CIRCULATORY SYSTEM

Circulatory System

Circulatory system: • Efficient distribution system

• Network of 100,000 km of blood vessels•Supplies cells with nutrients and oxygen and removes carbon dioxide and waste products

• Transports hormones

•Plays an important role repairing tissues and protecting the body from infection

Organs of the Circulatory System* Blood: Type of connective tissue (cells &

liquid)* Heart: Multi-chambered, muscular organ- Overall flow of blood via blood vessels

from the heart to the tissues throughout the body back to the heart- Body contains 5 L of blood

3 Types of Blood Vessels1. Capillaries:

• Microscopic blood vessels- make contact with all cells of the body

• Walls of capillaries consist of a thin layer of epithelial tissue enables diffusion of nutrients and oxygen out of the blood & the diffusion of waste products into the blood

2. Arteries: • Blood flows from the heart to the capillaries through thick

walled blood vessels = arteries• Walls of arteries = epithelial tissue wrapped in layers of

smooth muscle and connective tissue• Muscle tissue enables arteries to constrict & dilate; Blood

in arteries is under pressure due to the heart’s pumping action

3 Types of Blood Vessels3. Veins: Blood returns from the capillaries to the heart through

vessels = veins Walls of veins consist of epithelial tissue surrounded by

smooth muscle & connective tissue… but muscle layer is thinner than that in arteries

Blood is under little pressure Contracting skeletal muscles squeezes the

veins and forces blood back to the heart

Chemical Exchange between Blood & Body Tissues

Most cells are no further than 10 micrometers from a capillary and the blood inside

Capillary networkCritical to accomplishing the main functions of

the circulatory systemDistribution of oxygen & nutrients, and removal of waste

products

Cells in body tissues surrounded by interstitial fluid

Chemical Exchange between Blood & Body Tissues

Substances in capillaries do not enter tissue cells directly

1. First: Substances in capillaries enter the interstitial fluid

2. Second: Substances in the interstitial fluid then enter the cells

Chemical Exchange between Blood & Body Tissues

• Exchange of substances between blood & interstitial fluid occurs in several ways:

• Small molecules (oxygen, carbon dioxide) diffuse across the membrane or pass through gaps between the epithelial cells of the capillary wall• Oxygen & nutrients move from the blood into the

interstitial fluid• Carbon dioxide & other small waste products move from

the interstitial fluid into the blood• Larger molecules move across the membranes by

exocytosis and endocytosis

Chemical Exchange between Blood & Body Tissues

• Exchange of substances between blood & interstitial fluid occurs in several ways:• Blood pressure forces fluid through the capillary wall

At the artery end of a capillary blood pressure forces water, small solutes, and some dissolved proteins through the gaps between the cells… However, blood cells & larger proteins are too large to pass easily through the openings remain in the capillary Result: Vein end of the capillary in hypertonic

compared to the surrounding interstitial fluid Thus, water reenters the vein end of the capillary via osmosis… Blood pressure is very low at the vein end of the capillary, so it does not oppose the flow of fluid back into the capillary

Blood consists of Cells suspended in Plasma * Blood

Highly specialized tissuePart liquid, part cellular material

* PlasmaComposes 55% of the volume of bloodPlasma = 90% water; Other 10% = dissolved

salts, proteins, transport substances

Blood consists of Cells suspended in Plasma * Red blood cells (Erythrocytes):

Constitutes the remaining 45% of the blood volume

Carry oxygen from the lungs to all the tissues in your body

Each RBC contains 250 million molecules of hemoglobin (Protein that temporarily stores oxygen for delivery to cells)

Hemoglobin Contains iron Oxygen molecules bind to the iron portion (heme group) of the hemoglobin molecule

Red Blood Cells* Red blood cells (Erythrocytes):

Produced in the bone marrow Distinctive shape due to the loss of their

nuclei and mitochondria shape = flat disk, curves inward in the middle structure provides increased surface area for oxygen transport

Life span of a RBC = 100-120 days

Blood consists of Cells suspended in Plasma * White blood cells (Leukocytes):

Responsible for fighting infection and preventing the growth of cancer

When an infection invades your body # of WBCs increases

Most of the action of the WBC takes place outside the blood vessels in the interstitial fluid

3 Functions of Blood

Blood:Carries oxygen, nutrients, and hormonesRemoves waste (carbon dioxide)Fights infection

Blood consists of cells suspended in plasma

Blood:Connective tissueFlows through blood vesselsFive liters of blood

Takes 1 minute to make a complete circuitComposed of:

55% Plasma45% RBCs

Blood consists of cells suspended in plasmaPlasma (45%)

90% water10% dissolved salts, proteins, and other

substancesRBCs

ErythrocytesMost numerous cells in blood5 million RBCs in 1 drop of bloodContains hemoglobinProduced in the bone marrow (2 million per

second)Replaced every 120 days

Blood consists of cells suspended in plasma

HemoglobinProtein that binds with oxygen for transport

to cellsContains iron which contains a high affinity

for oxygen

Blood consists of cells suspended in plasma

WBCsLeukocytesFight infection and prevents growth of cancer4,000-11,000 WBCs in 1 drop of bloodInfection increases the number of WBCsMost action takes place in the interstitial fluid

Blood consists of cells suspended in plasma

Blood clotting:Platelets help with blood clottingOriginate from the bone marrow250,000 – 500,000 in a drop of bloodStick to damaged siteRelease clotting factorsFibrin produced (Protein)Patch forms and dries into a scab