Transcript The Circulatory System

The Circulatory System
Human circulatory system


Closed system-blood moves through a
series of vessels
Consists of the heart, a series of blood
vessels, and the blood
Heart




Hollow organ, composed mostly of muscle,
the size of your clenched fist
Enclosed in protective covering called
pericardium
Heart walls have two layers of epithelial
and connective tissues that form around
the muscle called myocardium
Contractions of myocardium pump blood
through the system
Heart




Contracts 72 times per minute and pumps
70 ml of blood with each contraction
Septum divides the right side from the left
side and prevents mixing of oxygen-rich
and oxygen-poor blood
Upper chambers, atria (atrium), receive
blood
Lower chambers, ventricles, pump blood
away from the heart
Circulation through the body



Right side of heart pumps blood from heart
to lungs in pulmonary circulation to
exchange carbon dioxide and oxygen
Oxygen-rich blood returns to the left side of
the heart to be pumped to the body in
systemic circulation
Systemic circulation carries oxygen to all
cells and picks up carbon dioxide before
returning to the right side of the heart
Circulation through the heart





Blood enters heart through right and left atria
When heart contracts blood moves from atria to
ventricles (and out of ventricles to body or lungs)
Valves between atria and ventricles prevent blood
from flowing backwards
Valves also prevent blood from flowing back into
the ventricles when it leaves the heart
Valves keep blood moving in one direction and
increases pumping efficiency
Blood vessels

Blood moves through 3 types of vessels



Arteries
Capillaries
Veins
Arteries



Large vessels that carry blood from heart to
tissues
All carry oxygen-rich blood (except for the
pulmonary artery that carries oxygen-poor
blood from heart to lungs)
Blood leaving heart to go to body tissues
must first pass through the aorta (large
artery)
Capillaries



Smallest blood vessels
Walls only 1 cell thick
Bring oxygen and nutrients to tissues and
absorb carbon dioxide and other wastes
Veins




Return blood to heart after passing through
capillaries
Walls contain connective tissue and smooth
muscle
Large veins also contain valves to prevent
back flow
Many located between or within skeletal
muscles whose contractions help force
blood toward the heart
Arteries & Capillaries
To return to the chapter summary click escape or close this document.
Blood pressure



Produced when heart contracts and forces
a wave of fluid through the arteries
Force of blood on arterial walls is blood
pressure
Without pressure, blood would stop flow
Regulation of blood pressure



Sensory receptors in body detect level of blood
pressure and sends impulses to medulla
oblongata
If pressure is too high, neurotransmitters are
released by autonomic nervous sys. Causing
vessel walls to relax and lower pressure
If pressure is too low, neurotransmitters can
elevate pressure by causing vessel walls to
contract
Regulation of blood pressure



Kidneys also help control blood pressure
Hormones from heart and other organs
cause kidneys to remove water from blood
when pressure is too high
This reduces blood volume and lowers
blood pressure
Blood plasma






55% of blood is fluid called plasma
Plasma is 90% water and 10% dissolved gases,
salts, nutrients, enzymes, hormones, wastes, and
plasma proteins (albumins, globulins, fibrinogen)
Albumins and globulins transport fatty acids,
hormones, and vitamins
Albumins regulate osmotic pressure and blood
volume
Globulins fight viral and bacterial infections
Fibrinogens are proteins that help blood to clot
Red blood cells






Most numerous cells in blood (also called
erythrocytes)
Used to transport oxygen
Color comes from hemoglobin (iron-containing
protein that binds oxygen for transport)
Produced from red marrow
Do NOT have nuclei
Circulate for 120 days and are then destroyed by
the spleen
Blood Type Chart
To return to the chapter summary click escape or close this document.
White blood cells





Also called leukocytes
Do NOT have hemoglobin
Produced in bone marrow and have nuclei
Live for days, months, or years
Guard against infection, fight parasites, and
attack bacteria
Types of white blood cells


Phagocytes-engulf and digest bacteria and
other disease-causing microorganisms;
some release histamines that produce
redness and swelling (allergies)
Lymphocytes-produce antibodies (proteins)
that destroy pathogens; essential to fighting
infection and produce immunity to diseases
Importance of white blood cells


First lines of defense in fighting infection
Part of immune system
Platelets




Made of plasma proteins and cell fragments
Produced in bone marrow
Platelets come in contact with broken blood
vessel, they become “sticky” and gather at the
wound
Platelets release clotting factor (thromboplastin)
that converts prothrombin to thrombin (changes
fibrinogen to mesh of fibrin filaments) to stop
bleeding
Blood Components
To return to the chapter summary click escape or close this document.