circulatory system

1. Chapter 8
Circulatory system
Lecture note
March, 2016

2. Functions of Circulatory system
• A highly effective means of transporting materials within the body.
1. Transportation
• To tissue cells oxygen and nutrients
• From tissue cells metabolic wastes
• Regulatory hormones target organs and cells
2. Protection
• From foreign substances by white blood cells
• Clotting of blood

3. Major Components Circulatory System
1) The cardiovascular system
• Consists of the heart and blood vessels
2) The lymphatic system
• Consists of lymph nodes and lymphatic vessels

4. Cardiovascular system
• The cardiovascular system consists of three interrelated components:
blood, the heart, and blood vessels.
• Blood is a connective tissue composed of a liquid extracellular matrix
called blood plasma that dissolves and suspends various cells and cell
fragments.
• Interstitial fluid is the fluid that bathes body cells and is constantly
renewed by the blood.

5. Blood Components
(1) blood plasma, a watery liquid
extracellular matrix that contains
dissolved substances
2) formed elements, which are cells and
cell fragments.
• If a sample of blood is centrifuged
(spun) in a small glass tube, the cells
sink to the bottom of the tube while
the lighter-weight plasma forms a layer
on top (Figure)
• Blood is about 45% formed elements
and 55% blood plasma.

8. THE HEART
• The heart is relatively
small in relation to its
function
• Roughly the same size
(but not the same
shape) as your closed
fist.
• The heart lies in the
mediastinum between
the lungs (thoracic
cavity)
• About two-thirds of
heart lies to the left of
the body’s midline
The cone shaped heart has an apex and base:
1. The apex is formed by the tip of the left ventricle
and is directed anteriorly, inferiorly, and to the
left.
2. The base is its posterior surface. It is formed by the
atria (upper chambers) of the heart, mostly the left
atrium.

9. Mediastenum
Cross-section of the thorax
Subdivisions of
mediastenum

10. Figure: Structure of the heart: surface features.
Sulci are grooves that contain blood vessels and fat and mark the
external boundaries between the various chambers.

11. Figure: Posterior external view showing surface features
The coronary sulcus forms an external boundary between which chambers of the
heart?

12. Chambers of the Heart
• The heart has four chambers. The two superior receiving chambers are the atria,
and the two inferior pumping chambers are the ventricles.
• On the anterior surface of each atrium is a wrinkled pouchlike structure called an
auricle, so named because of its resemblance to a dog’s ear (Figure 20.3). Each
auricle slightly increases the capacity of an atrium so that it can hold a greater
volume of blood.
• Also on the surface of the heart are a series of grooves, called sulci (SUL-se¯), that
contain coronary blood vessels and a variable amount of fat. Each sulcus (SULkus)
marks the external boundary between two chambers of the heart.
• The deep coronary sulcus encircles most of the heart and marks the external
boundary between the superior atria and inferior ventricles.
• The anterior interventricular sulcus is a shallow groove on the anterior surface of
the heart that marks the external boundary between the right and left ventricles.
This sulcus continues around to the posterior surface of the heart as the posterior
interventricular sulcus, which marks the external boundary between the
ventricles on the posterior aspect of the heart (Figure

13. Figure: Structure of the heart:
surface features.
Sulci are grooves that contain
blood vessels and fat and mark
the external boundaries
between
the various chambers.

14. Figure: Sulci of the heart. A. Anterior surface of the heart. B. Posterior surface of the
heart

15. Cardiopulmonary Resuscitation
• In cases in which the heart suddenly stops beating, cardiopulmonary
resuscitation (CPR)—properly applied cardiac compressions, performed
with artificial ventilation of the lungs via mouth-to-mouth respiration—
saves lives.
• CPR keeps oxygenated blood circulating until the heart can be restarted.

