AHP Unit 3

1. CARDIOVASCULAR AND
LYMPHATIC SYSTEMS
UNIT 3
CARDIOVASCULAR AND
LYMPHATIC SYSTEMS

2. TOPICS TO BE COVERED
 BLOOD & BLOOD GROUP
 STRUCTURE OF HEART
 CONDUCTING SYSTEM OF HEART
 PROPERTIES OF CARDIAC MUSCLE, CARDIAC CYCLE, HEART BEAT
 BLOOD VESSELS, REGULATION OF HEART RATE & BLOOD PRESSURE
 PARTS AND FUNCTIONS OF LYMPHATIC SYSTEMS
 TYPES OF LYMPHATIC ORGANS & VESSELS
PROPERTIES OF CARDIAC MUSCLE, CARDIAC CYCLE, HEART BEAT
BLOOD VESSELS, REGULATION OF HEART RATE & BLOOD PRESSURE
PARTS AND FUNCTIONS OF LYMPHATIC SYSTEMS
TYPES OF LYMPHATIC ORGANS & VESSELS

3. BLOOD & BLOOD
GROUP
COMPONENTS OF BLOOD AND FUNCTIONS
BLOOD GROUPS AND IMPORTANCE
BLOOD & BLOOD
COMPONENTS OF BLOOD AND FUNCTIONS
BLOOD GROUPS AND IMPORTANCE

4.  Blood is the river of life.
 Blood transports everything that must be carried from one place to another
within the body—nutrients, hormones, wastes and body heat
vessels.
everything that must be carried from one place to another
nutrients, hormones, wastes and body heat—through blood

5. COMPONENTS
 Blood is a complex connective tissue in which living blood cells, the formed
elements are suspended in plasma and a nonliving fluid matrix.
 The collagen and elastin fibers typical of other connective tissues are absent from
blood; instead, dissolved proteins become visible as fibrin
clotting.
 If a sample of blood is separated, the plasma rises to the top and the formed
elements being heavier-fall to the bottom.
Blood is a complex connective tissue in which living blood cells, the formed
in plasma and a nonliving fluid matrix.
typical of other connective tissues are absent from
blood; instead, dissolved proteins become visible as fibrin strands during blood
If a sample of blood is separated, the plasma rises to the top and the formed
fall to the bottom.

6.  Most of the reddish “pellet” at the bottom of the tube is
the formed elements that function in oxygen transport.
 There is a thin, whitish layer called the buffy
erythrocytes and the plasma.
 This layer contains the remaining formed elements,
in various ways to protect the body and platelets, cell fragments that help stop bleeding.
 Erythrocytes normally account for about 45 percent of the total volume of a blood
sample, a percentage known as the hematocrit
 White blood cells and platelets contribute less than 1 percent, and plasma makes up
most of the remaining 55 percent of whole blood.
reddish “pellet” at the bottom of the tube is erythrocytes or red blood cells,
the formed elements that function in oxygen transport.
buffy coat at the junction between the
This layer contains the remaining formed elements, leukocytes , white blood cells that act
platelets, cell fragments that help stop bleeding.
Erythrocytes normally account for about 45 percent of the total volume of a blood
hematocrit (“blood fraction”).
White blood cells and platelets contribute less than 1 percent, and plasma makes up
most of the remaining 55 percent of whole blood.

7. PHYSICAL CHARACTERISTICS AND VOLUME
 Blood is a sticky, opaque fluid that is heavier than water and about five times thicker, or
more viscous, largely because of its formed elements.
 Depending on the amount of oxygen it is carrying, the
(oxygenrich) to a dull red or purple (oxygen-
 Blood has a characteristic metallic, salty taste.
 Blood is slightly alkaline, with a pH between 7.35 and 7.45.
 Its temperature (38°C, or 100.4°F) is always slightly higher than body temperature
because of the friction produced as blood flows through the vessels.
 Blood accounts for approximately 8 percent of body weight, and its volume in healthy
adults is 5 to 6 liters, or about 6 quarts.
PHYSICAL CHARACTERISTICS AND VOLUME
Blood is a sticky, opaque fluid that is heavier than water and about five times thicker, or
more viscous, largely because of its formed elements.
Depending on the amount of oxygen it is carrying, the color of blood varies from scarlet
-poor).
Blood has a characteristic metallic, salty taste.
Blood is slightly alkaline, with a pH between 7.35 and 7.45.
F) is always slightly higher than body temperature
because of the friction produced as blood flows through the vessels.
Blood accounts for approximately 8 percent of body weight, and its volume in healthy

