Circulatory System

1. Circulation 

Diffusion is not enough for larger organisms 

A. circulatory system: an organ system that moves blood and lymph throughout animal’s body 

• Can be open (many arthropods)

• Or closed (all vertebrate, large/complex animals)

• 1. Cardiovascular system

  • cardio/vascular ‘heart/blood vessels’

  • Pulmonary ‘lungs’

  • heart= pump. vessels=transportation

  • Always circulated to lungs/ respiratory organs 

Systemic circulation ( thai s throughout the body) in different kinds of animals  

Fish (DIAGRAM). Its a single loop

• Two chambered 

• One atrium 

• One ventricle 

• Atrium > ventricle> gills>capillaries in body>back to atrium

Amphibians (DIAGRAM)

• Three chambered

• Two atria 

• One ventricle 

• Right atrium> ventricle> capillaries in body and to lungs/ skin> lungs go to left atrium> back to ventricle> capillaries in body go back to right atrium 

• Mixing of oxygenated and deoxygenated blood in ventricle 

Reptiles (similar to amphibian heart) (DIAGRAM)

• Three chambered 

• Two atria 

• One ventricle (septum divides ventricle reducing mixing of oxygenated and deoxygenated blood) 

• Right atrium receives deoxygenated blood from body 

• Left atrium receives oxygenated blood from lungs

• Both atria empty into a single ventricle, but septum (wall) prevents blood from lungs and body from mixing too much 

Mammals (DIAGRAM)

• Four chambers 

• Two atria

• Two ventricles 

• Double loop circulation 

• Arteries: vessels that carry blood away from the heart (DIAGRAM)

  • arterioles , then branch into capillaries 

  • Capillaries transport/diffusion of gases, nutrients, waste, hormones. Happens thru capillaries

  • Venules then veins  

• Veins: vessels that carry blood to the heart 

• Surface area is increased via branching, maximized by capillaries 

• Exchange at capillaries:  movement of fluid (and nutrients and hormones etc) and diffusion of gasses out of blood plasma to the interstitial fluid surrounding the cells and back into the blood (DIAGRAM)

Cardicac function 

• 1. Systol- contracting 

• 2. Diastole- relaxing 

• 3. Valves 

• 4. Cardiac cycles of contraction 

Blood pressure

• 1. Systolic value

• 2. Diastolic value 

• 3. Measuring blood pressure with a sphygmomanameter

• 4. How blood pressure changes across the circulatory system.

  • If capillaries are so small, you would expect fluid velocity and pressure to increase, like putting your thumb over the end of a garden hose. So why does it decrease. 

  • Massive increase in cross sectional area at the capillaries results in decreasing velocity