anatomy chapter 18 blood

blood

is the only Fluid tissue -Continuously regenerated connective tissue - made up of formed elements and plasma

formed elements

Cells are living blood cells are suspended in plasma

Plasma

Matrix is nonliving fluid

Erythrocytes

(red blood cells) transport respiratory gases in theblood

Leukocytes

(white blood cells) defend against pathogens

Platelets

help form clots to preventblood loss

blood transport

• Delivering O2 and nutrients to body cells

• Transporting metabolic waste

• Transporting hormones

blood regulation

• Maintaining body temperature

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

• Maintaining adequate fluid volume

blood protection

• Preventing blood loss - Plasma proteins and platelets in blood initiate clot formation

• Preventing infection - Agents of immunity are carried in blood.

volume of blood

Adults have approximately 5 L of blood. Approximately 8% of our total body weight.

Viscosity of blood

blood is 4-5 times thicker than water. Depends on amount of dissolved and suspended substances relative to amount of fluid

blood ph

is slightly alkaline - pH 7.35-7.45

blood color

Color varies with oxygen content

High levels - bright red, Low levels - dark red

Plasma Concentration

of solutes (for example, proteins, ions)

Determines the direction of osmosis across capillary walls

centrifuged blood

Whole blood (plasma and formed elements) separated into parts by centrifuge

Erythrocytes in centrifuge

Bottom, red layer

About 44% of sample

buffy coat in centrifuge

Very thin (1%) middle layer with gray-white color Composed of leukocytes and platelets

plasma in centrifuge

Straw-colored liquid at top of tube

About 55% of sample

Hematocrit

- Percentage of volume of all formed elements

- Clinical definition: percentage of only erythrocytes

- Adult males: 42 to 56%; females 38 to 46%

Blood smear

- Thin layer of blood placed on microscope slide and stained

- Formed elements differ in appearance

- Erythrocytes are most numerous - pink, anucleate, biconcave discs

- Leukocytes - larger than erythrocytes, varied in form, noticeable nucleus

- Platelets - small fragments of cells

Blood Plasma

is straw-colored sticky extracellular fluid

- Similar in composition to interstitial fluid

- About 90-92% water, but plasma has a high protein composition

Over 100 dissolved solutes

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

- Plasma proteins are most abundant solutes (7%)

- Remain in blood; not taken up by cells

- Proteins produced mostly by liver

blood is a Colloid

Plasma contains dispersed proteins

variety of plasma proteins

Albumin, globulins, fibrinogen and other clotting proteins, enzymes, and some hormones

Albumin

makes up 60% of plasma proteins

- Functions as carrier of other molecules, as blood buffer, and contributes to plasma osmotic pressure

plasma proteins exert colloid osmotic pressure

•Prevents loss of fluid from blood as it moves through capillaries

•Helps maintain blood volume and blood pressure

•Can be decreased with diseases, resulting in fluid loss from blood and tissue swelling

•E.g., liver diseases that decrease production of plasma proteins

•E.g., kidney diseases that increase elimination of plasma proteins

Albumins 2

Smallest and most abundant group of plasma proteins(58%)

- Exert greatest colloid osmotic pressure; transport proteins for some lipids, hormones, and ions

Globulins

Second largest group of plasma proteins (37%)

- Smaller alpha-globulins and larger beta-globulins

- Transport some water-insoluble molecules, hormones, metals, ions

Gamma globulins

(immunoglobulins or antibodies) - Part of body's defenses

Fibrinogens

Makes up only 4% of plasma proteins

- Contributes to blood clot formation

regulatory proteins

(Includes enzymes and hormones)

- less than 1% of total proteins

Hematopoiesis

production of formed elements

- Occurs in red bone marrow of certain bones

Hemocytoblast

Hematopoietic stem cells gives rise to all formed elements

- Pluripotent: can differentiate into many types of cells

- Produce two different lines: myeloid line and lymphoid line

Myeloid line

forms erythrocytes, all leukocytes except lymphocytes, and megakaryocytes (cells that produce platelets

lymphoid line

forms only lymphocytes

Colony-stimulating factors (CSFs)

stimulate hematopoiesis

- Hormones and growth factors push cell toward specific pathway of blood cell development

