CIRCULATORY SYSTEM

Circulatory System heart, blood, and blood vessels transport oxygen and nutrients

to organs and tissues throughout the body

carry away waste products

I. Functions Increases blood flow

meet increased energy demands during exercise

regulates body temperature conveys disease-fighting elements of

immune system to regions under attack white blood cells and antibodies

sends clotting cells and proteins to the affected site stop bleeding and promote healing

II.Circulatory System Components Heart - divided into four chambers

right atrium, right ventricle, left atrium, left ventricle

Chamber walls composed of myocardium contracts continuously and

rhythmically to pump blood.

Pumping action of the heart -two stages for each heart beat

Diastole-when the heart is at rest

Systole-when the heart contracts to pump deoxygenated blood toward the lungs and oxygenated blood to the body.

During each heartbeat, typically about 60 to 90 ml (about 2 to 3 oz) of blood are pumped out of the heart.

If the heart stops pumping, death usually occurs within four to five minutes.

Three types of blood cells oxygen-bearing red blood cells disease-fighting white blood cells blood-clotting platelets, all of which

are carried through blood vessels in plasma plasma is yellowish, consists of water, salts,

proteins, vitamins, minerals, hormones, dissolved gases, and fats.

Three types of blood vessels arteries carry blood away

thicker walls to withstand the pressure of blood being pumped from heart

veins - toward heart lower pressure one-way valves to prevent blood from flowing

backwards away from heart

capillaries tiny links b/w arteries and veins where oxygen

and nutrients diffuse to body tissues smallest of blood vessels, are only visible by

microscope ten capillaries lying side by side are barely as thick as a human hair.

Inner layer of blood vessels lined with endothelial cells - create

a smooth passage for blood transit surrounded by connective tissue

and smooth muscle for: Expansion - during exercise to meet demand

for blood and to cool body Contraction - after injury to reduce bleeding

and/or conserve body heat

If all the arteries, veins, and capillaries in the human body were placed end to end, the total length would equal more than 100,000 km (more than 60,000 mi)—they could stretch around the earth nearly two and a half times.

Arteries, veins, and capillaries - divided into two systems: Systemic - carries oxygenated blood from heart to

all tissues in body except lungs and returns deoxygenated blood carrying waste products, such as carbon dioxide, back to heart. oxygen-rich blood ejected under high pressure out of heart's main pumping chamber (L. ventricle) through largest artery (aorta) smaller arteries branch off from aorta to various parts of the body smaller arteries in turn branch out into even smaller arteries

(arterioles) arterioles become progressively smaller eventually forming

capillaries - blood pressure is greatly reduced

interstitial fluid fills the gaps between the cells of tissues or organs dissolved oxygen and nutrients then enter the cells from interstitial fluid

by diffusion carbon dioxide and other wastes leave the cell via interstitial fluid, cross

capillary walls, and enter blood. after delivering oxygen to tissues and absorbing wastes,

deoxygenated blood in capillaries then starts the return trip to heart

capillaries merge to form tiny veins, called venules

venules join together to form progressively larger veins

veins converge into two large veins: inferior vena cava-brings blood from the lower half of

body superior vena cava-brings blood from upper half Both join at the right atrium of heart

FYI Varicose Veins

pressure is dissipated in arterioles and capillaries blood in veins flows back to heart at very low

pressure, often running uphill when a person is standing

Flow against gravity allowed by one-way valves several centimeters apart in veins

Veins with defective valves (allow the blood to flow backward) become enlarged or dilated to form varicose veins

Varicose veins

Pulmonary Circulation deoxygenated blood returning from organs and tissues travel

from R. atrium to R. ventricle. pushed through pulmonary artery to lung pulmonary artery divides forming pulmonary capillary region microscopic vessels pass adjacent to alveoli (air sacs) - gases

are exchanged across thin membrane oxygen crosses membrane into blood while carbon dioxide

leaves blood through same membrane newly oxygenated blood then flows into pulmonary veins and is

collected by L. atrium of the heart (collecting pool for L.ventricle)

contraction of L. ventricle sends blood into aortacompleting circulatory loop

L. LUNGR. LUNG

HEART

AORTIC ARCH

SUP. VENA CAVA

INF. VENA CAVA AORTA

PUL. ARTERY

PUL. VEINS

On average, a single blood cell takes roughly 30 seconds to complete a full circuit through both the pulmonary and systemic circulation.

III. Additional Functions & Features Transports nutrients and removes toxins

Absorbed through intestine wall via network of capillaries and veins that drain the intestine - hepatic portal circulation (HPC)

HPC – carries nutrients/toxins to the liver for further metabolic processing.

Liver stores sugars, fats, and vitamins & releases to the blood as needed

Liver also cleans blood by removing waste product and toxins. After hepatic portal blood has crossed the liver cells veins converge to form the large hepatic vein that joins the vena cava near the right atrium.

Body Temperature

Regulation exercise = muscles

generate heat blood supplying muscles

with oxygen and nutrients absorbs much heat and carries to other parts of body

If body gets too warm, vessels near skin enlarge = disperse excess heat outward through skin

If cold, blood vessels constrict to retain heat.

Hormone Transportation Endocrine system = collection of hormone-

producing glands Regulates rate of metabolism, growth, sexual

development, and other functions. chemical messengers (hormones) released

directly into bloodstream transported to specific organs and tissues

WBC & Antibody Transport and Clotting WBC and antibodies circulate in blood transported to infection sites coagulation system - composed of

Platelets and clotting factors circulate in blood Damaged blood vessels are repaired by forming

clots

Supporting Organs Brain/nervous system

monitor blood circulation send signals to heart or blood vessels to maintain constant blood

pressure. Bone Marrow

Site of new blood cell manufacture Spleen

Old blood cells are broken down valuable constituents, such as iron, are recycled

Kidneys metabolic waste products removed from blood also screens for excess salt maintains blood pressure balance of minerals and fluids