heart and circulatory system Flashcards
(45 cards)
what is a single circulatory system?
blood flows in 1 circuit around the body
eg in fish
what is a double circulatory system?
blood flows in 2 circuits around the body
- from the heart to the lungs
- from the heart to the rest of the body
eg humans
what are the advantages of a double circulatory system?
- higher blood pressure, especially to the body
- higher blood flow to body tissues
- oxygenated and deoxygenated
arteries - structure and function
- thick elastic wall (allows it to withstand high pressure of the blood)
- small, narrow lumen
- able to stretch ad recoil
- carry oxygenated blood (apart from pulmonary artery) away from the heart
capilleries - structure and function
- thin walls are 1 cell thick (short diffusion path)
- carry blood from arteries to veins
- smallest blood vessels (7-10μm)
- red blood cells must pass through single file
- large surface area
- function is gas exchange
veins - structure and function
- thin wall
- wide lumen (able to hold a large volume of blood)
- valves (prevet backflow of blood)
- carry deoxygenated blood to the heart (apart from pulmonary vein)
- low pressure
what are the main blood vessels in the heart? (4)
- pulmonary vein
- aorta - main artery
- vena cava - main vein
- pulmonary artery
what type of blood does the pulmonary vein carry, from where and where to?
oxygenated blood from lungs to left atrium
what type of blood does the aorta carry, from where and where to?
oxygenated blood from left atrium to body
what type of blood does the vena cava carry, from where and where to?
deoxygenated blood from body to right artrium
what type of blood does the pulmonary artery carry, from where and where to?
deoxygenated blood from right artrium to lungs
why do ventricles have thicker walls than atria?
ventricles have to pump blood further
what controls the natural resting heartbeat?
pacemaker cells (from the sinoatrial node) in the right atrium
explain blood flow in the heart
- heart relaxes and blood enters both atria
- atria contract at the same time which forces blood into both ventricles
- ventricles contract from the bottom upwards which forces blood into the pulmonary artery/ aorta
when are the atrioventricular valves open/shut?
open when atria contract and force blood into vetricles, shut when ventricles cotract force blood into aorta/ pulmonary artery
what is the function of the atrioventricular valves?
open to let blood through and then shut to prevent the backflow of blood
what is blood made up of?
- 55% plasma
- 45% red blood cells
- ~1% white blood cells
- ~1% platelets
function and structure of plasma
- straw coloured liquid
- trasports many substaces in the blood like hormones, antibodies, nutrients and waste substances
function and structure of platelets
- cell fragments
- help the clotting process at wound sites
function and structure of white blood cells
- can change shape to exit blood vessels and chase pathogens
- lymphocytes and phagocytes
- large nucleus for immunological memory
- destroy pathogens and create antitoxins
function and structure of red blood cells
- very small so they can pass through capilleries
- biconcave so they have a large surface area:volume ratio which increases rate of diffusion of oxygen
- no nucleus to increase space for haemoglobin
how many red blood cells are there in 1 mm³?
around 5 million which means that blood is able to transport oxygen efficiently
how do red blood cells carry oxygen?
- haemoglobin binds to oxygen at a a high concentration (eg in the lungs) to form oxyhaemoglobin
- the bonds between oxygen and haemoglobin are weak and reversible so oxyhaemoglobin dissociates to haemoglobin and oxygen in low oxygen concentrations (eg body tissues that need oxygen)
what is cardiac rate?
volume of blood flowing out of the heart in 1 min
