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A&P-chapter 21 notes-circulation.docx

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University of Toronto Mississauga
Robert Reisz

Chapter 21—Circulation  The Tunica Media (middle layer)  Blood vessels o Contains concentric sheets of smooth o Are classified by size and histological muscle in loose connective tissue organization o Binds to inner and outer layers o Are instrumental in overall o External elastic membrane of the tunica cardiovascular regulation media  Arteries—carry blood away from the heart Separates tunica media from tunica  Arterioles—are the smallest branches of externa arteries  The tunica external (outer layer)  Capillaries—are the smallest blood vessels; o Anchors vessel to adjacent tissues in location of exchange between blood and arteries interstitial fluid  Contains collagen fibers  Venules—collect blood from capillaries  Elastic fibers  Veins—return blood to the heart o In veins  The largest blood vessels  Contains elastic fibers o Attach to heart  Smooth muscle cells o Pulmonary trunk—carries blood from o Vasa vasorum (“vessels of vessels”) right ventricle  Small arteries and veins o To pulmonary circulation  In walls of larger arteries and  Aorta veins  Supply cells of tunica media and o Carries blood from left ventricle o To systemic circulation tunica externa  The Smallest Blood vessels  Differences between arteries and veins o Arteries and veins run side by side o Capillaries—have small diameter and thin walls o Arteries have thicker walls and higher  Chemicals and gases diffuse blood pressure across walls o Collapsed artery has small, round o The structure of vessel walls lumen (inner space)  Walls have three layers o Vein has a large, flat lumen  Tunica intima o Vein lining contracts, artery lining does  Tunica media not o Artery lining folds  Tunica externa o The tunica intima (inner layer) o Arteries more elastic  Includes o Veins have valves  Arteries  The endothelial lining  Connective tissue layer o Elasticity allows arteries to absorb pressure waves that come with each  Internal elastic layer—in heartbeat arteries, is a layer of elastic fibers in outer o Contractility  Arteries change diameter margin of tunica intima  Controlled by sympathetic division of ANS  Vasoconstriction—the o Are the smallest vessels with thin walls contraction of arterial smooth o Microscopic capillary networks muscle by the ANS permeate all active tissues  Vasodilation—the relaxation of o Capillary function arterial smooth muscle  Location of all exchange  Enlarging the lumen functions or cardiovascular  Vasoconstriction and vasodilation system o Affect:  Materials diffuse between blood  Afterload on heart and interstitial fluid  Peripheral blood pressure  Capillary structure  Capillary blood flow o Endothelial tube, inside thin basement  Arteries membrane o From heart to capillaries, arteries change o No tunica media  From elastic arteriesmuscular o No tunica externa arteries arterioles o Diameter is similar to red blood cell  Elastic arteries  Continuous capillaries o Also called conducting arteries o Have complete endothelial lining o Large vessels (ie. Pulmonary trunck o Are found in all tissues except epithelia and aorta) and cartilage o Tunica media has many elastic fibers o Functions of continuous capillaries and few muscle cells  Permit diffusion of water, small o Elasticity evens out pulse force solutes, and lipid-soluble  Muscular arteries materials  Block blood cells and plasma o Also called distribution arteries o Are medium sized (most arteries) proteins o Tunica media has many muscle cells  Specialized continuous capillaries  Arterioles o Are in CNS and thymus o Are small o Have very restricted permeability o Have little or no tunica externa o For example, the blood-brain barrier o Have thin or incomplete tunica media  Fenestrated capillaries  Artery diameter o Have pores in endothelial lining o Small muscular arteries and arterioles o Permit rapid exchange of water and  Change with sympathetic or larger solutes between plasma and endocrine stimulation interstitial fluid  Constricted arteries oppose o Are found in: blood flow  Choroid plexus  Resistance (R)  Endocrine organs  Kidneys  Resistance vessels- arterioles  Intestinal tract  Aneurysm o A bulge in an arterial wall o Is caused by weak spot in