The Human Body

Circulatory System

Functions

• Distribution of food, water, salt, enzymes, hormones, oxygen, and antibodies

• removal of wastes (carbon dioxide, nitrogen)

• MAINTAIN HOMEOSTASIS

MAKE UP OF SYSTEM

• Blood

• blood vessels - arteries, veins, capillaries

– arterioles- small branched arteries

– venules- small branched veins

• heart

Heart

• Located between lungs under sternum, slightly to left side

• cardiac muscle

• enclosed in a sac called the pericardium

Valves of Heart

• 2 sets

– atrioventricular set (AV): one way from atria to ventricle

– semilunar set (SL): tricuspid, located at openings of arteries; prevents back flow of blood when ventricles empty

• one way only

• maintains pressure in arteries

Phases of the Heart Beat

• 2 phases

– systole: ventricles contract and force blood into arteries

– diastole: ventricles relax and receive blood from atria

• sounds like lub-dup, lub-dup, ….

– Lub: heart begins systole; AV valves close

– Dup: heart begins diastole; SL valves close

Control of the Heart Beat

• Sinoatrial node (SA node): starts the heart beat by contracting the atria

– located in the right atria

• Atrioventricular node (AV node): causes the ventricles to contract

– located in the right atria also

• rate is controlled by nerves, but affected by smoking, drugs, alcohol, emotional state, etc.

BLOOD VESSELS

• ARTERIES

– thick walled

– 3 layers

• connective tissue, smooth muscle, endothelium

– ventricles contract - forces blood into arteries, and the arteries expand. The blood flows in spurts

– the pulses are felt at pulse points due to systolic pressure

BLOOD VESSELS CONT.

• Capillaries:

– tiny vessels only one blood cell thick

– thin walled

– gas exchange occurs through the walls

BLOOD VESSELS CONT.

• Veins:

– close to surface of skin

– tubes returning to the heart

– thin walled, less muscle

– larger internal diameter than arteries

– many contain valves to keep the blood going back to the heart

BLOOD FLOW

• HEART-ARTERIES-ARTERIOLES-CAPILLARIES-VENULES-VEINS-HEART

• SPECIFICALLY: You should be able to trace the flow of blood from one part of the heart back to the heart

Blood Pressure

• Systole/diastole

• pressure is different in different vessels

– high pressure in arteries close to heart

– low pressure in veins

• factors

– volume of blood (~4.5 liters)

– output of blood

– elasticity of arterties

• increase elasticity = less pressure

• increase age = decrease elasticity

– changing vessel diameter

Composition of Blood

• Blood

– liquid connective tissue

– carries oxygen to the body, carbon dioxide and nitrogen away from the cells

– 12 pints of blood = average total

– 9% of body weight

– contains: plasma, red corpuscles, white corpuscles, and platelets

• liquid: 55% (plasma)

• solid: 45% (cells and platelets)

Plasma

• 90% water

• light red colored

• contains

– fibrinogen: helps in clotting blood

– Serum albumin (A): regulates osmotic pressure between plasma and tissue

– Serum Globulins: includes antibodies

– digested foods: glucose, fatty acids, glycerol, amino acids

– minerals: salts important in clotting and teeth and bone maintenance

– nitrogenous waste: by products of metabolism

Red Corpuscles

• Also called red blood cells and erythrocytes

• formed in red marrow from flat bones

• very small, but numerous (4.8-5.4 million)

• contain hemoglobin

– pigment in corpuscle containing Fe which carries oxygen and carbon dioxide

• donut shaped

• no nuclei in mammals

White Corpuscles

• Also called white blood cells and leucocytes

• larger than red blood cells

• contain nuclei

• fewer in number (1-600)

• formed in red marrow, lymph nodes, tonsils, and the spleen

• go from blood to tissue in capillary walls

• invade foreign microorganisms by phagocytosis

Platelets

• Pieces of larger cells

• formed in bone marrow

• no nuclei

• small in size

• important in clotting

– release factors which produce an enzyme called prothrombinase which triggers the following reactions

• prothrombin => thrombin

• fibrinogen (soluble) => fibrin (insoluble)

Blood types

Rh factor in blood

• Rh factor: another protein found in blood

– 85% of people have it; 15% do not

– Rh+ = protein present; Rh- = protein absent

• Problems occur with mixing also

– usually with women in their 2nd pregnancy

• Rh- female + Rh+ male = child with Rh+

– during second pregnancy the mom will have Rh+ antibodies build up that would attack a Rh+ child