Circulatory System Flashcards
What are Arteries?
Carry blood away from the heart Carry blood with oxygen (red) with the exception of the pulmonary artery Walls are thick, strong, and stretchy Composed of three layers Carry blood at high pressure
What are Arterioles?
Smaller arteries
Vasoconstriction and vasodilation take place
Help lower blood pressure
What are Capillaries?
Smallest vessel in the body (single cell layer thick)
Branch through tissues
Site of fluid and gas exchange (oxygen, nutrients, carbon dioxide and wastes) between blood and tissue fluid by diffusion
Red blood cells must pass through single file
Fragile
What are Venules?
Smaller veins where deoxygenated blood collects from capillaries
What are Veins?
Carry blood towards the heart
Blood is deoxygenated (blue) with the exception of the pulmonary vein
Thin walled; carry blood under low pressure
Contains valves which open in one direction only
The walls of veins allow materials to diffuse in and out easily
What is the heart?
Muscular organ, size of your fist
Surrounded by a fluid-filled membrane called the pericardium that reduces friction
What are the chambers in the heart?
Each side has two hollow muscular chambers that are separated by a wall called a septum
Four chambers total
Two thin walled atria (receives blood)
Two thick ventricles (pumps blood out of the heart)
What is pulmonary circulation?
Deoxygenated blood pumped from the right side of the heart to the lungs via the pulmonary arteries
Blood picks up oxygen (oxygenated) and travels back to the left side of the heart via the pulmonary veins
What is systemic circulation?
Left side of the heart pumps blood to the entire body via the aorta (largest artery)
From the aorta blood is diverted to
- coronary arteries (heart tissue)
- upper and lower body arteries
- Hepatic/Portal System (digestive)
Two large veins called the superior and inferior veins cava return blood to the right side of the heart
What are valves in the heart?
Allow blood to flow in one direction only
AV (atrioventricular) valve separates atria and ventricles
SV (semilunar) valve separates ventricles and arteries (pulmonary trunk and aorta)
Tiny chords anchor flaps of valves to ventricle walls
What controls the pumping of the heart?
SA node (sinoatrial node) initiates the controls of the heartbeat but external stimulation can speed up or slow down the heart
The SA node is located at the top right side of the right atrium. Electrical impulses are delayed from the top to bottom of the heart
When the atria are contracting the ventricles need to be relaxed and vice versa
What is the external regulation of the heart rate?
The SA node is regulated externally by the parasympathetic and sympathetic nerves which conduct electrical impulses
What is the Cardiac Cycle?
The sequence of heart chamber contraction
Diastole: chamber relaxation
Systole: chamber contraction
What causes the “Lubb-dubb” sound in the heart?
“Lubb” caused by closing of both the atrioventricular valves
“Dubb” caused by closing of both the semilunar valves
What is blood pressure?
The force that blood exerts on the walls of blood vessels
Blood pressure is highest in the blood vessels closest to the heart (aorta) and lowest in the veins
Blood pressure depends on what two factors?
The volume of blood pumped (cardiac output)
The resistance to blood flow caused by narrowing of the arterioles (vasoconstriction and vasodilation)
What is Capillary Exchange?
Blood moves through the capillary very slowly which allows time for exchange of materials
CO2 and O2 move in and out of capillary by process of diffusion
Water moves out of arteriole and carries sugar, amino acids, wastes, hormones, vitamins
What two forces control movement of fluid through the capillary wall?
Osmotic pressure
Blood pressure
Describe osmotic pressure in the capillary exchange.
Moves water from tissue fluid into blood
Describe blood pressure in the capillary exchange.
Moves water from blood into tissue fluid
Solutes diffuse according to their concentration gradient
Glucose and oxygen diffuse out of capillary
Wastes and CO2 diffuse into capillary
What is the lymphatic system?
Lymphatic vessels capture excess fluids leaked from capillaries
Collect products of fat digestion from small intestine
Lymph nodes found mainly in neck, groin, and armpit
The pulsing of blood through the arteries that caused the systolic values of blood pressure to be recorded is due to the action of what structures?
The ventricles
The movement of blood from the legs towards the heart is achieved through the use of:
Valves and muscular contraction
In which direction will water molecules move at the arteriolar end of the capillary bed?
It will move from the blood to the tissue fluid
In which direction will water molecules move at the venous end of the capillary bed?
It will move from the tissue fluid into the blood
What does the P represent on an electrocardiogram?
Atrium excitation begins
Atrium contract
What does after the P represent on an electrocardiogram?
Impulse delayed at SA node
Ventricles fill
What does the QR represent on an electrocardiogram?
Ventricular excitation
Bicuspid and tricuspid valves close
Lub sound is made
What does the RS represent on an electrocardiogram?
Ventricular excitation complete
What does the T represent on an electrocardiogram?
Ventricular relaxation
Semilunar valves close
