General Histology Midterm Notes PDF

THE CIRCULATORY SYSTEM HEART  Muscle type: CARDIAC MUSCLE  4 chambers:...

THE CIRCULATORY SYSTEM HEART  Muscle type: CARDIAC MUSCLE  4 chambers: Ventricle- it propels blood Vasculature: blood vessels  Left ventricle - lower chamber Function: *Propels blood systemic circulation  Transport blood  Right ventricle -lower chamber  Transport oxygen (transported by red blood *Propels bood to pulmonary ciruclation (lungs) cells) and CO2, nutrient, metabolic waste Atrium- receives blood  Temperature regulation  Right atria- upper chamber  Hormone distribution *Receives blood from body  Immune function (by white blood vessels)  Left atria- upper chamber *Receives blood from pulmonary veins Two functional system Endocardium 1. Blood vascular system  transport nutrients, gases, hormones to the other parts of the body, and collect waste products during cellular metabolism  Blood vessels (arteries,veins, capillaries, venules and arterioles) and heart(muscular pump)  Blood- the fluid Components:  Heart - it propels the blood throughout the system  Arteries and arterioles- carries blood away  Epithelial tissue: Simple Squamous Epithelial from the heart to the different tissue  Connective tissue: Loose Connective Tissue  Capillaries- where oxygen and carbon dioxide,  Myoelastic layer: smooth muscle fiber and nutrients and easte products exchange connective tissue between blood vessels and tissues. Smallest *middle layer vessels  Subendocardial layer→modified cardiac  Venules and veins- carries blood back to the muscle fibers called purkinje fibers that heart contrbites to impulse contracting system of 2. Lymph vascular system heart  Collect tissue fluids and return to blood vascular * it emerges to myoelastic tissue system  Lymphatic capillaries; lymphatic vessels; and Myocardium lymphoid organs (lymph nodes, spleen, thymus)  Lymph- the fluid Components:  Lymphatics  Lymph nodes HEART AND BLOOD VESSELS  Thickest layer - due to strong force of blood pumping specifically in left ventricle  Cardiac muscle→arranged in a spiral pattern  Fibrous skeleton of collagen (insulators that carry electric signal and provides structural support) and elastic fibers (allows heart to return its shapes after it contracts)  Numerous blood vessels -there is twisting Pericardium  Characteristics: similar cellular structure to the SA Fluid filled and double wall node but slightly smaller AV Bundle (Bundle of His)  Pathway: extends from the AV node into the interventricular septum  Function: conducts electrical impulses from the AV node to the ventricles  Branches:  Right bundle branch: conducts impulses to the right ventricle  Pericardial sac (parietal pericardium)  Left buncle branch: conduct impulses to the  Tough outer fibrous layer left ventricle  Thin serous lining of epithelial tissue  It anchors heart to aorta and vena cava Subendocardial conducting network  Epicardium (visceral pericardium)  Composed of specialized fibers known as Purkinje  Epithelial tissue:Simple Squamous fibers Epithelial  Function: rapidly transmits electrical impulses  Connective tissue: Loose Connective throughout the ventricles, ensuring coordinated Tissue contracion for effective blood pumping  More delicate layer  Directly in contact to the surface of heart Summary: 2 layers are close together with a pericardial fluid in Electrical impulse=heart beat between called pericardial fluid Starts with the SA node that generates impulse, Pericardial fluid which will spread to the atrium, stimulating contraction. - reduces friction cause by pumping After, it will go into the AV node, and once it receives an * inflammation or disease in the heart will affect impulse, there are delays so that the atrium will contract pericardial fluid and it will increase and accumulates first. After the atrium contracts, it will now spread into a when increase and it compresses the heart that can lead bundle of His. Travel down into the bundle of his, which to heart failure. will bifurcate to the right ventricle and left ventricle, which will be stimulated by Purkinje, and after the ventricle will Heart wall: other structures contract.  Dense fibrous connective tissue (Cardiac skeleton)  Forms part of the interventricular and interarterial septa  Surrounds all valves of the heart  Function: Anchoring and support the heart valves Providing firm points of insertion for cardiac muscle Electrical insulation HEART WALL: OTHER STRUCTURES  Cardiac conduction system Purkinje fibers *Generate and propagate electrical impulse  Larger than cardiac fibers with more glycogen and  Key components include: lighter staining Sinoatrial (SA) node  Part of the conduction system of the heart Atrioventricular (AV) node  Located beneath the endocardium on either side of AV bundle (bundle of his) the interventricular septum Subendocardial conducting network  Branch throughout the myocardium and deliver stimuli via gap junctions to the rest of the heart Sinoatrial (SA) node  Location: right atrial wall near the superior vena cava  Size: approximately 6-7 mm3  Function: initiating electrical impulses that stimulate atrial contraction *natural pace maker  Characteristics: composed of modified cardiac muscle cells with fewer myofibrils and intercalated disks compared to adjacent muscle fibers Atrioventricular (AV) node Systemic Circuit :  Location: floor of the right atrium near the AV valve *blood vessels that distributes blood  Function: receives impulses from the SA node and  Components: delays them (~120ms) Arteries- transport blood away from the blood *Delays to ensure complete contraction in atrium before Capillaries- exhange happens ventricular contraction  Veins- carry blood back to the heart  More prevalent in the walls of veins than arteries why? because veins contains more cells than VESSEL TUNICS arteries. Since they contain more cells, they need Tunica Intima more nourishment.  