Transcript Heart - De Anza College

Circulation
Part I

All animal cells need to gain O2 and nutrients
and give out CO2 and waste products.

2 broad strategies:
form fits function


cell in direct contact with environment (gastro
vascular cavity)
have a transport system connecting gas exchange
surface to cells (circulatory system)

When body shape and size keeps all cells in
direct or very close contact with the
environment each cell can perform the
necessary exchanges through diffusion.

Single-celled organisms – entire body in direct
contact with water.

Gastro vascular cavity: Single opening that
maintains continuity between


the fluids inside the cavity and water outside.
Body walls are two-cell thick and all cells are in
contact with water.

Hydra has a simple gastro vascular cavity
with branches extending into tentacles.
Mouth
Tentacles
Gastrovascular
cavity
Epidermis
Mesoglea
Gastrodermis


Cnidarians like jelly fishes have elaborately
branching gastro vascular cavity
Flatworms have gastro vascular cavity and
are very thin and flat
Circular
canal
Mouth
Radial canal
5 cm

Circulatory system: 3 basic components:

Circulatory fluid

Interconnecting tubes

Muscular pump

Open circulatory
system:
 circulatory fluid comes
in direct contact with the
cells;
 circulatory fluid is the
same as the interstitial
fluid (hemolymph);
 chemical exchange
occurs between
hemolymph and body
cells
 one or more hearts
(accessory hearts) –
pumping of hearts and
squeezing of sinuses
due to body movement
maintains flow of
hemolymph
Heart
Hemolymph in sinuses
surrounding organs
Anterior
vessel
Lateral
vessel
Ostia
Tubular heart
An open circulatory system.

Closed
circulatory
system:


Blood is always
confined to blood
vessels and is
always separate
from interstitial
fluid.
Exchange
happens
between blood
vessels and
interstitial fluids.
Heart
Interstitial
fluid
Small branch vessels
in each organ
Dorsal vessel
(main heart)
Auxiliary hearts
A closed circulatory system.
Ventral vessels
Heart
Heart
Hemolymph in sinuses
surrounding organs
Interstitial
fluid
Anterior
vessel
Small branch vessels
in each organ
Lateral
vessel
Ostia
Dorsal vessel
(main heart)
Tubular heart
An open circulatory system.
Auxiliary hearts
A closed circulatory system.
Ventral vessels
Closed circulatory system is:
 more effective for transportation in animals
with high metabolic activity.
 Design makes it easier to control.
 Annelids (earthworms), cephalopods (squid,
octopuses), all vertebrates

Circulation in vertebrates: heart with at least
two muscular chambers and extensive
system of blood vessels – cardiovascular
system.

Cardiovascular system is more complex in
animals with higher metabolic rates,
complexity is higher in organs with higher
metabolic activity





Arteries – carry blood away from the heart
Arterioles – smaller branches of arteries
Capillaries – thin, microscopic, with porous walls
Venules – smaller branches that converge into veins
Veins – carry blood back to heart

Heart – at least two chambers, muscular;
atrium (pl. atria) receives blood, ventricles
pump blood out

Closed circulatory system can have single or
double circulation.

Single circulation
in fish

Blood pressure drops
after flowing through
the capillary beds.

Muscle contraction
during swimming
accelerates blood
flow in the vessels.
FISHES
Gill capillaries
Gill
Artery
circulation
Heart:
Ventricle (V)
Atrium (A)
Systemic
Vein circulation
Systemic capillaries
Double circulation:

Two pumps combined in one organ (heart)