elastic fibers  Sinusoids (sinusoidal capillaries) o Pressure may rupture vessel o Have gaps between adjacent  Capillaries endothelial cells  Liver response to a chronically  Spleen constricted or occluded vessel  Bone marrow  Vasomotion  Endocrine organs o Contraction and relaxation cycle of o Permit free exchange capillary sphincters  Of water and large plasma o Causes blood flow in capillary beds to proteins constantly change routes  Between blood and interstitial  Veins fluid o Collect blood from capillaries in tissues o Phagocytic cells monitor blood at and organs sinusoidals o Return blood to heart  Capillary beds (capillary plexus) o Are larger in diameter than arteries o Connect one arteriole and one venule o Have thinner walls than arteries o Precapillary spincter o Have lower blood pressure  Guards entrance to each  Venules capillary o Very small veins  Opens and closes, causing o Collect blood from capillaries capillary blood to flow in pulses  Medium-sized veins  Thoroughfare channels o Thin tunica media and few smooth o Direct capillary connections between muscle cells arterioles and venules o Tunica externa with longitudinal o Controlled by smooth muscle segments bundles of elastic fibers (metarterioles)  Large veins  Collaterals o Have all three tunica layers o Multiple arteries to one capillary bed o Thick tunica externa o Allow circulation if one artery is o Thin tunica media blocked  Venous valves o Arterial anastomosis o Folds of tunica intima  Fusion of two collateral arteries o Prevent blood from flowing backward o Arteriovenous anastomoses o Compression pushes blood toward  Direct connections between heart arterioles and venules  The distribution of blood  Bypass the capillary bed o Heart, arteries and capillaries  Angiogenesis  30-35% of blood volume o Formation of new blood vessels o Venous system o Vascular endothelial growth factor  60-65%--1/3 of venous blood is (VEGF) in the large venous networks of o Occurs in the embryo as tissues and the liver, bone marrow, and skin organs develop  Capacitance of a blood vessel o Occurs in response to factors released o The ability to stretch by cells that are hypoxic, or oxygen- o Relationship between blood volume staved o Veins (capacitance vessels) stretch  Most important in cardiac more than arteries muscle, where it takes place in  Venous response to blood loss o Vasomotor centers stimulate o Depends on vessel length and vessel sympathetic nerves diameter o 1) Systemic veins constrict o Adult vessel length is constant (venoconstriction) o Vessel diameter varies by vasodilation o 2) Veins in liver, skin and lungs and vasoconstriction redistribute venous reserve o R increases exponentially as vessel  Total capillary blood flow diameter decreases o Equals cardiac output  Viscosity—R caused by molecules and o Is determined by pressure and suspended materials in a liquid resistance in the cardiovascular system o Whole blood viscosity is about four  Pressure times that of water o The heart generates P to overcome  Turbulence resistance o Swirling action that disturbs smooth o Absolute pressure is less important flow of liquid than pressure gradient o Occurs in heart chambers and great  The pressure gradient vessels o Circulatory pressure o Atherosclerotic plaques cause o The difference between abnormal turbulence  Pressure at the heart  An overview of cardiovascular pressures  And pressure at peripheral o Vessel diameters capillary beds o Total cross-sectional areas  Flow—is proportional to the pressure o Pressures difference; divided by R o Velocity of blood flow  Measuring pressure  Arterial blood pressure o Blood pressure o Systolic pressure  Arterial pressure  Peak arterial pressure during o Capillary hydrostatic pressure ventricular systole  Pressure within the capillary o Diastolic pressure beds  Minimum arterial pressure o Venous pressure during diastole  Pressure in the venous system o Pulse pressure  Circulatory pressure  Difference between systolic o Pressure difference across the systemic pressure and diastolic pressure circuit (about 100 mm Hg)  Abnormal blood pressure o Circulatory pressure must overcome o Normal=120/80 total peripheral resistance  R of entire cardiovasc. System  Hypertension  Total peripheral resistance o Abnormally high blood pressure o Vascular resistance  Greater than 140/90 o Blood viscosity  