Please enable JavaScript.
Coggle requires JavaScript to display documents.
CIRCULATION AND OSMOREGULATION (42.5 Gas exchange occurs across…
CIRCULATION AND OSMOREGULATION
42.1 Circulatory systems link exchange surfaces with cells throughout the body
diffusion: random thermal motion
difference in concentration, diffusion results in net movement, although slow
2 basic adaptations that permit effective exchange for all animal's cells
simple body plan that places many or all cells in direct contact with environment
characteristic of cnidarians and flatworms
animals lacking simple body plan and circulatory system
exchange with environment and body tissues occur over short distances
Gastrovascular Cavities
functions in the distribution of substances throughout the body
opening at one end connect cavity to surrounding water
in cnidarians: fluid bathes both inner and outer tissue layers
facilitates exchange of gases and cellular waste
cells lining cavity have direct access to nutrients released by digestion
planarians/flatworms
combination of gastrovascular cavity and flat body
flat body optimizes exchange by
Open and Closed Circulatory Systems
circulatory system = 3 basic components
circulatory fluid
set of interconnecting vessels
heart
muscular pump
powers circulation by using metabolic energy to elevate circulatory fluid's hydrostatic pressure
hydrostatic pressure: pressure fluid exerts on surrounding vessels
fluid flows through vessels and back to heart
functionally connects aqueous environment of body cells to organs that exchange gases, absorb nutrients, and dispose of wastes
open circulatory system
hemolymph: circulatory fluid (also interstitial fluid) that bathes body cells
contraction of heart pumps hemolymph through circulatory vessels into interconnected sinuses
sinus: space surrounding organs
within sinuses, hemolymph and body cells exchange gases and other chemicals
relaxation of heart draws hemolymph back in through pores
pores have valves that close when heart contracts
advantages
lower hydrostatic pressures allow less energy usage
closed circulatory system
blood: circulatory fluid confined to vessels and distinct from interstitial fluid
one or more hearts pump blood into large vessels that branch into smaller ones that infiltrate the tissues and organs
chemical exchange occurs between blood and interstitial fluid and body cells
all vertebrates have closed circulatory systems
advantages
blood pressure high enough to enable effective delivery of O2 and nutrients in larger and more active animals
well suited to regulating distribution of blood to other organs
Organization of Vertebrate Circulatory Systems
cardiovascular system
often used to describe the heart and blood vessels in vertebrates
blood circulates to and from the heart through extensive network of vessels
3 main types of blood vessels
within each type, blood flows in only one direction
arteries
carry blood from heart to organs throughout the body
branch into arterioles within organs
capillaries
microscopic vessels with very thin, porous walls
blood conveyed to capillaries by arterioles
capillary beds
networks of capillaries
infiltrate tissues, passing within a few cell diameters of every cell
across walls, dissolved gases and other chemicals exchange by diffusion between blood and interstitial fluid
converge into venules at "downstream" end
veins
converged venules
vessels that carry blood back to the heart
arteries and veins distinguished by direction in which they carry blood, not by O2 content
arteries carry blood away from heart toward capillaries
veins return blood toward heart from capillaries
exceptions
portal veins: carry blood between pairs of capillary beds
hearts of all vertebrates contain 2 or more muscular chambers
atrium (pl. atria)
chamber that receives blood entering the heart
ventricle
chamber responsible for bumping blood out of the heart
Single Circulation
blood travels through the body and returns to its starting point in a single circuit (loop
sharks, rays, bony fishes
hearts consist of 2 chambers
blood entering the heart collects in atrium before transfer to the ventricle
contraction of ventricle pumps blood to capillary bed in gills
net diffusion of O2 into blood and of CO2 out of the blood
as blood leaves gills, capillaries converge into a vessel that carries oxygen-rich blood to capillary beds throughout the body
blood enters veins and returns to the heart following gas exchange in capillary beds
blood that leaves heart passes through 2 capillary beds before returning to heart
blood pressure drops
drop in blood pressure in gills limits blood flow in rest of animal's body
contraction and relaxation of muscles help accelerate circulation as the animal swims
