Circulatory System



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:

• Pectinate muscles on inner wall surface

• Fossa ovales – formerly, foramen ovales inutero

• Oxygen poor blood enters right atrium from three vessels - superior vena cava, inferior vena cava and coronary sinus

Superior vena cava

• Vein that brings blood from superior region of body

• Enters heart at the right atrium

Inferior vena cava

• Vein that brings blood from inferior region of body

• Enter heart at the right atrium

Coronary Sinus

• 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

Right 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

• 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

• 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

• 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

- 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

- right subclavian artery passes under clavicle and is called right axillary artery

- 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

- 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

- left axillary artery descends left upper arm and becomes left brachial artery

- left brachial artery branches into radial and ulnar arteries

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:

• 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:

• 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:

• 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:

• 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:

• External jugular – drains blood from face region

• Internal jugular – returns blood from cranium

• Subclavian vein – returns blood from arm and shoulder region

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