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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

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invertebrate circulatory systems
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

invertebrate circulatory systems1
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 & transported away from and back to the heart

vertebrate circulatory systems
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

later evolved vertebrate circulatory systems
Later-Evolved Vertebrate Circulatory Systems

-Oxygenated and deoxygenated blood don’t mix in heart

heart valves
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 valvesguard the exits from the ventricles to the arterial system

-Pulmonary valve = On the right

-Aortic valve = On the left

the cardiac cycle
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 diastolic pressure


Contraction of Heart Muscle

Autorhythmic SA node



Electrocardiogram (ECG or EKG)

characteristics of blood vessels
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

cardiovascular diseases
Cardiovascular Diseases


-Accumulation of fatty material within arteries


-Arterial hardening due to calcium deposition

blood flow and blood pressure
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

blood flow and blood pressure1
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

blood flow and blood pressure2
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.

veins and venules
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 one-way venous valves


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

the components of blood
The Components of Blood

Plasma is 92% water, but it also contains the following solutes:

-Nutrients, wastes, and hormones



-Albumin,alpha (a) & beta (b) globulins


-If removed, plasma is called serum

the components of blood1
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

white blood cells
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







3. Cascade of


reactions is

triggered by


plasma factors,

and damaged


1. Vessel is




tissue to blood.

2. Platelets

adhere and


sticky, forming

a plug.

5. Once tissue


is healed,

the clot is


4. Threads of

fibrin trap


and form

a clot.

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


Making Blood “Formed Elements”

All of the “formed elements”

develop from pluripotent

stem cells

Hematopoiesisis 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


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

gas exchange
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


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


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


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

gas exchange1

D A Dp

R =


Gas Exchange

The rate of diffusion between two regions is governed by Fick’s law of diffusion

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



-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

-Surrounded by an extensive capillary network


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


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

lung structure and function
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

lung structure and function1
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

lung structure and function2
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

gas exchange2
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

lung structure and function3
Lung Structure and Function

Neurons are sensitive to blood PCO2changes

-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)

lung structure and function4
Lung Structure and Function

-Each breath is initiated by

neurons in a respiratory control

center in the medulla oblongata

respiratory diseases
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

respiratory diseases1
Respiratory Diseases

Lung cancer follows or accompanies COPD

-The number one cancer killer

-Caused mainly by cigarette smoking

rbcs of vertebrates contain hemoglobin a pigment that binds and transports oxygen
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 loseO2as blood passesin capillaries, forming deoxyhemoglobin


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


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


-Mitochondria release CO2 after pyruvate oxidation and the Krebs CycleMitochondria also reduce oxygen to H20 (water) at the end of the electron transport chain. C02 leaves tissue cells

Gas Exchange Biochemistry

In Tissue Cells


Gas Exchange Biochemistry

In Red Blood Cells & Plasma

-The enzyme carbonic anhydrase combines CO2 with H2O to form H2CO3-H2CO3 dissociates into H+ and HCO3– -H+ binds to deoxyhemoglobinmaking O2 get into tissue-HCO3– moves out of the blood, and into plasmaacts as buffer 72% of the CO2 in blood is“hidden” in HCO3


-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 Cellsand goes into the alveoliTHEN YOU EXHALE IT...Bronchioles, bronchi,trachea, pharynx, mouth,atmosphere!!

Gas Exchange Biochemistry

Into Alveoli

transportation of carbon dioxide
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) these molecules compete with, oxygen, the terminal electron acceptor in the electron transport chain...can be deadly