Vigorous blood flow to brains, muscles and
other organs due to repressurization of the
blood
Double circulation: Two distinct circuits

pulmonary/pulmocutaneous circuit (between heart and gas
exchange surface)
 systemic circuit (between heart and organs and tissues in the rest of
the body).
Amphibian double
circulation:
 two atria, one
ventricle
 Small ridge in
ventricle - 90% of
the separation
maintained.
 Oxygenation
happens in lungs
and on the skin
(pulmocutaneous)
 Under water blood
diverted only to skin
for oxygenation
AMPHIBIANS
Lung and skin capillaries
Pulmocutaneous
circuit
A
A
V
Left
Right
Systemic
circuit
Systemic capillaries
Reptilian circulation:
 Septum partially
divides right and left
ventricle.
 In crocodilians the
septum is complete
 Base of the arteries is
connected for
shunting of blood to
the systemic circuit
when underwater.
REPTILES (EXCEPT BIRDS)
Lung capillaries
Pulmonary
circuit
Right
systemic
aorta
A
V
Right
Left
A systemic
aorta
V
Left
Systemic capillaries
Mammalian and avian
circulation:

Complete separation of
the ventricles – four
chambered heart.
MAMMALS AND BIRDS



Left side of the heart
only circulates O2 rich
blood and the right side
only circulates O2 poor
blood.
4 chambered heart
where O2 rich and O2
poor blood is kept
completely separate
More efficient - can
provide up to 10 times
more O2 to endotherms.
Lung capillaries
Pulmonary
circuit
A
A
V
V
Right
Left
Systemic
circuit
Systemic capillaries
FISHES
AMPHIBIANS
REPTILES (EXCEPT BIRDS)
Gill capillaries
Lung and skin capillaries
Gill
Artery
circulation
Pulmocutaneous
circuit
Heart:
Ventricle (V)
Atrium (A)
A
A
MAMMALS AND BIRDS
Lung capillaries
Lung capillaries
Pulmonary
circuit
Right
systemic
aorta
A
Left
A systemic
aorta
V
Left
V
Right
Systemic
Vein circulation
V
Left
Right
Systemic
circuit
Systemic capillaries
Systemic capillaries
Systemic capillaries
Pulmonary
circuit
A
A
V
V
Right
Left
Systemic
circuit
Systemic capillaries
Systemic circuits include all body tissues except lungs. Note that circulatory systems are depicted
as if the animal is facing you: with the right side of the heart shown at the left and vice-versa.

4-chambered heart arose independently in
birds (evolved from reptiles) and mammals.

Example of convergent evolution.
Circulation
Part II

Circulatory system: 3 basic components:

Circulatory fluid

Interconnecting tubes

Muscular pump
Capillaries of
head and
forelimbs
Anterior
vena cava

Circulation in
humans
Pulmonary
artery
Pulmonary
artery
Capillaries
of right lung
Pulmonary
vein
Right atrium
Right ventricle
Posterior
vena cava
Aorta
Capillaries
of left lung
Pulmonary
vein
Left atrium
Left ventricle
Aorta
Capillaries of
abdominal organs
and hind limbs

Circulatory system: 3 basic components:

Muscular pump

Interconnecting tubes

Circulatory fluid

Details of
the human
heart
Aorta
Pulmonary artery
Pulmonary
artery
Anterior
vena cava
Left
atrium
Right
atrium
Pulmonary
veins
Pulmonary
veins
Semilunar
valve
Semilunar
valve
Atrioventricular
valve
Posterior
vena cava
Atrioventricular
valve
Right
ventricle
Left
ventricle

Cardiac cycle:



Rhythmic contraction (systole) and relaxation
(diastole) of the heart
complete sequence of pumping and filling of the
heart
using a stethoscope you can hear the sound of
the heart beating (lub – dub)
LE 42-7
Atrial systole;
ventricular
diastole
Semilunar
valves
closed
Semilunar
valves
open
AV valves
open
Atrial and
ventricular
diastole
AV valves
closed
Ventricular systole;
atrial diastole



Stroke volume – amount of blood pumped
by the ventricles in a single contraction.
Cardiac output: volume of blood pumped by
ventricles per minute.
Heart rate - rate of contraction – beats per
minute

Valves (atrioventricular and semilunar)
prevent backflow.

