Lecture 7 Flashcards
What are the two main circulatory systems in vertebrates?
1) Cardiovascular system (transports blood)
2) Lymphatic system (transports lymph)
What is the function of the circulatory system?
It transports fluids (blood and lymph) throughout the body using a network of vessels and pumps.
What does the cardiovascular system transport?
Oxygen (O₂), carbon dioxide (CO₂), water, ions, fuel (proteins, fats, carbohydrates), signaling molecules (hormones), metabolites (lactate), and waste.
What are the main components of the cardiovascular system?
1) Fluid (Blood)
2) Vessels
3) Muscular Pump (Heart)
What are the three main components of blood?
- Plasma – Contains water, dissolved gases (O₂, CO₂), ions, fuel, signaling molecules, carrier proteins, vitamins/minerals.
- Buffy Coat – Contains white blood cells (immune cells) and thrombocytes (platelets).
- Erythrocytes (Red Blood Cells - RBCs) – Transport respiratory gases via hemoglobin.
How does blood differ from hemolymph?
Blood contains red blood cells (RBCs) with hemoglobin, while hemolymph (in invertebrates) lacks RBCs and uses open circulation.
What is hematocrit (Hct)?
The percentage of whole blood made up of erythrocytes (RBCs).
What is the function of hemoglobin (Hb)?
It binds and transports O₂ and CO₂ in the blood.
How does O₂ transport occur in the blood?
O₂ is loaded onto hemoglobin in the lungs/gills and unloaded at aerobic tissues via simple diffusion.
Why are smaller RBCs advantageous?
They allow faster diffusion of O₂ due to a shorter diffusion distance.
What makes mammalian RBCs unique compared to other vertebrates?
They lack a nucleus and mitochondria, making them more efficient at oxygen transport.
What are the different types of blood vessels?
- Arteries – Carry blood away from the heart, high pressure.
- Capillaries – Sites of gas/nutrient exchange, very thin walls.
- Veins – Return blood to the heart, lower pressure, often contain valves to prevent backflow.
What are the three types of capillaries?
- Continuous – Least permeable, found in skin, muscle, lungs.
- Fenestrated – Medium permeability, found in kidneys, gut, endocrine organs.
- Discontinuous – Most permeable, found in liver, spleen, bone marrow.
How does blood move through capillaries?
By diffusion for small molecules (e.g., gases, nutrients) and bulk flow for fluids driven by pressure gradients.
What is the difference between single and double circulation?
Single circulation (fish) – Blood passes through the heart once per cycle (heart → gills → body → heart).
Double circulation (amphibians, reptiles, mammals, birds) – Blood passes through the heart twice per cycle (heart → lungs → heart → body).
How does blood flow through a fish’s circulatory system?
- Deoxygenated blood flows from the heart → ventral aorta → afferent branchial arteries → gills.
- Oxygenated blood leaves the gills via efferent branchial arteries → dorsal aorta → body tissues.
- Deoxygenated blood returns to the heart via veins.
What is the main problem with single circulation?
- Oxygen problem – The heart pumps only deoxygenated blood, which limits oxygen supply to cardiac muscle.
- Pressure problem – Blood pressure drops after passing through gills, leading to slow circulation.
What are the four layers of the vertebrate heart?
- Pericardium – Fluid-filled sac surrounding the heart.
- Epicardium – Outer connective tissue.
- Myocardium – Heart muscle (cardiomyocytes).
- Endocardium – Inner lining.
What is the function of pacemaker cells in the heart?
They spontaneously depolarize to generate action potentials, setting the heart’s rhythm.
How does fish heart contraction occur?
- Sinus venosus (pacemaker) initiates contraction.
- Atrium contracts and pushes blood to the ventricle.
- Ventricle contracts, pushing blood into the conus/bulbus arteriosus.
- Bulbus arteriosus (elastic) or conus arteriosus (contractile) dampens pressure before blood reaches the gills.
How do Antarctic icefish survive without hemoglobin?
They have high bulk flow rates and absorb O₂ directly through their plasma.
What helps fish maintain venous return (blood flow back to the heart)?
- Skeletal muscle contractions help squeeze veins.
- One-way valves prevent backflow.
- Smooth muscle in veins helps push blood forward.
What is coronary circulation, and why is it important?
It provides oxygenated blood to the heart muscle (important in active fish and warm environments).
