Human Histology - Circulatory System PDF

HUMAN HISTOLOGY CHAPTER VIII: CIRCULATORY SYSTEM 1st Semester | S.Y. 2023-2024 FUNCTIONS OF THE CIRCULATORY SYSTEM 4. Aortic valve Delivers nutrients, oxygen, hormones, and Superior & inferior vena cava other rela...

HUMAN HISTOLOGY CHAPTER VIII: CIRCULATORY SYSTEM 1st Semester | S.Y. 2023-2024 FUNCTIONS OF THE CIRCULATORY SYSTEM 4. Aortic valve Delivers nutrients, oxygen, hormones, and Superior & inferior vena cava other related substances -> Organs & tissues → Drains deoxygenated blood to the right Removes metabolic end products for disposal atrium → Transported into the connective tissue or → Inferior vena cava = Largest vein lymphatic system Right atrium & right ventricle = Deoxygenated Participates in the immune system blood → Complement system Pulmonary artery = Pumps deoxygenated blood → Provides proteins and vitamins for repair of to the lungs tissue Pulmonary vein = Receives oxygenated blood from the lungs 2 SYSTEMS: Left atrium & left ventricle = Oxygenated blood 1. Blood Vascular System/Cardiovascular System Aorta = Pumps oxygenated blood towards the body 2. Lymph Vascular System → “Sewage system” CARDIOVASCULAR SYSTEM COMPONENTS OF CARDIOVASCULAR SYSTEM 1. Heart → Pump blood 2. Blood vessels Artery → Carry blood away from the heart → Carry oxygenated blood, except pulmonary artery Vein → Carry blood towards the heart → Carry deoxygenated blood, except pulmonary vein → Deoxygenated: Oxygen is already utilized PERICARDIUM by the tissues and is converted to CO2 Capillaries → Found between arteries and Outermost connective tissue surrounding the veins & distribute blood to tissue heart Envelops the heart 2 SACS/POUCHES OF PERICARDIUM: THE HEART Chambers of the Heart 1. Fibrous Pericardium 1. Atria (Right and left) = Receive blood from Dense irreg. CT vein 2. Ventricles (Right and left) = Eject blood to the 2. Serous Pericardium arteries Loose CT Valves of the Heart Serous membrane → Stop backflow of blood → Produce serous fluid = Protect heart 1. Tricuspid valve from physical injury 2. Pulmonary valve → Lined by simple squamous epithelium 3. Mitral valve (mesothelium)  → Pericardial fluid = 15-50 mL in adults; Reduces friction within the pericardium by lubricating the luminal surfaces of the visceral and parietal pericardia, thus allowing the membranes to easily glide over each other when the heart contracts; Produced by the mesothelial cells a. Parietal pericardium → Far from the heart b. Visceral pericardium/Epicardium → Attached to the wall of the heart ENDOCARDIUM → Outermost layer of the wall of the heart Thinnest layer Lines the internal surface Continuous with the inner layer of the great blood vessels Lined with endothelium Contain blood vessels, nerves, smooth muscles, and Purkinje fibers Composed of layers of epithelium and connective tissue 4 Layers of Endocardium: 1. Endothelium → SSE 2. Subendothelium → Loose CT 3. Dense CT layer → With collagen fibers, elastic elements, and smooth muscles 4. Subendocardium → Loose CT; contains many blood vessels, nerves, and Purkinje fibers HISTOLOGIC LAYERS OF THE HEART 1. Endocardium MYOCARDIUM 2. Mesocardium Cardiac muscle tissue 3. Epicardium Thickest layer Thickest: Left ventricle Thinnest: Atria  Arrangement: Spiraling course around the CARDIAC SKELETON cardiac skeleton Dense irreg. CT Originate and insert in the cardiac skeleton Forms stroma of the heart Cardiac muscles in atria and interventricular septum 3 COMPONENTS OF THE CARDIAC SKELETON: → Secrete atrial natriuretic peptide and brain natriuretic peptide 1. Septum membranaceum = Interventricular → Natriuretic peptide: septum Regulate blood pressure and 2. Annuli fibrosis = Surrounds the AV and electrolytes semilunar orifices Participate in cardio-renal homeostasis Target organs: Kidneys, adrenals, 3. Trigona fibrosa = Between the semilunar and AV pituitary gland, and brain orifices CARDIAC VALVE Dense CT Consist of reduplicated endocardia Continuous with the cardiac skeleton (Annuli EPICARDIUM fibrosis) Visceral pericardium Prevent backflow of blood Loose connective tissue 2 CLASSES OF VALVE: Lined with mesothelium Bigger branches of the coronary arteries are 1. Atrioventricular valve lodged = Epicardium contains a lot of Tricuspid valve → Right atrium + Right adipocytes ventricle Bicuspid (mitral) valve → Left atrium + Left ventricle 2. Semilunar valve Pulmonic valve → Right ventricle + Pulmonary artery Aortic valve → Left ventricle + Aorta  IMPULSE-CONDUCTING SYSTEM BLOOD, LYMPHATIC VESSLES, & NERVES Contraction = Triggered by electrical impulse Coronary arteries generated and propagated by Purkinje fibers → End