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The Circulatory and
Respiratory Systems
Chapter 49
Invertebrate Circulatory Systems
Sponges, Cnidarians, and nematodes lack a
separate circulatory system
-Sponges circulate water using many incurrent
pores and one excurrent pore
-Hydra circulates water through a gastrovascular
cavity (also for digestion)
-Nematodes are thin enough that the digestive
tract can also be used as a circulatory system
2
Invertebrate Circulatory Systems
Larger animals require a separate circulatory
system for nutrient and waste transport
-Open circulatory system = No distinction
between circulating and extracellular fluid
-Fluid called hemolymph
-Closed circulatory system = Distinct
circulatory fluid enclosed in blood vessels &
3
transported away from and back to the heart
Vertebrate Circulatory Systems
Mammals, birds and crocodilians have a
four-chambered heart with two separate
atria and two separate ventricles
-Right atrium receives deoxygenated
blood from the body and delivers it to the
right ventricle, which pumps it to the lungs
-Left atrium receives oxygenated blood
from the lungs and delivers it to the left
ventricle, which pumps it to rest of the body
4
Later-Evolved Vertebrate Circulatory Systems
-Oxygenated and deoxygenated blood don’t mix in heart5
Heart Valves
The heart has two pairs of valves:
-Atrioventricular (AV) valves guard the openings
between atria and ventricles
-Tricuspid valve = On the right
-Bicuspid, or mitral, valve = On the left
-Semilunar valves guard the exits from the
ventricles to the arterial system
-Pulmonary valve = On the right
-Aortic valve = On the left
6
The Cardiac Cycle
These valves open and close as the heart
goes through the cardiac cycle of rest
(diastole) and contraction (systole)
-“Lub-dub” sounds heard with stethoscope
-Systolic pressure is the peak pressure at which
ventricles are contracting AV valves close (to prevent
backwash)= “lub”
-Diastolic pressure is the minimum pressure
between heartbeats at which the ventricles are
relaxed, semilunar valves close = (to prevent
backwash)“dub”
-Blood pressure is written as a ratio of systolic over
7
diastolic pressure
8
Contraction of Heart Muscle
Autorhythmic SA node
Initiates
depolarization
Electrocardiogram (ECG or EKG)
9
Characteristics of Blood Vessels
*Arteries and veins are composed of four tissue layers
*Capillaries are composed of only a single layer of
endothelial cells...They allow for rapid exchange of
gases and metabolites between blood and body cells
10
Arteries and Arterioles Regulate Heat Loss
11
Cardiovascular Diseases
Atherosclerosis
-Accumulation of fatty material within arteries
Arteriosclerosis
-Arterial hardening due to calcium deposition
12
Blood Flow and Blood Pressure
Blood flow and pressure are regulated by the
autonomic nervous system
The cardiac center of the medulla oblongata
modulates heart rate
-Norepinephrine, from sympathetic
neurons, increases heart rate
-Acetylcholine, from parasympathetic
neurons, decreases heart rate
13
Blood Flow and Blood Pressure
Cardiac output is the volume of blood
pumped by each ventricle per minute
-Increases during exertion because of an
increase in both heart rate & stroke volume
Arterial blood pressure (BP) depends on the
cardiac output (CO) and the resistance (R)
to blood flow in the vascular system
BP = CO x R
14
Blood Flow and Blood Pressure
The baroreceptor reflex is a negative
feedback loop that responds to BP changes
-Baroreceptors detect changes in arterial
BP
-If BP decreases, the number of
impulses to cardiac center is decreased
-Ultimately resulting in BP increase
...and vice versa.
15
Veins and Venules
Veins and venules
-Have thinner layer of
smooth muscles than
arteries
-Return blood to the
heart with the help of
skeletal muscle
contractions and oneway venous valves
16
What is Blood?
