Respiration is the uptake of oxygen and the removal of carbon dioxide from the body.
This job is performed by the lungs.
Breathing is achieved by contraction and relaxation of the diaphragm and rib muscles.

What are the two types of veins?

1. Systemic Veins are located all throughout the body from your arms to your legs and transport oxygen-depleted blood back to your heart.

2. Pulmonary Veins transport oxygen-rich blood from your lungs to your heart. Each lung features two sets of pulmonary veins, a left and right…[Read more]

Arteries carry blood from the heart to various organs of the body under high pressure so they have thick and elastic walls. Veins collect the blood from different organs and bring it back to the heart. The blood is no longer under pressure, so the walls are thin with valves to ensure that blood flows only in one direction.

No, veins are generally smaller than arteries:
Arteries
The largest artery, the aorta, is about 10–25 mm in diameter. Arteries start large and branch into smaller vessels called arterioles. Arteries have thick walls that appear round in cross section because of the high pressure of blood being pumped away from the heart.
Veins
Veins range in s…[Read more]

The human digestive system consists of the gastrointestinal tract plus the accessory organs of digestion. Digestion involves the breakdown of food into smaller and smaller components, until they can be absorbed and assimilated into the body.

The nervous system helps all the parts of the body to communicate with each other. It also reacts to changes both outside and inside the body. The nervous system uses both electrical and chemical means to send and receive messages.