The Human Circulatory Systemand the Components of Blood

Circulatory System

• The circulatory system is also referred to as the cardiovascular system

• Functions very closely with digestive and respiratory systems

• Basic system requires:1. a pump (heart); 2. vessels/pathways (veins, arteries, capillaries); 3. fluid (blood).

Circulatory System

Key Roles:• Maintains homeostasis– body temperature regulation– controls blood pressure

• Delivers and removes substances throughout body

Delivers Removes

- nutrients- oxygen- messages (via hormones)- toxins

- metabolic wastes- carbon dioxide- toxins

Components of Blood

• a sample of blood can be spun in a centrifuge– high speed, circular motion– causes blood to separate by the weights of its components

Components of Blood

Erythrocytes: Red Blood Cells

• Produced in bone marrow, stored in spleen• Constantly destroyed and replaced• Distinct biconcave shape

– Flattened disc that is pinched in the centre– Makes it flexible for traveling through various blood vessels

• No nucleus• No mitochondria• Contains special

hemoglobin molecule

Hemoglobin

• Complex protein made up of 4 protein chains, each with a central iron-containing heme group

• Iron gives RBCs their distinct red colour• Iron binds with oxygen

(4 O2 molecules per

hemoglobin molecule) – blood becomes oxygenated

• Iron is recycled in bone marrow

Anemia

• Medical condition when there is a less than normal amount of hemoglobin in the blood

• Less hemoglobin, less O2 being delivered throughout the body

• Can be caused by a genetic disorder (e.g., sickle cell anemia or thalassemias) or by a great loss of blood

Leucocytes: White Blood Cells

• Produced in bone marrow• Larger than red blood cells, but much fewer in

number• Amoeboid-shaped• Contain nucleus and lysosomes

Leucocytes: White Blood Cells

• Part of body’s immune response system• Detects and defends body from infection and

diseases• Lysosomes digest foreign bacteria• Pus is formed at site of infection– White blood cells (living & dead) + bacteria– Body’s natural “soap”

• An increase in WBCs indicate the body is fighting an infection

Leukemia

• Cancer of the white blood cells• White blood cells are produced in

overabundance in the bone marrow• Bone marrow becomes crowded and is unable

to manufacture other blood cells• Malignant WBCs can leave bone marrow,

travel blood stream and affect other organs

Platelets

• Fragments of special cells from the bone marrow

• Important for circulatory system repair• Form blood clots

Platelets – Blood Clotting

• Detect damaged blood vessels• Burst and release special adhesive chemicals• Platelets stick together and form

a platelet plug• Through chemical reactions,

forms strand-like fibrin molecule• A mesh of fibrin strands forms a

blood clot• Clot protects body from losing

blood through the damaged vessel• Holds vessel wound together until it can be

reconstructed with new tissue growth

Hemophilia

• X-linked genetic disorder• Individual lacks special proteins that are needed for

creating blood clots• Can bruise easily• Can bleed excessively if cut – sometimes bleeding to

death

Shock

• An actual medical condition – can be life-threatening• Body (or parts of body) shut down because circulatory

system cannot meet oxygen demands of some vital organs• Body reduces blood flow to arms and legs so it can

maximize O2 getting to the vital organs (in body’s core)• Can result from loss of blood, extreme fright or emotional

disturbanceFirst Aid:• Put person in half upright position, keep warm• Apply direct pressure to any areas of severe bleeding• Get (call for) medical help