Module 3, section 2: Transport in animals.

What things do transport systems transport?

Hormones, antibodies, sugars and waste products.

How are a double and single circulatory system different?

A double circulatory system does two complete circuits of the body, and blood passes through the heart twice.

Define a closed circulatory system.

Blood is enclosed within vessels (arteries, veins etc.)

Define open circulatory systems.

Blood freely flows through the body cavity, as it does in invertebrates.

Why is the artery inner lining folded?

Allows the artery to expand under high blood pressure.

Function of elastic tissue in the artery?

Allows artery to stretch and recoil in response to being filled with blood.

How are arterioles different to arteries?

Smaller lumen than arteries, branch into capillaries. Their pressure is also far lower, and they do not feature valves.

Describe the function and structure of capillaries.

Smallest blood vessel, one cell thick to ensure most efficient gas exchange. Very small lumen.

Describe venules.

Small blood vessels that capillaries branch into, to return deoxygenated blood to the heart. Have little smooth muscle, and a large lumen to accommodate for high volume of blood. Contain valves.

What do valves do, and which blood vessels contain them?

They prevent backflow of blood. Venules and veins contain them, as well as the pulmonary artery and the aorta.

What is tissue fluid?

Fluid that surrounds cells in tissue.

What is tissue fluid comprised of?

Substances that leave the blood plasma, oxygen, water and nutrients.

Why isn’t there any proteins or white blood cells in tissue fluid?

Proteins are too big to leave capillary walls. Metabolic waste is released into tissue fluid.

Pressure filtration?

Hydrostatic pressure forces fluid out of the capillaries, forming tissue fluid.

Define oncotic pressure.

Increase in concentration of plasma proteins, due to water moving out of the capillaries. Water reenters at the venule end.

Describe the lymphatic system.

Contains extra fluid from the blood, which is eventually returned to the blood via lymph vessels.

Where does lymph fluid end up?

Ends up in near the heart, and is returned to the heart there.

What are other functions of the lymphatic system.

Contains white blood cells, acts as a component of the immune system.

How does tissue fluid become lymph?

Diffuses from surrounding cells into lymph capillaries, which then move toward main lymph vessels, that contain valves to prevent backflow.