AtriumVentricleConus arteriosus (trunk)

Gill breathing fish heart

AV valve – one way valve between atrium & ventricle to prevent backflow

Semilunar valve – one way valve between ventricle & conus arteriosus to prevent backflow

Lungfish & Amphibians

Two circuit heartDivisions to divide heart into oxygenated

and deoxygenated sidesInteratrial septum (partial or complete)Interventricular septum/Ventricular

trabeculae – partialSpiral valve – tries to divide conus

arteriosus

Amniote heart

More complete divisions of heart, 2 circuit heart

Two atria, two ventricles

Amniote Heart

Sinus venosus is the pacemaker through reptiles

Sinus venosus becomes the sinoatrial node in birds & mammals which is the pacemaker & is located in the wall of the RA

Pacemaker sets the pace for all heartbeats

Amniote heart

Interatrial septum is completeForamen ovale is an embyronic hole in

interatrial septum Auricle is an expansion of atria in mammals

onlyInterventricular septum is complete in most

Key Points

What do you suppose the function of the auricle is?

Key Points

Why would the foramen ovale be a necessary structure in the mammalian fetus?

Key Points

Summarize the difference between a single circuit and a double circuit pump.

What anatomical features support the heart being a double circuit pump?

Amniote heart

AV valves are bicuspid & tricuspid in mammals

Semilunar valves between ventricles and trunks

Amniote heart

Fate of conus arteriosusThree trunks in reptilesTwo trunks in birds and mammals

Key Points

The conus arteriosus becomes trunks. Are trunks arteries or veins?

Name the two trunks in birds and mammals.

Circulation between lungs and heart

Pre/Postcava RA RV Pulmonary trunk – arteries Lungs LA LV Aorta Systemic circulation

Key Points

Without looking, trace the blood flow from pre/post cavas through heart, to lungs, back to heart to aorta.