CVS 1 Structure And Function Of CVS Flashcards
Where does the lymphatic system drain between?
Capillaries draining into large veins by heart
How much blood will a large man contain?
6l
Where does blood flow fastest? (In relation to cross sectional area)
Where cross sectional area is least
Which elastic arteries branch from the aortic arch?
Brachiocephalic, left common carotid, left subclavian
What are the major elastic arteries of the body?
R and L pulmonary arteries, aorta, braciocephalic, left common carotid, subclavian, L and R common iliac arteries
What happens in elastic arteries in systole and diastole?
Systole- LV contraction causes BP in aorta to rise to about 120mmHg and walls of elastic aorta and other elastic arteries stretch Diastole- aortic semilunar valve closes, aorta walls recoil maintaining pressure on blood and moving it towards the smaller vessels, aortic pressure drops to 70-80mmHg
What are the three major types of artery?
Elastic conducting- widest Muscular distributing- intermediate diameter, most of named arteries Arterioles-narrowest
What are the three layers of arteries and veins?
Tunica intima Tunica media Tunica adventitia
What is diffusion affected by?
Area available for exchange- capillary density Diffusion resistance- nature of barrier, nature of molecules diffusing, PATH length Conc grad- most importantly affected by flow of blood rather than conc of substances in blood
Outline amount of blood flow needed to body and brain. Which other organs must blood be delivered to at all times?
Body- 5 to 25L/min Brain- 0.75L/min Heart muscle and kidneys Note: date of blood flow=perfusion rate
Describe the major functional components of the circulation
Pump-heart Distribution vessels- arteries Flow control- arterioles and precapillary sphincters are the resistance vessels ensuring appropriate distribution do cardiac output Capacitance-ability to cope with changes in CO-store of blood in veins to cope with imbalances in blood returning and blood needing to be pumped out
Where is the majority of blood stored?
Veins
What do muscular arteries branch into?
Arterioles
What do arterioles regulate?
Amount of blood reaching an organ or tissue and blood pressure
What controls diameter of arteries and arterioles?
Autonomic nervous system
What do arterioles branch into?
Metarterioles
How many cells thick are capillary walls?
1
What is an end artery?
A terminal artery supplying all or most of blood to a body part without significant collateral circulation
Give three examples of end arteries
Renal, splenic, coronary
Where are the precapillary sphincters?
Between metarterioles and capillaries
Where do lymphatic capillaries return extra cellular fluid?
Junctions of internal jugular and subclavian veins
What are the typical diameters of capillaries?
7-10um
What are continuous capillaries?
Most common type with cells joined by tight or occluding junctions. Located in nervous, muscle and connective tissues, exocrine glands and lungs. Endothelial layer is continuous
What are fenestrated capillaries?
Capillaries where there are little interruptions across thin parts of endothelium bridged by a thin diaphragm(except in renal glomerulus). Found in parts of gut, endocrine glands and renal glomerulus
What are sinusoidal/discontinuous capillaries?
Larger capillaries (30-40um) with slower blood flow with gaps in walls allowing whole cells to move between blood and tissue. Found in liver, spleen and bone marrow
What are pericytes?
Cells that from a branching network on outer surface of endothelium of capillaries. These are capable of dividing into muscle cells, or fibroblasts during angiogenesis, tumour growth and wound healing
What type of valves do veins contain?
Paired semilunar. These ensure blood flows one way
Which veins don’t have valves?
Those narrower than 1mm and those in thoracic and abdominal cavities
How do muscles contribute to blood flow in veins
Muscle pump action in leg helps pump blood upwards against gravity
Describe elastic artery structure
Endothelium Thick tunica media with 40-70 fenestrated elastic membranes with smooth muscle and collagen between lamellar.thin external elastic lamina may be present. Tunica adventitia- layer of fibroelastic connective tissue containing vasa vasorum lymph vessels and nerve fibres
Describe the structure of muscular arteries
Tunica intima- endothelium Tunica media 40 layers of smooth muscle cells connected by gap junctions for coordinated contraction, prominent external elastic lamina Tunica adventitia- thin fibroelastic connective tissue layer containing vasa vasorum lymph vessels and nerve fibres
What nerve fibres act on muscular arteries?
Sympathetic nerve fibres stimulate vasoconstriction. Release noradrenaline which diffuses through fenestration in external elastic lamina to tunica media to depolarise superficial smooth muscle cells
Describe arteriole structure
Arteries with 1-3 layers of smooth muscle in tunica media. Thin elastic lamina only present in large arterioles External elastic lamina absent Scant tunica adventitia
In which blood vessels is velocity at its lowest
Capillaries
What are venae comitantes?
Deep paired veins that accompany some small arteries on either side, the three vessels being wrapped in one sheath. The pulsing of the artery promoted venous return in the veins. Examples are brachial, ulnar and tibial venae comitantes
What are vasa vasorum?
Small blood vessels that supply or drain the walls of larger arteries and veins. Embedded in tunica adventitia
What is the outermost layer of the pericardium? What is it attached to?
Fibrous pericardium. Bound to central tendon of diaphragm where extrapericardial fat can often be seen radiographically. Also attached to sternum by sternopericardial ligaments. Also stuck to mediastinal pleura except where the two separated by phrenic nerves
What makes up the inner pericardium
Serous pericardium- parietal layer lining the fibrous pericardium, visceral layer lining heart. Thin fluid layer between known as pericardial cavity.
What is the transverse sinus?
Passage posterior to aorta and pulmonary trunk and anterior to left atrium and superior vena cava that you can pass a finger through upon opening pericardial sac anteriorly
What is the oblique sinus?
The reflection of the pericardium at the venous end giving an inverted u along pulmonary veins and inferior vena cava
Describe the orientation of the heart
Lies obliquely (diagonally) between 3rd and 5th ribs, mainly on left side of midline of thorax but with roughly a third of it slightly to the right. Base: posterior surface-left atrium Apex: most inferior and lateral part of left ventricle lying beneath 5th intercostal space at midclavicular line.
Describe borders of heart
Right: right atrium between superior and inferior venae cava Left:left auricle and left ventricle Inferior:mainly right ventricle with a little left ventricle Superior: right and left atria and their auricles