8. PLASMA
 Plasma, which is approximately 90 percent water, is the liquid part of the blood. Over 100
different substances are dissolved in this straw
 Examples of dissolved substances include nutrients,
hormones, plasma proteins, and various wastes and
 Plasma proteins are the most abundant solutes
protein-based hormones, the liver makes most plasma proteins.
 The plasma proteins serve a variety of functions. For instance, albumin acts as a carrier
to shuttle certain molecules through the circulation, is an important blood buffer, and
contributes to the osmotic pressure of blood, which acts to keep water in the
bloodstream.
 Clotting proteins help stem blood loss when a blood vessel is injured, and antibodies help
protect the body from pathogens.
Plasma, which is approximately 90 percent water, is the liquid part of the blood. Over 100
different substances are dissolved in this straw-colored fluid.
Examples of dissolved substances include nutrients, salts (electrolytes), respiratory gases,
plasma proteins, and various wastes and products of cell metabolism.
Plasma proteins are the most abundant solutes in plasma. Except for antibodies and
based hormones, the liver makes most plasma proteins.
The plasma proteins serve a variety of functions. For instance, albumin acts as a carrier
to shuttle certain molecules through the circulation, is an important blood buffer, and
contributes to the osmotic pressure of blood, which acts to keep water in the
Clotting proteins help stem blood loss when a blood vessel is injured, and antibodies help

9. FORMED ELEMENTS

12. HEMATOPOIESIS
 Blood cell formation, or hematopoiesis, occurs in red bone marrow, or
tissue.
 In adults, this tissue is found chiefly in the axial skeleton, pectoral and pelvic
girdles, and proximal epiphyses of the humerus
 Each type of blood cell is produced in different numbers in response to changing
body needs and different stimuli.
 After they mature, they are discharged into the blood vessels surrounding the
area.
 On average, the red marrow turns out an ounce of new blood containing 100
billion new cells every day.
, occurs in red bone marrow, or myeloid
in the axial skeleton, pectoral and pelvic
humerus and femur.
Each type of blood cell is produced in different numbers in response to changing
After they mature, they are discharged into the blood vessels surrounding the
On average, the red marrow turns out an ounce of new blood containing 100

13.  All the formed elements arise from a common
stem cell, the hemocytoblast (blood cell
former), which resides in red bone marrow.
 The hemocytoblast forms two types of
descendants—the lymphoid stem cell, which
produces lymphocytes, and the myeloid stem
cell, which can produce all other classes of
formed elements
All the formed elements arise from a common
blood cell
marrow.
which
myeloid stem
cell, which can produce all other classes of

14. FORMATION OF RBCs
 Since RCBs are anucleate, they are unable to synthesize
 As they age, RBCs become rigid and begin to fall apart in 100 to 120 days. Their remains
are eliminated by phagocytes in the spleen, liver, and other body tissues.
components are salvaged.
 Lost blood cells are replaced more or less continuously by the division of
in the red bone marrow.
 The developing RBCs divide many times and then begin synthesizing huge amounts of
hemoglobin.
 When enough hemoglobin has been accumulated, the nucleus and most organelles are
ejected, and the cell collapses inward.
 The result is the young RBC, called a reticulocyte
endoplasmic reticulum
, they are unable to synthesize protiens, grow and divide.
RBCs become rigid and begin to fall apart in 100 to 120 days. Their remains
are eliminated by phagocytes in the spleen, liver, and other body tissues. RBC
Lost blood cells are replaced more or less continuously by the division of hemocytoblasts
The developing RBCs divide many times and then begin synthesizing huge amounts of
has been accumulated, the nucleus and most organelles are
reticulocyte because it still contains some rough

