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Section 1: Blood
• Cardiovascular system
– Includes:
• Fluid (blood)
– Includes ~75 trillion cells
• Series of conducting hoses (blood vessels)
• Pump (heart)
The Components of the Cardiovascular System
THE HEART
propels blood and maintains blood pressure.
Heart
BLOOD VESSELS
distribute blood around the body.
Capillaries
permit diffusion between blood and
interstitial fluids.
Capillaries
Arteries
carry blood away from the heart to the
capillaries.
Artery
Veins
return blood from capillaries to the
heart.
Vein
BLOOD distributes oxygen, carbon dioxide, and
blood cells; delivers nutrients and hormones;
transports waste products; and assists in
temperature regulation and defense against disease.
Figure 17 Section 1
1
Section 1: Blood
• Functions of blood
– Transportation of dissolved gases, nutrients,
hormones, and metabolic wastes
– Regulation of the pH and ion composition of
interstitial fluids
– Restriction of fluid loss at injury sites
– Defense against toxins and pathogens
– Stabilization of body temperature
Module 17.1: Blood components
• Blood
– Is a fluid connective tissue
– About 5 liters (5.3 quarts) in body
• 5–6 in males, 4–5 in females (difference mainly body size)
– Consists of:
• Plasma (liquid matrix)
• Formed elements (cells and cell fragments)
– Properties
• Temp is roughly 38°C (100.4°F)
• Is 5× more viscous than water (due to solid components)
• Is slightly alkaline (average pH 7.4)
Module 17.1: Blood components
• Whole blood
– Term for removed blood when composition is
unaltered
• May be fractionated or separated
– Plasma
» 46%–63% of blood volume
– Hematocrit (or packed cell volume [PCV])
» Percentage of whole blood contributed by formed elements
(99% of which are red blood cells)
» Average 47% for male (range 40%–54%)
» Average 42% for female (range 37%–47%)
Module 17.1: Blood components
• Plasma
– Composition resembles interstitial fluid in many ways
•
•
•
•
Exists because exchange of water, ions, and small solutes
92% water
7% plasma proteins
1% other solutes
– Primary differences
• Levels of respiratory gases (oxygen and carbon dioxide)
• Concentrations of dissolved proteins (cannot cross capillary
walls)
Module 17.1: Blood components
• Plasma proteins
– In solution rather than as fibers like other
connective tissues
– Each 100 mL has ~7.6 g of protein
• ~5× that of interstitial fluid
– Large size and globular shapes prevent leaving
bloodstream
– Liver synthesizes >90% of all plasma proteins
Module 17.1: Blood components
• Plasma proteins (continued)
– Albumins
• ~60% of all plasma proteins
• Major contributors to plasma osmotic pressure
– Globulins
• ~35% of all plasma proteins
• Antibodies (immunoglobulins) that attack pathogens
• Transport globulins that bind ions, hormones, compounds
– Fibrinogen
• Functions in clotting and activate to form fibrin strands
– Many active and inactive enzymes and hormones
Module 17.1: Blood components
• Plasma solutes
– Electrolytes
• Essential for vital cellular activities
• Major ions are Na+, K+, Ca2+, Mg2+, Cl–, HCO3–, HPO4–, SO42–
– Organic nutrients
• Used for cell ATP production, growth, and maintenance
• Includes lipids, carbohydrates, and amino acids
– Organic wastes
• Carried to sites of breakdown or excretion
• Examples: urea, uric acid, creatinine, bilirubin, NH4+
Plasma
(46–63%)
Whole
blood
consists of
Formed
elements
(37–54%)
Figure 17.1
1
Module 17.1: Blood components
• Formed elements
– Platelets
• Small membrane-bound cell fragments involved in clotting
– White blood cells (WBCs)
• Also known as leukocytes (leukos, white + -cyte, cell)
• Participate in body’s defense mechanisms
• Five classes, each with different functions
– Red blood cells (RBCs)
• Also known as erythrocytes (erythros, red + -cyte, cell)
• Essential for oxygen transport in blood
Module 17.1 Review
a. Define hematocrit.
b. Identify the two components constituting
whole blood, and list the composition of
each.
c. Which specific plasma proteins would you
expect to be elevated during an infection?
