Biology 3.3 Flashcards
(19 cards)
Open circulatory system
Ex. insects, mollusks. Fluid called hemolymph functions as blood, lymph and interstitial fluid. Fluid is pumped to hemocoel where digestive and respiratory organs sit. Hemolymph absorbs oxygen/nutrients to distribute throughout the body. Hemolymph returns to heart through holes called Ostia.
Closed circulatory system
Ex. annelids, certain mollusks, vertebrates. Blood, which contains nutrients, oxygen, wastes, is isolated from interstitial fluid of the body. Oxygenated blood pumped away from the heart through arteries which branches into arterioles and capillaries. Gas exchange occurs at capillaries between blood and interstitial fluid. Deoxygenated blood carries waste back to the heart through venues which merge into veins. Deoxygenated blood goes to lungs via pulmonary arteries. Oxygenated blood returns to heart via pulmonary veins
Right atrium
Deoxygenated blood enters through superior and inferior vena cava
Right ventricle
Thicker muscle walls than atrium. When relaxed, right atrioventricular or tricuspid valve opens up and blood enters from Right atrium. When full, they contract which closes the tricuspid valve. Semilunar or pulmonary valve open, and blood flows from pulmonary arteries to lungs
Left atrium
Oxygenated blood returns through pulmonary veins
Left ventricle
When relaxed, left atrioventricular or mitral valve opens up and blood enters from left atrium. When full, they contract which closes the mitral valve. Semilunar aortic valve opens and blood flows to aorta and up aortic arch. Thicker than right ventricle because blood must overcome resistance to pump to the entire body.
Pulmonary circuit
pathway from R ventricle to lungs to L atrium
Systemic circuit
pathway from L ventricle to body to R atrium
Cardiac Cycle
rhythmic contraction/relaxation of heart muscles regulated by auto-rhythmic cells that function independently. 3 steps.
Step 1 of cardiac cycle
sinoatrial node (SA) on the wall of R atrium generates an action potential at a regular rate
Step 2 of cardiac cycle
Action potential spreads to both atrial walls to stimulate contractions until it reaches atrioventricular node (AV) at lower right wall of R atrium
Step 3 of cardiac cycle
Action potential reaches Bundle of His which bifurcates to left and right bundle branch that further branch to purkinje fibres that stimulate ventricular contraction. Closing of AV valves, followed by closing of semilunar valves create “Lub-dup” sound
Systole
ventricular contraction forces blood through pulmonary arteries and aorta. AV valves closed and semilunar valves open
Diastole
Ventricular relaxation causes semilunar valves to close and AV valves to open
Movement of blood
Hydrostatic pressure in heart causes blood to move through arteries. Blood pressure drops going from artery to arteriole to capillary. Skeletal muscles push on venules and veins to push blood to the heart and veins have valves to prevent back flow
Erythrocytes, RBCs
bioconcave disks that transport respiratory gases. Developed through a process called erythropoiesis and derived from stem cells stimulated by the cytokine erythropoietin
Leukocytes, WBCs
detect and fight against “non-self” material that are harmful, in the immune system
Platelets
performs blood clotting (hemostasis) at damaged blood vessel walls. Release clotting factors that convert the inactive agent fibrinogen to the active form fibrin
Plasma
liquid portion of blood containing proteins and dissolved substances. Plasma proteins are made in liver and control osmotic pressure inside capillaries. Since proteins are non-diffusible through capillary walls, a concentration gradient is made between blood and interstitial fluid that allows water to flow into or out of the capillaries
