Ch. 42 -- Circulation and Gas Exchange

endothelin

A peptide produced by a blood vessel's endothelium that causes the vessel to constrict.

CO2 + H20

H2CO3 -> H+ + HCO3- carbonic acid bicarbonate

systolic/diastolic

blood pressure 120/80

capillary beds

sites of chemical exchange between the blood and interstitial fluid

atria

upper chambers of the heart; chambers that receive blood entering the heart

How an Amphibian Breathes

v diff from birds or mammals (missing diaphragm): Positive Pressure Breathing ventilates its lungs by positive pressure breathing, which forces air down the trachea

partial pressure equation

% concentration of gas x total pressure of gas mixture

hemolymph

In invertebrates with an open circulatory system, the body fluid that bathes organs/tissues. "blood" of open circulatory systems

Open Circulatory Systems

blood is only partially contained within a system of blood vessels as it travels through the body In insects, other arthropods, and some molluscs, circulatory fluid called hemolymph bathes the organs directly in an open circulatory system (directly contacts organs and cells)

how are circulatory systems linked?

1.Direct contact with environment 2.Fluid-filled circulatory system

Bohr shift

A lowering of the affinity of hemoglobin for oxygen, caused by a drop in pH; facilitates the release of oxygen from hemoglobin in the vicinity of active tissues. CO2 produced during cellular respiration lowers blood pH and decreases the affinity of hemoglobin for O2 Low pH decreases the affinity of hemoglobin for O2

Blood Pressure and Gravity

Animals with long necks require a very high systolic pressure to pump blood a great distance against gravity

Blood Composition and Function

Blood in vertebrates is a connective tissue consisting of several kinds of cells suspended in a liquid matrix (plasma) Cells and cell fragments occupy about 45% of the volume of blood With open circulation, the fluid is continuous with the fluid surrounding all body cells The closed circulatory systems of vertebrates contain a more highly specialized fluid called blood Plasma & Cell Fragments

veins

Blood vessels that carry blood back to the heart

Dissociation Curves for Hemoglobin at 37ºC (Variable pH)

Bohr shift--CO2 produced during cellular respiration lowers blood pH and decreases the affinity of hemoglobin for O2 Hemoglobin plays a minor role in transport of CO2 and assists in buffering the blood Hb retains less O2 at lower pH (high [CO2])

systole

Contraction of the heart

What is the function of a circulatory system?

It brings a transport liquid into close contact with all cells in the body.

pulmonary circulation vs systemic circulation

Pulmonary - pathway of blood from heart to lungs and back Systemic - all blood vessels other than those associated with lungs The pulmonary circulation is the lower-pressure circuit to the lung, whereas the systemic circulation is the higher-pressure circuit to the rest of the body.

What regulates exchange between capillaries and the interstitial fluid?

blood pressure and osmotic pressure

precapillary sphincters

control the blood flow into capillary beds / tissues

Double Circulation in Mammals vs. Amphibians

-In reptiles and mammals, oxygen-poor blood flows through the pulmonary circuit to pick up oxygen through the lungs -In amphibians, oxygen-poor blood flows through a pulmocutaneous circuit to pick up oxygen through the lungs and skin (Some vertebrates with double circulation are intermittent breathers) Amphibians and many reptiles may pass long periods without gas exchange or relying on gas exchange from another tissue, usually the skin Frogs and other amphibians have a three-chambered heart: two atria and one ventricle A ridge in the ventricle diverts most of the oxygen-rich blood into the systemic circuit and most oxygen-poor blood into the pulmocutaneous circuit When underwater, blood flow to the lungs is nearly shut off Turtles, snakes, and lizards have a three-chambered heart: two atria and one ventricle, partially divided by an incomplete septum In alligators, caimans, and other crocodilians, a septum divides the ventricles, but pulmonary and systemic circuits connect where arteries exitthe heart Mammals and birds have a four-chambered heart with two atria and two ventricles The left side of the heart pumps and receives only oxygen-rich blood, while the right side receives and pumps only oxygen-poor blood Mammals and birds are endotherms and require more oxygen than ectotherms

Closed Circulatory Systems Benefits:

-more efficient (delivery of O2 and nutrients and excretion of CO2) especially for larger mammals -increases/allows tighter/more regulation of blood flow

RIght Side of Heart (Double Circulation)

-pump O2-low blood to lungs for gas exchange Pulmonary Circuit

Open Circulatory Systems Benefits

-uses less energy (due to low hydrostatic pressure) -additional functions to circulatory system e.g. spiders use hydrostatic pressure to extend the legs

Coordination of Circulation and Gas Exchange

1 During inhalation, fresh air mixes with air remaining in the lungs. 2 The resulting mixture formed in the alveoli has a higher PO2PO2 than the blood flowing through the alveolar capillaries. Consequently, there is a net diffusion of O2O2 down its partial pressure gradient from the air in the alveoli to the blood. Meanwhile, the presence of a PCO2PCO2 in the alveoli that is higher in the capillaries than in the air drives the net diffusion of CO2CO2 from blood to air. 3 By the time the blood leaves the lungs in the pulmonary veins, its PO2PO2 and PCO2PCO2 match the values for the air in alveoli. After returning to the heart, this blood is pumped through the systemic circuit. 4 In the systemic capillaries, gradients of partial pressure favor the net diffusion of O2O2 out of the blood and CO2CO2 into the blood. These gradients exist because cellular respiration in the mitochondria of cells near each capillary removes O2O2 from and adds CO2CO2 to the surrounding interstitial fluid. 5 Having unloaded O2O2 and loaded CO2CO2, the blood is returned to the heart and pumped to the lungs again. 6 There, exchange occurs across the alveolar capillaries, resulting in exhaled air enriched in CO2CO2 and partially depleted of O2O2.

Circulatory Systems (has to have)[3]:

1. A circulatory fluid 2. A set of interconnecting vessels 3. A muscular pump, the heart The circulatory system connects the fluid that surrounds cells with the organs that exchange gases, absorb nutrients, and dispose of wastes Circulatory systems can be open or closed The heart powers circulation by using metabolic energy to elevate the circulatory fluid's hydrostatic pressure, the pressure the fluid exerts on surrounding vessels. The fluid then flows through the vessels and back to the heart.

control of heart rhythm

1. Sinoatrial node generates signal causing both atria to contract 2. Signal delayed at atrioventricular node to let atria empty 3. AV node passes signal to heart apex 4. Signal spreads throughout ventricle walls Impulses from the SA node first spread rapidly through the walls of the atria, causing both atria to contract in unison. During atrial contraction, the impulses originating at the SA node reach other autorhythmic cells located in the wall between the left and right atria. These cells form a relay point called the atrioventricular (AV) node. Here the impulses are delayed for about 0.1 second before spreading to the heart apex. This delay allows the atria to empty completely before the ventricles contract. Then the signals from the AV node are conducted to the heart apex and throughout the ventricular walls by specialized structures called bundle branches and Purkinje fibers. Sympathetic and Parasympathetic regulation via NS H regulation via Endocrine regulation body temp (An increase of only 1°C raises the heart rate by about 10 beats per minute. This is the reason your heart beats faster when you have a fever.)