Module 17.2: Red blood cells
• RBCs in blood
– Most numerous cell type in blood
•
Roughly 1/3 of all cells in the body
– Red blood cell count (standard blood test) results
•
•
•
Adult males: 4.5–6.3 million RBCs/1 µL or 1 mm3 of whole
blood
Adult females: 4.2–5.5 million RBCs/1 µL or 1 mm3 of
whole blood
One drop = 260 million RBCs
Module 17.2: Red blood cells
• RBC characteristics
– Biconcave disc
– Average diameter ~8 µm
– Large surface area-to-volume ratio
•
Greater exchange rate of oxygen
– Can form stacks (rouleaux)
•
Facilitate smooth transport through small vessels
– Are flexible
•
Allow movement through capillaries with diameters
smaller than RBC (as narrow as 4 µm)
Stained blood smear
LM x 450
Figure 17.2
1
The size and biconcave shape of an RBC
7.2–8.4 μm
0.45–1.16 μm
RBCs
2.31–2.85 μm
Colorized SEM x 1800
Figure 17.2
2
The advantages of the biconcave shape of RBCs
Functional Aspects of Red Blood Cells
• Large surface area-to-volume ration. Each
RBC carries oxygen bound to intracellular
proteins, and that oxygen must be absorbed or
released quickly as the RBC passes through the
capillaries. The greater the surface area per unit
volume, the faster the exchange between the
RBC’s interior and the surrounding plasma. The
total surface area of all the RBCs in the blood of a
typical adult is about 3800 square meters, roughly
2000 times the total surface area of the body.
Rouleaux
(stacks of RBCs)
Blood vessels (viewed
in longitudinal section)
• RBCs can form stacks. Like dinner plates,
RBCs can form stacks that ease the flow through
narrow blood vessels. An entire stack can pass
along a blood vessel only slightly larger than the
diameter of a single RBC, whereas individual
cells would bump the walls, bang together, and
form logjams that could restrict or prevent blood
flow.
• Flexibility. Red blood cells are very flexible and
can bend and flex when entering small capillaries
and branches. By changing shape, individual
RBCs can squeeze through capillaries as narrow
as 4 μm.
Nucleus of endothelial cell
Red blood cell (RBC)
Sectional view of capillaries
LM x 1430
Figure 17.2
3
Module 17.2: Red blood cells
•
RBC characteristics (continued)
–
Lose most organelles including nucleus during development
•
–
Cannot repair themselves and die in ~120 days
Contain many molecules (hemoglobin) associated with
primary function of carrying oxygen
•
•
Each cell contains ~280 million hemoglobin (Hb) molecules
Normal whole blood content (grams per deciliter)
–
•
14–18 dL (males), 12–16 dL (females)
~98.5% of blood oxygen attached to Hb in RBCs
–
Rest of oxygen dissolved in plasma
Module 17.2: Red blood cells
•
Hemoglobin
–
–
Protein with complex quaternary structure
Each molecule has 4 chains (globular protein subunits)
•
•
–
2 alpha (α) chains
2 beta (β) chains
Each chain contains a single heme pigment molecule
•
Each heme (with iron) can reversibly bind one molecule of oxygen
–
Forms oxyhemoglobin (HbO2) (bright red)
»
Deoxyhemoglobin when not binding O2 (dark red)
Figure 17.2
4
The quaternary structure
of hemoglobin
β chain 1
α chain 1
β chain 2
Heme
α chain 2
Figure 17.2
5
The chemical structure
of a heme unit
Heme
Figure 17.2
6
Module 17.2 Review
a. Define rouleaux.
b. Describe hemoglobin.
c. Compare oxyhemoglobin with
deoxyhemoglobin.