Heart murmur: abnormal sound due to
backflow of blood.

Maintiaing heart beat:


Vertebrate cardiac cells are autorhythmic.
Contraction has to be coordinated in an intact
heart

Sinoatrial (SA) node (pacemaker): sets the
rate and timing at which heart rates contract;
causes atria to contract simultaneously
Pacemaker
generates wave of
signals to contract.
SA node
(pacemaker)
LE 42-8a

Atrioventricular (AV) node: located in the
wall between L & R atria; relay the impulse
started by the SA node; signals delayed
(0.1sec) to let the atria empty.
Signals are delayed
at AV node.
AV
node

Signals then are relayed to the ventricles by
Bundle branches and Purkinje fibers;
ventricles contract
Signals spread
throughout
ventricles.
Signals pass
to heart apex.
Bundle
branches
Heart
apex
Purkinje
fibers

Electrical impulses made by SA node are
conducted to the skin and can be read by
electrocardiogram (ECG)
Pacemaker
generates wave of
signals to contract.
SA node
(pacemaker)
Signals are delayed
at AV node.
Signals pass
to heart apex.
AV
node
Bundle
branches
ECG
Signals spread
throughout
ventricles.
Heart
apex
Purkinje
fibers

Regulation of heart beat:



Nerves: sympathetic and parasympathetic
Hormones: epinephrine (adrenaline) - “fight or
flight” hormone; norepinephrine (noradrenaline)
Temperature: 1oC raises heart rate by 10 beats
min-1

Circulatory system: 3 basic components:

Muscular pump

Interconnecting tubes

Circulatory fluid

Patterns of blood pressure and flow reflect
the structure and arrangement of blood
vessels – form fits function

All vessels have a central lumen, lined with
endothelium (single layer of flattened
epithelial cells)
Artery
Vein
100 µm

Capillaries: just thicker than red blood cells
Endothelium
Basement
membrane
Capillary
Arteriole
Venule

Arteries: in addition
they have



superficial to
endothelium - middle
layer with smooth
muscles and elastic
fibers
superficial to smooth
muscle - connective
tissue also with elastic
fibers
thick strong walls can
accommodate and
maintain blood at high
pressure
Endothelium
Smooth
muscle
Connective
tissue
Artery
Arteriole
Valve
Endothelium

Veins:

similar layers but
thinner
Smooth
muscle
Connective
tissue
Vein
Venule

valves maintain
direction of blood flow
Artery
Vein
100 µm
Endothelium
Valve
Basement
membrane
Endothelium
Endothelium
Smooth
muscle
Capillary
Connective
tissue
Smooth
muscle
Connective
tissue
Vein
Artery
Arteriole
Venule


Velocity of blood flow: maximum velocity
in aorta, minimum in capillaries (500 times
slower)
Slow blood flow in the capillaries:


capillaries are numerous and total crosssectional volume in capillaries is much greater
than arteries
critical so that exchange of gases, nutrients, and
wastes can take place
Venae cavae
Veins
Venules
Capillaries
Arterioles
Arteries
Aorta
Velocity (cm/sec)
Area (cm2)
5,000
4,000
3,000
2,000
1,000
0
50
40
30
20
10
0

Blood pressure:




Generated by contraction of ventricles
In arteries pressure is lengthwise along the artery and
against the walls
Pressure dissipates in the capillaries
Blood entering the veins has substantially less pressure
than blood in the arteries

Systolic pressure: spike in blood pressure caused
by contraction of the ventricles (pulse)

Diastolic pressure: lower (but substantial) pressure
when ventricles relax
Venae cavae
Veins
Venules
Capillaries
Arterioles
Arteries
Aorta
Pressure (mm Hg)
120
100
80
60
40
20
0
Systolic
pressure
Diastolic
pressure
Venae cavae
Veins
Venules
Capillaries
Arterioles
Arteries
120
100
80
60
40
20
0
Aorta
Pressure (mm Hg)
Velocity (cm/sec)
Area (cm2)
5,000
4,000
3,000
2,000
1,000
0
50
40
30
20
10
0
Systolic
pressure
Diastolic
pressure

