1. Circulatory Systems in Animals

2. Basic Components of All Circulatory Systems
A fluid, blood, that serves as a medium of transport
A system of channels, or vessels, that conduct the blood throughout the body
A pump, the heart, that keeps the blood circulating

3. Types of Circulatory Systems
Open Circulatory System
example: arthropods and mollusks
2) Closed Circulatory System
example: earthworms, vertebrates

4. Open Circulatory System
Have an open space, the hemocoel
Vessels empty blood into and pick blood up from the hemocoel
Tissues within the hemocoel are bathed directly in the blood

6. Hemocoel
Blood Vessel
Blood

7. Closed Circulatory System
Blood is confined to the heart and a continuous system of blood vessels
Each body cell has a direct blood vessel connection

10. Functions of the Vertebrate Circulatory System
Transport of oxygen from lungs to tissues
Transport of carbon dioxide from tissues to lungs
Transport of nutrients from digestive system to all body cells
Transport of waste products from all body cells to the liver, then kidney

11. Functions of the Vertebrate Circulatory System
5. Distribution of hormones from gland to target organ
6. Regulation of body temperature by adjustments in blood flow
7. Prevention of blood loss by means of clotting
8. Protection of body from microbes by circulating white blood cells and antibodies

12. Evolution of Vertebrate Heart
Two distinctly different chambers:
1) atrium (pl. atria)
thin walls and very elastic
designed to collect blood from the body
2) ventricle
thick walls and very muscular
designed to pump blood to the body

13. Atrium
Ventricle

14. Evolution of Vertebrate Heart
Fish have a 2 chambered heart = one atrium and one ventricle
Amphibians and reptiles have a 3 chambered heart = two atria and one ventricle
Birds and mammals have a 4 chambered heart = two atria and two ventricles

15. Fish
Amphibian, Reptile
Bird, Mammal

16. Fish Circulatory System
Single loop circulatory system
Atrium collects blood from body
Atrium transfers blood to ventricle
Ventricle pumps blood to gills
Gills pick up oxygen and give off carbon dioxide
Blood travels to body cells and gives off oxygen and picks up carbon dioxide

17. Amphibian and Reptile Circulatory System
Two loop circulatory system
Right atrium collects low oxygen/ high carbon dioxide blood from body
Left atrium collects high oxygen/ low carbon dioxide blood from lungs
Both atria empty into the common ventricle
Deoxygenated and oxygenated blood mix in ventricle and is pumped to body and lungs

18. Bird and Mammal Circulatory System
Two distinct loops circulatory system
Right loop= pulmonary circulation
Left loop = systemic circulation
Deoxygenated blood is always kept separate from oxygenated blood
Low O2
High O2
Low O2
High O2

19. The Blood Vessels There are 3 types of blood vessels:
Arteries (and smaller arterioles)
Capillaries
Veins (and smaller venules)
Vein
Artery
Capillary

20. The Blood Vessels: ACV Arterioles Arteries Heart Capillaries Veins
Venules

21. Arteries and Arterioles
Carry blood under pressure away from the heart towards the capillaries
Middle tissue layer of arteries is thick smooth muscle
Lumen
Thick layer of smooth muscle

22. Arteries and Arterioles
Smooth muscle contractions regulate blood flow and blood pressure in arteries
Contraction of arteries and arterioles increases blood pressure
Relaxation of arteries and arterioles decreases blood pressure

23. Capillaries
Capillary wall
Lumen
Capillaries have cell walls one cell thick  easy diffusion of molecules between blood in capillaries and cells in body
CO2 O2
RBC
Body
Cell

24. Capillary Bed
While individual capillaries are small, capillaries form large capillary beds in tissues  very large total area which slows down blood flow  increases the rate of diffusion
Capillary Bed

25. Capillary Bed and Total Area

26. Blood Shunting in Capillary Bed
Body regulates the flow of blood through capillary beds
When precapillary sphincters are closed, blood is moved in bulk through a thoroughfare channel called the arteriovenous shunt
This prevents diffusion between blood in capillaries and cells in tissue

27. Blood Shunting in Capillary Bed
Example: after eating, precapillary sphincters in digestive system capillary beds are open while precapillary sphincters in muscle capillary beds are closed  priority is for the blood to pick up the nutrient molecules from digestive system

28. Veins and Venules
Veins (and smaller venules) drain blood from the capillaries and return it to the heart under low blood pressure
Veins have the same tissue layers as arteries, but have less smooth muscle in the middle layer  walls of a vein are thin in comparison to arteries

29. Veins and Venules

30. Connective Tissue
Smooth Muscle

31. Veins and Valves
Theoretically, because veins are thin walled and blood pressure is low in veins, blood should tend to move slowly through the veins
Actually, the flow of blood in the veins increases due to the presence of one-way valves in veins and skeletal muscle contraction around veins