Section 1: Heart Structure
• Location of the heart
– Near anterior chest wall, directly posterior to
sternum
– Center lies slightly to the left of midline
– Entire heart is rotated slightly left
Section 1: Heart Structure
• Gross anatomy
– Base (superior surface where major vessels attach)
– Apex (inferior pointed tip)
– Borders
• Superior border (formed by base)
• Right border (formed by right atrium)
• Left border (formed by left ventricle and small part of left
atrium)
• Inferior border (formed mainly by inferior wall of right
ventricle)
The location of the heart
in the chest cavity
Base
1
2
3
4
5
6
7
8
9
10
1
2
3
Ribs
4
5
Apex
6
7
8
9
10
Figure 18 Section 1
1
An anterior view showing the
borders of the heart
Superior border
Right border
Left border
Inferior border
Figure 18 Section 1
2
Module 18.1: Heart wall and tissue
• Layers of heart wall
1. Epicardium (visceral pericardium)
•
•
Covers surface of heart
Serous membrane made of exposed mesothelium and
underlying areolar tissue (attaching to myocardium)
– Parietal pericardium
•
•
Not a heart wall layer but is continuous serous
membrane with visceral pericardium
Lines pericardial cavity and fibrous pericardial sac
Module 18.1: Heart wall and tissue
• Layers of heart wall (continued)
2. Myocardium
•
•
Middle, muscular layer forming atria and ventricles
Contains cardiac muscle tissue, blood vessels, and
nerves
–
Concentric muscle tissue layers
» Form a figure-eight around the atria
» Superficial muscle layers wrap both ventricles
» Deep muscle layers form figure-eight around ventricles
The direction of muscle
bundles of the atrial and
ventricular musculature
Atrial
musculature
Ventricular
musculature
Figure 18.1
2
Module 18.1: Heart wall and tissue
• Layers of heart wall (continued)
3. Endocardium
•
•
Covering inner surfaces of heart, including valves
Composed of simple squamous epithelial tissue and
underlying areolar tissue
–
Forms endothelium continuous with blood vessel
endothelium
A section of the heart showing its three layers: epicardium,
myocardium, and endocardium
Parietal Pericardium
The serous membrane that
forms the outer wall of the
pericardial cavity; it and a
dense fibrous layer form the
pericardial sac surrounding
the heart
Pericardial cavity
(contains serous fluid)
Dense fibrous layer
Areolar tissue
Mesothelium
Myocardium
Muscular wall of the heart
consisting primarily of
cardiac muscle cells
Epicardium
Covers the outer surface
of the heart; also called
the visceral pericardium
Mesothelium
Areolar tissue
Connective tissues
Endocardium
Covers the inner surfaces of
the heart
Endothelium
Areolar tissue
Figure 18.1
1
Module 18.1: Heart wall and tissue
• Cardiac muscle tissue
– Compared to skeletal muscle tissue
1.
2.
3.
4.
Small cell size
Single, centrally located nucleus
Branching interconnections
Specialized intercellular connections
–
Intercalated discs
A light micrograph showing
the histological characteristics
of cardiac muscle tissue
Intercalated discs
Cardiac muscle tissue
LM x 575
Figure 18.1
3
Module 18.1: Heart wall and tissue
• Cardiac muscle tissue (continued)
– Found only in the heart
– Cells are striated due to organized myofibrils
– Almost totally dependent on aerobic
metabolism for ATP
• Large numbers of mitochondria and myoglobin to
store O2
• Has large number of capillaries to supply nutrients
and O2
Module 18.1: Heart wall and tissue
• Intercalated discs
– Contain:
• Desmosomes
• Gap junctions
– Allow ions and molecules to move directly between cells
» Create direct electrical connection so an action potential
can pass directly between cells
– Stabilize relative positions of adjacent cells
– Allow cells to “pull together” for maximum
efficiency
– All cells to function “as one” (functional syncytium)
The structure of cardiac muscle cells
Cardiac muscle cells, which feature organized
myofibrils, aligned sarcomeres, and numerous
mitochondria
Size of a typical cardiac muscle cell:
10–20 μm in diameter and
50–100 μm in length
Intercalated
disc (sectioned)
Nucleus
Mitochondria
Bundles of
myofibrils
Intercalated
disc
The connection of cardiac muscle cells by intercalated discs,
gap junctions, and desmosomes, forming a functional syncytium
Gap junction
Intercalated Disc
Z lines bound
to opposing cell
membranes
Desmosomes
Figure 18.1
4 – 5
Module 18.1 Review
a. From superficial to deep, name the layers of
the heart wall.
b. Describe how the cardiac muscle cells ‘talk’ to
one another.
c. Why is it important that cardiac tissue be richly
supplied with mitochondria and capillaries?
