Cardiorespiratory System- Blood Vessels Flashcards
What is the anatomy of blood vessels?
Systemic circulation extends to all body regions, while pulmonary circulation consists of vessels to and from the lungs
- Arteries carry blood away from the heart and become smaller as they branch and lead to capillaries
- Veins return blood to the heart and become progressively larger as they merge and approach the heart
- An anastomosis is the convergence of 2 or more vessels (veins do this more than arteries and end arteries don’t at all)
- Companion vessels are arteries and veins that lie next to each other
What are blood vessel tunics?
- Artery and vein wall have 3 layers:
1. Tunica intima: composed of endothelial and subendothelial layer areolar connective tissue
2. Tunica media: Composed of circularly arranged smooth muscle (sympathetic makes smooth muscle contract resulting in vasoconstriction)
3. Tunica externa: outer connective tissue that helps anchor blood vessels to their surroundings - Capillary walls contain only tunica intima
What are arteries?
- Transport blood away from the heart
- 3 types: elastic, muscular and arterioles
What are elastic arteries?
- Largest arteries
- Walls contain many elastic fibers (mostly in tunica media)
- Most are near the heart because they allow stretching to occur when the heart pumps blood to them (aorta, pulmonary and brachiocephalic arteries)
- These arteries branch into muscular arteries
What are muscular arteries?
- Medium-sized arteries
- Possess elastic fibers in 2 concentric rings: internal elastic lamina separates the tunica intima and media, whereas the external elastic lamina separates the tunica media and externa
- Have thicker tunica media with multiple layers of smooth muscle cells
- Most named arteries are muscular
- Muscular arteries branch into arterioles
What are arterioles?
- The smallest arteries
- Number of tunics and the thickness of walls vary between larger and smaller arterioles
- Generally all have 6 layers of smooth muscle cells in the tunica media
- Sympathetic innervation to muscle fibers of tunica media cause vasoconstriction which elevates blood pressure upstream
What are capillaries?
- The smallest blood vessels
- For most, their walls consist of tunica intima
- Allow for metabolic exchange between blood and tissues
What are capillary beds?
- A group of capillaries
- Each bed is fed by a metarteriole
- Several true capillaries branch from the metarteriole to form the bulk of the capillary bed
- The metarteriole continues distally to the thoroughfare channel which then connect to the postcapillary venule
1. Continuous: endothelial cells form a complete lining aided by tight junctions (most common in muscle and brain)
2. Fenestrated: endothelial cells contain pores that allow fluid exchange between blood and interstitial fluid (in small intestine and kidneys)
3. Sinusoids: have large gaps between endothelial cells and a discontinuous basement membrane which allows for the transport of large molecules and cells to and from blood (in bone marrow and liver)
What are veins?
- Drain capillaries and return blood to the heart
- Pressure is lower in veins than in arteries
- At rest, they hold about 60% of the body’s blood
- Function as blood reservoirs
- Venules are small veins
- Companion vessels with arterioles
- Smallest are the postcapillary venules
- Diapedesis (leukocytes migrating from bloodstream to interstitial fluid) occurs through walls of postcapillary venules
- Venules merge to form veins
- Smaller and medium sized veins travel with muscular arteries
- Large veins travel with elastic arteries
- Contain valves formed by tunica intima that prevent blood pooling in veins
- Muscles bulge as they contract and push on veins, helping to move blood towards the heart (skeletal muscle pump)
- Venous return is also assisted by the respiratory pump which changes intrathoracic and intra-abdominal pressure
What is blood pressure?
- The force per unit area that blood places on the inside of a blood vessel
- Measured by a sphygmomanometer
- Systolic BP: pressure during ventricular contraction
- Diastolic BP: pressure during ventricular relaxation
- Pressure is pulsatile until it reaches capillaries
- Pressure decreases from aorta to venae cavae
What is the arterial flow out of the heart?
- Oxygenated blood is pumped out of left ventricle into ascending aorta from which the left coronary artery and right coronary artery branch off of
- 3 arterial branches emerge from the aortic arch: brachiocephalic trunk, left common carotid artery, left subclavian artery
- Descending thoracic aorta follows aortic arch and several arteries emerge to thoracic wall
- Changes name to descending abdominal aorta after it passes through diaphragm
- At fourth lumbar vertebra, the aorta bifurcates into left and right common iliac arteries
- Common iliac arteries further divide into internal and
external iliac arteries
What is the venous return to the heart?
- Superior vena cava is formed from a fusion of the right and left brachiocephalic veins and drains into the right atrium
- Inferior vena cava returns blood to the right atrium from
lower limbs, pelvis and perineum, and abdominal structures
What is the blood flow through the head and neck?
