chapter 18: the blood

the blood powerpoint

composition

• the blood is the medium for transport of substances around the body

• composed of

  • mostly water plasma (54-58%)

  • red blood cells (41-45%)

  • everything else (1% white blood cells, platelets, proteins, etc)

formed elements

• three types of elements in the blood

  • erythrocytes (99% of cells)

  • leukocytes

  • platelets

• the hematocrit is the percentage of total blood occupied by erythrocytes

  • around 42% in women and 45% in men

• plasma is 90% water

plasma

• consists of water and other substances

• 90% water which is a transport medium for all blood borne substances, ions, gases, nutrients, hormones and plasma proteins (10%)

• majority of the 10 is plasma proteins (8%)

plasma proteins

• establish an osmotic gradient between blood and interstitial fluid (osmotic pressure)

• proteins buffer ph changes

• aid in transport of blood-borne substances (hormones, etc)

• function in immunity as antibodies

• fibrinogen is a key factor in blood clotting

plasma proteins

• albumin

• complement

• fibronectin

• inorganic salts

• glycocalyx

erythrocytes = oxygen transport

• rbc also transports co2 and hydrogen ions

• diameter of an erythrocyte is about 8um

• cell lacks a nucleus, organelles and ribosomes

  • does not go through mitotic division because no nucleus

• mainly a package of hemoglobin molecules and iron

• flat, biconcave, disc scape is well suited to carry out its main function to carry oxygen

• plasma membrane of the erythrocyte is flexible, allows it to slide through a capillary

hemoglobin

• consists of 2 parts

• globin is 4 folded polypeptide chains

• the heme (iron) part is non protein, each of the 4 iron atoms is bound to one of the polypeptides and can combine with one molecule of oxygen gas

• hemoglobin can also combine with co2, hydrogen ions, carbon monoxide and nitric oxide

• hemoglobin can buffer ph by binding to hydrogen ions

rbc

• bone marrow produces erythrocytes

• erythropoiesis (erythrocyte production) is the production of new red blood cells, replacing the worn out cells in circulation

• average lifespan of a rbc is 120 days

• do not reproduce

• number of rbc normally remains constant

erythropoiesis

• controlled by erythropoietin

• if oxygen delivery to tissues is decreased, kidneys detect this and increase output of erythropoietin and erythropoiesis increases

• erythropoietin can be produced synthetically in the lab

homeostatic imbalance

• anemia - lower than normal oxygen carrying capacity of the blood

• types of anemia

  • nutritional anemia - low iron

  • pernicious anemia - b12 deficiency

  • aplastic anemia - failure of bone marrow to make enough rbc

  • renal anemia - kidney disease

  • hemorragic anemia - loss of blood

  • hemolytic anemia- rupture of rbc

  • sickle cell disease

polycythemia

• excess in circulating erythrocytes

• produces an elevated hematocrit

• primary is caused by tumorlike condition in the bone marrow

• secondary is an erythropoietin-induced adaptive mechanism to improve oxygen carrying capacity in the blood

leukocytes

• one of the other main constituents of the blood is the wbc

• form one of the body’s major means of defense against foreign invasion

• agranular

  • lymphocytes

  • monocytes

• granular

  • basophils (b shape)

  • neutrophils (3+)

  • eosinophils (2 facing)

platelets

• last components of the blood

• allow blood to clot to prevent uncontrolled bleeding

• hemostasis

function of platelets

• also called thrombocytes

• function in hemostasis

• remain functional for around 10 days

• hormone thrombopoietin increases the number of platelets

• platelets are cell fragments derived from undifferentiated blood cells from the bone marrow

• overall production is not well known

hemostasis

• prevents blood loss from damaged blood vessels

• 2 steps to stop blood escape

  • vascular spasm then platelet plugging

• then once it stops it forms a blood clot