Structure and function of open and closed systems

What are the functions of the circulatory system?

* Distribution of nutrients
* Support for metabolism (O2 delivery, transportation of CO2 and metabolic waste products)
* Distribution of water and electrolytes.
* Transportation and distribution of hormones.

What are the principle components of circulatory systems?

* A fluid that circulates through the system - transport
* A propulsive mechanism that drives fluid flow by applying a force - generates pressure gradient
* A system of tubes or channels through which the fluid flows
* A system of one-way valves or septa that ensure unidirectional flow of the fluid

What is an open circulatory system?

* Fluid is open to body cavities and cells
* Most molluscs, arthropods and some annelids
* Lower pressure system
* Less efficient

What are the features of an open circulatory system?

* Incomplete system of vessels
* Circulating fluid, known as ***haemolymph*** - contains respiratory stuff just not necessarily in cells
* haemolymph flows through vessels and freely percolates through

intercellular spaces
* heart(s) may propel the haemolymph through vessels
* haemolymph bathes the internal organs and therefore directly reaches every cell of the body

What is an open circulatory system in insects

* Insects use their tracheal systems to transport nutrients and CO2
* Circulation can be less efficient when respiratory gases are handled through a separate system

What is a closed circulatory system?

* Fluid is enclosed within the system and does not contact cells directly
* All vertebrates, cephalopod molluscs and some annelids
* Higher pressure system
* More efficient

What are the features of a closed circulatory system?

* complete and continuous system of blood vessels
* fluid in vessels is ***blood***
* heart(s) propels blood through vessels
* intercellular spaces filled with interstitial fluid (composition different from blood)
* lymph in lymphatic vessels
* Blood remains in vessels and therefore separate from cells of the body

Where does diffusion occur in a closed circulatory system?

Diffusion occurs between blood vessels and interstitial fluid at the capillary beds

What features differ in closed circulatory systems between species?

* Pump - anatomy of the heart varies (number of chambers and arrangement of inflow/outflow vessels)
* Distribution vessels - circulation patterns vary (single, double)

What is required for an efficient circulatory system?

* Efficient O2 carriers (proteins/cells) in blood or haemolymph
* Efficient gas exchange in the respiratory system (O2 in/CO2 out) Efficient delivery of nutrients and O2
* Diversification of oxygenated fluids to systemic organs and deoxygenated fluids to respiratory organs
* Fast flow of fluids


* Efficient gas exchange in tissues (O2 out/CO2 in)

How is flow rate calculated?

Driving force/Resistance

How do flow rates differ in open and closed systems?

* Closed - driving force is high and resistance is high
* Open - driving force is low and resistance is low
* Allows both to maintain a high flow rate

What is the functions of the mammalian cardiovascular system?

* Distribution of O2 and nutrients
* Transportation of CO2 and removal of metabolic

waste products
* Distribution of water, electrolytes and hormones
* Thermoregulation
* Immune system infrastructure

What is the arrangement of the mammalian cardiovascular system?

* Four-chambered heart (unidirectional flow)
* Blood supplies to systemic vascular beds run in parallel
* Pulmonary circulation runs in series
* High-pressure system

How is the cardiovascular system adapted to function?

* Heart provides force
* Distribution vessels
* Blood vessels offer resistance