Download circulatory system

Learning Objectives
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Define what you understand by the term “Angiology”.
State the organs of circulatory and lymphatic system.
Mention the various functions of circulator system and lymphatic system.
Contrast lymph and circulatory system.
List the functions of blood and lymph.
Trace the path of blood in the typical animal body. Begin with the aorta.
State what you understand by the term “ANGIOLOGY”
The word ANGIOLOGY came from Greek “angiologos” which means: angio, “vessel”;
and logos, “knowledge”. It is the medical specialty which deals with the disease of
circulatory system and lymphatic system, i.e., arteries, veins and lymphatic vases,
and its diseases.
Living things must be capable of transporting nutrients, wastes and gases to and
from cells. Single-celled organisms use their cell surface as a point of exchange
with the outside environment. Multicellular organisms have developed transport and
circulatory systems to deliver oxygen and food to cells and remove carbon dioxide
and metabolic wastes.
Multicellular animals do not have most of their cells in contact with the external
environment and so have developed circulatory systems to transport nutrients,
oxygen, carbon dioxide and metabolic wastes. Components of the circulatory system
include
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blood: a connective tissue of liquid plasma and cells
heart: a muscular pump to move the blood
blood vessels: arteries, capillaries and veins that deliver blood to all tissues
There are several types of circulatory systems. The open circulatory system,
examples of which are diagrammed in Figure below, is common to molluscs and
arthropods. Open circulatory systems (evolved in insects, mollusks and other
invertebrates) pump blood into a hemocoel with the blood diffusing back to the
circulatory system between cells. Blood is pumped by a heart into the body cavities,
where tissues are surrounded by the blood. The resulting blood flow is sluggish.
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Vertebrates, and a few invertebrates, have a closed circulatory system, shown in
Figure BOV (BELOW). Closed circulatory systems (evolved in echinoderms and
vertebrates) have the blood closed at all times within vessels of different size and
wall thickness. In this type of system, blood is pumped by a heart through vessels,
and does not normally fill body cavities. Blood flow is not sluggish. Hemoglobin
causes vertebrate blood to turn red in the presence of oxygen; but more
importantly hemoglobin molecules in blood cells transport oxygen. The human closed
circulatory system is sometimes called the cardiovascular system. A secondary
circulatory system, the lymphatic circulation, collects fluid and cells and returns
them to the cardiovascular system.
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Identify the Organs of circulatory system and lymphatic system
Circulatory system:
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Heart: a muscular pump to circulate the blood.
Blood: a connective tissue of liquid plasma and Cells, tissues.
Blood vessels: arteries, capillaries and veins that deliver blood to all
tissues and cells.
Lymphatic system:
The lymphatic system consists of organs, vessels, capillaries, and nodes.
Mention the Functions of circulatory system
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This system is involved in transport of nutrients
and oxygen to the cells and removal of metabolic
waste from the cells.
Transport of hormones to target organs.
Aids in the regulation of body temperature.
Body defense- WBCs as antigens.
Maintains water balance- blood plasma.
Mention the Function of lymphatic system.
 To collect and return intestinal fluid, involving plasma protein to the blood,
and thus help maintain fluid balance.
 To defend the body against disease by producing lymphocytes.
 To absorb lipids from the intestine and transport them to the blood.
Discuss the Vascular Systems of farm animals.
 The invertebrates have the open type of circulator system whereas in higher
vertebrates it is closed type. Former type lacks vessels where the blood is
pumped in body cavity called as hemocoel therefore the flow of blood is
sluggish. But, in closed type of circulatory system have the blood closed at
all times within vessels of different size and wall thickness, so the flow of
blood is not sluggish.
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 The Chambered heart completely separates oxygen-rich and oxygendepleted blood, as is shown in Figure 1.
 Fish have a two-chambered heart.
 Amphibians have a three-chambered heart with two atria and one ventricle.
 Birds and mammals have a four-chambered heart.
Fig. 1 Images from Purves
et al.
Comprehend heart on following sub-topic:
a) Location:
b) Chambers:
c) Valves:
d) Layers:
Anatomy of heart.
Structures
Right heart.
Left heart
Layers
Atria (interatrial septum). Ventricles (interventricular
septum). valves
(Vena cavae, coronary sinus) → Right atrium (auricle) →
tricuspid valve → right ventricle → pulmonary valve →
(pulmonary artery and pulmonary circulation).
