M3 Topic 7: Blood Flashcards
(30 cards)
What is blood?
Type of liquid connective tissue which acts as transport medium for the body
- Consists of cells and liquid extracellular matrix
Functions of blood
- Transportation
- Regulation
- Protection
Blood role in transportation of substances
- Delivers oxygen from lungs to tissues, transporting carbon dioxide from tissues to lungs for elimination
- Transport of nutrients from gastrointestinal (GI) tract to tissues
- Transport of metabolic and waste products to organs such as liver and kidneys for breakdown and elimination
- Transport of hormones from endocrine organs to target organs and tissues
Blood role in regulatory functions
- Regulates body temp by absorbing and distributing heat throughout body, including to the skin to encourage cooling
- Maintain acid/base balance of body fluids by regulating and buffering pH
- Regulate circulatory fluid volume by minimising movement of fluid from blood to tissues
Blood role in protective functions
- Prevent blood lose after wound or injury by forming blood clot at site of damage
- Prevent infection via presence of immune cells & blood proteins
What happens when you put blood into a centrifuge?
Plasma at top as it is less dense, erythrocytes at bottom, buffy coat in between
Components of blood
Liquid component
- Plasma
Cellular component (cells and cell fragments)
- Formed elements
Plasma
Pale yellow fluid from extracellular matrix, less dense component
- Makes up 55% of blood volume
Composed of wide range of substances dissolved in it
- Electrolytes
- Nutrients
- Metabolic and waste products
- Circulating hormones
- Gases (O2, CO2)
- Plasma proteins (e.g. albumin)
Albumin
Plasma protein that helps maintain osmotic pressure of blood
Haematocrit
Volume percentage of red blood cells in blood volume
Buffy coat
The remaining formed elements
- Leukocytes
- Platelets
Makes up less than 1% of blood volume
Formed elements
Cells and fragments in blood
3 types…
- Erythrocytes
- Leukocytes
- Platelets
Leukocytes
White blood cells which play vital role in defence against disease
Different types of leukocytes play unique roles in protecting body from pathogens
- Macrophages
- Neutrophils
- T cells
Platelets
Fragments of larger cells known as megakaryocytes
- Not true cells, lack a nucleus (thus cannot divide or reproduce)
- Short life-span, around 10 days in circulation
Critical part of haemostasis (blood clotting)
Haemostasis
Process that stops bleeding
- Without platelets, high risk of losing large amounts of blood even through small cuts and wounds
Erythrocytes
Red blood cells that transport oxygen within body
- Make up 45% of total blood volume
- Most abundant type of blood cell
- Live for 100-120 days in circulation
Structure of erythrocytes
Small cells shaped like biconcave discs (flattened discs with depressed centres)
- Very simple structure, no nucleus or other organelles
- Thus, cannot replicate, but does free up a lot of space inside cell for haemoglobin
Strong & flexible PM and cytoskeleton
- Allows for squeezing through narrow capillaries w/o damage
- Pretty much flexible ‘bags’ of haemoglobin, highly suitable for role as oxygen transporter
Haemoglobin
Iron-containing protein that reversibly binds and transports oxygen
- Gives erythrocytes red colour
How does blood become oxygenated?
As erythrocytes pass through lungs, each haemoglobin molecule picks up and binds 4 oxygen molecules, oxygenating the blood
How does blood become deoxygenated?
As the oxygenated blood passes through tissues, oxygen is released from haemoglobin, diffusing into the tissues
- Erythrocytes contain no mitochondria, thus they don’t consume any oxygen transported
How many haemoglobin molecules does each erythrocyte have?
Around 250 million molecules
- Thus 1 single red blood cell can transport around 1-billion molecules of oxygen
Haematopoiesis
Formation of blood cells and formed elements
- Takes place in red bone marrow
Haematopoietic stem cell
Precursor of all different blood cells and formed elements
- Found in red bone marrow
Capacity to develop into…
- Erythrocytes
- Leukocytes
- Platelets
depending on chemical signals received by bone marrow
Example…
- Invading pathogens stimulate production of leukocytes
- Hormones regulate production of erythrocytes
Erythropoiesis
The process of erythrocyte production
