Circulatory system

blood → fluid that transports dissolved substances around the body

blood vessel → tubes that carry the blood to all parts of the body

heart → muscular pump that moves blood around the body

functions:

• transports substances/antibodies
• temperature regulation
• reproduction

Humans have a double circulation

blood structure

plasma 55% → 90% water and other substances

blood cells 45% → red, white, platelets

red blood cells

Cytoplasm full of haemoglobin → transport oxygen from the lungs to the body

can be affected by:

Anaemia → to few red blood cells

carbon monoxide → gas taken up instead of oxygen

high altitudes → less oxygen in the air

white blood cells

monocytes → process phagocytosis

neutrophils → process phagocytosis

lymphocytes → produce antibodies

platelets

non nucleated cell fragments formed in the bone and marrow

prevents executive blood loss from damaged blood vessel

prevents entry of pathogens from damage skin

Blood groups

caused by proteins antigens in red blood cells → ABO system → antigen A attack antigen B and vice versa

transfusion

need to worry about the donor's antigens and the recipient's antibodies

structure of the heart

muscular pump that pushes blood around the blood → cardiac muscle

cells contract at the same time → systole

one complete heartbeat is a cardiac cycle:

diastole → aria and ventricles relax and blood enters the heart

Atrial systole → both atria contract together

ventricular systole →  both ventricles contract together and the aria begin to relax

heart sounds

lubb-dubb → sound caused by the closure of the valves

lubb → closure of the bicuspid and tricuspid valves → louder sound

dubb → closure of the semilunar valves →  softer sound

blood pressure

the blood can be pumped thanks to the high pressure that the heart builds up

pulse

pulse → when the arteries expand and the ventricles contract

cardiac cycle centre→ area of the brain that initiates nerve impulses

adrenaline → produced by the adrenal gland, it increases the heart rate in times of stress

How blood gets back to the heart

veins carry blood at low pressure back to the heart with the help of

• gravity
• Skeletal muscle
• valves
• partial vacuum in chest

tissue fluid → small molecules that leave the capillaries and bathe the body

some tissue fluid drains into blind-ended capillaries and becomes lymph

→ rich in lipids and white cells

lymph nodes → swelling of the lymph