Erythropoiesis

red blood cell production - takes about 15 days

Erythropoiesis requires

iron, B vitamins like B12, folic acid, amino acids

myeloid stem cells

responds to multi-CSF- Forms progenitor cell

Proerythroblast

a large nucleated cell

erythroblast

smaller, produces hemoglobin

Normoblast

still smaller, more hemoglobin, anucleate

Reticulocyte

lacks organelles except ribosomes that make hemoglobin

- Reticulocyte count indicates rate of RBC formation

Erythrocyte

ribosomes have degenerated

Leukopoiesis

production of leukocytes (granulocytes, agranulocytes)

Granulocytes

are neutrophils, basophils, and eosinophils

- Multi-CSF and GM-CSF cause myeloid stem cell to form progenitor cell

-Progenitor cell becomes myeloblast that becomes a granulocyte

Monocyte

(agranulocyte) also derived from myeloid stem cells

- Stem cell differentiates into progenitor cell

- M-CSF prompts progenitor cell to become a monoblast

- Monoblast becomes a promonocyte, which matures into a monocyte

Lymphocytes

(agranulocyte) are derived from lymphoid stem cells

- Stem cells differentiate into B-lymphoblasts and T-lymphoblasts

- Lymphoblasts mature into B-lymphocytes and T-lymphocytes

Thrombopoiesis

platelet production

Megakaryoblast

produced from myeloid stem cell

- Forms megakaryocyte under influence of thrombopoietin

- Large size and multilobed nucleus

megakaryocyte

produces thousands of platelets

- Large cell produces proplatelets—long extensions

- These extend through blood vessel wall into bloodstream

- Blood flow "slices" off fragments which are platelets

Formed elements are

RBCs, WBCs, and platelets

Only WBCs are

complete cells

-RBCs have no nuclei or other organelles

-Platelets are cell fragments

Most formed elements survive

in bloodstream only few days

- WBCs and platelets - a few days

- RBCs survive for 120 days

Most blood cells originate in bone marrow and do not divide

RBC Erythrocytes

contribute to gastransport

RBC cell

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

RBC filled with

hemoglobin (Hb) for gas transport (>250 million Hb molecules)

RBC diameters

are larger than some capillaries, but flexibility to change shape

RBC Biconcave shape offers

huge surface area relative to volume for gas exchange

Hemoglobin makes up

97% of cell volume (not counting water)

RBCs have no

mitochondria

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

RBCs are dedicated to

respiratory gas transport

Hemoglobin binds

reversibly with oxygen

Normal values of hemoglobin

Males: 13-18 g/100ml; Females: 12-16 g/100ml.

Hemoglobin consists of

red heme pigment bound to the protein globin

Globin is

composed of four polypeptide chains

- Two alpha and two beta chains = 4 O2 carried maximum

- A heme pigment is bonded to each globin chain

- Gives blood red color

Oxyhemoglobin

Each Hb molecule can transport four O2 (loads in lung)

Each RBC contains

250 million Hb molecules

Deoxyhemoglobin

if unloading O2 tissues

Carbaminohemoglobin

CO2 loading in tissues, 20% of CO2 in blood binds to Hb, producing

oxygen binds to

iron weakly

Rapid attachment in lungs and rapid detachment in body tissues

carbon dioxide binds to

globin protein (not iron) weakly

Attachment in body tissue and detachment in lungs

regulation and requirements of erythropoiesis

* Too few RBCs lead to tissue hypoxia

* Too many RBCs increase blood viscosity

* > 2 million RBCs are made per second

*Balance between RBC production and destruction depends on

- Hormonal controls

- Dietary requirements

Hormonal Control (Erythropoietin, EPO)

controls erythropoiesis

Hormone produced primarily in the kidneys (a little in liver)

Secretion is stimulated by a decrease in blood oxygen

Red marrow myeloid cells respond to EPO - make more RBC's

The erythrocytes increase blood's oxygen carrying capacity

The increase in blood oxygen inhibits EPO release

Testosterone stimulates EPO production in kidney

Therefore, males have higher erythrocyte count, higher hematocrit

Environmental factors such as altitude influence EPO levels

low oxygen levels at high altitude stimulate EPO

some athletes abuse artificial epo

Use of EPO increases hematocrit, which allows athlete to increase stamina and performance

