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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.