PULMONARY AND SYSTEMIC CIRCULATION- - ENGLISH
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PULMONARY AND SYSTEMIC
CIRCULATION-
• The
blood circulation is defined as flow of blood
through blood vessels to
different parts of body. There are four types of blood circulations we study in anatomy and
physiology-
• Pulmonary
circulation.
• Systemic
circulation
• Fetal
circulation (only in fetus)
• Portal circulation.
PULMONARY CIRCULATION-
• Pulmonary
circulation is defined as the circulation of blood from the right ventricle of
the heart to the lungs and back to the left atrium. In other words we can say flow of blood from
heart to lungs and from lungs back to the heart is known as pulmonary
circulation.
• The
pulmonary artery or trunk takes deoxygenated blood from the upper part of the right ventricle of
the heart. It passes upwards and divides into left and right pulmonary arteries
at the level of the 5th thoracic vertebra.
• The
left pulmonary artery runs to the root of the left lung where it divides
into two branches, one enters into each lobe carrying deoxygenated blood.
• The
right pulmonary artery passes to the root of the right lung and divides
into two branches. The larger branch carries blood to the middle and lower
lobes, and the smaller branch to the upper lobe.
• Within
the lung these arteries divide and subdivide into smaller arteries, arterioles
and capillaries. The exchange of gases takes place between capillary blood and
air in the alveoli of the lungs . In each lung the capillaries containing oxygenated
blood join up and eventually form two pulmonary veins. Two pulmonary veins come
out of each lung, returning oxygenated blood to the left atrium of the heart.
SYSTEMIC CIRCULATION
The blood pumped out from the left ventricle of
heart is carried by the branches of the aorta
around the body and returns to the right atrium of the heart by the
superior and inferior vena cava. This flow of blood is known as systemic
circulation
Aorta is the first artery of systemic circulation which
takes oxygenated blood . Aorta has two parts one is thoracic aorta and second
is abdominal aorta.
Thoracic aorta is further divided into ascending aorta,
arch of aorta and descending aorta.
Ascending aorta - This is the first part of aorta that starts from left ventricle of the heart. It is about 5 cm
long . The right and left coronary arteries are its only branches which
supply oxygen and nutrients to the myocardium.
Arch of aorta - it is a continuation of the
ascending aorta. It give rises to three branches -
• brachiocephalic
artery
• left
common carotid artery
• left
sub-clavian artery.
Descending aorta - This part of the aorta is
continuous with the arch of the aorta and begins at the level of the 4th
thoracic vertebra. It extends downwards
to the level of the 12th thoracic vertebra, where it passes behind the
diaphragm to become the abdominal aorta.
CIRCULATION OF BLOOD TO HEAD AND NECK-
left and right common carotid arteries and left and right
vertebral arteries supply to the head and neck. The right common carotid artery
is a branch of the brachiocephalic artery. The left common carotid
artery arises directly from the arch of the aorta. They pass upwards on
either side of the neck and have the same distribution on each side.
At the level of the upper border of the thyroid cartilage
each common carotid artery divides into an internal carotid artery and
an external carotid artery. The carotid sinuses are slight
dilations at the point of division (bifurcation) of the common carotid arteries
into their internal and external branches.
EXTERNAL CAROTID ARTERY-This artery supplies the
superficial tissues of the head and neck, via a number of branches:
• The
superior thyroid artery supplies the thyroid gland and nearby muscles.
• The
lingual artery supplies the tongue, the mucus membrane of the mouth, the tonsil
and the epiglottis.
• The
facial artery passes outwards over the mandible just in front of the angle of
the jaw and supplies the muscles of facial expression and structures in the mouth.
• The
occipital artery supplies the posterior part of the scalp.
• The
temporal artery passes upwards over the zygomatic process in front of the ear
and supplies the frontal, temporal and parietal parts of the scalp. The pulse
can be felt in front of the upper part of the ear.
• The
maxillary artery supplies the muscles of mastication and a branch of this
artery,
• The
middle meningeal artery, runs deeply to supply structures in the interior of
the skull.