15.  The reticulocytes enter the bloodstream to begin their task of transporting
oxygen. Within 2 days of release, they have ejected the remaining ER and have
become fully functioning erythrocytes. The entire developmental process from
hemocytoblast to mature RBC takes 3 to 5 days.
 The rate of erythrocyte production is controlled by a hormone called
erythropoietin.
enter the bloodstream to begin their task of transporting
oxygen. Within 2 days of release, they have ejected the remaining ER and have
become fully functioning erythrocytes. The entire developmental process from
to mature RBC takes 3 to 5 days.
The rate of erythrocyte production is controlled by a hormone called

16. FORMATION OF WHITE BLOOD CELLS AND PLATELETS
 The formation of leukocytes and platelets is stimulated by hormones.
 These colony stimulating factors (CSFs) and interleukins
bone marrow to turn out leukocytes, but also enhance the ability of mature
leukocytes to protect the body.
 The hormone thrombopoietin accelerates the production
megakaryocytes, but little is known about how that process is regulated.
FORMATION OF WHITE BLOOD CELLS AND PLATELETS
and platelets is stimulated by hormones.
colony stimulating factors (CSFs) and interleukins not only prompt red
bone marrow to turn out leukocytes, but also enhance the ability of mature
accelerates the production of platelets from
, but little is known about how that process is regulated.

17. HEMOSTASIS
 Hemostasis involves three major phases,
which occur in rapid sequence: vascular
spasms, platelet plug formation, and
coagulation, or blood clotting.
 Blood loss at the site is prevented when
fibrous tissue grows into the clot and seals the
hole in the blood vessel.
involves three major phases,
vascular
Blood loss at the site is prevented when
fibrous tissue grows into the clot and seals the

18. BLOOD GROUPS

19. STRUCTURE OF HEART
STRUCTURE OF HEART

20. Structure of Heart

21.  Wall of the heart has 3 layers- epicardium
 Epicardium is serous layer covering the heart, myocardium is made up of cardiac
muscle cells which are involuntary and endocardium
endothelial cells lining the inner surface of the heart.
 The cardiac muscles have branching fibers
adjacent fibers are connected by intercalated disks. These are cell membranes
that separate cardiac muscle cells from one another.
 The electrical resistance through the intercalated disks is 1/400degree of the
cardiac cell membrane.
epicardium, myocardium and endocardium.
is serous layer covering the heart, myocardium is made up of cardiac
endocardium is a single layer of
endothelial cells lining the inner surface of the heart.
fibers with centrally located nucleus. The
are connected by intercalated disks. These are cell membranes
that separate cardiac muscle cells from one another.
The electrical resistance through the intercalated disks is 1/400degree of the

22.  The intercalated disks contains gap junctions.
 The gap junctions between the adjacent
passage ofions.
 Because of this presence of low resistance bridges, cardiac muscle
as a single unit. It is termed as functional
 The desmosomes in the disk provide site for adhesion between two cardiac
muscle cells.
 These adhesions helps to transmit the tension developed in one cell to other
during contraction.
The intercalated disks contains gap junctions.
The gap junctions between the adjacent fibers offer low resistance to the
Because of this presence of low resistance bridges, cardiac muscle fibers contract
as a single unit. It is termed as functional syncytium.
in the disk provide site for adhesion between two cardiac
These adhesions helps to transmit the tension developed in one cell to other

23.  Two atriaor two ventricels contract simultaneously as a single unit.
 The cardiac muscle has the contractile roteins
sarcomere.
 It has the characteristics A-, I-, and H bands with M
 In the cardiac muscle, the sarcoplasmic reticulum is not well formed.
 T- tubules is wider and located at the Z-line unlike the A
muscle.
contract simultaneously as a single unit.
roteins actin and myosin arranged in a
, and H bands with M- and Z-lines.
reticulum is not well formed.
line unlike the A-I junction in the skeletal

24. CONDUCTING SYSTEM
OF HEART
CONDUCTING SYSTEM
OF HEART

25.  The conducting systemof heart consists of
sinoatrial node.
atrioventricular node.
Bundle of His.
Right and left bundle branches.
Purkinje fibers.
heart consists of
Right and left bundle branches.