Hemoglobin (Hb)

12-16 gm/100 mL blood bind O2 in reversible fashion lung: load tissue: unload 4 binding spots in structure Cooperative loading: when 1 O2 binds it, changes the shape of Hb to increase affinity for O2 unloading: 4 molecules bound, 1 unloads, other 3 more easily released (decrease affinity)

partial pressure of O2

160 mmHg 0.21*760 1. overall pressure exerted by gas mixture 2. % of mixture of gas

Cell and cell fragments suspended in plasma

45% volume of blood: 1. RBC 2. WBC 3. Platelets: cell fragments Cellular elements Erythrocytes: RBCs Leukocytes: WBCs Platelets Suspended in blood plasma are two types of cells: Red blood cells (erythrocytes) transport oxygen Erythrocytes Red blood cells, or erythrocytes, are the most numerous blood cells They contain hemoglobin, the iron-containing protein that transports oxygen In mammals, mature erythrocytes lack nuclei and mitochondria White blood cells (leukocytes) function in defense Leukocytes There are five major types of white blood cells, or leukocytes They function in defense either by phagocytizing bacteria and debris or by mounting immune responses against foreign substances They are found both in and outside of the circulatory system Platelets Platelets are fragments of cells and function in blood clotting

plasma

55% 1. water 2. inorganic salts 3. proteins 4. nutrients Plasma contains inorganic salts as dissolved ions Plasma proteins influence blood pH and help maintain osmotic balance between blood and interstitial fluid Plasma is similar in composition to interstitial fluid, but plasma has a much higher protein concentration

positive pressure breathing

A breathing system used by amphibians in which air is forced into the lungs. Inhalation begins when muscles lower the floor of an amphibian's oral cavity, drawing in air through its nostrils. Next, with the nostrils and mouth closed, the floor of the oral cavity rises, forcing air down the trachea. Exhalation follows as air is expelled by the elastic recoil of the lungs and by compression of the muscular body wall. When male frogs puff themselves up in aggressive or courtship displays, they disrupt this breathing cycle, taking in air several times without allowing any release.

cardiac cycle

A complete heartbeat consisting of contraction and relaxation of both atria and both ventricles

The structure and function of fish gills.

A fish continuously pumps water through its mouth and over gill arches, using coordinated movements of the jaws and operculum (gill cover) for this ventilation. (A swimming fish can simply open its mouth and let water flow past its gills.) Each gill arch has two rows of gill filaments, composed of flattened plates called lamellae. Blood flowing through capillaries within the lamellae picks up O2O2 from the water. Notice that the countercurrent flow of water and blood maintains a partial pressure gradient that drives the net diffusion of O2O2 from the water into the blood over the entire length of a capillary.

tracheal system

A gas exchange system of branched, chitin-lined tracheal tubes that infiltrate the body and carry oxygen directly to cells in insects. The tracheal system of insects consists of a network of branching tubes throughout the body Tracheal tubes supply O2 to cells The respiratory and circulatory systems are separate Larger insects must ventilate their tracheal system to meet O2 demands

atrioventricular (AV) valve

A heart valve located between each atrium and ventricle that prevents a backflow of blood when the ventricle contracts.

bohr shift

A lowering of the affinity of hemoglobin for oxygen, caused by a drop in pH; facilitates the release of oxygen from hemoglobin in the vicinity of active tissues. dec. in pH ---> dec affinity of Hb for O2----> facilitates release of O2 from hemoglobin in the vicinity of active tissue (Co2 produced during cellular respiration lowers blood pH and decreases Hb affinity for O2)---> release more O2

Dissociation Curves for Hemoglobin at 37ºC (Constant pH)

A single hemoglobin molecule can carry four molecules of O2, one molecule for each iron-containing heme group The hemoglobin dissociation curve shows that a small change in the partial pressure of oxygen can result in a large change in delivery of O2 cooperativity displayed at the sharpest slope on the graph

Rank hemoglobin molecules with the described conditions from most likely to bind oxygen molecules to most likely to release oxygen molecules.

A single hemoglobin molecule consists of four subunits, each of which can bind an oxygen molecule. Hemoglobin is more likely to bind oxygen when the partial pressure of oxygen is high, such as in the lungs. It is more likely to release oxygen when the partial pressure of oxygen is low, such as in body tissues. As oxygen molecules bind to hemoglobin, the protein undergoes conformational changes, making it more likely that the other subunits will bind oxygen molecules. Conversely, as oxygen releases from hemoglobin, conformational changes make it more likely that the other subunits will release oxygen. This cooperative binding helps ensure that hemoglobin becomes fully loaded with oxygen in the lungs and efficiently unloads oxygen in the tissues.

Basic Blood Vessel Structure and Function

All blood vessels contain a central lumen (cavity) lined with an endothelium, a single layer of flattened epithelial cells. smooth endothelial layer minimizes resistance to fluid flow. Surrounding the endothelium are tissue layers that differ among capillaries, arteries, and veins, reflecting distinct adaptations to the particular functions of these vessels

How does an increase in the CO2CO2 concentration in the blood affect the pH of cerebrospinal fluid?

An increase in blood CO2CO2 concentration causes an increase in the rate of CO2CO2 diffusion into the cerebrospinal fluid, where the CO2CO2 combines with water to form carbonic acid. Dissociation of carbonic acid releases hydrogen ions, decreasing the pH of the cerebrospinal fluid.

stem cell

Any relatively unspecialized cell that can divide during a single division into one identical daughter cell and one more specialized daughter cell, which can undergo further differentiation. an reproduce indefinitely, dividing mitotically to produce one daughter cell that remains a stem cell and another that adopts a specialized function. The stem cells that produce the cellular elements of blood cells are located in the red marrow inside bones, particularly the ribs, vertebrae, sternum, and pelvis. As they divide and self-renew, these stem cells give rise to two sets of progenitor cells with a more limited capacity for self-renewal

Structure and Function of Arteries and Veins

Arteries - higher pressure - walls are thicker, strong walls. Has elastic lamina - allows arteries to expand and recoil - smooths blood flow. Veins - pressure lower - walls are thinner - lumen larger - have valves. Walls do not expand. both arteries and veins have walls that consist of two layers of tissue surrounding the endothelium. The outer layer is formed by connective tissue that contains elastic fibers, which allow the vessel to stretch and recoil, and collagen, which provides strength. The layer next to the endothelium contains smooth muscle and more elastic fibers. Arterial walls are thick, strong, and elastic. They can thus accommodate blood pumped at high pressure by the heart, bulging outward as blood enters and recoiling as the heart relaxes between contractions -------> maintain/withstand blood pressure and ensure flow of blood The smooth muscles in the walls of arteries and arterioles help regulate the path of blood flow. Signals from the nervous system and circulating hormones act on the smooth muscle of these vessels, causing dilation or constriction that modulates blood flow to different parts of the body. Because veins convey blood back to the heart at a lower pressure, they do not require thick walls. For a given blood vessel diameter, a vein has a wall only about a third as thick as that of an artery. Unlike arteries, veins contain valves, which maintain a unidirectional flow of blood despite the low blood pressure in these vessels.