(Pulmonary veins) → left atrium (auricle) → mitral valve
→ left ventricle → aortic valve (aortic sinus) → (aorta
and systemic circulation).
pericardium (sinus) • epicardium • myocardium •
endocardium •
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a) Location of heart.
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The construction, the form, and the position of heart are similar in all
mammals. The connective tissue invests the heart which is called as
“pericardium”.
The pericardium is included within the mediastinum. It is conical and is
placed asymmetrically within the thorax with larger part lying to the left of
the median plane.
The base is dorsal and reaches approximately to the horizontal plane that
bisects the first rib; the apex is placed close to the sternum.
The projection of pericardium upon the chest wall extends between the
third and sixth ribs. Heart is under cover of the forelimbs.
b) Chambers.
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As stated earlier all farm animals have all four chambers in the heart – two
atria (auricle) and two ventricles they are referred as right and left
according to their which region they are located.
The two atria are separated by an internal septum called interatrial septum
as are the two ventricles interventricular septum; but the atrium and
ventricle of each side communicate through a large opening.
The heart thus consists of two pumps that are arranged in series but
combined within a single organ.
The right pump receives de-oxygenated (venous) blood from the body and
ejects it into the pulmonary trunk which carries it to the lungs for reoxygenation; the left pump receives the oxygenated (arterial) blood from
the lungs and ejects it into the aorta which distributes it once more to the
body. The sizes vary among the animals.
The right atrium (in older texts termed the “right auricle”)
 This chamber lies mainly on the right.
 It receives de-oxygenated blood from the cranial and caudal vena
cava and the coronary sinus, and pumps it into the right ventricle
through the tricuspid valve.
 The sinoatrial node (SA node) is located within this chamber next to
the vena cava.
 SA node is a group of pacemaker cells which spontaneously depolarize
to create an action potential.
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The left atrium (in older texts termed the “left auricle”)
 It receives oxygenated blood from the pulmonary veins, and pumps it into
the left ventricle.
 Blood is pumped through the left atrioventricular orifice, which contains the
mitral valve.
The right ventricle
 It receives de-oxygenated blood from the right atrium via the tricuspid
valve (right atrioventricular), and pumps it into the pulmonary artery via the
pulmonary valve.
 It is triangular in form, and extends from the right atrium to near the apex
of the heart.
 It’s under surface is flattened, rests upon the diaphragm, and forms a small
part of the diaphragmatic surface of the heart.
 Its posterior wall is formed by the ventricular septum.
 Its upper and left angle forms a conical pouch, from which the pulmonary
artery arises.
 The wall of the right ventricle is thinner than that of the left, But thicker
than that of the atria.
 Between the atria and the ventricles are tricuspid valves, overlapping layers
of tissue that allow blood to flow only in one direction.
 Valves are also present between the ventricles and the vessels leading from
it.
The left ventricle
 It receives oxygenated blood from the left atrium via the mitral (bicuspid)
valve, and pumps it into the aorta via the aortic valve.
 The left ventricle is longer and more conical in shape than the right.
 It forms a small part of the sternocostal surface and a considerable part of
the diaphragmatic surface of the heart; it also forms the apex of the heart.
C) Valves
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The tricuspid valve is on the right side of the heart, between the right
atrium and the right ventricle. The normal tricuspid valve usually has three
leaflets and three papillary muscles. ***** The tricuspid valve also opens
and closes at periods of time making the blood flow through from the right
atrium to the right ventricle*****
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The mitral valve (also known as the bicuspid valve or left atrioventricular
valve), is a dual flap valve in the heart that lies between the left atrium (LA)
and the left ventricle (LV). In Latin, the term mitral means shaped like a
miter, or bishop's cap. The mitral valve and the tricuspid valve are known
collectively as the atrioventricular valves because they lie between the atria
and the ventricles of the heart and control flow.
d) Layers
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Made up of three (3) distinct layers:
The pericardium is a double-walled sac that contains the heart and the roots
of the great vessels.
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the visceral layer, also known as the epicardium.
Space called
the pericardial
cavity, which
contains a
supply of fluid.
The serous
fluid that is
found in this
space is known
as the
pericardial
fluid enclosed
by parietal and
visceral
pericardium.
The layer next
to the heart is
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Great vessels
heart
Visceral pericardium
Connective tissue
Pericardial cavity
Parietal pericardium
Mediastinal pleura
Sternopericardial ligament.