16. Pericardium
• The membrane that surrounds and protects the heart is the pericardium.
• The pericardium consists of two main parts::
1. Fbrous pericardium, sack-like membrane
1. Serous pericardium,.
a. The outer parietal layer of the serous pericardium
b. The inner visceral layer of the serous pericardium or (epicardium)
• Between the parietal and visceral layers is pericardial fluid,
• Pericardial space
• N.B. Inflammation of the pericardium is called pericarditis

17. Layers of the heart wall
• The wall of the heart consists of three layers:
1. Epicardium --external layer
2. Myocardium(middle layer), --95% of the heart pumping action
3. Endocardium(inner layer) endothelial layer
• The innermost endocardium is a thin layer of endothelium
i) provides a smooth lining for the chambers of the heart and covers the
valves of the heart.
ii) It is continuous with the endothelial lining of the large blood vessels

18. Chambers of the heart
• The heart has four chambers.
1. The two superior receiving chambers are the atria
• Right atrium
• Left atrium
2. The two inferior pumping chambers are the ventricles.
• Right ventricle
• Left ventricle

19. External surface of heart
• Grooves or Sulci of the heart indicate the margins of heart chambers
externally.
1. Coronary sulcus
2. Anteriorinterventricularsulcus
3. Posterior interventricularsulcus

21. Forms the right border
of the heart
Receives blood from
three veins: the
superior vena cava,
inferiorvena cava, and
coronary sinus
interatrial septum--–
partiton between right
and left atria
Fosaovalis--- a
depression
Tricuspid valve (right
atrioventricular
valve)—prevents
backflow of blood
Right Atrium
Figure: Internal view of right atrium.
The valves of the heart are composed of dense
connective tissue covered by endocardium.

22. Figure: Internal view of the right ventricle
The right ventricle forms
most of the anterior
surface of the heart.
The inside of the right
ventricle contains
trabeculaecarneae
(raised cardiac muscles)
and chordaetendinae
The interventricular
septum, partition
between right and left
ventricles
Pulmonaryvalve
(pulmonary semilunar
valve) pulmonary trunk,
Right Ventricle
Pulmonary trunk divides into right and left pulmonaryarteries that
transport deoxygenated to the right and left lungs, respectively.

23. Left atrium
The left atrium is
about the same
thickness as the right
atrium and forms
most of the base of
the heart
It receives blood
from the lungs
through four
pulmonary veins.
Bicuspid (mitral)
valve or left
atrioventricular valve
–prevents backflow
of blood

24. Figure: Internal view of the left ventricle
The left ventricle is the
thickest chamber of
the heart, and forms
the apex of the heart.
Contains
trabeculaecarneae and
has chordaetendinae
Blood passes through
aortic valve (aortic
semilunarvalve) to the
ascending
aorta
Aorta parts: ascending,
arch of aorta ,
descending aorta
Ligamentumarteriosu
m—remnant of fetal
ductusarteriosus.
Left Ventricle
Ascending aorta branches: right and left
coronary arteries.

26. Coronary circulation
• The myocardium is supplied with the blood by the right and left cornoray
arteries.
• Two branches of left coronary a. are:
1) Anterior interventricular a. serves the ventricles
2) Cicumflex a. serves the left atrium and left ventricle
• Two branches of right coronary a. are:
1) Posterior interventricular a. supplies ventricles
2) Right marginal branch supplies right atrium and right ventricle
• N.B. Occulsion of coronary a. is the most common type of heart attack

27. Figure: Sulci of the heart. A. Anterior surface of the heart. B. Posterior surface of the
heart

28. Conduction system of the heart
• Cardiac muscle has an intrinsic rythmcity
• The conduction system enables the cardiac cycle /filling and emptying of
the chambers/
• The components of the conduction system are:
1. Sinoatrial node (SA node), or pace maker
2. Atrioventricular node (AV node)
3. Atrioventrivular bundle (bundle of His)
4. Conduction myofibers (Purkinji fibers) spread within the ventricular walls
• The SA and AV nodes also have both sympathetic innervation.

