Respiratory and
Circulatory
Systems
Bio 171 – Week 11
Learning Objectives
• Describe the mechanics of breathing
• Describe the path of blood flow in the fourchambered heart
• Describe the structure and function of red blood
cells, white blood cells, capillaries, veins, and
arteries
• Understand how the respiratory and circulatory
systems work together; their purpose and function
• Understand the importance of surface area:volume
ratios on respiration
Respiratory and Circulatory
Systems
• Cells need O2, get rid of
CO2—these tasks are
completed by respiratory and
circulatory systems.
• Respiratory—gas exchange
between the surface of
organism and the
environment
• Circulatory—connects all cells
with the environment
• During respiration gases
diffuse between environment
and organism
Lungs and Respiration
• Thoracic cavity
• Diaphragm contracts,
expands thoracic
cavity
• Expansion creates
negative pressure
(partial vacuum)
pulling air into nostrils,
mouth, and then
lungs
• Intercostal muscles
between ribs also
contract to expand
the chest and suck air
into lungs
Exercise: Exhalation occurs by relaxing your
diaphragm and intercostal muscles. To force
more air from your lungs, you must use our
abdominal muscles. Place your hand near your
belly button and force as much air out of your
lungs as possible.
What happened to your abdominal muscles
when you exhaled?
Respiratory Organs
• Gills—designed for
water breathing, dense
capillary beds that
function in external resp.
• Extracts dissolved oxygen
from water
• Thin membranes dry out if
not kept moist
Respiratory Organs
• Lungs—air breathing, elastic
bags w/in body (volume
expands/decreases),
connected to environment
via the trachea, paired
organ
Respiratory Organs
• Gas bladder —control buoyancy, sometimes
vascularized and function to respire
• Single, dorsal to digestive tract, no distinction between systemic and
pulmonary circulation
• Homologous to lungs
• Found in ray-finned fishes (class Actinopterygii) but not cartilaginous
fishes (class Chondrichthyes; e.g., sharks and rays)
Respiratory System
• Cutaneous—respiration
through skin, important for
amphibians
Respiration - Mammals
• In mammals lungs are
filled via aspiration
pump (ventilation):
o Air is sucked in by low
pressure created around
lungs; rib cage and
diaphragm
o Lungs expand, fill with air
• Air enters Trachea
• Trachea -> Bronchi ->
Bronchioles
• Bronchial tubes
terminate into thinwalled air sacs, called
alveoli, where gas
exchange occurs
Bronchial and Pulmonary
Diseases
• Pneumonia – Alveoli fill
with thick fluid, making
gas exchange difficult
• Emphysema – Alveoli
burst and fuse into
enlarged air spaces;
surface area for gas
exchange is reduced.
• Asthma – airways are
inflamed due to
irritation and
bronchioles constrict
due to muscle spasms.
• Bronchitis – Airways are
inflamed due to
infection or irritant.
Coughing brings up
mucus and pus.
Circulatory System
• Transports gases between sites of internal and
external respiration
• But also:
o Thermoregulation
o Carries glucose to active organs
o Carries hormones, immune system cells
• Cardiovascular system—includes blood, vessels,
and heart
Circulatory System
• Blood vessels
o Arteries—away from heart
o Veins—toward the heart
o Capillaries—tiny vessels connecting the
two
• Generally arteries carry O2
rich blood and veins O2 poor,
but not always
o Pulmonary artery carries O2 poor blood
from heart to lung, pulmonary vein
carries O2 rich from lungs to heart
• Two circuits: Pulmonary and
Systemic
Circulatory System
• Blood flows through arteries via pressure
from heart beats
• Veins have one-way valves, flow is
accomplished largely by muscle
contraction
• Mammals have a double circulation:
o Systemic: body
o Pulmonary: lungs
Circulatory System – The Heart
• Pump that moves blood through
vessels
• Mammals—four chambered heart
o No mixing of O2 rich and O2 poor blood
o Divided circ. allows for separate blood pressures
• Atria receive blood from veins
• Ventricles pump blood into
arteries
• Right atrium receives blood from
body, then to right ventricle, which
pumps blood to lungs
• Left atrium receives blood from the
lungs, then to left ventricle, which
pumps blood to body
Circulatory System – The Heart
• Blood passes through
atrioventricular valves to the
ventricles
o Tricuspid (R) and Bicuspid (L)valves
• Blood passes through semilunar
valves to leave the ventricles
o Pulmonary semilunar valve
o Aortic semilunar valve
• Right atrium receives blood from
body, passes through tricuspid
valve to right ventricle, which
pumps blood to lungs through the
pulmonary semilunar valve to lungs
• Left atrium receives blood from the
lungs, passes through bicuspid
valve to left ventricle, which pumps
blood through the aortic semilunar
valve to body
Circulatory System – The Heart
•
•
•
•
•
•
Superior/inferior venae cavae - Blood
from body to right atrium
Pulmonary Artery - Blood from R
Ventricle to Lungs
o
Oxygen-poor!
o
Oxygen-rich!
Pulmonary Veins - Blood from Lungs to L
Ventricle
Aorta - Blood from L Ventricle to body
Right atrium receives blood from body
through the superior or inferior vena
cava, passes through tricuspid valve to
right ventricle, which pumps blood to
lungs through the pulmonary semilunar
valve into the pulmonary artery to lungs
Left atrium receives blood from the lungs
through the pulmonary veins, passes
through bicuspid valve to left ventricle,
which pumps blood through the aortic
semilunar valve to the aorta and to the
rest of the body
Tracing Blood Through
the Body
Gas Exchange
• Occurs in capillaries
o One cell thick
• Occurs through
diffusion across a
concentration
gradient
o High  Low concentration of
O2
Today
• Respiratory and
Circulatory dissections
o Fetal Pig
o Sheep Hearts
• Do all pig dissections then
do hearts
• Pages 68-103!
• Surface Area and
Volume Handout
• Turn in both handouts
and graphs from the
SA:V handout!
Surface Area:Volume
Handout
• Estimate SA and
volume for a
bacterium, protistan,
red-backed
salamander, fetal pig,
human
• Calculate SA:V ratio
• Two graphs: V (x-axis)
x SA (y-axis) for each
species and log(V) x
log(SA)
• Choose preserved lizard,
plethodontid photo, or live
plethodontid to measure
Photos by Alex Figueroa
(http://afigs.weebly.com/)
Family Plethadontidae:
Lungless Salamanders
• Lack lungs; respire through skin
and tissue in mouth
• Have 3-chambered heart: 2
atria, 1 ventricle
• 439 species, originated in the
Appalachian Mountains (US!)
• Appalachian region has the
highest biodiversity of
salamanders in the world
• ~10 species in New York State
• Plethodon cinereus – Redbacked Salamander
• Polymorphic – “red-backed”
and “lead backed” colors
• Find on Staten Island! Check
under logs in deciduous forests
Photos by Alex Figueroa
(http://afigs.weebly.com/)