9.28.2023 - Circulatory System Student.pptx

Circulatory System ID 767 – FALL 2023 MICHAEL BROWN, PT, DPT, SCS OBJECTIVES 1. Identify the components of the circulatory system 2. Identify the histological features of the heart 3. Describe the histological structures of the blood vessels 4. Explain the correlation between the circulatory histo...

Circulatory System ID 767 – FALL 2023 MICHAEL BROWN, PT, DPT, SCS OBJECTIVES 1. Identify the components of the circulatory system 2. Identify the histological features of the heart 3. Describe the histological structures of the blood vessels 4. Explain the correlation between the circulatory histological components and their functions 5. Distinguish the differences between the various blood vessels Circulatory Components 1.Heart 2.Arteries 3.Veins 4.Capillaries 5.Lymphatics Heart 1. 4 chambers a) 2 Atria (right and left) b) 2 Ventricles (right and left) 2. Rhythmical contraction for pumping 3. 3 layers in the walls a) Endocardium – Endothelial lining and connective tissue b) Myocardium – Cardiac muscle a) Thickest layer c) Epicardium – simple squamous epithelium (Mesothelium) with a layer of loose connective tissue Epicardium Myocardium Endocardiu m En = Endothelium, SEn = Subendocardial layer, P = Purkinje fibers, M = Muscle fibers (Cardiac) Heart Endocardium 1. Innermost layer 2. Fibroelastic connective tissue with scattered smooth muscle 3. Deep layer of connective tissue continuous with tissue of the myocardium (subendocardial layer) a) Special modified cardiac muscle called Purkinje fibers (conduction) located here Endocardiu m Myocardiu m Subendocardiu m En = Endothelium, SEn = Subendocardial layer, P = Purkinje fibers, M = Muscle fibers (Cardiac) Heart Myocardium 1. Contractile cardiac muscle fibers arranged spirally around the heart chambers 2. Myocardium much thicker in the ventricles compared to atria a) Left 3 times thicker than right Endocardiu m Subendocardium Myocardium Heart Epicardium 1. Outermost layer (most superficial) = mesothelium a) Cells produce serous fluid that prevents friction as heart beats 2. Supported by loose CT, which contains blood vessels, autonomic nerves, adipose 3. Pericardium 1. 2. Parietal layer = outer layer, fibrous sac with serous lining Visceral layer = epicardium Ep = Epicardium, Mes = Mesothelium, CT = Connective tissue (loose), M = Myocardium, N = Nerves, F = Fat Cardiac Skeleton 1. Dense irregular connective tissue separating the musculature of atria from ventricles a) Extends into valves 2. Functions: a) Surround, support and anchor to valves b) Attachment site for cardiac muscle c) Electrical insulation Heart Valves 1. Dense connective tissue lined with endothelium 2. Prevent backflow of blood C = Connective tissue (dense), A = Atrium, V = Ventricle, CT = Chordae tendineae, M = Myocardium, En = Endocardium Heart Conducting System Sinoatrial Node Atrioventric ular Node AV Bundle (His) Purkinje fibers Blood Vessel Structure Tunica Intima Tunica Media Tunica Externa (Adventitia) Endothelium 1. Simple squamous epithelial tissue 2. Functions: a) Monitors molecule exchange – semi-permeable b) Secretes agents to prevent blood from clotting (nonthrombogenic) c) Regulates vascular tone and blood flow d) Stimulates smooth muscle contraction e) Inflammation Blood Vessel Layers 1. Tunica Intima (I) a) Endothelium b) Subendothelial layer = loose CT, sometimes smooth muscle c) Internal elastic lamina (in arteries) (IEL) 2. Tunica Media (M) a) Concentric layers of smooth muscle b) Variable amounts of elastic fibers, elastic lamellae, reticular fibers, proteoglycans c) External elastic lamina – sometimes in arteries 3. Tunica Externa (Adventitia) (A) a) Type I collagen + elastic fibers b) Bound to surrounding tissue V = Vaso Vasorum Vaso Vasorum 1. Blood supply to the vessels 2. Within the tunic externa (adventitia) of large vessels 3. Brings oxygen and nutrients to cells too far from the lumen A = Arterioles, V = Venules, N = Nerves, SM = Smooth Muscle, E = Elastic Lamellae Large / Elastic Artery 1. Aorta, pulmonary arteries 2. Tunica intima (I) also well-developed a) Smooth muscle in subendothelial CT b) Internal elastic lamina is well defined at border between tunica intima and media 3. Thick tunica media (M) containing elastic lamellae and smooth muscle 4. Tunica adventitia (A) – contains vasa vasorum, nerves, lymphatic capillaries 5. The elastic laminae are important for uniform blood flow. a) Ventricles contract = blood pushed into large arteries, walls stretch b) Ventricles relax = blood pressure drops, but the elastin rebounds and helps maintain arterial pressure E = Endothelial cells Medium / Muscular Artery 1. Tunica intima has thin subendothelial layer a) Prominent internal elastic lamina (IEL) 2. Tunica media may contain up to 40 layers of smooth muscle (SM) cells with interspersed elastic lamellae a) External elastic lamina ONLY in larger muscular arteries 3. Tunica adventitia – similar to large arteries – contains vasa vasorum (V), nerves, lymphatic capillaries 