lesson 14 video + study guide Flashcards
3 types of circulatory system
No circulatory system
open circulatory system
closed circulatory system
How does circulation work in animals with no circulatory system (e.g., Hydra, sponges)?
They use diffusion and gastrovascular cavities to move materials.
hemolymph
circulatory fluid in open systems, mixing with body fluids.
open circulatory system
The heart pumps hemolymph into body cavities where it bathes organs directly.
Which organisms use open circulatory systems
Insects, mollusks, arthropods
What defines a closed circulatory system
Blood is confined to vessels (arteries, capillaries, veins) and is separate from body fluids.
Which animals have closed circulatory systems
Earthworms, vertebrates (fish, amphibians, reptiles, mammals)
Why is a closed circulatory system more efficient?
It allows faster, more controlled delivery of oxygen and nutrients.
What percentage of blood is plasma
55
percentage of blood is rbcs
45
percentage of blood is wbc and platelets
less than 1%
function of plasma
Transports water, proteins, nutrients, hormones, and waste
What is the role of red blood cells (erythrocytes)
Carry oxygen using hemoglobin
What is the role of white blood cells (leukocytes)?
Fight infections and are key to immune response
What do platelets do in the blood
Help clot blood by forming fibrin threads at injury sites
hematopoiesis
The formation of new blood cells from bone marrow stem cells
What is erythropoietin (EPO) and its function
A hormone from the kidneys that stimulates RBC production when oxygen is low
How many heart chambers do fish have?
Two chambers – 1 atrium and 1 ventricle
How many heart chambers do amphibians have?
Three – 2 atria and 1 ventricle (with some mixing of blood)
How is the reptile heart more advanced than the amphibian heart?
It has a partially or completely divided ventricle to separate oxygenated and deoxygenated blood.
What major adaptation do mammals and birds have in their hearts?
A four-chambered heart with complete separation of oxygenated and deoxygenated blood
Why is the four-chambered heart important?
It allows high-efficiency circulation, necessary for endothermy (warm-bloodedness)
path of blood
Body
Vena cava
Right atrium
Right ventricle
Pulmonary artery
Lungs
Pulmonary vein
Left atrium
Left ventricle
Aorta
Body
Which vessels carry oxygenated blood?
Pulmonary vein, aorta, systemic arteries
Which vessels carry deoxygenated blood
Vena cava, pulmonary artery, systemic veins
What is the difference between pulmonary and systemic circulation?
Pulmonary = heart → lungs
Systemic = heart → body
What is the role of lymph nodes
Filter lymph and house white blood cells (immune defense)
What is the function of the foramen ovale in a fetus?
Shunts blood from right atrium to left atrium, bypassing lungs
What is the ductus arteriosus
A vessel that connects pulmonary artery to aorta, bypassing fetal lungs
What does the umbilical vein do
Delivers oxygenated blood from placenta to fetus
What do the umbilical arteries do?
Return deoxygenated blood from fetus to placenta
What is the SA node and what does it do?
The pacemaker of the heart; initiates heartbeat in right atrium
What role does the AV node play
Delays the signal, then sends it through Purkinje fibers to the ventricles
What is systolic pressure
Blood pressure when ventricles contract (higher number)
What is diastolic pressure
Blood pressure when ventricles relax (lower number)
Arteries
Carry blood away from heart
Thick, elastic walls; high pressure
Veins
Return blood to the heart
Thinner walls; have valves to prevent backflow
Capillaries
Exchange materials with tissues
One cell thick; site of gas/nutrient exchange
What helps veins return blood to the heart?
Skeletal muscle contractions and one-way valves (venous pump)
What happens at the capillary level
Exchange of oxygen, CO₂, nutrients, and waste
lymph
Plasma that leaks out of capillaries and becomes tissue fluid
How is lymph returned to circulation?
Through the lymphatic system, which drains into veins near the heart
What causes fluid to return into the capillaries from tissues
Osmotic pressure from retained plasma proteins
