Simple Diffusion = net movement of particles from a region of higher concentration to a region of lower concentration, resulting from random motion

• Sponges
• Cnidarian gastrovascular cavity
• flatworms = thin, branched intestine
• nematode fluid body cavity
• nutrients, O2, waste move between cells and interstitial fluid that bathes cells

Circulatory system when animal several cells thick

• diffusion alone would be too slow, so circ system reduces diffusion distance
• O2, nutrients, waste, hormones, etc.
• Human cardivascular system: disease linked to high cholesterol and LDL’s. HDL’s protect.

Parts:

• blood - connective tissue of cells and fragments in fluid plasma
• pumping organ (heart)
• blood vessels or spaces for blood to move thru

Open Circulatory system = open-ended vessels, blood in sinuses

• Arthropods, most Mollusks
• hemolymph = blood and interstitial fluid, which are continuous
• Hemocoel = blood cavity made of sinuses, separate from coelom body cavity
• Hemocyanin = pigment that binds O2 to copper. Blue when oxygenated
• Mollusk heart -> open ended vessel -> gills. 2 atria, one ventricle
• Arthropod tubular heart -> arteriest -> sinuses -> openings in heart with one way valve. Movement moves blood. Accessory hearts at legs, wings.

Closed circulatory system = blood in vessel circuit

• Earthworm has 2 long vessels, laterals in each segment. Near head = 5 contractile vessels that pump. Hemoglobin dissolved in plasma
• Cephalopod = closed, with accessory hearts to pump after gills.
• Vertebrates have ventral, muscular heart, Blood, lymph, vessels, thymus, spleen, liver

Functions of vertebrate circ system:

Move nutrients, O2, metabolic waste, hormone

Maintain fluid balance, pH

Defense against microorganisms

Distribute heat (most from muscles)

Blood

I. Plasma, pale, yellowish fluid, 55% volume

• water, proteins, slats, gases, nutrients, waste, hormones....
• Changing equilibrium between blood and interstitial fluid, with exchange at capillaries
• fibrinogen protein in blood clotting
• Serum - plasma without clotting proteins
• alpha globulin proteins = hormones and their transporters
• beta globulins = move fats, cholesterol, vitamins, minerals
• gamma globulins = antibodies
• albumin protein important in osmotic pressure: proteins too big to leave vessel.
• Proteins also are acid=base buffers, keep pH 7.4

II. Red Blood Cells (RBC, erythrocytes)

• transport O2 (hemoglobin)
• most vert RBC have nuclei. Lost in mature mammal RBC
• flexible, biconcave disc with internal elastic framework
• high surface area: volume for diffusion of O2 and CO2.
• Form in red bone marrow of long bones, vertebrae, ribs, breastbone
• RBC lives 120 days, when old, phagocytes in liver and spleen remove and recycle proteins, bile, etc
• Erythropoietin hormone released by kidney when low O2 stimulates RBC production
• Anemia = deficiency in hemoglobin, weak, fatigued
• loss of blood ( hemorrhage)
• low production of hemoglobin, RBC (iron deficiency)
• increased destruction of RBC (hemolytic anemia)

III. White blood cells (WBC, Leukocytes)

• defend against bacteria and other microorganisms
• ameoboid movement: leave capillaries, mature in tissues
• formed in red bone marrow

Granular leukocytes have granules, large, lobed nuclei

• neutrophils = eat bacteria, dead cells. Granules = enzymes for digesting
• eosinophils = detoxify. Granules have peroxidase, oxidase. High with allergy, parasitic infection
• Basophils have histamine and heparine granules.
• Histamine dilates BV, increase capillary permeability. Released in allergy or when tissue injured
• heparine = anticoagulant

Agranular leukocytes no granules, kidney or round nuclei

• lymphocytes make antibodies or attach directly to bacteria or virus. Label for destruction
• Monocytes move into tissue, form large macrophages that eat bacteria, debris

WBC count increases with bacterial infection

• Differential divides WBC into type, may indicate problem
• Leukemia = cancer with high WBC w/in bone marrow
• anemia as RBC crowded out
• internal hemorrhaging, esp brain or bacterial infection cause WBC immature

IV. Platelets = bits of cytoplasm surrounded by membrane in mammal blood

• Thrombocytes in other vertebrates (oval cells)
• In mammals, megakaryocyte cell in bone marrow pinches off bits of cytoplasm into platelets
• Vessel cut: constrict to reduce blood loss
• Temporary clot as platelets stick to fibers of cut. Platelets release chemicals to attract, stick more platelets
• More permanenet clot forms at same time, with 30+ proteins involved.
• Hemophilia = genetic condition, lacking one clotting factor
• Liver makes protein prothrombin using vit K
• Clotting factors, etc, convert prothrombin to thrombin
• Thrombin coverts fibrinogen to fibrin protein
• Fibrin protein lays down net to trap blood cells, platelets and strengthen clot.

Vessels

Arteries away from heart

Arterioles = branches within organs

Capillaries = exchange

Venules = capillaries fuse into

Veins = back to heart

Heart

3 layers of blood vessel walls in artery, vein

• endothelium inside = 1 cell thick
• middle layer of connective tissue and smooth muscle
• Outer layer of connective tissue with elastic and collagen fibers
• Capillary = 1 cell thick, only endothelium, so exchange is across capillary wall, between or thru cells
• Smooth muscle in arteriole wall allows vasoconstriction / vasodilation to adjust pressure and volume
• Most blood to kidey, liver, brain unless nervous system input changes volume elsewhere
• Metarterioles link aterioles and venules, with capillaries branching off metarterioles
• Precapillary sphincter controls blood movement in capillary bed, too many capillaries in body for all to be filled with blood at same time. Blood flow only when needed.