29. Figure: Conduction system of the heart. A. Right chambers. B. Left chambers.

30. Types of blood vessels
• The five main types of blood vessels are arteries, arterioles, capillaries,
venules, and veins
• Arteries carry blood away from the heart to other organs.
i) Large, elastic arteries leave the heart and divide into medium-sized,
muscular arteries that branch out into the various regions of the body.
ii) Medium-sized arteries then divide into small arteries, which in turn divide
into still smaller arteries called arterioles (ar-TE¯ R-e¯-o¯ls).
iii) As the arterioles enter a tissue, they branch into numerous tiny vessels called
capillaries (KAP-i-lar-e¯z hairlike).
• The thin walls of capillaries allow the exchange of substances between the
blood and body tissues.
iv) Groups of capillaries within a tissue reunite to form small veins called
venules (VEN-u¯ ls). These in turn merge to form progressively larger blood
vessels called veins.
V) Veins (VA¯ NZ) are the blood vessels that convey blood from the tissues
back to the heart.

31. Walls of blood vessels
1. Tunica externa
2. Tunica media /smooth muscle/
3. Tunica intima /endothelium/
• -- Arteries have more muscles than same sized veins.
• -- Veins serve as reservoirs or capacitance vessels because
they can strech, when they receive more blood.
• Many veins have venous valves that direct blood to the
heart but arteries do not have valves.

32. Figure. Comparative
structure of blood vessels.
The capillary in (c) is enlarged
relative to the structures
shown in
parts (a) and (b).
Arteries carry blood
from the heart to
tissues; veins carry
blood from tissues to
the heart.

33. Principal Arteries of the Body
1. Aorta—3 parts (ascending, arch of aorta, descending)
2. Arteries of the Head and Neck/ common carotid artery and vertebral arteries/
3. Arteries of the Upper Limb
• subclavian a. _____ axillary a. --------- brachial a. ------ radial and ulnar aa.
• Anastomosis of the radial and ulnar arteries in the palm forms the palmar arch
that gives digital branches to the fingers.
4. The thoracic aorta and its branches
– visceral branches, and parietal branches (posterior intercostal arteries --)
5. The abdominal aorta and its branches---
Unpaired branches
• Celiac trunk --- foregut
• Superior mesenteric --- midgut
• Inferior mesenteric ---- hindgut
Paired branmches
• Right and left renal arteries; Gonadal arteries; Inferiorpherenic arteries; Lumbar
arteries

34. Cross sections of small
arteries. B: A small artery
with a distinctly stained
internal elastic lamina
(arrowhead). Low
magnification. (From a
preparation of the late G
Gomori.)

35. Figure:
Principal
arteries
of
the
body

36. Cont’d
6. Arteries of the pelvis
-- Branches of internal illiac arteries
7. Arteries of the Lower Limb
• External iliac artery ------ femoral a. -------- popliteal a. ------ anterior tibial
artery and posterior tibial artery.
• Anterior tibial artery --- dorsalis pedis artery to dorsum of the foot
• Posterior tibial a. at the ankle bifurcates into lateral and medial plantar
arteries that supply blood to the sole of the foot.
• Anastomsis of lateral plantar a. with the dorsal pedal a. forms the plantar
arch that gives digital branches to the toes

37. Figure:
descending
aorta

38. Figure:
Principal
arteries
of
the
body

39. PRINCIPAL VEINS OF THE BODY
• A vein receives smaller tributaries
• The veins from all parts of the body converge into superior and inferior
venacavae -------- right atrium.
1. Veins Draining the Head and Neck
– external jugular v. ------- subclavian v.
– internal jugular + subclavian veins = brachiocephalic v.
• The right and left brachiocephalic vv. ------- superior vena cava,
2. Veins of the Thorax
• Superior and inferior venacavae
• Intercostal veins -----azygos system
3. Veins of the Abdomen and Pelvis
• Posterior abdominal wall veins join the azygos vein
• Veins from the kidneys, adrenal glands and gonads directly enter the
inferior vena cava
• Veins from the stomach, intestine, spleen and pancreas ------ hepatic
portal vein ----- hepatic sinusoids ------ hepatic veins -------- inferior vena
cava ------- right atrium.

