Circulatory System and Gas Exchange

Crestley Wong

Kiran Varghese

Connor Fong

Ajay Nair Sharma

Transport Systems Connect Organs with Cells Diffusion alone is not enough for

transporting chemicals in animals. The time it takes for a substance to

diffuse is proportional to the square distance the substance will travel.

Circulatory system ensures no substance will difuse far to enter or leave the cell.

Most Invertebrates Have either:

Gastrovascular Cavity Hydra, Cnidarians, Planarians,

flatworms. A body wall encloses a central

gastrovascular cavity, which serves the funcitons of digestion and distributions of substances throughought the body.

Both inner and outer layers of the tissue are bathed by fluid.

Thin branches of the vacity extend into the tentacles of the organims.

Only the cells of the inner layer have diret access to nutrients.

OR Open/Closed Circulatory System.

Open C.S: Blood bathes the internal organs directly. Blood and interstitial fluid is collectively called

hemolymph. A heart(s) pump the hemolymph into a system of

interconnected sinuses, spaces that surround the organism.

When heart relaxes, it draws in hemolymph through pores called ostia.

Closed C.S: Blood confined to vessels and is distinct from the interstitial fluid.

Heart(s) pump blood into large vessels that branch into smaller ones coursing through the organs.

3 Parts of a C.S. System Blood Heart

1 or 2 atrium/atria, the chambers that receive blood returning to the heart.

1 or 2 ventricles, the chambers pumping blood out of the heart.

QuickTime™ and a decompressor

are needed to see this picture.

Blood Vessels Arteries carry blood away from the heart to

organs throughout the body. Arteries branch into arterioles, small vessels

that convey blood to the capillaries. Capillaries are microscopic vessels with

thin porous walls. Gas exchange occurs across capillary walls. Networks of capillaries are called capillary

beds, and inhabit each tissue. At their “end”, cappilaries form into venules.

Venules form into veins.

Veins return blood to the heart

Different Animals, different C.S. Fish- 2 chambers: 1 atrium, 1 ventricle.

Blood goes from ventricle to gills, where gas exchange occurs. Gill capillaries converge into a vessel that carries the

oxygen-rich blood throughout the body. Blood returns in veins back to atrium.

Amphibians- 3 chambers: 2 atria, 1 ventricle. Pulmocutaneous circuit: Leads blood to gas exchange

tissues. Blood gets oxygen and pumped to… Systemic circuit: Carries oxygen-rich blood to all body

organs and returns it to right atrium via veins. This is called double circulation, which ensures blood

flow to brain, muscles, and other organs because the blood is pumped a second time after it loses pressure in the capillary beds.

Mammalian Heart Left side- Oxygen-rich blood

Right side- Oxygen-poor blood 2 atria: Thin walls, collection chambers for

returning blood, pump blood short distance. 2 ventricles: Thick walls, very powerful. Left

ventricle extra powerful because it pumps blood to all body organs.

Each valve has a flap, preventing blood backflow.

Atrioventricular (AV) valve: Between each atrium and ventricle. Anchored by strong fibers. Pressure generated from ventricles close the AV valve.

Semilunar valves: Located at the two exits of the heart. The blood that’s pumped into arteries must leave these valves. Pressure from ventricles open/close the valves. Right side of heart: oxygen-poor blood.

Left side of heart: oxygen-rich blood. One complete sequence of

pumping/filling is called cardiac cycle. The contraction phase is called

systole, and a relaxation phase is called diastole.

Maintaining the Heart’s Rhythmic Beat

Certain cells of the heart are self-excitable; they can contract without signal from the nervous system.

Region called the sinoatrial (SA) node, or pacemaker, maintains the rhythm by setting the rate at which the cardiac muscle cells contract. Located in the wall of the right atrium. Generates electrical impulses through the atria

walls, causing them to contract in unison. The impulses pass off to the atrioventricular (AV)

node, which delays the impulses to ensure the atria will fully contract and empty before the ventricles do.

SA Node Influenced by different cues:

2 sets of nerves oppose each other in adjusting heart rate.

Hormones: secreted into blood by glands.

Body temperature: increase in temperature, increases in heart rate (ex: fever)

Exercise.

Blood Vessel Tissue Arteries have 3 layers:

Outside: layer of connective tissue with elastic fibers.

Middle: Smooth muscle and more elastic fibers. Lining: an endothelium, a single layer of flat

cells, provides a smooth surface minimizing the resitance to blood.

