Chapter 17 Blood Flashcards
What is the hematocrit of red blood cells(blood fraction)
Erythrocytes normally constitute about 45% of the total volume of a blood sample
In healthy males the norm is 47% +/- 5%
In healthy females the norm is 42% +/- 5%
What is Blood Composition
Blood: a fluid connective tissue composed of
Plasma Formed elements Erythrocytes (red blood cells, or RBCs) Leukocytes (white blood cells, or WBCs) Platelets
Describe the physical characteristics and volume of blood
Blood is a sticky, opaque fluid with a characteristic metallic taste.
- Depending on the amount of oxygen it is carrying, it varies from scarlet (oxygen rich) to dark red (oxygen poor).
- Blood is more dense than water and about five times more viscous due to its formed elements mainly.
- Slightly alkaline with a pH between 7.35-7.45
- Accounts for approximately 8% body weight
- Males; 5-6L, females; 4-5L
Define blood’s 3 main roles
- Distributing substance
- Regulating blood levels
- Protecting the body
Describe the distribution functions of blood
- Delivering oxygen from the lungs and nutrients from the digestive tract to all body cells
- Transporting metabolic waste products from cells to elimination sights - to the lungs to eliminate carbon dioxide and to the kidneys to dispose of nitrogenous wastes in urine
- Transporting hormones from the endocrine organs to their target organs
Describe the regulatory functions of blood
- Maintaining appropriate body temperature by absorbing and distributing heat throughout the body and to the skin surface to encourage heat loss
- Maintaing normal pH in body tissues.
- Maintaing adequate fluid volume in the circulatory system. Blood proteins prevent excessive fluid loss from the bloodstream into the tissue spaces.
Describe the protective functions of blood
- Preventing blood loss. When a blood vessel is damaged platelets and plasma proteins initiate clot formation, halting blood loss
- Preventing infection. Drifting along in blood are antibodies, complement proteins and white blood cells, all of which help defend the body against foreign invaders such as bacteria and viruses
Describe blood plasma and its constituents
Are plasma proteins used as fuel for body cells?
NO! They aren’t used as fuel for body cells because their presence in blood is required to perform many key functions
Describe plasma proteins
Plasma proteins account for about 8% of plasma weight. Most plasma proteins are produced by the liver, except for hormones and gamma globulins. All contribute to osmotic pressure and maintaing water balance in blood and tissues; all have other functions as well, e.g. transport, enzymatic
Describe the formed elements of blood; erythrocytes, leukocytes and platelets
- Erythrocytes have no nuclei or organelles and platelets are cell fragments. Only leukocytes are complete cells
- Most of the formed elements survive in the bloodstream for only a few days
- Most blood cells do not divide. Instead, stem cells divide continuously in red bone marrow to replace them.
- Erythrocytes vastly outnumber the other types of formed elements
Describe the structure of erythrocytes
Are small cells, about 7.5um in diameter. Shaped like biconcave discs, flattened discs with depressed centres, they appear lighter in colour at their thin centres than at their edges.
Describe red blood cells structure to function relationship
*Structural characteristics contribute to gas transport
* Biconcave shape—huge surface area relative to volume
* >97% hemoglobin (not counting water)
* No mitochondria; ATP production is anaerobic; no O2 is used
in generation of ATP
* A superb example of complementarity of structure and function!
Describe some functions of erythrocytes
- RBCs are dedicated to respiratory gas transport
- Hemoglobin binds reversibly with oxygen
- Can bind and disassociate with oxygen
- Haemoglobin structure;
- Protein globin: two alpha and two beta chains
- Heme pigment bonded to each globin chain
- Iron atom in each heme can bind to one O2 molecule
- Each Hb molecule can transport four O2
Describe haemoglobin
Is the protein that makes red blood cells red, binds easily and reversibly with oxygen and most oxygen carried in blood is bound to haemoglobin