INTERNAL CAROTID ARTERY-This is
one of the artery which forms the circulus arteriosus (circle of Willis) which supplies the greater part of the brain.
It also has branches that supply the eyes, forehead and nose. Four large
arteries contribute to the formation of circle of willies : the two internal
carotid arteries and the two vertebral arteries. The vertebral arteries
arise from the subclavian arteries, pass upwards through the foramina in the
transverse processes of the cervical vertebrae, enter the skull through the
foramen magnum, then join to form the basilar artery.
CIRCLE OF WILLIS
• Basilar
artery further divides into two left and right posterior cerebral
arteries which take part in formation of circle of willies. Both
internal carotid arteries divides into anterior cerebral artery and middle
cerebral arteries. One anterior communicating artery connects both anterior
cerebral arteries to each other and two
posterior communicating arteries connects middle cerebral artery to posterior
cerebral artery to complete the circle. This circle supply oxygen and nutrition to the brain
parts without interruption.
VENOUS RETURN FROM HEAD AND NECK-
• The
venous blood from the head and neck is returned by deep and superficial
veins.
• Superficial
veins with the same names as the branches of the external carotid artery return
venous blood from the superficial structures of the face and scalp and unite to
form the external jugular vein
• The
external jugular vein begins in the neck at the level of the angle of
the jaw. It goes downwards in front of the sternocleidomastoid muscle, then
behind the clavicle before entering the subclavian vein.
• Left
external jugular vein >>> Left subclavian vein
• Right
external jugular vein >>> Right subclavian vein
• Venous
retrun from deep structures of head are collected by- The superior sagittal
sinus carries the venous blood from the superior part of the brain and later
continues as right transverse sinus. The
inferior sagittal sinus lies deep within the brain and passes backwards to form
the straight sinus. The straight sinus runs backwards and downwards to
become the left transverse sinus. The transverse sinuses turns into sigmoid sinuses and finally continues as the internal jugular vein before
entering the subclavian vein. The vertebral vein also enters into
subclavian vein
• the
subclavian veins enters into the brachiocephalic veins are situated one on each
side in the root of the neck. Both left
and right brachiocephalic veins unite to form the superior vena cava.
The superior vena cava, which drains all the venous blood from the head,
neck and upper limbs, is about 7 cm long. It passes downwards along the right
border of the sternum and ends in the right atrium of the heart.
ARTERIAL SUPPLY TO UPPER ARM-
The right subclavian artery is a division of
brachiocephalic artery; the left subclavian artery comes from the arch of the
aorta. Each subclavian artery divides
into three branches: the vertebral artery, which passes upwards to supply the
brain, the internal thoracic artery,
which supplies the breast and a number of structures in the thoracic cavity
and the axillary arteries. Axillary
artery enters to arm through axilla and becomes brachial artery. Brachial
artery runs down the medial aspect of the upper arm, passes to the front of the
elbow and extends to about 1 cm below the joint, where it divides into the
radial and ulnar arteries.
The radial artery passes down the radial or lateral side
of the forearm to the wrist. Just above the wrist it lies superficially and can
be felt in front of the radius, as the radial pulse. The ulnar artery runs
downwards on the ulnar or medial aspect of the forearm to cross the wrist and
pass into the hand. There are anastomoses between the radial and ulnar
arteries, called the deep and superficial palmar arches, from which palmar
metacarpal and palmar digital arteries arise to supply the structures in the
hand and fingers.
VENOUS RETURN FROM UPPER LIMB- The veins of the upper
limb are divided into two groups:superficial
and deep veins- The superficial
veins begin in the hand and consist of the following:
• cephalic
vein
• basilic
vein
• median
vein
• median
cubital vein.
The deep veins follow the course of the arteries
and have the same names:
• -palmar
metacarpal veins -deep palmar venous arch
• -ulnar
and radial veins -brachial
vein
• -axillary
vein -subclavian
vein.