arteries (specialized noncontractile cardiac muscle → Supplies the heart fibers) → Arise from the ascending aorta → Do not bifurcate 1. SA Node → Branches: What connects other arteries Consists of Purkinje fibers → In case of obstruction, providing new Boundary of the right atrium and the superior alternate routes is almost, if not at all, vena cava impossible Cardiac pacemaker → Other coronary arteries would not be able to compensate a blocked artery (Myocardial 2. Internodal Tracts (3) infarction) Small bundles of Purkinje fibers Cardiac vein Propagates the signal generated by SA node → Waste materials are drained → Empty either into the coronary sinus or 3. AV Node directly into the right atrium Located in the myocardium of the posterior → Collected by lymphatic tissue if emptied into lower part of the interatrial septum the coronary sinus Lymph channels 4. AV Bundle of His → Abundant in myocardium, subendocardium, and subepicardium Located in the dense connective tissue of the Heart receives efferent nerve from vagus trigonum fibrosum nerve (parasympathetic) and sympathetic 5. Bundle Branches (2) division of ANS Vagus nerve Right branch: Subendocardium of the right → Inhibit heart action ventricle Sympathetic fibers Left branch: Subendocardium of the left → Stimulate heart action ventricle SA Node 6. Purkinje Fibers → Function autonomously → Not innervated by the CNS & PNS Larger, paler, and has more glycogen than the → Determine rhythm of the heart typical cardiac muscle fibers → Frequency of signal = Influenced by the parasympathetic and sympathetic division THE BLOOD VESSELS 1. Arteries 2. Veins 3. Capillaries ENDOTHELIUM Simple squamous inner lining of all blood vessels  Facilitate the flow of blood 3. Sinusoidal Capillaries Regulates the diffusion of substances and cells Found in liver, spleen, bone marrow, and to and from blood some endocrine glands Regulatory functions = Secretion of substances Have discontinuities in their endothelium that participate in blood clotting (von that allow free passage of blood Willebrand factor, prostacyclins, and nitric Endothelium of sinusoids oxide) + inflammatory response → Formed by a mixture of phagocytic and non-phagocytic cells that rest on a discontinuous basal lamina CAPILLARIES → Basal lamina = Separated from the Smallest (7-9um) parenchyma of the organ by a very fine Simplest (endothelium only) network of reticular fibers Pericyte → Envelop the wall → Influence the size of capillaries → Blood flow Only one RBC can pass through small capillaries at a time = Necessary for gas and molecule exchange Not all capillaries in any given organ or tissue are used simultaneously ❖ Continuous & fenestrated capillaries = Not Many are closed and do not contain blood & seen in H&E staining open only when the need arises HISTOLOGIC LAYER OF VEIN AND ARTERY 1. Tunica Intima Endothelium + loose connective tissue (Subendothelium) Internal elastic lamina (Arteries only) Endothelium = Weibel-Palade bodies (storage site of von Willebrand factor which is synthesized by the endothelial cells of blood vessels) 3 Types of Capillaries: 2. Tunica Media 1. Continuous Capillaries Smooth muscle fibers External elastic lamina (Arteries only) Found in muscles, lungs, CNS, and skin Cells = Interdigitating 3. Tunica Adventitia Continuous endothelium Loose connective tissue = Arranged 2. Fenestrated Capillaries longitudinally Found in GI tract, endocrine glands, pancreas, and renal glomerulus Has pores in the cytoplasm that are bridged by diaphragms (except in glomerulus) of fibrils Pores = Molecules pass through  Tunica intima → Endothelium, subendothelium (Loose CT: elastic and collagen), and internal elastic membrane Tunica media → Well developed → ~40 layers of smooth muscle fibers → Most abundant: Smooth muscle Tunica adventitia ELASTIC ARTERY E.g. Pulmonary artery & aorta Tunica intima → Endothelium, subendothelium (loose CT with smooth muscle fibers), and elastic membrane that is continuous with elastic lamella of tunica media Tunica media → Has elastic lamella with smooth muscle and connective tissue in between the layers → External elastic membrane is continuous with elastic lamella → Most abundant: Elastic lamella Pump of the cardiovascular system during ARTERIES diastole (heart is resting after a contraction) During systole (contraction of the heart), the Deliver blood away from the heart elastic arteries store part of the mechanical Vasa vasorum → Small blood vessels within energy generated by the contraction of the the wall of large blood vessels and that supply heart by stretching their wall the blood vessel wall with nutrients 3 Types of