Double Circulation
two circuits of blood flow
pulmonary circuit
right side of the heart pumps oxygen-poor blood to capillary beds of gas exchange tissues
net movement of O2 into the blood of CO2 out of the blood
gas exchange takes place in the lungs
pulmocutaneous circuit
for many amphibians
gas exchange takes place in capillaries in both the lungs and the skin
systemic circuit
begins with left side of heart pumping oxygen-enriched blood from gas exchange tissues to capillary beds in organs and tissues through the body
following exchange of O2, CO2, waste products, and nutrients, oxygen-poor blood returns to heart
amphibians, reptiles, and mammals
pumps for two circults combined ito heart
simplifies coordination of the pumping cycles
provides flow of blood to brain, muscles, and other organs
heart repressurizes blood after it passes through capillary beds of lungs or skin
42.2 Coordinated cycles of heart contraction drive double circulation in mammals
Mammalian Circulation
beginning with pulmonary circuit
1.) contraction of right ventricle pumps bloods to lungs via
2.) the pulmonary arteries. As blood flows through
3.) capillary beds in left and right lungs, it loads O2 and unloads CO2
oxygen-rich blood returns to lungs via pulmonary veins
4.) the left atrium of the heart; oxygen-rich blood flows into
5.) the heart's left ventricle
pumps oxygen-rich blood out to body tissues through the systemic circuit
6.) blood leaves left ventricle via aorta
conveys blood to arteries leading throughout the body
coronary arteries
first branches leading from aorta
supplies blood to heart muscle
8.) capillary beds in hind limbs (abdominal organs and legs)
net diffusion of O2 from the blood to the tissues and of CO2 (produced by cellular respiration) into the blood
capillaries rejoin, forming venules
convey blood to veins
oxygen-poor blood from head, neck, and forelimbs channeled into
9.) superior vena cava (large vein)
10.) inferior vena cava: drains blood from trunk and hind limbs
10.) venae cavae empty blood into right atrium
oxygen-poor blood flows into right ventricle
7.) branches lead to capillary beds in head and arms (forelimbs)
aorta descends into abdomen, supplying oxygen-rich blood to arteries leading to
The Mammalian Heart:
A Closer Look
located behind sternum (breastbone)
size of a clenched fist
consists mostly of cardiac muscle
atria
relatively thin walls
serve as collection chambers for blood returning to the heart from the lungs or other body tissues
must of blood that enters atria flows into ventricles while all four heart chambers are relaxed
remainder transferred by contraction of atria before ventricles begin to contract
ventricles
thicker walls and contract more forcefully than atria
left ventricle pumps blood throughout the body via systemic circuit
left ventricle pumps same amount of blood as right ventricle during each contraction, despite the greater force
cardiac cycle
one sequence of pumping and filling of blood in the heart
contracts --> pumps blood
systole
relaxes --> chambers fill with blood
diastole
cardiac output
volume of blood each ventricle pumps per minute
2 factors determine cardiac output
heart rate
rate of contraction
number of beats per minute
stroke volume
amount of blood pumped by a ventricle in a single contraction
average in humans is about 70mL
four valves in heart prevent back flow and keep blood moving in correct direction
made of flaps of connective tissue
valves open when pushed from one side and close when pushed from the other
atrioventricular (AV) valve
lies between each atrium ventricle
anchored by strong fibers that prevent them from turning inside out during ventricular systole
pressure generated by contraction of ventricles close AV valves
keeps blood from flowing back into atria
semilunar valves
located at two exits of the heart
where pulmonary artery leaves right ventricle
where aorta leaves the left ventricle
valves pushed open by pressure generated during contraction of the ventricles
when ventricles relax, blood pressure in pulmonary artery and aorta closes semilunar valves
prevents backflow
heart murmur
abnormal sound caused by blood squiring backward through a defective valve
Maintaining the Heart's Rhythmic Beat
sinoatrial (SA) node
"pacemaker"
sets rate and timing at which all cardiac muscle cells contract
produces electrical impulses that spread rapidly within heart tissues through gap junctions
impulses generate currents that can be measured when they reach skin via body fluids
electrocardiogram
ECG/EKG
electrodes placed on skin record electric currents, measuring activity of heart
atrioventricular (AV) node
relay point formed by autorhythmic cells in the wall between left and right atria
