ch.3 circulatory system

Question 1

protozoans

Answer 1

unicellular animal-like protists
rely on the movement of gas via simple diffusion within the cell

Question 2

cnidarians

Answer 2

body walls are 2 cells thick so all cells are in direct contact with either internal or external environment

ex: hydra

Question 3

arthropods

Answer 3

includes most insects and crustaceans
i. open circulatory system - pump blood into an internal cavity called the hemocoel (has smaller cavities called sinuses), which bathes tissues in oxygen and nutrient containing fluid called hemolymph
ii. hemolymph returns to the pumping mechanism (heart) through holes called ostia
iii. mollusks - most have open circulatory systems except for cephalopods, which have closed circulatory systems
a) cephalopods have closed systems due to large oxygen demands, and have gill hearts
iv. annelids - include earthworms
a) have closed circulatory systems in which blood is confined to vessels (also seen in certain mollusks and vertebrates)

Question 4

path of circulation in closed system

Answer 4

away from heart: aorta –> arteries –> arterioles –> capillaries

back to heart: capillaries –> venules –> veins

the dorsal vessel functions as the main heart or pump; aortic loops link the dorsal and ventral vessels together, which function in pumping blood

Question 5

number of chambers in different animals

Answer 5

humans, birds, crocodiles, and alligators: 4
reptiles and amphibians: 3
fish: 2

Question 6

pericardium

Answer 6

a fluid filled sac that surrounds the heart in order to protect and lubricate it for proper function

Question 7

right atrium

Answer 7

chamber where deoxygenated blood enters via the superior and inferior vena cava

Question 8

right ventricle

Answer 8

blood is squeezed into this chamber through the right AV (atrioventricular)/tricuspid valve, which contracts and pumps blood into the pulmonary artery via the pulmonary semilunar valve

• when the ventricle contracts, the tricuspid valve closes to prevent backflow, which produces the ‘lub’ sound
• when the ventricle relaxes, the pulmonary valve prevents backflow from pulmonary artery back into ventricles by closing, thus creating the ‘dub’ sound

Question 9

pulmonary circuit

Answer 9

the blood pathway from the right side of the heart to the lungs, and eventually the left side of the heart

Question 10

systemic circuit

Answer 10

heart (left) –> body –> heart (right)

Question 11

left atrium

Answer 11

after traveling through the lungs, oxygenated blood enters the left atrium via the pulmonary veins

Question 12

left ventricle

Answer 12

after traveling through the left AV/mitral/bicuspid valve, blood from the left ventricle enters the aorta through the aortic valve into the rest of the body

Question 13

ejection fraction

Answer 13

the % of blood that does not leave the ventricle when the heart pumps

Question 14

SA (sinoatrial) node/pacemaker

Answer 14

located in upper wall of the right atrium, the SA node is a group of specialized cardiac muscle cells that initiate by contracting both atria and sending an impulse that stimulates the AV node
i. at the AV node, the impulse is briefly delayed to allow the atria to completely empty, and to allow the ventricles to fill with blood
ii. the impulse spreads the contraction to surrounding cardiac muscles via electrical synapses made from gap junctions
iii. the pace of the SA node is faster than the normal heartbeat, but the parasympathetic vagus nerve innervates the SA node and slows contractions
a) the vagus nerve also increases the digestive activity of intestines

Question 15

AV node

Answer 15

located in the lower wall of the right atrium / interatrial septa; sends impulse through the Bundle of His -> passes between both ventricles -> branches into ventricles via the purkinje fibers which results in contraction of both ventricles simultaneously

Question 16

ventricular contraction

Answer 16

when the ventricles contract (ventricular systole phase), blood is forced through the pulmonary arteries and aorta

Question 17

papillary muscles and chordae tendinae

Answer 17

attached to cardiac valves and force them closed during systole

Question 18

why is the left ventricle thicker than the right

Answer 18

it pumps blood to most of the body, but the right ventricle only pumps to the lungs

Question 19

systole vs. diastole

Answer 19

systole- occurs when the atria or ventricles contract
diastole- occurs during relaxation of atrial or ventricles

Question 20

semilunar valves

Answer 20

aortic and pulmonary valves

Question 21

atrioventricular valves

Answer 21

tricuspid/right AV valves and bicuspid/left AV/mitral

Question 22

blood pressure

Answer 22

hydrostatic pressure from the heart contracting causes blood to move through the arteries. Blood pressure drops as it reaches the capillaries, and reaches near zero in the venules. Blood continues to move through the veins due to:
1. pumping of the heart assisted by movements of adjacent skeletal muscles
2. expansion of atria each time the heart beats
3. falling pressure in the chest when a person breathes

Question 23

arteries

Answer 23

thick-walled, muscular, elastic vessels that pump oxygenated blood away (except for pulmonary arteries that transport deoxygenated blood form the heart to lungs). wrapped in smooth muscle, arteries are typically innervated by the sympathetic nervous system.
i. large arteries have less smooth muscle (per volume) than medium sized ones; larger arteries are also less affected by the sympathetic nervous system, but medium sized arteries can constrict enough to re-route blood
ii. arteries have 3 layers (tunics):
a) endothelial lining (inner)
b) smooth muscle and elastic tissue (middle)
c) connective tissues (outer)

Question 24

arterioles

Answer 24

very small vessels wrapped in smooth muscle, and constrict or dilate to regulate blood pressure or re-route blood
i. are a major determinant of blood pressure as they have the greater resistance to blood flow

Question 25

capillaries

Answer 25

have the smallest diameter and have a single layer of endothelial cells across which gases, nutrients, enzymes, hormones, and waste diffuse
i. there are 4 methods for materials to cross the capillary wall
a) endo or exocytosis (proteins)
b) diffusion through capillary cell membrane
(O2 and CO2)
c) movement through pores called
fenestrations
d) movement through space between the
cells (ions)
ii. sometimes you will also see pericytes (contractile cells) around the capillaries and venules throughout the body

Question 26

erythrocytes

Answer 26

RBC
transport oxygen on hemoglobin

Question 27

leukocytes

Answer 27

WBC
phagocytes that engulf foreign particles