1. What Are The Major Features And Functions Of Circulatory Systems?
A circulatory system evolved in multicellular animals to bring the external world to each metabolizing cell in the animal, so that nutrients, oxygen, and waste products could be exchanged.

2. What Are The Major Features And Functions Of Circulatory Systems?
Circulatory systems have three main components:
Blood
Blood vessels
Heart

3. Anatomy of Circulatory Systems
arteries - vessels that carry blood away from the heart
capillaries - smallest blood vessels (microscopic) penetrate tissues
extracellular fluid - fluid surrounding capillaries; dissolved substances in the blood are exchanged
veins – vessels that move blood back toward the heart

4. vertebrate circulatory systems transport…
oxygen from the lungs or gills to the tissues
carbon dioxide from the tissues to the lungs or gills
nutrients from the digestive system to the tissues
waste products & toxins to the liver & kidney for excretion
hormones from the glands and organs that produce them to the tissues on which they act

5. Circulatory Systems also
Help to regulate body temperature by adjusting blood flow
Help to protect the body from bacteria and viruses by circulating the cells and molecules of the immune system

6. How Does The Vertebrate Heart Work?
The vertebrate heart consists of muscular chambers.
In vertebrate hearts, muscular chambers, called atria, collect blood.
Blood flows from the atria to the ventricles, chambers whose contractions circulate blood through the body.
The number of atria and ventricles differs among different classes of vertebrates.

7. How Does The Vertebrate Heart Work?
Four-chambered hearts, like the human heart, can be thought of as two separate pumps.
One pump, consisting of the right atrium and right ventricle, pumps oxygen-depleted blood to the lungs.
The other pump, consisting of the left atrium and left ventricle, moves oxygen-rich blood from the lungs and through the aorta to the rest of the body.

8. How Does The Vertebrate Heart Work?
The human heart and its valves and vessels
aorta
left atrium
pulmonary artery (to left lung)
semilunar valves
pulmonary veins (from left lung)
atrioventricular valve
left ventricle
thicker muscle of left ventricle
descending aorta (to lower body)
right ventricle
inferior vena cava
superior vena cava
pulmonary artery (to right lung)
pulmonary veins (from right lung)
right atrium
Fig. 20-3

9. How Does The Vertebrate Heart Work?
The atria and ventricles contract in a coordinated way.
The chambers of the heart alternatively contract and relax
two atria contract at the same time, emptying their contents into the ventricles.
A fraction of a second later, the two ventricles contract, forcing blood into arteries that exit the heart
Both atria and ventricles then relax briefly, and the cycle repeats.

10. How Does The Vertebrate Heart Work?
The cardiac cycle
Oxygenated blood is pumped to the body
Deoxygenated blood is pumped to the lungs
Blood fills the atria and begins to flow passively into the ventricles
Deoxygenated blood from the body enters the right ventricle
Oxygenated blood from the lungs enters the left ventricle
Atria contract, forcing blood into the ventricles
Then the ventricles contract, forcing blood through the arteries to the lungs and the rest of the body
The cycle ends as the heart relaxes
Fig. 20-4

11. How Does The Vertebrate Heart Work?
The atria and ventricles contract in a coordinated way
At a normal resting heart rate, the cycle lasts about 1 second.
Blood pressure changes as the cycle proceeds
systolic pressure is measured during ventricular contraction
diastolic pressure is measured between contractions.

12. How Does The Vertebrate Heart Work?
Measuring blood pressure
A stethoscope detects pulse sounds
cuff
The cuff is inflated, putting pressure on the artery
Fig. 20-5

13. How Does The Vertebrate Heart Work?
Valves prevent blood from moving in the wrong direction.
Atrioventricular valves separate the atria from the ventricles
Semilunar valves allow blood to enter the pulmonary artery and the aorta when the ventricles contract

14. How Does The Vertebrate Heart Work?
Electrical impulses coordinate the sequence of contractions.
Contractions are coordinated by the pacemaker, a cluster of specialized heart muscle cells that produce spontaneous electrical signals.
The heart’s primary pacemaker is the sinoatrial (SA) node, located in the wall of the right atrium.

15. How Does The Vertebrate Heart Work?
Electrical impulses coordinate the sequence of contractions
From the SA node, an electrical impulse creates a wave of muscular contraction that spreads through the right and left atria until it arrives at the unexcitable tissue between the atria and ventricles.
There, the excitation is channeled through the atrioventricular (AV) node.

16. How Does The Vertebrate Heart Work?
Electrical impulses coordinate the sequence of contractions
From the AV node, the signal to contract spreads along excitable fibers to the base of the two ventricles.
This signal causes the ventricles to contract in unison.
If the pacemaker fails, uncoordinated irregular contractions, called fibrillation, occurs, and blood cannot be pumped out of the heart.

