b12 transport

Angioplasty - The use of a catheter to insert a small deflated balloon into a blocked or

narrowed artery. Once in place, the balloon is inflated, widening the artery. In some

cases a stent may be inserted into the lumen.

Aorta - The artery that takes oxygenated blood away from the heart to the body.

Arteriole - A type of blood vessel that connects the arteries and capillaries.

Artery - A type of blood vessel that carries blood away from the heart to the tissues, under

high pressure. The walls of the arteries contain thick layers of smooth muscle and elastic

fibres.

Aspirin - A drug used to treat coronary heart disease by preventing the formation of

blood clots in the arteries.

Atria - The two upper chambers of the heart that receive blood from the veins and pump

blood into the ventricles. The muscular walls of the atria are thinner than that of the

ventricles.

Atrioventricular (AV) valves - The valves found between the atria and ventricles. They

prevent the backflow of blood from the ventricles into the atria. There are two types of

AV valves: bicuspid and tricuspid.

Bicuspid valves - The atrioventricular valves found between the left atrium and left

ventricle.

Blood - A tissue containing red blood cells, white blood cells, platelets and plasma.

Blood clotting - A defence mechanism that prevents excessive blood loss and the

entry of harmful microorganisms. It involves platelets and the conversion of

fibrinogen to fibrin to form a mesh over the wound.

By-pass surgery - A surgical procedure involving the use of a blood vessel from

another region of the body (e.g. leg, arm) to divert blood around a blockage in the

coronary artery.

Capillaries - Thin, narrow blood vessels that connect the arteries and veins. They are the

site of exchange of substances between the blood and the tissues.

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Circulatory system - The transport system in mammals consisting of a pump, blood vessels

and valves.

Coronary arteries - The arteries that supply the heart muscle with food and oxygen.

Coronary heart disease - A disease caused by the build-up of fatty deposits inside the

coronary arteries, narrowing them and reducing blood flow to the heart tissue. Risk factors

include a diet high in saturated fats, stress, lack of exercise, smoking, age, genetic

predisposition and gender.

Double circulatory system - A circulatory system found in mammals in which the

blood flows through the heart twice in two circuits. Blood is pumped from the heart to

the lungs before returning to the heart. It is then pumped around the body, after which

it returns to the heart again.

Electrocardiogram (ECG) - A technique used to measure the spread of electrical activity

through the heart by measuring tiny changes in the skin's electrical conductivity. This

produces a trace which is used to detect abnormalities in heart rhythm.

Heart sounds - The sounds (‘lub-dup’) of the heart valves opening and closing. The ‘lub’

represents the closure of the valves between the atria and ventricles. The ‘dup’ signifies the

closure of the valves between the ventricles and the arteries.

Lactic acid - The product of anaerobic respiration in animal cells. Lactic acid build-up

inhibits anaerobic respiration and results in cramp and fatigue.

Lymph - Modified tissue fluid that drains into the lymphatic system.

Lymphatics - See ‘Lymphatic vessels’.

Lymphatic system - A collection of organs and tissues which drain lymph from the

blood and which are involved in immunity.

Lymphatic vessels - Thin-walled vessels that carry lymph through the lymphatic

system. They have valves ensuring the flow of lymph in one direction only. Also

known as lymphatics.

Lymph nodes - Swellings located at intervals in the lymphatic vessels that store and

release lymphocytes into the lymph.

Lymphocyte - A type of white blood cell that produces antibodies specific to a

particular antigen.

Phagocyte - A type of white blood cell that engulfs pathogens and digests them in a

process known as phagocytosis.

Phagocytosis - The process by which white blood cells (phagocytes) engulf and destroy

pathogens.

Plasma - The main component of the blood that carries red blood cells. It is a yellow liquid

containing blood cells, soluble nutrients, ions, carbon dioxide and hormones.

Platelets - Small fragments of cells that are involved in blood clotting.

Pulmonary arteries - The arteries that carry deoxygenated blood away from the heart to the

lungs.

Pulmonary veins - The veins that carry oxygenated blood from the lungs to the heart.

Pulse rate - The number of pulses felt in an artery (e.g. radial artery) per minute.

Red blood cell - A type of blood cell that is anucleate and biconcave. It contains

haemoglobin which enables the transport of oxygen and carbon dioxide to and from the

tissues.

Renal arteries - Blood vessels that carry oxygenated blood to the kidneys.

Renal veins - Blood vessels that drain the kidneys.