Dangerous consequences of artificial EPO

EPO can increase hematocrit from45% up to even 65%, with dehydration concentrating blood even more

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

date and destruction of erythrocytes

Life span: 100-120 days

RBCs are anucleate, so cannot synthesize new proteins, or grow or divide

Old RBCs become fragile, and Hb begins to degenerate

Globins and membrane proteins are broken into amino acids

Used by body for protein synthesis

Iron from hemoglobin transported by transferrin protein to liver

Bound to storage proteins: ferritin, hemosiderin

Most is bound to ferritin and stored in liver and spleen

Transported to red bone marrow as needed for erythrocyte production

Heme group (without Fe2+ )

Converted within macrophages into green pigment, biliverdin

Eventually converted into yellowish pigment, bilirubin

Transported by albumin to liver

Becomes part of bile (used in digestive system)

Bilirubin converted to urobilinogen in small intestine

May continue thorough intestine, be converted by bacteria to stercobilin, and be expelled from body as brown pigment in feces

May be absorbed back into blood, converted to urobilin, and be excreted from kidneys as yellow

anemia

ow number of RBCs or low hemoglobin

• Abnormally low O2-carrying capacity too low to support normal metabolism

hemorrhagic anemia

• Rapid blood loss (example: severe wound)

• Treated by blood replacement

chronic hemorrhagic anemia

• Slight but persistent blood loss

• Example: hemorrhoids, bleeding ulcer

• Primary problem must be treated to stop blood loss

iron deficiency anemia

• Can be caused by hemorrhagic anemia, but also by low iron intake or impaired absorption

• RBCs produced = pale microcytes

• Cannot synthesize hemoglobin because there is a lack of iron• Treatment: iron supplements

pernicious anemia

• Autoimmune disease that destroys stomach mucosa that produces intrinsic factor (needed to absorb B12)

• B12 = helps RBCs divide

• Without B12 RBCs enlarge but cannot divide, resulting in macrocytes/megaloblasts

• Treatment: B12 injections, sublingual, or nasal gel

• Can also be caused by low dietary intake of B12

• Can be a problem for vegetarians

renal anemia

• Kidneys cannot produce enough EPO

• Often accompanies renal disease

• Treatment: synthetic EPO

aplastic anemia

• Destruction or inhibition of red bone marrow

• Can be caused by drugs, chemicals, radiation, or viruses - 50% of cases have unknown cause

• All formed element cell lines are affected

• Results in anemia as well as clotting and immunity defects

• Treatment: short-term with transfusions, long-term with transplanted stem cells

Anemia due to Excessive RBC Destruction

• Premature lysis of RBCs = hemolytic anemias

• Can be caused by:

• Incompatible transfusions or infections

• Hemoglobin abnormalities: usually genetic disorder resulting in abnormal globin

• Thalassemias

• Sickle-cell anemia

Thalassemias

• Typically found in people of Mediterranean ancestry

• One globin chain is absent or faulty

• RBCs are thin, delicate, and deficient in hemoglobin

• Many subtypes that range in severity from mild to extremely severe

• Very severe cases may require monthly blood transfusions

sickle cell anemia

• Hemoglobin S: mutated hemoglobin - only 1 amino acid wrong

• RBCs become crescent shaped when O2 levels are low(exercise)

• Misshaped RBCs rupture easily and block small vessels leads to organ failure

• Results in poor O2 delivery and pain

• Prevalent in people of the African malarial belt and their descendants - possible benefit: people with sickle cell do not contract malaria

Polycythemia

• Abnormal excess of RBCs; increases blood viscosity, causing sluggish blood flow

• Polycythemia vera: Bone marrow cancer leading to excess RBCs

• Hematocrit may go as high as 80%• Treatment: therapeutic phlebotomy

• Secondary polycythemia: caused by low O2 levels (example: high altitude) or increased EPO production

• Blood doping: athletes remove, store, and reinfuse RBCs before an event to increase O2 levels for stamina

Dietary requirements for erythropoiesis

Amino acids, lipids, and carbohydrates

Iron: available from diet

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

Free iron ions are toxic so iron is bound with proteins

Stored in cells as ferritin and hemosiderin Transported in blood bound to protein transferrin