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Epicardium describes the outer layer of heart tissue (from Greek; epiouter, cardium heart). When considered as a part of the pericardium, it is
the inner layer, or visceral pericardium apparently produces the pericardial
fluid, which lubricates motion between the inner and outer layers of the
pericardium.
o Functions as an outer protective layer.
o Serous membrane that consists of connective tissue covered by
epithelium.
o Includes blood capillaries, lymph capillaries, and nerve fibers.
During ventricular contraction, the wave of depolarization moves from
endocardial to epicardial surface.
The muscles fibers of the heart are self-excitatory, means they can initiate
contraction themselves without receiving signals from the brain.
Myocardium is heart muscle
Myocardium
o Relatively thick.
o Consists largely of cardiac muscle tissue responsible for forcing blood
out of the heart chambers.
o Muscle fibers are arranged in planes, separated by connective tissues
that are richly supplied with blood capillaries, and nerve fibers.
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Endocardium
o Consists of epithelial and connective tissue that contains many elastic
and collagenous fibers.
o The innermost layer of tissue that lines the chambers of the heart.
o Connective tissue also contains blood vessels and some specialized
cardiacmuscle fibers called Purkinje fibers.
o Lines all of the heart chambers and covers heart valves.
The heart, shown in Figure, is a muscular structure that contracts in a rhythmic
pattern to pump blood. An auricle is the chamber of the heart where blood is
received from the body. A ventricle pumps the blood it gets through a valve from
the auricle out to the gills through an artery.
Images from Purves et al
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Discuss the various blood vessels of farm animals.
The blood vessels are the part of cardiovascular system
The arteries, capillaries and veins form a continuous system lined by an unbroken
low-friction, the tunica interna for the transportation of blood. Arteries carry
blood away whereas veins towards the heart.
Valves
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The arteries the arterial wall is composed of three concentric tunics. The
endothelium of the inner one (tunica interna) is supported by a thin layer of
specialized connective tissue that is bounded externally by a well-developed,
fenestrated elastic sheet, the inner elastic membrane. The middle tunic (tunic
media) is the thickest and most variable layer. It is composed of an elaborately
organized admixture of elastic tissue and smooth muscle in varying proportions. The
outer tunic (tunic adventitia) is predominately fibrous. It is importance in limiting
expansion of the artery, safeguarding against spontaneous rupture. A few very
large arteries-those that are required to expand considerably when they receive
the systolic output of the ventricles-have a media predominantly composed of
concentric, fenestrated elastic membranes with relatively little muscle
interspersed. The elastic tissue stretches to absorb and store the energy
contained in the moving blood stream; later, on recoil, it releases this energy to
forward the flow of blood toward periphery. For Example-The first part of aorta,
certain of its major branches, and the pulmonary trunk.
Whereas arteries and others of smaller size have a tunica media that consists
largely of smooth muscle arranged in many closely spiraled layers. The smallest
arteries, known as arterioles, principally regulate the resistance to the flow of
blood and hence the peripheral blood pressure. They have reduced layers of muscle
progressively. Though arterioles may be little wider than the capillaries into which
they open, they are differentiated from the retention of some muscle in the wall.
The capillaries and sinusoids the capillaries are reduced to narrow
endothelial tubes supported by a very delicate connective tissue investment.
Capillaries, the smallest blood vessels, are the site for the exchange of water and
solutes between the blood stream and the interstitial fluid. Because of their small
size, the capillaries are sometimes called as “Microcirculation”. They are also called
as exchange vessels, because they exchange water and solutes between the blood
stream and the interstitial fluid takes place across the walls of the capillaries.
Minute pores are present in the capillaries which in some situation are like that of
intestinal villi and renal glomeruli. Sinusoids are a special
type of capillaries found in certain organs- liver, spleen, and
bone marrow. They are wider, less regular, and more
commonly fenestrated than the ordinary capillary and their
endothelial cells are able to extract colloidal substances
from the blood.
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Microcircul
ation (from
Cunningha
m)
The veins. The construction of larger veins is similar to that of arteries.
Anyhow the smallest one, the venules, do not posses muscle and may pass through
several successive confluences before acquiring this component of the wall. The
tunica interna is always thin and lacks an
elastic membrane (therefore collapsed
appearance); its chief distinction is its
involvement in the formation of valves
(repeated at the intervals along their
length, which ensure a uni-directional flow
and prevent reflux of blood when the
circulation stagnates. Each valve consists
of 2 or 3 semi-lunar cusps facing each
other.
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Identify the components of lymphatic system.
The system has two components. The first comprises a system of lymphatic
capillaries and larger vessels that return intestinal fluids to the blood stream. The
second compromises a variety of widely scattered aggregations of lymphoid tissue,
including the many lymph nodes.
