B8 - transport in animals Flashcards
Why do animals need a transport system?
Higher metabolic demands:
- high O2 & CO2 demands = more waste produced = diffusion alone not enough
small SA:V:
larger distance & smaller SA to absorb nutrients
hormones/enzymes:
- made in one place, needed in another
waste products:
- need transporting to excretory organs & removed
food:
- transported to cells for respiration etc.
components of circulatory system(3):
liquid transport medium = blood
vessels = carry transport medium
pumping mechanism to move fluid = HEART
open circulatory system in general
- few vessels to contain transport medium
- pumped straight from heart to haemocoel(open body cavity), where transport medium has low pressure
- transport medium has direct contact w/ cells & tissues
- transport medium returns to heart via open-ended vessel
open circulatory system in insects/invertebrates
- insect blood = haemolymph (doesn’t carry O2 or CO2)
- haemolymph transports nitrogenous waste & cells to defend against disease
- heart extends along abdomen & thorax of insect.
Why can’t a steep concentration gradient be maintained in open circulatory systems?
The amount of haemocoel flowing to a particular tissue cannot be varied to meet demand, as is an open cavity w/ no blood vessels.
closed circulatory system (general)
- Blood fully enclosed in vessels
- No direct contact with cells
- Heart pumps blood at high pressure through progressively smaller vessels
- substances diffuse through walls of blood vessels (capillaries)
- blood vessels widen or narrow to adjust amount of blood going to tissues
- blood pigment carries respiratory gases
single closed circulatory system definition
blood passes through 2-chambered heart once for every complete circulation of the body
problems with single closed circulatory system’s efficiency
- blood passes through 2 sets of capillaries before returning to heart
- blood pressure drops due to narrow capillaries = slowly returns to heart = limits efficiency of exchange process
- suitable for low activity animals
single closed circulatory system in fish.
very active & efficient system
- countercurrent gas exchange system in gills in first set of capillaries = takes O2 from water
- oxygenated blood becomes deoxygenated as is carried to body capillaries.
- body weight supported by water
- don’t need to maintain body temp = reduced metabolic demands, so can be very active.
Why are there 2 sets of capillaries in a single closed circulatory system?
1st: O2 & CO2 exchanged
2nd: substances exchanged between blood & cells
double circulatory system definition
Blood passed through 4-chambered heart twice for every complete circulation of the body
(only pass through 1 set of capillaries before returning to heart = maintain high pressure)
what are the 2 circulations in a double closed circulatory system?
pulmonary: heart -> lungs
- blood picks up O2 and unloads CO2
systematic: heart -> body
- releases O2 to cells that need it & return to heart
blood vessel components (3)
elastin fibres: stretch & recoil, flexible vessel walls
smooth muscle:
- constrict & relax to change lumen size
collagen: structural support & maintains shape/volume of vessel
Arteries
- carry oxygenated blood away from heart
- high pressure, maintained by narrow lumen
exceptions:
pulmonary artery - carries deoxygenated blood to lungs
umbilical artery - carries deoxygenated blood foetus to placenta
structure of arteries:
thick elastic: withstand force of blood & stretch to take more blood
- stretch and recoil in between heart contractions
- provides continuous blood flow, but you feel a pulse when the heart contracts as elastic fibres aren’t strong enough to eliminate pulse
endothelium thin lining:
smooth for blood to easily flow over
narrow lumen: withstand higher pressure
arterioles
- link arteries & capillaries
- more muscle, less elastin than arteries
VASOCONSTRICTION: smooth muscle contracts, preventing blood flow into capillary bed
VASODILATION: smooth muscle relaxes, increasing blood flow into capillary bed
capillaries
- link arterioles with venules
- very narrow lumen, so reed blood cells travel single file
-1 cell thick of endothelium slows rate of blood flow = more time for gas exchange - exchange substances through gaps in endothelium
- oxygenated blood enters from arterioles, deoxygenated blood leaves venules
Veins
- carry deoxygenated blood from cells into heart
(exception = pulmonary vein carries oxygenated blood from lungs into heart) - no pulse (lost after entering narrow capillaries)
- low blood pressure
- lots of collagen & little elastin
- wide lumen & thin lining = easy blood flow
- have valves which prevent backflow of blood
Vein adaptations for pumping blood against gravity under low pressure:
valves: flaps/infoldings of inner lining. close to prevent blood flowing backwards
bigger veins run through active muscles: muscles contract, squeezing veins, forcing blood towards heart
breathing movement of chest acts as pump: pressure changes move blood to heart
tissue fluid
- dissolved substances move out gaps in endothelium
- large plasma proteins (eg albumin) can’t move out = lowers water potential
- water moves into blood from surroundings = oncotic pressure
- blood flowing through arteriole end has high hydrostatic pressure due to heart contractions
- hydrostatic pressure higher than oncotic, so fluid squeeze out capillaries = TISSUE FLUID
- substances from tissue fluid diffuse into cells
- As blood moves through capillaries, hydrostatic pressure decreases as fluid moves out & pulse is lost
- oncotic pressure now higher than hydrostatic pressure at venule end
- ## blood returns to veins w/ 90% tissue fluid
What is the purpose of albumins?
- large plasma proteins
- can’t fit through fenestrations in endothelium
- lowers water potential in blood
- so that water moves into blood from surrounding fluid = oncotic pressure
define tissue fluid
fluid cells are soaked in to facilitate substance exchange between cell & blood
oncotic pressure value (kPa)
-3.3kPa
role of lymphatic system
- remove excess fluid & waste from spaces between cells
- absorb fatty acids from digestive system & deliver to body cells
- Role in immune system & defence
