Lecture 16 BIO 311D 1st EditionOutline of Last Lecture I. Fluid Return by the Lymphatic SystemII. Blood ComponentsIII. PlasmaIV. ErythrocytesV. LeukocytesVI. Stem CellsOutline of Current Lecture I. Blood ComponentsII. Partial Pressure Gradients in Gas ExchangeIII. Respiratory SurfacesIV. How other animals breatheV. LungsVI. Pathway of the Respiratory SystemVII. Control of Breathing in HumansCurrent LectureBlood ComponentsComponent Structure FunctionPlasma Water, proteins, ions,electrolytesSolvent for carrying othersubstances, osmoticbalanceLeukocytes (white bloodcells)Round large cells, no nuclei,no hemoglobinDefense and immunityPlatelets Fragments Blood clotErythrocytes (red bloodcells)No nuclei Carry oxygenPartial Pressure Gradients in Gas Exchange• A gas diffuses from a region of higher partial pressure to a region of lower partial pressure• Partial pressure is the pressure exerted by a particular gas in a mixture of gases• Gases diffuse down pressure gradients in the lungs and other organs as a result of differences in partial pressure• Animals can use air or water as a source of O2, or respiratory medium• In a given volume, there is less O2 available in water than in air• Obtaining O2 from water requires greater efficiency than air breathingRespiratory Surfaces• Animals require large, moist respiratory surfaces for exchange of gases between their cells and the respiratory medium, either air or water• Gas exchange across respiratory surfaces takes place by diffusion• Respiratory surfaces vary by animal and can include the outer surface, skin, gills, tracheae, and lungs Concurrent flow is not as efficient in exchange as countercurrent flow because the latter provides:A. More diffusion at the beginning of capillary flow than midway through the capillaryB. More diffusion at the end of capillary flow than midway through the capillaryC. Adequate diffusion of gases across weaker concentration gradientsD. Thinner capillary walls to promote diffusionE. Greater surface area for diffusionGills in Aquatic Animals• Gills are outfoldings of the body that create a large surface area for gas exchange• Ventilation moves the respiratory medium over the respiratory surface• Aquatic animals move through water or move water over their gills for ventilation• Fish gills use a countercurrent exchange system, where blood flows in the opposite direction to water passing over the gills; blood is always less saturated with O2 than the water it meets• There must be movement of water in order for them to BreatheTracheal Systems in Insects• The tracheal system of insects consists of tiny branching tubes that penetrate the body• The tracheal tubes supply O2 directly to body cells• The respiratory and circulatory systems are separate• Larger insects must ventilate their tracheal system to meet O2 demandsLungs• Lungs are an infolding of the body surface• The circulatory system (open or closed) transports gases between the lungs and the rest of the body• The size and complexity of lungs correlate with an animal’s metabolic rate• A system of branching ducts conveys air to the lungs• Air inhaled through the nostrils is warmed, humidified, and sampled for odors• The pharynx directs air to the lungs and food to the stomach• Swallowing tips the epiglottis over the glottis in the pharynx to prevent food from entering the tracheaPathway of Respiratory System:• Air passes through the pharynx, larynx, trachea, bronchi, and bronchioles to the alveoli, where gas exchange occurs• Exhaled air passes over the vocal cords in the larynx to create sounds• Cilia and mucus line the epithelium of the air ducts and move particles up to the pharynx• This “mucus escalator” cleans the respiratory system and allows particles to be swallowed into the esophagus• Gas exchange takes place in alveoli, air sacs at the tips of bronchioles• Oxygen diffuses through the moist film of the epithelium and into capillaries• Carbon dioxide diffuses from the capillaries across the epithelium and into the air space• Cilia helps collect unwanted particles like dust, etc from entering the lungs• Alveoli lack cilia and are susceptible to contamination• Secretions called surfactants coat the surface of the alveoli• Preterm babies lack surfactant and are vulnerable to respiratory distress syndrome; treatment is provided by artificial surfactants• The process that ventilates the lungs is breathing, the alternate inhalation and exhalation of air• Doctors inject artificial surfactants into infants to help them stay aliveBreathing ventilates the lungs• The process that ventilates the lungs is breathing, the alternate inhalation and exhalation of airHow an Amphibian Breathes• An amphibian such as a frog ventilates its lungs by positive pressure breathing, which forces air down the tracheaHow a Bird Breathes• Birds have eight or nine air sacs that function as bellows that keep air flowing through the lungs• Air passes through the lungs in one direction only• Every exhalation completely renews the air in the lungsHow a Mammal Breathes• Mammals ventilate their lungs by negative pressure breathing, which pulls air into the lungs• Lung volume increases as the rib muscles and diaphragm contract• The tidal volume is the volume of air inhaled with each breath• The maximum tidal volume is the vital capacity• After exhalation, a residual volume of air remains in the lungsControl of Breathing in Humans• In humans, the main breathing control centers are in two regions of the brain, the medulla oblongata and the pons• The medulla regulates the rate and depth of breathing in response to pH changes in the cerebrospinal fluid• The medulla adjusts breathing rate and depth to match metabolic demands• The pons regulates the tempo• Sensors in the aorta and carotid arteries monitor O2 and CO2 concentrations in the blood• These sensors exert secondary control over breathingAdaptations for gas exchange include pigments that bind and transport gases• The metabolic demands of many organisms require that the blood transport large quantities of O2 and CO2Coordination of Circulation and Gas Exchange• Blood arriving in the lungs has a low partial pressure of O2 and a high partial pressure of CO2 relative to air in the alveoli• In the alveoli, O2 diffuses into the blood and CO2 diffuses into the air• In tissue capillaries, partial pressure gradients favor