- Left and right common carotid arteries supply most of the blood to the head and neck
- At the superior border of the thyroid cartilage, they divide into external and internal carotid arteries
- External carotid artery provides blood to several branches:
– Superior thyroid artery
– Ascending pharyngeal artery
– Lingual artery
– Facial artery
– Occipital artery
– Posterior auricular artery - External carotid artery then divides into maxillary artery and superficial temporal artery
- Venous blood return is through the internal jugular vein or the external jugular vein
- These two veins drain into the subclavian vein and then into the brachiocephalic vein
What is blood flow through the cranium?
- Internal carotid arteries enter cranium through carotid canal
- They divide into anterior and middle cerebral arteries, which supply brain, and ophthalmic arteries, which supply the eyes
- Vertebral arteries branch from subclavian arteries and enter cranium through the foramen magnum where they merge to form the basilar artery
- The basilar artery and internal carotid arteries provide blood to vessels that create an anastomosis called the cerebral arterial circle
- Vessels in the circle include: anterior cerebral arteries, anterior communicating artery, posterior cerebral arteries, posterior communicating artery
- Most cranial venous blood drains through dural venous sinuses
- These large veins are formed between the two layers of dura mater
- There are no valves in the dural venous sinus system so blood can flow in more than one direction
• The dural sinus system includes:
– Superior sagittal sinus
– Inferior sagittal sinus
– Straight sinus
– Left and right transverse sinuses
– Left and right sigmoid sinuses
What is blood flow through thoracic and abdominal walls?
• The internal thoracic artery arises from the subclavian artery
• It gives rise to upper anterior intercostal arteries (1–6) and then continues on to become the superior epigastric artery, which supplies blood to the superior abdominal wall
• The inferior epigastric artery is a branch of the external iliac artery and supplies blood to the inferior abdominal wall and forms an anastomosis with the superior epigastric artery
• Internal thoracic vein is formed by merger of intercostal,
superior epigastric and musculophrenic veins
• Inferior epigastric vein merges with external iliac vein
• Supreme intercostal vein that drains into brachiocephalic vein
• Lumbar and posterior intercostal veins enter azygous system
– Left side drains into the hemiazygos and accessory hemiazygos veins
– Right side veins and the hemiazygos vessels drain into the azygos vein
• Blood from the azygos vein drains into the superior vena cava just before it enters the right atrium
What is blood flow through thoracic organs?
• The lungs are supplied by several bronchial arteries that
branch from the descending thoracic aorta
• The esophagus is mostly supplied by esophageal arteries that branch from the descending aorta
• The diaphragm is supplied from three sources:
– Superior phrenic arteries
– Musculophrenic arteries
– Inferior phrenic arteries
What is blood flow through the gastrointestinal tract?
• Three unpaired arteries emerge from anterior wall of
descending abdominal aorta and supply blood to
gastrointestinal tract:
– Celiac trunk
– Superior mesenteric artery
– Inferior mesenteric artery
What is the arterial supply to the abdomen?
• The celiac trunk gives off three branches:
1. Left gastric artery: Supplies lesser curvature of stomach and lower esophagus
2. Splenic artery: Supplies the spleen and part of the stomach
3. Common hepatic artery: Supplies the liver, gallbladder, and a portion of the stomach
• The superior mesenteric artery provides blood to the
following branches:
1. Inferior pancreaticoduodenal arteries: Supplies portions of the pancreas and duodenum
2. Intestinal arteries: Supply the jejunum and ileum
3. Ileocolic artery: Supplies the ileum, cecum, and appendix
4. Right colic artery: Supplies the ascending colon
5. Middle colic artery: Supplies most of the transverse colon
• The inferior mesenteric artery provides blood to the following branches:
1. Left colic artery: Supplies distal part of transverse colon and proximal part of descending colon
2. Sigmoid arteries: Supplies distal descending colon and sigmoid colon
3. Superior rectal artery: Supplies the rectum and upper half of the anal canal
What is the hepatic portal system?
• The hepatic portal system is a network of veins that brings nutrient-rich blood from digestive organs to the liver
• The hepatic portal vein is formed by the fusion of three
abdominal veins
1. Inferior mesenteric vein: Drains the distal part of the colon
2. Splenic vein: Drains the spleen, pancreas, and stomach
3. Superior mesenteric vein: Drains blood from the small intestines, proximal part of colon, pancreas, and stomach
• Hepatic veins collect blood from liver and return it to the
inferior vena cava
What is blood flow through the posterior abdominal organs, pelvis and perineum?