Capillaries only have a layer of endothelium. Dut to gas exchange.

Arteries have ticker middle and out layers than veins. Due to varying amounts/pressure.

Thinner walled veins convey blood back to the heart at low velocity and pressure.

Arteries: To Cap. Veins: From Cap.

Blood Flow Velocity Law of Conformity: Fluid will stream through

narrower segments of pipe faster than it flows through wider segments. Total cross-sectional area of the pipes

determines flow rate. Blood slows down as it enters the arterioles

from arteries and flows slowest in the capillary beds. Because each artery conveys blood to so many

capillaries, the total (cumulative) diameter of the vessels is larger in capillary beds.

Blood Pressure The hydrostatic force that blood exerts

against the wall of a vessel is called blood pressure.

Pressure greater in arteries than veins. Fluid goes from areas of HIGH

pressure TO areas of LOW pressure When the heart contracts, blood enters

the arteries faster than it leaves, and the vessels stretch as a result.

Blood Pressure is determined partly by cardiac output and partly by the degree of peripheral resistance to blood flow.

Capillary Function

5% - 10% of the body’s capillaries have blood flowing through them.

Capillaries in the major organs are filled to capacity with blood.

QuickTime™ and a decompressor

are needed to see this picture.

Two Mechanisms Two mechanisms regulate the distribution of

blood in capillary beds. Contraction of the smooth muscle layer in

the wall of an arteriole constricts the arteriole, decreasing blood flow. When the muscle relaxes the arteriole dilates, allowing blood to enter the capillaries.

Rings of smooth muscle called precapillary sphincters control the flow between arterioles and venules.

Capillary Exchange The transfer of substances between the blood and

the intestinal fluid takes place across the thin endothelial walls of the capillaries.

Some substances may be carried across an endothelial cell in vesicles that form by endocytosis on one side of the cell and then release their contents by exocytosis on the opposite side.

About 85% of the fluid that leaves the blood at the arterial end of a capillary bed reenters from the intestinal fluid at the venous en, and the remaining 15% of the fluid lost from capillaries is eventually returned to the blood by the vessels of the lympathetic system.

The Lymphatic System Lost fluids and proteins are returned

to the blood via the lymphatic system.

Fluids enter by diffusing into tiny lymph capillaries that are intermingled among the blood capillaries.

The system help defend the body against infection and maintains the volume and protein concentration.

Blood as a Connective tissue

Blood consists of several kinds of cells suspended in a liquid matrix called plasma

The cellular elements occupy about 45% of the volume of blood.

Plasma Blood plasma is about 90% water. Consists of water and dissolved ions, which

help maintain osmotic balance. Plasma proteins act as buffers against pH

changes, help maintain the osmotic balance between blood and intestinal fluid, and contribute to blood viscosity.

QuickTime™ and a decompressor

are needed to see this picture.

Cellular Elements RBC’s, WBC’s, and Platelets. RBC

Biconcave disk Mammal RBC’s lack nuclei,

mitochondria and generate their ATP exclusively by anaerobic metabolism.

Main function is to carry oxygen. Contains about 250 million molecules

of hemoglobin.

WBC Five types: monocytes, nuetrophils,

basophils, eosinophils, and lymphocytes. Main function is to fight infections. Monocytes and nuetrophils are

phagocytes. Platelets

Fragments of cells. No nuclei and originate as cytoplasm

fragments of bone marrow. Functions in blood clotting

Stem Cells and Replacement

Cellular elements are replaced constantly.

They develop from a common source, pluripotent stem cells.

RBC production is controlled by a negative feedback mechanism.

Blood Clotting Fibrinogen is the inactive sealant

present in out blood. Once activated it turns into fibrin

which aggregates into threads that form the fabric of the clot.

The clotting mechanism begins with the release of clotting factors from platelets.

Cardiovascular Diseases

Heart attack The death of cardiac muscle tissue in

the heart. Stroke

The death of nervous tissue in the brain.

Hypertension High blood pressure.

Gas exchange • Gas exchange is the uptake of molecular oxygen (O₂)

from the environment and the discharge of carbon dioxide (CO₂) to the environment .

• Animals require a continuous supply of 0₂ for cellular respiration. They must also dispose of CO₂, the waste product of cellular respiration.

• The source of oxygen, called the respiratory medium, is air for terrestrial animals and water for aquatic animals.

