Chapter 17 - A&P2

transport

• Delivering )2 and nutrients to body cells

• Transporting metabolic wastes to lungs and kidneys for elimination

• Transporting hormones from endocrine organs to target organs

Regulation

• Maintaining body temperature by absorbing and distributing heat

• Maintaining normal pH using buffers: alkaline reserve of bicarbonate ions

• Maintaining adequate fluid volume in circulatory system

Protection

• Preventing blood loss

  • Plasma proteins and platelets in blood initiate clot formation

• preventing infection

  • agents of immunity are carried in blood

    • antibodies

    • complement proteins

    • white blood cells

composition of blood

• blood is the only fluid tissue in the body

plasma

• matrix is nonliving fluid

formed elements

• living blood cells

  • cells are suspended in plasma

• erythrocytes (red blood cells)

• leukocytes (white blood cells)

• platelets

• Only white blood cells are complete cells

  • Red blood cells have no nuclei or other organelles

  • pltelets are cell fragments

• Most formed elements survive in the bloodstream for only a few days

• Most blood cells originate in bone marrow and do not divide

spun tube of blood yields three layers:

• erythrocytes on the bottom (45% of whole blood)

  • normal values (males 47% Females 42%)

• white blood cells and platelets in buffy coat(<1%)

  • thin, whitish layer between red blood cells and plasma layers

• plasma on top (55% of whole blood)

hematocrit

percent of blood volume that is red blood cells

physical characteristic of blood

• sticky, opaque fluid with metallic taste

• color varies with O2 content

  • high O2 levels show a scarlet red

  • low O2 levels show a dark red

Volume of blood

• pH 7.35-7.45

• make up 8% of body weight

• average volume

  • Males: 5-6 L

  • Females: 4-5 L

Blood Plasma

• straw colored sticky fluid

  • about 90% water

Over 100 dissolved solutes found in blood plasma

• nutrients, gases, hormones, wastes, proteins, inorganic ions

• Plasma proteins are the most abundant solutes

  • remain in blood: not taken up by cells

  • proteins produced mostly by liverthe

  • Albumin: makes up 60% of plasma proteins

    • functions as a carrier of other molecules, as a blood buffer, and contributes to plasma osmotic pressure

structural characteristics of Erythrocytes

• small diameter (7.5 um) cells that contribute to gas transport

• cell has biconcave disc shape, is anucleate, and essentially has no organelles

• filled woth hemoglobin for gas transport

• red blood cell diameter are larger than some capillaries

• contain plasma membrane protein spectrin and other proteins

  • Spectrin provides flexibility to change shape

3 features that make for efficient gas transport

• biconcave shape offers huge surface area relative to volume for gas exchange

• hemoglobin makes uo 97% of cell volume (not counting water)

• red blood cells have no mitochondria

  • ATP production is anaerobic, so they do not consume O2 they transport

function of Erythrocytes

• red blood cells are dedicated to respiratory transport

• normal values:

  • males 14-18g/100ml

  • Females 12-16 g/100

• new blood cells enter the blood sinusoids

Hemoglobin

• binds reversibly with oxygen

• consists of red heme pigment bound to the protein goblin

  • goblin is composed of 4 polypeptide chains ( 2 alpha and 2 beta)

• a heme pigment is bonded to each globin chain

  • gives blood red color

  • each heme’s central iron atom binds one O2

how many O2 can each Hb molecule transport

four

how many red blood cells do Hb molecules contain

250 million

O2 loading in lungs

produces oxyhemoglobin (ruby red)

O2 unloading in tissues

produces deoxyhemoglobin, or reduces hemoglobin (dark red)

CO2 loading in tissues

20% of CO2 in blood binds to Hb, producing carbaminohemoglobin

Hematopoiesis

• formation of blood cells

• occurs in bone marrow; composed of reticular connective tissue and blood sinusoids

  • in adults its found in the axial skeleton, girdles, and proximal epiphyses of the humerus and femur

Hematopoietic stem cells (Hemocytoblasts)

• stem cell that gives rise to all formed elements

• hormones and growth factors push cell towards specific pathway of blood cell development

• committed cells cannot change

stage 1 of erythropoiesis

Hematopoietic stem cells: transforms into myeloid stem cell

erythropoiesis

process of formation of red blood cells that takes about 15 days 

stage 2 of erythropoiesis

myeloid stem cell: transforms into proerythroblas

stage 3 of erythropoiesis

proerythroblast: divides many times, transforming into basophilic erythroblasts

stage 4 of erythropoiesis

basophilic erythroblasts: synthesize many ribosomes, which stain blue

stage 5 of erythropoiesis

Polychromatic erythroblasts: synthesize large amounts of red-hue hemoglobin; the cell now shows both pink and blue areas

stage 6 of erythropoiesis

orthochromatic erythroblasts: contain mostly hemoglobin, so appear jsut pink; eject most organelles; nucleus degrades, causing concave shape

stage 7 of erythropoiesis

reticulocytes: still contain small amount of ribosomes

stage 8 of erythropoiesis

Mature erythrocyte: in 2 days, ribosomes degrade, transforming mature red blood cells-

• reticulocyte count indicates the rate of red blood cell transformation

Regulation and requirements of erythropoiesis

• too few red blood cells lead to tissue hypoxia

• too may red blood cells increase blood viscosity

• > 2 million red blood cells are made per second

balance between red blood cell production and destruction depends on:

