Blood Flashcards
(30 cards)
Blood
Blood can be described as an opaque, viscous fluid when compared to water. It is bright red in color when oxygenated (in the arteries) and darker red in color when de-oxygenated (in the veins). The pH of blood is close to neutral, ranging from 7.35-7.45 and its temperature is slightly higher than that of the rest of the body, at 38 oC.
The average adult has about 5 liters of blood circulating in the body at any one point in time, but this is variable from person to person depending on body size. Blood comprises two components: blood plasma (between 46-63% of total blood volume) and the formed elements of blood (around 37-54% of the total blood volume). The proportion of plasma to formed elements of the blood varies depending on a wide range of factors, including the sex of the individual.
BLOOD PLASMA
Blood plasma is a clear yellow fluid comprised mainly of water (91.5%), in which several organic and inorganic molecules are dissolved. The majority of substances found in blood are proteins transported within the plasma. Blood plasma also contains nutrients, electrolytes, dissolved gases, organic waste products, and signaling molecules, such as hormones. The components of blood plasma also affect the osmotic pressure.
Osmotic pressure
Osmotic pressure is the result of a difference in solute concentration between two fluids, separated by a semi-permeable membrane which is impermeable to the solutes. As a result, the solvent (water) will move towards the side with the higher solute concentration. The pressure difference between the two sides is the osmotic pressure.
Albumins
Albumins are a group of transport proteins produced by the liver that carry steroid hormones and fatty acids. In addition, they produce the colloid osmotic pressure of blood (which tends to ‘pull’ water into the circulation from the interstitial fluid). Albumins also act as a blood buffer, helping to keep the pH of blood stable.
Fibrinogens
Fibrinogens are a family of blood clotting proteins produced by the liver.
Globulins
Globulins are proteins produced in the liver and by B cell lymphocytes. Alpha and beta globulins transport fat-soluble vitamins, lipids, and iron. Gamma globulins, particularly the immunoglobulins (also known as antibodies) contribute to the immunological response of the body.
Globulins
Globulins are proteins produced in the liver and by B cell lymphocytes. Alpha and beta globulins transport fat-soluble vitamins, lipids, and iron. Gamma globulins, particularly the immunoglobulins (also known as antibodies) contribute to the immunological response of the body.
Enzymes
Enzymes are proteins that catalyze chemical reactions, increasing the rate at which the reactions take place. Blood plasma contains various enzymes, and transports them to their site of action.
Nutrients
Products of digestion are absorbed into the bloodstream for distribution throughout the body. They are used for energy production (ATP), growth of the body, and cell maintenance. These include; amino acids, monosaccharides, fatty acids, glycerol, vitamins, and minerals.
Electrolytes
Electrolytes are small, inorganic ions that help regulate and maintain osmotic pressure. These include sodium, potassium, calcium, chloride, and bicarbonate.
Dissolved gases
Small amounts of oxygen are carried in blood plasma (most is bound to hemoglobin in red blood cells). Carbon dioxide is carried dissolved in blood plasma.
Organic waste products
Waste products of metabolism are carried in the blood to the organs of excretion (kidneys, skin, lungs, and liver). These include: urea, creatinine, ammonia, uric acid, and bilirubin.
Hormones
Hormones are secreted by endocrine organs. They alter the physiological activity of their target cell and travel to this target cell via the bloodstream. Hormones may be proteins (known as peptide hormones) or non-proteins. Peptide hormones include insulin and growth hormone and non-peptide hormones include cortisol and epinephrine.
Red blood cells
Red blood cells, or erythrocytes, are the most abundant cells found in the blood. These cells are specially designed to carry oxygen and carbon dioxide around the body to and from actively respiring cells.
White blood cells
White blood cells, or leukocytes, form the other principle cell component of blood. There are various different types of white blood cells, each with a specialized function. In general however, white blood cells function as part of our body defense against foreign substances and pathogens entering the body, and the removal of cellular debris.
Platelets
Platelets are fragments of cells found suspended in blood plasma along with red and white blood cells. They are abundant in blood plasma and play a key role in blood clotting mechanisms.
Erythropoiesis
- In adults, new red blood cells are produced in the red bone marrow in flat and irregular bones, and the proximal ends of long bones
- Red blood cells arise from multipotent stem cells called haemocytoblasts.
- Myeloid stem cells are derived from multipotent stem cells and differentiate into erythroblasts.
Proerythroblast
- Earliest distinguishable red blood cell precursor
Erythroblast (normoblast)
- Last stage of red blood cell with a nucleus, which then disintegrates
- Haemoglobin synthesis occurs and iron molecules accumulate
Reticulocyte
- Contains fragments of the endoplasmic reticulum
- Usually found in bone marrow, with a small percentage in circulation
Erythropoietin
- A hormone produced in the kidneys which stimulates an increase in red blood cell production
- Produced when the body is in a state of hypoxia, or lack of oxygen
Life cycle of a red blood cell
- Red blood cells circulate for ~120 days
- At this stage their membranes begin to disintegrate and damaged cells are removed by macrophages in the liver, spleen, and red bone marrow
What happens to the iron?
- Returned to the red bone marrow to produce new red blood cells
- If not needed for erythropoiesis then iron is stored in the liver
What happens to the haemoglobin?
- Globin, the protein portion of haemoglobin, is digested to its amino acids to be used for the synthesis of new proteins
- Haem cannot be recycled and is converted to bilirubin by macrophages, which is removed from circulation by the liver and excreted into bile
- Bile is secreted into the small intestine and is eliminated in the faeces.
Erythrocytes (red blood cells)
- Thin, disc-shaped, bi-concave cells (increases surface area to carry more oxygen)
- Thin, disc-shaped cells, about 7.5µm in diameter
- Bind oxygen in the lungs and carry it to tissues throughout the body where it is exchanged for the waste product carbon dioxide
- Do not have a nucleus and are absent of most organelles, leaving space for large amounts of haemoglobin.
Haemoglobin
- Consists of protein (globin)- 4 polypeptide chains + organic molecule (haem) with an iron at centre
- Iron weakly binds to oxygen molecules
- Each haemoglobin binds to 4 oxygen molecules (one bound to each iron)
- This oxygen is released into interstitial fluid for diffusion into cells
- Haemoglobin is bright red when combined with oxygen, but is dark red when oxygen is lost to the body tissues