The Interrelationship of Cross-sectional Area of Blood Vessels, Blood Flow Velocity, and Blood Pressure

Blood flows from areas of higher pressure to areas of lower pressure Blood pressure is a force exerted in all directions, including against the walls of blood vessels The recoil of elastic arterial walls plays a role in maintaining blood pressure The resistance to blood flow in the narrow diameters of tiny capillaries and arterioles dissipates much of the pressure increase cross sectional area decreases velocity narrow diameter of arterioles and capillaries gives substantial resistance to blood flow and pressure. (diameter and Surface Area) INCREASE VELOCITY blood slows as it moves from arteries to arterioles to the much narrower capillaries -----> The number of capillaries is enormous, roughly 7 billion in a human body. Each artery conveys blood to so many capillaries that the total cross-sectional area is much greater in capillary beds than in the arteries or any other part of the circulatory system This enormous increase in cross-sectional area results in a dramatic decrease in velocity from the arteries to the capillaries: Blood travels 500 times more slowly in the capillaries (about 0.1 cm/sec) than in the aorta (about 48 cm/sec). After passing through the capillaries, the blood speeds up as it enters the venules and veins, which have smaller total cross-sectional areas.

Two opposing forces control the movement of fluid between the capillaries and the surrounding tissues:

Blood pressure tends to drive fluid out of the capillaries, and the presence of blood proteins tends to pull fluid back Many blood proteins (and all blood cells) are too large to pass readily through the endothelium, so they remain in the capillaries. These dissolved proteins are responsible for much of the blood's osmotic pressure (the pressure produced by the difference in solute concentration across a membrane). The difference in osmotic pressure between the blood and the interstitial fluid opposes fluid movement out of the capillaries. On average, blood pressure is greater than the opposing forces, leading to a net loss of fluid from capillaries. The net loss is generally greatest at the arterial end of these vessels, where blood pressure is highest.

arteries

Blood vessels that carry blood away from the heart branch into arterioles and carry blood away from the heart to capillaries

Arteries

Blood vessels that carry blood away from the heart higher pressure - walls are thicker, strong walls. Has elastic lamina - allows arteries to expand and recoil - smooths blood flow. have walls that consist of two layers of tissue surrounding the endothelium: The outer layer is formed by connective tissue that contains elastic fibers, which allow the vessel to stretch and recoil, and collagen, which provides strength. The (inner) layer next to the endothelium contains smooth muscle and more elastic fibers. walls are thick, strong, and elastic. They can thus accommodate blood pumped at high pressure by the heart, bulging outward as blood enters and recoiling as the heart relaxes between contractions -------> maintain/withstand blood pressure and ensure flow of blood

Veins

Blood vessels that carry blood back to the heart - pressure lower - walls are thinner - lumen larger - have valves. Walls do not expand. have walls that consist of two layers of tissue surrounding the endothelium: The outer layer is formed by connective tissue that contains elastic fibers, which allow the vessel to stretch and recoil, and collagen, which provides strength. The (inner) layer next to the endothelium contains smooth muscle and more elastic fibers. convey blood back to the heart at a lower pressure, they do not require thick walls. (For a given blood vessel diameter, this has a wall only about a third as thick as that of an artery). contain valves, which maintain a unidirectional flow of blood despite the low blood pressure in these vessels.

Homeostatic Control of Breathing

Breathing is regulated by involuntary mechanisms The breathing control centers are found in the medulla oblongata of the brain (respiratory drive center) Neurons in the medulla regulates the rate and depth of breathing in response to pH changes in the cerebrospinal fluid Sensors in the aorta and carotid arteries monitor O2 and CO2 levels These signal the breathing control centers, which respond as needed Additional modulation of breathing takes place in the pons, next to the medulla [The neurons mainly responsible for regulating breathing are in the medulla oblongata, near the base of the brain (Figure 42.28). Neural circuits in the medulla form a pair of breathing control centers that establish the breathing rhythm. When you breathe deeply, a negative-feedback mechanism prevents the lungs from overexpanding: During inhalation, sensors that detect stretching of the lung tissue send nerve impulses to the control circuits in the medulla, inhibiting further inhalation.]

Why is diffusion only efficient over short distances?

But such movement is very slow for distances of more than a few millimeters. That's because the time it takes for a substance to diffuse from one place to another is proportional to the square of the distance.

CO2 Transport

CO2 + H2O <-> H2CO3 (carbonic acid) <-> HCO3- (bicarbonate) + H+ this reaction occurs within RBCs, HCO3- exits RBC by exchanging with Cl- 3 ways that CO2 is transported: 1. carbonic anhydrase- enzyme in RBCs that catalyzes rxn 2. attached to hemoglobin (not in O2 position) 3. more water soluble than O2, so in plasma With slight differences in the partial pressure of CO2, the body ensures that CO2 diffuses out of the tissues, into the blood, and then out of the body through the lungs. Most of the CO2 produced during cellular respiration is transported to the lungs in the form of bicarbonate ions in the blood. The incorporation of CO2 into bicarbonate ions lowers the partial pressure of CO2 in the blood, helping draw more CO2 out of the tissues. The incorporation of CO2 into bicarbonate ions in red blood cells roughly follows this process: CO2 reacts with water and forms carbonic acid, a reaction catalyzed by the enzyme carbonic anhydrase. Each molecule of carbonic acid (H2CO3) dissociates into a bicarbonate ion (HCO3 - ) and a proton (H+). Most of the bicarbonate ions diffuse into the blood plasma. (The protons, on the other hand, are bound by hemoglobin, which keeps them from causing a drop in blood pH. In this way, hemoglobin acts as a buffer.) When the blood reaches the lungs, the reverse of the above-described reactions takes place. Bicarbonate ions combine with protons, forming carbonic acid. Carbonic anhydrase catalyzes the conversion of carbonic acid back into CO2, which diffuses into the blood plasma and then into the alveoli, where it is exhaled through the lungs.

systemic circuit

Circuit of blood that carries blood between the heart and the rest of the body. begins with the left side of the heart pumping oxygen-enriched blood from the gas exchange tissues to capillary beds in organs and tissues throughout the body. Following the exchange of O2O2 and CO2CO2, as well as nutrients and waste products, the now oxygen-poor blood returns to the heart, completing the circuit.

Blood Clotting

Coagulation is the formation of a solid clot from liquid blood A cascade of complex reactions converts inactive fibrinogen to fibrin, forming a clot A blood clot formed within a blood vessel is called a thrombus and can block blood flow

What determines whether O2O2 and CO2CO2 undergo net diffusion into or out of capillaries? Explain.