• hormonal controls

• Dietary requirements

Hormonal controls

• erythropoeitin (EPO): hormone that stimulates the formation of red blood cells

  • always small amount of EPO in blood to maintain the basal rate

  • released by the kidneys (some from the liver) in response to hypoxia

    • at low O2 levels, oxygen-sensitive enzymes in kidney cells cannot degrade

    • HIF can accumulate, which triggers synthesis of EPO

• causes of hypoxia:

  • decreased red blood cell numbers due to hemorrhage or increased destruction

  • insufficient hemoglobin per red blood cell

  • Reduced availability of O2

• too many erythrocytes or high oxygen levels in blood inhibit EPO production

• EPO causes erythrocytes to mature faster

  • Testosterone enhances EPO production, resulting in higher RBC counts in males

Dietary requirements for erythropoiesis

• amino acids, lipids and carbohydrates

• iron available from diet

  • 65% of iron is found in hemoglobin, witht he rest in the liver, spleen, and bone marrow

  • free iron ions are toxic so iron is vound with proteins:

    • stored in cells as ferritin and hemosiderin

    • transported in blood-bound protein transferrin

• vitamin B12 and folic acid are necessary for DNA synthesis for rapidly dividing cells such as developing red blood cells

Homeostatic imbalance

• some athletes abuse artificial EPO

  • use of EPO increases hematocrit, which allows athletes to increase stamina and performance

• dangerous consequences:

  • EPO can increase hematocrit from 45% up to even 65%, with dehydration concentrating blood even more

  • blood becomes like sludge and can cause clotting, stroke, or heart failure

Fate and destruction of erythrocytes

• life span: 100-120 days

• Red blood cells are anucleate, so they cannot synthesize new proteins, grow or divide

• old red blood cells become fragile, and Hb begins to degenerate

• Macrophages in spleen engulf and break down dying red blood cells

red blood cells break down: Heme, iron, and globin are separated

• iron binds to ferridin or hemosiderin and is stored for reuse

• heme is degraded to yellow pigment bilirubin

  • liver secretes bilirubin (in bile) into intestines, where ir is degrades to pigment urobilinogen(transforms into brown pigment and leaves the body in feces)

• globin is metabolized into amino acids

  • released into circulation

Erythrocyte Disorders

• most erythrocyte disorders are classified as either anemia or polycythemia

Anemia

• blood has abnormally low O2 carrying capacity that is too low to support normal metabolism

• sign of problem rather than disease itself

symptoms of anemia

• fatigue

• pallor

• dyspnea

• chills

Anemia: 3 groups based on cause

• blood loss

• not enough red blood cells produces

• too many red blood cella being destroyed

Polycythemia

• abnormal excess of red blood cells; increases blood viscosity, causing sluggish blood flow

Polycythemia vera

• bone marrow cancer leading to excess red blood cells

  • hematocrit may go as high as 80%

  • treatment: therapeutic phlebotomy

secondary polycythemia

• caused by low O2 levels (ex: high altitude)

• or increase EPO production

Blood doping

Athletes remove, store, and reinfuse red blood cells before an event to increase O2 levels for stamina

general structure of Leukocytes

• leukocytes or white blood cells are the only formed element that is complete cell with nuclei and organelles

• make up <1% of total blood volume

  • 4800 tp 10800 white blood cells per ul of blood

function in defense against disease of leukocytes

• can leave capillaries via diapedesis

• move through tissue spaces by amoeboid motion and positive chemotaxis

• white blood count is over 11000 per ul

• increase is a normal response to infection

Leukocytes are grouped into two major categories:

• Granulocytes - contain visibly cytoplasmic granules (neutrophils, eosinophils, basophils)

• agranulocytes: do not contain visible cytoplasmic granules (lymphocytes, monocytes)

Mnemonic to remember decreasing abundance in blood:

(Never let monkeys eat bananas)

• neutrophils

• lymphocytes

• monocytes

• eosinophils

• basophils

Granulocytes

• 3 types

  • neutrophils, eosinophils, basophiles

• larger and shorter lives than red blood cells

• contain lobed, rather than circular, nuclei

• cytoplasmic granules stain specifically with wrights stain

• all are phagocytic to some degree

Neutrophils

• most numerous white blood cells

  • account for 50-70# of white blood cells

• about twice the size of red blood cells

• granules contain either hydrolytic enzymes or antimicrobial proteins, defensins

• also called polymorponuclear leukocytes

  • cell has anywhere from 3 to 6 lobes

• very phagocytic

  • reffered to as bacteria slayer

  • killed microbes by process called respiratory burst

    • cell synthesizes potent oxidizing substances (bleach or hydrogen)

• defensin granules merge with phagosole

  • form “spears” that pierce holes in membrane of ingested microbe

eosinophils

• account for 2-4% of all leukocytes

• nucleus has 2 lobes connected by a broad band; resembles ear muffs

• red-staining granules contain digestive enzymes

  • release enzymes on large parasitic worms, digesting their surface

• also play role in allergies and asthma, as well as immune response modulators

Basophils

• rarest white blood cells, accounting for only 0.5-1% of leukocytes

• nucleus deep purple with 1-2 contrictions

• large, purplish black (basophilic) granules contain histamine

• are functionally similar to mast cells

histamine

inflammatory chemical that acts as vasodilator and attracts white blood cells to inflamed cites

Agranulocytes

• lack visible granules

• two types: lymphocytes and monocytes

• both has spherical or kidney shaped nuclei

Lymphocytes

second