The Lymphatic System includes
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Lymph nodes located along the paths of collecting vessels.
Isolated nodules of lymphatic patches in the intestinal wall.
Specialized lymphatic organs such as the tonsils, thymus, and spleen
The lymphatic system differs from the circulatory system in that the lymphatics
do not form a closed ring or circuit. Instead, begin blindly in the intercellular
spaces of the soft tissues of the body.
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Lymph: is a clear, colourless liquid similar to plasma and it is formed during the
metabolic exchange between the blood and the tissue.
Lymphatic vessels- a plexus of lymphatic capillaries (Wall of the lymphatic
capillary consists of a single layer) spread through most tissues collects a fraction
of the interstitial fluid (the capillaries begins blindly which is called as lymphatic
capillaries from the intercellular spaces), a fraction that is disproportionately
important, since it contains protein and other large molecules unable to enter the
less permeable blood vessels. The greater permeability of the lymphatic capillaries
also allows them to take in particulate matter, including microorganisms on occasion.
The fluid (lymph) they contain is generally pale, they are rarely conspicuous, though
easily identified once seen.
Lymphatic vessels resemble veins
in structure with these
exceptions:
o
o
o
o
Lymphatics have
thinner walls.
Lymphatics contain
more valves which
directs in one
direction i.e. to
right.
Lymphatics contain
lymph nodes
located at certain
intervals along
their course.
Lymphatics play a
critical role in
homeostasis.
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The Lymphatic Pump
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Although there is no muscular pumping organ connected with the lymphatic
vessels to force lymph onward as the heart forces blood, still lymph moves
slowly and steadily along its vessels.
 Occurs despite the fact that most of the flow is against
gravity or "uphill".
o It moves through the system in the right direction because of the
large number of valves that permit fluid flow only in one direction.
o The movement is due to breathing movements and skeletal muscle
contractions.
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Activities that result in central movement or flow are called lymphokinetic
actions.
Research has shown that literally thoracic respiration leads lymph to
“pumped" into the venous system during inspiration.
The rate of flow of lymph into venous circulation is proportional to the depth
of inspiration.
Contracting skeletal muscles also exert pressure on the lymphatics to push
the lymph forward.
Other pressure generating factors:
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o
o
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Arterial pulsations
Postural changes
Passive compression (massage) of the body soft tissues
Lymphatic nodes-
are incorrectly termed lymph glands, are placed along
the lymph pathways since they don’t secret substances, anyhow it filters lymph and
produces lymphocytes which traps the antigen (foreign particles). The nodes are
firm, smooth-surfaced, and generally ovoid or bean-shaped. Some are superficial
which can be easily noticed on palpation through the skin. Lymph node: is the
nodular gland or nodular structure located along the course of lymph vessels. It
filters lymph and produces lymphocytes.
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Each node is bounded
by a fibrous capsule, a
below which runs an
open space
(subcapsular sinus) into
which the afferent
vessels open at
scattered sites. Inside
the lymph node the
fibrous capsule
extends to form
trabeculae (thin
reticular fibers form a
supporting meshwork inside the node i.e., Fibrous septa or trabeculae extend from
the covering capsule toward the center of the node).
Branches from the subcapsular sinus lead to a medullary sinus close to the generally
indented (sunken) were the few efferent vessels emerge. The concave side of the
lymph is called as hilum. The artery and vein are attached at the hilum and allows
blood to enter and leave the organ, respectively.
The lymph node is divided into an outer cortex and inner medulla.
Cortex-
in the cortex, the subcapsular sinus drains to corticoid sinusoids. Again
due its different properties it is named as
outer and inner cortex.
It has got fluid made from the blood called
plasma.
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1=external and internal jugular veins.
2=lymph from head.
3=lymph from the shoulder and forelimb.
4=tracheal duct.
5=thoracic duct.
6=lymph from the thoracic organs.
7=cisterna chyli.
8=lymph from the abdominal organs.
9=lymph from the lumbar regions and kidneys.
10=lymph nodes of the pelvis.
11=lymph from the hind limb.
Generalized scheme of the lymph nodes and
lymphatic vessels (dorsal view). The top
represents the neck region. (text book of vet.DYCE.SACK.WENSING.
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1=parotid node.
2=mandibular nodes.
3=superficial cervical nodes.
4=accessory axillary node.
5=femoral node.
6=Popliteal node.