A connective tissue
composed of a fluid
extracellular matrix,
called plasma, within
which are found different
cells and formed
elements
The functions of circulating blood are:
1. Transportation of materials
2. Regulation of body functions
3. Protection from injury and invasion
17
The Components of Blood
Plasma is 92% water, but it also contains the
following solutes:
-Nutrients, wastes, and hormones
-Ions
-Proteins
-Albumin, alpha (a) & beta (b) globulins
-Fibrinogen
-If removed, plasma is called serum
18
The Components of Blood
The formed elements of the blood include red
blood cells, white blood cells and platelets
Red blood cells (erythrocytes)
-About 5 million per microliter of blood
-Hematocrit is the fraction of the total blood
volume occupied by red blood cells
-RBCs of vertebrates contain hemoglobin, a
pigment that binds and transports oxygen
19
White Blood Cells
White blood cells (leukocytes)
-Less than 1% of blood cells
-Larger than erythrocytes and have nuclei
-Can also migrate out of capillaries
-Granular leukocytes
-Neutrophils, eosinophils, and basophils
-Agranular leukocytes
-Monocytes and lymphocytes
20
The Components of Blood
Platelets are cell fragments that pinch off
from larger cells in the bone marrow
-Function in the formation of blood clots
Prothrombin
Thrombin
Fibrinogen
Thrombin
Fibrin
1. Vessel is
damaged,
exposing
surrounding
tissue to blood.
2. Platelets
adhere and
become
sticky, forming
a plug.
3. Cascade of
enzymatic
reactions is
triggered by
platelets,
plasma factors,
and damaged
tissue.
4. Threads of
fibrin trap
erythrocytes
and form
a clot.
5. Once tissue
damage
is healed,
21
the clot is
dissolved.
Making Blood “Formed Elements”
All of the “formed elements”
develop from pluripotent
stem cells
Hematopoiesis is blood
cell production
-Occurs in the bone
marrow of (medullary bone),
and produces:
-Lymphoid stem cell...Lymphocytes
-Myeloid stem cell...All other blood cells
Red blood cell production
is called erythropoiesis
22
Lungs
Gills were replaced in terrestrial animals because
1. Air is less supportive than water
2. Water evaporates
The lung minimizes
evaporation by moving
air through a branched
tubular passage
23
Gas Exchange
Gases diffuse directly into unicellular organisms
However, most multicellular animals require
system adaptations to enhance gas exchange
-Amphibians respire across their skin
-Echinoderms have protruding papulae
-Insects have an extensive tracheal system
-Fish use gills
-Mammals have a large network of alveoli
24
Gills
Gills are specialized extensions of tissue that
project into water
External gills are not enclosed within body
structures
-Found in immature fish and amphibians
-Two main disadvantages
-Must be constantly moved to ensure
contact with oxygen-rich fresh water
-Are easily damaged
25
Gills
The gills of bony fishes are located between
the oral (buccal or mouth) cavity and the
opercular cavities
-These two sets of cavities function as
pumps that alternately expand
-Moving water into the mouth, through
the gills, and out of the fish through the
open operculum or gill cover
26
Gills
27
Gills
There are four gill arches on each side of a
fish’s head
-Each is composed of two rows of gill
filaments, which consist of lamellae
-Within each lamella, blood flows
opposite to direction of water movement
-Countercurrent flow
-Maximizes oxygenation of blood
28
29
30
Gas Exchange
The rate of diffusion between two regions is
governed by Fick’s law of diffusion
D A Dp
R=
d
R = Rate of diffusion
D = Diffusion constant
A = Area over which diffusion takes places
Dp = Pressure difference between two sides
d = Distance over which diffusion occurs 31
Lungs
-Lungs of mammals are packed with millions of alveoli (sites of
gas exchange)
-Inhaled air passes through the larynx, glottis and trachea
-Bifurcates into the right and left bronchi, which enter each lung
and further subdivide into bronchioles
32
-Surrounded by an extensive capillary network
Lungs
Air exerts a pressure downward, due to gravity
-A pressure of 760 mm Hg is defined as one
atmosphere (1.0 atm) of pressure
Partial pressure is the pressure contributed
by a gas to the total atmospheric pressure
-Based on the % of the gas in dry air
-PN2 = 760 x 79.02% = 600.6 mm Hg
-PO2 = 760 x 20.95% = 159.2 mm Hg
-PCO2 = 760 x 0.03% = 0.2 mm Hg
33
34
Lungs
Lungs of amphibians are formed as saclike
outpouchings of the gut
Frogs have positive pressure breathing
-Force air into their lungs by creating a
positive pressure in the buccal cavity
Reptiles have negative pressure breathing
-Expand rib cages by muscular contractions,