Module 18.2: Pericardial cavity
•
•
Heart lies within pericardial cavity, a subdivision of the
mediastinum
Mediastinum also contains:
–
–
–
–
•
Great vessels (entering and exiting the heart)
Thymus
Esophagus
Trachea
Because heart is closely associated with many organs, trauma
can lead to fluid accumulation that can restrict heart
movement (cardiac tamponade)
Two views showing the location of the heart in the chest cavity
The position and orientation of the heart
relative to the major vessels and the ribs,
sternum, and lungs
Trachea
Thyroid gland
A diagrammatic superior view of a partial dissection of the
thoracic cavity showing the physical relationships among the
components in the mediastinum
First rib (cut)
Esophagus
Posterior
mediastinum
Aorta (arch
segment removed)
Base of heart
Right lung
Left lung
Left pulmonary
artery
Apex of heart
Diaphragm
Right pleural cavity
Anterior view of chest cavity
Parietal
pericardium
(cut)
Right
lung
Left pleural
cavity
Left
lung
Left
pulmonary
vein
Bronchus
of lung
Aortic
arch
Right
pulmonary
artery
Pulmonary
trunk
Left atrium
Right pulmonary
vein
Left ventricle
Pericardial cavity
Superior vena cava
Epicardium
Right atrium
Pericardial sac
Right ventricle
Anterior mediastinum
Figure 18.2
1 – 3
Module 18.2: Pericardial cavity
• Pericardial cavity and fluid
– Lined with parietal pericardium
•
Continuous with visceral pericardium (like balloon
with fist in it)
– Contains 10–15 mL of pericardial fluid secreted
by membranes
•
Acts as lubricant when heart beats
–
Swelling of pericardial surfaces can occur with infection
causing friction (pericarditis)
The position and orientation of the heart
relative to the major vessels and the ribs,
sternum, and lungs
Trachea
Thyroid gland
First rib (cut)
Base of heart
Right lung
Left lung
Apex of heart
Diaphragm
Anterior view of chest cavity
Parietal
pericardium
(cut)
Figure 18.2
1
The positions of and relationship
between the heart and the
pericardial cavity
Wrist (corresponds
to base of heart)
Inner wall (corresponds
to epicardium)
The relationship between the heart
and the pericardial cavity, which can
be linked to a fist pressed into the
center of a partially inflated balloon
Air space (corresponds
to pericardial cavity)
Outer wall (corresponds
to parietal pericardium)
Balloon
The location of the pericardial
cavity relative to the heart
Base of heart
Cut edge of
parietal pericardium
Fibrous tissue of
pericardial sac
Pericardial cavity
containing
pericardial fluid
Parietal Pericardium
Areolar tissue
Mesothelium
Cut edge of epicardium
Fibrous attachment
to diaphragm
Apex of heart
Figure 18.2
2
Module 18.2 Review
a. Define mediastinum.
b. Describe the heart’s location.
c. Why can cardiac tamponade be a lifethreatening condition?
