circularity system chapter 50 Flashcards
Blood
Type of connective tissue composed
Fluid matrix called plasma
Formed elements—cells and platelets
Functions of circulating blood
Transportation—nutrients, O2, CO2, metabolic wastes, etc.
Regulation—hormones, vasoconstriction, vasodilation (controls heat)
Protection—blood clotting, leukocytes
Blood plasma
92% water Contains the following solutes Nutrients, wastes, and hormones Ions—Na+, Cl-, HCO3-, others Proteins Albumin, alpha (a) and beta (b) globulins Fibrinogen If removed, plasma is called serum
Formed elements
Red blood cells (erythrocytes)
About 5 million per microliter of blood
Hematocrit is the fraction of the total blood volume occupied by red blood cells (usually 45%)
Mature mammalian erythrocytes lack nuclei
RBCs of vertebrates contain hemoglobin
Pigment that binds and transports oxygen
White blood cells (leukocytes) Less than 1% of blood cells Larger than erythrocytes and have nuclei Can migrate out of capillaries into tissue fluid Types Granular leukocytes Neutrophils, eosinophils, and basophils Agranular leukocytes Monocytes and lymphocytes
Platelets
Cell fragments that pinch off from larger cells in the bone marrow
Function in the formation of blood clots
All develop from pluripotent stem cells
Hematopoiesis is blood cell production
Occurs in the bone marrow
Produces 2 types of stem cells
Lymphoid stem cell Lymphocytes
Myeloid stem cell All other blood cells
Erythropoietin (from kidney in response to low O2) stimulates the production of erythrocytes (erythropoiesis)
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Invertebrate Circulatory Systems
Larger animals require a separate circulatory system for nutrient and waste transport
Open circulatory system
No distinction between circulating and extracellular fluid
Fluid called hemolymph
Closed circulatory system
Distinct circulatory fluid enclosed in blood vessels and transported away from and back to the heart
Vertebrate Circulatory Systems
Amphibians
Advent of lungs required a second pumping circuit, or double circulation
Pulmonary circulation moves blood between the heart and lungs
Systemic circulation moves blood between the heart and the rest of the
Amphibian heart
3-chambered heart
2 atria and 1 ventricle
Separation of the pulmonary and systemic circulations is incomplete
Amphibians living in water obtain additional oxygen by diffusion through their skin
Reptiles have a septum that partially subdivides the ventricle, thereby further reducing the mixing of blood in the heart
Mammals, birds, and crocodilians
4-chambered heart
2 separate atria and 2 separate ventricles
Right atrium receives deoxygenated blood from the body and delivers it to the right ventricle, which pumps it to the lungs
Left atrium receives oxygenated blood from the lungs and delivers it to the left ventricle, which pumps it to rest of the body
The Cardiac Cycle
Heart has two pairs of valves
Atrioventricular (AV) valves
Maintain unidirectional blood flow between atria and ventricles
Tricuspid valve = On the right
Bicuspid, or mitral, valve = On the left
Semilunar valves
Ensure one-way flow out of the ventricles to the arterial systems
Pulmonary valve located at the exit of the right ventricle
Aortic valve located at the exit of the left ventricle
Valves open and close as the heart goes through the cardiac cycle
Ventricles relaxed and filling (diastole)
Ventricles contracted and pumping (systole)
“Lub-dub” sounds heard with stethoscope
Lub – AV valves closing
Dub – closing of semilunar valves
Heart contains “self-excitable” autorhythmic fibers
Most important is the sinoatrial (SA) node
Located in wall of right atrium
Acts as pacemaker
Autonomic nervous system can modulate rate
Each SA depolarization transmitted
To left atrium
To right atrium and atrioventricular (AV) node
AV node is only pathway for conduction to ventricles
Spreads through atrioventricular bundle
Purkinje fibers
Directly stimulate the myocardial cells of both ventricles to contract
Electrical activity can be recorded on an electrocardiogram (ECG or EKG)
First peak (P) is produced by depolarization of atria (atrial systole)
Second, larger peak (QRS) is produced by ventricular depolarization (ventricular systole)
Last peak (T) is produced by repolarization of ventricles (ventricular diastole)
Right and left pulmonary arteries deliver oxygen-depleted blood from the right ventricle to the right and left lungs
Pulmonary veins return oxygenated blood from the lungs to the left atrium of the heart
Aorta and all its branches are systemic arteries, carrying oxygen-rich blood from the left ventricle to all parts of the body
Coronary arteries supply oxygenated blood to the heart muscle
Blood from the body drains into the right atrium
Superior vena cava drains upper body
Inferior vena cava drains lower body
Arterial blood pressure can be measured with a sphygmomanometer
Systolic pressure is the peak pressure at which ventricles are contracting
Diastolic pressure is the minimum pressure between heartbeats at which the ventricles are relaxed
Blood pressure is written as a ratio of systolic over diastolic pressure
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Characteristics of Blood Vessels
Blood leaves heart through the arteries
Arterioles are the finest, microscopic branches of the arterial tree
Blood from arterioles enters capillaries
Blood is collected into venules, which lead to larger vessels, veins
Veins carry blood back to heart
Arteries and veins are composed of four tissue layers
Endothelium, elastic fibers, smooth muscle, and connective tissue
Walls too thick for exchange of materials across the wall
Capillaries are composed of only a single layer of endothelial cells
Allow rapid exchange of gases and metabolites between blood and body cells
Arteries and arterioles
Larger arteries contain more elastic fibers in their walls than other blood vessels
Recoil each time they receive blood from the heart
Contraction of the smooth muscle layer of the arterioles results in vasoconstriction
Greatly increases resistance and decreases flow
Chronic vasoconstriction can result in hypertension
Relaxation of the smooth muscle layer results in vasodilation
Decreasing resistance and increasing blood flow to an organ
