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What are the 3 layers of blood vessels? Tunica intima, tunica media and tunica externa Innermost tunica intima Simple squamous epithelium to allow a low friction surface Middle tunica media Smooth muscle and elastic tissue to control the diameter Outermost tunica externa Nerve and elastic fibers Vasa vasorum Tiny blood vessels that supply blood for larger ones Vasoconstriction Smooth muscle constricts to decrease the diameter Vasodilation Smooth muscle relaxes to increase the diameter Elastic arteries Thick walled and near the heart. They have the largest lumens and are considered to be the conducting vessels (send blood from heart to medium arteries) Atherosclerosis Hardening of the arteries. Blood flow gushes/trickles as the heart beats, causing the vessel walls to weaken or eventually balloon out (aneurysm), or burst Muscular arteries Considered to be the distributing vessels (deliver blood to organs). Diameter ranges greatly Arterioles The resistance vessels: diameter determines blood flow to capillaries as a mechanism of homeostasis that responds to neural, hormonal, and chemical influences Capillaries Microscopic vessels with thin walls. They allow the exchange of gasses, nutrients and hormones between the blood and the interstitial fluid (then to the tissues) Continuous capillaries Least permeable and most common
Fenestrated capillaries Fenestrations increase permeability Sinusoid capillaries Most permeable to allow large cells to pass. Incomplete basement membrane and large intercellular cleft Capillary beds Connections between terminal arterioles and postcapillary venules. True capillaries are the exchange vessels and the vascular shunt (thoroughfare channel) bypasses tissue cells Precapillary sphincter A smooth muscle cuff that regulates blood flow (like a valve) Veins Return blood to the heart from the venules. Have thin walls because of the low pressure, and large lumens so that blood can be returned to the heart at the same rate that it is pumped out Venous valves Prevent blood from flowing backwards, made from folds of tunica intima and are mostly in the lower limbs Venous sinuses Specialized veins with thick endothelium walls (example is the coronary sinus) Varicose veins Homeostatic imbalance - dilated veins caused by incompetent valves. The blood pools in lower limbs and causes valves to weaken Stages of atherosclerosis Endothelium is injured, lipids accumulate and oxidize in the tunica intima, smooth muscle cells proliferate and then the plaque enlarges and becomes unstable Consequences of atherosclerosis Increases the likelihood of clot formation, may cause aneurysm, angina, heart attack, stroke Treatment of atherosclerosis Coronary artery bypass and graft surgery, angioplasty, stenting or thrombolytic agents Blood flow The volume of blood moving though a vessel/organ/entire circulatory system within a given period (mL/min) Blood pressure force exerted on a vessel wall by contained blood (mmHg). A pressure gradient results from differences in BP between two points Resistance Opposition to blood flow due to friction encountered in the vessels Blood viscosity Resistance to flow of fluids (increased viscosity=molecules cannot slide past eachother as well) Relationship between blood flow and blood pressure
Antidiuretic hormone Causes vasoconstriction when there is blood loss Renal control of blood pressure Can regulate by controlling blood volume Hypertension Systolic over 120, diastolic over 80. Strains heart, damages arteries Primary hypertension Most common with unknown cause and therefore no cure Secondary hypertension Known cause with cure Hypotension Low blood pressure but can be normal Orthostatic hypotension Blood pressure drop after standing that causes dizziness and falls because this is the body's mechanism of getting more blood to the brain Addision's disease An adrenal deficiency that can cause hypotension Circulatory shock Blood vessels are not adequately filled and the blood cannot circulate, so tissue needs are not met. Cell death/organ damage can cause death Vascular shock Blood volume is normal but circulation is not, causing dilated blood vessels (equivalent to blood loss because it does not reach tissues Cardiogenic shock Heart fails as a pump and cannot provide adequate circulation Extrinsic controls of blood vessels body wide, sympathetic nervous system Intrinsic control of blood vessels Local, ensures that blood gets to the tissues that need it. Two types: metabolic and myogenic Metabolic controlled autoregulation Causes vasodilation or vasoconstriction to keep the system at equilibrium Myogenic controlled autoregulation Protects the organs against blood pressure changes by changing the degree of stretch of the vessel wall Angiogenesis New blood vessels are generated as needed Blood flow to skeletal muscles Flow increases in direct proportion to increased metabolic activity
