Transcript Lab 5: The Heart and Blood Histology

Lab 5: The Heart and Blood Histology
mediastinum
Heart Covering: Pericardium
• Pericardium (3 layers)
– fibrous pericardium (outer layer)
made of dense CT, holds heart in
place, prevents overfilling
– serous pericardium (2 layers)
• parietal layer sticks to fibrous
pericardium
• visceral layer (= epicardium) is the
outermost layer of the heart wall
• Between parietal and visceral
layers is the pericardial cavity,
which contains serous fluid (which
reduces friction)
External Features of the Heart
The heart has:
• A base
• An apex
• 3 surfaces:
– anterior
(= sternocostal)
– inferior
(= diaphragmatic)
– posterior (= base)
External Features of the Heart
•
Sulci (= grooves)
– 1 atrioventricular
(= coronary sulcus)
– 2 interventricular
(posterior and anterior
interventricular sulci)
•
L&R auricles (= “flaps”)
•
Coronary arteries & cardiac veins
– Right coronary artery
– Left coronary artery
– Coronary Sinus (venous)
Veins vs Arteries?
anterior
posterior
The Human Heart has 4 Chambers
• L&R atria
– Receiving chambers
• L&R ventricles
– Pumping chambers
• The atria are separated by
an interatrial septum
• The ventricles are
separated by an
interventricular septum
The Human Heart has 4 Valves
• 2 atrioventricular valves:
– R atrioventricular (= tricuspid) valve (3 cusps)
– L atrioventricular (= mitral or bicuspid) valve (2 cusps)
• 2 semilunar valves (each with 3 cusps):
– Pulmonary semilunar valve (between R ventricle and
pulmonary trunk)
– Aortic semilunar valve (between L ventricle and aorta)
• Openings to coronary arteries lie in the cusps, called sinuses of Valsalva
• Cusps are flaps made of endocardium and reinforced by
cores of dense CT
Superior View of Heart Valves
The Fibrous “Skeleton” of the Heart
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•
•
•
Lies within atrioventricular septum
Surrounds all 4 valves
Made of dense CT
Functions:
– Anchors valve cusps
– Prevents overdilation of valve openings
– Serves as an insertion for bundles of cardiac
muscle
– Blocks direct spread of electrical impulses
from atria to ventricles
Special Features of the Heart Wall
Pectinate
muscles:
muscular
ridges of right
atrium wall
Crista
Terminalis
C-shaped ridge
of right atrium
Papillary
muscles:
Cone-shaped,
attached to the
chordae
tendineae
Trabeculae carneae: muscular ridges of ventricular walls
Layers of the Heart Wall
epicardium
myocardium
Heart
wall
endocardium
• Epicardium: visceral layer of serous pericardium
• Myocardium: consists mainly of cardiac muscle
• Endocardium: sheet of endothelium resting on a thin layer
of CT; lines heart chambers and makes up heart valves
Blood is pumped through 2 circuits
• Pulmonary Circuit:
– Blood vessels that
carry blood to and
from the lungs
• Systemic Circuit:
– Blood vessels that
carry blood to and
from the rest of the
body
Great Vessels of the Heart
Entering L atrium posteriorly: 2 L and 2 R pulmonary VV
Superior vena cava
R pulmonary A
Aorta [A]
- ascending
- aortic arch
- descending
L pulmonary A
Pulmonary trunk
Inferior vena cava
Blood Flow Through the Heart
A video:
http://www.heartpoint.com/theheart.html
*Which valves are passed at which points?
• The systemic circuit is
longer than the pulmonary
circuit, therefore the left
ventricle must be able to
generate greater force and
pressure with each pump,
than the right ventricle.
Note the difference in their
wall thicknesses.
• Atria are relatively thin
walled; they pump blood in
the direction of gravity and
only have to move blood
into the ventricles.
