Cardiovascular System Module 1 Topic 1.2a PDF

MODULE 1 Cardiovascular System Blood vessels Topic 1.2a: Functional anatomy of arteries 1  Learning Objectives ü identify the major arteries in the body ü describe the structure and function of all types of blood vessels in the CVS. ü describ...

MODULE 1 Cardiovascular System Blood vessels Topic 1.2a: Functional anatomy of arteries 1  Learning Objectives ü identify the major arteries in the body ü describe the structure and function of all types of blood vessels in the CVS. ü describe the microscopic structure of blood vessels. ü describe the mechanisms involved in the control of blood vessel diameter. ü describe the risk factors for coronary artery disease (CAD) and why they increase the risk of atherosclerosis. ü describe the basic steps involved in the progression of atherosclerosis. Low pressure High pressure Overview High pressure § Heart (left) i. Arteries § Large arteries § Small arteries § Arterioles ii. Capillaries (exchange) iii. Veins § Venules § Small veins § Large veins § Heart (right) Low pressure 2 Blood vessel structure 3 layers ‘tunics’ that surround a lumen intima (innermost); media (middle); arteries, veins, capillaries externa (outermost) Smooth muscle layer (tunica media) § Vasoconstriction - lumen reduces § Vasodilation - lumen increases lumen lu m en Arteries § Arteries = pressure reservoirs Can be divided into 3 groups i. Elastic § conducting, largest, thick walled, located near the heart, diameter (2.5cm-1 cm), most elastic (contain elastin - very distensible), expand and recoil as blood moves ii. Muscular § distributing, respond to extrinsic control mechanisms, affects blood pressure (vasoconstrict/vasodilate) and blood distribution, Less stretch iii. Arterioles § smallest arteries (diameter = 0.3 mm -10um), feed into capillary beds, finer adjustments to diameter (BF) due to hormonal, neural, local chemical influence. resistance vessels 3  (i) Elastic arteries § transport = high pressure blood (120 mmHg) § largest arteries (e.g. aorta or femoral artery) § conducting arteries § thick walled § distendable – lots of elastin § i.e. VERY stretchy § pressure reservoirs (ii) Muscular arteries § Distributing arteries (1 cm-0.3 mm diameter) § Respond to extrinsic control mechanisms (neural/hormonal). § Affects blood pressure and blood distribution § vasoconstrict; vasodilate; less stretch B = diameter changed in vessel B Vasoconstrict Blood Flow Blood Flow = constant = constant A = diameter equal in A, B, C, D 4 (iii) Arterioles Respond to § Neural § Hormonal § Local signals (intrinsic or autoregulation) § myogenic § metabolic § Vasodilation = ↑ blood flow § Vasoconstriction = ↓ blood flow § Example: exercising muscle (dilate arterioles) & kidney (constrict arterioles) VasoDILATIORS Extrinsic and Intrinsic controls of blood flow i. Intrinsic control (Autoregulation) § blood flow changes to tissues independent to nerves/hormones Intrinsic Extrinsic § Metabolic (chemical) VasoCONSTRICTORS § Myogenic (physical) ii. Extrinsic control (keeps us alive) § redirect blood flow to where its needed most § maintain blood pressure (BP) § Neural (SNS) § Hormonal 5  Intrinsic controls: Metabolic autoregulation Example: Active hyperaemia in skeletal muscle § increase blood flow (BF) into tissue after stimulus (exercise) § exercise ↓ O2 and ↑ metabolic waste in tissue § SNS = ↑ norepinephrine § vasoconstriction § divert blood from non-essential organs Major Arteries: Systemic Circulation Upper Limb § Axillary a 1. Ascending Aorta § Brachial a. § Radial a 2. Aortic arch § Ulnar a § Brachiocephalic trunk § Right common carotid a. § Right subclavian a. 3. Left common carotid a. 4. Left subclavian a. 5. Descending aorta (abdomen/LL) § Thoracic aorta § Abdominal aorta § Common iliac a. § Internal iliac a. § Femoral a. § Popliteal a. ( anterior an posterior tibial arteries) 6 Major Arteries schematic flowchart Arterial pulse sites § Know the sites and how to palpate them § Pulse sites § Pressure points Q. Which pulse point is important when measuring blood pressure? 