Hypotension o Turbulence o Abnormally low blood pressure  Vascular resistance  Elastic rebound o Due to friction between blood and o Arterial walls vessel walls  Stretch during systole  Rebound (recoil to original o Some ions (Na, K, Ca, Cl) diffuse through shape) during diastole channels in plasma membranes  Keep blood moving during o Large, water-soluble compounds pass diastole through fenestrated capillaries  Pressures in small arteries and arterioles o Lipids and lipid-soluble materials such as O2 o Pressure and distance and CO2 diffuse through endothelial plasma o MAP and pulse pressure decrease with membranes distance from heart o Plasma proteins cross endothelial lining in o Blood pressure decreases with friction sinusoids o Pulse pressure decreases due to elastic  Filtration rebound o Driven by hydrostatic pressure  Venous pressure and venous return o Water and small solutes forced through o Determines the amount of blood capillary wall arriving at right atrium each minute o Leaves larger solutes in bloodstream o Low effective pressure in venous system o Low venous resistance is assisted by:  Muscular compression of peripheral veins  Compression of skeletal muscles pushes blood toward heart (one-way valves) o The respiratory pump  Thoracic cavity action  Inhaling decreases thoracic pressure  Exhaling raises thoracic pressure o Capillary pressure and capillary exchange  Vital to homeostasis  Moves materials across capillary walls by  Diffusion  Filtration  Reabsorption  Diffusion o Movement of ions or molecules from high to lower concentration along the concentration gradient  Diffusion routes o Water, ions, and small molecules such as glucose  Diffuse between adjacent endothelial cells  Or through fenestrated capillaries TERM 2 PHYSIOLOGY NOTES  The respiratory epithelium Chapter 23—23.1, 23.4-.9 o For gases to exchange efficiently: 23.1—Components of the Respiratory System  Alveoli walls must be very thin  The respiratory system (<1 micrometer)  Cells produce energy  Surface area must be very great o For maintenance, growth, defense, and (about 35 times the surface area of the body) division o Through mechanisms that use oxygen  The respiratory mucosa and produce carbon dioxide o Consists of  Oxygen  An epithelial layer o Is obtained from the air by diffusion  An areolar layer called the across delicate exchange surfaces of lamina propria lungs o Lines the conducting portion of the o Is carried to cells by the cardiovascular respiratory system system, which also returns carbon  The LAMINA PROPRIA dioxide to the lungs o Underlying layer of areolar tissue that  Five functions of the respiratory system supports the respiratory epithelium 1) Provides extensive gas exchange surface o In the upper respiratory system, area between air and circulating blood trachea and bronchi 2) Moves air to and from exchange surfaces of  It contains mucous glands that lungs secrete onto epithelial surface 3) Protects respiratory surfaces from outside o In the conducting portion of lower environment respiratory system  It contains smooth muscle cells 4) Produces sounds 5) Participates in olfactory sense that encircle lumen of  Organization of the respiratory system bronchioles o The respiratory system is divided into  Structure of respiratory epithelium  Upper respiratory system— o Pseudostratified ciliated columnar above the larynx epithelium with numerous mucous  Lower respiratory system— cells below the larynx  Nasal cavity and superior  The respiratory tract portion of the pharynx o Consists of a conducting portion o Stratified squamous epithelium—  From nasal cavity to terminal inferior portions of the pharynx bronchioles o Pseudostratified ciliated columnar o Consists of a respiratory portion epithelium—superior portion of the  The respiratory bronchioles and lower respiratory system o Cuboidal epithelium with scattered alveoli o Alveoli cilia—smaller bronchioles  Are air filled pockets within the  Alveolar epithelium lungs o Is a very delicate, simple squamous  Where all gas exchange takes epithelium place o Contains scattered and specialized cells o Lines exchange surfaces of alveoli  The RESPIRATORY DEFENSE SYSTEM  Complex of connective tissue, o Consists of a series of filtration nerves, and vessels in hilum mechanisms  Anchored to the o Removes particles and pathogens mediastinum  Components