32. Veins, Blood Pressure and Velocity

34. Cross-section of Vein

35. Summary of Blood Vessels
Artery
Capillary
Vein
Flow of Blood
From heart to capillaries
Diffusion between capillary and body tissue
From capillaries to heart
Blood Pressure
High
Low
Lowest
Smooth Muscle Layer
Thick
None
Thin
Valves
Yes

36. Summary of Blood Vessels
Artery
Capillary
Vein
Total Cross-sectional area
Low
High
Blood Velocity

37. The Human Heart
The human heart weighs between 200 to 425 grams and is a little larger than the size of your fist
The heart is located between your lungs in the middle of your chest, behind and slightly to the left of your sternum
The apex of the heart is oriented to the left side of the body
Right
Side
Left
Side

38. Rat Dissection
Left Side
Lungs
Heart
Liver
Lungs
Right Side
Diaphragm

39. Pericardium
A double-layered membrane sac called the pericardium surrounds the heart
The outer parietal pericardium surrounds the roots of your heart's major blood vessels and is attached by ligaments to your spine, diaphragm, and other parts of your body
The inner visceral pericardium is attached to the heart muscle
(myocardium)

40. Pericardium
A coating of fluid separates the two layers of membrane, letting the heart move as it beats, yet still be attached to your body
This space between the visceral and parietal pericardium is the pericardial cavity

41. Myocardium
The major portion of the heart is composed of cardiac muscle cells, collectively called the myocardium
Myocardium has a "stringy" look compared to skeletal muscle
Striated skeletal muscle cells are large and lie next to each other in more or less parallel bundles

42. Myocardium
Cardiac muscle cells are small, butted together at their ends, irregularly shaped, and have numerous blood vessels (BV) between them
Intercalated disks are specialized cell-to-cell adhesion/communications sites and are found only in cardiac muscle.

43. Heart Chambers Your heart has 4 chambers
The upper chambers are called the left and right atria ( atrium, singular) and have protruding appendages called auricles
The lower chambers are called the left and right ventricles

44. Heart Septum
A wall of muscle called the septum separates the left and right atria and the left and right ventricles  the right side of the heart is a pump for pulmonary circulation and the left side of the heart is a pump for systemic circulation
Left Ventricle
Right
Ventricle

45. Heart Valves
The heart has two types of valves: atrioventricular valves and semilunar valves
The tricuspid and mitral (or bicuspid) valves are atrioventricular valves
They have fibrous strands called chordae tendineae on their leaflets that attach to papillary muscles located on the respective ventricular walls
The papillary muscles contract during ventricular contraction and generate tension on the valve leaflets via the chordae tendineae to prevent the AV valves from bulging back into the atria  no back flow
The pulmonary and aortic valves are called semilunar valves and do not have chordae tendineae

46. Blood Flow Through the Heart
The right atrium receives deoxygenated blood from the body via the superior and inferior vena cava
Deoxygenated blood flows from the right atrium, across the atrioventricular tricuspid valve, and into the right ventricle
The right ventricle contracts and pumps deoxygenated blood to the lungs via the pulmonary artery
The semilunar pulmonary valve prevents back flow of the blood into the right ventricle

47. Blood Flow Through the Heart
Oxygenated blood returns to the heart from the lungs via four pulmonary veins that enter the left atrium
Oxygenated blood flows from the left atrium, across the atrioventricular mitral (or bicuspid) valve, and into the left ventricle
The left ventricle has a very thick muscular wall so that it can generate high pressures during contraction
Oxygenated blood from the left ventricle is pushed across the semilunar aortic valve and into the aorta for transport to the body

48. Human Circulatory System
Two distinct loops circulatory system
Right loop= pulmonary circulation
Left loop = systemic circulation
Deoxygenated blood is always kept separate from oxygenated blood
Low O2
High O2
Low O2
High O2

49. Heartbeat and Cardiac Cycle
When surgically removed from the body, the heart will continue to beat for several hours provided it is supplied with the appropriate nutrients and salts
This is possible because the heart possesses its own specialized conduction system and can beat independently even after being separated from its nerve supply
The extrinsic (arising external to the heart) nerve supply coming from the nervous system serves to modify and control the intrinsic (inherent to the heart itself) beating established by the heart

50. Heart Conduction System
Atrioventricular
Bundle
SA node
Inter-nodal
Fiber Bundle
AV node
Purkinje
fibers

51. Heartbeat and Cardiac Cycle
There are five basic components to the heart's intrinsic conduction system
(1) sinoatrial node (SA node)
(2) inter-nodal fiber bundle
(3) atrioventricular node (AV node)
(4) atrioventricular bundle
(5) Purkinje fibers