4. Distribute blood to organs 5. Help regulate blood pressure by contracting or relaxing smooth muscle in the media Small Arteries / Arterioles 1. Tunica intima (I) a) Endothelium (E) b) Subendothelial layer is very thin c) No elastic lamina 2. Tunica media (M) often only contains 3-4 layers of smooth muscle 3. Adventitia (Ad) may be hard to pinpoint 4. Leading up to microvasculature smallest arterioles (A), capillaries (C), venules (V) 5. This is where exchange between blood and interstitial fluid happens Capillaries 1. Location of exchange with blood and interstitial fluid 2. Enters oxygenated leaves poorly oxygenated 3. Pericytes (P) – dilate or constrict capillaries through extensions into endothelial cells a) Can differentiate into smooth muscle in new vessels 4. 3 types: a) Continuous – tight, well-developed occluding junctions. Most common b) Fenestrated – Sieve-like allowing more exchange c) Sinusoid – maximal exchange through large perforations Capillaries Venules (V) 1. Larger lumens than arterioles 2. Wall is very thin, mainly consisting of endothelium with some pericytes and a few smooth muscle cells 3. Larger venules will have upwards of 3 layers of smooth muscle and a more distinct adventitia 4. Leading away from microvasculature (smallest arterioles (A), capillaries (C), venules) Lymphatic vessels (L) Medium Veins (MV) 1. Typically adjacent to medium/muscular arteries 2. Tunica intima – thin 3. Tunica media - small bundles of smooth muscle mixed with reticular and elastic fibers 4. Tunica adventitia - welldeveloped with dense irregular connective tissue 5. Carrying blood back to the heart Large Veins 1. Typically adjacent to large/elastic arteries 2. Tunica intima (I) is well developed a) May see internal elastic lamina 3. Tunica media (M) has smooth muscle mixed CT 4. Collagen in the adventitia (A) tends to be well-developed (thicker than tunica media) 5. Valves (V) are present. 6. Carrying blood back to the heart 7. Valves help prevent backflow of blood in large veins Lymphatic Vessels 1. Thin-walled lymphatic capillaries a) Endothelial cells (E) 2. Lymph (L) fluid that is lightly staining but does not contain red blood cells 3. Collect interstitial fluid and return it to blood 4. Anchoring filaments prevent collapse 5. Along the path to larger lymph vessels (that empty into blood vessels), lymph is processed in lymph nodes Type of Artery Elastic arteries Intima Media Adventitia Endothelium; connective tissue with smooth muscle Many elastic lamellae alternating with smooth muscle Connective tissue, thinner than media, with vasa vasorum Endothelium; connective tissue with smooth muscle, internal elastic lamina prominent Endothelium; connective tissue less smooth muscle Many smooth muscle layers, with much less elastic material Roles in Circulatory System Venules Endothelium; no valves (postcapilla ry, collecting, and muscular) Small veins Endothelium; connective tissue with scattered smooth muscle fibers Medium Endothelium; connective veins tissue, with valves Pericytes and scattered smooth muscle cells Conduct blood from heart and with elastic recoil help move blood forward under steady pressure Connective tissue, thinner Distribute blood to all organs and than media; vasa vasorum maintain steady blood pressure maybe present and flow with vasodilation and constriction Connective tissue, thinner Distribute blood to arterioles, than media; no vasa vasorum adjusting flow with vasodilation and constriction Very thin connective tissue Resist and control blood flow to layer capillaries; major determinant of systemic blood pressure None Exchange metabolites by diffusion to and from cells None Drain capillary beds; site of leukocyte exit from vasculature Thin, 2-3 loose layers of smooth muscle cells Connective tissue, thicker than media Collect blood from venules 3-5 more distinct layers of smooth muscle Carry blood to larger veins, with no backflow Large veins Endothelium; connective > 5 layers of smooth Thicker than media; longitudinal smooth muscle may be present Thickest layer, with bundled Muscular arteries Small arteries 3-10 layers of smooth muscle Arterioles Endothelium; no connective 1-3 layers of smooth tissue or smooth muscle muscle Capillaries Endothelium only A few pericytes only Return blood to heart Questions? Tissue Examples References 2021 UMMC Fundamental Histology and Cell Biology Course Materials Drake RL, Vogl W, Mitchell AWM. Gray's Anatomy for Students. Fifth ed. Philadelphia, PA: Elsevier; 2024. https://www.clinicalkey.com/dura/browse/bookChapter/3-s2.0-C20210023117. Accessed September 22, 2023. Drake RL, Vogl W, Mitchell AWM. Gray's Atlas of Anatomy. Third ed. Philadelphia, PA: Elsevier; 2021. INSERT-MISSING-URL. Accessed September 22, 2023. https://histologyguide.org/index.html Nerve Tissue & the Nervous System. In: Mescher AL. eds. Junqueira's Basic Histology Text and Atlas, 16e. McGraw Hill; 2021. Accessed September 14, 2023. https://accessmedicine.mhmedical.com/content.aspx?bookid=3047&sectionid =255120935