Lesson 6 - Specialised transport systems in mammals Flashcards
What can supply everything the cell needs to import and export via:
- Diffusion
- Osmosis
- Active transport
- Exocytosis
- Endocytosis
Why do multicellular organisms need transport systems?
- Metabolic demands of most multicellular animals are high, so diffusion over long distances is not enough to supply quantities needed and remove waste.
- SA:V smaller as multicellular organisms get bigger. Smaller SA to absorb or remove substances becomes relatively smaller.
- Molecules (hormones & enzymes) may be in one place but need to be transported to another
- Food digested in one organ, but needs to be transported to every cell in the body for aerobic respiration and other aspects of cell metabolism.
- Waste products of metabolism need to be removed from cells and transported to excretory organs.
Features of circulatory system:
- Have liquid transport medium that circulates around the system
- Vessels that carry transport medium
- Pumping mechanism to move the fluid around the system
When substances are transported in a mass fluid with a mechanism moving the fluid around the body
Mass transport system
Open circulatory system:
Blood is not enclosed in vessels, and it circulates in open space.
How open circulatory system works?
- Very few blood vessels to contain transport medium
- Pumped straight from heart into body cavity
- In haemocoel transport medium is under low pressure
- Comes into direct contact with cells and tissues
- Transport medium returns to heart through an open ended vessel
What is the body cavity called?
Haemocoel
Where does gaseous exchange take place in the open system?
Haemocoel
Where are open-ended vessels found?
Invertebrate animals:
- Insects
- Molluscs
Insect blood =
Haemolymph
What doesn’t haemolymph carry and why?
Oxygen and carbon dioxide:
- Gaseous exchange occurs in tracheoles
What does haemolymph carry in the blood?
- Food
- Nitrogenous waste products
- Cells involved in defence against disease
How is the open system of an insect structured?
Haemocoel split by a membrane and heart extends along length of the thorax and the abdomen of the insect.
Haemolymph flow?
Circulates but steep concentration gradient can not be maintained for efficient diffusion. The amount of haemolymph flowing to a particular tissue can not be varied to meet changing demands.
Closed circulatory system:
Blood enclosed in blood vessels and does not come directly into contact with cells of the body.
How does closed circulatory system work?
- Heart pumps blood around body under pressure and relatively quickly, and blood returns directly to heart.
How does gaseous exchange occur in a closed system?
Substances leave and enter blood by diffusion through the walls of the blood vessels.
How is quantity of blood delivered to cells altered in a closed system?
Widening / narrowing the blood vessels
What is the blood pigment for?
To carry respiratory gases.
Where are closed systems found? (what phyla)
- Echinoderms
- Cephalopod molluscs
- Annelid worms
- Vertebrate groups
Echinoderms:
Sea urchins and starfish
Cephalopod molluscs:
Octopods and Squids
Annelid worms:
common earthworms
Where are single closed circulatory systems found?
Annelids and fish
Single closed circulatory system:
Blood flows through the heart once for every complete circulation.
How many sets of capillaries does the blood pass through in one circuit in a single closed circulatory system?
two
1: exchange oxygen and carbon dioxide
2: Different organ systems. Substances exchanged between blood and cells.
What is the result of passing through 2 sets of capillaries in a single closed circulatory system?
Blood pressure decreases and blood returns to the heart very slowly.
This limits limits the efficiency of the exchange processes, so the activity levels of animals with a single closed circulatory system needs to be relatively low.
What is the exception to the low activity level rule for single closed circulatory systems?
Fish
How is a fish’s metabolic rate decreased?
- Efficient gaseous exchange (counter-current flow)
- Body weight is supported by the water
- Do not need to maintain body temperature due to water
Double closed circulatory system is present in?
Birds and most mammals
How does double closed circulatory system work?
- Blood is pumped from the heart to the lungs to pick up oxygen and unload carbon dioxide, and then returns to the heart.
- Blood flows through the heart and is pumped out to travel all around the body before returning again.
Pulmonary circulation:
heart and lungs
Systemic circulation:
heart and body / other organs
Definition of double circulatory system:
Blood travels through the heart twice for each complete circulation.
How is high pressure and fast flow maintained?
Blood only passes through one network of capillaries in each circuit.