Semilunar valves - A pair of valves found between the ventricles and arteries. They

prevent the backflow of blood from the arteries into the ventricles.

Septum - The wall of muscle separating the left side from the right side of the heart. It

prevents oxygenated and deoxygenated blood from mixing.

Shunt vessels - Blood vessels that directly link the arterioles to the venules, allowing

blood to bypass the capillaries. They can control blood flow via constriction and

dilation.

Single circulatory system - A circulatory system in which the blood travels one circuit.

Blood flows through the heart and is pumped around the body before returning to the

heart. Single circulatory systems are found in fish.

Stent - A small, hollow tube that can be surgically implanted into the lumen of arteries

to keep them open.

Tissue fluid - The fluid that surrounds the cells of animals. It has the same

composition as plasma but does not contain red blood cells or plasma proteins.

Tricuspid valves - The atrioventricular valves found between the right atrium and right

ventricle.

Valves - Structures in the heart that prevent the backflow of blood.

Vein - A type of blood vessel that carries blood towards the heart under low pressure. It has

a wide lumen, smooth inner lining and valves. The walls of the veins contain some smooth

muscle and little elastic fibre.

Vena cava - The vein that returns deoxygenated blood to the heart from the body.

Ventricles - The two lower chambers of the heart that receive blood from the atria and expel

blood into the arteries. The muscular wall of the left ventricle is thicker than that of the

right ventricle.

Venule - A type of blood vessel that connects the capillaries and veins.

White blood cells - Cells of the immune system that protect the body from invading

pathogens. They play a role in phagocytosis and in the production of antibodies. Two types:

phagocytes and lymphocytes.

Alveoli - Tiny, thin-walled air sacs in the lungs which serve as the gaseous exchange

surface.

Breathing rate - The number of breaths taken per minute.

Bronchi - Divisions of the trachea that lead into the lungs.

Bronchioles - Many small divisions of the bronchi.

Cilia - Hair-like structures found on ciliated cells that waft substances across the

surface of the tissue in one direction.

Ciliated cell - A type of epithelial cell that lines the surface of the respiratory tract.

Ciliated cells are covered in tiny hair-like structures known as cilia.

Diaphragm - A large sheet of muscle that separates the thorax and the abdomen.

Exchange surface - A surface over which materials are exchanged from one region to

another. An effective exchange surface has a large surface area, thin layers, a good blood

supply and ventilation to maintain a steep diffusion gradient.

Expiration - During expiration (exhalation) the diaphragm relaxes and reverts to a

dome shape. The internal intercostal muscles contract, pulling down the ribcage. The

volume of the thorax decreases and thoracic pressure rises above air pressure. Air

moves out of the lungs.

Expired air - The air that is breathed out. It has a higher concentration of carbon dioxide and

water vapour than inspired air and a lower concentration of oxygen.

External intercostal muscles - A set of muscles found between the ribs on the inside

that are involved in forced exhalation.

Gaseous exchange - The exchange of respiratory gases between an organism and its

environment.

Goblet cells - Specialised cells located in the epithelial lining of the trachea, bronchi,

and some bronchioles that secrete mucus.

Inspiration - During inspiration (inhalation) the diaphragm contracts and flattens and

the external intercostal muscles contract, raising the ribcage. The volume of the

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thorax increases and thoracic pressure falls below air pressure. Air moves into the

lungs.

Inspired air - The air that is breathed in. It has a higher concentration of oxygen than

expired air and a lower concentration of carbon dioxide and water vapour.

Intercostal muscles - Groups of muscles situated between the ribs. They control rib

movement.

Internal intercostal muscles - A set of muscles found between the ribs on the outside

that are involved in forced and quiet inhalation.

Larynx - A hollow, tubular structure located at the top of the trachea involved in breathing,

and the production of sound.

Limewater - A chemical used to test for the presence of carbon dioxide. It turns milky when

carbon dioxide is present.

Lungs - A pair of air-filled organs located on either side of the chest. They contain the

alveoli, the gaseous exchange surface.

Mucus - A slimy substance secreted by goblet cells. It forms a thin, sticky film over

the internal lining of the respiratory tract, trapping pathogens and particles and

preventing their entry into the alveoli.

Ribs - A set of bones that surround and protect the chest cavity.

Trachea - The primary airway which carries air from the nasal cavity down into the chest. It

is a tube supported by incomplete rings of cartilage which provide structural strength.

Ventilation - The movement of fresh air into the lungs and stale air out of the lungs via

inspiration and expiration.