Chapter 17 - Blood

What is blood?

What is blood?

Blood is a fluid connective tissue; contains cells surrounded by a liquid extracellular matrix (plasma)

Erythrocytes

Red blood cells; they make up ~45% of blood

Hematocrit

The percent of blood volume that is composed of red blood cells (normal is around 45%-50%)

How is blood composition measured?

After blood is drawn, a centrifuge separates the blood into three components based on density: RBCs, WBCs, and plasma

Buffy coat

White blood cells (leukocytes) and platelets; this makes up 1% of blood

Blood plasma

The pale yellow fluid portion of blood, contains water/proteins/solutes; this makes up 55% of blood

Proteins in blood plasma (3)

Albumin, globulins, fibrinogen

Albumins (protein)

Most abundant plasma protein, transports lipids/hormones and helps regulate osmotic pressure of the blood

Globulins (protein)

Plasma protein that form antibodies

Fibrinogen (protein)

Plasma protein that is converted to fibrin in the clotting process

What are the cellular components of blood?

Erythrocytes (Red Blood Cells), Leukocytes (White Blood Cells), and Thrombocytes (Platelets)

What are the three major functions of blood?

Transportation, regulation, protection

What does blood transport?

Blood transports oxygen, carbon dioxide, nutrients, hormones, heat, and waste products

How does blood regulate homeostasis?

1. pH regulation via buffers
2. Temperature regulation by absorbing/releasing heat
3. Maintains fluid balance via platelets

How does blood protect the body?

Blood protects against excessive blood loss by clotting, and uses white blood cells to protect against infections

How long do blood cells live?

Lymphocytes (T and B cells) are able to live for years; most other blood cells live for hours/days/weeks

How long do RBCs live?

120 days (4 months)

Where does the recycling of hemoglobin take place?

In the liver and spleen

Pluripotent stem cells

Stem cells located in red bone marrow; they give rise to all the different types of blood cells

Hematopoiesis

The process of blood cell formation; occurs in the red bone marrow

Hematopoietic cells

Also called hemocytoblasts (meaning "blood cell bud"); these stem cells differentiate into the 3 types of blood cells

What are colony-stimulating factors?

A type of glycoprotein that stimulates the differentiation of stem cells into specific white blood cells

What is unique about the structure of red blood cells?

RBCs are biconcave discs (allows increased surface area), and they do NOT have nuclei or mitochondria (allows for more space for hemoglobin)

Hemoglobin

A protein in red blood cells that contains 4 iron molecules (Fe) and carries oxygen

Heme group

Disks that contain an iron molecule in the middle; the disks are the sites of oxygen binding

How many hemoglobin molecules are in each RBC?

A single RBC contains 250 million Hb molecules

Spectrin

A protein in the plasma membrane of RBCs which allows it to change shape

Oxyhemoglobin

Hemoglobin loaded with oxygen, produces a bright red color

Deoxyhemoglobin

Hemoglobin without oxygen, produces a dark blue-ish/red color

Carbaminohemoglobin

Hemoglobin bound to carbon dioxide

How does hemoglobin regulate blood pressure?

Hemoglobin releases nitrous oxide (NO), which stimulates vasodilation --> improves blood flow, enhances oxygen delivery

Carbonic anhydrase

An enzyme present in erythrocytes that catalyzes the conversion of CO2 and H2O into carbonic acid (H2CO3)

Bilirubin

An orange/yellow pigment in bile that formed by the breakdown of hemoglobin during the recycling of RBCs

Jaundice

Symptoms: Yellowing of the skin and the whites of the eyes

Cause: Caused by an accumulation of bile pigment (bilirubin) in the blood

Hypoxia

Low oxygen in the blood

Erythropoiesis

The formation of red blood cells; occurs when a hormone (erythropoietin) is released in response hypoxia (low O2 in the tissues)

Reticulocytes

Immature red blood cells in bone marrow; they enter the circulation and mature in 1 to 2 days

What are possible consequences of increased hematocrit?

Increased RBCs in the blood causes it to become dehydrated and increases the risk clotting/stroke/heart failure

Anemia

Definition: A condition in which the blood does not contain enough oxygen to support all of the body's tissues

Symptoms: Fatigue, weakness, shortness of breath

Causes: Blood loss, not enough RBCs being produced, too many RBCs being destroyed

Sickle cell anemia

A type of genetic anemia caused by a mutation to the hemoglobin protein --> RBCs are misshapen --> they are unable to carry O2 properly

Iron-deficiency anemia

Inadequate iron supply --> hemoglobin cannot be created --> RBCs are small and pale without hemoglobin --> anemia

What is the main function of leukocytes?

Fighting infections and diseases

What is unique about the structure of leukocytes?

Leukocytes contain a nucleus and organelles, but they do not have hemoglobin

Granular leukocytes (contains granules)

Neutrophils, eosinophils, basophils

What are the "granules" in leukocytes?