Differences in partial pressure between the capillaries and the surrounding tissues or medium; the net diffusion of a gas occurs from a region of higher partial pressure to a region of lower partial pressure.

gastrovascular cavity (GVC)

Digestive chamber with a single opening, in which cnidarians, flatworms, and echinoderms digest food and distribute gases An opening at one end connects the cavity to the surrounding water. In a hydra, thin branches of the gastrovascular cavity extend into the animal's tentacles. In jellies and some other cnidarians, the gastrovascular cavity has a much more elaborate branching pattern

Respiratory Adaptations of Diving Mammals

Diving mammals have evolutionary adaptations that allow them to perform extraordinary feats Weddell seals in Antarctica can remain underwater for 20 minutes to an hour These animals have: a high blood to body volume ratio myoglobin The Cuvier's beaked whale can dive to 2,900 m and stay submerged for more than 2 hours Diving mammals can store oxygen in their muscles in myoglobin proteins Diving mammals also conserve oxygen by Changing their buoyancy to glide passively Routing blood to vital tissues Deriving ATP in muscles from fermentation once oxygen is depleted

Loading and Unloading of Respiratory Gases

During inhalation, fresh air mixes with air in the lungs The resulting mixture has a higher O2 pressure than the blood flowing through alveolar capillaries In the alveoli, O2 diffuses into the bland and CO2 diffuses into the air By the time the blood leaves the lungs, the pressure of O2 and CO2 match the values for air in the alveoli In the systemic capillaries, gradients of partial pressure favor net diffusion of O2 out of the blood and CO2 into the blood Having unloaded O2 and loaded CO2, the blood is returned to the heart and pumped to the lungs again There, exchange occurs across the alveolar capillaries, resulting in exhaled air enriched in CO2 and partly depleted of O2 gas flow will flow from higher partial pressure to low

Fluid Return by the Lymphatic System

Each day the adult human body loses approximately 4-8 L of fluid from capillaries to the surrounding tissues. There is also some leakage of blood proteins, even though the capillary wall is not very permeable to large molecules. The lost fluid and the proteins within it are recovered and returned to the blood via the lymphatic system Fluid diffuses into the lymphatic system via a network of tiny vessels intermingled with capillaries (Figure 42.15). The recovered fluid, called lymph, circulates within the lymphatic system before draining into a pair of large veins of the cardiovascular system at the base of the neck. This joining of the lymphatic and cardiovascular systems completes the recovery of fluid lost from capillaries as well as the transfer of lipids from the small intestine to the blood Lymph vessels, like veins, have valves that prevent the backflow of fluid. Rhythmic contractions of the vessel walls help draw fluid into the small lymphatic vessels. In addition, skeletal muscle contractions play a role in moving lymph Along a lymph vessel are small, lymph-filtering organs called lymph nodes, which play an important role in the body's defense. Inside each lymph node is a honeycomb of connective tissue with spaces filled by white blood cells, which function in defense. When the body is fighting an infection, the white blood cells multiply rapidly, and the lymph nodes become swollen and tender. This is why your doctor may check for swollen lymph nodes in your neck, armpits, or groin when you feel sick. Because lymph nodes may also trap circulating cancer cells, doctors often examine the lymph nodes of cancer patients to detect the spread of the disease

Capillary Structure

Endothelial tube, inside thin basement membrane No tunica media No tunica externa Diameter is similar to red blood cell smallest blood vessels, having a diameter only slightly greater than that of a red blood cell. Capillaries also have very thin walls, which consist of just an endothelium and a surrounding extracellular layer called the basal lamina. The exchange of substances between the blood and interstitial fluid occurs only in capillaries because only there are the vessel walls thin enough to permit this exchange.

Differentiation of Blood Cells

Erythrocytes, leukocytes, and platelets all develop from a common source of stem cells in the red marrow of bones, especially ribs, vertebrae, sternum, and pelvis The hormone erythropoietin (EPO) stimulates erythrocyte production when O2 delivery is low Physicians can use recombinant EPO to treat people with conditions such as anemia

How does a Feathery Fringe Help this Animal Survive?

FACT: Every organism must exchange substances with its environment FACT: Exchanges ultimately occur at the cellular level by crossing the plasma membrane Question: How would this differ between unicellular and multicellular organisms? In unicellular animals, these exchanges occur directly with the environment For most cells of multicellular organisms, direct exchange with the environment is not possible Gills are an example of a specialized exchange system in animals -O2 diffuses from the water into blood vessels -CO2 diffuses from blood into the water Internal transport and gas exchange are functionally related in most animals

The Structure and Function of Fish Gills

Fish gills use a countercurrent exchange system, where blood flows in the opposite direction to water passing over the gills Blood is always less saturated with O2 than the water it meets In fish gills, more than 80% of the O2 dissolved in the water is removed as water passes over the respiratory surface *** the countercurrent flow of water and blood maintains a partial pressure gradient that drives the net diffusion of O2O2 from the water into the blood over the entire length of a capillary.*** gills drastically increase SA

Valves

Four valves prevent backflow of blood in the heart; keep blood flowing in uniform direction The atrioventricular (AV) valves separate each atrium and ventricle The semilunar valves control blood flow to the aorta and the pulmonary artery The two atria have relatively thin walls and serve as collection chambers for blood returning to the heart The ventricles have thicker walls and contract much more forcefully Made of flaps of connective tissue, the valves open when pushed from one side and close when pushed from the other. The AV valves are anchored by strong fibers that prevent them from turning inside out during ventricular systole. Pressure generated by the powerful contraction of the ventricles closes the AV valves, keeping blood from flowing back into the atria. The "lub-dup" sound of a heart beat is caused by the recoil of blood against the AV valves (lub) then against the semilunar (dup) valves Backflow of blood through a defective valve causes a heart murmur The first heart sound ("lub") is created by the recoil of blood against the closed AV valves. The second sound ("dup") is due to the vibrations caused by closing of the semilunar valves.

Respiratory Surfaces

Gas exchange across respiratory surfaces takes place by diffusion: Diffusion fastest when: Large surface area Short diffusion distance Respiratory surfaces vary by animal and can include the skin, gills, tracheae, and lungs

Lungs

Gas exchange takes place in alveoli, air sacs at the tips of bronchioles Oxygen diffuses through the moist film of the epithelium and into capillaries Carbon dioxide diffuses from the capillaries across the epithelium and into the air space Alveoli lack cilia and are susceptible to contamination Secretions called surfactants coat the surface of the alveoli Preterm babies lack surfactant and are vulnerable to respiratory distress syndrome; treatment is provided by artificial surfactants

Gills in Aquatic Animals

Gills are outfoldings of the body that create a large surface area for gas exchange Ventilation moves the respiratory medium over the respiratory surface different morphologies and distribution of gills are present, but fxn remains the same

A drop in blood pH causes an increase in heart rate. What is the function of this control mechanism?

Increased heart rate increases the rate at which CO2CO2-rich blood is delivered to the lungs, where CO2CO2 is removed.