• The part of an animal where oxygen from the environment diffuses into living cells and carbon dioxide diffuses out is called respiratory surface.

• The respiratory surface is moist.

Gills• Gills are variously shaped outfoldings of the body surface

specialized for gas exchange.• Gills must be very efficient to obtain oxygen from water.• Ventilation increases the flow of the respiratory medium over

the respiratory surface. • Ventilation brings a fresh supply of oxygen and removes

carbon dioxide expelled from the gills• The arrangement of capillaries in the gills of a fish also

enhances gas exchange.• Countercurrent exchange is a process where blood flows

through the capillary and becomes more and more loaded with oxygen.

• It simultaneously encounters water with ever higher oxygen concentrations because the water is just beginning its passage over the gills. This means that along the entire length of the capillary, there is a diffusion gradient favoring the transfer of oxygen from the water to the blood.

Tracheal System• Since O₂ and CO₂ diffuse much faster in air than in water,

respiratory surfaces exposed to air do not have to be ventilated as thoroughly as gills.

• The trachael system, which is made up of air tubes that branch throughout the body, is one variation on the theme of a folded internal respiratory surface.

• The largest tubes, called tracheae, open to the outside.• The finest branches extend to the surface of nearly every cell,

where gas is exchanged by diffusion across the moist epithelium that lines the terminal ends of the tracheal system.

• Diffusion brings enough O₂ from the air into the tracheal system and removes enough CO₂ to support cellular respiration.

Lungs• The lungs are restricted to one location• The gap between the respiratory surface of a lung and

the other parts of the body must be bridged by the circulatory system, which transports oxygen from the lungs to the rest of the body.

• Lungs have a dense net of capillaries just under the epithelium, which serves as the respiratory surface

Mammalian Respiratory Systems• A system of branching ducts conveys air to the lungs.• Air enters through the nostrils and is then filtered by

hairs.• The nasal cavity leads to the pharynx, an intersection

where the paths for air and food cross. • When food is swallowed, the larnyx (upper part of the

respiratory tract) moves upward and tips the epiglottis over the glottis (the opening of the windpipe)

• When air is exhaled, it rushes by a pair of vocal cords in the larynx, and sounds are produced when voluntary muscles in the voicebox are tensed, stretching the cords so they vibrate.

Continued next slide.

• From the larynx, air passes into the trachea, or windpipe.

• The trachea forks into two bronchi, one leading to each lung

• The bronchus branches repeatedly into finer and finer tubes called bronchioles

• The epithelium lining the major branches of the respiratory tree is covered by cilia and a thin film of mucus, which helps clean the respiratory system.

• At the tips of the bronchioles are air sacs called alveoli

SO REMEMBER… Lungs

Nostrils Pharynx

Larynx Trachea

Bronchi Bronchioles

Alveoli

Ventilating the Lungs• Positive pressure breathing is when air is pushed down the

windpipe• Negative pressure breathing is when air is pulled down the lungs• The volume of the lungs increases as a result of contraction of the

rib muscles and the diaphragm, a sheet of skeletal muscles that forms the bottom wall of the chest cavity

• Contraction of the rib muscles expands the rib cage by pulling the ribs upward and the breastbone outward.

• At the same time, the chest cavity expands as the diaphragm contracts and descends like a piston

• All of these changes increase the lung volume. So the air pressure within the alveoli becomes lower than atmospheric pressure

• The volume of air an animal inhales and exhales with each normal breath is called tidal volume

• Birds have parabronchi, which are tiny channels through which air flows continuously in one direction

Breathing Control Centers• Our breathing control centers are located in two regions of

the brain, the medulla oblongata and the pons• Aided by the control center in the pons, the medulla’s

center sets the basic breathing rhythm. • The medulla monitors the CO₂ level of the blood and

regulates the amount of CO₂ our alveoli dispose when we exhale.

• When the O₂ level in blood is severely depressed, O₂ sensors in the aorta and carotid arteries in the neck send alarm signals to the breathing control centers, and the centers respond by increasing the breathing rate

• The breathing center responds to a variety of nervous and chemical signals, adjusting the rate and depth of breathing to meet the changing demands of the body.

