Blood and Blood Products Flashcards
Describe the formation of blood
Fluid running through arteries and veins. Bright red. Cells are suspended in plasma. 55% plasma and 45% formed elements.
What are the characteristics of blood?
Heavier, more viscous than water. Accounts for 7% of body weight. Temperature 38 degrees centigrade. Oxygenated blood saturation 98-99%
Deoxygenated blood saturation 75%.
The pH is 7.35-7.45
Describe plasma
Slightly alkaline. yellow in colour. 90% water. 10% dry matter
Organic substances: glucose, lipids, proteins, hormones, amino acids and vitamins
Describe blood cells
Basic structural and functional units. Microscopic. Shaped differently. Special cells (erythrocytes, leucocytes). Includes platelets.
Describe red blood cells
Erythrocyte. Most numerous, biconcave lens shape. Their function is to provide oxygen to tissues and recovers carbon dioxide as waste. carries haemoglobin. They have a life span of 120 days.
Describe white blood cells
Leucocyte. Their function is defence and immunity. Less numerous. They come in 2 categories, granulocytes have multi lobed nuclei and agranulocytes have a large nucleus
Describe a platelet
Thrombocytes. Smaller than erythrocytes. Intense purple colour. Stops loss of blood through promoting blood coagulation
What are antigens?
The presence or absence of certain antigens determines your blood group. In the ABO system there are 2 possible antigens A and B
Describe antibodies
Associated with each blood group are specific antibodies. These antibodies are capable of attacking antigens from other ABO groups
What is the Rhesus factor?
The positive or negative sign next to the blood groups is known as the Rhesus (Rh) factor. The Rh factor is an inherited protein that can be found on the surface of the red blood cell. If your blood type is positive, then your blood cells have the Rh protein/antigen.
What effect can having the antibodies to the rhesus antigen have?
When does the response to the rhesus happen?
The response come after the birth of the first fetus. Then in subsequent pregnancies maternal antibodies can cross the placenta and damage the fetus. Ant-D gamma-globulin (injection) given to the mother immediately after the first birth will result in the Rh+ cells not being recognised and antibodies are not produced.
How does blood volume change during pregnancy?
Blood volume increases by 30-50%
More in multiple pregnancies and correlates with birth weight.
How is there capacity for the increased blood volume?
Progesterone and oestrogen relax vascular smooth muscle causing vasodilation and decreased peripheral resistance
Describe haemoglobin in pregnancy
As plasma volume increases haemoglobin concentration falls- reaching its lowest point at 16-22 weeks. Normal adult Hb- 12-15 (g/dl). Pregnancy level is 10.8-14.6
