Circulatory System
Two circuits:
Pulmonary circuit – blood travels from heart to lungs back to heart
Systemic circuit – blood travels from heart to body back to heart
Heart and its major vessels:
4 chambers – Right atrium, right ventricle, left atrium, left ventricle
Right atrium:
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Pectinate muscles on inner wall surface
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Fossa ovales – formerly, foramen ovales inutero
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Oxygen poor blood enters right atrium from three vessels - superior vena
cava, inferior vena cava and coronary sinus
Superior vena cava
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Vein that brings blood from superior region of body
Enters heart at the right atrium
Inferior vena cava
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Vein that brings blood from inferior region of body
Enter heart at the right atrium
Coronary Sinus
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Right
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Vein that brings blood from heart muscles
Collects from coronary veins – great cardiac vein and middle cardiac vein
Opening into right atrium inferiorly to inferior vena cava
ventricle:
Oxygen poor blood enters right ventricle from right atrium through flaps
Three flaps form the tricuspid valves (or right atrioventricular (AV) valve)
Chordae tendinae are tendons attached to cusps
Papillary muscles are attached to tendons that help keep cusps in place during
ventricular contraction
Ventricular Contraction
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Cusps close over AV valves passively from blood pushing on them
Papillary muscles contract, pulling on tendons
Papillary muscles/tendons prevent cusps from swinging wide into atria
and allowing back flow of blood
Trabeculae carnae – muscles on ventricle wall that is involved in
ventricular contraction
Blood leaves right ventricle to lungs via the Pulmonary Trunk
Pulmonary Trunk:
 Oxygen poor blood enters into pulmonary trunk through the pulmonaric
semilunar valves
 Pulmonary trunk branches into Right and Left Pulmonary artery
 Right and left pulmonary arteries take blood to right and left lungs,
respectively
 Blood becomes oxygen rich
Oxygen rich blood leaves lungs to left atrium via Pulmonary Veins
Left Atrium
 Receives oxygen rich blood from pulmonary veins
 Lacks pectinate muscles
Left Ventricle
 Oxygen rich blood enters left ventricle from left atrium through flaps
 Two flaps form the bicuspid valves (aka. Left AV valve or mitral valve)
 Chordae tendinae are tendons attached to cusps
 Papillary muscles are attached to tendons that help keep cusps in place during
ventricular contraction
 Works in same fashion as the tricuspid valves
 Also contains trabeculae carnae
Blood leaves left ventricle to body via the Aorta
Aorta and its branches:
Ascending aorta
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First part of aorta leaving heart
Oxygen rich blood enters ascending aorta through aortic semilunar valves
First branches are right and left coronary arteries that feed heart
Right Coronary arteries
supplies blood to right atrium and portions of ventricles
branches into marginal artery and posterior interventricular artery
(blood leaves these areas by the middle cardiac vein to enter coronary
sinus and back to right atrium)
Left Coronary arteries
supplies blood to left ventricle and left atrium
branches into circumflex artery and anterior interventricular artery
(blood leaves these areas by the great cardiac vein to coronary sinus)
Aortic Arch
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Ascending aorta arches and becomes aortic arch
Branches from aortic arch are the brachiocephalic trunk, left common carotid
and left subclavian vein
Brachiocephalic trunk, left common carotid and left subclavian all feed the
head, neck, shoulders and upper limbs
Left common carotid divides into internal and external carotid arteries feeding
the face and cranium, respectively
Brachiocephalic Trunk
from aortic arch
right common carotid branches from it
right common carotid divides into right internal and external
carotid arteries
carotid arteries feeds neck and cranium region
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brachiocephalic trunk is now called right subclavian artery
Right Subclavian arteries
from brachiocephalic trunk
thyrocervical trunk provides blood to neck, shoulder and upper
back
internal thoracic artery provides blood to rib cage
vertebral artery provides blood to brain and spinal cord
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right subclavian artery passes under clavicle and is called right
axillary artery
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right axillary artery descends right upper arm and becomes right
brachial artery (around the area that T. major inserts on
humerus)
right brachial artery divides into the radial and ulnar arteries
right axillary, brachial, radial and ulnar arteries provide blood to the
right upper arm, forearm, and hand