The Heart’s Own Blood Supply
• Right coronary artery
– Emerges from R side of aorta
– Descends in coronary sulcus
between R atrium and R
ventricle
Optional -- Major branches:
• Posterior interventricular A
(= posterior descending A)
• Marginal A
• Supplies R atrium, most of R
ventricle, and 80% of the time,
the inferior portion of the L
ventricle as well
The Heart’s Own Blood Supply
• Left coronary artery
– Arises from L side of Aorta
– VERY SHORT
Optional -- Major branches:
• Circumflex A
• Anterior interventricular A
(= anterior descending A)
• AIA supplies anterior wall
of both ventricles
• Circumflex supplies L
atrium and posterior part
of L ventricle
The Heart’s Own Blood Drainage
• Cardiac veins
– Carry deoxygenated
blood from the heart
tissues
– Almost all venous
blood from the heart
drains into the
coronary sinus,
which feeds into the
R atrium
• Fetal blood is
oxygenated at the
placenta, not in the
lungs. Most blood
that has been
oxygenated by the
placenta bypasses
the lungs via the
foramen ovale and
the ductus
arteriosus
• The ductus
venosus allows most
blood from the
placenta to bypass
the developing liver
Fetal
Neonatal
Fetal vessel
For now:
Ductus arteriosus
Foramen ovale
Later:
Umbilical vein
Umbilical arteries
Ductus venosus
Postnatal derivatives
ligamentum arteriosum
fossa ovalis
ligamentum teres
medial umbilical ligaments
ligamentum venosum
Adult Remnants of Fetal Heart
Ligamentum
arteriosum
Fossa ovalis
- Thin, sheet like
The Cardiac Cycle
• Systole= the period of ventricular
contraction
• Diastole= the period of ventricular
relaxation
Chamber-to-Chamber Valves
Chamber-to-Vessel Valves
Heart Sounds
• Closure of heart valves causes vibrations
in adjacent heart walls and blood; these
vibrations constitute the heart sounds
• “Lub”: Produced by the closing of AV
valves at the start of ventricular systole
• “Dub”: Produced by the closing of the
semilunar valves at the end of ventricular
systole
systole = 1st heart sound
A-V valves close = “lub”
diastole = 2nd heart sound
pulmonic and aortic semilunar valves close = “dub”
The Conduction System of the Heart
• Sinoatrial (SA) node
• Internodal pathway fibers
• Atrioventricular (AV) node
• AV bundle (= Bundle of His)
• R and L bundle branches
• Purkinje fibers
SA node
Internodal fibers
AV node
AV Bundle
Bundle branches
Purkinje fibers
Conduction System of the Heart
• Sinoatrial node
– Node of muscle cells
– Lies in wall of R atrium
– Pacemaker of heart,
sets basic heart rate
– Generates ~70-80
impulses/minute
Conduction System of the Heart
• Atrioventricular node
– Impulses travel from SA
node via internodal
pathway fibers
– Located in inferior part of
interatrial septum
– Impulses that arrive here
are delayed for a fraction
of a second before
passing on to the AV
bundle. This allows
ventricles to fill before
they start to contract
Conduction System of the Heart
• Atrioventricular bundle
– Enters interventricular
septum and divides in to
R and L bundle
branches
– Midway down the
interventricular septum,
bundle branches split into
Purkinje fibers
Conduction System of the Heart
• Purkinje Fiber Cells
– Approach the apex of
the heart and then turn
superiorly
– This orientation enables
contraction of the
ventricles to start at the
apex and travel
superiorly, ejecting the
blood up and out into
the great arteries
Conduction System of the Heart
• Cardiac muscle cells are intrinsically able
to generate and conduct impulses
• Nodal cells and the cells of the AV bundle
are small, but typical cardiac muscle cells
• Purkinje fibers are long rows of large
diameter, barrel shaped cardiac muscle
cells, specialized for conduction more than
contraction
Purkinje fiber cells
What controls heart rate?
• The intrinsic rate of contraction can be
affected by:
– Changes in hormone level (epinephrine)
– Outside neural controls, specifically those of
the Autonomic Nervous System (ANS)
• innervates smooth muscle, cardiac muscle, and
glands
• regulates visceral functions (blood pressure, heart
rate, digestion, elimination)
What controls heart rate?
There are 2 types of autonomic nervous control:
• Parasympathetic:
– via Vagus nerve
– reduces heart rate and the force of contractions
– resting and digesting states
• Sympathetic:
– increases heart rate and the force of contractions
– fight or flight states
Blood
- specialized form of connective tissue
- components:
- blood cells (several types)
- plasma (extracellular matrix)
Functions of Blood
• Transport nutrients and respiratory gases
• Transport waste products to organs and tissues
where they can be recycled or released
• Transport hormones
• Transport immune cells throughout the body
• Helps regulate body temperature
Components of Plasma
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•
•
Water (~90%)
Nutrients
Waste products (CO2, ammonia, urea)
Hormones
Oxygen
Proteins
– including fibrinogen, a clotting factor
• Serum = everything in plasma, minus the
clotting factors
Relative Amounts of Blood Cells
The Staining of Blood Cells
• Blood smears are usually stained with a
mix of:
– Eosin, an acidic dye that stains pink
– Methylene blue, a basic dye that stains blue
to purple
• Take note of the staining of blood cells in
your Wheater’s book and on the prepared
slides!