of the respiratory defense 23.5—The Lungs systems  Left and right lungs are in left and right o Mucous cells and mucous glands pleural cavities produce mucous that bathes exposed  The base—inferior portion of each lung rests surfaces on superior surface of diaphragm o Cilia—sweep debris trapped in mucous  Loves of the lungs are separated by deep toward the pharynx (mucous escalator) fissures o Filtration in nasal cavity removes large  Lobes and surface of the lungs particles o The right lung has three lobes: o Alveolar macrophages engulf small superior, middle and inferior particles that reach lungs  Separated by horizontal and 23.4—The Trachea oblique fissures  The trachea o The left lung has two lobes o Also called the windpipe  Superior and inferior o Extends from the cricoid cartilage into  Separated by an oblique fissure mediastinum  Lung shape o Where it branches into right and left o Right lung is wider; is displaced pulmonary bronchi upward by liver o The submucosa o Left lung is longer, is displaced  Beneath mucosa of trachea leftward by the heart forming the  Contains mucous glands cardiac notch  The tracheal cartilages  The bronchi o 15-20 tracheal cartilages o The bronchial tree is formed by the  Strengthen and protect airway primary bronchi and their branches  Discontinuous where trachea o Extrapulmonary bronchi—the left and contacts esophagus right bronchi branches outside the o Ends of each tracheal cartilage are lungs connected by an elastic ligament and o Intrapulmonary branches—branches trachealis muscle within the lungs  The primary bronchi  A primary bronchus o Right and left primary bronchi are o Branches to form secondary bronchi separated by an internal ridge (the carina) (lobar bronchi) o The right primary bronchus is larger in o One secondary bronchus goes to each diameter than the left lobe o Descends at a steeper angle o HILUM—where pulmonary nerves, blood  Secondary bronchi vessels, lymphatics enter lung; anchored in o Branch to form tertiary bronchi meshwork of connective tissue (segmental bronchi) o The root of the lung o Each segmental bronchus supplies air to a single bronchopulmonary segment  Bronchopulmonary segments o Each pulmonary lobule is supplied by o The right lung has 10 pulmonary arteries and veins o The left lung has 8 or 9 o Each terminal bronchiole branches to  Bronchial structure form several respiratory bronchioles, o The walls of primary, secondary and where gas exchange takes place tertiary bronchi  Alveolar ducts and alveoli o Respiratory bronchioles are connected  Contain progressively less cartilage and more smooth to alveoli along aleolar ducts muscle o Alveolar ducts end at alveolar sacs; common chambers connected to many  Increased smooth muscle tension affects airway individual alveoli constriction and resistance o Each alveolus has an extensive network  Bronchitis of capillaries surrounded by elastic o Inflammation of bronchial walls causes fibers constriction and breathing difficulty  Alveolar epithelium  Bronchodilation o Consists of simple squamous o Dilation of bronchial airways epithelium o Caused by sympathetic ANS activation o Consists of thin, delicate pneumocutes o Reduces resistance type I  Bronchoconstriction o Patrolled by alveolar macrophages (dust cells) o Constricts bronchi o Caused by o Contains pneumocytes type II (septal  Parasympathetic ANS activation cells) that produce surfactant  Surfactant  Histamine release (allergic reactions) o Is an oily secretion  Asthma o Contains phospholipids and proteins o Excessive stimulation and o Coats alveolar surfaces and reduces bronchoconstriction surface tension o Stimulation severely restricts airflow  Respiratory distress syndrome  Pulmonary lobules o Difficult respiration due to alveolar o Trabeculae collapse; caused when pneumocytes  Fibrous connective tissue type II do not produce enough partitions from root of lung surfactant  Contain supportive tissues and  Respiratory membrane—the thin membrane of alveoli where gas exchange takes place lymphatic vessels  Branch repeatedly  Three layers of respiratory membrane  Divide lobes into increasingly 1) Squamous epithelial cells lining the smaller compartments alveolus  Pulmonary lobules are divided 2) Endothelial cells lining an adjacent by the smallest trabecular capillary partitions (interlobular septa) 3) Fused basement