• Three paired arteries issued from the descending abdominal aorta include:
1. Middle suprarenal arteries: Supply the adrenal gland
2. Renal arteries: Supply the kidneys
2. Gonadal arteries: Either the testicular or ovarian arteries supplying the gonads
• Branches of the internal iliac artery include:
1. Superior and inferior gluteal arteries: Supply the gluteal region
2. Obturator artery: Supplies the medial thigh
3. Internal pudendal artery: Supplies the anal canal and the perineum
4. Middle rectal artery: Supplies the rectum
5. Uterine and vaginal arteries: Supply the uterus and vagina
• Venous drainage provided by internal iliac vein
– It merges with common iliac vein which then drains to inferior vena cava
What is blood flow through the upper limb?
• Right and left subclavian arteries supply blood to upper limbs
• As the subclavian artery passes over lateral border of first rib, its name changes to the axillary artery
• The axillary artery supplies the shoulder and thoracic region
• As the axillary artery passes the inferior border of the teres major muscle, its name changes to the brachial artery
• In the cubital fossa, the brachial artery bifurcates into the ulnar and radial arteries
• These arteries of the forearm anastomosis and form the
superficial and deep palmar arches in the palm of the hand
• Digital arteries emerge from the arches to supply the fingers
What is superficial venous drainage of the upper limb?
- On the dorsum of the hand, a dorsal venous network drains into the basilic and cephalic veins
- In the cubital fossa, these two veins are connected by the median cubital vein - a common site for venipuncture
What is deep venous drainage of the upper limb?
- The digital veins and superficial and deep palmar venous arches drain into pairs of radial and ulnar veins in the forearm
- At the cubital fossa, the radial and ulnar veins merge to form a pair of brachial veins
- The brachial veins merge with the basilic vein to form the axillary vein
- The axillary vein changes its name to the subclavian vein as it crosses superior to the lateral border of the first rib
What is blood flow through the lower limb?
• The right and left external iliac arteries supply blood to the lower limb
• As external iliac passes inferior to inguinal ligament, its name changes to femoral artery, which provides a branch called the deep femoral artery
• The deep femoral artery supplies the hip joint via medial and lateral circumflex arteries
• The femoral artery enters the posterior popliteal fossa, where its name changes to the popliteal artery
– Popliteal artery supplies the knee joint and muscles in that region
• The popliteal artery divides into the anterior and posterior tibial arteries, which supply the anterior and posterior compartments of the leg, respectively
• The posterior tibial artery provides a branch called the fibular artery, which supplies the lateral compartment of the leg
• The posterior tibial artery divides into the medial and lateral plantar arteries in the foot
• The anterior tibial artery becomes the dorsalis pedis artery at the anterior surface of the ankle
– This artery and a branch of the lateral plantar artery unite to form the plantar arch
• Digital arteries extend from the arch to supply the toes
What is superficial venous drainage of the lower limb?
- On top of foot, a dorsal venous arch drains into the great saphenous vein medially and the small saphenous vein laterally
- The great saphenous vein drains into the femoral vein and the small saphenous vein drains into the popliteal vein
What is the deep venous drainage of the lower limb?
• Digital veins and deep veins of the foot drain into pairs of medial and lateral plantar veins
• These veins drain into a pair of posterior tibial veins
• On the dorsum of the foot and ankle, deep veins drain into a pair of anterior tibial veins
• The anterior and posterior tibial veins merge to form the
popliteal vein in the popliteal fossa
• The popliteal vein curves onto the anterior thigh
compartment and becomes the femoral vein
• Once the femoral vein passes superior to the inguinal
ligament, it becomes the external iliac vein
• When the external iliac vein fuses with the internal iliac vein, the new vein is called the common iliac vein
• The left and right common iliac veins merge to form the
inferior vena cava
What is pulmonary circulation?
• Pulmonary circulation carries deoxygenated blood from right side of heart to lungs and returns newly oxygenated blood to left side of heart
• In this circulation, arteries carry deoxygenated blood and veins carry oxygenated blood
– This is opposite the systemic circulation
• Deoxygenated blood exits the right ventricle into the
pulmonary trunk, which bifurcates into right and left
pulmonary arteries that go to the lungs
• These arteries branch into arterioles and then capillaries and finally return to the left atrium as pulmonary veins
What is the aging of vessels?
• Vessels lose resilience with age
– Blood pressure may increase
– Older individuals more susceptible to aneurysms (ballooning out of artery wall that can rupture)
– Atherosclerosis risk also increases with age
