circulation of blood

1. Circulatory Systems I

2. Primary Functions
 Transport oxygen and nutrients to
actively metabolizing tissues.
 Remove carbon dioxide and other waste
products from tissues.
 Transport signaling molecules and
immune cells throughout the body.

3. Diffusion
 Unicellular organisms and some small
metazoans lack cardiovascular systems.
 Rely on diffusion to transport molecules.
 Slow across long distances.

4. Diffusion

5. Bulk Flow
 Limitation on the rate of diffusion so
larger animals move fluids through their
body by a process called bulk flow
 Occurs within a series of chambers &
tubes.
 Faster across long distances than diffusion

6. Bulk Flow
 One way valves ensure unidirectional flow
through the system.

7. Circulation Time
Mammal Body Mass
(kg)
Circulation
Time (sec)
Elephant 4000 140
Horse 700 90
Human 70 50-60
Rat 0.2 12
Shrew 0.003 4
Exercising Human = 12 seconds
Exercising Shrew = 1 second

8. Circulatory Systems
 3 Main Components:
1. 1≤ pumps apply force to drive fluid flow.
2. A system of tubes, channels, or spaces through
which the fluid can flow.
3. A fluid that circulates through the system.
 Substantial diversity among animals

9. Pumping Structure
 3 main types:
◦ Contractile Chamber
◦ External Pump
◦ Peristaltic Contraction

10. Pumping Structures

11. Pumping Structures
 Chambered hearts:
◦ Chamber(s) that circulatory fluid first
enters is/are called atrium/atria
◦ Function as both reservoirs and pumps.
◦ Fluid flows from an atrium into a
muscular chamber called a ventricle.
◦ Functions as primary pump.

12. Pumping Structures
 Skeletal muscles can be used to develop
pressure gradients.

13. Pumping Structures
 Tube-like hearts found in some
invertebrates move blood by peristalsis.

14. Circulatory Systems
 Open Circulatory Systems
 Closed Circulatory Systems

15. Open Circulatory Systems
 Circulatory fluids flow through open
spaces called sinuses.
 Sinuses allow circulatory fluids to make
direct contact with tissues.
 Circulatory fluids therefore mix with
extracellular fluids.

16. Closed Circulatory Systems
 Circulatory fluids flow through enclosed
blood vessels.
 Blood vessels have specialized lining that
separates circulatory fluids from tissues.
 Complete separation of circulatory fluid
and extracellular fluid.

17. Circulatory Fluids
 Interstitial Fluid
◦ Extracellular fluid directly bathes tissues
 Blood
◦ Closed circulatory systems.
 Hemolymph
◦ Open circulatory systems

18. Diversity of Circulatory Systems

19. Sponges, Cnidarians and Flatworms
 All lack a true circulatory system.
 All have mechanisms for propelling fluid
around their bodies.
 The bulk flow of fluids is part of a
combined respiratory, digestive, and
circulatory system.

20. Sponges, Cnidarians and Flatworms
 The bulk flow of fluids is part of a combined
respiratory, digestive, and circulatory system.

21. Annelids
 Most have closed
circulatory systems
◦ Polychaetes = tube worms
 Some have open circulatory
systems
◦ Oligochaetes = earth worms
 Series of small blood vessels
connect large dorsal and ventral
blood vessels

22. Mollusks
 Most have open circulatory systems
◦ All have hearts or contractile organs
◦ Some have blood vessels

23. Mollusks:
Squid, Octopuses, & Cuttlefish
 Have completely closed circulatory systems.

24. Mollusks: Squid & Octopuses
 Have 3 muscular chambered hearts:
 The systemic heart pumps oxygenated
blood to the body.
 Deoxygenated blood flows into the two
branchial hearts that pump blood through
the gills.
 From the gills the oxygenated blood flows
back into the systemic heart.

