Exchange of materials
•	Animal cells exchange material across their cell membrane
•	fuels for energy 
•	nutrients 
•	oxygen 
•	waste (urea, CO2)
•	If you are a 1-cell organism that’s easy!
•	If you are many-celled that’s harder
Overcoming limitations of diffusion
•	Diffusion is not adequate for moving material across more than 1-cell barrier
In circulation…
•	What needs to be transported
•	nutrients & fuels
•	from digestive system
•	respiratory gases
•	O2 & CO2 from & to gas exchange systems: lungs, gills
•	intracellular waste
•	waste products from cells
•	water, salts, nitrogenous wastes (urea)
•	protective agents
•	immune defenses
•	white blood cells & antibodies
•	blood clotting agents
•	regulatory molecules
•	hormones
Circulatory systems
•	All animals have:
•	circulatory fluid = “blood”
•	tubes = blood vessels
•	muscular pump = heart
Open circulatory system
•	Taxonomy
•	invertebrates
•	insects, arthropods, mollusks
•	Structure
•	no separation 
between blood & 
interstitial fluid 
•	hemolymph
Closed circulatory system
•	Taxonomy
•	invertebrates
•	earthworms, squid, octopuses
•	vertebrates
•	Structure
•	blood confined to vessels & separate from interstitial fluid
•	1 or more hearts
•	large vessels to smaller vessels
•	material diffuses between vessels & interstitial fluid
Vertebrate circulatory system
•	Adaptations in closed system
•	number of heart chambers differs
Evolution of vertebrate circulatory system
Evolution of 4-chambered heart
•	Selective forces
•	 body size
•	protection from predation
•	bigger body = bigger stomach for herbivores
•	endothermy
•	can colonize more habitats 
•	flight
•	decrease predation & increase prey capture
•	Effect of higher metabolic rate
•	greater need for energy, fuels, O2, waste removal
•	endothermic animals need 10x energy
•	need to deliver 10x fuel & O2 to cells
Vertebrate cardiovascular system
•	Chambered heart
•	atrium = receive blood
•	ventricle = pump blood out
•	Blood vessels
•	arteries = carry blood away from heart
•	arterioles
•	veins = return blood to heart
•	venules
•	capillaries = point of exchange, thin wall
•	capillary beds = networks of capillaries

Arteries: Built for high pressure pump
•	Arteries 
•	thicker walls 
•	provide strength for high pressure pumping of blood
•	narrower diameter
•	elasticity 
•	elastic recoil helps 
maintain blood 
pressure even 
when heart relaxes
Veins: Built for low pressure flow
•	Veins
•	thinner-walled 
•	wider diameter 
•	blood travels back to heart 
at low velocity & pressure
•	lower pressure
•	distant from heart
•	blood must flow by skeletal muscle contractions when we move 
•	squeeze blood through veins
•	valves
•	in larger veins one-way valves 
allow blood to flow only toward heart
Capillaries: Built for exchange
•	Capillaries
•	very thin walls 
•	lack 2 outer wall layers 
•	only endothelium 
•	enhances exchange across capillary
Controlling blood flow to tissues
•	Blood flow in capillaries controlled by 
pre-capillary sphincters
•	supply varies as blood is needed
•	after a meal, blood supply to digestive tract increases
•	during strenuous exercise, blood is diverted from digestive tract to skeletal muscles
•	capillaries in brain, heart, kidneys & liver usually filled to capacity
Exchange across capillary walls
Fluid & solutes flows out of capillaries to tissues due to blood pressure
•	 “bulk flow”
Lymphatic system
•	Parallel circulatory system
•	transports white blood cells
•	defending against infection
•	collects interstitial fluid & returns to blood
•	maintains volume & protein concentration of blood
•	drains into circulatory system near junction of vena cava & right atrium
Lymph System
Mammalian
circulation
Mammalian heart
Coronary arteries
Heart valves
•	4 valves in the heart
•	flaps of connective tissue
•	prevent backflow
•	Atrioventricular (AV) valve 
•	between atrium & ventricle
•	keeps blood from flowing back 
into atria when ventricles contract
•	“lub”
•	Semilunar valves
•	between ventricle & arteries
•	prevent backflow from arteries into ventricles while they are relaxing
•	“dub”
Lub-dub, lub-dub
•	Heart sounds 
•	closing of valves
•	“Lub”
•	recoil of blood against 
closed AV valves
•	“Dub”
•	recoil of blood against 
semilunar valves
•	Heart murmur
•	defect in valves causes hissing sound when stream of blood squirts backward through valve
•	Mitral valve prolapse (MVP) is the most common condition of the heart valves. Some studies show it affects 6% of the population.