Blood flow to the brain Needs a huge amount of blood relative to its size because neurons cannot store nutrients Effect of too much CO2 on the brain Abolishes autoregulation and decreases brain activity Blood flow to the skin A mechanism of temperature control. Too hot: vasodilation (blood flows to skin capillary beds so heat can be released) Too cold: vasoconstriction (warm blood is kept in to reduce heat loss) Blood flow to the lungs Arteries are like veins (carry deoxygenated blood), low pressure and opposite autoregulatory mechanism (decreased blood pressure causes vasoconstriction to keep blood away from the damaged area) Capillary hydrostatic pressure The pressure that pushes fluids out into the interstitial space Edema Increased interstitial fluid - the outward pressure is greater Osmotic interstitial pressure Sucks fluid from the blood, causing swelling Capillary osmotic pressure Stops fluid from returning to the blood, usually because of decreased plasma proteins Fluid in the lymphatic system Protein containing fluid that is leaked from blood vessel capillaries (20L every day, 17L come back, so net 3L fluid loss). The fluid is reclaimed from interstitial fluid and returned to the blood stream Location of lymphatic capillaries Everywhere but bones, teeth, or CNS Lymphatic capillaries Extremely permeable with wall junctions that function as minivalves Material let into the lymphatic capillaries Can be good: lacteals (absorbed fat in the form of chyle - energy for skeletal muscle) or bad: pathogens and cancer cells The lymphatic vessels Same tunics as veins with thinner walls. Largest ones are the right lymphatic duct and thoracic duct Lymph transport Low pressure system (no pump), but flows because of the action of skeletal muscles and pressure changes during breathing Lymphangitis Vasa vasorum (lymphatic system's blood supply) gets congested with blood Lymphedema
Yes, the liver and bone marrow take over its functions in the case of splenectomy What is the mucosa-associated lymphoid tissue (MALT)? A set of lymphoid tissues distributed throughout the body and located in mucous membranes Function of tonsils Line the entrance to the throat as to stop pathogens from entering Function of the respiratory system Supplies the tissues with oxygen and disposes of carbon dioxide Pulmonary ventilation Movement of air into and out of the lungs External respiration Diffusion of oxygen into the tissues, and carbon dioxide into the lungs Components of the upper respiratory system Nose, pharynx, and larynx Functions of the nasal cavity Airway, produces mucous, moistens/warms incoming air and houses the olfactory receptors Rhinitis Nasal mucosa inflammation. There is too much mucous in the nasal cavities with can spread to the throat and chest Infected/swollen adenoids The air passages in the nasopharynx are blocked, causing the person to have to breathe through their mouth (air is not properly filtered) Components of the lower respiratory system Larynx, trachea, bronchi and lungs Functions of the larynx Air passageway, epiglottis, and voice box What is the epiglottis? Elastic cartilage that is covered with taste buds to sense if the wrong substance is about to enter the lungs, if so, it will prevent this. How does the voice box work? There are vocal folds (ligaments lacking blood vessels) that vibrate and produce sound as air rushes up the larynx - voice occurs as glottis opens and closes (intermittent air release) Voice during puberty The male larynx enlarges, making the vocal folds longer and thicker. The vibration frequency now decreases, and the voice is deeper Valsalva's maneuver The vocal folds act as a sphincter (stopping air flow out) to increase abdominal pressure Layngitis