From" Getty, 1975
Medulla – there are two named structures in the medulla:
The medullary cords- are cords of lymphatic tissue, and include plasma cells and Tcells.
The medullary sinus (or sinusoids) is vessel-like spaces separating the medullary
cords. Lymph flows to the medullary sinus from cortical sinus, and into efferent
lymphatic vessels. Medullary sinus contains histiocytes (immobile microphages) and
reticular cells.
The function of lymph nodes act as filters, with an internal honeycomb of
reticular connective tissue filled with lymphocytes (the lymph nodes contain lymph
nodules, germinal centers in which lymphocytes-B and T cells are produced) that
collects and destroys bacteria and other antigen when the body is fighting an
infection, lymphocytes multiply rapidly and produce a characteristic swelling of
lymph nodes.
The tissue of node is divided between cortical and medullary regions. The cortex
(cortical) contains the germinal centers in which lymphocytes are continually
produced, the medulla consists of looser branching cellular cords, and both the
cortical and medullary sinuses are lined with specialized reticuloendothelial cells
(fixed macrophages) capable of phagocytosis.
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Lymph vessels and blood vessels both carry white blood cells. But lymph vessels
carry lymph, not blood. They also carry nutrients that would not fit inside small
blood vessels.
Tonsils – the name is most often used specifically for those in the pharyngeal
region where they guard against the passage of infection to deeper parts of the
respiratory and digestive systems.
1) Palatine tonsils--located on each side of the throat.
2) Pharyngeal tonsils--also known as adenoids are near the posterior openings of
the nasal cavity.
3) Lingual tonsils--near the base of the tongue
4) The tonsils serve as the first line of defense from the exterior and as such are
subject to chronic infection—tonsillitis.
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Schematic drawing of the palatine
tonsils of cattle.
Epithelium.
Tonsillar sinus.
Palatine tonsil.
Efferent sinus.
Thymus
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It is an organ whose importance is greatest in the young animal. It begins to
regress about the time of puberty and may eventually almost disappear.
The thymus has a paired origin from the third pharyngeal pouches, the buds
grow down the neck beside the trachea and invade the mediastinum in which
they extend to the pericardium.
Structure of the thymus
o The thymus is subdivided into small lobules by connective tissue septa
that extend inward from a fibrous covering capsule.
o Each lobule is composed of a sense cellular cortex and an inner less
dense medulla.
 Both cortex and medulla are composed of lymphocytes in an
epithelial framework. Got similar structures with that of
lymph nodes.
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Functions of the Thymus
o Thymus performs two important functions:
 Serves as a final site of lymphocyte development before birth.
 Soon after birth the thymus begins secreting a group of
hormones collectively called thymosin that enable lymphocytes
to develop into mature T-cells.
Spleen
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Location of the Spleen
o It is contained within the left cranial part of the abdomen where it is
joined to the greater curvature of the stomach.
Structure of the Spleen – the basis form is very dissimilar in the various
domestic species, being dumb-bell in the dog and cat; strap-like in the horse.
Because of its whitish appearance, this tissue is called white pulp. Near the
outer regions of each compartment is tissue called red pulp made up of fine
reticular fibers submerged in blood that comes
from nearby arteries.
Functions of the Spleen
Defense
o As blood passes through the sinusoids,
reticuloendothelial cell (macrophages)
lining these venous spaces remove
microorganisms from the blood and
destroy them by phagocytosis.
 Hematopoiesis
o Monocytes and lymphocytes complete their development to become
activated in the spleen.
o Before birth, red blood cells are also formed in the spleen.
Red blood cell and platelet destruction.
o Macrophages lining the spleen's sinusoids remove worn-out red blood
cells and imperfect platelets from the blood and destroy them by
phagocytosis.
o Also break apart the hemoglobin molecules from the destroyed red
blood cells and salvage their iron and globin content by returning
them to the blood stream for storage in bone marrow and liver.
Blood reservoir - Pulp of the spleen and its venous sinuses store considerable
blood which can be released during hemorrhage.
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Briefly describe Lymphatic circulation.
Lymph circulates to the lymph node via afferent lymphatic vessels and drains into
the node just beneath the capsule in a space called the subcapsular sinus. The
subcapsular sinus drains into trabecular sinus and finally into medullary sinus. The
sinus space is criss-crossed by the pseudo or pseudopodia (false feet) of
macrophages that act to trap foreign particles and filter the lymph. The medullary
sinus converges at the hilum and lymph then leaves the lymph node via the efferent
lymphatic vessel.