membranes between the  Pulmonary lobules alveolar and endothelial cells o Each terminal bronchiole delivers air to  Diffusion across respiratory membrane is a single pulmonary lobule rapid because the distance is short o Gases (O2 and CO2) are lipid soluble  Respiration refers to two integrated processes  Inflammation of lobules 1) External respiration—includes all processes o Also called pneumonia involved in exchanging O2 and CO2 with the  Causes fluid to leak into alveoli environment  Compromises function of 2) Internal respiration—result of cellular respiratory membrane respiration; involves the uptake of O2 and production of CO2 within individual cells  Blood supply to the lungs o Respiratory exchange surfaces receive  Three processes of external respiration blood from arteries of pulmonary 1) Pulmonary ventilation (breathing) circuit 2) Gas diffusion—across membranes and o A capillary network surrounds each capillaries alveolus as part of the respiratory 3) Transport of O2 and CO2 membrane a. Between alveolar capillaries o Blood from alveolar capillaries b. Between capillary beds in other tissue  Passes through pulmonary  Abnormal external respiration is dangerous venules and veins o Hypoxia—low tissue oxygen levels  Returns to left atrium o Anoxia—complete lack of oxygen  Also site of angiotensin- 23.7—Pulmonary Ventilation converting enzyme (ACE)  Pulmonary ventilation o Capillaries supplied by bronchial o Is the physical movement of air in and arteries provide oxygen and nutrients out of respiratory tract to tissues of conducting passageways of o Provides alveolar ventilation lung  The movement of air o Venous blood bypasses the systemic o Atmospheric pressure—the weight of circuit and flows into pulmonary veins air has several important physiological o Blood pressure in pulmonary circuit is effects low (30mm Hg)  Gas pressure and volume o Pulmonary vessels are easily blocked o Boyle’s law—defines the relationship by blood clots, fat, or air bubbles between gas pressure and volume causing pulmonary embolism where P=1/V o The pleural cavities and pleural o In a contained gas membranes  External pressures forces  Two pleural cavities are molecules closer together separated by the mediastinum  Movement of gas molecules  Each pleural cavity holds and exerts pressure on container lung and is lined with a serous  Pressure and airflow to the lungs membrane (the pleura) o Air flows from area of higher pressure  The pleura to area of lower pressure o Consists of two layers o A respiratory cycle consists of 1) Parietal pleura  An inspiration (inhalation) 2) Visceral pleura  An expiration (exhalation)  Pleural fluid lubricates space between two  Pulmonary ventilation causes volume changes layers that created changes in pressure 23.6—Introduction to Gas Exchange o Volume of thoracic cavity changes with  The respiratory cycle expansion or contraction of diaphragm o Cyclical changes in intrapleural or rib cage pressure operate the respiratory pump  Inhalation: elevation of the rib cage and which aids in venous return to heart contraction of the diaphragm increase the size  Tidal volume (Vt)—amount of air moved in of the thoracic cavity; pressure within the and out of lungs in a single respiratory cycle thoracic cavity decreases, and air flows into  Injury to the chest wall the lungs o Pneumotharax allows air into pleural  Exhalation: when the rib cage returns to its cavity original position and the diaphragm relaxes, o Atelectasis (also called a collapsed the volume of the thoracic cavity decreases; lung) is a result of pneumothorax pressure rises and air moves out of the lungs  The respiratory muscles  Compliance o Most important are the diaphragm, o An indicator of expandability external intercostal muscles of the ribs, o Low compliance requires greater force accessory respiratory muscles o High compliance requires less force (activated when respiration increases o Factors the affect compliance significantly)  Connective tissue structure of  The mechanics of breathing the lungs o Inhalation-always active  Level of surfactant production o Exhalation-active or passive  Mobility of the thoracic cage  Muscles used in inhalation  Pressure changes during inhalation and o Diaphragm exhalation  Contraction draws air into lungs o Can be measured i
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