impulses delayed for about 0.1 seconds before spreading to heart apex
allow atria to empty completely before ventricles contract
sympathetic and parasympathetic divisions largely responsible for regulating pacemaker function of SA node
42.3 Patterns of blood pressure and flow reflect the structure and arrangement of blood vessels
Blood Vessel Structure and Function
all blood vessels contain central lumen (cavity) lined with an endothelium
single layer of flattened epithelial cells
minimizes resistance to fluid flow due to smooth layer
surrounded by tissue layers that differ among capillaries, arteries, and veins
capillaries
smallest blood vessels
diameter slightly greater than that of a red blood cell
thin walls that consist of endothelium and basal lamina
surrounding extracellular layer
exchange of substances between blood and interstitial fluid occurs because walls thin enough to permit this exchange
arteries and veins have walls that consist of two layers of tissue surrounding endothelium
outer layer formed by connective tissue that contains
elastic fibers: allow vessel to stretch and recoil
collagen: provide strength
layer next to endothelium contains smooth muscle and more elastic fibers
arterial walls thick, strong, and elastic
can accommodate blood pumped at high pressure by the heart
essential role in maintaining blood pressure and flow to capillaries
smooth muscles in walls of arteries and arterioles help regulate path fo blood flow
signals from nervous system and circulating hormones act on smooth muscle
veins do not require thick walls
convey blood back to heart at lower pressure
contain valves that maintain unidirectional flow of blood
Blood Flow Velocity
blood slows as it moves from arteries to arterioles to capillaries
number of capillaries responsible for the slowing down of flow
total cross-sectional area much greater in capillary beds than any other part of circulatory system
Blood Pressure
contraction of heart ventricle generates blood pressure
part of the force directed lengthwise in artery causes blood to flow away from heart (site of highest pressure)
part of force exerted sideways stretches wall of artery
Changes in Blood Pressure During the Cardiac Cycle
arterial blood pressure highest when heart contracts during ventricular systole
systolic pressure
pulse: rhythmic bulging of artery walls with each heartbeat
pressure surge partly due to narrow openings of arterioles impeding exit of blood from arteries
when heart contracts, blood enters arteries faster than it can leave
diastole
elastic walls of arteries snap back
diastolic pressure: lower but still substantial blood pressure when ventricles are relaxed
Regulation of Blood Pressure
vasocontriction
arterioles narrow due to smooth muscles in arteriole walls contracting
increases blood pressure upstream in arteries
endothelin
peptide
most potent inducer
vasodilation
smooth muscles relax
increase in diamter causes blood pressure in arteries to fall
nitric oxide (NO) major inducer
vasoconstriction and vasodilation often coupled to changes in cardiac output that also affect blood pressure
maintains adequate blood flow as body's demands on circulatory system change
gravity consideration for blood flow in veins, especially those in legs
Capillary Function
at any given time, only about 5-10% of body's capillaries have blood flowing through them
brain, heart, kidneys, and liver capillaries usually filled to capacity
blood flow in capillary beds altered despite lack of smooth muscle in capillaries
constriction or dilation of arterioles that supply capillary beds
precapillary sphincters
rings of smooth muscle located at entrance to capillary beds
opening and closing redirects passage of blood into particular sets of capilaries
signals regulating blood flow by these mechanisms
nerve impulses
hormones traveling through bloodstream
chemicals produced locally
exchange of substances between blood and interstitial fluid
takes place across thin endothelial walls of capillaries
a few macromolecules are carried across the endothelium in vesicles that form on one side by endocytosis and release contents on other side by exocytosis
O2 and CO2 diffuse across endothelial cells, or in some tissues, through microscopic pores in capillary wall
openings provide route for transport of small solutes like sugars, salts, adn urea
2 opposing forces control movement of fluid between capillaries and surrounding tissues
blood pressure drives fluid of of capillaries
presence of blood proteins pulls fluid back
many blood proteins too large to pass through endothelium (remain in capillaries)
dissolved proteins responsible for blood's osmotic pressure
osmotic pressure: the pressure produced by the difference in solute concentration across a membrane)