Lymphocytes, both B and T cells, constantly circulate the lymph nodes. They enter
the lymph node via the blood stream and cross the wall of blood vessels by process
of diapedesis.
 The B cells migrate to the nodular cortex and medulla.
 The T cells migrate to the deep cortex.
When a lymphocytes recognizes an antigen, B cells become activated and migrate to
germinal centers (by definition, a “secondary nodule” has a germinal center, while a
“primary nodule” does not). When antibody- producing plasma cells are formed,
they migrate to the medullary cords. Stimulation of the lymphocytes by antigens
can accelerate the migration process to about 10 times normal, resulting in
characteristic swelling of the lymph nodes.
The spleen (left cranial part of the abdomen, joined to the greater curvature of
the stomach) and tonsils are larger lymphoid organs that serve similar functions to
lymph nodes, though the spleen filters blood cells rather than bacteria or viruses.
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Identify the various paths or circuits way taken by the blood.
Circulatory circuits-Three circuits are
1. Pulmonary circuit
2. Systemic circuit
3. Coronary circuit
The pulmonary circulation- such circulation the blood starts or leaves
the heart through the pulmonary arteries, goes to the lungs, and returns to the
heart through the pulmonary veins. The right heart, pulmonary artery, lung and
pulmonary vein are involved in pulmonary circulation.
The pulmonary arteries: the pulmonary trunk arises from the pulmonary orifice of
the right ventricle. It is slightly expanded at its origin where it presents a small
sinus above each cusp of the pulmonary valve. The trunk, passes between the two
atria, then bends caudally over the base of the heart where it is joined on its right
face by ligament. After penetrating the pericardium it divides into right and left
pulmonary arteries, each directed to the hilus of the corresponding lung, where it
ramifies for their function.
The pulmonary veins: it opens variously into the roof of the left atrium. Valves are
absent.
The systemic circulation- the blood leaves the heart through the aorta.
Goes to all the organs of the body through the systemic arteries, and then returns
to the heart through the systemic veins. Left heart, vessels in the cranial part of
the body, aorta, liver, intestine, portal vein, kidneys, vessels in the caudal part of
the body, caudal vena cava, and cranial vena cava.
The systemic arteries:
 The aortic arch and its ramification= the origin of the aorta is similar to
that of the pulmonary trunk but is from the left ventricle. The initial
portion, the aortic bulb, is concealed between the atria and forms sinuses
above the three cusps of aortic valve. Following are the its ramifications,
Coronary arteries- run cranially, dorsally and caudally penetrating the
pericardium.
Paired subclavian artery- supplies blood to forelimb and to structures of the
neck and cervicothoracic.
Paired carotid artery- they supplies blood to brain, face.
Costocervival trunk-the second largest branch provides the first few
intercostal arteries and the deep cervical artery.
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The internal thoracic artery- the third branch provides to thoracic and sternum
which extends till abdomen.
The superficial cervical artery- fourth branch arises from the subclavian which
supplies to muscles of the ventral part of the neck, the cranial part of shoulder,
and the upper arm.
 The axillary artery= supplies blood to forelimb.
 The thoracic aorta= it runs caudally below the roof of the thorax to enter
the abdomen.
 Abdominal aorta= it follows the roof of the abdomen.
 The external Iliac artery= is the principle artery of the hind limb.
 The internal Iliac artery= supply of the pelvic viscera and walls.
The systemic veins:
Veins returns blood to the heart through the cranial venacava, caudal vena cava, and
coronary sinus (returns the bulk of blood from the heart wall).
 The cranial vena cava= is formed close to the entrance to the chest. The
veins corresponding to artery of aorta and its ramification (which provides
blood above abdomen) connects with it.
 The caudal vena cava= it is formed on the roof of the abdomen, near pelvic
inlet.
Coronary circulation- the heart muscle is supplied by its own set of blood
vessels. These are called as coronary arteries. The coronary arteries are classified
as "end circulation", since they represent the only source of blood supply to the
myocardium.
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Describe the cardiovascular circulation.
The work of the heart is to pump blood to the lungs through pulmonary circulation
and to the rest of the body through systemic circulation. This is accomplished by
systematic contraction and relaxation of the cardiac muscle in the myocardium.
cardiovascular
system, showing that the systemic
and pulmonary circulations are arranged in series and that the organs within the
systemic
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General layout of the
cardiovascular
system, showing that the systemic
and pulmonary circulations are
arranged in series and that the
organs within the systemic
circulation are arranged in parallel.