40. Figure:
Principal
veins
of
the
body

41. Figure:
Hepatic
portal
circulation

42. Veins of the Upper Limb
Superficial and deep
veins
• The deep veins
accompany the
arteries (vena
commitents)
• The superficial veins
include the basilica
and cephalic veins.
• The median cubital
vein connects the
basilic and cephalic
veins at the cubital
fossa of the elbow.
• The median cubital
vein is a frequent site
for venipuncture.
Figure. Superficial veins and lymph
nodes of upper limb

43. Veins of the Lower Limb
• The lower extremities have both superficial and deep veins.
• The right and left common iliac veins unite to form the inferior vena
cava,
• The deep veins course with the deep arteries and have similar names.
• The posterior and anterior tibial veins merge to form the popliteal vein.
• Above the knee, the popliteal vein becomes the femoral vein.
• The femoral vein becomes the external iliac vein as it passes the
inguinal ligament.
• The superficial veins of the lower extremity are the two; the small and
great saphenous veins.

44. Figure: Veins of lower
limb. The veins are
subdivided into
superficial (A and B) and
deep (C and E) groups.

45. The Fetal Circulation
• The circulatory system of a fetus, called the fetal circulation,
exists only in the fetus and contains special structures that
allow the developing fetus to exchange materials with its
mother. It differs from the postnatal (after birth) circulation
because the lungs, kidneys, and gastrointestinal organs do not
begin to function until birth.
• The fetus obtains O2 and nutrients from and eliminates CO2
and other wastes into the maternal blood.
• The exchange of materials between fetal and maternal
circulations occurs through the placenta, which forms inside
the mother’s uterus and attaches to the umbilicus (navel) of
the fetus by the umbilical cord.

46. Fetal circulation cont’d
• The capillary exchange between the maternal and fetal circulation occurs
within the placenta
• The umbilical cord is the connection between the placenta and fetal
umbilicus, it includes one umbilical vein and two umbilical arteries
• Umbilical vein ---- hepatic portal vein ----- ductus venous ------ inferior vena
cava (mix of blood) ---- right atrium ---- foramen ovale ----- left atrium -----
left ventricle ---- systemic circulation ------ internal iliac artery ------ two
umbilical arteries ----- Placenta.
• Superior vena cava ----right ventricle ---- ductus arterous
Important changesof CVS that occur at birth.
• Closure of foramen ovale
• Collapse of umbilical vein and ductousvenouses--ligaments
• Ductus arterous atrophy after six weeks of birth,
• These four structures are not functional after birth.

47. Figure:
Fetal
circulation

48. Lymphatic system
• The lymphatic system consists of the lymphatic vessels, lymph nodes and
lymph.
• The functions of the lymphatic system are basically three fold:
1. It transports excess interstitial (tissue) fluid, which has initially formed as a
blood filtrate back to the blood stream.
2. It serves as the route by which absorbed fat from the intestine is
transported
3. Immunological defense against disease causing agents

49. Lymphatic vessels and capillaries
– Lymph capillaries contain lymph.
– Adequate lymphatic prevents edema
– Lymph is returned to the venous system via two large lymph ducts; the
thoracic duct and right lymphatic duct in the thorax.
– The walls of lymphatic vessels (ducts) are similar to that of veins and
contain valves.

50. Figure: Routes for
drainage of lymph
from lymph trunks
into the thoracic
and right lymphatic
ducts.
All lymph returns
to the bloodstream
through the
thoracic (left)
lymphatic duct
and right
lymphatic duct.

51. Lymph nodes
• Lymph is filtered through the reticular tissue of lymph nodes. The reticular tissue
contains phagocytic cells that help purify the fluid.
• Lymph nodes are small oval bodies enclosed within a capsule.
• Lymphatic nodules within the nodes are the sites of lymphocyte production.
• Lymph nodes usually occur in clusters in some regions of the body. Some of the
principal groups of lymph nodes are:
i) Poplitealand inguinal lymph nodes
ii) Lumbar nodes of the pelvic region
iii) Cubitalandaxillary lymph nodes of the upper extremity
iv) Thoracic lymph nodes of the chest
v) Cervical lymph nodes of the neck
vi) Mesentric (Peyer’s) patches that are large clusters of lymphatic tissue in the
intestine
• The spleen and thymus are lymphoid organs because they produce lymphocytes.

52. The lymphoid organs and
lymphatic vessels are
widely distributed in the
body.
The lymphatic vessels
collect lymph from most
parts of the body and
deliver it to the blood
circulation primarily
through the thoracic duct.

53. Lymphatic
system