Left common carotid
from aortic arch
divides into the left internal and external carotid arteries
feeds neck and head region
Left subclavian arteries
from aortic arch
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left thyrocervical trunk, internal thoracic artery and vertebral
artery provides blood to the left side of the body (same body parts as
right side)
left subclavian artery passes under clavicle and is called left axillary
artery
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left axillary artery descends left upper arm and becomes left brachial
artery
left brachial artery branches into radial and ulnar arteries
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Descending Aorta
- divided by the diaphragm into abdominal and thoracic descending aorta
Unpaired:
celiac trunk
 divides into the left gastric artery, splenic artery, and common
hepatic artery
 left gastric artery feeds stomach
 splenic artery feeds the spleen
 common hepatic artery feeds liver
superior mesenteric artery
 inferior to celiac branching
 feeds pancreas, duodenum, small intestine and large intestine
inferior mesentery artery
 inferior to superior mesenteric branching
 delivers blood to portions of large intestine and rectum
Paired arteries:
renal arteries
 close to superior mesenteric artery
 right and left renal arteries
 feed right and left kidneys
Gonadal arteries
 between superior mesenteric and inferior mesenteric arteries
 right and left gonadal arteries
 feed gonads (testes in males and ovaries in females)
 in males, called testicular arteries
 in females, called ovarian arteries
Common iliac arteries
 termination of descending aorta
 right and left common iliac arteries
 feed pelvic region and upper thigh
branches of common iliac arteries:
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internal and external iliac arteries
internal iliac arteries supply blood to pelvic, urinary bladder,
external genitalia, and medial side of thigh
external iliac artery becomes femoral artery as is descends down
anterior thigh region
branches of femoral artery:
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femoral artery branches from femoral artery and supplies blood
to deep muscles of thigh
deep femoral artery passes through adductor magnus muscle
(adductor hiatus) and becomes posterior
changes name on posterior side to popliteal artery
branches of popliteal artery:
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branches into the posterior tibial artery and anterior tibial
artery
posterior tibial artery has a branch that runs along fibula bone on
posterior side and is called fibular artery
anterior tibial artery travels between tibia and fibula to become
anterior
branches of popliteal arteries provide blood to skin and muscles of
anterior and posterior portion of leg
INUTERO BYPASSES (in embryo):
To divert more blood to placenta for oxygen (instead of lungs)
1.
Foramen ovales – hole between right and left atria; at birth becomes fossa
ovales
2.
ductus arteriosus – canal between pulmonary trunk and aorta; at birth becomes
ligamentum arteriosum
Blood returning to heart via veins:
Veins of the lower leg, anterior thigh and pelvic region
* each of these have a right and left side
Great saphenous vein – longest vein in body and returns blood from leg
region
anterior tibial vein – goes between tibia and fibula to branch into posterior
tibial vein; brings blood from anterior lower leg
posterior tibial vein – drains blood from posterior lower leg; becomes popliteal
vein when coursing in popliteal region (posterior side)
popliteal vein – travels through adductor hiatus and becomes deep femoral
vein (anterior thigh region)
Deep femoral vein – drains into femoral vein on anterior side
Great saphenous vein – drains into femoral vein on anterior side
Femoral vein – receives blood from great saphenous vein and deep femoral
vein; located in thigh region; drains into the external iliac veins
External Iliac veins – femoral vein becomes external iliac veins in pelvic region
Internal Iliac veins – drain into external iliac veins to become common iliac
veins
Common Iliac veins – internal iliac veins joins external iliac veins and becomes
common iliac vein; right and left side join together to drain into inferior vena
cava
Inferior Vena Cava – Common Iliac veins from right and left lower limb form
together and begin the inferior Vena Cava
Tributaries entering Inferior Vena Cava:
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Common iliac veins- base of inferior vena cava, draining from
thigh and pelvis
Renal veins – draining from kidneys
Gonadal veins – draining from gonads
Hepatic veins – draining from liver
**Veins do not drain directly from digestive tract (eg. intestines, stomach) – they
go through liver first via hepatic portal vein and then enter IVC via hepatic
veins**
Tributaries entering Superior Vena Cava:
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External jugular – drains blood from face region
Internal jugular – returns blood from cranium
Subclavian vein – returns blood from arm and shoulder region