Close Association of Lymphatic Vessels and Blood Capillaries

Lymph: fluid lost by capillaries The lymphatic system returns fluid that leaks out from the capillary beds The lymphatic system drains into veins in the neck Valves in lymph vessels prevent the backflow of fluid Edema is swelling caused by disruptions in the flow of lymph Lymph nodes are organs that filter lymph and play an important role in the body's defense When the body is fighting an infection, lymph nodes become swollen and tender

How a Mammal Breathes

Mammals ventilate their lungs by negative pressure breathing, which pulls air into the lungs (diaphragm) Lung volume increases as the rib muscles and diaphragm contract Using muscle contraction diaphragm to actively expand the thoracic cavity, mammals lower air pressure in their lungs below that of the air outside their body. Because gas flows from a region of higher pressure to a region of lower pressure, the lowered air pressure in the lungs causes air to rush through the nostrils and mouth and down the breathing tubes to the alveoli.

capillaries

Microscopic network vessel through which exchanges take place between the blood and cells of the body capillary beds are the sites of chemical exchange between the blood and interstitial fluid

facilitated diffusion

Movement of specific Polar molecules across cell membranes through protein channels or carriers

Gill capillaries

O2 from water moves (diffuses) into blood, CO2 will diffuse into water diameter is so small it decreases BP (a negative to Single Circulation)

Given that capillaries lack smooth muscle, how is blood flow in capillary beds altered?

One mechanism is constriction or dilation of the arterioles that supply capillary beds. A second mechanism involves precapillary sphincters, rings of smooth muscle located at the entrance to capillary beds The signals regulating blood flow by these mechanisms include nerve impulses, hormones traveling throughout the bloodstream, and chemicals produced locally. For example, the chemical histamine released by cells at a wound site causes vasodilation. The result is increased blood flow and increased access of disease-fighting white blood cells to invading microorganisms.

vena cava

One of two large vessels (superior and inferior) that return deoxygenated blood to the right atrium of the heart.

Carbon Dioxide Transport

Only about 7% of the CO2CO2 released by respiring cells is transported in solution in blood plasma. The rest diffuses from plasma into erythrocytes and reacts with water (assisted by the enzyme carbonic anhydrase), forming H2CO3H2CO3. The H2CO3H2CO3 readily dissociates into H+H+ and HCO3−HCO3−. Most H+ binds to hemoglobin and other proteins, minimizing change in blood pH. Most HCO3−HCO3− diffuses out of the erythrocytes and is transported to the lungs in the plasma. The remaining HCO3−HCO3−, representing about 5% of the CO2CO2, binds to hemoglobin and is transported in erythrocytes. When blood flows through the lungs, the relative partial pressures of CO2CO2 favor the net diffusion of CO2CO2 out of the blood. As CO2CO2 diffuses into alveoli, the amount of CO2CO2 in the blood decreases. This decrease shifts the chemical equilibrium in favor of the conversion of HCO3−HCO3− to CO2CO2, enabling further net diffusion of CO2CO2 into alveoli. Overall, the PCO2PCO2 gradient is sufficient to drive about a 15% reduction in PCO2PCO2 during passage of blood through the lungs.

body capillaries

Oxygenated to Deoxygenated Oxygenated blood from the lungs is pumped into the body to be used and becomes deoxygenated blood. O2 from blood moves to tissue, and CO2 from tissue move to blood.

How a Bird Breathes

Passage of air through the entire system of lungs and (9) air sacs requires two cycles of inhalation and exhalation Ventilation in birds is highly efficient--unidirectional air flow (necessary for flight) Birds have air sacs that function as bellows that keep air flowing through the lungs Air passes through the lungs in one direction only Within the lungs, tiny channels called parabronchi serve as the sites of gas exchange. Passage of air through the entire system—air sacs and lungs—requires two cycles of inhalation and exhalation incoming fresh air does not mix with air that has already carried out gas exchange, maximizing the partial pressure difference with blood flowing through the lungs.

diastole

Relaxation of the heart

Adaptations for gas exchange include pigments that bind and transport gases

Respiratory pigments, proteins that transport oxygen, greatly increase the amount of oxygen that blood can carry due to the high metabolic demands of many animals necessitate the exchange of large quantities of O2O2 and CO2CO2. Arthropods and many molluscs have hemocyanin, with copper as the oxygen-binding component Most vertebrates and some invertebrates use hemoglobin The metabolic demands of many organisms require that the blood transport large quantities of O2 and CO2

Direct contact with environment

Some cnidarians and flatworms have elaborate gastrovascular cavities that function in both digestion and distribution of substances throughout the body The body wall that encloses the gastrovascular cavity is only two cells thick Flatworms have a gastrovascular cavity and a flat body that minimizes diffusion distances

Evolutionary Variation in Double Circulation

Some vertebrates with double circulation are intermittent breathers. For example, amphibians and many reptiles fill their lungs with air periodically, passing long periods either without gas exchange or by relying on another gas exchange tissue, typically the skin. A variety of adaptations found among intermittent breathers enable their circulatory systems to temporarily bypass the lungs in part or in whole: Frogs and other amphibians have a heart with three chambers—two atria and one ventricle (see Figure 42.4b). A ridge within the ventricle diverts most (about 90%) of the oxygen-rich blood from the left atrium into the systemic circuit and most of the oxygen-poor blood from the right atrium into the pulmocutaneous circuit. When a frog is underwater, it takes advantage of the incomplete division of the ventricle, largely shutting off blood flow to its temporarily ineffective lungs. Blood flow continues to the skin, which acts as the sole site of gas exchange while the frog is submerged. In the three-chambered heart of turtles, snakes, and lizards, an incomplete septum partially divides the single ventricle into right and left chambers. Two major arteries, called aortas, lead to the systemic circulation. As with amphibians, the circulatory system enables control of the relative amount of blood flowing to the lungs and the rest of the body. In alligators, caimans, and other crocodilians, the ventricles are divided by a complete septum, but the pulmonary and systemic circuits connect where the arteries exit the heart. This connection allows arterial valves to shunt blood flow away from the lungs temporarily, such as when the animal is underwater. Double circulation in birds and mammals, which for the most part breathe continuously, differs from double circulation in other vertebrates. As shown for a panda in Figure 42.4c, the heart has two atria and two completely divided ventricles. The left side of the heart receives and pumps only oxygen-rich blood, while the right side receives and pumps only oxygen-poor blood. Unlike amphibians and many reptiles, birds and mammals cannot vary blood flow to the lungs without varying blood flow throughout the body in parallel.

How does the Bohr shift help deliver O2O2 to very active tissues?

The Bohr shift causes hemoglobin to release more O2O2 at a lower pH, such as found in the vicinity of tissues with high rates of cellular respiration and CO2CO2 release.

A doctor might give bicarbonate (HCO3−)(HCO3-) to a patient who is breathing very rapidly. What is the doctor assuming about the patient's blood chemistry?

The doctor is assuming that the rapid breathing is the body's response to low blood pH. Metabolic acidosis, the lowering of blood pH as a result of metabolism, can have many causes, including complications of certain types of diabetes, shock (extremely low blood pressure), and poisoning.