26.  SINOATRIAL NODE:
 The SA node is a specialized cardiac tissue present at the junction of the superior vena
cava and the right atrium.
 It generates maximum number of impulses (70
Hence, it is called pacemaker of the heart.
 ATRIOVENTRICULAR NODE:
 The AV node is present between the atrium and the ventricle close to the AV opening. It
can produce 50-60 impulses/min. It is connected to the SA node by mean of
pathways.
 It conducts the impulse generated by the SA node.
The SA node is a specialized cardiac tissue present at the junction of the superior vena
It generates maximum number of impulses (70-80/min) and sets the pace for the heart.
The AV node is present between the atrium and the ventricle close to the AV opening. It
60 impulses/min. It is connected to the SA node by mean of internodal
It conducts the impulse generated by the SA node.

27.  BUNDLE OF His:
 The AV node continues as the bundle of His. It gives out a left bundle branch and
continues as the right bundle branch. The left bundle branch divides into the anterior
and posterior divisions.
 It supplies the left ventricle and interventricular
supplies the right ventricle.
 PURKINJE FIBERS:
 These are specialized myocardial cells with gap junctions. They form network in both the
ventricles and transfer impulses from the bundle branches to the working myocardium.
 Purkinje fibers can generate about 15-40 impulses/min.
The AV node continues as the bundle of His. It gives out a left bundle branch and
continues as the right bundle branch. The left bundle branch divides into the anterior
interventricular septum. The right bundle branch
These are specialized myocardial cells with gap junctions. They form network in both the
ventricles and transfer impulses from the bundle branches to the working myocardium.
40 impulses/min.

28. PROPERTIES OF
CARDIAC MUSCLE,
CARDIAC CYCLE, HEART
BEAT
PROPERTIES OF
CARDIAC MUSCLE,
CARDIAC CYCLE, HEART

29. PROPERTIES OF CARIAC MUSCLE
 1. Rhythmicity
 2. Excitability
 3. Conductivity
 4. Contractility
PROPERTIES OF CARIAC MUSCLE

30. Rhythmicity
 Rhythmicity means the ability of the heart to beat regularly without external stimulation.
 It is myogenic in origin not neurogenic The nodal fibres and conducting system are
selfexcitable.
 Sinoatrial node (SAN)→110 b/min
 Atrioventricular node (AVN)→ 90
 Bundle of His (A-V bundle) → 45
 Purkinje fibres → 35
 Ventricular fibres → 25
 The cells of SAN; (posterior wall of right atrium) is the primary pacemaker of the heart
means the ability of the heart to beat regularly without external stimulation.
The nodal fibres and conducting system are
The cells of SAN; (posterior wall of right atrium) is the primary pacemaker of the heart

31. Excitability
 The heart muscle responds to stimuli which may be mechanical, electrical or
chemical
The heart muscle responds to stimuli which may be mechanical, electrical or

32. Conductivity
 The ability to conduct impulse from one cell to another
presence of gap junctions that transmit electrical currents.
 From SAN→ atrial muscle & atrioventricular
 From AVN (slowest) → atrioventricular (AV) bundle (bundle of His) →le & right
bundles →purkinje fibres (fastest)
The ability to conduct impulse from one cell to another--- facilitated by the
presence of gap junctions that transmit electrical currents.
atrioventricular node (AVN)
(AV) bundle (bundle of His) →le & right

33. Refractory Period
 The refractory period of the myocardial
that of skeletal muscle fibers and lasts approximately as long as the cardiac
contraction. so no continous contraction without relaxation (tetanus) can occur
in heart.
The refractory period of the myocardial fibers is of much longer duration than
and lasts approximately as long as the cardiac
contraction without relaxation (tetanus) can occur

34. RULES CONTROLLING CONTRACTILITY
 ALL OR NONE LAW:
 The cardiac muscle contracts either maximally or not at all (under constant
conditions)
 The Atria contract as one unit & the ventricles contract as one unit
 This is significant for efficient pumping of the blood.
RULES CONTROLLING CONTRACTILITY
The cardiac muscle contracts either maximally or not at all (under constant
The Atria contract as one unit & the ventricles contract as one unit
This is significant for efficient pumping of the blood.