Cardiac cycle
•	1 complete sequence of pumping
•	heart contracts & pumps
•	heart relaxes & chambers fill 
•	contraction phase
•	systole
•	ventricles pumps blood out
•	relaxation phase
•	diastole
•	atria refill with blood
Measurement of blood pressure
•	High Blood Pressure (hypertension)
•	if top number (systolic pumping) > 150
•	if bottom number (diastolic filling) > 90

Blood & blood cells
•	Blood is a tissue of cells in a fluid
•	plasma = fluid (55% of volume)
•	ions (electrolytes), plasma proteins, nutrients, waste products, gases, hormones
•	cells (45% of volume)
•	RBC = erythrocytes
•	transport O2
•	WBC = leukocytes
•	defense
•	platelets
•	blood clotting
Components of Blood tissue
Plasma proteins
•	Synthesized in liver & lymph system
•	fibrinogen
•	clotting factor
•	blood plasma with clotting factors removed = serum
•	albumins
•	buffer against pH changes, help maintain osmotic balance & blood’s viscosity
•	globulins
•	immunoglobins = antibodies
•	immune response to combat foreign invaders 
Blood cell production
Red blood cells
•	Function
•	O2 transport
•	Structure
•	small biconcave disks
•	large surface area
•	lack nuclei & mitochondria
•	more space for hemoglobin
•	iron-containing protein that transports O2
•	generate ATP by anaerobic respiration 
•	only last 3-4 months (120 days) 
•	ingested by phagocytic cells in liver & spleen
•	~3 million RBC destroyed each second
•	produce ~3 million RBC every second to replace
Hemoglobin 
•	Protein with 4° structure
•	O2 carrier molecule
Control of heart
•	Evolution of system to control heart beat
•	timely delivery of O2 to cells is critical 
•	cells of cardiac muscle are “self-excitatory”
•	contract without any signal from nervous system
•	each cell has its own contraction rhythm, so have to coordinate them
•	cells synchronized by sinoatrial (SA) node
•	“pacemaker”
•	cells in wall of right atrium
•	sets rate & timing of cardiac cell contraction
SA node & Electrical signals
•	Pacemaker generates electrical impulses across heart
•	signal also transmitted to skin = EKG or ECG
Regulation of heart rate
•	Physiological cues affect heart rate
•	nervous system 
•	speed up pacemaker 
•	slow down pacemaker 
•	heart rate is regulated by opposing actions of these 2 sets of nerves
•	hormones
•	epinephrine from adrenal 
glands increases heart rate
•	body temperature
•	activity
•	exercise, etc.
Regulation of blood volume / pressure
•	Hormone regulation
•	ADH (antidiuretic hormone)
•	from pituitary
•	causes kidneys to reabsorb more water
•	aldosterone
•	from adrenal gland
•	causes kidneys to reabsorb Na+ & water
•	atrial natriuretic hormone
•	from heart (right atrium)
•	promotes excretion of Na+ in urine
•	nitric oxide
•	from blood vessel cells
•	dilates blood vessels
•	nitroglycerin & Viagra release nitric oxide
Blood clotting
Powerful evolutionary adaptation
•	emergency repair prevents excessive blood loss
Cardiovascular disease
•	Leading cause of death in U.S. 
•	plaques develop in inner wall of arteries
•	narrowing channel
•	stroke, heart attack, atherosclerosis, arteriosclerosis, hypertension (high blood pressure)
•	tendency inherited, but other risk factors: 
smoking, lack of exercise, obesity, diet rich in fat
Cardiovascular health (U.S. 2001)
Heart Disease
Women & Heart Disease
•	Heart disease is 3rd leading cause of death among women aged 25–44 years & 2nd leading cause of death among women aged 45–64 years.
Thermoregulation
•	Vasodilation & vasoconstriction
•	adjusts blood flow
•	evaporative cooling
Temperature management