(adapted from Milnor
WR:cardiovascular physiology.
NY, oxford Unv Press,1990)
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Other parts of the conduction system include the atrioventricular node, AV bundle,
bundle of His, Purkinje’s fibers. All these components coordinate the contraction
and relaxation of the heart chambers.
Sleeping
50
awake
100
walking
running
150
200
defence reaction.
250
Heart Rate (beats/min) of dog.
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Conduction System
An effective cycle for productive pumping of blood requires that the heart be
synchronized accurately. Both atria need to contract simultaneously, followed by
contraction of both ventricles. Specialized cardiac muscle cells that make up the
conduction system of the heart coordinate contraction of the chambers.
The conduction system includes several components. The first part of the
conduction system is the sinoatrial node. Without any neural stimulation,
the sinoatrial node rhythmically initiates impulses. Because it establishes
the basic rhythm of the heartbeat, it is called the pacemaker of the heart.
Other parts of the conduction system include the atrioventricular node, AV
bundle, bundle of His, Purkinje’s fibers.
.All these components coordinate the contraction and relaxation of the heart
chambers.
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Cardiac Cycle - The cardiac cycle refers to the alternating contraction and
relaxation of the myocardium in the walls of the heart chambers, coordinated by
the conduction system, during one heartbeat. Systole is the contraction phase of
the cardiac cycle, and diastole is the relaxation phase.
The contraction of the heart and the action of the nerve nodes located on the
heart. Images from Purves et al.
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The below shows the relationship between Electro Cardio Graph (ECG) and
transmission of impulse throughout the heart.
Heart Sounds – The sounds associated with the heartbeat are due to
vibrations in the tissues and blood caused by closure of the valves. Abnormal heart
sounds are called murmurs.
Heart Rate -The sinoatrial node, acting alone, produces a constant rhythmic
heart rate. Regulating factors are reliant on the atrioventricular node to increase
or decrease the heart rate to adjust cardiac output to meet the changing needs of
the body. Most changes in the heart rate are mediated through the cardiac center
in the medulla oblongata of the brain. The center has both sympathetic and
parasympathetic components that adjust the heart rate to meet the changing
needs of the body, former increases latter decreases the heart beat.
Peripheral factors such as emotions, ion concentrations, and body temperature may
affect heart rate. These are usually mediated through the cardiac center.
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Pulse: is the wave of pressure that spreads through the arteries when the blood
is forced into the aorta with each heart beat. The rate of the pulse is the number
of pulse per minute and it is directly proportional to temperature and respiration.
Undertake a brief view on the blood composition and functions.
The blood is a complex liquid tissue that transports nutrients, respiratory gases,
metabolic products and other substances from one part to the other parts of the
body.
The flow chart below shows the types of blood:
Blood
Erythrocytes (RBC) Leucocytes (WBC)
Granulocytes
Eosinophil
Basophil
Thrombocytes (Platelets)
Agranulocytes
Monocytes
Lymphocytes
Functions of blood
o
o
o
o
o
o
o
Contains phagocytic cells that fight infection- Leucocytes are for
body defence mechanism. It phogocytose the microbes (that cause
infection) invading the body.
Erythrocytes are involved in gaseous exchange, transport of nutrients
and removal of metabolic waste.
Carry hormones from endocrine glands to target cells
Maintain water balance.
Prevent excess loss of blood by clotting- Thrombocytes are involved
in the clotting of the blood.
Contains chemicals that buffer internal pH.
Helps maintain normal body temperature.
Blood constituents
Plasma, Serum, Cells.
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60% of total.
1) Plasma- Blood minus cells. The plasma is a slightly alkaline fluid, with a typical
yellowish color. It consists of 90 % water and 10% dry matter. Nine parts of
it are made up by organic substances, whereas one part is made up by
minerals. These organic substances are composed of glucides (glucose), lipids
(cholesterol, triglycerides, phospholipids, lecithin, and fats), proteins
(globulins, albumins, and fibrinogen), glycoproteins, hormones, amino acids
and vitamins. The mineral substances are dissolved in ionic form that is
dissociated into positive and negative ions.
2) Serum- Plasma minus fibrinogen, Straw colored fluid left after clotting.
3) Cells- Formed structures in blood, Different types seen are
ERYTHR0CYTES (RED BLOOD CELLS )In lower vertebrates and birds, the RBCs are nucleated. In mammals, the RBCs are
anucleated and have the shape of a biconcave lens. RBCs form from stem cells in
the bone marrow.
