As Biology Transport in mammals

Components and layers of arteries and veins

Inner layer:

• Endothelium to minimize friction with the moving of blood

• Elastic fibres - recoil and retract

Middle layer:

• Smooth muscle - contract steadily

• Collagen

• Elastic fibres

Outer layer:

• Elastic fibres and collagen fibres

The process of blood flowing into blood vessels

As the high pressure of blood flows into the elastic arteries, the artery walls stretch as the high pressure blood surges into them, and then recoil inwards

=> Wider lumen to reduce the pressure

Blood at lower pressure enters an artery, the artery wall recoils inwards => raising the pressure

Muscular arteries are found where arteries has a higher proportion of muscles in their walls

=> They divide into arterioles

Their narrowness causes resistance to blood flow

=> slow down, providing time for exchange of gases and nutrients as the blood flows through the capillaries in the tissues

Nerve impulses from the brain can cause their smooth muscle to contract, narrowing the arteriole

=> Vasoconstriction

=> Vasodilation

Tissue fluid and its movement in and out of the capillaries

its compositions are water, amino acids,… It has far fewer protein molecules, contains white blood cell

Tissue fluid is the leak of plasma from the capillaries

At the arterioles end of the capillary bed, the blood pressure is high which increases the hydrostatic pressure that pushes the water and the solutes (tissue fluid)
Although there is a higher concentration of protein in the capillaries, the water still moves out into the tissue fluid

At the venule end of the capillary bed, the blood pressure decreases where as the solute (waste products, urea,…) concentration gradient is steep inside the capillary

Two types of circulation in the double circulation system

Double circulation: a circulatory system in which the blood passes the heart twice on one complete circuit of the body
Systemic circulation: bring oxygenated blood to the body

Pulmonary circulation: brings oxygenated blood to the heart from the lungs

Structure of artery

Muscular artery

Elastic artery

Arteries

Function: -       Transport blood at high pressure Inner layer: -       Endothelium ð Minimize with friction with the moving blood -       Elastic fibres – Recoil and retract Allows the wall to be stretch  => Pulse

Middle layer: -       Smooth muscles – contracts, reducing blood flow into the arterioles Controls the volume of blood entering the tissue

Outer layer: -       Elastic fibres -       Collagen - Strength, structure, flexibility

CO2 is transported via

Dissolved in plasma (5%)

carbaminohaemoglobin (10%)

Hydrogen carbonate ions (85%)

Carbonic anhydrase is an enzyme in the cytoplasm of the red blood cells which catalyses the production of carbonic acid from CO2

CO2 + H2O => H2CO3

H2CO3 => HCO3- + H+ (reversible reaction)

Structure of vein