The Structure & Function of the Circulatory System Copy
CARDIOVASCULAR SYSTEM
The cardiovascular system includes the heart, blood vessels and blood cells. The blood is the transport system of the body making sure that the
body is provided with the essential nutrients it needs to function. The blood cells play a crucial role in fighting infection and providing immunity.
FUNCTIONS OF BLOOD
Our blood can be described as our life force, making sure our cells have all the essential supplies they need and keeping micro-organisms at bay.
The blood has several essential functions. These functions can be divided into two main areas:
■ Transportation (provides nutrients to cells, removes waste and carries hormones to target organs)
■ Protection (Cells in the blood defend the body against invasion of micro-organisms and their toxins)
Blood accounts for 7–9 per cent of our total body weight and we have approximately 5.6 litres of this red viscous liquid flowing around our body. Around 55 per cent of blood is plasma and the other 45 per cent is made up from the different blood cells. The volume and concentration of our blood must be kept within narrow limits to maintain homeostasis
Blood supply to head, face and body
Oxygenated blood travels heart via the aorta and is pumped to the common carotid arteries located on either side of the neck, here the blood supply divides into the internal and external carotid arteries. The internal carotid artery passes through the temporal bone behind the ear to supply the brain with blood. The external carotid artery remains outside the skull and feeds the occipital, temporal and facial arteries, skin and muscles of the face.
Arteries divide into smaller vessels called arterioles and then into capillaries. These capillaries are one cell thick to allow nutrients and oxygen to pass into the tissues through capillary exchange, waste products are collected and the blood is returned back to the heart via venules which then enlarge to form veins.
The scalp, face and neck are drained by the internal and external jugular veins, which carry the blood from the head via the occipital, temporal and facial veins and feed back into the subclavian vein at the base of the neck and chest region where the blood is returned to the heart via the superior vena cava.
List of arteries located in the head and face:
- Occipital artery
- Right internal carotid artery
- Temporal artery
- Facial artery
- Right external carotid artery
- Right common artery
List of veins located in the head and face:
- Occipital vein
- Right external jugular vein
- Temporal vein
- Facial vein
- Right internal jugular vein
use the link below for labelled diagrams