25. Arthropods
 All have open circulatory systems
◦ Almost all have 1≤ hearts and some BVs.

27. Vertebrates
 All have closed circulatory systems.
◦ Blood remains within blood vessels
throughout all points of circulation.
 Advantages:
◦ Ability to generate high pressure and flow
◦ Ability to control and direct blood flow to
specific tissues

28. Blood
 Circulatory fluid in closed systems.
 Plays many roles:
◦ Provide constant internal environment
◦ Transports – nutrients, oxygen, wastes
products, immune cells, and signaling
molecules around the body.

29. Composition ofVertebrate Blood

30. Composition ofVertebrate Blood
 Blood Plasma:
◦ mostly water (93% by volume)
◦ contains dissolved proteins, glucose, clotting
factors, dissolved ions, hormones and CO2
 White Blood Cells = Leukocytes
◦ Immune System Cells
 Red Blood Cells (RBCs) = erythrocytes
◦ Main Function = transport of oxygen

31. Red Blood Cells
 Mammalian RBCs lack nuclei, mitochondria,
and other organelles including ribosomes.
 Most mammalian RBCs are shaped like
biconcave disks.
 Contain oxygen high concentration of binding
protein hemoglobin (Hb).

32. Red Blood Cells
 Hb: increases the maximum amount of
oxygen that blood can carry by 50x
 When you increase Hb you increase you
oxygen storage capacity of blood and
your ability to deliver oxygen to tissues.

33. Red Blood Cells
 Hematocrit (HCT) = % blood that is
made up of erythorcytes (RBCs)
 Varies substantially among vertebrates
(20-65%)
 Acclimation of humans to high altitude
causes an increase in HCT.

34. Circulatory Plan ofVertebrates

35. Circulatory Plan ofVertebrates
 Arteries: carry blood away from heart
 Arterioles: arteries branch into arterioles
 Capillary Beds: dense networks of thin
walled capillaries
 Venules: capillaries coalesce into venules
 Veins: venules coalesce into veins, which
return blood to the heart

36. BloodVessels - Wall Structure
 Blood vessels are hollow and tubular
◦ Lumen = hollow area
 Composed of up to 3 Layers:
◦ Tunica Intima
◦ Tunica Media
◦ Tunica Externa

37. BloodVessels - Wall Structure
 Tunica Intima – inner-most layer
◦ Inner lining called the vascular endothelium
 Tunica Media – middle layer
◦ Composed of smooth muscle and elastin
◦ Vasodilatation and vasoconstriction
 Tunica Externa – outer-most layer
◦ Composed of collagen fibers
◦ Support and reinforce blood vessel

39. BloodVessels - Wall Thickness
 Arteries: large diameter & thick-walled
◦ Aorta - highly elastic with a thick tunica
externa.
◦ Arteries farther from heart have a thicker
tunica media and are highly muscular.

40. BloodVessels - Wall Thickness
 Arterioles: thinner walls and lack
extensive tunica externa.
◦ Larger arterioles - extensive tunica media
◦ Smaller arterioles = single layer of smooth
muscle around the endothelium
 allows for vasoconstriction and vasodilatation

41. BloodVessels - Wall Thickness
 Capillaries: lack tunica media and
externa.
 Very small diameter
 Extremely thin walled:
◦ composed of a single sheet of epithelial cells.
◦ Allows substances to pass between the blood
and tissues.

42. Capillaries
 Substances can move across walls by:
◦ Diffusion – lipid-soluble substances
◦ Vesicle transport – proteins
◦ Paracellular pathway – small molecules like
water and ions can pass through pores
between cells of the capillary walls.

43. Capillaries – Tunica Intima
 Continuous capillaries:
◦ seal between cells not usually complete allowing
fluids and small molecules to pass.
 Fenestrated capillaries:
◦ Cells of vascular endothelium have many pores.
Passage of small molecules and fluids is easy.
 Sinusoidal capillaries:
◦ Most porous of all capillaries.
◦ Allows proteins to move across capillary wall.

45. BloodVessels - Wall Thickness
 Capillaries empty into venules, which lead
to veins that return blood to the heart.
 Vein usually has a thinner wall and larger
lumen than a similarly sized artery.
 Thin tunica media, thick tunica externa.