35. RULES CONTROLLING CARDIAC CONTRACTILITY
 2- Staircase or Treppe Phenomenon
 Rapidly Repeated stimulation of the cardiac muscle produce gradual increase in
the strength of contraction
 The earlier contractions produce better conditions (heat, less viscosity between
muscle fiber, more Ca) for the following contraction.
RULES CONTROLLING CARDIAC CONTRACTILITY
Rapidly Repeated stimulation of the cardiac muscle produce gradual increase in
The earlier contractions produce better conditions (heat, less viscosity between
, more Ca) for the following contraction.

36.  STARLING LAW:
 Within limits, the greater the initial length of cardiac muscle fibre (stretch), the
greater the force of contraction
 The initial length is determined by the volume of blood filling ventricles at end of
diastole (end-diastolic volume; EDV).
Within limits, the greater the initial length of cardiac muscle fibre (stretch), the
The initial length is determined by the volume of blood filling ventricles at end of

37. CARDIAC CYCLE
 The term cardiac cycle refers to the events of one complete heartbeat, during
which both atria and ventricles contract and then relax.
 The average heart beats approximately 75 times per minute, so the length of the
cardiac cycle is normally about 0.8 second.
The term cardiac cycle refers to the events of one complete heartbeat, during
which both atria and ventricles contract and then relax.
The average heart beats approximately 75 times per minute, so the length of the
about 0.8 second.

38.  Atrial diastole (ventricular filling): Our discussion begins with the heart
completely relaxed. Pressure in the heart is low, the AV valves are open, and
blood is flowing passively through the atria into the ventricles. The
valves are closed.
 Atrial systole: The ventricles remain in diastole as the atria contract, forcing
blood into the ventricles to complete ventricular filling.
 Isovolumetric contraction: Atrial systole
initial rise in intraventricular pressure closes the AV valves, preventing backflow
of blood into the atria. For a moment, the ventricles are completely
chambers.
Our discussion begins with the heart
completely relaxed. Pressure in the heart is low, the AV valves are open, and
blood is flowing passively through the atria into the ventricles. The semilunar
The ventricles remain in diastole as the atria contract, forcing
ventricles to complete ventricular filling.
systole ends, and ventricular systole begins. The
pressure closes the AV valves, preventing backflow
of blood into the atria. For a moment, the ventricles are completely closed

39.  Ventricular systole (ejection phase): The ventricles
the intraventricular pressure to surpass the pressure in the major arteries leaving
the heart. This causes the semilunar valves to open and blood to be ejected from
the ventricles. During this phase, the atria are again relaxed and filling with
blood.
 Isovolumetric relaxation: As ventricular diastole
ventricles falls below that in the major arteries, and the
prevent backflow into the ventricles. For another moment, the ventricles are
completely closed chambers and intraventricular
Meanwhile, the atria have been in diastole, filling with blood. When
pressure increases above intraventricular
cycle repeats.
The ventricles continue to contract, causing
pressure to surpass the pressure in the major arteries leaving
valves to open and blood to be ejected from
the ventricles. During this phase, the atria are again relaxed and filling with
As ventricular diastole begins, the pressure in the
ventricles falls below that in the major arteries, and the semilunar valves close to
prevent backflow into the ventricles. For another moment, the ventricles are
intraventricular pressure continues to decrease.
Meanwhile, the atria have been in diastole, filling with blood. When atrial
intraventricular pressure, the AV valves open, and the