difference in osmotic pressure between blood and interstitial fluid opposes fluid movement out of capillaries
Fluid Return by the Lymphatic System
lost fluid and proteins within it are recovered and returned to the blood via the lymphatic system
fluid diffuses into system via network of tiny vessels intermingled with capillaries
lymph: recovered fluid
circulates within lymphatic system before draining into pair of large veins of cardiovascular system at base of neck
joining of lymphatic and cardiovascular systems completes recovery of fluid lost from capillaries as well as transfer of lipids from small intestine to blood
lymph vessels have valves that prevent backflow of fluid
rhythmic contractions of vessel walls help draw fluid into small lymphatic vessels
skeletal muscle contractions move lymph
edema: fluid accumulation
caused by disruptions in movement of lymph
lymph nodes
important role in body's defense
small, lymph-filtering organs
42.4 Blood components function in exchange, transport, and defense
Blood Composition and Function
Plasma
liquid matrix that suspends cells and makes up blood
dissolved ions and proteins that function in osmotic regulation, transport, and defense
together with blood cells
inorganic salts
in form of dissolved ions
essential component of blood
some buffer, others help maintain osmotic balance
concentration of ions in plasma affects composition of interstitial fluid
additional functions of certain plasma proteins
immunoglobulins
antibodies
combat viruses and other foreign agents
apolipoproteins escort lipids
fibrinogens: clotting factors that help plug leaks when blood vessels are injured
serum: blood plasma from which these clotting factors have been removed
contains many other substances in transit
nutrients
metabolic wastes
respiratory gases
hormones
higher protein concentration than interstitial fluid
Cellular Elements
erythrocytes
red blood cells
most numerous blood cells
main function: O2 transport
biconcave
thinner in center than at the edges
shape increases surface area
enhances rate of diffusion of O2 across plasma membrane
hemoglobin: iron-containing protein that transports O2
mature cells lack:
nuclei: allows for more space for hemoglobin
mitochondria
generate ATP exclusively by anaerobic metabolism
sickle-cell disease: abnormal form of hemoglobin polymerizes into aggregates
leukocytes
white blood cells
main function: fight infections
some are phagocytic (engulf and digest microorganisms and debris from body's own dead cells)
lymphocytes mount immune responses against foreign substances
found outside the circulatory system
patrolling interstitial fluid and lymphatic system
platelets
pinched-off cytoplasmic fragments of specialized bone marrow cells
serve both structural and molecular functions in blood clotting
Stem Cells and the Replacement of Cellular Elements
can reproduce indefinitely
dividing mitotically to produce one daughter cell that remains a stem cell and another that adopts a specialized function
stem cells that produce cellular elements of blood cells are located in red marrow inside bones, particularly ribs, vertebrae, sternum, and pelvis
progenitor cells
lymphoid progenitors
produce lymphocytes
myeloid progenitors
produce all other white blood cells, red blood cells, and platelets
erythropoietin (EPO) hormone synthesized and secreted by kidneys that stimulates the generation of more erythrocytes
Blood Clotting
coagulation: conversion of liquid components of blood into a solid
fibrinogen: inactive form of coagulant
clotting begins when injury exposes proteins in broken blood vessel wall to blood constituents
exposed proteins attract platelets, which gather at site of injury and release clotting factors
cascade of reactions triggered
active enzyme
thrombin
formed from inactive form
prothrombin
thrombin converts fibrinogen to fibrin
aggregates into threads that form framework of clot
involves positive feedback loop
thrombus: clot that forms within a blood vessel, blocking the flow of blood
Cardiovascular Disease
Atherosclerosis, Heart Attacks, and Stroke
atherosclerosis
the hardening of the arteries by the accumulation of fatty deposits
individuals with high ratio of LDL to HDL substantially at risk for atherosclerosis
low-density lipoprotein (LDL): particle that delivers cholesterol for membrane production
density lipoprotein (HDL): particle that scavenges excess cholesterol for return to the liver
heart attack
myocardial infarction
damage or death of cardiac muscle tissue resulting from blockage of one or more coronary arteries
arteries supply oxygen-rich blood to heart muscle
stroke
death of nervous tissue in the brain due to lack of O2
hypertension