Challenge of blood flow
against gravity:




Brain has lower pressure
than heart, if too low you
will faint (horizontal)
which will bring the brain
at the same level as heart
restoring blood flow
Blood flow in vein is aided
by squeezing of blood in
veins
Important to “warm up”
and “cool down” during
exercise
Important to walk around
periodically in long flights
Direction of blood flow
in vein (toward heart)
Valve (open)
Skeletal muscle
Valve (closed)

Circulatory system: 3 basic components:

Muscular pump

Interconnecting tubes

Circulatory fluid

Blood composition and function

Connective tissue with cellular elements suspended in
plasma
Plasma 55%
Constituent
Major functions
Water
Solvent for
carrying other
substances
Ions (blood electrolytes)
Sodium
Potassium
Calcium
Magnesium
Chloride
Bicarbonate
Plasma proteins
Albumin
Cellular elements 45%
Cell type
Number
Functions
per µL (mm3) of blood
Erythrocytes
(red blood cells)
Osmotic balance,
pH buffering, and
regulation of
membrane
permeability
Separated
blood
elements
5–6 million
Leukocytes
5,000–10,000
(white blood cells)
Transport oxygen
and help transport
carbon dioxide
Defense and
immunity
Osmotic balance,
pH buffering
Fibrinogen
Clotting
Immunoglobulins
(antibodies)
Defense
Substances transported by blood
Nutrients (such as glucose, fatty acids,
vitamins)
Waste products of metabolism
Respiratory gases (O2 and CO2)
Hormones
Lymphocyte
Basophil
Eosinophil
Neutrophil
Platelets
Monocyte
250,000–
400,000
Blood clotting
Platelets

Blood clotting



Platelet plug
Fibrin clot
Anticlotting factors in blood prevent spontaneous
clotting (thrombus)
LE 42-17
Endothelium of
vessel is damaged,
exposing connective
tissue; platelets adhere
Platelets form a plug
Seal is reinforced by a clot of fibrin
Collagen fibers
Platelet plug
Fibrin clot
Platelet releases chemicals
that make nearby platelets sticky
Clotting factors from:
Platelets
Damaged cells
Plasma (factors include calcium, vitamin K)
Prothrombin
Thrombin
Fibrinogen
Fibrin
5 µm
Red blood cell

Replacement of cellular element

Stem cells



multipotent
replenish blood cells
found in the red bone marrow, especially ribs,
vertebrae, sternum, pelvis
Pluripotent stem cells
(in bone marrow)
Myeloid
stem cells
Lymphoid
stem cells
Basophils
B cells
T cells
Lymphocytes
Eosinophils
Neutrophils
Erythrocytes
Platelets
Monocytes

Cardiovascular disease (disease of the
heart and blood vessels)

Hard to detect until they affect critical blood flow

Arthrosclerosis: Hardening of arteries due to
the formation of fatty deposits causing
obstruction of blood flow

Symptoms: chest pain especially during
heavy work
Connective
tissue
Smooth
muscle
Normal artery
Endothelium
50 µm
Plaque
Partly clogged artery
250 µm

LDL (low density lipoprotein) – bad
cholesterol – contributes to formation of
deposits

HDL (high density lipoprotein) – good
cholesterol – prevents formation of deposits

Smoking, consuming trans fat can contribute
to formation of deposits

Heart attack (myocardial infraction)


Damage or death of cardiac muscle tissue (lack of
oxygen) from blockage of coronary arteries.
Stroke

Death of nervous tissue of the brain due to lack of
oxygen

Hypertension:
chronic high blood pressure – damages the
capillaries, contributes to heart attack and
stroke