Inner most layer  They appear flat Artery  Composition:  3 major types: Simple squamous epithelium (endothelium) → 1. Elastic arteries- largest artery, known as the lines the lumen vessels conducting artery Secretes: 2. Muscular arteries- known as distributing artery  Type II, IV, V collagen, Laminin, 3. Arterioles- smallest artery endothelin, Nitric oxide (a component of oxygen dependent phagocytosis) , vWF Elastic artery (von Willebrand factor- function of clot  Aorta, common carotid artery, subclavian artery, formation or coagulation) , Tissue factor common iliac artery, and pulmonary trunk (clot formation or cuagulation), P- selectin  Yellow in fresh state (presence of elastin)  Posses: ACE, bradykinin, serotonin,  Tunica intima prostaglands, thrombin(function in clot  Endothelium supported by connective tissue formation or coagulation), norepinephrine with few fibroblast Subendothelial layer  Smooth muscle They line after endothelial cell  Collagen  Composition: loose connective tissue  Internal elastic laminae Internal elastic lamina  Weibel-palade bodies-secretes von willebrand Well developed in muscular artery factor that contribute in clot formation  Composition: elastin * internal elastic laminae are incomplete and appear  Separates tunica intima and tunica media thin  Fenestrated- presence of pores that  Tunica media allows or permit diffusion in to deeper  40 (a child) -70 (adult) fenestrated membranes layers (increase with age- arteries grow in thickness, due to continuous deposition of elastin) Tunica media  Smooth muscle cells (less abundant)  Thickest layer interspread between elastic membranes  Concentric cell layer →helically arranged smooth  ECM: chondroitin, sulfate, collagen, reticular muscle and elastin fiber  Fibrous element: elastic fibers, type III collagen,  External elastic lamina proteogylcans (they are interspread within smooth  Abundant is fenestrated membranes muscle)  Tunica adventitia  External elastic lamina  Thin layer of fibroelastic connective tissue More delicate than internal elastic lamina (loose and presence of fibroblast) They are only seen in larger muscular arteries  Vasa vasorum only  Lymphatic vessels Separates tunica media and tunica adventitia  Nerve fibers  Pericytes → replace the tunica media  Seen in capillaries and post-capillary vessel because they don’t have tunica media Tunica adventitita  Outer most layer which blends with the connective tissue  Composition: dense irregular, collagenous connective tissue  Fibroblast, type I and III collagen fibers, elastic fibers *tunica media and tunica adventitia are thick and they are muscular specifically in larger vessesl. Diffusion is not possible, here come vasa vasorum that are small Muscular artery vessels that can enter vessels walls that provides  Most vessels arising from aorta, brachial artery, nourishment. ulanr artery, femoral artery, renal artery  Identifying characteristics: thick tunica media Vasa vasorum composed mostly of smooth muscle cells  “vessels of the vessels”  Tunica intima  Furnish the muscular walls of the blood vessels with  Thinner than elastic artery a blood supply  Subendothelial layer: few smooth muscle cells  Prominent internal elastic lamina   Bifid (duplicated) internal elastic lamina Capillaries  Tunica media  Smallest blood vessels  Predominant smooth muscle cells:  50 um in length Small muscular arteries: 3-4 layers  8-10 um in width Large muscular arteries: 40 layers  Structure: single layer of squamous endothelial cell The number of smooth muscle cell layers and flatten however nucleus are bulgy and decrease as the diameter of artery decreases. tappering If you have larger muscular, you have more  3 types: smooth muscle layers. 1. Continuous  External lamina envelopes each smooth muscle cells  Exetrnal elastic lamina appear as several layers of thin elastic sheets  Elastic fibers, Type III collagen fibers, chondroitin sulfate  Tunica adventitia  ECM (they are produced by fibroblast): Elastic fibers, collagen fibers, and ground substance A tight gap junction, wherein they slightly overlap. (dermatan sulfate and heparan sulfate) Present in muscle, nervous and connective tissue. *Elastic fiber and collagen are arranged 2. Fenestrated longitudinally  Outer regions: vasa vasorum and unmyelinated nerve endings Presence of pores. It has sive structures. Some fenestration can be covered by a thin diaphragm and basement membrane covers fenestration. Present in pancreas, intestines, endocrine glands Arterioles and kidney. These organs have rapid exhange of  Arteries with a diameter of