40. HEART BEAT
 Heart sounds are often described by the two
sequence is lub-dup, pause, lub-dup, pause, and so on.
 The first heart sound (lub) is caused by the closing of the AV valves.
 The second heart sound (dup) occurs when the
of ventricular systole.
 The first heart sound is longer and louder than the second heart sound, which
tendsto be short and sharp.
Heart sounds are often described by the two syllables “lub” and “dup,” and the
dup, pause, and so on.
) is caused by the closing of the AV valves.
The second heart sound (dup) occurs when the semilunar valves close at the end
The first heart sound is longer and louder than the second heart sound, which

41. BLOOD VESSELS,
REGULATION OF HEART
RATE & BLOOD
PRESSURE
BLOOD VESSELS,
REGULATION OF HEART
RATE & BLOOD
PRESSURE

42.  Blood circulates inside the blood vessels, which form a closed transport system
called the vascular system.
 As the heart beats, it propels blood into the large arteries leaving the heart.
 As the large arteries branch, blood moves into successively smaller and smaller
arteries and then into the arterioles which feed the capillary beds in the tissues.
 Capillary beds are drained by venules which in turn empty into veins that merge
and finally empty into the great veins (venae
Blood circulates inside the blood vessels, which form a closed transport system
As the heart beats, it propels blood into the large arteries leaving the heart.
As the large arteries branch, blood moves into successively smaller and smaller
arteries and then into the arterioles which feed the capillary beds in the tissues.
Capillary beds are drained by venules which in turn empty into veins that merge
and finally empty into the great veins (venae cavae) entering the heart.

43. BLOOD VESSEL:
 The walls of blood vessels have three layers, or tunics :
 Tunica intima
 Tunica media
 Tunica externa
The walls of blood vessels have three layers, or tunics :

44.  The tunica intima which lines the lumen, or interior, of the vessels, is a thin layer
of endothelium (squamous epithelial cells) resting on a basement membrane. Its
cells fit closely together and form a slick surface that decreases friction as blood
flows through the vessel lumen
 The tunica media is the bulky middle layer, made up mostly of smooth muscle
and elastic fibers. Some of the larger arteries have elastic laminae, sheets of
elastic tissue, in addition to the scattered elastic fibers.
 The tunica externa is the outermost tunic. This layer is composed largely of
fibrous connective tissue, and its function is to support and protect the vessels.
The tunica intima which lines the lumen, or interior, of the vessels, is a thin layer
of endothelium (squamous epithelial cells) resting on a basement membrane. Its
cells fit closely together and form a slick surface that decreases friction as blood
The tunica media is the bulky middle layer, made up mostly of smooth muscle
and elastic fibers. Some of the larger arteries have elastic laminae, sheets of
elastic tissue, in addition to the scattered elastic fibers.
The tunica externa is the outermost tunic. This layer is composed largely of
fibrous connective tissue, and its function is to support and protect the vessels.

45.  Artery walls are thick and strong to withstand blood pressure fluctuations. They
expand and recoil as the heart beats.
 Vein walls are thinner, their lumens are larger, and they are equipped with valves.
These modifications reflect the low pressure of the blood flowing in veins.
 Capillary beds have two types of vessels
Blood flow into true capillaries is controlled by precapillary sphincters. Exchanges
with tissue cells occur across the walls of the true capillaries. When the
precapillary sphincters are closed, blood flows directly through the vascular
shunt
Artery walls are thick and strong to withstand blood pressure fluctuations. They
Vein walls are thinner, their lumens are larger, and they are equipped with valves.
These modifications reflect the low pressure of the blood flowing in veins.
Capillary beds have two types of vessels—a vascular shunt and true capillaries.
Blood flow into true capillaries is controlled by precapillary sphincters. Exchanges
with tissue cells occur across the walls of the true capillaries. When the
precapillary sphincters are closed, blood flows directly through the vascular

47. BLOOD PRESSURE:
 Blood pressure is the pressure the blood exerts against the inner walls of the
blood vessels, and it is the force that keeps blood circulating continuously even
between heartbeats.
 Unless stated otherwise, the term blood pressure in this discussion is understood
to mean the pressure within the large systemic arteries near the heart.
Blood pressure is the pressure the blood exerts against the inner walls of the
blood vessels, and it is the force that keeps blood circulating continuously even
Unless stated otherwise, the term blood pressure in this discussion is understood
to mean the pressure within the large systemic arteries near the heart.