Tiny sacs; they contain enzymes/compounds that are used to fight pathogens and reduce inflammation

Neutrophils

Structure: Nuclei has three or more lobes

Function: The most common WBC; fights bacterial infections by engulfing bacteria by phagocytosis

Eosinophils

Structure: Nuclei has two lobes, they stain orange/red

Function: A WBC that digests and destroys parasitic worms, they also play a role in allergy and immune response

Basophils

Structure: Nuclei is U or S shaped but is obstructed by HUGE purple/black granules

Function: A WBC that produces histamine --> causing inflammation during an immune response

Agranular leukocytes (contains NO granules)

Lymphocytes, monocytes

Lymphocytes

Structure: Has a large, dark purple nucleus that takes up most of the cell volume

Function: Two WBCs (B and T cells) make antibodies and fight off viral infections

Monocytes

Structure: U shaped nucleus, pale blue cytoplasm

Function: A large WBC that transform into macrophages to fight off viruses and chronic infections

Emigration (diapedesis)

During an invasion, white blood cells leave the bloodstream by squeezing through the arterial walls and collect at sites of invasion

What does white blood cell concentration tell us?

High WBC count indicates infection/inflammation, low WBC count can be caused by drugs (glucocorticoids and anticancer drugs)

Leukopenia

Abnormally low white blood cell count

Leukemias

Cancers of the blood, caused by the overproduction of abnormal WBCs

Infectious mononucleosis

Epstein-Barr virus aka mono aka the kissing disease --> causes an LARGE amount of BIG lymphocytes --> the disease was named mono bc they originally thought the giant lymphocytes were monocytes

(common in young adults bc we're all hoes)

Megakaryocyte

A HUGE cell in red bone marrow that splits apart produces platelets

Thrombopoietin (TPO)

A hormone that stimulates platelet formation

How long do platelets live?

5-9 days

Hemostasis

To stop or control bleeding

3 Steps of hemostasis

1. Vascular spasm
2. Platelet plug formation
3. Coagulation

Vascular spasm

Contraction of the smooth muscle in the wall of a damaged blood vessel to prevent blood loss

Platelet plug formation

When platelets are exposed to collagen after an injury to the blood vessel, platelets clump and form a temporary seal --> they release chemicals to call more platelets to the injury site

Coagulation

Blood clotting

Intrinsic pathway of coagulation

Activated by internal injury; clotting factors are present within the blood and are activated by exposed collagen fibers

Extrinsic pathway of coagulation

Activated by external injury; clotting factors are located outside the blood and are activated by exposure to tissue factor

Phase 1 of coagulation

Prothrombinase is activated by either intrinsic or extrinsic pathway

Phase 2 of coagulation

Prothrombin is converted into the active enzyme thrombin

Phase 3 of coagulation

Thrombin converts fibrinogen to fibrin --> fibrin strands trap RBCs in a jelly substance

What role does vitamin K play in blot clotting?

Vitamin K is needed for the creation of 4 clotting factors

How are blood clots destroyed?

Blood clots are dissolved by the enzyme plasmin

Fibrinolysis

Breakdown and removal of a clot by plasmin ("splitting of fibrin")

Thrombus

A blood clot that forms in an unbroken blood vessel; if the clot blocks blood circulation --> tissue death will occur

Embolus

A blood clot that breaks free and travels through the bloodstream

Embolism

When an embolus (a moving blood clot) lodges within a vessel and blocks the flow of blood

Anticoagulant drugs

Drugs that prevent the clotting of blood

Thrombocytopenia

Low platelet count --> causes spontaneous bleeding and increased bleeding after an injury

What role does calcium play in blood clotting?

Calcium minerals are needed for blood clotting

Blood groups (2)

ABO and Rh (positive or negative)

What are antigens?

Proteins present on the surface of RBCs that determine blood type

What are antibodies?

Proteins in blood plasma (globulins) that detect and attack antigen

Positive blood type

The presence of Rh/D antigen --> positive

Negative blood type

Absence of Rh/D antigen --> negative

Type A blood

A antigens, B antibodies

Type B blood

B antigens, A antibodies

Type AB blood

A and B antigens, no antibodies (universal recipient)

Type O blood

NO antigens, A and B antibodies (universal donor)

What happens when antibodies detect incompatible blood?

When antibodies detect an incompatible blood antigen, the RBCs will clump together (agglutination) and rupture (hemolysis)

Agglutination

The clumping of red blood cells; will result if blood types with different antigens are mixed

Rh incompatibility

Occurs when a woman who is Rh-negative becomes pregnant with a baby with Rh-positive blood --> the mother's antibodies will attack the baby's RBCs (because the mother's body views them as foreign objects)

Hemolysis

The destruction of red blood cells