52. SA Node
The sinoatrial (SA) node is a small mass of specialized cardiac muscle situated in the upper dorsal surface of the right atrium
Because the SA node is able to initiate each beat of the heart, it is often referred to as the pacemaker of the heart
The excitation impulse occurs every 0.85 seconds  approximately 72 times per minute

53. SA Node
Excitation of the SA node sends a nerve impulse to: (1) the muscles of the atria causing them to contract (atrial systole) while the ventricles relax (ventricular diastole), and
(2) the AV node along the inter-nodal fiber bundle
Atrial systole takes 0.15 seconds of the 0.85 second cardiac cycle

54. AV Node
From the SA node, inter-nodal fiber bundles conduct the nerve impulse to the atrioventricular (AV) node
The AV node is located in the right atrium near the lower part of the interatrial septum
There is a short delay in transmission of the impulse to the ventricles
This is important because it permits the atria to complete their contraction and empty their blood into the ventricles before the ventricles contract

55. Purkinje Fibers
Once the nerve impulse leaves the AV node, it enters specialized muscle fibers called Purkinje fibers
Purkinje fibers permit a very rapid and simultaneous distribution of the nerve impulse throughout the muscular walls of both ventricles
This results in a contraction of the ventricles that proceeds upward from the apex of the heart toward its base
Ventricle contraction (systole) and atria relaxation (diastole) takes 0.30 seconds of the cardiac cycle

56. Purkinje Fibers
Once the ventricles have contacted, there is a period of atrial and ventricular relaxation
This recovery period occupies the final 0.40 seconds of the cardiac cycle

57. Cardiac Cycle Atrial & Ventricular Diastole 0.15 sec 0.30 sec 0.40 sec
Systole
Ventricular
Systole
Atrial &
Ventricular
Diastole
0.15 sec
0.30 sec
0.40 sec

58. Review of Cardiac Cycle
The spontaneous generation of a nerve impulse within the SA node represents the start of the cardiac cycle. This electrical impulse spreads throughout the atrial muscle and leads to contraction of the two atria.
As the atria contract, the AV valves remain open and blood is forced into the ventricles. The aortic and pulmonary semilunar valves remain closed, keeping blood in the ventricles.
After the atria have contracted and the ventricles have filled, the AV valves close.
The nerve impulse reaches the AV node, travels through the Purkinje fibers and the ventricles begin their contraction.
Ventricular contraction forces blood through the semilunar valves into the aorta and pulmonary arteries.
As the ventricles begin to relax, the aortic and pulmonary valves close, the AV valves open, and blood flows into the ventricles to begin another cycle.

59. Vascular Pathways The human heart has two pumps:
1) right atrium and ventricle pump deoxygenated blood from the body cells to the heart  pulmonary circulation
2) left atrium and ventricle pump oxygenated blood from the lungs to the body cells  systemic circulation

61. Major Blood Vessels Arteries Aortabody Subclavianarms Carotidbrain
Pulmonarylungs
Mesentericintestines
Renalkidneys
Iliaclower body
Femorallegs
Cardiacheart
Veins
Bodyvena cavae
Armssubclavian
Brainjugular
Lungspulmonary
Intestineshepatic portal
Liverhepatic
Kidneysrenal
Lower bodyiliac
Legsfemoral
Heartcardiac

64. Blood Flow
Blood pressure, the pressure of blood against the wall of a blood vessel, keeps the blood moving through the circulatory system
Blood pressure is measured with a sphygmomanometer, usually around the brachial artery in the arm

65. Blood Pressure
Systolic pressure = the highest blood pressure in the arteries is reached when the ventricles contract
Diastolic pressure = the lowest blood pressure in the arteries is reached when the ventricles are relaxed

66. Blood Pressure
The ratio of systolic pressure to diastolic pressure is commonly referred to as “blood pressure”
For the average human, “blood pressure” is 120 mm mercury systolic pressure to 80 mm mercury diastolic pressure  120/80

67. Blood Pressure and Velocity

68. Fetal Circulation

69. Fetal Circulation
The developing human fetus has several features that are not present in adult human circulation
These differences exist because the fetus is not using its lung for gas exchange
Gas exchange for the fetus is accomplished by the mother via the umbilical blood vessels

71. Fetal Circulation Features
Foramen ovale = oval opening
Shunts blood from right to left atrium in order to bypass inoperable lungs
2. Ductus arteriosus = arterial duct
Shunts blood from right ventricle and pulmonary artery to aorta in order to bypass inoperable lungs

72. Fetal Circulation Features
3. Umbilical arteries carry low oxygen blood and waste from fetus to placenta
4. Placenta allows gas, waste and nutrient exchange between the mother and fetus
5. Umbilical veins bring high oxygen blood and nutrients from placenta to fetus

73. Fetal Circulation Features
6. Ductus venosus = venous duct
Shunts blood from umbilical vein and fetal liver to the inferior vena cava of fetus