Cardiovascular System:Blood

Chapter 14

Cardiovascular System

• 3 components– Blood, heart, and

blood vessels

• Transports substances to and from body cells

• Hematology: branch of science concerned w/study of blood, blood-forming tissues

Blood• The only liquid connective

tissues with three functions• 1. Transportation

– Blood transports oxygen from lungs to cells throughout body

– Carries nutrients from GI tract to body cells, waste products away from cells, hormones from endocrine glands to other body cells

• 2. Regulation– pH of body fluids

• 3. Protection– Blood clots in response to

injury, which protects against excessive blood loss

– Helps protect against disease • Ex. White blood cells

Blood

• Denser and more viscous (sticky) than water

• pH ranges from 7.35-7.45• 8% of total body weight• Hematocrit: the

percentage of total blood volume occupied by red blood cells

• 2 parts– 1. blood plasma– 2. formed elements

Blood Plasma• Liquid that contains

dissolved substances• Contains plasma proteins

– Albumins: help maintain proper blood osmotic pressure, important in exchange of fluids across capillary walls

– Globulins: defensive proteins

• Antibodies or immunoglobulins

– Fibrinogen• Key protein in formation of

blood clots

Formed Elements

• Cells and cell fragments

• Red blood cells• White blood cells• Platelets

Formation of Blood Cells

• Hemopoiesis: the process by which the formed elements of blood develop

• Before birth: occurs in the yolk sac of embryo and later in liver, spleen, thymus, and lymph nodes of fetus

• 3rd trimester: red bone marrow becomes site for hemopoiesis

• Red Bone Marrow: highly vascularized connective tissue located in the microscopic spaces b/w trabeculae of spongy bone tissue

• Red bone marrow cells come from pluripotent stem cells (have capacity to develop into many different types of cells)– Generate myeloid stem cells (develop. in red bone marrow and

develop into diff. kinds of cells) and lymphoid stem cells (begin develop. in red bone marrow but complete in lymphatic tissue)

Red Blood Cells

• (RBCs) or erythrocytes

• Protein called hemoglobin: carries oxygen and gives its red color

• Mature RBCs are without a nucleus or organelles, cannot divide or do extensive metabolic activities

RBC life cycle• Live for 120 days• 1. Macrophages in spleen, liver, and red bone marrow phagocytize

ruptured and worn-out red blood cells, break apart globin and heme of hemoglobin

• 2. globin amino acids which can be used by body to create proteins

• 3. iron removed from heme and associates with transferrin (acts as transporter)

• 4. iron-transferrin complex red bone marrow, RBC precursors use it in hemoglobin synthesis– Iron needed for heme– Amino acids for globin– Vitamin B12 needed for hemoglobin

(stomach produces intrinsic factor for absorption of B12

• 5. Erythropoiesis in red bone marrow RBCs, enter circulation

• 6. When iron removed from heme:– Biliverdin: a green pigment Bilirubin: a yellow-orange

pigment– Bilirubin enters blood liversecreted by liver cells into

bilepasses into small intestine and large intestine• 7. large intestine, bacteria convert bilirubin urobilinogensome absorbed into blood urobilinexcreted in urine

• Most urobilinogen eliminated in feces – Brown pigment stercobilin

RBC Production

• Formation of just RBCs is called erythropoeisis• Near end of process: RBC precursor ejects nucleus reticulocyte (biconcave shape of red blood cell)

• Negative feedback loop• Regulated by amount of oxygen in blood• Erythropoiesis and destruction of RBCs at same pace• If erythrop. can’t keep up with RBC destruction, erythro.

increases

RBC Production• Hypoxia: deficiency of

oxygenstimulates release of erythropoietin (EPO) which is hormone made by kidneys

• EPOthru bloodred bone marrowstimulates erythropoeisis

• Cyanosis: bluish-purple skin coloration due to prolonged hypoxia

• Anemia: low # of RBCs or low hemoglobin

White Blood Cells

• WBCs or leukocytes• Have nuclei, no

hemoglobin• Granular or agranular• Granular: neutrophils,

eosinophils, and basophils

• Agranular: lymphocytes and monocytes

WBC functions

• Combat microbes by phagocytosis or produce antibodies

• Neutrophils: respond first, phagocytosis, release enzymes such as lysozyme

• Then monocytes arrive– wandering

macrophages– Clean up cellular

debris

• Eosinphils release enzymes that combat inflammation in allergic reactions

• Basophils involved in allergic reactions

• Lymphocytes-3 types– B cells-produce antibodies– T cells-attack viruses,

fungi, transplanted cells, cancer, etc.

