Circulatory systems and hearts
Function of circulatory systems
- To transport necessary materials to animal’s cells
- To transport waste products away
Circulatory system design
- Gastrovascular cavity
o Simple
o One cavity functions as digestive tract and sort of circulatory system
o Cnidarians, jellyfish, hydra
o As animal moves, this cavity is squeezed and churned, some also have cilia
- Open circulatory system
· have a pump (heart)
· but no blood vessels
· it is just pumped into the body cavity and sloshes around
· the more the animal moves, the more the fluid moves around, makes it more efficient
· insects and mollusks have this
· fluid is called hemolymph
- closed circulatory system
o have a pump (heart)
o and fluid (blood) stays within blood vessels all the time
o mostly “higher” organisms, but also worms
o active lifestyles
o advantage
§ can pump blood to where it is most needed, like active tissues or gut when digesting a meal
Design of closed circulatory systems – two types
- single circulation (fish) (Fig. 47.4a)
o heart has two chambers
§ atrium, to collect blood from tissues
§ ventricle, to pump blood out of heart
o blood goes from heart to gills
§ gases exchanged – CO2 from tissues leaves, O2 from water comes in
§ blood is at low pressure here
§ this is disadvantage in getting blood to rest of tissues, it must happen at low pressure
- double circulation (crocs, birds, mammals) (Fig. 47.4c)
o heart has four chambers
o blood is pumped through two distinct circuits, and never mixes
§ pulmonary – blood from the right side of the heart goes to the lungs
§ systemic – blood from left side of heart goes to the tissues
o deoxygenated blood is collected from body in right atrium
o goes to right ventricle
o goes from right ventricle to lung, where gas exchange occurs
o goes back to left atrium
o goes to left ventricle
o goes out to body at high pressure and velocity – good for efficient gas exchange
- intermediate circulation (amphibians and reptiles) (Fig. 47.4 b)
o partial separation of pulmonary and systemic circulation
o two atria, but one ventricle
o so oxygenated and deoxygenated blood is mixed
Blood
- connective tissue (has matrix (fluid) between cells)
- transports O2 (to cells) and CO2 (to lungs or gills) and also lots of other things
o hormones
o glucose
o proteins
o etc.
- has cellular and fluid part
o cellular
§ RBCs (by far majority 99.9%)
· To transport O2
· Live about 120 days, constantly being made and destroyed
· In humans no nucleus or most organelles
o Anemia – too few RBCs
o Polycythemia – too many RBCs
· Packed with hemoglobin (Fig. 47.7)
o O2 carrier of blood
o Made of 4 chains of protein globin
o Plus heme
§ O2 carrier, so each hemoglobin carries 4 O2
§ Carried on iron atom
§ WBCs
· Immune system
§ Platelets
· Initiate blood clotting
§ If centrifuge blood, cell volume is hematocrit
· 38% men, 46% women
o Fluid (plasma)
§ 90% water
§ Various other, glucose, salts and ions, proteins
The Heart
- two atria
o right atrium collects blood from body
o left atrium collects blood from lungs
- separated by one-way atrioventricular valves from ventricles
- ventricles
o collect blood from atria
o pump to
§ right ventricle to lung
§ left ventricle to rest of body
§ one-way valves here too (semilunar valves)
· First vessels to branch are coronary arteries which supply O2 to heart muscle. It does not get O2 from the blood inside the chambers.
Contraction
- atria contract first, then ventricles
- begins in sinoatrial node in rt atrium. Wave of depolarization causes atria to contract.
- The depolarization is spread to ventricles a fraction of a second later by atrioventricular node because of connective tissue which separates atria from ventricles. AV node is cardiac muscle.
o contraction of ventricles is called systole (systolic pressure)
o relaxation is diastole (diastolic pressure)
§ these can be measured by sphygmomanometer in your peripheral arteries
§ Normal is 120/80 for male, about 10-15 less for women. Measured in sphygmomanometer in mmHg.
EKG
- Electrocardiogram (Fig. 47.11)
- measures electrical activity of the heart
- P, QRS, T waves happen when different things happening in heart