ARTERIAL SUPPLY IN THORACIC CAVITY- The descending aorta
is the main artery from which thoracic
cavity gets it arterial blood supply . There are many paired branches which
supply the walls of the thoracic cavity and the organs within the cavity,
including the:
• bronchial
arteries that supply the bronchi and their branches, connective tissue
in the lungs and the lymph nodes at the root of the lungs.
• oesophageal
arteries, supplying the oesophagus
• intercostal
arteries that run along the inferior border of the ribs and supply the
intercostal muscles, some muscles of the thorax, the ribs, the skin and its
underlying connective tissues.
VENOUS RETURN FROM CHEST CAVITY- Most of the venous blood
from the organs in the thoracic cavity is collectd by the azygos vein and the
hemiazygos vein. Some of the main veins that join them are the bronchial,
oesophageal and intercostal veins. The azygos vein joins the superior vena cava
and the hemiazygos vein joins the left brachiocephalic vein >>> superior vena cava .
ARTERIAL SUPPLY TO ABDOMINAL ORGANS- The abdominal aorta
is the main artery which supply oxygenated blood in abdominal cavity. It is a
continuation of the thoracic aorta. It descends in front of the bodies of the
vertebrae to the level of the 4th lumbar vertebra, where it divides into the right
and left common iliac arteries
Branches from the
abdominal aorta supply blood to the abdominal organs. These arteries are
paired (Inferior phrenic arteries ,
Renal arteries, Testicular arteries in males and Ovarian arteries in females)
and unpaired (The coeliac artery, left gastric artery, hepatic artery ,
superior mesenteric artery and inferior mesenteric artery)
VENOUS RETURN FROM ABDOMINAL ORGANS- The portal vein is formed by the union of several veins
(splenic vein , inferior mesenteric vein , superior mesenteric vein , gastric
veins and cystic vein )
The portal vein , testicular, ovarian, renal and adrenal
veins join the inferior vena cava
Inferior vena cava pour deoxygenated blood into right
atrium of the heart
ARTERIAL SUPPLY TO PELVIC CAVITY AND LOWER LIMB-
• In
front of the sacroiliac joint the common iliac artery divides into the internal
and the external iliac arteries.
• The
internal iliac artery supply the organs
within the pelvic cavity.
• The
external iliac artery goes downwards and passes behind the inguinal ligament
into the thigh where it becomes the femoral artery.
• The
femoral artery supplies blood to
the structures of the thigh and some superficial pelvic and inguinal
structures. After popliteal space it becomes popliteal artery. It supplies the
structures in this area, including the knee joint. At the lower border of the
popliteal fossa it divides into the anterior and posterior tibial arteries.
• The
anterior tibial artery passes forwards between the tibia and fibula and
supplies the structures in the front of the leg. At lower end it is continuous
as the dorsalis pedis artery which contributes to the formation of the
plantar arch.
• The
posterior tibial artery runs
downwards and medially on the back of the leg,
it gives off a large branch called the peroneal artery, which
supplies the lateral aspect of the leg. At lower end it continues as the plantar
artery that supplies the structures in the so le of the foot. This
artery, its branches and the dorsalis pedis artery form the plantar arch, from
which the digital arteries arise to supply the toes.
VENOUS RETURN FROM PELVIC CAVITY AND LOWER LIMB-
The two main superficial veins draining blood from the
lower limbs are the small and the great saphenous veins. The small saphenous
vein begins behind the ankle joint where many small veins which drain the
dorsum of the foot join together. It ascends superficially along the back of
the leg and in the popliteal space it joins the popliteal vein . The great
saphenous vein is the longest vein in the body. It begins at the
medial half of the dorsum of the foot
and runs upwards, crossing the medial aspect of the tibia and up the inner side
of the thigh. Just below the inguinal ligament it joins the femoral vein.
• There
are both deep and superficial veins in the lower limb . Blood entering the
superficial veins passes to the deep veins through communicating veins.
The deep veins accompany the arteries and their branches and have the same
names. They are the: femoral vein,
external iliac vein , internal
iliac vein , common iliac vein.
• Left
and right common iliac arteries join to form the inferior vena cava.
Inferior vena cava pour deoxygenated blood into right atrium of the heart
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