Vocal fold inflammation, impairing vibration and causing hoarseness The 4 layers of the trachea wall Mucosa, sub-mucosa, hyaline and adventitia Heimlich maneuver Propels a substance out of the blocked trachea by forcing air from the lungs Walls of the alveoli Squamous epithelial cells called type I alveolar cells Type II alveolar cells Scattered among type I, secrete surfactant fluid and antimicrobial proteins Features of alveoli Have pores to equalize air pressure and macrophages to destroy germs Which lobe has more bronchopulmonary segments Right (has 10) compared to 8-10 left Why is most pulmonary disease surgically removable? It is usually confined to 1-2 segments and can be taken out without impairing function to the point of lung death Which thoracic cavity do the lungs not occupy? Mediastinum Innervation of the lungs (what type) Both sympathetic and parasympathetic Parasympathetic innervation in the respiratory system Constricts the bronchioles but do not innervate the blood vessels Sympathetic innervation in the respiratory system Dilates the bronchioles and constricts the blood vessels Pleurae A double layered covering of the lung (similar to pericardial sac around the heart) Function of the pleurae Produces pleural fluid which fills a small pleural cavity to allow the lungs to glide over the thorax wall between breathing Pleurisy Inflammation of the pleura (pneumonia). It becomes rough and causes a stabbing pain with each breath Intrapulmonary/intra-alveolar pressure (Ppul) The pressure changes with breathing, but equalizes to 0 Intrapleural pressure (Pip) The pressure inside the pleural cavity. It changes with each breath, but is always 3mm less than Ppul Transpulmonary pressure The difference between intrapulmonary and intrapleural pressure
Hyperinflated lungs Restrictive lung disease decreased total lung capacity (limited lung expansion Minute ventilation Measures respiratory efficiency using a rough approximation of the total amount of air flowing into and out of the lungs in one minute Alveolar ventilation rate A better approximation of respiratory efficiency frequency x (tidal volume - dead space) Effect of deep breathing on the alveolar ventilation rate Increases - the dead space does not change, so increased tidal volume = increased AVR Henry's law The greater the partial pressure of a gas, the faster it will mix into a solution Solubility of CO2 relative to oxygen 20x more Effect of temperature on solubility Solubility decreases with higher temperature because the gas is being driven out of the liquid Gas in alveoli compared to the atmosphere Alveoli contain more carbon dioxide and water vapour, less oxygen Determinants of external respiration (3) Partial pressure gradient and gas solubility Surface area of respiratory membrane Ventilation-perfusion coupling Partial pressure gradients and gas solubility Pressure differences of oxygen and CO2 drive diffusion across the membrane There is a greater oxygen pressure gradient than that of CO2, yet equal amounts are still exchanged. How does this happen? CO2 is more soluble and can diffuse at a smaller gradient than oxygen Thickness and surface area of a respiratory membrane The greater the surface area, the more gas can diffuse across it Pulmonary edema Lungs are water clogged and the thickness of the respiratory membrane increases. Blood can't get into the heart and is backed up in the lungs, increasing transit time and causing oxygen deficiency Emphysema Break down of the alveolar walls (more space, less surface area) Pressure gradients in the tissues Reversed - because oxygen is needed for metabolic activities (goes into tissues)
Oxygen affinity and its result on respiration Each bond of oxygen to hemoglobin facilitates the next, which is why oxygen comes on in the tissues and goes off in the lungs Hypoxia Oxygen deficiency Anemia Too few/abnormal RBCs Ischemia Impaired/blocked circulation Histotoxicity Cells are unable to use oxygen Hypoxemia Decreased arteriolar pressure Methods of carbon dioxide transport Dissolved in plasma, bound to deoxyhemoglobin, or by bicarbonate ions in the plasma catalyst in the bicarbonate equation carbonic anhydrase Bohr and haldane effects of CO2 elimination The lower the oxygen concentration, the less oxygen on the hemoglobin, so the more CO2 it can carry Pontine respiratory centre Interacts with the medullary respiratory centres to fine tune respiration Ventral respiratory group Tells the muscles what to do to achieve inspiration or expiration Dorsal respiratory group Communicates with the ventral respiratory group and moderates its rhythm Phrenic nerve Innervates the diaphragm Eupnea Normal respiratory rate/rhythm Action of the ventral respiratory group during hypoxia Generates gasping to restore oxygen to the brain Detection of CO central and peripheral chemoreceptors Hypercapnia High carbon dioxide levels generate H+, which excites chemoreceptors to increase respiration rate so that more CO2 is expelled Hyperventilation
