Cardiorespiratory System- Blood Vessels Flashcards
1
Q
What is the anatomy of blood vessels?
A
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
2
Q
What are blood vessel tunics?
A
- 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
3
Q
What are arteries?
A
- Transport blood away from the heart
- 3 types: elastic, muscular and arterioles
4
Q
What are elastic arteries?
A
- 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
5
Q
What are muscular arteries?
A
- 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
6
Q
What are arterioles?
A
- 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
7
Q
What are capillaries?
A
- The smallest blood vessels
- For most, their walls consist of tunica intima
- Allow for metabolic exchange between blood and tissues
8
Q
What are capillary beds?
A
- 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)
9
Q
What are veins?
A
- 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
10
Q
What is blood pressure?
A
- 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
11
Q
What is the arterial flow out of the heart?
A
- 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
12
Q
What is the venous return to the heart?
A
- 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
13
Q
What is the blood flow through the head and neck?
A
- 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
14
Q
What is blood flow through the cranium?
A
- 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
15
Q
What is blood flow through thoracic and abdominal walls?
A
• 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