Vertebrate evolution

Fish have 1 atrium and 1 ventricle

• Tissue -> thin sinus venosus -> atrium -> ventricle -> conus arteriosus -> gills -> body
• one circuit
• low pressure leaving gills, muscles in swimming help move blood thru body

Amphibians have double circuit of pulmonary and systemic circulation, 2 atria, one ventricle

• body -> sinus venosus -> right atrium -> ventricle -> lungs / skin in pulmonary circuit
• from lungs -> left atrium -> ventricle -> body in systemic sircuit
• Mixing of O2 poor and O2 rich blood minimized because one leaves heart before other arrives
• Don’t breathe constantly, so only send blood to lungs as needed.

Reptiles = double circuit, 2 atria, one ventricle with partial wall

• minimize mixing by timing, pressure flow
• crocodiles = full 4-chambered heart

Birds and mammals have full wall, 4 chambered heart

• sinus venosus becomes sinoatrial bode
• conus splits into aorta and pulmonary artery
• Blood passes theu heart twice, so higher blood pressure
• Rapid, efficient movement of materials, more O2 for endothermy
• Veins -> right atrium -> right ventricle -> pulmonary arteries -> lung capillaries -> pulmonary veins -> left atrium -> left ventricle -> aorta, arteries, arterioles, capillaries

Heart is about the size of your fist, right under breastbone

Pericardium = tough connective tissue sac around heart

• Endothelium on surface of heart and pericardium
• pericardial space between has fluid to reduce friction

Heart wall = muscle and collagen fiber framework

• Septum divides heart into right and left sides (interatrial and interventricular)
• Fossa ovalis is a depression in the septum between atria where connected in fetus
• Foramen ovale = hole in fetus to allw blood to skip the ventricles
• Gas exchange thru placenta, don’t need pulmonary circ to lungs.
• Auricle = small pouch on top of each atrium

Valves prevent backflow

• Tricuspid = right atrioventricular valve
• mitral valve or bicuspid valve is left AV valve
• Chordae tendinae = chords that hold valves in place (heart strings)
• Semilunar valves close exits at pulmonary artery and aortic artery
• Valve deformities: birth, rheumatic fever, syphilis

Heart beat

• Intercalated discs between cells have gap junctions, so action potential passes thru cells
• Entire atrial muscle contracts together and entire ventricular muscle contracts together
• Ca2+ involved in depolarization, longer action potential than skeletal muscle
• Pacemaker aka sinoatrial node initiates heartbeat from right atrium, Ca2+ channels open.
• Muscle fibers take action potential to atrioventricular node in lower right atrium. DELAY contraction of ventricles so atria finish contracting.
• From AV node to Purkinje fibers in AV bundle, which takes impluse to each ventricle.

Cardiac cycle = one complete heartbeat, about 70 / min

• Contraction = sytole
• Relaxation = diastole
• Pressure waves as ventricle contracts, blood into artery.
• Lub-dub = closure of valves, turbulence echoes across walls
• lub = AV valves closing (mitral and tricuspid
• dub = closing semilunar valves
• Heart murmur = hissing when semilunar valves injured

EKG = electrocardiogram

• p-wave = firing of SA node, depolarization of atria
• QRS complex = AV node firing and depolarization of ventricles
• T waves = repolarization of ventricles
• Heart block = impulse is delayed or blocked in transmission thru heart
• Artificial pavemakers take impulse to heart properly

Caridac output = volume of blood pumped by left ventricle into aorta in one minute

• stroke volume = from one beat
• CO = Stroke volume * number of beats / minute
• Stroke colume depends on venous return
• Starling’s law of the heart = greater amount of blood delivered to the heart by the veins, the more blood the heart pumps. Muscles stretch and contract with greater force
• Nervous and endocrine systems influence heart rate
• Sensory receptors in walls indicate blood pressure, message to cardiac center of medulla
• Parasymphathetic nerve release Ach, slows heart
• Sympathetic nerves release norepinephrin, increase heart rate. Beta blockers block norepi receptors, treat hypertension
• Adrenal glands release epi, norepi if stressed
• Fever increases heart rate

Blood pressure = force exerted by blood against walls of blood vessels

• cardiac output, blood volume, resistance to blood flow
• peripheral resistance caused by viscosity of blood and friction between blood and walls
• Small change in BV diameter = big change in blood pressure
• Normal 120/80. systolic / diastolic
• Hypertension - diastolic BP > 95 mm Hg, from increased resistance, wears out left ventricle
• Artery bloood pressure highest
• Veins have very low pressure, rely on muscle movement to push blood past one-way valves.
• Fall in blood pressure sympathetic nerves to BV cause vasoconstriction increase pressure
• If baroreceptor in heart wall, arteries stretched, message to brain, parasympathetic nervous system
• Renin hormone from kidneys causes formation of angiotensin from plasma protei. Vasoconstrictors.
• Aldosterone hormone increased by angiotensins, increase Na+ retention in kidney, increase blood volume

Pulmonary circulation

• from tissues to right atrium, right ventricle, pulmonary artery
• Pulmonary arteries are only arteries in body that carry oxygen poor blood.
• Pulmonary capillaries surrounde alveoli air sacs in lungs. Gas exchange across 1 cell of alveoli and 1 cell of capillary.
• Pulmonary veins take O2 rich blood back to left atrium

Sytemic circulation goes to tissues

• left ventricle into aorta
• coronary arteries to heart wall -> capillaries -> coronary veins -> coronary sinus dumps into right atrium. Heart attack = blocked artery
• carotid arteries to brain return in jugular veins -> superior vena cava
• Superior vena cava takes blood from brain, arms, upper body.
• Inferior vena cava takes blood from kidney, lower legs, liver, etc
• mesentery artery to intestine
• renal artery to kidney