17. How Does The Vertebrate Heart Work?
The heart’s pacemaker and its connections
The sinoatrial node electrical signal starts the atrial contraction
Unexcitable tissue separates the atria and ventricles
AV node
The signal spreads, causing the atria to contract
excitable fibers
The atrioventricular node transmits the signal to the ventricles with a slight delay
The signal travels to the base of the ventricles
Excitable fibers transmit the signals to ventricular cardiac muscle, causing contraction from the base upwards
Fig. 20-6

18. What Is Blood?
Blood transports dissolved nutrients, gases, hormones, and wastes through the body.
It has two major components:
A fluid, called plasma
Cellular components—including red blood cells, white blood cells, and platelets—which are suspended in the plasma
The cellular components are produced in bone marrow and later move into the blood.

19. What Is Blood? Blood cells Fig. 20-9 neutrophil neutrophil monocyte
basophil
eosinophil
red blood cells
lymphocyte
(a)
Erythrocytes
(b)
White blood cells
platelets
megakaryocyte
(c)
Megakaryocyte forming platelets
Fig. 20-9

20. What Is Blood? Plasma is primarily water and dissolved substances.
Plasma is 90% water.
Dissolved in the plasma are proteins, hormones, nutrients, salts, and wastes, such as urea.

21. What Is Blood?
Red blood cells carry oxygen from the lungs to the tissues.
The most abundant cells in the blood are red blood cells.
Red blood cells get their red color from hemoglobin, an iron-containing protein that can bind up to four oxygen molecules.
Hemoglobin picks up oxygen in the lungs, where oxygen is at high concentration, and releases it in other tissues of the body, where the oxygen concentration is low.

22. What Is Blood? White blood cells help defend the body against disease.
White blood cells, or leukocytes, make up less than 1% of blood cells but play a key role in the body’s resistance to disease.
There are five types of white blood cells:
Neutrophils
Eosinophils
Basophils
Lymphocytes
Monocytes

23. What Is Blood?
Lymphocytes are responsible for the immune response against disease.
Neutrophils and monocytes engulf foreign particles.
Fig

24. What Is Blood?
Platelets are cell fragments that aid in blood clotting.
Platelets are pieces of large cells, called megakaryocytes, that occur in the bone marrow and enter the blood, playing a key role in blood clotting.
Blood clotting starts when platelets contact an irregular surface, such as a damaged blood vessel, where they partially block the opening.

25. What Is Blood?
The platelets and injured tissue initiate a complex sequence of reactions among plasma proteins, which results in a fibrous network, called fibrin, that traps red blood cells and closes the wound.
platelets
white blood cell
fibrin strands
red blood cell
Fig

26. What Are The Types And Functions Of Blood Vessels?
jugular vein
aorta
superior vena cava
carotid artery
lung capillaries
pulmonary artery
heart
kidney
femoral vein
intestine
inferior vena cava
liver
femoral artery
As it leaves the heart, blood travels from arteries to arterioles to capillaries to venules to veins, and finally, it returns to the heart.

27. What Are The Types And Functions Of Blood Vessels?
Arteries and arterioles carry blood away from the heart.
These vessels have thick walls embedded with smooth muscle and elastic connective tissue.
Arteries branch into vessels of small diameter called arterioles.
precapillary sphincters
arteriole
venule
artery
vein
capillary
valve
smooth muscle
connective tissue
cross section
capillary network
Fig

28. What Are The Types And Functions Of Blood Vessels?
Structures and interconnections of blood vessels
capillary network
arteriole
smooth muscle
precapillary sphincters
venule
cross section
capillary
valve
smooth muscle
connective tissue
artery
vein
Fig

29. What Are The Types And Functions Of Blood Vessels?
Capillaries are microscopic vessels through which nutrients and wastes are exchanged.
Diffusion of nutrients and wastes occurs in capillaries, the smallest of all blood vessels.
Because their walls are only one cell thick, substances can cross a capillary cell’s plasma membrane and easily move into or out of capillaries.
Capillaries are so narrow that red blood cells pass through them in single file.
The speed of blood flow drops very quickly as it moves through this narrow capillary network.
The flow of blood in capillaires is regulated by tiny rings of smooth muscle, called precapillary sphincters, which surround the junctions between arterioles and capillaries.

30. What Are The Types And Functions Of Blood Vessels?
Red blood cells flow through a capillary.
Red blood cells must pass through capillaries in single file
Capillary walls are thin and permeable to gases, nutrients, and cellular wastes
Fig

31. What Are The Types And Functions Of Blood Vessels?
Venules and veins carry blood back to the heart.
After picking up carbon dioxide and other cellular wastes from cells, capillary blood drains into larger vessels called venules, which empty into larger veins.
To prevent blood from flowing away form the heart, veins are equipped with valves that allow blood to flow in only one direction.

32. What Are The Types And Functions Of Blood Vessels?
Blood pressure is low in veins and contraction of skeletal muscle during exercise helps return blood to the heart by squeezing the veins and forcing blood through them.
Valves direct the flow of blood in veins.
valve open
valve closed
muscle contraction compresses vein
relaxed muscle
valve closed
Fig