Fluid Exchange between Capillaries and the Interstitial Fluid

The exchange of substances between the blood and interstitial fluid takes place across the thin endothelial walls of the capillaries Blood pressure tends to drive fluid out of capillaries(hydrostatic pressure), and blood proteins tend to pull fluid back (osmotic pressure) These proteins are responsible for much of the blood's osmotic pressure On average, there is a net loss of fluid from capillaries

The cardiac cycle

The heart contracts and relaxes in a rhythmic cycle Systole: the contraction, or pumping, phase Diastole: the relaxation, or filling, phase

The Mammalian Cardiovascular System: An Overview

The human heart is about the size of a clenched fist and consists mainly of cardiac muscle Four valves prevent backflow of blood in the heart The two atria have relatively thin walls and serve as collection chambers for blood returning to the heart The ventricles have thicker walls and contract much more forcefully Contraction of 1 the right ventricle pumps blood to the lungs via 2 the pulmonary arteries. As the blood flows through 3 capillary beds in the left and right lungs, it loads O2O2 and unloads CO2CO2. Oxygen-rich blood returns from the lungs via the pulmonary veins to 4 the left atrium of the heart. Next, the oxygen-rich blood flows into 5 the heart's left ventricle, which pumps the oxygen-rich blood out to body tissues through the systemic circuit. Blood leaves the left ventricle via 6 the aorta, which conveys blood to arteries leading throughout the body. The first branches leading from the aorta are the coronary arteries (not shown), which supply blood to the heart muscle itself. Then branches lead to 7 capillary beds in the head and arms (forelimbs). The aorta then descends into the abdomen, supplying oxygen-rich blood to arteries leading to 8 capillary beds in the abdominal organs and legs (hind limbs). Within the capillaries, there is a net diffusion of O2O2 from the blood to the tissues and of CO2CO2 (produced by cellular respiration) into the blood. Capillaries rejoin, forming venules, which convey blood to veins. Oxygen-poor blood from the head, neck, and forelimbs is channeled into a large vein, 9 the superior vena cava. Another large vein, 10 the inferior vena cava, drains blood from the trunk and hind limbs. The two venae cavae empty their blood into 11 the right atrium, from which the oxygen-poor blood flows into the right ventricle.

Why do the circulatory systems of land vertebrates have separate circuits to the lungs and to the rest of the body?

The large decrease in blood pressure as blood moves through the lungs may prevent efficient circulation through the rest of the body. The changes in blood pressure as blood moves through the lungs of land-dwelling vertebrates make it necessary to have separate circuits to the lungs and the rest of the body.

Regulation of the pacemaker

The pacemaker is regulated by two portions of the nervous system: Sympathetic division: speeds up the pacemaker Parasympathetic division: slows down the pacemaker The pacemaker is also regulated by hormones and temperature (epinephrine) regulated by endocrine and nervous

SA node

The pacemaker of the heart, located in the right atrium.

why is there a net loss of fluid from the capillaries?

The primary force driving fluid transport between the capillaries and tissues is hydrostatic pressure, which can be defined as the pressure of any fluid enclosed in a space. Blood hydrostatic pressure is the force exerted by the blood confined within blood vessels or heart chambers. Even more specifically, the pressure exerted by blood against the wall of a capillary is called capillary hydrostatic pressure (CHP), and is the same as capillary blood pressure. CHP is the force that drives fluid out of capillaries and into the tissues As fluid exits a capillary and moves into tissues, the hydrostatic pressure in the interstitial fluid correspondingly rises. This opposing hydrostatic pressure is called the interstitial fluid hydrostatic pressure (IFHP). Generally, the CHP originating from the arterial pathways is considerably higher than the IFHP, because lymphatic vessels are continually absorbing excess fluid from the tissues. Thus, fluid generally moves out of the capillary and into the interstitial fluid. This process is called filtration. The net filtration pressure (NFP) represents the interaction of the hydrostatic and osmotic pressures, driving fluid out of the capillary. It is equal to the difference between the CHP and the BCOP. Since filtration is, by definition, the movement of fluid out of the capillary, when reabsorption is occurring, the NFP is a negative number. NFP changes at different points in a capillary bed (Figure 1). Close to the arterial end of the capillary, it is approximately 10 mm Hg, because the CHP of 35 mm Hg minus the BCOP of 25 mm Hg equals 10 mm Hg. Recall that the hydrostatic and osmotic pressures of the interstitial fluid are essentially negligible. Thus, the NFP of 10 mm Hg drives a net movement of fluid out of the capillary at the arterial end. At approximately the middle of the capillary, the CHP is about the same as the BCOP of 25 mm Hg, so the NFP drops to zero. At this point, there is no net change of volume: Fluid moves out of the capillary at the same rate as it moves into the capillary. Near the venous end of the capillary, the CHP has dwindled to about 18 mm Hg due to loss of fluid. Because the BCOP remains steady at 25 mm Hg, water is drawn into the capillary, that is, reabsorption occurs. Another way of expressing this is to say that at the venous end of the capillary, there is an NFP of −7 mm Hg. Since overall CHP is higher than BCOP, it is inevitable that more net fluid will exit the capillary through filtration at the arterial end than enters through reabsorption at the venous end. Considering all capillaries over the course of a day, this can be quite a substantial amount of fluid: Approximately 24 liters per day are filtered, whereas 20.4 liters are reabsorbed. This excess fluid is picked up by capillaries of the lymphatic system. These extremely thin-walled vessels have copious numbers of valves that ensure unidirectional flow through ever-larger lymphatic vessels that eventually drain into the subclavian veins in the neck. An important function of the lymphatic system is to return the fluid (lymph) to the blood. Lymph may be thought of as recycled blood plasma. (Seek additional content for more detail on the lymphatic system.)

The Control of Heart Rhythm

The sinoatrial (SA) node, or pacemaker, sets the rate and timing at which cardiac muscle cells contract Impulses that travel during the cardiac cycle can be recorded as an electrocardiogram (ECG or EKG) Some cardiac muscle cells are autorhythmic, meaning they contract without any signal from the nervous system The sinoatrial (SA) node, or pacemaker, sets the rate and timing at which cardiac muscle cells contract Impulses that travel during the cardiac cycle can be recorded as an electrocardiogram (ECG or EKG) Impulses from the SA node travel to the atrioventricular (AV) node Here, the impulses are delayed and then travel to the Purkinje fibers that make the ventricles contract

Organization of Vertebrate Circulatory Systems

The three main types of blood vessels are arteries, veins, and capillaries Humans and other vertebrates have a closed circulatory system called the cardiovascular system Blood flow is one way in these vessels Arteries and veins are distinguished by the direction of blood flow, not by oxygen content Vertebrate hearts contain two or more chambers Blood enters through an atria and is pumped out through ventricles Blood circulates to and from the heart through an amazingly extensive network of vessels: The total length of blood vessels in an average human adult is twice Earth's circumference at the equator!

