The blood vascular system is made up of four parts:

1. B∕the osmotic balance of the fluids and the cells. The presence of plasma proteins, particularly albumin in the bkx>d. controls the Ilow of fluid between the Iluid compartments and is responsible for maintaining bkx>d volume and bkxxi pressure.

Body Ienyierature- bkxxi conducts heal around the btype of stain they take up. i.e. neutral, basic or acidic. There are three types of granulocytes:

1..Xciitrophils - take up neutral dyes and the granules stain purple (l ig. 7.2). Immature neutrophils have a nucleus that looks like a curved band and are known as ImiikIcells. Neulrophilsarc the most abundant of the leucocytes, forming about 90% of all granulocytes. They are able to move through the endothelial lining of the blood vessels into the surrounding tissues and engulf invading bacteria and cell debris by phagocytosis, thus helping to light disease. A neutrophilia or raised numbers of neutrophils indicates the presence of an infective process while a neιιiropaenia or lack of white cells may be characteristic of certain viral infections.

2. Iλ)sin

infectious hepatitis and viral haemorrhagic disease all cause subcutaneous haemorrhages due to interference with blιχxl clotting

I hrombixytopaenia - lack of platelets may be seen in some forms of leukaemia kick of blιxκl calcium - this feature is used in the lab to prevent blixxJ samples clotting. Chemicals such as FI)^rΓA (ethylene diamine tetra-acelic acid), citrate and oxalate all combine with calcium in the blιxxl and prevent it being involvet! in Iheclotting pnxcss.

The bd from the atria to the ventricles, as it circulates through the heart:

1. Right atrioventricular (AV) or tricuspid valve - this lies between the right atrium and right ventricle and is composed of three Iibrous Ilaps or cusps which attach to a Iibrous ring encircling the opening to the right ventricle

2.

- this lies between the left atrium and left ventricle and is composed of two cusps.

The free edges of the atrioventricular valves are attached to the papillary muscles of the walls of the ventricles by Iibrous threads called the t Iiorduc Iendi- nae (Fig. 73). The atrioventricular valves open to allow the blood to Iill the ventricles from the atria: when the ventricles are full they close to prevent back- Ilow of blood into the atria. The chordae Iendinae pre­vent the valves everting as blood is pressed against them when the ventricles begin to contract. It is (he closing of the AV valves that causes the Iirst heart sound-'lub'.

At the base of (he major vessels leaving (he ventri­cles are two more sets of valves, (he semilunar valves, which prevent the Ilow of IMcmmJ from the vessel back into the ventricle. They are composed of three half­moon shaped cusps and when they shut it causes the second heart sound - ’dub’. The semilunar valves are:

1. Pulmonary valve - lies at the base of the pulmonary artery as it leaves the right ventricle

2. Aortic valve - lies at the base of the aorta as it leaves the left ventricle.