high blood pressure
42.5 Gas exchange occurs across specialized respiratory surfaces
gas exchange
often called respiratory exchange or respiration
should not be confused by energy transformations of cellular respiration
uptake of molecular O2 from the environment and the discharge of CO2 to the environment
Partial Pressure Gradients in Gas Exchange
partial pressure: the pressure exerted by a particular gas in a mixture of gases
diffusion from higher pressure to lower pressure
to calculate, pressure that a gas mixture exerts and fraction of the mixture represented by a particular gas
also applies to gases dissolved in liquid
the warmer and saltier water is, the less dissolved O2 it can hold
Respiratory Media
water more demanding gas exchange medium than air
aquatic animals expend considerable energy to carry out gas exchange
evolution enabled most to be efficient in gas echange
Respiratory Surfaces
always moist
movement of O2 and CO2 takes place by diffusion
rate of diffusion proportional to surface area across which it occurs
inversely proportional to the square of the distance through which molecules must move
sponges, cnidarians, flatworms
every cell in body is close enough to external environment that gases can diffuse quickly between any cell and the environment
respiratory surface is thin, moist epithelium that constitutes a respiratory organ
skin as respiratory organ
earthworms, as well as some amphibians and other animals
dense network of capillaries just below the skin facilitates exchange of gases between the circulatory system and the environment
Gills in Aquatic Animals
outfoldings of the body surface that are suspended in the water
regardless of distribution, gills often have total surface area greater than rest of body's exterior
ventilation
movement of respiratory medium over respiratory surface
maintains partial pressure gradients of O2 and CO2 across the gill that are necessary for gas exchange
to promote, most gill-bearing animals move their gills through water or move water over their gills
fish use motion of swimming or coordinated movements of mouth and gill cover to ventilate gills
current water enters mouth fo fish, passes though slits in pharynx, flows over gills, then exits body
concurrent exchange
exchange of a substance or heat between two fluids flowing in opposite directions
blood and water in fish gill
at each point in its travel, blood less saturated with O2 than water it meets
as blood enters gill capillary, encounters water that is completing passage through gill
water has higher PO2 than incoming blood
O2 transfer takes place
PO2 steadily increases, but so does that of water it encounters
result: partial pressure gradient that favors diffusion of O2 from water to blood along entire length of capillary
efficient: more than 80% of O2 dissolved in water is removed as water passes over respiratory surface
Tracheal Systems in Insects
network of air tubes that branch throughout the body
trachea (largest tubes) open to the outside
at tips of finest branches, moist epithelial lining enables gas exchange by diffusion
efficient exchange of O2 and CO2 does not require participation of animal's open circulatory system
Lungs
localized respiratory organs
respiratory surface not in direct contact with all other parts of the body
gap must be bridged by circulatory system
amphibians rely heavily on diffusion across all body surfaces
lungs are relatively small
most reptiles, all birds, all mammals depend entirely on lungs
Mammalian Respiratory Systems:
A Closer Look
lungs located in thoracic cavity
air enters through nostrils and is filtered by hairs, warmed, humidified, and sampled for odors as it flows through maze of spaces in nasal cavity
nasal cavity leads to pharynx
pharynx: intersection where paths for air adn food cross
when food is swallowed, the larynx (upper part of the respiratory tract) moves upward and tips of epiglottis over the glottis
allows food to go down esophagus to stomach
glottis: opening of the trachea (windpipe)
from larynx, air passes into trachea
cartilage that reinforces walls of larynx and trachea keeps part of airway open
vocal cords in larynx
trachea branches into two bronchi, one leading to each lung
bronchioles: finer tubes branching from bronchi
epithelium lining covered with cilia and thin film of mucus
mucus traps dust, pollen, and other particulate contaminants
beating of cilia move mucus upwards to the pharynx
"mucus" escalator
alveoli
where gas exchange in mammals occur
air sacs clustered at tips of bronchioles
oxygen in air entering dissolves in moist film lining inner surfaces and rapidly diffuses across epithelium into web of capillaries that surrounds each
net diffusion of CO2 occurs in opposite direction
