Circulation and The Heart (lesson eight)

Question 1

Does unicellular organisms have a circulatory system

Answer 1

Unicellular organisms, like some bacteria, algae and fungi, can function without a circulatory system because they directly exchange gases with the environment

Question 2

do all multicellular organisms have circulatory systems?

Answer 2

Some simple multicellular organisms do not either but instead depend on an internal body cavity lining covered in flagella to circulate fluid through the body (recall: flagella are microscopic hair-like structures that help with locomotion)

Question 3

Open circulatory systems

Answer 3

• In an open circulatory system, the circulating fluid is pumped into a connected system of body cavities, often called sinuses
• These openings bathe the cells directly in the hemolymph, a mixture of blood and tissue fluid
• The contraction of one or more hearts forces the hemolymph around the body
• Most invertebrates, like snails and insects, have this type of system

Question 4

is an open circulatory system inefficient or efficient?

Answer 4

• This is a relatively inefficient method of circulation because the hemolymph is under low pressure and circulates slowly
• This is practical for many animals with low metabolic rates which therefore have lower oxygen and energy demands

Question 5

Closed circulatory system?

Answer 5

• in a closed circulatory system, the fluid, often blood, is contained within a network of tubes called blood vessels
• The blood and tissue fluid (recall- the interstitial fluid) are always separate
• All vertebrates and some complex invertebrates have a closed system
• There is a lot of variation in the structure of closed circulatory systems

Question 6

how many variations of a closed circulatory system are there?

Answer 6

Closed circulatory systems may include one of 5 versions of an increasingly complex “heart” structure depending on their evolution

Question 7

Aortic Arch

Answer 7

• which are enlarged blood vessels that work like hearts to pump blood through the system
• found in earthworms

Question 8

Two Chambered Heart

Answer 8

this structure is commonly found in fish

Question 9

Three Chambered Heart

Answer 9

commonly found in amphibians

Question 10

Four Chambered Heart

Answer 10

This structure is found in reptiles, mammals, and birds (which may or may not have a septum)

Question 11

two-circuit circulatory system

Answer 11

• humans have an example of a complex closed circulatory system, called a two-circuit circulatory system
• In these systems, the circulation of blood to the lungs (pulmonary circuit) is separate from the circulation of blood to the rest of the body (systemic circuit)

Question 12

how is a two-circuit circulatory system possible?

Answer 12

This is possible because of our four-chambered heart

Question 13

where is the Heart found

Answer 13

found in the middle of your chest, directly under your breastbone, is the center of your circulatory system

Question 14

what is the heart made up of?

Answer 14

• You have two atria, which receive blood from your body at the top of the heart
• You have two ventricles, which receive blood from your atria at the bottom of the heart

Question 15

does the atrium or the ventricular have thicker walls?

Answer 15

• The ventricular walls are much thicker and more muscular than the atria
• This is because the ventricles have to pump blood a much longer distance
• Because the atria do not have to pump blood far there is less muscle required (blood in atria must only be pumped into ventricles)

Question 16

septum

Answer 16

Your heart is divided into two sides by the septum

Question 17

what right side of the heart receive?

Answer 17

The right side of your heart receives blood from your systemic (body) circuit and circulates blood to your pulmonary (lung) circuit

Question 18

what does the left side of the heart receive?

Answer 18

The left side of your heart receives blood from your pulmonary (lung) circuit and circulates blood to your systemic (body) circuit

Question 19

Circulation Through the Heart

Answer 19

• Blood enters your right atrium from one of two blood vessels
• Blood from your upper body tissues enters from your superior vena cava or Blood from your lower body tissues enters from your inferior vena cava
• Your right atrium then beats and blood enters the right ventricle through your atrioventricular valve (specifically, the tricuspid valve)
• Blood then leaves your right ventricle through the semilunar valves (specifically, the pulmonary semilunar valve) to go towards your lungs via your left pulmonary arteries
• Blood is then oxygenated in the lungs and returns to your heart via the right pulmonary veins
• It enters your left atrium and then is pushed towards your left ventricle through the mitral valve (the other atrioventricular valve)
• Blood then gets pushed through the semilunar valve (specifically, the aortic semilunar valve) and enters the aorta so it can be distributed through the body

Question 20

chordae tendineae

Answer 20

The atrioventricular valve is supported by tough cords called chordae tendineae and prevents blood from flowing backwards

Question 21

coronary blood vessels

Answer 21

• the heart has its own supply of blood vessels called the coronary blood vessels which branch off the aorta

Question 22

pericardium

Answer 22

• Your heart is protected by a double-layer membrane called the pericardium
• Like the pleural membrane around the lung, it is filled with fluid and prevents friction by providing lubrication

Question 23

what are the circulatory system’s functions?

Answer 23

1. It delivers oxygen from the respiratory system
2. It delivers nutrients from the digestive system
3. delivers hormones from the endocrine system
4. delivers chemicals or cells from the immune system
5. delivers metabolic wastes from the cells to the lungs and kidneys