48. Factors increasing blood pressure:
Factors increasing blood pressure:

49.  In normal adults at rest, systolic blood pressure varies between 110 and 140 mm
Hg, and diastolic pressure between 70 and 80 mm Hg
considerably from one person to another and cycles over a 24
peaking in the morning.
 What is normal for you may not be normal for your grandfather or your neighbor.
 Blood pressure varies with age, weight, race, mood, physical activity, and
posture.
In normal adults at rest, systolic blood pressure varies between 110 and 140 mm
Hg, and diastolic pressure between 70 and 80 mm Hg—but blood pressure varies
considerably from one person to another and cycles over a 24-hour period,
What is normal for you may not be normal for your grandfather or your neighbor.
Blood pressure varies with age, weight, race, mood, physical activity, and

50. PARTS AND FUNCTIONS
OF LYMPHATIC SYSTEMS
PARTS AND FUNCTIONS
OF LYMPHATIC SYSTEMS

51.  The lymphatic system consists of two semi
 A meandering network of lymphatic vessels
 Various lymphoid tissues and organs scattered throughout the body.
 The lymphatic vessels transport fluids that have escaped from the blood back to
the cardiovascular system.
 The lymphoid tissues and organs house phagocytic cells and lymphocytes, which
play essential roles in body defense and resistance to disease.
The lymphatic system consists of two semi-independent parts:
A meandering network of lymphatic vessels
Various lymphoid tissues and organs scattered throughout the body.
The lymphatic vessels transport fluids that have escaped from the blood back to
The lymphoid tissues and organs house phagocytic cells and lymphocytes, which
play essential roles in body defense and resistance to disease.

53. TYPES OF LYMPHATIC
ORGANS & VESSELS
TYPES OF LYMPHATIC
ORGANS & VESSELS

54. Lymphatics vessels:
 The lymphatic vessels, also called lymphatics, form a one
flows only toward the heart.
 The microscopic lymph capillaries weave between the tissue cells and blood
capillaries in the loose connective tissues of the body and absorb the leaked
fluid.
 Although similar to blood capillaries, lymphatic capillaries are so remarkably
permeable that they were once thought to be open at one end like a straw.
 Like veins of the cardiovascular system, lymphatic vessels are thin walled, and the
larger ones have valves. The lymphatic system is a low
system.
The lymphatic vessels, also called lymphatics, form a one-way system, and lymph
The microscopic lymph capillaries weave between the tissue cells and blood
capillaries in the loose connective tissues of the body and absorb the leaked
Although similar to blood capillaries, lymphatic capillaries are so remarkably
permeable that they were once thought to be open at one end like a straw.
Like veins of the cardiovascular system, lymphatic vessels are thin walled, and the
larger ones have valves. The lymphatic system is a low-pressure, pumpless

55.  Lymph is transported from the lymph capillaries through successively larger
lymphatic vessels, referred to as lymphatic collecting vessels, until it is finally
returned to the venous system through two large ducts in the thoracic region.
 The right lymphatic duct drains lymph from the right arm and the right side of
the head and thorax.
 The large thoracic duct receives lymph from the rest of the body
 Both ducts empty the lymph into the subclavian vein on their own side of the
body.
Lymph is transported from the lymph capillaries through successively larger
lymphatic vessels, referred to as lymphatic collecting vessels, until it is finally
returned to the venous system through two large ducts in the thoracic region.
The right lymphatic duct drains lymph from the right arm and the right side of
The large thoracic duct receives lymph from the rest of the body
Both ducts empty the lymph into the subclavian vein on their own side of the