highly susceptible to contamination
film of liquid subject to surface tension
surfactant
coats alveoli and reduces surface tension
surface active agent
42.6 Breathing ventilates the lungs
breathing: alternating inhalation and exhalation of air
How an Amphibian Breathes
positive pressure breathing: inflating the lungs with forced airflow
muscles lower floor of oral cavity, drawing in air through nostrils
with nostrils and mouth closed, floor of oral cavity rises, forcing air down trachea
exhalation follows as air is expelled by elastic recoil of lungs and by compression of muscular body wall
How a Bird Breathes
passes air over gas exchange surface in only one direction
air sacs situated on either side of lungs act as bellows that direct air flow through lungs
parabronchi: tiny channels within lungs that serve as sites of gas exchange
requires two cycles of inhalation and exhalation
highly efficient ventilation
birds pass air over gas exchange surface in only one direction during breathing
incoming fresh air does not mix with air that has already carried out gas exchange
maximizes partial pressure difference with blood flowing through the lungs
How a Mammal Breathes
negative pressure breathing: pulling, rather than pushing, air into lungs
muscle contraction to actively expand thoracic cavity
mammals lower air pressure in lungs below that of air outside of the body
lowered pressure in lungs causes air to rush through nostrils, mouth, adn down breathing tubes to alveoli
diaphragm
sheet of skeletal muscle that forms bottom wall of cavity
inhalation: diaphragm contracts (moves down)
rib cage expands as rib muscles contract
exhalation: diaphragm relaxes (moves up)
rib cage gets smaller as rib muscles relax
within thoracic cavity
double membrane surrounds lungs
inner layer adheres to outside of lungs
outer layer adheres to wall of thoracic cavity
thin space filled with fluid separates the two layers
surface tension in fluid causes layers to stick together
rib muscles and diaphragm sufficient to change lung volume when mammal is at rest
tidal volume: volume of air inhaled and exhaled with each breath
vital capacity: tidal volume during maximal inhalation and exhalation
residual volume: air that remains after forced exhalation
inhalation occurs through same airways as exhalation
maximum PO2 in alveoli always considerably less than in atmosphere
Control of Breathing in Humans
neural circuits in medulla form pair of breathing control centers that establish breathing rhythm
medulla uses ph of fluid in which it is bathed as indicator of blood CO2 concentration
sensors in medulla detect pH change
medulla's control circuits increase depth and rate of breathing
blood O2 level little effect on breathing control centers
when O2 level drops very low, O2 sensors in aorta and carotid arteries in neck send signals to breathing control centers
42.7 Adaptations for gas exchange include pigments that bind and transport gases
Coordination of Circulation and Gas Exchange
1.) During inhalation, fresh air mixes with air remaining in lungs
2.) mixture in alveoli has higher PO2 than blood flowing through alveolar capillaries
3.) PO2 and PCO2 match values for air in alveoli
blood pumped through systemic circuit
4.) in systemic capillaries, gradients of partial pressure favor net diffusion of O@ out of blood and CO2 into blood
5.) O2 unloaded/CO2 loaded, blood returned to heart and pumped to lungs again
6.) exchange occurs across alveolar capillaries
Respiratory Pigments
proteins that transport O2
circulate with blood or hemolymph and often contained within specialized cells
respiratory pigment of many invertebrates and almost all vertebrates is hemoglobin
in vertebrates, contained in erythrocytes and has four subunits
polypeptide
heme group (cofactor that has an iron atom at center)
hemoglobin efficient at delivering O2 to tissues actively consuming O2
Bohr shift: effect where low pH decreases affinity of hemoglobin for O2
Carbon Dioxide Transport
Most CO2 diffuses from plasma into erythrocytes and reacts with water
7% CO2 released by respiring cells transported in solution of blood plasma
Respiratory Adaptations of Diving Mammals
myoglobin: oxygen-storing protein
osmoregulation: the general term for the processes by which animals control solute concentrations and balance water gain and loss
excretion: ridding the body of nitrogenous metabolites and other metabolic waste products
44.1 Osmoregulation balances the uptake and loss of water and solutes
Osmosis and Osmolarity
osmolarity
unit of measurement for solute concentration
human blood: about 300 milliosmoles per liter (mOsm/L)
seawater: 1,000 mOsm/L
the number of moles of solute per liter of solution