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 & Phylogeny First system to be functional in development Similar embryology in all vertebrates Individual variation within species

Blood Plasma (serum is plasma minus clotting factors) Formed Elements = Cells Erythrocytes Red Blood Cells Have hemoglobin pigment to carry oxygen Need iron for hemoglobin synthesis

Blood Leukocytes Function in immunity, antibody production Phagocytosis

Blood Platelets Clotting of blood

Blood Hemopoiesis = Formation of blood cells Sites in adult include liver, kidney, spleen and red bone marrow depending on class Blood islands – located in wall of yolk sac is earliest site of hemopoiesis in vertebrates Hemocytoblast = stem cell

Heart Develops early from splanchnic hypomere Functional by 30 hours in chick (21 d incubation) Functional by 4 weeks in humans (280 d gestation)

Heart Wall Endocardium – inner, smooth lining Myocardium – striated cardiac m., intercalated discs Epicardium – outermost layer

Heart Parietal pericardium – part of pericardial sac that encloses the heart Visceral pericardium = epicardium Pericardial cavity – between parietal & visceral pericardium

Gill Breathing Fish Heart Single circuit pump with 4 chambers Sinus venosus – pacemaker (through reptiles) Atrium Ventricle Conus 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 heart Divisions to divide heart into oxygenated and deoxygenated sides Interatrial septum (partial or complete) Interventricular septum/Ventricular trabeculae – partial Spiral 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 complete Foramen ovale is an embyronic hole in interatrial septum Auricle is an expansion of atria in mammals only Interventricular 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 arteriosus Three trunks in reptiles Two 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.