Erythrocytes (RBCs)
• Small, biconcave discs
• Transport oxygen and CO2,
cytoplasm is full of hemoglobin
molecules
• Have no nuclei or organelles
• Pick up O2 at lung capillaries
and release it at body tissue
capillaries
• Survive for ~100-120 days in
the circulation. Worn out RBCs
are removed by macrophages
of the spleen and liver.
Blood cell disorders
Sickle cell
Spherocyte
Leukocytes
• Originate in the bone marrow and released
continuously into the blood
• Travel in bloodstream but function mainly
outside of the bloodstream (in loose CT)
• 5 types organized into 2 groups
– Granulocytes
• Neutrophils
• Eosinophils
• Basophils
– Agranulocytes
• Lymphocytes
• Monocytes
Granulocytes
• cytoplasmic granules (containing enzymes or
chemicals)  makes cytoplasm look grainy
• Non-spherical nuclei with lobes
• All are phagocytic; they engulf and consume
foreign cells and material
• 3 main types
Granulocytes: Neutrophils
• Up to 5 lobes in nucleus
connected by “threads” of
nuclear material
• Red nucleus, light purple-pink
cytoplasm
• Called neutrophils because
cytoplasm takes up red
(acidic) and blue (basic) stains
equally
• Specialized for responding to
bacterial invasions
Granulocytes: Eosinophils
• Usually have bi-lobed nuclei
connected by a short “thread”
of nuclear material
• Large cytoplasmic granules,
which stain red with the acidic
eosin dye (eosinophil = eosin
loving)
• Help in ending allergic
reactions and in fighting
parasitic infections
Granulocytes: Basophils
• Rarest leukocyte – might not see
these under the microscopes
• Usually have bi-lobed, S-shaped
nuclei but their granules often
makes it hard to see
• Has large granules that stain dark
purple in basic dyes (basophil =
basic loving)
• Granules contain histamine and
other molecules that mediate
inflammation in allergic reactions
and parasitic infections
Agranulocytes
• Granules in cytoplasm are absent or too
small to see
– Cytoplasm appears clear blue
• 2 types based on structure (not cell lineage):
– Lymphocytes
– Monocytes
Agranulocytes: Lymphocytes
• Dark purple nucleus occupies
most of cell volume
• Cytoplasm is light blue
• Different types of T cells
– some directly kill foreign or infected
cells; others activate phagocytes to
destroy microbes
• B cells differentiate into plasma
cells
– secrete antibodies that bind to
specific antigens and mark them for
destruction by phagocytic cells
Can be confused
with basophils!
Agranulocytes: Monocytes
• Largest leukocytes
• Clear blueish cytoplasm & a
large C-shaped purple
nucleus
• Larger proportion of
cytoplasm than lymphocytes
• Travel through bloodstream
to reach connective tissues,
where they transform into
macrophages (large
phagocytic cells)
Thrombocytes (Platelets)
• Disc-shaped, plasma
membrane enclosed
fragments of
cytoplasm
• Broken off from
larger cells called
megakaryocytes
• Aids in clotting by
plugging tears in
vessel walls
• Release secretory
granules that help
recruit other platelets
Blood Cell Formation (Hematopoiesis)
• Begins during embryonic development
– yolk sac, liver, spleen, bone marrow
• Continues throughout life
– only in bone marrow after 28 weeks
• After birth, all blood cells originate in bone
marrow
Bone Marrow and Hematopoiesis
• Red bone marrow actively generates
blood cells
– In adults, found only in vertebrae and girdles,
and in the proximal epiphysis of the humerus
and femur
• Yellow marrow is dormant; only makes
blood cells in emergencies
– Fat storage
– Long bone marrow cavities
The Microscopic Structure of Bone Marrow
• Loose reticular CT
forms a “labyrinth of
caverns” between
bone trabeculae where
blood cells form
• Prevalent cell types
include reticular cells
(specialized fibroblasts
which secrete the fiber
network), adipocytes,
developing blood cells,
macrophages, stem
cells
Blood Cell Differentiation
One type of blood stem cell
which can differentiate into
multiple blood stem cell
lineages:
- RBC lineage
- Granular leukocyte lineage
-Monocyte lineage
- Platelet lineage
- Lymphocyte lineage with a
different precursor than
other blood cells
Bone Marrow
megakaryocyte
RBCs: some have nuclei
Blood