Haematology Flashcards
What is blood?
A connective tissue
What are the 3 functions and their sub-functions of blood?
1) Transport:
- Oxygen from the lungs to the tissues & CO2 from the tissues to the lungs, for excretion
- Nutrients from digestive tract tissues & cell wastes from the tissues to excretory organs (kidneys)
- Hormones secreted from the endocrine glands to their target cells/tissues
- Heat from active tissues to less active tissues
2) Protection:
- Antibodies: migrate to areas for infection (inflammation)
- Clotting factors: coagulate in order to prevent the loss of blood from a ruptured blood vessel
3) Regulation:
- Fluid/electrolyte balance
- Hormones
- pH of the blood plasma
- Temperature
What proportion of the body does blood make up (%)?
Man = 7% Women = less than 7% Children = more than %
What are the 2 components of blood and their %’s?
1) Plasma (matrix) = 55%
2) Cellular components = 45%
What are the 7 components of blood plasma?
1) Mainly water (90-92%)
2) Plasma proteins (7%)
3) Mineral, inorganic salts
4) Organic waste products
5) Nutrients
6) Hormones
7) Gases
3 Properties of the plasma proteins:
1) They remain within the blood vessels as they are too large to pass through the capillary pores within the capillary bed.
2) Responsible for: maintaining the OSMOTIC PRESSURE (normal: 25 mmHg) in order to keep the water component of the blood plasma within the blood vessel.
If the plasma proteins where not produced/moved out of the blood vessels, the water would follow are OEDEMA would occur!
3) Responsible for: maintaining the VISCOSITY of the blood. The viscosity of the blood can be used as a measure of how well the body’s response is to particular diseases.
What is Oedema?
When the plasma proteins are not produced/move out of the blood vessels so water follows.
Osmotic pressure is lower than 25mmHg.
What are the different plasma proteins:
1) Albumin: (most abundant plasma protein)
Produced: in the liver.
Responsible for: Maintaining the normal osmotic pressure of blood & transports lipids and steroid hormones within the blood.
2) Globulin:
Produced: Mainly liver & the rest in lymphoid tissue.
Responsible for: Immunoglobulins (antibodies) that will bind to specific antigens –> important in immunity, transport certain hormones and mineral salts & inhibit some protease enzymes.
3) Clotting factors (e.g. Fibrinogen)
Produced: Liver
Responsible for: Coagulation of the blood
What is blood called if it doesn’t contain clotting factors?
Serum
Inorganic (mineral) salts:
Responsible for: Maintaining a balance of acids and alkalis (in order to maintain the normal pH of the blood).
Also involved in:
1) Cell formation
2) Secretion formation
3) Nerve impulse transmission
4) Muscle contraction
Normal pH of blood:
Slightly alkaline (7.35 - 7.45)
Nutrients:
Absorbed from the digestive tract into the blood. They are required by cells for: 1) Energy 2) Heat 3) Cell repair and replacement 4) Cell secretion production 5) Production of other blood components
Organic waste products:
1) Products of protein metabolism (urea, creatinine & uric acid) which are produced in the liver and transported to the kidney for excretion
2) CO2 which is produced by all tissues and transported to the lungs for excretion
Hormones:
Produced by endocrine glands and transported via the blood to target tissues/glands. Responsible for influencing cellular activity
Gases:
O2, CO2 & N+ (atmospheric nitrogen)
O2 and CO2 can be transported in the blood in haemoglobin (in RBC’s).
CO2 dissolved in plasma = BICARBONATE IONS.
Ways of obtaining a blood sample:
1) Venepuncture
2) Thumb/heel prick (mainly in babies)
What are the 3 types of blood cells that make up the cellular component of blood?
1) Erythrocytes = Red blood cells
2) Leukocytes = White blood cells
3) Thrombocytes = Platelets
Development of blood cells/bone marrow
1) All blood cells originate from pluripotent stem cells
2) Before they can enter the blood they must undergo HAEMOPOIESIS (which occurs in red bone marrow)
Red marrow = takes up the capacity of bones (in the 1st few years of life)
Yellow fatty marrow = replaces the red bone marrow (over the next 20 yrs of life)
Haemocrit (aka PCV = packed cell volume)
The total volume (%) of erythrocytes in 1L of blood.
How to discover the haemocrit?
Using a centrifuge which separates the components of the blood (plasma from the cellular component).
Order of separation (bottom to top) = erythrocytes - leukocytes - plasma
Haemocrit levels in men and women:
Men: 40 - 54%
Women: 37 - 47 %
Developmental process (erythropoiesis) and lifespan of erythrocytes:
Development: (formed in red bone marrow)
1) Stimulus: Hypoxia (low levels of oxygen reaching cells -detected by the kidneys)
2) Stimulates kidneys and liver to release erythropoietin (hormone)
3) Erythropoietin stimulates proerythroblasts to be developed from pluripotent stem cells.
4) Erytrhopoiesis: Maturation of proerythroblasts and the formation of haemoglobin.
(takes 7 DAYS)
4) Once the erythrocytes are released into circulation = last for 120 DAYS.
What is erythropoiesis and what are its 2 stages?
The development of erythrocytes from pluripotent stem cells (lasts 7 days).
Stages: 1) Maturation of the cell of proerytroblast 2) Formation of haemoglobin
First stage of erytropoiesis: 1) Maturation of the proerythroblast:
Cell decreases and nucleus is removed.
Requires: Vitamin B12 and Folic Acid
Absorbed from diet and stored in the liver.
Vitamin B12 required glycoprotein for:
1) it’s absorption and
2) (when binds to glycoprotein) protection from enzyme digestion
When will the effects be seen of low levels of vitamin b12 and folic acid?
Vitamin B12 = effects won’t be seen for year due to the high stores in the liver.
Folic acid = effects will be seen within a few months
Second stage of erythropoiesis: 2) Formation of haemoglobin:
Haemoglobin is produced inside the developing erythrocyte during erythropoiesis.
Haemoglobin properties:
Contains globin and 4 haem groups. Each haem group can carry one O2 molecule.(oxyhaemoglobin)
Fully saturated haemoglobin = 4 molecules of O2.
Can help to carry CO2 to the lungs for excretion.
What gives blood its red colour?
Oxyhaemoglobin
Control of erythropoiesis:
Negative feedback mechanism.
Hypoxia is the stimulus for erythropoietin to be released from kidneys and liver, in order for the stimulation of erythropoiesis to take place.
Once there is enough oxygen supplying the cells, then erythropoietin is no longer excreted.
Definition and causes of hypoxia:
Def: Deficiency of oxygen supplying the body cells
Causes:
1) Heaemorrhage = loss of erythrocytes, so loss of haemoglobin.
2) Haemolysis = breakdown of erythrocytes, breakdown of haemoglobin
3) High altitude = less O2 in the air