Blood Vessels and You
Blood vessels – in general
Arteries – carry blood away from heart to supply tissues; have thicker walls
Veins – drain tissues, return blood toward heart; have thinner walls, valves
Capillaries – microscopic, thin; exchange nutrients, gases, wastes between blood and tissues
→ a closed system of tubes transporting blood (the body’s main transportation medium for nutrients, gases, wastes, etc.) between the heart and the body’s tissues
→ along with the heart, they make up the circulatory system
Systemic vs. pulmonary circulation (a review)…
Systemic arteries branch from the aorta and carry oxygen-rich blood from the left ventricle to the capillaries of all body tissues, serving their metabolic needs; systemic veins drain oxygen-poor blood from these tissues to the right atrium.
Pulmonary arteries branch from the pulmonary trunk and carry oxygen-poor blood from the right ventricle to the capillaries of the lungs for gas exchange with inspired air; pulmonary veins drain oxygen-rich blood from the lungs to the left atrium.
→ note that the pulmonary circulation is the exception to the general rule that arteries carry O2-rich blood and veins carry O2-poor blood
Systemic arteries – upper body
Aortic arch – from left ventricle; its branches supply head and upper extremities
Brachiocephalic artery (brachiocephalic trunk) – first visible branch off aortic arch; divides into the:
Right common carotid artery (supplying right side of neck/head/ brain) and the
Right subclavian artery (supplying right shoulder and arm)
Left common carotid artery – arises directly from aortic arch
Left subclavian artery – immediately to left of left common carotid artery
Axillary arteries – continuations of subclavian arteries through armpits
Brachial arteries – continuations of axillary arteries through upper arm region
Descending aorta – after the aortic arch the aorta continues down into the thoracic cavity
Aortic arch
Arterial supply to brain�
The common carotid artery on either side of neck divides to form:
Vertebral arteries arise from subclavian arteries and also supply the brain
Note that the brain is supplied by two sources:
Internal carotid arteries
Vertebral arteries
Arterial supply to brain�
Circle of Willis – an arterial anastomosis (convergence) of certain branches of the internal carotids, theoretically providing alternative pathways for blood to reach the brain
Abdominal arteries
Descending (abdominal) aorta – its branches supply the abdomen, pelvis, and lower extremities
Celiac trunk – immediately branches to supply liver, stomach, spleen, pancreas, and part of small intestine
Abdominal arteries
Superior mesenteric artery – supplies most of small intestine and first half of large intestine
Inferior mesenteric artery – supplies distal half of large intestine
Renal arteries – supply kidneys
The descending aorta divides into 2 common iliac arteries – supply pelvis, lower abdominal wall, lower limbs
Abdominal and pelvic arteries
Each common iliac artery divides into internal and external iliac arteries…
Internal iliac artery – supplies gluteal muscles, adductor muscles of thigh, genitalia, perineum
External iliac artery – supplies anterior abdominal wall and lower limb
As the external iliac artery continues into the thigh, it becomes the femoral artery, supplying the leg.
Anterior and posterior tibial A – supply the lower anterior and medial leg.
Fibular A – supplies lateral lower leg
Pelvic and lower limb arteries
Schematic of systemic arterial circulation
Systemic veins – upper body
Superior vena cava – drains head, upper extremities, and torso above the diaphragm into right atrium
Inferior vena cava – drains tissues below the diaphragm into right atrium
Left and right brachiocephalic veins drain head, neck, upper limbs and unite to form superior vena cava
Subclavian veins – drains right shoulder and arm (branch from brachiocephalic vein)
Axillary veins – continuation of subclavian veins through armpits, becoming brachial veins as they pass along the humerus; drain arms
Azygos vein – drains the right side of the thorax into the superior vena cava just above the right atrium; FYI – it is part of the azygos system, which drains the intercostal muscles of the thorax and abdominal wall
Systemic veins – head/neck
External jugular veins – drain blood from face and scalp into the subclavian veins
Internal jugular veins – drains blood from the brain
Abdominal veins
Renal veins – drain kidneys
Gonadal veins – drain ovaries or testes; right gonadal vein drains directly into inferior vena cava, while left gonadal vein drains into left renal vein
The inferior vena cava starts at the junction of the common iliac veins – drain venous blood from legs and pelvis
External iliac veins – receive blood from lower limb and become the femoral veins as they traverse the medial thigh
Great saphenous veins – superficial; the longest veins in the body from the heel up the entire medial side of leg and joins the femoral veins
Veins of the pelvis and lower limb
Schematic of systemic venous circulation
Before it’s allowed to return to the systemic veins, blood from the digestive viscera (stomach and intestines), spleen and pancreas is first delivered to the liver via the hepatic portal vein for processing of nutrients and toxins.
Superior mesenteric vein – receives blood from small intestine and colon and drains into hepatic portal vein
Hepatic veins – drain the processed blood from the liver into the inferior vena cava
Hepatic portal circulation