Arteries: ❖ Systole = Pumping of left ventricle ❖ Diastole 1. Arterioles (Small) → Contraction of elastic artery 2. Muscular Arteries (Medium) → Able to revert back to its original size → Resting stage (in between heartbeat) 3. Elastic Arteries (Large) ARTERIOLES Heartbeat = Until arterioles only Tunica intima → Endothelium and internal elastic membrane (larger vessels) → No subendothelium Tunica media → 1-5 layers of smooth muscle → No elastic membrane Tunica adventitia MUSCULAR ARTERY Most of the named arteries in the body  SENSORY ORGANS ASSOCIATED WITH ARTERIES 1. Carotid & Aortic Bodies Sensitive to changes in the O2 and CO2 Hyperventilate = Release CO2 Embedded in the tunica adventitia Carotid body = Carotid artery Aortic body = Subclavian artery 2. Carotid Sinuses Sensitive to changes in arterial blood VENULES pressure ≤1mm in diameter Functionally: Like capillaries Morphologically: Have more CT in their wall VEINS Smooth muscle cells are scattered Deliver blood from tissues towards the heart Capillaries: Endothelial cells only Bigger calibers, more irregular lumens, and Venules: Endothelial cells + CT thinner and less elastic walls. Tunica intima Arteries = More muscular and elastic elements Tunica media Veins = More connective tissue elements → Only larger venules Tunica adventitia of large veins has 3 layers: → Muscle fibers are separated by CT 1. Internal zone (dense fibroelastic CT) Tunica adventitia 2. Middle zone (smooth muscle) → Thick 3. Outer zone (loose CT, collagen and elastic fibers) 3 Types of Veins: 1. Venules 2. Medium Veins 3. Large Veins  MEDIUM VEINS Almost all named veins and their principal tributaries Diameter: 1-9mm Tunica intima → Endothelium → Thin subendothelial layer (connective tissue) Tunica media → Circularly-arranged smooth muscle cells that is thinner than that of arteries → Smooth muscle fiber = Separated by CT; not as thick as the smooth muscle in medium artery VENOUS VALVES Tunica adventitia One-way valves that ensure unidirectional flow → Connective tissue of blood to the heart → Thickest layer Inward projections of tunica intima → May have vaso vasorum Blood flow in the vein → Facilitated by smooth muscle in tunica media → Contraction is not strong enough to push blood back to the heart Valves prevent backflow (e.g. medium veins like leg veins) Varicose Vein = Blood flow is not healthy LARGE VEINS Vena cava, pulmonary veins, and portal veins Tunica intima → Thicker but identical to that found in medium veins Tunica media → Poorly developed MODIFICATION IN THE ORGANIZATION OF BLOOD → Very few smooth muscle fibers are present VESSELS → Some vasa vasorum exist. Tunica adventitia Most common → Very thick organization of → Well-supplied with vasa vasorum blood vessels: → Has three zones: Capillary in a. Internal zone = Fibroelastic connective tissue between vein b. Middle zone = Smooth muscle fibers and artery (longitudinally arranged) c. Outer zone = Loose CT, Collagen and elastic fibers  Blood vessels: Hard to reconnect LYMPH VASCULAR SYSTEM 1. Arteriovenous anastomoses FUNCTIONS Found in skin of the palm, sole, lip, ear, nose, Collects the substances that leaked from the and mucous membrane of the nose and the capillaries and return them to the venous side digestive tract, erectile tissue, and tongue of the circulation No capillary in between Collect fluid produced by tissue Artery—Vein Contains lymph Lymph → Milky substance that is consist of 2. Portal systems water, proteins, lymphocytes, and fat droplets; Portal vein/artery: In between 2 sets of no RBC capillaries Cell in the lymphatic system: Lymphocyte Portal veins: Found in the digestive system and pituitary gland LYMPHATIC CAPILLARIES Start blindly → One end = Connected to a lymphatic vessel → Other end = Open (Collect fluid) Consist of endothelium only No pericyte LYMPHATIC VESSELS Composed of endothelium and underlying thin layer of connective tissue (collagen and elastic ❖ Capillary—Portal vein—Capillaries leading fibers) to the liver Large lymphatic vessels = Three layers (tunica Portal arteries: Found in kidneys intima, tunica media, and tunica adventitia) are found LYMPHATIC DUCTS 1. Right lymphatic duct Collects all lymph form structures on the right side of the body above the diaphragm Drains its lymph into the right brachiocephalic vein at the junction of the internal jugular and subclavian veins 2. Thoracic duct ❖ Afferent arterioles—Glomerulus (set of capillaries)—Efferent arteriole—Peritubular Collects lymph from the rest of the body capillaries (Tubules of kidney) Drains its lymph into the venous system at the junction of the left jugular and subclavian veins