Blood Flow in Capillary Beds

Two mechanisms regulate distribution of blood in capillary beds -Constriction or dilation of arterioles that supply capillary beds -Precapillary sphincters that control flow of blood between arterioles and venules -Blood flow is regulated by nerve impulses, hormones, and other chemicals Blood flows through only 5-10% of the body's capillaries at any given time Capillaries in major organs are usually filled to capacity Blood supply varies in many other sites

Regulation of Blood Pressure

Vasoconstriction: the contraction of smooth muscle in arteriole walls; it increases blood pressure Vasodilation: the relaxation of smooth muscles in the arterioles; it causes blood pressure to fall Nitric oxide (NO) is a major inducer of vasodilation The peptide endothelin is a potent inducer of vasoconstriction Vasoconstriction and vasodilation are often coupled to changes in cardiac output that affect blood pressure Blood pressure is generally measured for an artery in the arm at the same height as the heart Fainting is caused by inadequate blood flow to the head Animals with long necks require a very high systolic pressure to pump blood a great distance against gravity Because blood pressure is low in veins, one-way valves in veins prevent backflow of blood Return of blood is also enhanced by contraction of smooth muscle in venule walls and skeletal muscle contraction

cooperativity of hemoglobin

When O2O2 binds to one subunit, the others change shape slightly, increasing affinity for O2O2. When four O2O2 molecules are bound and one subunit unloads its O2O2, the other three subunits more readily unload O2O2, as an associated change in shape lowers their affinity for O2O2. Hemoglobin is especially efficient at delivering O2O2 to tissues actively consuming O2O2. However, this increased efficiency results not from O2O2 consumption, but rather from CO2CO2 production. As tissues consume O2O2 in cell respiration, they also produce CO2CO2. As we have seen, CO2CO2 reacts with water, forming carbonic acid, which lowers the pH of its surroundings. Low pH decreases the affinity of hemoglobin for O2O2, an effect called the Bohr shift (Figure 42.31b). Thus, where CO2CO2 production is greater, hemoglobin releases more O2O2, which can then be used to support more cellular respiration. Hemoglobin also assists in buffering the blood—that is, preventing harmful changes in pH. In addition, it has a minor role in CO2CO2 transport, the topic we'll explore next.

negative pressure breathing

a breathing system in which air is pulled into the lungs Using muscle contraction to actively expand the thoracic cavity, mammals lower air pressure in their lungs below that of the air outside their body. Because gas flows from a region of higher pressure to a region of lower pressure, the lowered air pressure in the lungs causes air to rush through the nostrils and mouth and down the breathing tubes to the alveoli.

Single Circulation

a circulatory system consisting of a single pump and circuit, in which blood passes from the sites of gas exchange to the rest of the body before returning to the heart e.g. Bony fishes, rays, and sharks have single circulation with a two-chambered heart -- Atrium & Ventricle In single circulation, blood leaving the heart passes through two capillary beds before returning to the heart When blood flows through a capillary bed, blood pressure drops substantially, The drop in blood pressure in the gills limits the rate of blood flow in the rest of the animal's body. As the animal swims, however, the contraction and relaxation of its muscles help accelerate the relatively sluggish pace of circulation.

Bohr Effect

a decrease in the amount of oxygen associated with hemoglobin and other respiratory compounds in response to a lowered blood pH resulting from an increased concentration of carbon dioxide in the blood.

Breathing ventilates the lungs

amphibians also ventilate. birds, mammals

heart murmur

an abnormal sound from the heart produced by defects in the chambers or valves

sinoatrial (SA) node

autorhythmic; they can contract and relax repeatedly without any signal from the nervous system. a group of clustered autorhythmic cells located in the wall of the right atrium, near where the superior vena cava enters the heart pacemaker-- sets the rate and timing at which all cardiac muscle cells contract; produces electrical impulses much like those produced by nerve cells. Because cardiac muscle cells are electrically coupled through gap junctions (see Figure 6.30), impulses from the SA node spread rapidly within heart tissue. These impulses generate currents that can be measured when they reach the skin via body fluids.

respiratory proteins

bind oxygen at high concentrations; release oxygen at low concentrations; hemocyanin, hemoglobin,

Closed Circulatory Systems

blood is confined to vessels and is distinct from the interstitial fluid e.g. Annelids, cephalopods, and vertebrates have closed circulatory systems One or more hearts pump blood into large vessels that branch into smaller ones that infiltrate the tissues and organs. Chemical exchange occurs between the blood and the interstitial fluid, as well as between the interstitial fluid and body cells. Annelids (including earthworms), cephalopods (including squids and octopuses), and all vertebrates have closed circulatory systems.

surfactants

compounds that lower the surface tension of water

Plasma

dissolved is: ions and proteins that, together with the blood cells, function in osmotic regulation, transport, and defense. Inorganic salts in the form of dissolved ions are an essential component of the blood. Some buffer the blood, while others help maintaining osmotic balance. In addition, the concentration of ions in plasma directly affects the composition of the interstitial fluid, where many of these ions have a vital role in muscle and nerve activity. Serving all of these functions necessitates keeping plasma electrolytes within narrow concentration ranges. Like dissolved ions, plasma proteins such as albumins act as buffers against pH changes and help maintain the osmotic balance between blood and interstitial fluid. Certain plasma proteins have additional functions. Immunoglobulins, or antibodies, combat viruses and other foreign agents that invade the body (see Figure 43.10). Apolipoproteins escort lipids, which are insoluble in water and can travel in blood only when bound to proteins. Additional plasma proteins include the fibrinogens, which are clotting factors that help plug leaks when blood vessels are injured. (The term serum refers to blood plasma from which these clotting factors have been removed.) Plasma also contains many other substances in transit, including nutrients, metabolic wastes, respiratory gases, and hormones. Plasma has a much higher protein concentration than interstitial fluid, although the two fluids are otherwise similar. (Capillary walls, remember, are not very permeable to proteins.)

Double Circulation

e.g. Amphibians, reptiles, and mammals have double circulation -Oxygen-poor and oxygen-rich blood are pumped separately from right and left sides of heart -Oxygen-rich blood delivers oxygen through systemic circuit -Maintains higher blood pressure in organs than single circulation ***the pumps for the two circuits are combined into a single organ, the heart. Having both pumps within a single heart simplifies coordination of the pumping cycles. -provides a vigorous flow of blood to the brain, muscles, and other organs because the heart repressurizes the blood after it passes through the capillary beds of the lungs or skin. (Indeed, blood pressure is often much higher in the systemic circuit than in the gas exchange circuit.) By contrast, in single circulation the blood flows under reduced pressure directly from the gas exchange organs to other organs.

ECG/EKG (electrocardiogram)

electrocardiogram - is the record of the electricity of the heart. electrodes placed on the skin record the currents, thus measuring electrical activity of the heart. The graph of current against time has a shape that represents the stages in the cardiac cycle

The Structure of Blood Vessels

epithelium, smooth muscle, connective tissue tunica intima, tunica media, tunica externa, basal lamina All blood vessels contain a central lumen lined with an epithelial layer that lines blood vessels This endothelium is smooth and minimizes resistance Capillaries are only slightly wider than a redblood cell 7 billion capillaries (humans) Capillaries have thin walls, the endothelium plus its basal lamina, to facilitate the exchange of materials Arteries and veins have an endothelium, smooth muscle, and connective tissue Arteries have thick, elastic walls to accommodate the high pressure of blood pumped from the heart In the thinner-walled veins, blood flows back to the heart mainly as a result of muscle action Unlike arteries, veins contain valves to maintain unidirectional blood flow veins have valves to ensure unidirectional flow (stop backflow)