56. Lymph nodes:
 In addition to returning tissue fluid to circulation, the lymphatic system plays a
major role in immunity.
 Cells in lymph nodes in particular help protect the body by removing foreign
material such as bacteria and tumor cells from the lymphatic stream and by
producing lymphocytes that function in the immune response.
 Within the lymph nodes are macrophages which engulf and destroy bacteria,
viruses, and other foreign substances in the lymph before it is returned to the
blood.
In addition to returning tissue fluid to circulation, the lymphatic system plays a
Cells in lymph nodes in particular help protect the body by removing foreign
material such as bacteria and tumor cells from the lymphatic stream and by
producing lymphocytes that function in the immune response.
Within the lymph nodes are macrophages which engulf and destroy bacteria,
viruses, and other foreign substances in the lymph before it is returned to the

57.  Lymph nodes are just one of the many types of lymphoid organs in the body.
 Others include the
 Spleen
 Thymus
 Tonsils
 Peyer’s patches
 Appendix
 All these organs have a predominance of reticular connective tissue and lymphocytes.
 Although all lymphoid organs have roles in protecting the body, only the lymph nodes
filter lymph.
Lymph nodes are just one of the many types of lymphoid organs in the body.
All these organs have a predominance of reticular connective tissue and lymphocytes.
Although all lymphoid organs have roles in protecting the body, only the lymph nodes

58. Spleen:
The spleen is a soft organ located in the left side of the abdominal cavity, just beneath the
diaphragm, that curls around the anterolateral aspect of the stomach.
nstead of filtering lymph, the spleen filters and cleanses blood of bacteria, viruses, and other de
The spleen provides a site for lymphocyte proliferation and immune surveillance, but its most
mportant function is to destroy worn-out red blood cells and return some of their breakdown
products to the liver.
Other functions of the spleen include storing platelets and acting as a blood reservoir (like the liv
n the fetus, the spleen is an important hematopoietic (blood cell
adult spleen produces only lymphocytes.
The spleen is a soft organ located in the left side of the abdominal cavity, just beneath the
diaphragm, that curls around the anterolateral aspect of the stomach.
nstead of filtering lymph, the spleen filters and cleanses blood of bacteria, viruses, and other de
The spleen provides a site for lymphocyte proliferation and immune surveillance, but its most
out red blood cells and return some of their breakdown
Other functions of the spleen include storing platelets and acting as a blood reservoir (like the liv
n the fetus, the spleen is an important hematopoietic (blood cell–forming) site, but as a rule the

59. Tonsils:
 The tonsils are small masses of lymphoid tissue deep to the mucosa surrounding
the pharynx (throat).
 Their job is to trap and remove bacteria or other foreign pathogens entering the
throat.
 They carry out this function so efficiently that sometimes they become
congested with bacteria and become red,swollen
tonsillitis.
The tonsils are small masses of lymphoid tissue deep to the mucosa surrounding
Their job is to trap and remove bacteria or other foreign pathogens entering the
They carry out this function so efficiently that sometimes they become
red,swollen, and sore, a condition called

60.  The thymus, which functions at peak level only during youth, is a lymphoid mass
found in the anterior mediastinum overlying the heart.
 Peyer’s patches, which resemble tonsils, are found in the wall of the distal small
intestine.
 Lymphoid follicles are also located in the wall of the appendix
 The macrophages of Peyer’s patches and the appendix are in an ideal position to
capture and destroy harmful bacteria thereby preventing them from penetrating
the intestinal wall
The thymus, which functions at peak level only during youth, is a lymphoid mass
found in the anterior mediastinum overlying the heart.
Peyer’s patches, which resemble tonsils, are found in the wall of the distal small
Lymphoid follicles are also located in the wall of the appendix
The macrophages of Peyer’s patches and the appendix are in an ideal position to
capture and destroy harmful bacteria thereby preventing them from penetrating

61.  Peyer’s patches, the appendix, and the tonsils are part of the collection of small
lymphoid tissues referred to as mucosa-
 Collectively, MALT acts as a sentinel to protect the upper respiratory and
digestive tracts from the constant attacks of foreign matter entering those
cavities.
Peyer’s patches, the appendix, and the tonsils are part of the collection of small
-associated lymphoid tissue (MALT).
Collectively, MALT acts as a sentinel to protect the upper respiratory and
digestive tracts from the constant attacks of foreign matter entering those