Module 18.3: Heart surface anatomy
•
Heart surface anoatomy
–
Sulci (singular, sulcus)
•
Surface grooves separating heart chambers
– Often with cardiac vessels covered with fat
•
Anterior interventricular sulcus
– Anterior groove separating ventricles
•
Posterior interventricular sulcus
– Posterior groove separating ventricles
•
Coronary sulcus
– Separates atria from ventricles
– On posterior surface, contains coronary sinus (collects blood from
myocardium and conveys to right atrium)
Module 18.3: Heart surface anatomy
• Other surface features
– Auricles
•
Expandable extensions of atria
– Ligamentum arteriosum
•
Fibrous remnant of fetal connection between aorta
and pulmonary trunk
Two views of the anterior surface of the heart
A diagrammatic view of the
anterior surface of the heart
A photograph of an anterior view of
a heart from a preserved cadaver
Aortic arch
Ligamentum
arteriosum
Ascending aorta
Superior
vena cava
Pulmonary trunk
Parietal
pericardium
Superior
vena cava
Pulmonary
trunk
Auricle of
right atrium
Auricle of
left atrium
Right atrium
Auricle
Auricle of left atrium
Right
atrium
Ascending
aorta
Right
ventricle
Coronary
sulcus
Fat
Anterior
interventricular
sulcus
Left
ventricle
Right
ventricle
Left ventricle
Cadaver dissection, anterior view
Coronary
sulcus
Anterior
interventricular
sulcus
Anterior surface
Figure 18.3
1 – 3
Module 18.3 Review
b. Name and describe the shallow depressions
and grooves found on the heart’s external
surface.
c. Which structures collect blood from the
myocardium, and into which heart chamber
does this blood flow?
Module 18.4: Coronary circulation
• Coronary circulation
– Provides cardiac muscle cells with reliable supplies
of oxygen and nutrients
– During maximum exertion, myocardial blood flow
may increase to 9× resting levels
– Blood flow is continuous but not steady
• With left ventricular relaxation, aorta walls recoil (elastic
rebound), which pushes blood into coronary arteries
Module 18.4: Coronary circulation
•
Coronary arteries
–
Right coronary artery (right atrium, portions of both ventricles
and conduction system of heart)
•
•
–
Marginal arteries (right ventricle surface)
Posterior interventricular artery (interventricular septum and
adjacent ventricular portions)
Left coronary artery (left ventricle, left atrium, and
interventricular septum)
•
•
Circumflex artery (from left coronary artery, follows coronary
sulcus to meet right coronary artery branches)
Anterior interventricular artery (interventricular sulcus)
The locations of the arterial supply to the heart
Pulmonary
trunk
Aortic
arch
An anterior view of the coronary arteries
Left Coronary Artery
Left
atrium
Left coronary artery
Circumflex artery
Right
atrium
Right Coronary Artery
Anterior
interventricular
artery
Right
ventricle
Right coronary artery in the coronary sulcus
Left
ventricle
Marginal arteries
Anterior view
Arterial anastomoses
between the anterior
and posterior
interventricular arteries
The branches of the coronary arteries
on the posterior surface of the heart
Circumflex artery
Left
atrium
Marginal
artery
Right
atrium
Left
ventricle
Posterior
interventricular
artery
Right
ventricle
Posterior view
Right coronary
artery
Figure 18.4
1 – 2
Module 18.4: Coronary circulation
• Coronary veins
– Great cardiac vein (drains area supplied by
anterior interventricular artery, empties into
coronary sinus on posterior)
– Anterior cardiac veins (drains anterior surface
of right ventricle, empties into right atrium)
The major collecting
vessels on the anterior
surface of the heart
Aortic
arch
Left
atrium
Right
atrium
Anterior cardiac veins
Great
cardiac
vein
Right
ventricle
Left
ventricle
Anterior view
Figure 18.4
3
Module 18.4: Coronary circulation
• Coronary veins (continued)
– Coronary sinus (expanded vein, empties into right
atrium)
– Posterior cardiac vein (drains area supplied by
circumflex artery)
– Small cardiac vein (drains posterior right atrium
and ventricle, empties into coronary sinus)
– Middle cardiac vein (drains area supplied by
posterior interventricular artery, drains into
coronary sinus)
The major collecting vessels on
the posterior surface of the heart
Great
cardiac vein
Left
atrium
Coronary sinus
Right
atrium
Left
ventricle
Posterior
cardiac vein
Small
cardiac
vein
Right
ventricle
Posterior view
Middle
cardiac
vein
Figure 18.4
4
Module 18.4 Review
a. List the arteries and veins of the heart.
b. Describe what happens to blood flow
during elastic rebound.
c. Identify the main vessel that drains blood
from the myocardial capillaries.
