Download Circulatory System

Lecture 2

The cardiovascular
system includes
two circuits:
1. Pulmonary circuit

Circulates blood
through the
lungs
2. Systemic circuit

Circulates blood
to the tissues of
the body

The heart beats to circulate blood throughout
the body
 Blood
Pressure: the
pressure of blood
against the wall of the
blood vessel
 Blood
pressure
measured with a
SPHYGMOMANOMETER.
 SYSTOLIC
BLOOD PRESSURE: the
highest arterial pressure
reached during ejection of
blood from the heart.


DIASTOLIC BLOOD PRESSURE:
lowest arterial pressure, occurs
while ventricles relax.
Normal resting blood pressure
is 120 mm Hg over 80 mm Hg
in brachial artery of arm
(120/80)


Because there are many more capillaries than
arterioles, blood moves very slowly.
This allows for substance exchange between
the blood and surrounding tissues.
Arteries
Arterioles
Capillaries Veinules
Veins
Blood velocity is inverse to the total cross-sectional
area of blood vessels! (As area up, vel down)

In the capillary beds, fluid is exchanged between the blood
and tissue.

Three forces control movement of fluid and other substances:
a.
Osmotic pressure (due to relatively low water
concentration of blood) tends to cause water to move
from tissue fluid to blood.
b.
Blood pressure (due to heart) tends to cause water to
move from blood to tissue fluid.
c.
Diffusion (due to concentration gradients) allows
materials to cross capillary walls

At the arteriole end of the capillary:
 blood
pressure (40 mm Hg) is greater than osmotic
pressure (25 mm Hg)
 filtration
occurs: water, small molecules (amino
acids, glucose, oxygen) are forced out, while blood
cells and plasma proteins remain inside vessels
 tissue
fluid (plasma without plasma proteins) is
formed
BP
and OP are about equal
molecules
follow their diffusion gradients as
diffusion occurs
concentration
of O2 and nutrients (amino acids,
glucose) is always greater in the blood, so they
diffuse out into tissue
concentration
of CO2, H2O and wastes are
greater in tissues, so they diffuse into the blood
BP
(10 mm HG) is less than OP (25 mm HG)
water
not
moves back into blood
all water moves into the blood
excess
fluid is taken up by the LYMPHATIC
CAPILLARIES and becomes LYMPH
lymph
is eventually returned to the blood
Waste
waste
molecules
molecules
CO
CO2
WATER
Water
amino acids
Amino acids
WATER
Water
O
O22
GLUCOSE
Glucose
2


Blood pressure in veins
in minimal
Instead of blood
pressure, venous return
depends on:
1. Skeletal muscle
contractions
2. Valves in the veins
3. Respiratory movement

When the skeletal muscles contract, they
compress the weak walls of the veins and
pushes the blood through the valves.

Once blood is forced past the valves in the
veins, it cannot flow backwards.


When a person inhales, the
thoracic pressure falls and
abdominal pressure rises.
This helps blood flow back
to the heart because blood
flows in the direction of
reduced pressure.
is a liquid connective
tissue which has different
types of cells suspended in
fluid.
 Blood
1.
2.
3.
4.
Maintaining homeostasis.
For transport (of gases,
hormones, wastes, nutrients)
Clotting (seal injuries)
Fight infections.
If allowed to sit in a test tube without
clotting, blood will divide into TWO MAIN
PARTS:
A. PLASMA
(liquid portion – 55% of blood)
B. FORMED ELEMENTS
(solid portion – 45%)


Yellowish fluid
Contains water and dissolved organic
and inorganic substances (proteins,
gases, salts, nutrients, wastes)
The composition of mammalian plasma
Plasma 55%
Constituent
Water
Major functions
Solvent for
carrying other
substances
Icons (blood electrolytes
Sodium
Potassium
Calcium
Magnesium
Chloride
Bicarbonate
Osmotic balance
pH buffering, and
regulation of
membrane
permeability
Separated
blood
elements
Plasma proteins
Albumin
Osmotic balance,
pH buffering
Fibringen
Clotting
Immunoglobulins
(antibodies)
Defense
Substances transported by blood
Nutrients (such as glucose, fatty acids, vitamins)
Waste products of metabolism
Respiratory gases (O2 and CO2)
Hormones
Figure 42.15
Consists of:
a. RED BLOOD CELLS (ERYTHROCYTES)
- over 95% of formed elements
- transports O2
- formed in bone marrow
b. WHITE BLOOD CELLS (LEUKOCYTES)
- fight infection
- formed in bone marrow & lymphoid tissue
c. PLATELETS (THROMBOCYTES)
- function in blood clotting.