The erythrocytes are the most numerous blood cells. The red cells are rich in
hemoglobin, a protein able to bind in a faint manner to oxygen. Hence, these cells
are responsible for providing oxygen to tissues and partly for recovering carbon
dioxide produced as waste. However, most CO2 is carried by plasma, in the form of
soluble carbonates.
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In the red cells of the mammalians, the lack of nucleus allows more room for
hemoglobin and the biconcave shape of these cells raises
the surface and cytoplasmic volume ratio. These
characteristics make more efficient the diffusion of
oxygen by these cells. In so-called "sickle-cell anaemia",
erythrocytes become typically sickle-shaped.
LEUKOCYTES (white cells)
White blood cells (leukocytes)
(nucleated, phagocytic cells that remove worn-out RBCs and unwanted cell debris
from the bloodstream. Leukocytes are also formed from stem cells in the bone
marrow. There are five types: Lymphocytes (B and T cells of immune system),
monocytes (differentiate into macrophages), neutrophils (60% of WBCs),
eosinophils, and basophils (allergic responses) .
monocyte
Lymphocyte
basophil
eosinophil
neutrophil
Leukocytes, or white cells, are responsible for the defense of the organism. In
the blood, they are much less numerous than red cells. Leukocytes divide in two
categories: granulocytes and lymphoid cells or agranulocytes. The term granulocyte
is due to the presence of granules in the cytoplasm of these cells. In the different
types of granulocytes, the granules are different and help us to distinguish them.
In fact, these granules have a different affinity towards neutral, acid or basic
stains and give the cytoplasm different colors. So, granulocytes distinguish
themselves in neutrophil, eosinophil (or acidophil) and basophil. The lymphoid cells,
instead, distinguish themselves in lymphocytes and monocytes.
PLATELETS
The main function of platelets, or thrombocytes, is to stop the loss of blood from
wounds (hematostasis). To this purpose, they aggregate and release factors which
promote the blood coagulation. They are much smaller than erythrocytes.
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T- Lymphocytes
Platelets
RBCs
Brief the Clinical importance
1. Anaemia: is a condition in which either there is less red blood cells (RBC) in
circulation or haemoglobin content in RBC. Anaemia can occur when there is
heavy parasite infestation (endoparasite or ectoparsite), haemorrhage
(internal of external) can also result in anaemia. Protozoan infections like
Babesiosis cause anaemia due heavy destruction of RBC.
2. Oedema: Is the accumulation of fluid in tissue. This mainly due to imbalance
in osmotic pressure between blood and tissue. This is seen when there is
heavy parasite like Liver fluke infestation causing decrease in blood protein
level that reduces osmotic pressure in blood resulting in drainage of fluid
from blood into tissue in dependent parts.
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35
References.
1)
http://images.google.com/imgres?imgurl=http://education.vetmed.vt.edu/Curriculum/VM8054
/Labs/Lab13/IMAGES/THYMUS%2520COMPOSITE%2520SMALL.jpg&imgrefurl=http://edu
cation.vetmed.vt.edu/Curriculum/VM8054/Labs/Lab13/Lab13.htm&h=413&w=864&sz=114&hl=
en&start=3&um=1&tbnid=kOg1FB4xsTkKdM:&tbnh=69&tbnw=145&prev=/images%3Fq%3Dthy
mus%2Bof%2Bcattle%26svnum%3D10%26um%3D1%26hl%3Den
2) Notes for diploma (by Dr. Penjor and Nidup. K)
3) http://images.google.com/imgres?imgurl=http://www.ucd.ie/vetanat/images/65.gif&imgrefurl
=http://www.ucd.ie/vetanat/images/image.html&h=550&w=845&sz=146&hl=en&start=9&um=1
&tbnid=k1_z53cv_aHqtM:&tbnh=94&tbnw=145&prev=/images%3Fq%3Ddeep%2Blymph%2Bdra
inage%2Bof%2
4) http://images.google.com/imgres?imgurl=http://www.ucd.ie/vetanat/images/65.gif&imgrefurl
=http://www.ucd.ie/vetanat/images/image.html&h=550&w=845&sz=146&hl=en&start=9&um=1
&tbnid=k1_z53cv_aHqtM:&tbnh=94&tbnw=1
45&prev=/images%3Fq%3Ddeep%2Blymph%2Bdrainage%2Bof%2Bthe%2Bdog%2B%26svnum%3D1
0%26um%3D1%26hl%3Den%26sa%3DG.
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