Theme 3 Cont. Flashcards
Blood (ECF) in Vertebrates:
- Plasma (water, ions, proteins, nutrients, gas)
- Erythrocytes (RBCs) (contain respiratory pigments – haemoglobin, haemocyanin, etc.)
- Leukocytes (white blood cells) – immune system
- Platelets
Plasma key ions, proteins, and gasses
- Key ions: Na+, K+, Cl-, HCO3-, Ca++, H+
- Key proteins: globulins, albumin, fibrinogens
- Key gasses: O2 and CO2
Erythrocytes (RBCs) increase the capacity of
fluid to carry O2 and CO2
Variation in the circulatory system in vertebrates associated with:
- Whether or not gravity is a factor affecting blood flow (requiring higher pressure)
- Where gas exchange takes place (gills, lungs, or both)
- Thermoregulatory mode (endothermy or ectothermy)
Basal condition in vertebrates (“fish”) – 2 chambers:
- Atrium: thin-walled, receives o2-poor blood from the systemic circulation
- Ventricle: thick-walled, muscular, sends o2-poor blood through the aorta to gills
- Single looped circulatory system
- Low-pressure: gills are not a barrier, effects of gravity are negligible
In tetrapods, the blood has to pass through the delicate lungs
- Requires a low-pressure circuit because pressure would be insufficient to access the rest of the body if lungs and systemic circulation were on the same circuit
- System circuit requires higher pressure to supply much larger volume, work counter to gravity
Tetrapods evolved two separate circuits:
- Low-pressure pulmonary circuit between heart and lungs
- High-pressure systemic circuit between heart and rest of the body
Each of these circuits required its own atrium, and increasing separation of the ventricles into two chambers
Many “reptiles” can bypass the pulmonary circuit while
diving because they can tolerate some mixture of deoxygenated blood and oxygenated blood due to ectothermy and low metabolic rate, thus incomplete separation of the ventricle
Mammals and birds have complete separation,
two circuits can only pass from one to the other at the heart
Endothermy requires efficient delivery of O2 to tissues =
isolation of pulmonary circuit
Why is homeostasis and gas exchange needed?
- Krebs cycle and Oxidative phosphorylation (consumes oxygen and produce carbon dioxide)
- Photosynthesis (consumes carbon dioxide and produces oxygen)
- pH regulation (via CO2 regulation, forms carbonic acid)
- All plants and animals must breathe
Gas exchange in animals* bulk flow and diffusion *
- Ventilation by bulk flow: breathing moves air into and out of the lungs
- Diffusion across the respiratory system: O2 diffuses from the lungs into the blood and CO2 out of the blood into the lungs
- Circulation by bulk flow: O2 and CO2 are transported by the circulatory system to and from the cells
- Diffusion between blood and cells: O2 from blood diffuses into the cells and CO2 diffuses out of the cells into the blood
Gas Exchange With the Environment
Ventilation (breathing):
- Bulk flow between the respiratory medium (air/water) and the gas exchange surface (body surface/lungs/gills/etc.)
- Diffusion is too slow
Gas Exchange Surface:
- Diffusion between the environment (air/water) and the ECF
- Surface area of a gas exchange surface is proportional to mass and metabolic rate
- Surface area/volume relationships are important (large animals need specialized gas exchange structures, and then lungs, gills, book lungs/gills, trachea (not just body surface))
Characteristics of a good gas exchange structure:
- Reflected in Fick’s Law of Diffusion Rate = D A dC/dX
- Large surface area
- Moist
- Thin
- Highly vascularized
