B2.2 The challenges of size Flashcards
What is a surface area to volume ratio?
The surface area per unit volume of an object - calculated as a ratio
Why is surface area to volume ratio important?
The smaller the organism the larger the SA:V ratio is, nutrients can diffuse directly into the organism quickly enough to sustain life as diffusion distances are small
- larger organism has lower SA:V ratio - most multicellular organisms cant use simple diffusion to survive, as diffusion over a greater distance ant occur fast enough to meet cells demands
Exchange surfaces in larger organisms
Larger organisms have developed exchange surfaces, which increase SA:V ratio - e.g. alveoli on lungs, villi of small intestine
What features make an efficient exchange surface?
- large SA - so diffusion happens faster
- good blood supply - to maintain a steep concentration gradient so molecules can diffuse quicker
- thin walls - short diffusion distance
- moist - gases can only diffuse dissolved in solution
Why do we need a transport system?
- once substance have diffused into the body they must be transported to the cells that need them
- our circulatory system allows materials to travel around our bodies quickly
What is the circulatory system made of?
Heart, blood and blood vessels
Is the circulatory system open or closed, and why?
Closed - as blood remains within the structures
What does the circulatory system transport, and where?
- oxygen & glucose to the cells that need it
- Carbon dioxide and urea (waste products) away from cells
What is the heart?
A pump which circulates blood
What does blood flow away from the heart in?
Arteries
What does blood flow towards the heart in?
Vein
Where are valves and what do they do?
They are in the veins, and prevent back-flow of blood, TMT the blood flow is one-way
is our circulatory system double or single?
double - blood flows at low pressure from right side (to lungs) & high pressure from left side (to body)
is the heart a single or double pump?
double pump
describe the flow of blood throughout the body (oxygenated / deoxygenated blood - simple)
- deoxygenated pumped from heart to lungs
- blood receive oxygen - oxygenated blood pumped back to heart to rest of body
- oxygen leaves blood (for respiration in body) + blood goes back to heart
what is meant by a closed system?
blood stays inside blood vessels
what is the heart made up of?
cardiac tissue
what is special about the cardiac muscle?
can contract without receiving a nerve impulse from brain and don’t get tired easily (like other muscles
what are the two top chambers of the heart called?
atria (sing. atrium)
smaller
what are the two bottom chambers of the heart called?
ventricles
larger
label a heart diagram
describe the flow of blood through the heart - for oxygenated blood
PV,LA,BV,LV,AO,Body
describe the flow of blood through the heart - for deoxygenated blood
VC,RA,TV,RVPA,Lungs
characteristics of arteries
- thick walls
- small lumen
- high pressure
- away from heart - oxygenated blood
characteristics of veins
- thin walls
- large lumen
- low pressure
- into heart - deoxygenated blood
characteristics of capillaries
- very thin walls - one cell thick- - quicker diffusion for gaseous exchange
- very small lumen
- connected arteries to veins
what is blood made of?
platelets
plasma
red & white blood cells
what is plasma?
- pale yellow liquid
- makes 55% volume of blood
- over 90% water containing dissolved substances such as - food (glucose +amino acids), wastes (urea +CO2), hormones and antibodies
where are red blood cells made?
in bone marrow + live for about 4 months
what is the role of red blood cells?
carry O2 from lungs to organs
what are adaptations of red blood cells?
- biconcave disks - larger SA:V ratio - quicker diffusion of O2
- have lots haemoglobin which carry O2
- no nucleus - more space for haemoglobin + can carry more O2
what are platelets?
small fragments of cells - no nucleus - help blood clot at wounds
what are white blood cells?
- part of body defence system against pathogens
- have nucleus
what are coronary arteries
- supply blood to heart muscle
- wrap around outside of heart - small branches dive into blood
what is most of the heart made up of?
- cardiac muscle / tissue
