Circulatory System

Circulatory System

• Overview– Every cell in a living organism

must have direct access to its nutrient supply• Single celled organisms

– rely on simple diffusion to move materials into the cell

• Multi-cellular organisms – require some type of system

Circulatory System

• Functions– Carries nutrients and wastes to

and from cells– Carries chemical messages

between different cells– Distributes heat throughout the

body–Maintains fluid levels in the body– Defends against invading

organisms

Circulatory System – Key Parts

1. Blood– 55% Plasma– 45% Formed

Elements• Cells

– white blood cells

– red blood cells

• Platelets– (<1%) cell

fragments

– Humans have ~5L of blood

2. Vessels– Arteries, veins

and capillaries

3. Heart

4. Periphery Organs– Kidneys– Liver– Intestines– Lungs

Blood

• Fig 12.10• Blood composition

Blood - Plasma

• Fluid portion of the blood

• Contains dissolved materials – gases, glucose, amino acids, ions

and vitamins. – wastes and hormones.

Blood – Plasma cont’d• Soluble proteins

– Albumins• along with minerals, maintain fluid levels by

osmotically drawing water back into the capillaries

– Immunoglobulins • antibodies and carrier/transport proteins

– Fibrinogens • aid in blood clotting

• Concentration of plasma proteins helps control the osmotic balance in the blood.– Stops excess water from exiting the blood

• Why malnutrition can cause swelling

Blood - Erythrocytes

• Red blood cells (RBCs)– 4-6 million per mm3 of whole blood

• Function to transport gas around the body

Blood - Erythrocytes

• Structure– biconcave disks,• increased surface area, Increases

ability to exchange gas

– Have no nucleus at maturity• Increased space for hemoglobin,

increases ability to carry oxygen

– proteins in cell membranes determine blood type

Blood – Erythrocytes cont’d

• Continuously produced in bone marrow–Mainly in large bones• the skull, ribs, vertebrae, and ends of

the long bones.

– Production of red blood cells is stimulated by erythropoietin• From kidney• In response to decreased oxygen in

blood

Blood – Erythrocytes cont’d

• Contain hemoglobin– Red iron containing pigment–Heme portion of molecule forms

an unstable, reversible bond with oxygen. • Carries 20 ml oxygen per 100 ml of

blood• Oxygenated state = oxyhemoglobin

– Bright red

• Reduced state = deoxyhemoglobin – purple-blue.

Blood – Erythrocytes cont’d

• Fig. 12.11• Structure of Hemoglobin

Blood – Erythrocytes cont’d

• Lifespan- 120 days• Destroyed in liver by fixed

macrophages– Hemoglobin is broken down • Iron is recycled-taken to bone marrow• Heme portion is degraded and

excreted as bile pigments

Blood – Erythrocytes cont’d

• Anemia- decreased red blood cells–Most common type comes from

iron deficiency

• Carbon monoxide poisoning– Carbon monoxide binds at heme

sites more strongly than oxygen

Blood - Leukocytes

• White blood cells (WBCs) – General term for a variety of cells

without hemoglobin– Less numerous than RBC’s- 4000-

11000 per mm3 of whole blood– Larger cells, nucleated

Blood – Leukocytes cont’d

• Important part of the immune system.– able to enter fluids surrounding

tissues to fight infection• Blood stream is only a means of

transport to location of infection.

Blood – Leukocytes cont’d

• Fight infection by destroying pathogens– Other leukocytes will also clean up

the mess!– Pus is composed of dead invaders

and leukocyte fragments

Macrophage engulfing bacteria

• Fig. 12.12

Blood – Leukocytes cont’d

• Granulocytes– have visible granules in cytoplasm• Neutrophils

– most abundant WBC, phagocytic

• Basophils– granules stain deep blue and release

histamine

• Eosinophils– granules stain red, phagocytize allergens

Blood – Leukocytes cont’d

• Agranulocytes– lack visible granules• Lymphocytes

– T and B cells, play roles in immunity

• Monocytes– largest WBC’s, phagocytic– Differentiate into macrophages and

dendritic cells

Blood – Leukocytes cont’d

• Lifespan– Different types live different

lengths of time– Some live only a few days-die

combating invading pathogens– Some live months or years

Blood – Leukocytes cont’d

• Change in numbers may indicate disease– Infectious mononucleosis• Epstein-Barr virus• Increased number of B lymphocytes

– AIDS• HIV – Human Immunodeficiency Virus• Decreased number of T lymphocytes

– Leukemia• Blood cancer• Uncontrolled numbers of WBC’s

Blood - Thrombocytes

• Platelets– fragmentation of large cells called

megakaryocytes – 150,000-300,000 per mm3 of whole

blood– Tiny cells that play important role

in blood clotting.

Blood – Thrombocytes cont’d

• Blood clotting– Platelets form a plug for immediate

stoppage of bleeding

– Vessels release prothrombin activator and injured tissues release thromboplastin • Thromboplastin stimulates further

release of prothrombin activator• This process requires calcium (Ca2+)

Blood – Thrombocytes cont’d

• Clotting cont’d– Prothrombin activator activates a

plasma protein prothrombin to thrombin

– Thrombin activates fibrinogen to fibrin which forms a clot

– Clot is composed of network of fibrin threads and trapped cells

Blood – Thrombocytes cont’d

• Clotting cont’d– As damage heals, plasmin breaks

down the clot• If blood is allowed to clot in a test

tube, serum develops– Serum-plasma without fibrinogen

Body fluids related to blood

• Table 12.1

12-28

Blood clotting

• Fig 12.13

Blood – Production

• Bone marrow stem cells– Cell which is capable of dividing

and differentiating into particular cell types• Red and white blood cells• Some may even be able to give rise to

liver, bone, fat, cartilage, heart, and nerve cells• May provide solutions for diseases

such as Alzheimer’s and Parkinson’s

12-29

Blood – Production cont’d

• Bone marrow stem cells cont’d–Many researchers prefer to work

with embryonic stem cells• Totipotent-can become any cell type• Ethical issues

12-30

Blood – Production cont’d

• Fig. 12.14

Blood Disorders

• Anemia– A deficiency in hemoglobin or red

blood cells• Decreases O2 delivery

• Causes low energy levels• Common causes are hemorrhages and

iron deficiency in the diet

– Hematocrit• Blood test that measures the

percentage of your blood volume that is erythrocytes

Blood Disorders

• Hemophilia– Genetic disorder which causes a

defect in the production of clotting factors

– blood clotting does not occur properly

– Excessive bleeding can result from a minor injury

Blood Disorders

• Sickle Cell Anemia– Genetic disorder which causes

erythrocytes to form an abnormal crescent shape

– shaped cells deliver less oxygen to the body's tissues

– Also break easily preventing healthy blood flow• Causes painful episodes