Partial Pressure

•For a gas, whether present in air or dissolved in water, diffusion depends on differences in a quantity called partial pressure

Oxygen Transport Very little dissolved oxygen is transported

in blood Oxygen is carried through respiratory

pigments in most animals These pigments are proteins that get

their color from metal atoms in the blood Hemocyanin is one that has copper binding

the oxygen, causing bluish blood

Hemoglobin Hemoglobin is the

respiratory pigment of most vertebrates

It consists of 4 subunits, each with a cofactor called heme that has iron in the center The iron binds the

oxygen to the pigment, allowing one hemoglobin to carry 4 oxygen molecules

Loading and unloading depends on the cooperation of the subunits

Cooperative Binding Cooperative oxygen

binding is evident in the dissociation curve

Even the slightest change in oxygen partial pressures causes hemoglobin to load or unload a large amount of oxygen

Since hemoglobin is a protein, its conformation is sensitive to environmental factors

Carbon Dioxide Transport

Carbon dioxide expelled from respiring cells diffuses into blood plasma, then into red blood cells

Carbon dioxide reacts with water to form carbonic acid, then dissociates into a hydrogen ion and bicarbonate ion The hydrogen ions attach to hemoglobin and do not

affect the pH of blood The bicarbonate ions diffuse into plasma When blood flows through the lungs, the process

is reversed and converts bicarbonate into CO2

Deep Diving Mammals The Weddell seal can stay submerged in water

for about 20 min. Its capacity for holding oxygen is about twice

that of humans, holding most of its oxygen in blood rather than lungs

Another adaptation is a large spleen, allowing many red blood cells to be loaded with oxygen

They have a higher concentration of myoglobin, an oxygen storing protein, than most other mammals

They are able to decrease their heart rates and restrict blood supply to muscles during long dives

QuickTime™ and a decompressor

are needed to see this picture.

Fin!

GROUP QUIZ

Da, da, daaaaaaaaaaaaaaaaa

1. Which of the following statement(s) is true for an insect?

I. These animals breathe using a system of trachea.

II. Insect tracheoles are not filled with fluid.

III. Every body cell is close to a tracheole.

a) I and III only b) II only c) I and II only d) II and III only e) I, II, and III

2. Which of the following statements is (are) true about countercurrent flow?

I. It takes place in the respiratory systems of all vertebrates.

II. It is the movement of blood and water in opposite directions across gills to ensure maximum diffusion of oxygen.

III. It ensures that maximum transfer of oxygen to the blood takes place.

a) I only b) II only c) III only d) I, II, and III e) II and III only

3.The___________prevents food and liquid from entering the____________.

a) trachea; bronchiolesb) epiglottis; tracheac) pharynx; trachead) epiglottis; diaphragme) bronchi; bronchioles

4. What are the partial pressures of oxygen and carbon dioxide at sea level?

a) 160 mm mercury and 0.23 mm mercury b) 160 mm mercury and 23 mm mercury c) 16 mm mercury and 0.23 mm mercury d) 1.6 mm mercury and 0.23 mm mercury

5. Gas exchange depends on:a) Active transportb) Countercurrent flowc) Internal organs close to the body surface

d) Gill or lungse) Diffusion

6. A hemoglobin molecule is made up of:

a) Four peptide subunits, each bound to a heme unit

b) Four peptide subunits, and a single central heme unit

c) Four heme units and a central globin unit

d) Two peptide subunits, each bound to a heme unit

e) Two peptide subunits and a single central heme unit

7.Which of the following statement(s) is true for an animal with an open circulatory system?

I. These animals have a tube-shaped heart

II. These animals have an extensive network of blood vessels

III. The organs of these animals are directly bathed in hemolymph

a) I only b) II only c) I and III only d) I and II only e) I, II and III

8. Which of the following has a heart with a single atrium and a single ventricle?

I. Amphibian II. Bird III. Fish

a) I only b) II only c) I and III only d) III only e) I, II, and III

9. The pulmonary vein: a) Takes blood from the heart to

the lungs b) Takes blood from the lungs to

the body organs c) Takes blood from the body

organs to the heart d) Takes blood from the kidneys

to the venous system returning blood to the heart

e) Takes blood from the lungs to the heart

10. Which of the following is (are) true of capillaries?

I. They have muscular walls II. They are surrounded by layers of

elastic tissue III. Their walls are only a single cell

layer thick

a) I only b) I and II only c) I and III only d) II and III only e) III only

11. Which of the following is not usually considered to be a risk factor for heart disease?

a) High blood pressureb) Cholesterol levelc) Moderate activityd) Smoking e) Weight