– Natural killer cells -attack variety microbes and certain tumor cells

WBCs

• Have proteins called major histocompatibility antigens (MHC)

• “cell identity markers”• Used to type tissues to identify

compatibility of donors and recipients

WBC life spans

• A few days• During infection, only a few hours• Leukocytosis: increase in the # of WBCs

– Usually indicates inflammation/infection

Platelets

• Disc shaped• No nucleus• When blood vessels

damaged , platelets form blood clots

• Release chemicals that promote blood clotting

• Life span: 5-9 days

• Hemostasis: a sequence of responses that stops bleeding when blood vessels are injured

• Hemorrhage: the loss of a large amount of blood from the vessels

• Hemostatic response must be quick, localized, and carefully controlled

• Three mechanisms:– 1. vascular spasm– 2. platelet plug formation– 3. blood clotting (coagulation)

1. Vascular Spasm

• smooth muscle contracts quickly causing a spasm

• Reduces blood loss• vasoconstriction

which further reduces blood loss

2. Platelet Plug Formation• Platelets come together

to form a platelet plug• 1. platelet adhesion• 2. b/c of adhesion,

platelets change and enter the platelet release reaction – sustain vascular spasm

• 3. chemical release makes other platelets sticky platelet aggregation forming a platelet plug

3. Clotting (Coagulation)• Liquid part of blood:

serum • Gel portion: clot

– fibrin• Clotting (coagulation): is

a series of chemical reactions that culminates in the formation of fibrin threads

• If blood clots to easily thrombosis can occur (clotting in an unbroken blood vessel)

Clotting

• With the use of clotting factors• 3 stages:

– 1. Prothrombinase is formed– 2. Prothrombinase converts prothrombin

(liver) enzyme thrombin– 3. Thrombin converts soluble fibrinogen

(liver) insoluble fibrin. Fibrin forms threads of clot.

Two pathways for clotting

• 1. Extrinsic Pathway– Occurs rapidly– Damaged tissue cells release tissue factor (TF) into

blood from OUTSIDE blood vessels– Tissue eventually converted into prothrombinase

• 2. Intrinsic Pathway– Occurs more slowly– Activators in direct contact with blood or within blood

Clot Retraction

• Clot retraction: consolidation or tightening of the fibrin clot

• plasminogen– This can be activated to plasmin clot is dissolved by digesting fibrin threads

• Small clots dissolve in a process called fibrinolysis

Clotting

• Clots can form within blood vessels– Roughened vessel surface as a result of atherosclerosis,

trauma, or infection

• Thrombosis: clotting in an unbroken blood vessel• Thrombus embolus

• Emboli form in veins b/c slower blood rate

• Pulmonary embolism: when embolus gets lodged in lungs– Ventricular failure or death– Blocking arteryblocks

blood flow to brain, kidney, or heart stroke, kidney failure, or heart attack

Blood Groups and Blood Types

• Isoantigens (agglutinogens): an assortment of glycolipids and glycoproteins on the surface of red blood cells

• blood groups and within a blood group there may be different blood types– 2 major blood groups

• ABO and Rh

ABO blood group• Based on 2 isoantigens

– Antigens A and B– Type A (A antigen) and Type B

(B antigen) blood, Type AB or O (no antigens)

• Isoantibodies (agglutinins)– React with A and B antigens if

mixed– Anti-A antibody (reacts with

antigen A)– Anti-B antibody (reacts with

antigen B)– So, If you have type A blood,

you have A antigens on RBC surfaces, and anti-B antibodies in your plasma

Rh Blood Group

• Rh+ or Rh-• Important in blood transfusions• Ex. Person with type A blood receives type

B blood– 1. The anti-B antibodies of recipient bind to B

antigens of donor blood causing hemolysis– 2. anti-A antibodies of donor plasma can bind

to A antigens on recipients RBC, not serious though

• People with type AB blood = “universal recipients’”

• Type O blood= “universal donors”

Common Disorders

• Anemia: oxygen carrying capacity of blood is reduced due to decreased RBCs or amount of hemoglobin

• Sickle Cell Disease: has abnormal type of hemoglobin (Hbs). When this gives up oxygen, bend the erythrocyte into a sickle shape

• Hemophilia: inability to produce blood clots • Leukemia