Lecture Notes: Circulation and Gas Exchange in Mammals

Question 1

anatomy of circulatory system of mammals

Answer 1

• fully divided ventricle, four-chambered heart
• double circulation, pulmonary and systemic circuit
• same in birds and crocodiles

Question 2

advantages of closed circulatory systems

Answer 2

• gas exchange maximized
• full seperation of oxygen rich and poor blood
• arterial and venous circuits work at different pressures
• arterial blood receives the highest oxygen content
• ability to maintain higher blood pressure to sustain energetically expensive tissues

Question 3

right atrium

Answer 3

• receives deoxygenated blood from the superior and inferior vena cava
• pumps blood to right ventricle past the tricuspid valve

Question 4

right ventricle

Answer 4

• send blood to the pulmonary circuit via pulmonary trunk (carries deoxygenated blood)
• back flow is prevented by pulmonary semilunar valve

Question 5

left atrium

Answer 5

• receives blood from the pulmonary veins (carry oxygenated blood)
• sends oxygenated blood to the left ventricle past the bicuspid valve

Question 6

left ventricle

Answer 6

• sends oxygenated blood to the systemic circuit via aortic arch
• aortic semilunar valve prevents the back flow

Question 7

layers of the wall of the heart

Answer 7

endocardium- connective + epithelial (protection)

myocardium- cardiac muscle (contraction)

Question 8

pericardium

Answer 8

• protection and support

- fibrous layer (outer), then serous layer ( parietal and visceral)

Question 9

parietal

Answer 9

fused to fibrous layer

Question 10

visceral

Answer 10

aka epicardium adheres to the hearts surface

Question 11

pericardial cavity

Answer 11

between the parietal and visceral

pericardial fluid reduces friction

Question 12

coronary arteries

Answer 12

openings below the aortic semilunar valve

Question 13

blood supply to the heart

Answer 13

coronary arteries

coronary veins..coronary sinus..right atrium

Question 14

control of heartbeat

Answer 14

• cardiac muscle fibers are joined by intercalated disks
• sinoatrial (SA) node
• atrioventricular (AV) node

Question 15

intercalated disks

Answer 15

• gap junctions that spread action potentials

- desmosomes that reinforce the connections between fibers

Question 16

Sinoatrial (SA) node

Answer 16

• acts as a pacemaker, maintains self rhythm

- near where superior vena cava enters the right atrium

Question 17

Atrioventricular (AV) node

Answer 17

• transmits the action potential from the atria to ventricles via bundle of His.
• bundle branches left and right to purkinje fibers
• impulses are delayed…atria contract first; empty before ventricles contract

Question 18

arteries

Answer 18

• composed of collagen, provides support for high blood pressure
• elastic fibers store energy from blood pressure
• recoil during diastole
• smoother blood flow
• smooth muscle vasodilation and vasoconstriction control direction and pressure of blood

Question 19

veins- how does blood travel against gravity?

Answer 19

1. veins in between muscles, muscles squeeze

2. one-way valves, preventing backflow

Question 20

capillaries

Answer 20

• connect arterioles to venules
• small diameter, RBC pass in single line
• walls (single layer of endothelial cells) are permeable to water, lipid-soluable and small molecules
• some with intercellular clefts
• some fenestrated
• some very selective, some not

Question 21

arteriole side of capillary

Answer 21

-blood pressure > osmotic pressure

fluid exits

Question 22

venule side of capillary

Answer 22

-blood pressure < osmotic pressure

fluid enters

Question 23

lymphatic tissue

Answer 23

loss of fluid at capillaries returned to blood by the lymphatic system

1. diffusion of fluid into lymph capillaries
2. formation of lymph
3. drainage of lymph into circulation from thoracic duct at left brachiocephalic vein

Question 24

regulation of blood flow

Answer 24

1. pre capillary sphincters (smooth muscle) control flow from arterioles to capillary beds
2. low [oxygen], high [carbon dioxide] or [metabolic products] causes smooth muscle to relax

Question 25

blood

Answer 25

• connective tissue
• plasma (extracellular matrix)
• cellular elements (hematocrit: fracked cell volume)

Question 26

erythrocytes

Answer 26

• transport respiratory gases through hemoglobin
• anucleated and biconcave, increases area
• flexible
• production in bone marrow controlled by erythroprotein
• stored and recycled in the spleen

Question 27

erythroprotein

Answer 27

released in kidney in response to hypoxia (low oxygen levels)

Question 28

leukocytes

Answer 28

• immune response

- can move out of capillaries and into extracellular fluid—amoeboid

Question 29

platelets

Answer 29

• a-nucleated cytoplasmic bodies with cytoskeletal elements, enzymes and some organelles
• promote blood clotting and formation of platelet plug