7  Major Arteries Head and neck 1. Common carotid artery § External carotid artery (superficial) § supplies tissues of head except brain and orbit § Internal carotid artery (deep) § supplies orbits and more than 80% of cerebrum 2. Vertebral artery § arises from subclavian artery § ascends through transverse foramina in the cervical vertebrae to enter skull through foramen magnum. § supplies occipital lobes and inferior temporal lobes Activity: ‘Label & Learn’ Correctly match the major arteries: E § R. Subclavian a. D § Brachiocephalic trunk C § R. Common carotid a. A § R. External carotid a. § R. Internal carotid a. F § R. Vertebral a. B 8  Cardiovascular Disease Atherosclerosis 1. Arteriosclerosis (sclerosis = hardening) § Arterial walls become thicker and stiffer → hypertension 2. Atherosclerosis (arthero = glue) § most common form of arteriosclerosis § Atheroma's (raised lesion) form in tunica intima layer Arteriosclerosis § Contain macrophages, lipids, debris, fibrous connective tissue § Damage occurs to endothelium → inflammatory response § Lipids accumulate in tunica intima § Smooth muscle proliferates and fibrous tissue forms § Atherosclerotic plaque forms and enlarges → becomes unstable Atherosclerosis AFFECTED SITE COMPLICATION Atherosclerosis cerebral arteries stroke Risk factors carotid arteries stroke aorta aneurysm 1. hypertension (↑ BP) coronary arteries heart attack 2. dyslipidaemia (↑ cholesterol or fatty renal arteries hypertension acids) iliac arteries PVD 3. hyperglycaemia (↑ blood sugar/glucose 4. lack of exercise (sedentary activity) femoral arteries PVD 5. obesity tibial arteries 6. smoking (cigarettes) 7. chronic stress Turbulence, vessel damage & atherosclerosis 9 Coronary Artery Disease Treatment Coronary angioplasty: widening of a blocked or narrowed coronary arteries using a balloon Cardiovascular Disease Prevalence & Mortality A ↑ CVD prevalence in younger indigenous B § ↑ Mortality rates of CVD in indigenous males. § CVD Major cause of death [A] Prevalence (%) of CVD in indigenous vs. non indigenous (age); [B] Major causes of CVD deaths among indigenous people (sex) 10 Questions: Review and Learn 1. Where is most of the smooth muscle in arterial walls located? a. tunica intima b. tunica externa c. tunica media d. endothelium 2. Vasodilation of ________________________ is largely responsible for increasing blood pressure. a. conducting arteries b. pre-capillary sphincters c. large veins d. distributing arteries and arterioles e. the original question is incorrect, vasodilation will decrease blood pressure Summary of key concepts: Cardiovascular System Topic 1.2a § general structures blood vessels: tunica intima, tunica media and tunica externa § arteries: elastic, muscular and arterioles § elastic: transport, high pressure, pressure reservoirs § muscular: large SM layer (vasoconstrict/vasodilate), distributing, extrinsically regulated (neural hormonal) § arterioles: feed capillaries, respond top local signals (paracrine), myogenic, metabolic § blood flow regulation: extrinsic vs. intrinsic § Intrinsic (metabolic and myogenic), stretch, metabolites ( O2, CO2, H+, NO, lactate) § Extrinsic: Neural (SNS) or hormonal (NE, Angiotensin, ADH). § Redistribute blood flow to non essential organs (i.e. exercise) describe the risk factors for coronary artery disease (CAD) and why they increase the risk of atherosclerosis. § name of major arteries: head and neck, abdomen, upper limb and lower limb § arterial pulse points: name and location and clinical significance § cardiovascular disease: progression of atherosclerosis, risk factors, CAD (cause and treatment) 11