Circulatory systems link

exchange surfaces with cells throughout the body (O2/CO2) -- every cell in the body Small molecules can move between cells and their surroundings by diffusion Options: 1.Direct contact with environment 2.Fluid-filled circulatory system (Diffusion is only efficient over small distances because the time it takes to diffuse is proportional to the square of the distance) ---- high to low concentration through semipermeable membrane In some animals, many or all cells are in direct contact with the environment In most animals, cells exchange materials with the environment via a fluid-filled circulatory system

diaphragm

expands thoracic cavity, compresses abdominopelvic cavity (NEGATIVE PRESSURE BREATHING)

path of blood

heart, arteries, arterioles, capillaries, venules, veins, heart

The Mammalian Respiratory System

in descending order: Nasal cavity pharynx larynx trachea bronchi bronchioles alveoli A system of branching ducts conveys air to the lungs Air inhaled through the nostrils is filtered, warmed, humidified, and sampled for odors The pharynx directs air to the lungs and food to the stomach Swallowing moves the larynx upward and tips the epiglottis over the glottis in the pharynx to prevent food from entering the trachea, or windpipe [The cartilage that reinforces the walls of both the larynx and the trachea keeps this part of the airway open.] Air passes through the pharynx, larynx, trachea, bronchi, and bronchioles to the alveoli, where gas exchange occurs Exhaled air passes over the vocal cords in the larynx to create sounds Cilia and mucus line the epithelium of the air ducts and move particles up to the pharynx This "mucus escalator" cleans the respiratory system and allows particles to be swallowed into the esophagus

Tracheal System in Insects

is highly branched and approaches almost every cell to effect gas exchange The tracheal system of insects consists of a network of branching tubes throughout the body -Tracheal tubes supply O2 to cells -The respiratory and circulatory systems are separate

Rate of Diffusion

is proportional to the surface area across which it occurs and inversely proportional to the square of the distance through which molecules must move. In other words, gas exchange is fast when the area for diffusion is large and the path for diffusion is short. As a result, respiratory surfaces tend to be large and thin.

Cardiac Output (CO)

measurement of the amount of blood ejected per minute from either ventricle of the heart Two factors determine cardiac output: the rate of contraction, or heart rate (number of beats per minute), and the stroke volume, the amount of blood pumped by a ventricle in a single contraction. The average stroke volume in humans is about 70 mL. Multiplying this stroke volume by a resting heart rate of 72 beats per minute yields a cardiac output of 5 L/min—about equal to the total volume of blood in the human body. During heavy exercise, the increased demand for O2O2 is met by an increase in cardiac output that can be as much as fivefold.

Blood Flow in Veins

most is upward, from the lower body back to the heart against gravity Because blood pressure is low in veins, one-way valves in veins prevent backflow of blood Return of blood is also enhanced by contraction of smooth muscle in venule walls and skeletal muscle contraction capillaries, venules, veins, heart in lungs and at tissue [Skeletal muscle contraction squeezes and constricts veins. Flaps of tissue within the veins act as one-way valves that keep blood moving only toward the heart. If you sit or stand too long, the lack of muscular activity may cause your feet to swell as blood pools in your veins.]

simple diffusion

movement of a (non-polar) solute from an area of high concentration to an area of low concentration (through phospholipids)

ventilation

movement of air in and out of the lungs; moves the respiratory medium over the respiratory surface

osmotic pressure

pressure that must be applied to prevent osmotic movement across a selectively permeable membrane pressure produced by differences in solute concentration across a membrane

respiratory pigments

proteins that transport oxygen, greatly increase the amount of oxygen that blood can carry

semilunar valves

pulmonary and aortic valves located between the right ventricle and the pulmonary artery and between the left ventricle and the aorta are located at the two exits of the heart: where the pulmonary artery leaves the right ventricle and where the aorta leaves the left ventricle. These valves are pushed open by the pressure generated during contraction of the ventricles. When the ventricles relax, blood pressure built up in the pulmonary artery and aorta closes the semilunar valves and prevents significant backflow.

Left Side of Heart (Double Circulation)

pumps blood high in O2 to tissues Systemic Circuit

AV node (atrioventricular node)

region of the heart between the right atrium and right ventricle from which electrical impulses spread to the ventricles during a heartbeat

Diffusion is only efficient/rapid over _________ distances. _________ molecules ONLY can diffiuse random __________ motion

short small thermal

Venules

small vessels that gather blood from the capillaries into the veins converge into veins and return blood from capillaries to the heart capillaries converge into ___________

arterioles

small vessels that receive blood from the arteries

right atrium receives blood from

superior vena cava, inferior vena cava, coronary sinus

pulmonary circuit

system of blood vessels that carries blood between the heart and the lungs the right side of the heart pumps oxygen-poor blood to the capillary beds of the gas exchange tissues(lungs), where there is a net movement of O2O2 into the blood and of CO2CO2 out of the blood.

partial pressure

the contribution each gas in a mixture of gases makes to the total pressure Determining partial pressures enables us to predict the net movement of a gas at an exchange surface: A gas always undergoes net diffusion from a region of higher partial pressure to a region of lower partial pressure

countercurrent exchange

the opposite flow of adjacent fluids that maximizes transfer rates; for example, blood in the gills flows in the opposite direction in which water passes over the gills, maximizing oxygen uptake and carbon dioxide loss. *maintains a gradient of partial pressures over entire capillary PO2 of water is always higher to drive the diffusion and prevent equilibrium

Gas exchange

the process of obtaining oxygen from the environment and releasing carbon dioxide uptake of O2 from environment and discharge of CO2 to environment

Ventricles

the two lower chambers of the heart, and they pump blood out to the lungs and body.

The critical exchange of substances between the blood and interstitial fluid takes place across the _____ _________ _______ of the capillaries How does exchange occur?

thin endothelial walls of the capillaries. A few macromolecules are carried across the endothelium in vesicles that form on one side by endocytosis and release their contents on the opposite side by exocytosis. Small molecules, such as O2O2 and CO2CO2, simply diffuse across the endothelial cells or, in some tissues, through microscopic pores in the capillary wall. These openings also provide the route for transport of small solutes such as sugars, salts, and urea, as well as for bulk flow of fluid into tissues driven by blood pressure within the capillary.

basal lamina

thin extracellular layer that lies underneath epithelial cells and separates them from other tissues

alveoli

tiny sacs of lung tissue specialized for the movement of gases between air and blood 50X SA from alveoli than our bodies

The trachea branches into

two bronchi (singular, bronchus), one leading to each lung. Within the lung, the bronchi branch repeatedly into finer and finer tubes called bronchioles. The entire system of air ducts has the appearance of an inverted tree, the trunk being the trachea. The epithelium lining the major branches of this respiratory tree is covered by cilia and a thin film of mucus. The mucus traps dust, pollen, and other particulate contaminants, and the beating cilia move the mucus upward to the pharynx, where it can be swallowed into the esophagus. This process, sometimes referred to as the "mucus escalator," plays a crucial role in cleansing the respiratory system.

portal veins

veins that begin in a primary capillary network, extend some distance and end in a secondary capillary network without a pumping mechanism, such as the heart, between. carry blood between pairs of capillary beds