Module 18.5: Internal heart anatomy
• Internal heart anatomy
– Four chambers
•
•
Two atria (left and right separated by interatrial
septum)
Two ventricles (left and right separated by
interventricular septum)
– Left atrium flows into left ventricle
– Right atrium flows into right ventricle
Module 18.5: Internal heart anatomy
• Right atrium
– Receives blood from superior and inferior
venae cavae and coronary sinus
– Fossa ovalis (remnant of fetal foramen ovale)
– Pectinate (pectin, comb) muscles (muscular
ridges on anterior atrial and auricle walls)
• Left atrium
– Receives blood from pulmonary veins
Module 18.5: Internal heart anatomy
• Right ventricle
– Receives blood from right atrium through right
atrioventricular (AV) valve
•
Also known as tricuspid (tri, three)
–
–
•
Has three flaps or cusps attached to tendinous connective
fibers (chordae tendineae)
Fibers connect to papillary muscles
» Innervated to contract through moderator band which
keeps “slamming” of AV cusps
Prevents backflow of blood to atrium during ventricular
contraction
Module 18.5: Internal heart anatomy
•
Left ventricle
–
Receives blood from left atrium through right atrioventricular
valve
•
•
•
–
Also known as bicuspid and mitral (mitre, bishop’s hat) valve
Prevents backflow of blood to atrium during ventricular contraction
Has paired flaps or cusps
Trabeculae carneae (carneus, fleshy)
•
–
Muscular ridges on ventricular walls
Aortic valve
•
Allows blood to exit left ventricle and enter aorta
The internal anatomy of the heart and
the direction of blood flow between
the chambers
Ascending
aorta
Pulmonary
trunk
Superior
vena cava
Right Atrium
Aortic arch
Receives blood from the superior
and inferior venae cavae and from
the cardiac veins through the
coronary sinus
Left Atrium
Receives blood from
the pulmonary veins
Left pulmonary veins
Fossa ovalis
Pectinate muscles on the inner
surface of the auricle
Opening of the coronary sinus
Left Ventricle
Right Ventricle
Thick wall of left ventricle
Right atrioventricular (AV)
valve (tricuspid valve)
Chordae tendineae
Papillary muscle
Pulmonary valve (pulmonary
semilunar valve)
Left atrioventricular (AV)
valve (bicuspid valve)
Inferior
vena cava
Trabeculae carneae
Interventricular
septum
Moderator
band
Aortic valve
Figure 18.5
1
Module 18.5: Internal heart anatomy
•
Ventricular comparisons
–
Right ventricle has relatively thin wall
•
•
–
Ventricle only pushes blood to nearby pulmonary circuit
When it contracts, it squeezes against left ventricle wall forcing
blood out pulmonary trunk
Left ventricle has extremely thick wall and is round in cross
section
•
•
Ventricle must develop 4–6× as much pressure as right to push
blood around systemic circuit
When it contracts
1.
2.
Diameter of chamber decreases
Distance between base and apex decreases
A sectional view of the heart showing
the thicknesses of the ventricle walls
and the shapes of the ventricular
chambers
Posterior
interventricular sulcus
The left ventricle has
an extremely thick
muscular wall and is
round in cross section.
The relatively thin wall
of the right ventricle
resembles a pouch
attached to the massive
wall of the left ventricle
Fat in anterior
interventricular sulcus
Figure 18.5
2
The changes in ventricle
shape during ventricular
contraction
Right
ventricle
Left
ventricle
Dilated (relaxed)
Contraction of left ventricle
decreases the diameter of the
ventricular chamber and reduces
the distance between the base
and apex
Contraction of right
ventricle squeezes
blood against the thick
wall of the left ventricle.
Contracted
Figure 18.5
3
Module 18.5 Review
a. Damage to the semilunar valves on the right side
of the heart would affect blood flow to which
vessel?
b. What prevents the AV valves from swinging into
the atria?
c. Why is the left ventricle more muscular than the
right ventricle?
d. Name the four cardiac chambers.