creating lower pressure inside the lungs
35
36
Lung Structure and Function
During inhalation, thoracic
volume increases
through contraction
of two muscle sets
-Contraction of the external
intercostal muscles expands
the rib cage
-Contraction of the diaphragm
expands the volume of thorax
and lungs
-Produces negative pressure
which draws air into
the lungs
37
Lung Structure and Function
Tidal volume = Volume of air moving in and
out of lungs in a person at rest
Vital capacity = Maximum amount of air that
can be expired after a forceful inspiration
Hypoventilation = Insufficient breathing
-Blood has abnormally high PCO2
Hyperventilation = Excessive breathing
-Blood has abnormally low PCO2
38
Lung Structure and Function
Each breath is initiated by neurons in a
respiratory control center in the medulla
oblongata
-Stimulate external intercostal muscles
and diaphragm to contract, causing
inhalation
-When neurons stop producing impulses,
respiratory muscles relax, and exhalation
occurs
39
Gas Exchange
Gas exchange is driven by
differences in partial pressures
-As a result of gas exchange
in the lungs, systemic arteries
carry oxygenated blood with
relatively low CO2 concentration
-After the oxygen is
unloaded to the tissues,
systemic veins carry
deoxygenated blood with a high
CO2 concentration
40
Lung Structure and Function
Neurons are sensitive to blood PCO2 changes
-A rise in PCO2 causes increased production
of carbonic acid (H2CO3), lowering the pH
-Stimulates chemosensitive neurons in
the aortic and carotid bodies
-Send impulses to control center
Brain also contains central chemoreceptors
that are sensitive to changes in the pH of
cerebrospinal fluid (CSF)
41
Lung Structure and Function
-Each breath is initiated by
neurons in a respiratory control
center in the medulla oblongata
42
Respiratory Diseases
Chronic obstructive pulmonary disease
(COPD) refers to any disorder that obstructs
airflow on a long-term basis
-Asthma = An allergen triggers the release
of histamine, causing intense constriction of
the bronchi and sometimes suffocation
-Emphysema = Alveolar walls break down
and the lung exhibits larger but fewer alveoli
-Lungs become less elastic
43
Respiratory Diseases
Lung cancer follows or accompanies COPD
-The number one cancer killer
-Caused mainly by cigarette smoking
44
RBCs of vertebrates contain Hemoglobin,
a pigment that binds and transports
oxygen
Hemoglobin consists of four polypeptide chains:
two a and two b
-Each chain is associated with a heme group,
and each heme group has a central iron atom
that can bind a molecule of O2
Hemoglobin loads up with oxygen in the lungs,
forming oxyhemoglobin
-Some molecules lose O2 as blood passes in
capillaries, forming deoxyhemoglobin
45
Hemoglobin
In a person at rest, about one-fifth of the
oxygen is unloaded in the tissues
-Leaving four-fifths of the oxygen in the
blood as a reserve
-This reserve enables the blood to supply
body’s oxygen needs during exertion
The oxyhemoglobin dissociation curve is a
graphic representation of these changes
46
Hemoglobin
47
Hemoglobin
Hemoglobin’s affinity for O2 is affected by pH
and temperature
-The pH effect is known as the Bohr shift
-Caused by H+ binding to hemoglobin
-Results in a shift of oxyhemoglobin
dissociation curve to the right
-Facilitates oxygen unloading
-Increasing temperature has a similar effect
48
Hemoglobin
49
Gas Exchange Biochemistry
In Tissue Cells
-Mitochondria release CO2 after pyruvate oxidation and the
Krebs Cycle
Mitochondria also reduce
oxygen to H20 (water)
at the end of the electron
transport chain.
C02 leaves tissue cells
50
Gas Exchange Biochemistry
In Red Blood Cells & Plasma
-The enzyme carbonic anhydrase combines CO2 with H2O to form
H2CO3
-H2CO3
into H+
dissociates
and HCO3–
-H+ binds to deoxyhemoglobin
making O2 get into tissue
-HCO3– moves out of the
blood, and into plasma
acts as buffer
72% of the CO2 in blood is
“hidden” in HCO3
51
Gas Exchange Biochemistry
Into Alveoli
-CO2 goes into Alveoli...HCO3– moves INTO red blood cells
-H+ and HCO3– associate
into H2CO3
-H2CO3 changes into CO2
with H2O
-CO2 leaves Red Blood Cells
and goes into the alveoli
THEN YOU EXHALE IT
...Bronchioles, bronchi,
trachea, pharynx, mouth,
atmosphere!!
52
Transportation of Carbon Dioxide
When blood passes through pulmonary capillaries,
these reactions are reversed
-The result is the production of CO2 gas, which is
exhaled
Other dissolved gases are also transported by
hemoglobin
-For example, nitric oxide (NO) and carbon
monoxide (CO)...so these molecules compete
with, oxygen, the terminal electron acceptor
in the electron transport chain...can be deadly
53